Brake disc manufacturing device, arranged to produce a brake disc, use thereof and brake disc obtained

Abstract

Brake disc manufacturing device, designed to produce a brake disc starting from a substrate (12) of a brake disc, wherein the substrate (12) is made of a graphite-containing metallic material, in particular of grey cast iron, and the substrate (12) defines a surface (13, 13'), comprising: a laser deposition device arranged to form a metal-based deposition layer on the surface (13, 13') of the substrate (12) by applying laser deposition, with a powder feed including a powder nozzle and with a laser source arranged to direct a laser beam onto the surface such that powder is applied to the surface (13, 13') while a laser beam is irradiated onto the surface (13, 13'), wherein the powder nozzle is coupled to the laser head in order to move the supplied powder and the laser beam together over the surface to be coated when the laser head moves, wherein the laser application device is configured such that the diameter of a laser spot applied to the surface by the laser beam is larger than the diameter of a powder spot applied to the surface from the powder nozzle, and such that the axis of the laser spot applied to the surface is offset with respect to the axis of the powder spot applied to the surface.

Description

[0001] This application claims priority from European patent application EP24382549.4, filed on May 23, 2024. The full disclosure of European patent application EP24382549.4 is hereby incorporated by reference. TECHNICAL FIELD

[0002] The present disclosure relates to the field of brake discs for friction brakes of vehicles, in particular motor vehicles, such as land vehicles. More specifically, the present disclosure relates to a laser deposition device for the production of such brake discs. The disclosure is particularly advantageous in production when an energy beam, such as a laser energy beam, is used. STATE OF THE ART

[0003] Friction brakes consist of a rotating element, such as a brake drum or a brake disc. A brake disc typically consists of two outer friction surfaces facing each other. These surfaces are usually circular, ring-shaped. During braking, these surfaces are pressed against a brake pad, thus braking the brake disc.

[0004] Brake discs usually consist of a core part made of a metallic material (base material), such as cast iron, a relatively inexpensive material that is suitable for the production of brake discs due to several properties, such as high melting point, good heat storage capacity, good conductivity and good machinability.

[0005] It is known to apply a wear layer to the base material of the brake disc that is more wear-resistant and corrosion-resistant than the base material. Such a coating usually also aims to increase the friction coefficient of the brake disc. In addition to these reasons related to brake disc efficiency, there is currently a market requirement to produce brake discs that generate minimal particulate emissions (the Euro 7 emissions regulations for motor vehicles). For all these reasons, the application of the wear layer must be optimized to meet both the efficiency of the brake disc in terms of wear resistance and friction coefficient, as well as the low emission requirements.

[0006] The coating can be a powder coating, meaning that the coating material is in powder form before being applied to the friction surfaces. The powder is melted by heat during or shortly before the coating is applied, bonding with the base material of the brake disc and forming a surface layer. The powder can be applied to the friction surfaces, for example, by laser deposition or laser cladding. Examples of common materials used as coatings include metals in combination with carbides. The applied wear layer must exhibit good adhesion to the base material of the brake disc.

[0007] However, it has been found that the adhesion between the wear layer and the base material of the brake disc, especially when the base material is cast iron, is usually poor due to the presence of graphite in the cast iron, particularly in the form of lamellar graphite and / or spherical or quasi-spherical graphite flakes. Due to the high power of the laser beam used in a laser cladding process for coating a cast iron part with a metallic material in powder form, for example, the graphite flakes contained in the cast iron, particularly on the surface, are vaporized, causing cracks, voids, and bubbles in the applied coating, creating defects that reduce the adhesion between the wear layer and the surface of the base material. Consequently, these defects cause various imperfections in the coating, such as:Voids or discontinuities in the coating and irregular (i.e., non-flat) surfaces. Therefore, to improve the reliability of the wear-resistant coating, the amount of flake graphite in the surface of the brake disc's base material must be reduced.

[0008] Various techniques have been proposed to reduce the amount of graphite on the surface of the base material of a brake disc. For example, before applying such a coating to the base material, the base material can be pretreated. US2013 / 0153345A1 mentions the detachment and removal of the graphite component from the friction surface by subjecting the braking element to ultrasonic or laser beam treatment. US2014 / 0262642A1 mentions a method for producing a brake disc in which the contact surface of the base material of the brake disc is pretreated before applying a wear layer. This pretreatment can include modifying the surface topography by laser irradiation, for example, to remove organic deposits. DE102010048075A1 and DE102011056307A1 mention various methods for forming a graphite-free friction layer, including laser treatment.

[0009] However, none of the documents says anything about how such laser treatments should actually be carried out or how the corresponding devices should be set up or how they should be used in order to achieve the desired result.

[0010] Therefore, there is a need to improve the manufacturing of brake discs so that a brake disc with improved adhesion between an overlay layer and the base material of the brake disc can be achieved, thereby increasing the reliability of the wear layer. DESCRIPTION OF THE INVENTION

[0011] The brake disc manufacturing device for producing a brake disc, the use thereof and the brake disc manufactured by means of this or using the brake disc manufacturing device with laser deposition device aim to remedy the deficiencies of the prior art in the production of brake discs and the available brake discs.

[0012] The objective of the present disclosure is to provide a brake disc with increased efficiency, in particular having one or more friction surfaces with increased wear and corrosion resistance and an increased coefficient of friction. The increased efficiency must be achieved without significantly compromising the homogeneity of the disc substrate below its uppermost (surface) part.

[0013] The brake disc of this disclosure is made from a substrate, base material, or base body (hereinafter referred to as the substrate) made of a graphite-containing metallic material. The substrate can be cast or forged, for example, from suitable materials such as gray cast iron, cast steel, wrought steel, ductile iron, etc. The substrate is preferably made of gray cast iron. The metallic material from which the substrate is made contains graphite, often in the form of flakes. This is typical, but not limiting, for gray cast iron. The substrate is a rotatable element having two substantially flat surfaces that oppose each other. These surfaces are typically circular, annular surfaces.

[0014] At least one coating is applied to a surface of the substrate that is intended to be the friction surface of the finished brake disc after the latter has been completely manufactured. The cladding can then be repeated with the opposite surface of the substrate. The coating is intended to increase the performance of the brake disc, e.g. its wear and corrosion resistance and its coefficient of friction. The coating is applied using a laser cladding device to provide high performance and high material pick-up. Powder is applied to the surface to be coated, while a laser beam is directed onto the surface to be coated by a laser head that is moved along the surface to be treated. The radiation of the laser beam focused onto the surface creates a molten pool on the surface when the powder, e.g.is fed through a nozzle, causing the powder to melt. As the laser beam moves along the surface of the substrate, moving away from the deposited material, the deposited material cools and solidifies on the surface of the substrate. By repeatedly depositing or cladding the entire surface to be treated, the substrate is essentially covered with a coating. The coated surface can be the friction surface of a brake disc.

[0015] A first aspect of the disclosure relates to a brake disc manufacturing device configured to produce a brake disc from a substrate (12) of a brake disc, wherein the substrate (12) is made of a graphite-containing metallic material, in particular of grey cast iron, and the substrate (12) defines a surface (13, 13') comprising a laser deposition device configured to form a metal-based coating layer on the surface (13, 13') of the substrate (12) by applying laser deposition, with a powder feed containing a powder nozzle and with a laser source configured to direct a laser beam onto the surface such that powder is applied to the surface (13, 13') while a laser beam is irradiated onto the surface (13, 13'), wherein the powder nozzle is coupled to the laser head to move the supplied powder and the laser beam together over the surface to be coated when the laser head moves, wherein the laser application device is configured such that the diameter of a laser spot applied to the surface by the laser beam is larger than the diameter of a powder spot applied to the surface from the powder nozzle, and such that the axis of the laser spot applied to the surface is offset with respect to the axis of the powder spot applied to the surface.

[0016] Due to the offset between the axes (axis of the laser beam and thus of the corresponding laser spot on the one hand and axis of the powder nozzle and thus of the corresponding powder spot or powder spot on the other hand), a part of the laser radiation applied to the surface by the laser beam reaches an area of ​​the surface of the substrate before the powder delivered by the powder nozzle is applied to this area of ​​the surface, so that this part of the laser radiation interacts with the said area of ​​the surface before the powder is applied to this area, whereby the surface is thermally prepared to receive the powder and the surface is cleaned by the laser.In addition, another laser beam reaches the area of ​​the surface where the powder is applied at the same time as the powder is deposited on the thermally prepared area, enabling the melting of the deposited powder and the formation of a coating that bonds well with the thermally prepared surface of the substrate. By laser irradiating the surface zone before powder application, it is minimally altered by the evaporation of the graphite present in the uppermost layer of the substrate, thereby improving the contact surface on which the material (deposited powder) is received. The laser radiation also causes the evaporation of additional contaminants such as lubricant residues and rust, which may have arisen from a previous machining process, for example, thus preventing any deterioration of the deposited metal-based layer.

[0017] After repeating the cladding process over the entire surface of the substrate during a specific cycle time, a metal-based coating or plating essentially covers the substrate. The covered surface can be a friction surface of a brake disc.

[0018] In the context of the present disclosure, a laser spot (or a region thereof) is understood to mean a projection of an irradiated laser beam onto the surface of the substrate, covering a region thereof. A powder spot is understood to mean the powder that is applied or projected, for example, from a powder nozzle onto the surface of the substrate and covers a region thereof.

[0019] The substrate is preferably made of grey cast iron.

[0020] The graphite contained in the substrate is usually lamellar graphite, which occurs, among other things, in grey cast iron.

[0021] The at least one coating layer is preferably made of metal. In the context of the present disclosure, the at least one coating layer is a metal-based coating layer. In some embodiments, the at least one coating layer is a single layer of metal. Preferably, the metal-based coating layer is made of steel, e.g., stainless steel. In some embodiments, the at least one coating layer is a single layer of a mixture of a metal and a carbide. In some embodiments, the at least one coating layer is a multi-layer comprising two coating layers. In some embodiments, the at least one coating layer is a multi-layer comprising at least one coating layer of metal and at least one coating layer of a mixture of a metal and a carbide.Alternatively, the at least one coating layer is a multilayer comprising at least two coating layers made of a mixture of a metal and a carbide. The at least one metal coating layer of the multilayer system is preferably made of steel, for example stainless steel. The metal in the at least one coating layer made of a mixture of a metal and a carbide is preferably steel, for example stainless steel. In preferred embodiments, the carbide is tungsten carbide or titanium carbide. In some embodiments, the at least one metal coating layer consists only of pure metal.

[0022] In some embodiments, the at least one overlay layer of a mixture of a metal and a carbide comprises about 10 to about 30 wt.% of a carbide and about 70 to 90 wt.% of a metal. In some embodiments, the at least one overlay layer of a mixture of a metal and a carbide comprises about 20 to 40 vol.% of a carbide and about 60 to 80 vol.% of a metal.

[0023] In some embodiments, the at least one coating layer is a single layer with a thickness of about 50 to about 250 µm. For example, the single layer may have a thickness of about 100 µm with a tolerance of ±40 µm or a thickness of about 200 µm with a tolerance of ±40 µm. In some embodiments, the at least one coating layer is a multilayer consisting of two layers, wherein the first layer may have a thickness between 50 and 250 µm and the second layer may have a thickness between 150 and 350 µm. For example, the first layer may have a thickness of about 100 µm with a tolerance of ±40 µm or a thickness of about 200 µm with a tolerance of ±40 µm. The second layer may, for example, B. have a thickness of about 200 µm with a tolerance of ±20 µm or a thickness of about 300 µm with a tolerance of ±20 µm.The thickness of one or more layers was determined by taking and evaluating scanning electron microscopy (SEM) and / or light microscopy (OM) images.

[0024] The powder used to produce the at least one coating can be a metal-based powder, e.g., a steel-based powder, or a mixture of metal-based powder and carbide-based powder. Non-limiting examples of carbide-based powders are tungsten carbide powder and titanium carbide powder. The metal-based powder is conventional and falls outside the scope of the present invention. The powder can, for example, be a steel particle composite. Or the powder can be a carbide particle composite.When a coating comprising a mixture of a metal and a carbide is to be achieved, metal powder particles and carbide powder particles are combined and the mixture of powder particles is applied to the surface to be coated such that when a laser beam is directed onto the surface to be coated, the laser beam focused onto the surface creates a molten pool of material on the surface. The size of the powder particles can vary in the range from about 4 to about 180 µm (microns, 10-6 m) in diameter (assuming spherical particles, although they can also assume other shapes, including irregular particles, the former referring to the largest dimension of the particle). Preferably, the size of the powder particles can vary between about 10 and about 63 µm, more preferably between about 20 and about 53 µm.Powder particles are typically marketed under specific fractions of diameter or major dimension, e.g., between 5-45 µm, or between 4-45 µm, or between 15-45 µm, or between 20-53 µm, or between 20-63 µm, or between 45-106 µm, or between 45-150 µm, or between 53-125 µm, or between 53-180 µm. The shape and average size distributions of the particles were determined by capturing and evaluating scanning electron microscope (SEM) and / or optical microscope (OM) images. In embodiments where the particles are substantially spherical, the average size refers to the average diameter of the particles.As a non-limiting example, the metal-based powder used is a commercially available powder such as AISI 316L (stainless steel; spherical powder particles with a diameter in the range of 20-53 µm, supplied by Höganäs); or such as AISI 430L (stainless steel; spherical or irregular powder particles with a major dimension in the range of 20-53 µm, supplied by Höganäs); or such as WC (tungsten carbide; spherical powder particles with a diameter in the range of 20-53 µm, supplied by C&M); or such as TiC (titanium carbide; irregular powder particles with a major dimension in the range of 15-45 µm, supplied by Höganäs or in the range of 45-150 µm, supplied by Ampere or in the range of 20-63 µm, supplied by Heeger). In some embodiments, the titanium carbide may contain ferrochrome.

[0025] In some embodiments, the deposition of an overlay layer involves depositing a single layer, preferably a mixture of metal and a carbide, such as tungsten carbide or titanium carbide. This layer is formed from a powder containing a mixture of metal powder and carbide powder.

[0026] The laser radiation used in laser cladding is emitted from a laser processing head, which, for example, carries a nozzle. The emitted laser radiation passes through the nozzle coaxially, along the longitudinal axis of the nozzle. In order for the laser beam to shine onto the surface of the substrate, the laser beam preferably passes through any pattern on the surface of the substrate that is to be exposed to the laser radiation. The laser system can be a pulsed laser or a continuous wave laser, for example a scanned continuous wave laser. It is preferably a continuous wave laser. The selected pattern preferably follows a linear trajectory along a radial axis of the surface of the substrate. Preferably, the substrate rotates about its axis of rotation at a specific angular velocity at the same time.When the laser beam moves along a linear path, the linear advance of the laser beam along the linear path (i.e., from a central point on the surface corresponding, for example, to the inner radius of the substrate forming the brake disc and thus lying on the substrate's rotation axis, to a point on the substrate surface corresponding to its outer radius, or vice versa) creates a spiral path. In other words, the brake disc substrate rotates while the laser processing head moves linearly across the substrate surface (following a specific pattern), with this linear movement following a radial path on the substrate surface.

[0027] For example, in some embodiments, the substrate of the brake disc rotates while the laser processing head, from which the laser beam emanates, moves linearly on the surface of the substrate, with the linear movement following a radial path on the surface of the substrate. For example, the substrate rotates at a variable angular velocity while the laser beam moves linearly in the radial direction. The angular velocity of the substrate is variable to compensate for the radial advance of the laser beam, so that the substrate rotates at a constant linear velocity. For example, the substrate can rotate at a linear velocity in the range between 80 and 240 meters / minute (m / min), preferably between 120 and 200 m / min. The laser beam preferably moves linearly at a velocity of less than 500 mm / min. The speed of the laser beam depends on the dimensions of the brake disc.The speed of the laser beam moving along the radius of the substrate can be adjusted to regulate the distance between adjacent metal plates.

[0028] The powder is fed from a powder nozzle coupled to the laser head from which the laser beam is emitted, so that the laser beam and the powder nozzle move together radially along the surface to be coated as the laser head moves and the powder is fed simultaneously. A laser system is used that creates a circular laser spot. Thus, the fed powder and the laser beam move together along the surface to be coated as the laser head moves. Preferably, the distance between the surface of the substrate and the proximal end of the nozzle from which the powder is to be applied to the surface, and the distance between the surface of the substrate and the focal point of the laser beam are selected to achieve a predetermined size (i.e., width or diameter) of the coating. This predetermined size is usually smaller than the size (i.e.,the diameter) of the powder nozzle from which the powder is fed.

[0029] Unlike conventional laser beam cladding, in which the axis of the incident laser beam (and thus the axis of the corresponding laser spot projected onto the surface to be treated) is aligned with the axis of the nozzle or container from which the powder is dispensed (and thus the axis of the dispensed powder spot), the inventors have surprisingly found that cladding is optimized when a part of the laser spot reaches an area on the surface to be treated a certain time before the powder is deposited on that area of ​​the surface in the form of metal plating.By laser irradiating the area or zone of the surface before applying the powder to that area or zone, the graphite present in the uppermost layer of the substrate is evaporated, slightly altering the surface to which the powder is shortly applied, thus improving the contact area where the material (the applied powder) is received. This laser radiation also causes the evaporation of any additional impurities that may be present on the surface, thus preventing any deterioration of the deposited metal-based layer. It was therefore found that it is desirable for a portion of the laser spot to interact with the substrate without any further material being deposited during a certain interaction time.To achieve this interaction time, a certain misalignment between the axis of the laser beam (and therefore of the laser spot) and the axis of the powder spot is required. Therefore, the axis of the laser beam should be offset with respect to the axis of the nozzle that dispenses the powder. By decentering or offsetting the axis of the powder spot with respect to the axis of the laser beam, part of the laser spot reaches an area on the surface to be treated during the linear movement of the laser beam as the brake disc substrate rotates, before the powder is actually deposited on the surface in the form of metal plating. The decentering is achieved in such a way that the laser spot interacts with the substrate without any material being deposited during the aforementioned interaction time.The interaction time depends on the axis offset, the size of the laser spot and the powder diameter, as well as the process speed.

[0030] The axis of the powder spot is preferably offset from the axis of the laser spot within a range between 0 and 20% of the laser spot diameter (excluding 0), preferably between 2.5 and 20% thereof, more preferably between 2.5 and 15% thereof, and even more preferably between 5 and 12.5% ​​thereof. For example, if the difference between the diameter of the laser spot and the diameter of the powder spot is between 0.3 and 0.5 mm, the interaction time can be selected between 0.05 and 0.7 ms, depending on the disk size and speed.

[0031] By laser irradiating the area to which the powder is immediately applied, the surface is thermally influenced as it receives the application or coating material. In other words, by decentering the axis or offset of the laser beam relative to the axis of the powder spot, the substrate is thermally influenced, which leads to an improvement in the contact area of ​​the substrate, which in turn enables a better bond between the melt pool (powder molten on the surface) and the substrate surface.It has been found that conventional laser cladding processes, in which the laser beam axis is aligned with the powder spot axis, allowing simultaneous delivery of laser radiation and powder, result in undesirable displacement of the deposited material on the substrate surface due to stresses imposed on the material during deposition onto the substrate. This undesirable material displacement is particularly pronounced when a subsequent layer of material (in the form of a string or similar) is applied adjacent to a previously deposited layer. The proximity of a newly deposited layer, which sometimes slightly overlaps an adjacent layer, and the laser radiation applied during deposition of the subsequent layer remove the previously deposited layer, altering its position or displacing it from its location.This may be due to the fact that no actual dilution of the substrate with the deposited material occurs (such dilution is undesirable, as it could damage the substrate structure). This hinders the integration and adhesion of the material to the substrate. In contrast, with the offsetting process in the present disclosure, the magmatic powder particles, which reach the surface with some delay compared to the initial application of the laser radiation, can more easily fuse with the contact surface of the substrate, increasing their adhesion to the substrate. By offsetting the two axes, a portion of the laser radiation is applied slightly earlier than the powder material, and the high concentration of laser energy is initially applied only to the surface of the substrate, which is thereby somewhat thermally influenced, contributing to the subsequent integration of the cast material and the substrate.The subsequent application of the powder to the thermally prepared surface zone occurs simultaneously with the application of the laser radiation. Furthermore, the thermal preparation of the substrate surface by laser radiation prior to powder application causes some evaporation of any flake graphite present in the most superficial layer of the substrate before the actual application and melting of the powder. This results in the deposition of the deposition material on a surface that has some holes created by the evaporation of graphite and that has already been slightly heated. In summary, the offset or decentration of the powder spot axis with respect to the laser beam spot axis contributes to the integration of the metal deposition with the substrate and the adhesion of the metal coating to the substrate.

[0032] The offset of the powder nozzle axis with respect to the laser beam axis can be achieved either by keeping the powder nozzle (and thus its cone) fixed and moving the laser head accordingly, or vice versa, i.e., the laser head remains in its original position and the powder nozzle is moved.

[0033] In laser cladding, the diameter of the laser spot is, in some embodiments, between 10 and 40% larger than the diameter of the powder spot. When the diameter of the laser spot is larger than the diameter of the powder spot, the benefits of off-axis offset are enhanced by increasing the interaction time during which a portion of the laser spot interacts with the substrate without material being deposited.

[0034] The use of a laser spot larger than the powder surface, along with the offset between the laser spot axis and the powder axis, contributes to the thermal conditioning of the surface to which the powder will subsequently be deposited, allowing heating of this area shortly before the actual powder deposition. This also allows for surface cleaning, since the interaction of the laser with the area of ​​the substrate to which the powder will be deposited immediately afterward causes evaporation of the graphite flakes in the upper part of the substrate (i.e., its surface and the most superficial thickness of the substrate, approximately 80 µm).

[0035] In some embodiments, during laser coating or laser cladding, a shielding gas is released onto the surface of the substrate exposed to the laser beam but to which no powder has yet been applied. This shielding gas therefore acts on the area that is thermally treated immediately before the powder is applied by the laser beam. The shielding gas can be nitrogen or argon, for example. The inventors have found that applying a shielding gas to a portion of the substrate exposed to the laser radiation but to which no powder has yet been applied helps prevent oxidation of the surface to be treated and homogenizes the surface. Without the shielding gas, the gas produced during the evaporation of the graphite (evaporation due to the laser radiation) tends to oxidize the surface of the substrate.The use of a protective gas reduces surface oxidation caused by the explosion or evaporation of graphite.

[0036] Before laser cladding is used to deposit a metal-based coating on a substrate surface, laser cleaning is applied to the substrate surface without the addition of deposition or coating powder. This removes graphite from the substrate, particularly from the surface to which the coating will later be applied, by irradiating the surface with a laser beam. Generally, the graphite is removed from the surface of the substrate and from the part of the substrate located near this surface. This cleaning takes place before laser cladding, which applies a coating to the substrate surface.In particular, the graphite is preferably removed from the most superficial part of the substrate, typically from a superficial part with a maximum thickness of 80 µm, for example a maximum thickness of 50 µm or a maximum thickness of 30 µm. By removing the graphite essentially only in this superficial area, the substrate below this superficial area is not damaged because its graphite-containing structure is preserved. The graphite is usually in the form of flake graphite, which is typically present when the substrate is gray cast iron. The graphite is removed by irradiating the surface with a laser beam under specific conditions. Along with the graphite, lubricant residues and rust, which are normally found on the surface of the substrate, are also removed.

[0037] As with laser cladding, during laser cleaning, the brake disc substrate preferably rotates or turns, while the laser processing head moves linearly across the substrate surface. The linear movement follows a radial trajectory on the substrate surface. The same or similar parameters as for laser cladding can be used for laser cleaning.

[0038] In both laser cladding and, if present, cleaning, the energy density applied to the substrate surface depends on several parameters, such as the laser beam power, the area of ​​the laser spot applied to the surface, and the required cycle time (the period of time during which the surface cleaning or coating must be performed). The energy density of a laser beam follows the equation: Energy density = energy / laser spot area = (power × cycle time) / laser spot area.

[0039] In laser cladding, the energy density must be high enough to allow thermal treatment of the surface to which the powder is to be applied and melting of the powder to deposit a coating. During cleaning, the energy density must be sufficient to remove the flake graphite from the surface of the substrate while essentially maintaining the integrity of the substrate below the surface.

[0040] In embodiments of this disclosure, the power of the laser beam used in laser cladding ranges between 6 and 16 kilowatts (kW), both inclusive, preferably between 7 and 12 kW, both inclusive, and more preferably between 7.5 and 10 kW, both inclusive. This power has been proven to be appropriate when appropriate laser spot diameters and cycle time values ​​are selected.

[0041] In some embodiments, the diameter of the laser spot used in laser cladding is in a range between 1.5 and 4 mm, preferably between 2 and 4 mm, more preferably between 2.2 and 3.7 mm, and even more preferably between 2.5 and 3.5 mm. The diameter of the powder spot is in a range between 1 and 3.5 mm, preferably between 1 and 2.5 mm, and even more preferably between 1 and 2 mm.

[0042] The cycle time can be set or selected based on various parameters, such as the size of the brake disc (surface to be cleaned) and the disc's rotation speed. The selected cycle time depends on the circumstances and the specific application. Often, a specific cycle time value or a maximum cycle time is specified. Depending on the size of the brake disc to be treated, the cycle time can be, for example, less than 120 s (seconds), less than 80 s, less than 55 s (seconds), less than 30 s, or even less than 20 s. Therefore, for a required cycle time, suitable values ​​for the laser beam transmission power and the laser spot diameter must be selected to produce a brake disc with a more efficient friction surface. In general, for a given laser spot area, the cycle time can be reduced by increasing the laser beam power.

[0043] In some embodiments, the laser cladding cycle time is selected to be in the range between 20 and 55 seconds. Within this range, the coating applied to the substrate bonds well to the substrate surface when the laser beam power used is between 6 and 16 kW.

[0044] The cycle time may be dictated by production requirements. In this case, the cycle time is preferably as short as possible so that the largest possible number of brake discs are produced per unit of time (e.g., working day). To optimize the production of finished brake discs, if laser cleaning to remove graphite is performed before laser cladding, the laser cleaning cycle time is preferably selected to match the cycle time during which laser cladding is applied to deposit a metal-based coating on the surface of the substrate from which graphite has previously been removed. In this way, the operation of the various production cells for the different production steps can be synchronized.

[0045] In embodiments of the disclosure, the wavelength of the laser system used to irradiate the substrate surface is preferably in the range between 800 and 1200 nanometers (nm, 10-9 m), for example between 1000 and 1150 nm or between 1030 and 1100 nm. Alternatively, other wavelengths may be used that are also suitable for graphite evaporation.

[0046] During laser cladding of a metal-based coating, the surface is preferably irradiated with a laser beam emitted at a power ranging between 6 and 16 kW, with the laser spot diameter ranging between 1.5 and 4 mm, and the cycle time is suitably selected, for example, between 20 and 55 seconds. As already mentioned, to optimize the production of finished brake discs, when laser cleaning is used prior to laser cladding, the laser cleaning cycle time is preferably selected to match the cycle time for applying a metal-based coating to the surface of the substrate from which graphite has previously been removed.

[0047] In some embodiments of laser cladding for depositing a first cladding layer, the laser beam delivers an energy density on the surface of the substrate in the range between 14 kJ / mm 2 and 50 kJ / mm 2 .

[0048] The inventors have found that the thermal preparation of the surface due to the aforementioned axial shift during laser cladding, which occurs immediately before the actual deposition of the material, conditions or prepares the surface in such a way that the adhesion of the subsequently applied powder is improved. This conditioning of the surface to which a coating is to be applied is particularly improved if laser cleaning has been previously applied (in a separate step) to remove graphite from the surface of the substrate, since the laser beam used in laser cladding contributes to the removal of additional lamellar graphite located, for example, deeper in the substrate than the most superficial thickness.For example, laser cleaning can result in the evaporation of 50 to 100% of the graphite in the top 30 µm of the substrate, and additional laser cleaning performed during the material deposition process can cause the evaporation of graphite in a deeper region of the substrate, such as between 30 and 50 µm. Without this additional laser heating / conditioning process performed immediately before deposition of the overlay material (due to axis shift), the graphite still present in the surface of the substrate can explode during material deposition due to the high temperature reached by the molten pool, and because the voids or "bubbles" left open by the graphite explosion cannot be filled with the deposited material due to the immediate cooling and solidification of the molten pool.This is prevented or at least reduced by the additional laser conditioning / cleaning process.

[0049] In certain embodiments, only a single layer is applied during the deposition of an overlay layer. The layer may consist of a mixture of a metal and a carbide, with the metal preferably being steel and the carbide preferably being tungsten carbide or titanium carbide.

[0050] For example, if the laser beam power is set to 6 kW and the cycle time to 30 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 2.4 and 3.3 mm. In this case, the energy density applied to the substrate surface is between 21 and 40 kJ / mm 2Or, if the laser beam power is set to 6 kW and the cycle time to 50 s, a suitable metal-based coating can be achieved by choosing a laser spot diameter between 3 and 4 mm. In this case, the energy density applied to the substrate surface is between 21 and 42 kJ / mm 2 Or, if the laser beam power is set to 6 kW and the cycle time to 70 s, a suitable metal-based coating can be achieved by choosing a laser spot diameter between 3.5 and 4 mm. In this case, the energy density on the substrate surface is between 32 and 44 kJ / mm 2At this power level, large laser spot diameters, e.g., between 3.5 and 4 mm, are less preferable, as they require relatively large powder spot diameters (which should be only slightly smaller than the laser spot diameter), for which the applied power may not be sufficient to completely melt the powder, even with long cycle times. Therefore, at a laser power of 6 kW, smaller laser spot areas and thus shorter cycle times are preferred.

[0051] For example, if the laser beam power is set to 7 kW and the cycle time to 30 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 2.5 and 3.3 mm. In this case, the energy density applied to the substrate surface is between 21 and 42 kJ / mm 2Or, if the laser beam power is set to 7 kW and the cycle time to 50 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 3.2 and 4 mm. In this case, the energy density applied to the substrate surface is between 27 and 42 kJ / mm 2 Or, if the laser beam power is set to 7 kW and the cycle time to 70 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 3.8 and 4 mm. In this case, the energy density applied to the substrate surface is between 38 and 43 kJ / mm 2 However, for the same reason as with the 6 kW power, small laser spot areas and thus short cycle times are preferred.

[0052] For example, if the laser beam power is set to 8 kW and the cycle time to 30 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 2.7 and 3.7 mm. In this case, the energy density applied to the substrate surface is between 22 and 42 kJ / mm 2 Or, if the laser beam power is set to 8 kW and the cycle time to 50 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 3.3 and 4 mm. In this case, the energy density applied to the substrate surface is between 30 and 46 kJ / mm 2 .

[0053] For example, if the laser beam power is set to 9 kW and the cycle time to 30 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 2.7 and 3.7 mm. In this case, the energy density applied to the substrate surface is between 25 and 47 kJ / mm 2 Or, if the laser beam power is set to 9 kW and the cycle time to 50 s, a suitable metal-based coating can be achieved by choosing a laser spot diameter between 3.5 and 4 mm. In this case, the energy density applied to the substrate surface is between 35 and 46 kJ / mm 2 .

[0054] For example, if the laser beam power is set to 12 kW and the cycle time to 30 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 3.2 and 4 mm. In this case, the energy density applied to the substrate surface is between 28 and 45 kJ / mm 2 Or, if the laser beam power is set to 12 kW and the cycle time to 19 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 2.6 and 3.5 mm. In this case, the energy density applied to the substrate surface is between 23 and 43 kJ / mm 2 .

[0055] Considering a typical brake disc, when applying the above parameters (laser beam with a power between 6 and 16 kW, laser spot diameter between 1.5 and 4 mm, powder spot diameter between 1 and 3.5 mm, with the substrate rotating at a linear speed in the range between 80 and 240 m / min and the laser beam moving linearly at a speed of less than 500 mm / minute), a circular, annular surface of a substrate with an inner diameter between 160 and 230 mm and an outer diameter between 270 and 410 mm results, requiring laser deposition to apply a deposition layer with a duration in the range between 20 seconds and 55 seconds.

[0056] Laser cleaning can use the same or a different laser system that is used for coating.

[0057] In embodiments where laser cleaning is used to remove graphite from the surface of the substrate to which a coating is to be applied after the disclosed laser deposition, the surface is irradiated with a laser beam preferably emitting at a power in the range between about 2 and about 12 kW, more preferably between about 4 and about 8 kW, and even more preferably between about 5 and about 7 kW. This power has been proven effective when appropriate laser spot diameters and cycle time values ​​are selected.

[0058] During cleaning, a laser system is used that generates a circular laser spot. The diameter of the laser spot is preferably in the range between about 1.5 and about 4 mm. Preferred values ​​for the laser spot diameter are between about 2 and about 4 mm, preferably between about 2.2 and about 3.7 mm, and more preferably between about 2.5 and about 3.5 mm. By selecting an appropriate cycle time and laser beam power, the graphite is correctly removed from the substrate.

[0059] During cleaning, the cycle time is preferably selected to be in the range between approximately 20 and approximately 120 seconds, preferably between approximately 20 and approximately 55 seconds. The laser beam power (preferably between approximately 2 and approximately 12 kW) and the laser spot diameter (between approximately 1.5 and approximately 4 mm) must be selected to ensure that the graphite is correctly removed from the substrate.

[0060] During cleaning, the laser beam in some embodiments delivers an energy density on the surface of the substrate in the range between 10 kJ / mm 2 and 45 kJ / mm 2 , preferably between 14 kJ / mm 2 and 40 kJ / mm 2 .

[0061] After cleaning, the amount of graphite on the surface of the substrate is thus reduced. The absence of graphite due to evaporation during cleaning leaves holes on the surface, which lead to an increase in the contact area of ​​the substrate, which is intended to receive the deposited material in order to form a metal-based layer during subsequent laser deposition. These holes are usually in the form of elongated branches, which means a significant increase in the contact area. The larger the contact area of ​​the substrate, the more deposited material can settle and fill the holes on the substrate surface. In particular, it has been observed that the contact area of ​​the substrate is increased by more than 20%, for example by more than 30% or more than 50%, when the described laser cleaning is applied. The inventors have observed that when a metal-based deposition layer is applied to the already cleaned substrate (i.e.The substrate, which after irradiation of the surface with a laser beam, as stated above, has a reduced amount of graphite on its surface), i.e., when a laser cleaning pretreatment is applied separately before the application of the laser cladding coating, the adhesion of the cladding layer(s) is increased (the cladding layer is well integrated with the substrate), thus improving the wear resistance and friction coefficient of the brake disc once manufactured. This is due to the fact that holes in the substrate (in the uppermost part of the substrate), created by the evaporation of graphite during the laser cleaning pretreatment, are filled with the deposited cladding material during the subsequent laser cladding.

[0062] Furthermore, because the previously laser-treated substrate has a lower amount of flake graphite in its surface, the likelihood of graphite evaporating during the deposition of the metal-based overlay layer is reduced, and unwanted pits and "bubbles" are therefore less likely to form during deposition due to abrupt graphite deposition (evaporation). This increases the contact area between the substrate and the deposited overlay layer. It has also been found that particulate matter emissions typically generated during use of the brake disc are also significantly reduced.

[0063] During laser cleaning, the laser system must operate at a wavelength suitable for graphite evaporation. Therefore, the wavelength of the laser system used to irradiate the substrate surface is preferably in the range between 800 and 1200 nanometers (nm, 10-9 m), for example, between 1000 and 1150 nm or between 1030 and 1100 nm. Alternatively, other wavelengths suitable for graphite evaporation can be used.

[0064] As with laser cladding, laser radiation is emitted from a laser processing head, which, for example, carries a nozzle. The emitted laser radiation passes coaxially through the nozzle, along the nozzle's longitudinal axis. To ensure that the laser beam can be directed onto the surface of the substrate during cleaning and remove graphite, the laser beam is preferably directed in such a way that it defines any pattern (a line, a regular or irregular geometric figure, or another pattern) on the surface of the substrate to be exposed to the laser radiation. Laser cleaning can utilize the same or similar operating characteristics as laser cladding (type of laser system, pattern path followed by the laser beam, angular velocity of the substrate, linear motion of the laser processing head, etc.).

[0065] By applying laser cleaning to the substrate surface, the amount of lamellar graphite in the upper part of the substrate (i.e., in the uppermost layer thickness of approximately 80 µm) is significantly reduced. In particular, it was found that between 50 and 100% of the graphite flakes present in the surface, especially within a thickness of 30 µm from the surface, are evaporated by the laser radiation.

[0066] Thus, when the described laser cleaning is applied to the surface of the substrate, evaporation of at least 50% of the flake graphite present near the surface of the substrate is achieved without causing significant damage to the substrate below this uppermost part of the substrate (e.g., by impairing its homogeneity or changing its microstructure).

[0067] For example, if the laser beam power is set to 2 kW and the cycle time to 30 s, selecting a laser spot diameter between 1.5 and 2.1 mm during cleaning will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density acting on the substrate surface is between 17 and 32 kJ / mm 2 Or, if the laser beam power is set to 2 kW and the cycle time to 120 s, selecting a laser spot diameter between 3.1 and 4.0 mm achieves evaporation of the flake graphite from the substrate surface without significant damage. The applied energy density is also between 17 and 32 kJ / mm 2 .

[0068] For example, if the laser beam power is set to 3 kW and the cycle time to 30 s, a laser spot diameter between 1.9 and 2.55 mm will evaporate flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 17 and 32 kJ / mm 2 Or, if the laser beam power is set to 3 kW and the cycle time to 90 s, selecting a laser spot diameter between 3.2 and 3.82 mm achieves the evaporation of flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 20 and 35 kJ / mm 2 .

[0069] For example, if the laser beam power is set to 4 kW and the cycle time to 30 s, a laser spot diameter between 2.2 and 2.95 mm will evaporate flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 17 and 32 kJ / mm 2 Or, if the laser beam power is set to 4 kW and the cycle time to 80 s, selecting a laser spot diameter between 3.3 and 4.00 mm achieves the evaporation of flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 20 and 37.5 kJ / mm 2 .

[0070] For example, if the laser beam power is set to 5 kW and the cycle time to 30 s, a laser spot diameter between 2.45 and 3.3 mm will evaporate the flake graphite from the substrate surface without significant damage. In this case, the energy density on the substrate surface is between 17 and 32 kJ / mm 2 Or, if the laser beam power is set to 5 kW and the cycle time to 70 s, selecting a laser spot diameter between 3.4 and 4.00 mm achieves the evaporation of flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 27 and 38 kJ / mm 2 .

[0071] For example, if the laser beam power is set to 6 kW and the cycle time to 30 s, a laser spot diameter between 2.7 and 3.6 mm will evaporate the flake graphite from the substrate surface without causing significant damage. In this case, the energy density on the substrate surface is between 17 and 32 kJ / mm 2 Or, if the laser beam power is set to 6 kW and the cycle time to 55 s, selecting a laser spot diameter between 3.3 and 4.00 mm will achieve the evaporation of flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 25 and 38 kJ / mm 2 .

[0072] For example, if the laser beam power is set to 7 kW and the cycle time to 30 s, selecting a laser spot diameter between 2.91 and 3.9 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 17 and 32 kJ / mm 2 Or, if the laser beam power is set to 7 kW and the cycle time to 51 s, selecting a laser spot diameter between 3.5 and 4.00 mm achieves the evaporation of flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 27 and 38 kJ / mm 2 .

[0073] For example, if the laser beam power is set to 8 kW and the cycle time to 30 s, selecting a laser spot diameter between 3.11 and 4.00 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 19 and 32 kJ / mm 2 Or, if the laser beam power is set to 8 kW and the cycle time to 45 s, selecting a laser spot diameter between 3.2 and 4.00 mm achieves the evaporation of flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 27 and 44 kJ / mm 2 .

[0074] For example, if the laser beam power is set to 12 kW and the cycle time to 25 s, selecting a laser spot diameter between 3.00 and 4.00 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 23 and 42 kJ / mm 2 Or, if the laser beam power is set to 12 kW and the cycle time to 30 s, selecting a laser spot diameter between 3.2 and 4.00 mm achieves the evaporation of flake graphite from the substrate surface without significant substrate damage. In this case, the energy density on the substrate surface is between 28 and 44 kJ / mm 2 .

[0075] While power levels above 12 kW and up to approximately 24 kW can function correctly during cleaning, taking into account the required cycle time, the inventors have found that power levels above 12 kW, and especially close to 24 kW, lead to deformation of the substrate (brake disc). For example, it has been observed that the substrate surface loses its flatness (bows) towards the outer periphery due to the high power applied to the brake disc surface, even with a short cycle time. For this reason, laser power levels above 12 kW are less preferred, for example, over 13 kW or over 14 kW.

[0076] Although the inventors have observed a reduction of graphite in the surface of the substrate when cleaning is carried out with a power of less than 2 kW, e.g., between 200 W and 2 kW, the cleaning performance in this case is only relatively good at relatively long cycle times (e.g., about 120 s) compared to short cycle times (e.g., about 30 s), since longer cycle times mean a longer interaction between the applied power and the surface to be treated, thereby increasing the probability of evaporation of graphite from the surface of the substrate.

[0077] Considering a typical brake disc, when applying the above parameters (laser beam with a power between 2 and 12 kW, diameter of the laser spot between 1.5 and 4 mm), with the substrate rotating at a linear speed in the range of 80 and 240 m / min and the laser beam moving linearly at a speed of less than 500 mm / minute, a circular, annular surface of a substrate with an inner radius between 160 and 230 mm and an outer radius between 270 and 410 mm requires pre-treatment (laser cleaning) to remove graphite (cleaning) with a duration in the range of 20 seconds to 55 seconds.

[0078] In some embodiments, a shielding gas is ejected onto the surface of the substrate during cleaning. The shielding gas is ejected, for example, through a gas nozzle. The gas nozzle can be located on the same laser processing head as the laser processing head that carries the nozzle through which the laser radiation is ejected. The shielding gas can be, for example, nitrogen or argon. The use of a shielding gas helps prevent oxidation of the surface to be treated after cleaning and contributes to surface homogenization, for example, by obscuring or reducing the trace of the laser passes, since the overlap between adjacent passes can be reduced. Without the shielding gas, the gas produced during the evaporation of the graphite tends to oxidize the surface of the substrate. In addition, without the shielding gas, more time is required to homogenize the surface (i.e.reduce the trace of the laser passes) because a larger overlap between adjacent passes is required.

[0079] In certain embodiments, applying an overlay layer comprises applying a first overlay layer and a second overlay layer to the first overlay layer, wherein the first overlay layer consists, for example, of metal, such as steel, and the second overlay layer consists, for example, of a mixture of metal and a carbide, preferably tungsten carbide or titanium carbide.

[0080] When two metallic coatings are applied, cleaning (pretreatment) of the surface by irradiation with a laser beam (without powder deposition) is performed only before the first coating layer is applied (and not before the second coating layer). As with laser deposition for applying the first coating layer to the substrate, the second coating layer is applied using a laser beam that creates a laser spot whose axis is offset from the axis of the delivered powder spot. Furthermore, the area of ​​the laser spot (as projected onto the substrate surface) is larger than the area of ​​the powder (as deposited on the surface), with the diameters of the laser spot and powder being in a similar ratio.The application of the second coating layer is therefore essentially the same as the application of the first coating layer, including the type and size of the powder material, except for the selection of certain operating parameters.

[0081] In some embodiments, laser cladding involves applying two deposition layers to the surface of the substrate. To apply a second coating to an already deposited first coating, the surface is irradiated with a laser beam emitted at a power in the range between about 7 and about 18 kW for a suitably selected cycle time, preferably between about 20 and about 55 seconds. Preferred values ​​for the laser beam power are in the range between about 7.5 kW and about 14 kW, more preferably between about 7.5 kW and about 12 kW, which have proven to be correct when suitable laser spot diameters and cycle times are selected. Preferred values ​​for the laser spot diameter are in the range between about 1.5 and about 4 mm. The preferred powder spot diameters are between 1 and 3.5 mm.Since the second deposition layer is usually thicker than the first deposition layer, higher power and / or a longer cycle time are usually required to melt the required powder.

[0082] In some embodiments of the second laser cladding to produce a second coating, the laser beam provides an energy density on the surface of the substrate in the range between 25 kJ / mm 2 and 70 kJ / mm 2 .

[0083] For example, if the laser beam power is set to 7 kW and the cycle time to 30 s, a suitable second metal-based layer can be achieved by selecting a laser spot diameter between 2.2 and 3.0 mm. In this case, the energy density applied to the substrate surface is between 29 and 54 kJ / mm 2Or, if the laser beam power is set to 7 kW and the cycle time to 50 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 2.7 and 3.5 mm. In this case, the energy density applied to the substrate surface is between 36 and 60 kJ / mm 2 Small laser spot diameters are preferred because the powder spot diameter is only slightly smaller than the laser spot diameter, and large powder particles require higher power for melting.

[0084] For example, if the laser beam power is set to 8 kW and the cycle time to 30 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 2.2 and 3.0 mm. In this case, the energy density applied to the substrate surface is between 33 and 63 kJ / mm 2Or, if the laser beam power is set to 7 kW and the cycle time to 50 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 2.7 and 3.3 mm. In this case, the energy density applied to the substrate surface is between 46 and 70 kJ / mm 2 Small laser spot diameters are preferred because the powder spot diameter is only slightly smaller than the laser spot diameter, and large powder particles require higher power for melting.

[0085] For example, if the laser beam power is set to 9 kW and the cycle time to 30 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 2.3 and 2.9 mm. In this case, the energy density applied to the substrate surface is between 40 and 65 kJ / mm 2Or, if the laser beam power is set to 9 kW and the cycle time to 50 s, a suitable metal-based coating can be achieved by choosing a laser spot diameter between 3 and 4 mm. In this case, the energy density applied to the substrate surface is between 35 and 63 kJ / mm 2 .

[0086] For example, if the laser beam power is set to 12 kW and the cycle time to 30 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 2.7 and 4 mm. In this case, the energy density applied to the substrate surface is between 28 and 63 kJ / mm 2Or, if the laser beam power is set to 12 kW and the cycle time to 40 s, a suitable metal-based coating can be achieved by selecting a laser spot diameter between 3.1 and 4 mm. In this case, the energy density applied to the substrate surface is between 38 and 63 kJ / mm 2 .

[0087] In summary, thanks to the thermal treatment of the surface immediately before powder spot application, due to the difference between the diameters of the laser spot and powder spot, and also due to the offset between the powder cone axis and the laser beam axis, the laser heat acting on the surface thermally prepares and additionally cleans the surface. The surface is prepared to receive the material by removing additional graphite lamellae and thus creating new voids that are filled with metal-based powder (which quickly melts on the surface), but without creating unwanted bubbles in the surface of the substrate that would form if the material were deposited at exactly the same time as the laser heats the surface. Consequently, the applied coating is flat, homogeneous and well bonded to the substrate.

[0088] A second aspect of the disclosure relates to a brake disc manufactured with or by using the brake disc manufacturing apparatus of the first aspect of the invention.

[0089] Once the substrate surface has been cleaned following the described laser cleaning, the thermal treatment during the subsequent laser deposition process conditions or prepares the surface due to the offset of the axes, improving the adhesion of the subsequently applied coating. The laser radiation used in laser deposition removes additional lamellar graphite, which is typically present deeper within the substrate relative to its most superficial thickness. For example, while between 80 and 100% of the graphite in the top 30 µm of the substrate was evaporated during laser cleaning, the additional laser treatment during material deposition causes the evaporation of graphite in a deeper region of the substrate, e.g., at a depth between 30 and 50 µm.If these deeper graphite flakes were not removed, they could explode during powder deposition due to the high temperature reached by the molten pool on the substrate surface. However, the holes created by the explosion could not be filled with molten material due to the rapid cooling and solidification of the molten pool. This results in the resulting coating containing unwanted holes. For this reason, it is strongly recommended that the additional graphite flakes be removed somewhat earlier, rather than at the exact moment the powder is added and melted onto the substrate, to prevent the formation of voids and "bubbles" during the material deposition.

[0090] A third aspect of the disclosure relates to a brake disc manufacturing device or a device for manufacturing brake discs, comprising:

[0091] a laser deposition device or a laser deposition system comprising a laser head and configured to apply a metal-based coating layer to a surface of a substrate for producing a brake disc, the substrate being made of a graphite-containing metallic material, by applying laser deposition welding, the laser deposition system being configured to deposit powder onto the surface while a laser beam is irradiated onto the surface, the powder being supplied from a powder nozzle coupled to the laser head from which the laser beam is emitted, such that the supplied powder and the laser beam move together over the surface to be coated as the laser head moves,

[0092] wherein the diameter of a laser spot applied to the surface by the laser beam is larger than the diameter of a powder spot applied to the surface from the powder nozzle, and the axis of the laser spot applied to the surface is offset with respect to the axis of the powder spot applied to the surface.

[0093] In some embodiments, the brake disc manufacturing apparatus further comprises a laser cleaning system configured to remove graphite from the surface of the brake disc manufacturing substrate before applying a metal-based coating to the surface of the substrate by applying a cleaning step in which the surface is irradiated with a laser beam using either the laser head of the laser deposition apparatus or the laser system for applying the coating or another laser head.

[0094] In some embodiments, the brake disc manufacturing device or the device for manufacturing brake discs further comprises a rotation device or rotating device configured to rotate the substrate of the brake disc during the application of the cleaning and / or during the deposition of a metal-based coating, while the laser head(s) from which the laser beam is emitted moves / moves linearly on the surface of the substrate, wherein the linear movement follows a radial trajectory on the surface of the substrate.

[0095] In some embodiments, the rotating device is configured to rotate the brake disc at a linear speed in the range of 80 to 240 m / minute, preferably in the range of 120 to 200 m / minute.

[0096] In some embodiments of the apparatus for producing brake discs, the axis of the powder spot is offset with respect to the axis of the laser spot by an amount between 0 and 20% of the diameter of the laser spot, preferably between 2.5 and 20% thereof, more preferably between 2.5 and 15% thereof, even more preferably between 5 and 12.5% ​​thereof.

[0097] In some embodiments, the laser deposition device or laser system is configured for deposition welding such that the diameter of the laser spot is between 10 and 40% larger than the diameter of the powder spot to apply a metal-based coating to the surface of the substrate.

[0098] In some embodiments, the laser deposition device or the laser system for deposition welding is configured to adjust the power of the laser beam in a range between 6 kW and 16 kW, preferably between 7 kW and 12 kW and particularly preferably between 7.5 and 10 kW, and the cycle time is preferably between 20 and 55 seconds.

[0099] In some embodiments, the laser deposition device or laser system is configured for deposition welding such that the diameter of the laser spot used in laser deposition welding is in a range between 1.5 and 4 mm, preferably between 2 and 4 mm, more preferably between 2.2 and 3.7 mm, and more preferably between 2.5 and 3.5 mm; and the diameter of the powder spot is in a range between 1 and 3.5 mm, preferably between 1 and 2.5 mm, and more preferably between 1 and 2 mm.

[0100] In some embodiments, the laser system for cladding is configured for operation in the cladding process for depositing a metal-based cladding layer such that an energy density on the surface of the substrate is in the range between 14 kJ / mm 2 and 50 kJ / mm 2 is applied.

[0101] In some embodiments, the laser cleaning system is configured such that, during the cleaning application, the surface is irradiated with a laser beam emitting at a power in the range between 2 and 12 kW, wherein the diameter of the laser spot is in the range between 1.5 and 4 mm.

[0102] In some embodiments, the laser cleaning system is configured such that the surface is irradiated during cleaning with a laser beam emitting at a power in the range between 4 and 8 kW, preferably between 5 and 7 kW.

[0103] In some embodiments, the laser system for cleaning is configured such that during cleaning the diameter of the laser spot used for graphite removal is in a range between 2 and 4 mm, preferably between 2.2 and 3.7 mm, and more preferably between 2.5 and 3.5 mm.

[0104] In some embodiments, the laser cleaning system is configured such that the laser beam during cleaning has an energy density on the surface of the substrate in the range between 10 and 45 kJ / mm 2 delivers.

[0105] In some embodiments, the apparatus for manufacturing brake discs further comprises a shielding gas supply configured to deliver a shielding gas to the surface of the substrate during the application of the cleaning and / or during the deposition of a metal-based coating layer while the surface is irradiated with the laser beam, wherein the shielding gas is nitrogen or argon.

[0106] A fourth aspect of the disclosure relates to a use of the brake disc manufacturing apparatus of the third aspect for providing a brake disc, wherein the laser cladding deposits a single layer which preferably consists of a mixture of a metal and a carbide, wherein the metal is preferably steel and the carbide is preferably tungsten carbide or titanium carbide.

[0107] A fifth aspect of the disclosure relates to a use of the brake disc manufacturing apparatus of the third aspect for providing a brake disc, wherein a first metal-based coating layer is provided by laser deposition welding and further a second laser deposition welding is provided to apply a second metal-based coating layer to the first metal-based coating layer.

[0108] In some embodiments of the fifth aspect, the laser cladding apparatus or laser cladding system is configured for deposition of the second metal-based cladding layer such that the power of the laser beam is in a range between 7 and 18 kW, preferably between 7.5 and 14 kW, and more preferably between 7.5 and 12 kW; and the cycle time is selected to be between 20 and 55 seconds.

[0109] In some embodiments of the fifth aspect, the laser deposition device or the laser system for deposition welding is configured such that, during deposition welding for depositing the second metal-based deposition layer, it operates such that the energy density on the surface of the substrate is in the range between 25 and 70 kJ / mm 2 lies.

[0110] In some embodiments of the fifth aspect, the laser deposition device or the laser system for deposition welding is configured such that a layer of metal, preferably steel, is applied during the first laser deposition welding and a layer of a mixture of a metal and a carbide, wherein the metal is preferably steel and the carbide is preferably tungsten carbide or titanium carbide, is applied during the second laser deposition welding.

[0111] A sixth aspect of the disclosure relates to a brake disc produced with the brake disc manufacturing apparatus of the third aspect and / or using one of the fourth and fifth aspects, wherein the substrate is preferably made of gray cast iron.

[0112] Further advantages and features of the invention will become apparent from the following detailed description and are particularly emphasized in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0113] To complete the description and better understand the invention, a series of drawings are attached. These drawings form part of the description and illustrate embodiments of the invention, which are not to be understood as limiting the scope of the invention, but merely as examples of how the invention may be carried out. The drawings include the following figures: Fig. shows a photo of a conventional brake disc before applying a treatment to it. Fig. show photographs of the brake disc after application of laser-based cleaning according to this disclosure. Fig. show photographs of a brake disc as in Fig. after applying laser-based cleaning according to this disclosure. The Fig. schematically show laser cladding applied to the previously cleaned surface of a substrate, according to embodiments of the disclosure. Fig. schematically shows a section through a laser beam cladding system that can be used in laser beam cladding according to embodiments of the disclosure. Fig. schematically shows the shape of a metallic coating formed on the substrate while depositing a metal-based powder during laser deposition according to embodiments of the disclosure. The Fig. show schematically how the laser beam can be applied to the surface of the substrate to be treated, as described in the disclosure. The Fig. show OM images of brake discs to which a single coating layer was applied. The Fig. show a cross-sectional view of an AISI 316L coating applied to the surface of a brake disc substrate where neither pre-cleaning nor axis centering was performed during laser cladding. Fig. shows an OM image of brake discs to which a single coating layer was applied. Fig. shows an OM image of an overlay layer applied to a brake disc according to embodiments of this disclosure. Fig. shows a cross-sectional view of a substrate to which two coating layers have been applied according to the embodiments of this disclosure. Fig. shows a cross-sectional view of a substrate to which two coating layers have been applied according to the embodiments of this disclosure. Fig. shows a cross-sectional view of a substrate to which two coating layers have been applied according to the embodiments of this disclosure. The Fig. schematically show a cleaning applied to a surface of a substrate of a brake disc according to embodiments of the disclosure. The Fig. show SEM images of the surface of a substrate after treatment with laser cleaning according to embodiments of the disclosure. The Fig. show cross-sections of a substrate after treatment with laser cleaning according to embodiments of the disclosure. Fig. shows a photo of the brake disc before treatment. Fig. shows an SEM image of the surface of a substrate without laser cleaning. Fig. shows an SEM image of the surface of a brake disc to which no laser cleaning or various laser cleaning processes were applied. Fig. show brake discs after laser cleaning. Fig. shows an SEM image of the surface of the substrate after applying laser cleaning according to the embodiments of the disclosure. The Fig. show SEM images of brake discs to which no laser cleaning or different laser cleaning processes were applied. The Fig. show a photograph of a brake disc after applying a laser treatment and laser cladding according to the embodiments of the disclosure. The Fig. show OM images of brake discs to which a single coating was applied after the described laser cladding process. In all cases, the energy density of the applied laser beam during laser cladding is 39821 J / mm 2 . The Fig. show OM images of brake discs to which a single coating layer was applied without any misalignment or offset of the laser spot axis and the powder spot axis. In all cases, the energy density of the applied laser beam during laser cladding is 39821 J / mm 2 . Fig. shows an OM image of a brake disc to which a single layer was applied using the described laser cladding process. The energy density of the applied laser beam is 28,937 J / mm 2 . The Fig. show a brake disc manufactured with the disclosed brake disc manufacturing apparatus for applying two coating layers according to embodiments of the disclosure. The Fig. show cross-sections of the brake disc after it has been completely manufactured. Fig. are SEM images. The Fig. are OM images. Fig. shows an OM image of a brake disc to which two coating layers were applied without any misalignment of the laser spot axis and the powder spot axis. DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

[0114] The Fig. show photographs of conventional brake discs 10 before their treatment (the substrate has not yet been cleaned with a laser, and no laser deposition layer(s) have yet been applied). The brake discs consist of a substrate made of a metallic material, in the version shown made of gray cast iron. The discs are wheel-shaped and have an inner disc part 15 and an outer disc part 14 that surrounds the inner disc part 15 (outside). Both parts 14, 15 have a cylindrical shape, with the inner part 15 being thicker than the outer part 14. For this reason, the inner part 15 can be called a "hat" because its shape is reminiscent of the crown of a hat, while the outer disc part 14 resembles the brim of a hat. The outer disc part 14 forms a ring with an inner radius and an outer radius. The outer disc part 14 has two outer annular friction surfaces that lie opposite each other.The inner diameter of the outer disc part 14 of the in . Fig. The disc shown is 177 mm and its outer diameter is 306 mm. The inner diameter of the outer disc part 14 of the Fig. The disc shown is 220 mm and its outer diameter is 350 mm. In the top view of the Fig. only one friction surface 13' is visible.

[0115] During braking, these surfaces are pressed against a brake pad, thus braking the brake disc. The illustrated brake disc 10, in particular its outer part 14, is made of grey cast iron. In the following, reference numeral 12 is used to refer to the substrate of the outer part 14, which must be treated with the laser, although the inner part (cap part) 15 of the brake disc may be made of the same material (grey cast iron in the example shown). The substrate 12 contains graphite, in particular flake graphite, as in the Fig. shown (dark slats 51 in Fig. , which will be described in detail later.

[0116] The Fig. schematically show a laser deposition process for applying one or more coating layers to a surface 13, 13' of the substrate in order to obtain a manufactured brake disc, i.e. a brake disc with increased wear and corrosion resistance and / or an increased coefficient of friction with respect to the wear and corrosion resistance and / or the coefficient of friction of an uncoated brake disc. The surface can be one of the two surfaces 13, 13' of the outer disc part 14. The brake disc can be provided with one or more coatings, e.g. with one or two coatings or even with more than two coatings, depending on various factors, e.g. the expected performance of the manufactured brake disc. The coated surface is a friction surface of a brake disc.

[0117] The at least one coating is applied by laser deposition, in which powder is applied to the surface 13, 13' of the substrate while a laser beam is irradiated onto the surface 13, 13' to be coated from a laser head that is moved along the surface to be treated while the disk rotates. The powder is supplied from a powder nozzle coupled to the laser head from which the laser beam is emitted, so that the laser beam and the powder nozzle move together radially along the surface to be coated as the laser head moves.

[0118] To apply a coating layer to the surface 13, 13', a laser beam head performs a radial movement along the radius of the substrate while the base rotates. The surface can be one of the two surfaces 13, 13' of the outer disk part 14. In the Fig. 2A and Fig. 2B shows only a radial portion of the disk 10 (and thus a radial portion of the substrate 12 forming a friction surface 13, 13'). The section shown includes the disk center (indicated by a cross surrounded by a circle) and the inner 141 and outer 142 radius of the substrate 12, whose surface 13, 13' is to be treated. A coating is applied to the surface 13, 13' by laser deposition welding. The laser radiation is emitted by a laser processing head (not shown), which carries, for example, a nozzle through which the laser radiation is emitted. The laser head (not shown), which guides the laser beam, also carries an attached powder nozzle (not shown) connected to the laser head. The powder nozzle dispenses powder as the laser head moves. A carrier gas is typically used to convey the powder to the surface to be treated.

[0119] The surface 13, 13' is irradiated with a laser beam, which defines a laser spot 30 on the surface of the substrate. In one embodiment, the movement of the laser beam and thus of the laser spot 30 on the surface 13, 13' is in the Fig. represented by a straight dashed arrow. Fig. shows the beginning of a laser beam deposition welding process in a particular embodiment. In this case, the point from which the laser beam begins to move is a point on the inner radius 141 of the substrate 12. The movement of the laser beam could also begin at a point on the outer radius 142 of the substrate 12, as in Fig. In each case, the substrate 12 rotates around its axis of rotation at a certain angular velocity simultaneously with the movement of the laser beam. The curved arrow indicating the disk center in the Fig. represents the rotation of the disk (the substrate 12). In preferred embodiments, the linear velocity of the laser beam (and the powder supplied from the powder nozzle coupled to the laser head) is constant, and the angular velocity (rpm) of the disk is configured to vary depending on the radial position of the laser beam and hence of the laser spot 30 and the powder spot 40 on the surface to be treated, so that the actual linear velocity of the disk is constant and the interaction of the laser beam (and the applied powder) with the substrate is also constant.The simultaneous linear forward movement of the laser head along the linear trajectory shown by a dashed line 21 (from a point on the inner radius 141 of the substrate 12 to a point on the outer radius 142 of the substrate 12 or vice versa) and the rotation of the substrate 12 generate a spiral laser beam trajectory on the substrate 12.

[0120] Once the laser beam, and thus the laser spot 30 and the powder spot 40, have moved radially from the inner radius 141 of the substrate 12 to the outer radius 142 or vice versa, the laser spot 30 and the powder spot 40 either follow a return trajectory while the substrate 12 rotates, or the laser equipment is returned to its original position (e.g., to the home position at the inner radius 141) and a one-way movement is initiated again while the substrate 12 rotates. This linear movement (either back and forth or in one direction) of the laser head and the powder nozzle, while simultaneously rotating the substrate 12, is repeated over a certain period of time until a deposition layer has been applied to the surface 13 of the substrate 12.

[0121] The powder is thus applied to the surface 13, 13' in the form of powder spots 40 to apply a coating layer. Each area of ​​the surface 13, 13' to be coated is preferably supplied with powder in a single pass; i.e., to obtain a coating layer, the powder is preferably not stacked, or at least the overlap of material should be minimized. The movement followed by the laser head and the relative speeds of the laser head and the disk are thus designed so that ultimately a substantially homogeneous coating layer covers the surface.In other words: By the described supply of the powder, a type of metal-based strand or platelet is deposited on the substrate, and further strands or platelets are deposited next to one another without any significant overlap of the strands or at least a reduced overlap, so that a substantially flat coating layer is formed on the surface 13, 13' of the substrate 12. The . Fig. show a sketch of the metallic cords or platings applied to the surface 50.

[0122] Fig. shows a schematic longitudinal section through a laser system that can be used in laser material deposition for applying one or more coating layers to the surface 13, 13' of a substrate. The laser head (not shown), which emits the laser beam 63, and the nozzle (not shown) carrying the powder to be applied, move together. Typically, the laser beam 63 is confined within a nozzle (not shown), within the open space defined (surrounded) by the nozzle, such that a laser spot 30 is projected onto the surface 13, 13' to be treated. The laser spot is circular. To apply a coating layer for coating the substrate 13, 13', the energy distribution of the laser beam can, for example, be a hat distribution. The powder is in turn applied from a nozzle onto the surface 13, 13' to be treated and forms a powder spot or layer 40 thereon.During operation of the laser system for performing laser cladding, a shielding gas 65 can be delivered to the surface of the substrate, e.g., through a gas nozzle that moves simultaneously with the laser head. The gas nozzle can be the same nozzle as the powder nozzle, or there can be two different nozzles, preferably attached to one another so that they move together on the same trajectory. The shielding gas can be, for example, nitrogen or argon. For example, a gas quantity in the range of about 10 to about 25 liters per minute is applied. The inventors have found that the application of a shielding gas helps prevent oxidation of the surface to be treated after laser coating or laser cladding, and that it contributes to rapid homogenization of the surface.

[0123] The axis 71 of the powder spot 40 is offset or decentered with respect to the axis 73 of the laser spot 30 by 0 to 20% of the diameter of the laser spot, preferably by 2.5 to 15%, particularly preferably by 5 to 12.5%. The area of ​​the laser spot 30 is preferably selected to be larger than the area of ​​the powder spot 40. Preferably, a laser system is selected that emits a laser beam 63 whose diameter of the laser spot 30 (as projected onto the surface 13, 13' of the substrate 12) is between 10% and 40% larger than the diameter of the powder spot 40 applied to the surface 13, 13'. In several experiments, the diameter of the laser spot 30 is about 20% larger than the diameter of the powder spot 40 and the axis 71 of the powder spot 40 is misaligned with respect to the axis 73 of the laser spot 30.Due to the misalignment of the axis 71 of the powder spot 40 with respect to the axis 73 of the laser spot 30, a portion of the laser spot 30 reaches an area on the surface 13 to be treated before the powder (metal spot) 40 is deposited on the surface. Fig. The dashed arrow represents the linear path of the laser beam and powder nozzle. Reference numeral 50 represents a schematic sketch of the powder spot that forms (i.e., forms a kind of string) on ​​the surface 13 of the substrate 12 during the movement of the laser beam, powder nozzle, and substrate. This sketched powder cord 50 is an approximate representation and does not accurately represent an actual track formed by the powder layer, taking into account the linear advance of the laser head and nozzle, as well as the rotation of the substrate. This is carried out over a certain period of time until a complete coating has been applied to the substrate 13.

[0124] The surface 13, 13' is irradiated with a laser beam whose power is preferably in the range between about 6 and about 16 kW, with the diameter of the laser spot being in the range between about 1.5 and about 4 mm. By adjusting the cycle time, an energy density on the surface of the substrate in the range between about 14 kJ / mm 2 and about 50 kJ / mm 2For example, a laser system with an output of 8 kW can be used according to a "top hat" laser energy distribution, a wavelength of 1064 nm, and a laser spot of 2.7 mm. A "top hat" energy distribution delivers essentially constant power across the entire surface of the generated laser spot. The emitted power is a parameter that can be regulated by the user, so the applied laser power can be set as needed—in this example, 8 kW—without exceeding the maximum power provided by the laser system. The inventors have found that a laser with a "top hat" energy distribution operates efficiently because it ensures a homogeneous power distribution across the entire laser spot. This evenly heats the surface hit by the laser beam and enables melting of the delivered powder.Alternatively, a laser with a ring-shaped (donut-shaped) energy distribution can be used, e.g., a laser with a specific maximum power on an outer ring (also called the outer corona) of the laser spot and a specific other power, lower than the maximum, on the core of the laser spot. The powder nozzle is selected so that the diameter of the powder applied to the substrate surface is in a range between 1 and 3.5 mm, with this diameter preferably being smaller than the diameter of the laser spot.

[0125] For typical diameters of conventional brake discs, the substrate 12 preferably rotates at a linear speed in the range of approximately 80 to approximately 240 m / min. The speed of the laser beam depends on the disc dimensions and is therefore adjusted accordingly.

[0126] Fig. schematically shows the shape (outline) of the metal plating 100 (deposited in the form of a "string") formed on the substrate during powder deposition by laser deposition, in which the axis 71 of the powder spot 40 was provided with an offset axis with respect to the axis 73 of the laser beam and the laser spot 30. It has been found that for a deposited layer with a thickness 108 of, for example, 120-150 µm, the difference between the peaks 101 and the valleys 102 on the surface of the layer 100 typically does not exceed 30 µm. The distance 105 between successive layers (deposited powder spots) is typically greater than 500 µm if the diameters of the laser spot and powder spot are greater than 1.5 mm. The laser heating (thermal treatment) that occurs during laser cladding immediately before powder deposition is referred to as 109.

[0127] Laser beam welding can be carried out either perpendicular to the surface to be processed (see e.g. Fig. , in which the powder nozzle is not shown) or with a certain inclination between the surface to be treated and the laser beam and the application of the powder (see e.g. Fig. , in which the powder nozzle is not shown). Tilting can be carried out either by tilting the plane on which the surface to be treated lies, relative to a plane perpendicular to the laser beam (as in Fig. shown) or by tilting the nozzles and the laser head (which move together and assume a fixed relative position to each other) relative to a horizontal plane on which the substrate lies (not shown). Preferably, the tilt angle is between 0 and 30 degrees, where 0° means that the laser beam is directed perpendicularly to the surface to be treated ( Fig. , non-tilted pane). In Fig. the tilt angle α is > 0°, which means that the disc is tilted relative to the laser beam. The tilt of the substrate relative to the laser beam axis does not affect the laser treatment, the removal of graphite, or the application of a coating. The substrate is tilted relative to the laser beam when necessary depending on the circumstances, for example, to prevent the laser head (which may optionally carry a nozzle for transporting the protective or shielding gas to be applied to the braking surface) from colliding with the substrate 12 or with the disc cap 15 and / or to prevent laser beam reflections from traveling back to the laser head. These laser beam reflections could damage the optical elements located in the laser beam path.

[0128] Optionally, a second layer can be applied on top of the first layer, using a similar procedure to the first layer. Fig. The schematic deposition shown is also applicable for the deposition of the second coating layer.

[0129] A first attempt was made with the Fig. The test was carried out on the disc shown. In this test, a single coating was applied using the disclosed laser cladding process. Specifically, the laser cladding process for depositing the coating was carried out using the following parameters: Laser type: Top Hat; circular laser beam; laser beam diameter = 2.7 mm; power = 7.6 kW; speed = 150 m / min; cycle time = 30 s; applied energy density: 39,821.48 J / mm 2; Powder spot diameter = 2.2 mm; Powder flow rate = 90 g / min; Gas type: N2; Carrier gas flow rate = 10 l / min; Shielding gas: N2; Shielding gas flow rate = 20 l / min; Powder type: AISI 316L (particle diameter varies in the range of 20-53 µm); Powder supplier: Höganäs. The axis of the powder cone was offset by 400 µm from the laser beam axis. A microscope image of the brake disc (substrate 12) after application of coating 81 is shown in Fig. shown. In Fig. It can be seen that the overlay layer 81 has a smaller number of holes or bubbles, and the overlay layer 81 is well bonded to the substrate 12. This relatively good performance is achieved by the misalignment of the powder spot and the laser spot during powder deposition. It has been found that heating (thermal treatment) of the surface immediately before receiving the molten powder during deposition helps prevent the occurrence of large numbers of holes or bubbles caused by the explosion of graphite during the deposition of metal-based material. The resulting brake disc thus exhibits improved wear resistance and a better coefficient of friction.

[0130] The brake disc made of Fig. was fitted with a brake disc like in Fig. compared to which the same laser deposition was applied. Laser type: Top Hat; circular laser beam; laser beam diameter = 2.7 mm; power = 7.6 kW; speed = 150 m / min; cycle time = 30 s; applied energy density: 39,821.48 J / mm 2 ; Powder spot diameter = 2.2 mm; Powder flow rate = 90 g / min; Gas type: N2; Carrier gas flow rate = 10 l / min; Shielding gas: N2; Shielding gas flow rate = 20 l / min; Powder type: AISI 316L (particle diameter varies in the range of 20-53 µm); Powder supplier: Höganäs. In this case, however, the axis of the powder cone was aligned with the axis of the laser beam. A microscope image (OM image) of the brake disc (substrate 12) after application of coating 81 under these conditions is shown in Fig. As can be seen, the sample cuts into Fig. very poorly. Many holes are visible in the coating layer 81. There are also holes or bubbles at the interface between the coating layer 81 and the substrate 12, leading to poor integration between the coating layer and the substrate. The holes or bubbles were caused by the explosion of the graphite flakes during powder deposition.

[0131] The poor integration and adhesion of the deposition material to the surface of the substrate when laser beam deposition welding is carried out without axial offset or without decentration (axial offset) is described in the Fig. The cross-sectional views of an AISI 316L coating 100 applied to a gray cast iron substrate without any axial displacement of the powder spot relative to the laser spot axis are shown. Holes left open by the explosion of graphite during laser cladding can be seen.

[0132] A second test was carried out with a brake disc like the one in Fig. A single coating was applied using the following laser deposition technique: Laser type: Top Hat; circular laser beam; laser spot diameter = 3.3 mm; power = 8.25 kW; speed = 120 m / min; cycle time = 30 s; applied energy density: 28,937.26 J / mm 2Powder spot diameter = 2.8 mm; Powder flow rate = 105 g / min; Gas type: N2, carrier gas flow rate = 11 l / min; Shielding gas: N2; Shielding gas flow rate = 8 l / min; Powder type: AISI 316L (stainless steel) (particle diameter varies between 20 and 53 µm). The powder spot axis was offset (decentered) by 400 µm from the laser beam and spot axes. A suitable AISI 316L deposition layer was prepared. Its thickness is 100 µm ± 40 µm. Fig. (Microscope image) shows the resulting coating layer 81 deposited on the surface of the substrate 12. The coating layer 81 has few holes and is relatively well bonded to the substrate 12. This relatively good result is achieved by the misalignment of the powder spot and laser spot during powder coating. Laser cladding with an off-axis offset allows the surface to be heated shortly before the molten metal hits it, reducing the occurrence of holes or bubbles caused by the explosion of the graphite during deposition. The resulting brake disc thus exhibits greater wear resistance and a better coefficient of friction.

[0133] A third test was carried out with a brake disc as used in Fig. The following operating parameters were used: applied laser power = 9000 W, cycle time = 30 s, circular laser spot, laser spot diameter = 3.3 mm and applied energy density = 31567.92 J / mm 2 The laser beam axis was offset by 400 µm from the powder nozzle axis. A suitable coating layer was made of AISI 430L. Its thickness is 100 µm ±40 µm. Fig. shows a microscope image of the resulting coating. The coating has hardly any holes and is well bonded to the substrate.

[0134] A fourth test was carried out to apply a second coating layer on a brake disc surface as in Fig. on which a first coating layer had already been deposited. Laser cladding for the deposition of the first layer was carried out with the following process parameters: laser power = 8750 W, cycle time = 30 s, circular laser spot, laser spot diameter = 3.3 mm, and applied energy density = 30691.04 J / mm 2 The laser beam axis was offset by 400 micrometers from the powder nozzle axis. A suitable first layer was produced from AISI 316L. Its thickness was 100 µm ± 40 µm. Laser cladding for the deposition of the second layer was performed using the following process parameters: laser power = 8850 W, cycle time = 46 s, circular laser spot, laser spot diameter = 3.3 mm, and applied energy density = 47597.41 J / mm 2The laser beam axis was offset by 400 micrometers from the powder nozzle axis. A suitable second coating layer made of AISI 316L+WC was applied over the first coating layer. It has a thickness of 180 ±40 µm. Fig. shows a cross-sectional view of the substrate and the two applied coatings. Both are well integrated (the first with the substrate, the second with the first), and hardly any unwanted holes or bubbles are visible.

[0135] A fifth test was carried out to apply a second coating to a surface of a brake disc as in Fig. on which a first coating had already been deposited. Laser cladding for the deposition of the first layer was carried out with the following process parameters: laser power = 9000 W, cycle time = 30 s, circular laser spot, laser spot diameter = 3.3 mm, and applied energy density = 31567.92 J / mm2 The laser beam axis was offset by 400 micrometers from the powder nozzle axis. A suitable first coating was produced from AISI 430L. Its thickness was 100 µm ± 40 µm. Laser cladding to deposit the second layer was performed using the following process parameters: applied laser power = 9 kW, cycle time = 46 s, circular laser spot, laser spot diameter = 3.3 mm, and applied energy density = 48404.15 J / mm 2 The laser beam axis was offset from the powder nozzle axis. A suitable second coating of AISI 430L+TiC with a thickness of 180 ±40 µm was achieved. Fig. shows a cross-sectional view of the substrate and the two applied coating layers. Here, too, both layers are well integrated (the first with the substrate, the second with the first) and exhibit hardly any unwanted holes or bubbles.

[0136] A sixth test was carried out to test a second coating on a brake disc as in Fig. to which a first coating had already been applied. Laser cladding for the deposition of the first layer was carried out with the following process parameters: laser power = 11,500 W, cycle time = 34 s, circular laser spot, laser spot diameter = 3.3 mm, and applied energy density = 45,715.03 J / mm 2 The laser beam axis was offset by 400 micrometers from the powder nozzle axis. A suitable first coating layer was produced from AISI 430L. Its thickness was 100 µm ± 40 µm. Laser cladding for the deposition of the second coating was performed using the following process parameters: power = 11,500 W, cycle time = 34 s, circular laser spot, laser spot diameter = 3.3 mm, and applied energy density = 45,715.03 J / mm 2A suitable second coating of AISI 430L+TiCFeCr with a thickness of 180 ±40 µm was obtained. Fig. shows a cross-sectional view of the substrate and the two applied coating layers. Here, too, both layers are well integrated (the first with the substrate, the second with the first), and the presence of unwanted holes or bubbles is relatively rare.

[0137] Before applying laser cladding to deposit one or more coating layers on the brake disc substrate, the surface of the substrate 12 can be subjected to laser cleaning. An example of laser cleaning is shown in the Fig. To apply the laser cleaning radiation to the surface 13, 13', a laser beam head performs a radial movement along the radius of the substrate, while the sub-machine moves in a similar manner as in the Fig. 2A and Fig. 2B. However, in this case, there is no powder deposition on the surface of the substrate. In other words, laser cleaning can be applied to the original, untreated surface of the substrate. The surface 13, 13' is cleaned by this laser treatment. The laser radiation is emitted by a laser processing head (not shown), which, for example, carries a nozzle through which the laser radiation is emitted in a manner similar to laser cladding (however, in this case, no powder is supplied).

[0138] The surface 13, 13' is irradiated with a laser beam having a power in the range between approximately 2 and approximately 12 kW with a laser spot diameter in the range between approximately 1.5 and approximately 4 mm. By adjusting the cycle time, an energy density on the surface of the substrate is achieved that is between approximately 14 kJ / mm 2 and about 45 kJ / mm 2For example, a laser system with an output of 8 kW can be used according to a "top hat" laser energy distribution, a wavelength of 1064 nm, and a laser spot of 2.7 mm. A "top hat" energy distribution delivers essentially constant power across the entire surface of the generated laser spot. The emitted power is a parameter that can be regulated by the user, so the applied laser power, in this example 8 kW, can be set without exceeding the maximum power provided by the laser system. The inventors have found that a laser with a "top hat" energy distribution operates efficiently because it ensures a homogeneous power distribution across the entire laser spot. It therefore heats the surface encountered by the laser beam evenly. The inventors have found that such a homogeneous power distribution contributes to cleaning efficiency.Alternatively, a laser with a ring-shaped (donut-like) energy distribution can be used, e.g., a laser with a certain maximum power on an outer ring (also called outer corona) of the laser spot and a certain other power, lower than the maximum, on the core of the laser spot.

[0139] During laser cleaning, the laser beam is moved or scanned to create a specific pattern on the surface 13, 13' to be exposed to the laser radiation. For example, the laser beam can be repeatedly scanned according to a scanning pattern, creating an effective spot that is displaced relative to the surface to be treated. Alternatively, the laser beam can be moved (scanned), defining a specific path. Fig. The laser beam is moved, for example, along a radial axis of the surface 13, 13' to be treated on a linear path. The laser system that emits the laser beam is conventional and not the subject of the present invention. The same or a different laser system that is also used for laser cladding can be used for laser cleaning.

[0140] In this way, lamellar graphite is removed from the surface 13, 13' of the substrate 12 before an overlay layer is applied thereto. In particular, lamellar graphite is reduced on the surface of the substrate and within a maximum depth of about 80 µm. Under these conditions, a typical brake disc substrate with an inner diameter between about 160 and about 230 mm and an outer diameter between about 270 and about 410 mm requires a graphite removal cleaning process lasting between about 20 and about 55 seconds. This cleaning process has been found to enable the evaporation of 50 to 100% of the graphite flakes present on the surface, particularly within a thickness of 30 µm from the surface.

[0141] Although not shown, during operation of the laser cladding device or laser system for applying a laser beam to the surface of the substrate to remove graphite therefrom, a shielding gas may be released onto the surface 13, 13' of the substrate 12, as in laser cladding. The same or similar shielding gases and application parameters used in laser cladding can also be used in laser cleaning. The application of a shielding gas helps prevent oxidation of the surface to be treated after cleaning and contributes to the rapid homogenization of the surface, thereby improving overall cleaning.

[0142] Several experiments were conducted to evaluate the application of the presented laser cleaning.

[0143] The Fig. correspond to a seventh test. They show in particular the surfaces 13 and 13' of the brake disc from Fig. After laser treatment to remove graphite. The applied laser cleaning had the following parameters using a continuous laser: applied laser radiation power of 6 kW (top-hat distribution), wavelength of 1064 nm, circular laser spot, laser spot diameter of 2.7 mm, cycle time = 30 s, linear speed of the laser beam in the range of 100–200 mm / minute (to keep the linear rotation speed of the disk constant), equivalent linear speed of the rotating substrate of 170 m / minute, applied energy density = 31,438 J / mm 2 and use of nitrogen (N2) as a protective gas. Comparing the treated surfaces 13, 13' of the respective Fig. with the untreated surface 13' (substrate before laser cleaning) of the Fig. , it can be seen macroscopically that the surface 13, 13' has a matte appearance after laser cleaning, while the surface of the untreated substrate is much brighter. The surface of the brake disc was affected by the laser treatment in that the laser cleaning leads to a significant reduction of the surface graphite, which is evaporated. By evaporating (removing) graphite from the surface of the substrate, a better contact surface is achieved for the subsequent bond between the treated substrate (with a smaller amount of graphite) and a metal-based coating to be applied to the treated substrate of the cutting disc. Fig. show detailed pictures of the brake disc from Fig. after applying laser-based cleaning.

[0144] The Fig. show SEM images (scanning electron microscopy) (magnification x500) of the surface 13' of the substrate 12 from Fig. after laser cleaning treatment of this disclosure. The images were taken using different SEM settings. In both images, the voids created after the graphite flakes were extracted (evaporated) are clearly visible. Fig. was captured using an SEM configuration that highlights different materials. Specifically, the lighter parts of the image represent the substrate (cast iron), while the darker parts of the image show traces of graphite 36 on the surface. Fig. was captured using an SEM configuration that allows the surface relief to be seen (a certain depth is visible). In particular, the 37 voids shown on the surface are due to the missing graphite lamellae. This means that the substrate surface, which should have been essentially flat, now has a certain depth (holes) created by graphite evaporation. These holes increase the contact area of ​​the substrate, which will receive the deposited material in the subsequent laser phase (laser cladding).

[0145] The Fig. , which is still on the seventh attempt ( Fig. ) show microscopic images of a cross-section of the substrate of the wafer after treatment with the disclosed laser cleaning. Figures 15A and 15B differ in the image resolution, which is Fig. lowest and in Fig. is highest. The lower part of each image (the light gray part) represents the substrate 12, in which graphite lamellae 51 are present (in dark gray). It should be noted that it is desirable not to alter the structure of the substrate (except in its most superficial part, where it is desirable to evaporate the graphite) and therefore to preserve the graphite naturally present in the substrate. The elongated shape of the graphite is clearly visible and forms branches. In the Fig. In particular, holes 52 can be seen on the surface of the substrate, corresponding to the graphite lamellae evaporated during laser cleaning. These holes 52 enable the deposition and integration of the subsequently applied metallic coating layer with the substrate. Fig. shows a microscope image of a cross-section of the same substrate 12, on which a metallic coating was applied after laser cleaning as described above. The image resolution of Fig. is twice as high as that of Fig. It can be seen that the holes 52, which were created by the removal of the graphite on the surface and in its vicinity, were filled with the coating layer 81 53. Thanks to the increase in the contact area of ​​the substrate through the typically branched holes, which remained open due to the evaporation of the graphite flakes, the amount of deposited material that fills the holes and settles increases, thereby increasing the adhesion between the coating layer and the substrate. The minimally affected thickness of the substrate surface below the deposited coating is Fig. estimated at approximately 40 µm. In other words, a homogeneous heat-affected zone (HAZ) is guaranteed not to exceed a thickness of approximately 40 µm.

[0146] The positive effect of the application of a protective gas in the laser cleaning phase (laser cleaning) can be observed in an eighth experiment, which was carried out in the Fig. They show a brake disc as shown in the Fig. , to which cleaning was applied as follows: applied laser power = 2000 W, cycle time = 30 s, circular laser spot, laser spot diameter = 1.55 mm and applied energy density = 31797.87 J / mm 2 . The disc in Fig. was not treated with protective gas. In contrast, the disc was Fig. treated with N2. As can be seen, the shielding gas prevents oxidation of the substrate surface.

[0147] A ninth attempt was made with the disc from Fig. carried out. Fig. shows a photo of a grey cast iron brake disc with an inner diameter of 220 mm and an outer diameter of 350 mm before the application of laser cleaning or laser cladding. Fig. show SEM images (magnification x30 or x100) of the untreated surface of the substrate (surface 13' of the Fig. The disc shown shows clear machining marks, indicating that no laser cleaning was applied. To remove graphite from the surface of the disc, the following laser treatment was performed using a continuous laser: applied laser power = 5000 W, cycle time = 30 s, linear rotation speed of the disc = 170 m / min, circular laser spot, wavelength = 1064 nm, laser spot diameter = 3.3 mm, and applied energy density = 17535.73 J / mm 2 The surfaces 13 and 13' of the brake disc after laser treatment to remove graphite are shown in the Fig. shown. The Fig. show SEM images (magnification x30 and x100) of the substrate surface after the exemplary laser cleaning. Fig. Many holes can be seen that have been left open by vapor-deposited graphite lamellae (empty spaces 37). Some machining traces 35 are also visible. On the untreated surface in Fig. The processing marks 35 are clearly visible, which proves that the disc has not been laser treated. In this case, graphite (i.e., graphite flakes) is present on the surface and / or near the surface of the substrate. Fig. the processing marks 35 are much less clearly visible, which is an indication that the wafer has undergone laser treatment. In this case, after the laser treatment, in which part of the graphite flakes was detached or evaporated from the substrate, voids remain, caused by the missing graphite flakes. The inventors have observed that these voids (empty areas or void zones) on or near the surface of the substrate increase the effective surface area on which an overlay layer can be deposited and thus contribute to the adhesion of the overlay layer to be subsequently deposited. In other words, a metal-based coating fills the voids left behind by the missing graphite.

[0148] A tenth and an eleventh test were carried out with a brake disc like the one in Fig. shown.

[0149] In the tenth experiment, the following laser treatment was performed with a continuous laser: applied laser power = 3000 W, cycle time = 30 s, linear rotation speed of the disc = 170 m / min, circular laser spot, wavelength = 1064 nm, diameter of the laser spot = 3.3 mm and applied energy density = 10500 J / mm 2 . Fig. shows an SEM image (magnification x100) of one of the treated surfaces of the disk. In this image, only a few holes are visible, left open by evaporated graphite lamellae (empty spaces 37). The processing marks 35 are clearly visible.

[0150] In the eleventh experiment, the following laser treatment was performed with a continuous laser: applied laser power = 7000 W, cycle time = 30 s, linear rotation speed of the disc = 170 m / min, circular laser spot, wavelength = 1064 nm, laser spot diameter = 3.3 mm and applied energy density = 24552.83 J / mm 2. Fig. shows an SEM image (magnification x100) of one of the treated surfaces of the disk. This image shows numerous holes left open by evaporated graphite lamellae (voids 37). Furthermore, the processing marks 35 are barely visible.

[0151] Comparing the SEM images of the Fig. , you can see the optimal performance of laser cleaning of Fig. (applied power of 7 kW), in which many holes can be seen that have remained open due to evaporated graphite lamellae. Furthermore, hardly any machining traces are visible. In contrast, laser cleaning in Fig. (applied power of 3 kW) is poor, and only a few holes left by evaporated graphite flakes are visible. The machining marks are clearly visible.

[0152] Further tests were conducted to compare the performance of brake discs provided with a coating but where no laser cleaning was applied to the surface before the coating was applied (first test, Fig. , and with the same brake discs, which have the same coating, but where laser cleaning was applied to the surface before the coating was applied. In a test 12th, a brake disc as in Fig. (Gray cast iron brake disc, inner diameter of the disc 177 mm, outer diameter of the disc 306 mm) treated with laser cleaning according to the seventh experiment (parameters using a continuous laser: applied laser radiation power of 6 kW (top-hat distribution), wavelength of 1064 nm, circular laser spot, laser spot diameter of 2.7 mm, cycle time = 30 s, linear speed of the laser beam in the range of 100-200 mm / minute, equivalent linear speed of the rotating substrate of 170 m / minute, applied energy density = 31438 J / mm 2 and using nitrogen (N2) as a shielding gas). Subsequently, a deposition layer was applied after the laser deposition of the first test (laser type = top hat; circular laser beam; laser beam diameter = 2.7 mm; power = 7.6 kW; speed = 150 m / min; cycle time = 30 s; applied energy density: 39,821.48 J / mm 2Powder spot diameter = 2.2 mm; Powder flow rate = 90 g / min; Gas type: N2; Carrier gas flow rate = 10 l / min; Shielding gas: N2; Shielding gas flow rate = 20 l / min; Powder type: AISI 316L (particle diameter varies in the range of 20-53 µm); Powder supplier: Höganäs). The axis of the powder cone was offset, or decentered, by 400 µm from the laser beam axis. Fig. shows a microscope image of the brake disc (substrate 12) after application of coating 81. Fig. shows a photograph of the surface of the brake disc from Fig. after applying the first coat. Fig. shows a zoomed section of the photograph by Fig. Macroscopically, the essentially flat coating layer is visible. The flatness and flawlessness (no holes or cracks) of the coating layer proves its quality and correct integration with the substrate. A suitable first coating was made of AISI 316L. Its thickness is 100 µm ±40 µm. Fig. show microscope images of the brake disc after applying the described coating. Fig. shows an excerpt from Fig. It can be seen that the deposited layer 81 is free of holes or bubbles and that the deposited layer 81 is well bonded to the substrate 12. This good performance is achieved by the combination of pre-cleaning and the offset of the powder spot and laser spot during powder deposition. Holes created by the evaporation of graphite during the laser cleaning pretreatment improve the contact area and are filled with metal-based material during deposition. Heating the surface immediately before receiving the molten powder during deposition also helps prevent the occurrence of additional holes or bubbles caused by the explosion of additional graphite. Fig. is the interface between the coating layer 81 and the substrate 12 made of Fig. Enlarged image. It can be seen that the area of ​​the substrate thermally affected by the laser treatment has a maximum thickness of 47 µm (worst case). The resulting brake disc thus exhibits improved wear resistance and a better coefficient of friction.

[0153] The result of Experiment 12 can also be compared with an experiment conducted with a brake disc with the same properties (material and dimensions), the same laser cleaning (applied laser radiation power of 6 kW (top-hat distribution), wavelength of 1064 nm, circular laser spot, laser spot diameter of 2.7 mm, cycle time = 30 s, linear speed of the laser beam in the range of 100-200 mm / minute, equivalent linear speed of the rotating substrate of 170 m / minute, applied energy density = 31438 J / mm 2and use of nitrogen (N2) as shielding gas) and the same laser deposition (laser type = Top Hat; circular laser spot; laser spot diameter = 2.7 mm; power = 7.6 kW; speed = 150 m / min; cycle time = 30 s; applied energy density: 39,821.48 J / mm 2 ; Powder spot diameter = 2.2 mm; Powder flow = 90 g / min; Gas type: N2; Carrier gas flow = 10 l / min; Shielding gas: N2; Shielding gas flow = 20 l / min; Powder type: AISI 316L (particle diameter varies in the range of 20-53 µm); Powder supplier: Höganäs), however, during laser cladding, the powder spot axis was aligned with the laser beam and spot axis. The result is shown in Fig. shown. Fig. shows a relatively good performance, although not as good as that of Fig. . Pre-cleaning allows a significant reduction of holes or bubbles in the coating layer 81 compared to a sample without pre-cleaning ( Fig. . It also reduces the likelihood of graphite evaporation during the deposition of the metallic coating. Fig. However, it is observed that the application of powder deposition on the surface without an immediately preceding laser preheating (no axis shift) causes an undesirable displacement of the deposited material on the surface of the substrate, due to the stresses to which the material just deposited on the substrate is subjected, which hinders the integration and adhesion of the material with the substrate and provokes the explosion of the graphite still present in the substrate (sudden evaporation), causing some holes in the deposited layer and poor contact between the deposited layer and the substrate. The samples in the Fig. perform better than the sample in Fig. . Fig. shows the best performance.

[0154] The Fig. show more pictures of the sample from Fig. (Brake disc that was cleaned with a laser and then coated with a laser deposition, but without misalignment between the axis of the powder spot and the axis of the laser beam and the laser spot). Due to the cleaning before laser deposition, essentially no holes are observed in the deposition layer 81, so good performance of the coated brake disc can be expected. Fig. However, certain changes in the coating layer 81 can be seen, which show that the material is not well bonded to itself in certain areas 95. In the Fig. Certain defects can be seen at the interface between the coating layer 81 and the substrate 12, indicating that the material used to coat the substrate is not well bonded to the substrate, resulting in poor contact between the coating layer and the substrate. These defects are due to the stress on the material during deposition, which did not involve any axial displacement.

[0155] A test was carried out 13th with a brake disc as in Fig. This attempt can be repeated with the second attempt ( Fig. ). Before applying a coating layer, the same laser cladding process as in the second test was used (laser type = Top Hat; circular laser beam; laser spot diameter = 3.3 mm; power = 8.25 kW; speed = 120 m / min; cycle time = 30 s; applied energy density: 28,937.26 J / mm 2; Powder spot diameter = 2.8 mm; Powder throughput = 105 g / min; Gas type: N2; Carrier gas flow = 11 l / min; Shielding gas: N2; Shielding gas flow = 8 l / min; Powder type: AISI 316L (stainless steel) (particle diameter varies between 20-53 µm)). To obtain an AISI 316L coating with a thickness of 100 µm ± 40 µm, laser cleaning was previously applied to the original brake disc (laser type: Top Hat; circular laser beam; laser beam diameter = 3.3 mm; power = 5 kW; speed = 170 m / min; cycle time = 30 s; gas type: N2; shielding gas flow rate = 15 l / min; energy density of the laser beam used = 17,537.73 J / mm 2 ). The resulting sample is in Fig. , which demonstrates optimal performance. The deposition layer 81 is free of holes and well bonded to the substrate 12. This optimization is achieved through the combination of pre-cleaning and offsetting of the powder spot and laser spot during powder deposition. Pre-cleaning causes evaporation of the graphite flakes near the substrate surface, leaving holes that can be filled with the material to be deposited during laser deposition. Off-axis laser deposition allows the surface to be heated shortly before the molten metal is absorbed, preventing or at least reducing the occurrence of additional holes or bubbles due to the explosion of additional graphite. The resulting brake disc thus exhibits improved wear resistance and a better coefficient of friction.

[0156] A 14th attempt was made with a brake disc like the one in Fig. In particular, test 14 was carried out on a brake disc to which test 12 had been applied (cleaned after laser cleaning and coated with a first layer, see Fig. ). A second layer was then applied to the first layer by laser cladding with the following parameters: Laser type = Top Hat; circular laser beam; laser beam diameter = 2.7 mm; power = 7.75 kW; speed = 80 m / min; gas type: N2; carrier gas flow rate = 15 l / min; shielding gas flow rate = 20 l / min; powder spot diameter = 2.2 mm; powder flow rate = 90 g / min; cycle time = 40 s; applied energy density: 54,143.25 J / mm 2; The powder type is a mixture of AISI 316L and WC tungsten carbides (20-53 µm); powder supplier: Höganäs for AISI 316L and C&M for WC. The laser beam axis was offset by 400 micrometers from the powder nozzle axis. A suitable second coating was obtained from a mixture of AISI 316L and WC. It has a thickness of 180 µm ±20 µm. Fig. shows a photo of the brake disc from Fig. after applying the second coating. Fig. shows an enlarged section of the photo of Fig. Macroscopically, the essentially flat coating layer can be seen. The flatness and flawlessness (no holes or cracks) of the coating layer proves its quality and correct integration with the first coating layer. Fig. show SEM images of two exemplary cross-sections of the substrate of the disc from Fig. (on which two layers were applied). The Fig. show images taken with a light microscope of the same substrate of the disc from Fig. . The dissolution of the Fig. is five times lower than the resolution of the Fig. . In the Fig. The substrate 12 occupies most of the image. Graphite flakes 51 are present in the substrate 12 (dark gray in color). This means that the structure of the substrate has been correctly preserved after cleaning and coating. It can also be observed that the first deposition layer 81 is essentially free of graphite. This is due to the fact that the laser cleaning applied initially, as well as the additional laser heating performed immediately before the deposition of the metal-based powder by shifting the axis of the powder cone with respect to the axis of the laser beam during the first laser deposition or laser deposition welding, reduced the amount of graphite on the surface of the substrate. In the second deposition layer 82, the white spots represent the carbide present in this layer. The gray color in the first and second deposition layers 81, 82 represents the metal base of the layer.It can be seen that both layers are essentially free of graphite.

[0157] In a 15th experiment, the results of the 14th experiment (depositing the second layer using misaligned axes) were compared with the deposition of a second layer on a similar brake disc (after laser cleaning and the first layer from the 12th experiment). As in the 14th experiment, laser cladding to deposit the second layer was carried out with the following process parameters: Laser type: Top Hat; circular laser beam; laser beam diameter = 2.7 mm; power = 7.75 kW; speed = 80 m / min; gas type: N2; carrier gas flow rate = 15 l / min; shielding gas flow rate = 20 l / min; powder spot diameter = 2.2 mm; powder flow rate = 90 g / min; cycle time = 40 s; applied energy density: 54,143.25 J / mm 2; The powder type is a mixture of AISI 316L and WC tungsten carbides (20-53 µm); Powder supplier: Höganäs for AISI 316L and C&M for WC. In this case, the laser beam axis was not misaligned with the powder nozzle axis. A second coating was obtained from a mixture of AISI 316L and WC. Fig. shows a picture of the sample from the Fig. to which this second coating 82 was applied. At the interface between the two layers 81 and 82, certain defects 98 can be seen, indicating that the material of the second coating layer 82 cannot bond well with the first coating layer 81. These defects are due to the stresses to which the material was exposed during deposition or cladding.

[0158] In this text, the terms "comprises" and "includes" and their derivatives (such as "comprises", "includes", etc.) are not to be understood in an exclusive sense, i.e. these terms are not to be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.

[0159] The term "about," when used in the context of the present invention before and referring to a number, is to be understood as meaning any value that lies within the range defined by the number ±5%, preferably within a range defined by the number ±2%. For example, the term "about 10" is to be understood as "within the range of 9.5 to 10.5," preferably "within the range of 9.8 to 10.2."

[0160] The invention is of course not limited to the specific embodiment(s) described herein, but also includes all variations that a person skilled in the art may consider within the general scope of the invention defined in the claims (e.g. with regard to the choice of materials, dimensions, components, configuration, etc.). QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 24382549.4

[0001] US 2014 / 0262642A1

[0008] DE 102010048075A1

[0008] DE 102011056307A1

[0008]

Claims

[1] Brake disc manufacturing device, designed to produce a brake disc starting from a substrate (12) of a brake disc, wherein the substrate (12) is made of a graphite-containing metallic material, in particular of grey cast iron, and the substrate (12) defines a surface (13, 13'), comprising: a laser deposition device arranged to form a metal-based deposition layer on the surface (13, 13') of the substrate (12) by applying laser deposition, with a powder feed including a powder nozzle and with a laser source arranged to direct a laser beam onto the surface such that powder is applied to the surface (13, 13') while a laser beam is irradiated onto the surface (13, 13'), wherein the powder nozzle is coupled to the laser head in order to move the supplied powder and the laser beam together over the surface to be coated when the laser head moves, wherein the laser application device is configured such that the diameter of a laser spot applied to the surface by the laser beam is larger than the diameter of a powder spot applied to the surface from the powder nozzle, and such that the axis of the laser spot applied to the surface is offset with respect to the axis of the powder spot applied to the surface. [2] Brake disc manufacturing device according to claim 1, wherein the laser deposition device and / or a cleaning device is / are arranged to remove graphite from the surface (13, 13') of the substrate (12) by applying a cleaning in which the surface is irradiated with a laser beam prior to the application of a laser deposition for depositing a metal-based coating on the surface (13, 13') of the substrate (12). [3] Brake disc manufacturing device according to one of the claims 1 to 2, comprising a rotation device arranged to rotate the substrate (12) of the brake disc during the application of the cleaning and / or during the deposition of a metal-based coating, while the laser head from which the laser beam is emitted moves linearly on the surface (13) of the substrate (12), wherein the linear movement follows a radial trajectory on the surface of the substrate. [4] Brake disc manufacturing device according to claim 3, wherein the rotation device is arranged to rotate the brake disc at a linear speed in the range of 80 to 240 m / min, preferably in the range of 120 to 200 m / min. [5] Brake disc manufacturing device according to one of claims 1 to 4, in which the application device is arranged so that the axis of the powder spot is offset with respect to the axis of the laser spot by an amount between 0 and 20% of the diameter of the laser spot, preferably between 2.5 and 20% thereof, more preferably between 2.5 and 15% thereof, and even more preferably between 5 and 12.5% ​​thereof. [6] Brake disc manufacturing device according to one of claims 1 to 5, wherein, during laser deposition for depositing a metal-based coating on the surface of the substrate, the deposition device is arranged so that the diameter of the laser spot is between 10 and 40% larger than the diameter of the powder spot. [7] Brake disc manufacturing device according to one of claims 1 to 6, in which, during laser deposition welding for depositing a metal-based coating, the deposition device is arranged so that the power of the laser beam is in a range between 6 kW and 16 kW, preferably between 7 kW and 12 kW and particularly preferably between 7.5 and 10 kW and the deposition device is arranged to set the cycle time preferably to between 20 and 55 seconds. [8] Brake disc manufacturing device according to one of claims 1 to 7, which is arranged to set the diameter of the laser spot used in the laser beam build-up welding to a range between 1.5 and 4 mm, preferably between 2 and 4 mm, more preferably between 2.2 and 3.7 mm and more preferably between 2.5 and 3.5 mm; and to set the diameter of the powder spot to a range between 1 and 3.5 mm, preferably between 1 and 2.5 mm and more preferably between 1 and 2 mm. [9] Brake disc manufacturing device according to one of claims 1 to 8, which is arranged to achieve an energy density on the surface of the substrate in the range between 14 kJ / mm 2 and 50 kJ / mm 2 to provide. [10] Brake disc manufacturing device according to one of claims 1 to 8, which is arranged to irradiate the surface with a laser beam emitted with a power in the range between 2 and 12 kW, the diameter of the laser spot being in the range between 1.5 and 4 mm, during the application of the cleaning. [11] Brake disc manufacturing device according to claim 10, which is arranged to irradiate the surface during cleaning with a laser which is arranged to emit with a power in the range between 4 and 8 kW, preferably between 5 and 7 kW. [12] Brake disc manufacturing device according to one of claims 10 to 11, which is arranged to adjust the diameter of the laser spot used for graphite removal during cleaning to a range between 2 and 4 mm, preferably between 2.2 and 3.7 mm and more preferably between 2.5 and 3.5 mm. [13] Brake disc manufacturing device according to one of claims 10 to 12, which is arranged to apply an energy density on the surface of the substrate in the range between 10 and 45 kJ / mm 2 to provide. [14] Brake disc manufacturing device according to one of the claims 1 to 13, comprising a gas supply which is arranged to direct a protective gas onto the surface of the substrate during cleaning and / or during deposition of a metal-based coating while the surface is irradiated with the laser beam, wherein the protective gas is nitrogen or argon. [15] Brake disc manufacturing device according to one of claims 1 to 14, which is designed to deposit a single layer during laser deposition welding, which layer preferably consists of a mixture of a metal and a carbide, wherein the metal is preferably steel and the carbide is preferably tungsten carbide or titanium carbide. [16] Brake disc manufacturing apparatus according to one of claims 1 to 15, which is further arranged to provide a second laser deposition to apply a second metal-based deposition layer to the first metal-based deposition layer. [17] Brake disc manufacturing device according to claim 16, which is designed to set the power of the laser beam in a range between 7 and 18 kW, preferably between 7.5 and 14 kW and particularly preferably between 7.5 and 12 kW during the laser deposition welding for depositing the second metal-based coating layer, and to set the cycle time preferably between 20 and 55 seconds. [18] Brake disc manufacturing device according to claim 16 or 17, which is designed to have an energy density on the surface of the substrate in the range between 25 and 70 kJ / mm during the second laser deposition for depositing the second metal-based coating layer2 to provide. [19] Brake disc manufacturing device according to one of claims 16 to 18, which is arranged to apply a layer of metal, preferably steel, during the first laser deposition welding and to apply a layer of a mixture of a metal and a carbide, wherein the metal is preferably steel and the carbide is preferably tungsten carbide or titanium carbide, in the second laser deposition welding. [20] Use of the brake disc manufacturing device according to one of the claims 1 to 19, wherein during the laser deposition welding a single layer is deposited, which preferably consists of a mixture of a metal and a carbide, wherein the metal is preferably steel and the carbide is preferably tungsten carbide or titanium carbide. [21] Use of the brake disc manufacturing apparatus according to any one of claims 1 to 19, wherein a first metal-based coating layer is provided by laser deposition welding and further a second laser deposition welding is provided to apply a second metal-based coating layer to the first metal-based coating layer. [22] Use according to claim 21, wherein the laser system for deposition welding for depositing the second metal-based coating layer is configured such that the power of the laser beam is in a range between 7 and 18 kW, preferably between 7.5 and 14 kW and more preferably between 7.5 and 12 kW; and the cycle time is selected between 20 and 55 seconds. [23] Use according to claim 21 or 22, wherein the laser system for the build-up welding is configured to operate during the deposition of the second metal-based build-up layer such that the energy density on the surface of the substrate is in the range between 25 and 70 kJ / mm 2 lies. [24] Use according to one of claims 22 to 23, in which the laser system for deposition welding is configured such that a layer of metal, preferably steel, is applied during the first laser deposition welding and a layer of a mixture of a metal and a carbide, wherein the metal is preferably steel and the carbide is preferably tungsten carbide or titanium carbide, is applied during the second laser deposition welding. [25] Brake disc produced with the brake disc manufacturing device according to one of the claims 1 to 19 and / or using the device according to one of the claims 20 to 24, wherein the substrate is preferably made of grey cast iron.

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