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 cleaning system arranged to remove graphite from the surface (13, 13') of the substrate (12) by applying a cleaning by irradiating the surface with a laser beam emitted with a power between 2 and 12 kW, wherein the diameter of the laser spot is between 1.5 and 4 mm; and a laser deposition welding system arranged to apply a metal-based coating layer to the surface (13, 13') of the substrate (12) from which graphite has been removed by laser deposition welding, wherein the laser cleaning system and the laser cladding system contain one or more laser heads.

Description

[0001] This application claims priority from European patent application EP24382550.2, filed on May 23, 2024. The full disclosure of European patent application EP24382550.2 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 the manufacture of such brake discs. The disclosure is particularly advantageous for manufacture using an energy beam, e.g., a laser energy beam. 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 typically 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 a 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 matter 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. During or shortly before the coating is applied, the powder to be applied is melted by the application of heat, bonding with the base material of the brake disc and forming a surface layer. The powder can be applied to the friction surfaces using a laser deposition process, for example. 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. For example, the high power of the laser beam used in laser cladding to coat a cast iron part with a powdered metallic material vaporizes the graphite flakes contained in the cast iron, particularly on the surface, 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 say 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 a brake disc manufacturing device so that the amount of graphite in the base material of the brake disc, especially near the surface, can be reduced, allowing a coating layer to be applied thereto by laser cladding that offers higher performance than conventional brake discs. It is therefore desirable to obtain a brake disc with improved adhesion between the coating layer and the base material of the brake disc, thereby increasing the reliability of the wear layer. DESCRIPTION OF THE INVENTION

[0011] The brake disc manufacturing device, its use and the brake disc thus obtained aim to remedy the deficiencies of the state of the art in the production of brake discs and the available brake discs.

[0012] The objective of the present disclosure is to obtain 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 provided from a substrate, base material, or base body (hereinafter referred to as the substrate) made of a graphite-containing metallic material. The substrate may, for example, be cast or forged 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, for example, but not limiting, for gray cast iron. The substrate is a rotatable element having two substantially flat surfaces facing each other. These surfaces are typically circular, annular surfaces.

[0014] Once the brake disc has been completely manufactured, 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. The cladding process can then be repeated on 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 can be applied using laser cladding with high power and high material absorption. Powder is applied to the surface to be coated while a laser beam is shined onto the surface to be coated by a laser head that is moved along the surface to be treated. The radiation from the laser beam is focused onto the surface and creates a molten pool on the surface when the powder is 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 repeating this deposition over the entire surface to be treated, the substrate is essentially covered with a coating layer. The coated surface could be the friction surface of a brake disc.

[0015] A first aspect of the disclosure relates to a brake disc manufacturing apparatus for manufacturing a brake disc, comprising: Providing a brake disc substrate, the substrate being made of a graphite-containing metallic material and defining a surface; Removing graphite from the surface of the substrate by cleaning, in which the surface is irradiated with a laser beam emitted at a power in the range between about 2 and about 12 kW, the diameter of the laser spot being in the range between about 1.5 and about 4 mm; Applying a metal-based coating layer to the surface of the substrate from which graphite has been removed by laser deposition welding or laser cladding.

[0016] In the context of the present disclosure, a laser spot or laser point (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.

[0017] The substrate is preferably made of grey cast iron.

[0018] The graphite contained in the substrate is usually lamellar graphite, which occurs, among other things, in grey cast iron.

[0019] The at least one coating or coating layer is 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, for example 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 of two coating layers. In some embodiments, the at least one coating layer is a multi-layer comprising at least one metal coating layer 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.

[0020] 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.

[0021] 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.

[0022] 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 a metal-based powder and a 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's radiation 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 take on other shapes, including irregular particles, in which case the former values ​​refer to the largest dimension of the particle). Preferably, the size of the powder particles varies from about 10 to about 63 µm, more preferably from about 20 to 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.

[0023] 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.

[0024] Before applying an overlay layer to a substrate surface, graphite is removed from the substrate, in particular from the surface on which the overlay layer is to be applied, or more generally from the surface of the substrate and from the part of the substrate located below and close to this surface. In particular, the graphite is 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 present on the surface of the substrate, are also removed.

[0025] During both the cleaning and laser cladding phases, the energy density that must be applied to the substrate surface depends on several parameters, such as the laser beam power, the area of ​​the laser spot to be applied to the surface, and the required cycle time (the time required to complete the surface cleaning process). The energy density of a laser beam follows the equation: Energy density = energy / area of ​​the laser spot = (power × cycle time) / area of ​​the laser spot.

[0026] During cleaning, the energy density must be high enough to remove the flake graphite from the substrate surface while essentially preserving the integrity of the substrate below the surface. In laser cladding, the energy density must be sufficient to allow the surface to which the powder is to be applied to be thermally treated and the powder to be melted to apply a coating.

[0027] The power of the laser beam used in cleaning may be in a range between 2 and about 12 kilowatts (kW), preferably between about 4 kW and about 8 kW, inclusive, and more preferably between about 5 and about 7 kW, inclusive.

[0028] A laser system is used that generates a circular laser spot. Preferred values ​​for the laser spot area are in the range between approximately 1.75 and approximately 12.50 mm 2, which corresponds to laser spot diameters 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 a suitable cycle time and laser beam power, the graphite is correctly removed from the substrate.

[0029] 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.

[0030] 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 is produced per unit of time (e.g., working day). To optimize the production of finished brake discs, the cycle time for removing graphite from the substrate surface by laser cleaning is preferably selected to match the cycle time for laser cladding to deposit a metal-based coating onto the substrate surface 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.

[0031] In some embodiments, the cycle time is selected to be in the range between 20 and 55 seconds. In this case, appropriate values ​​for the applied laser beam power and the laser spot diameter must be selected to ensure proper removal of the graphite from the substrate.

[0032] In some embodiments, the laser beam provides an energy density on the surface of the substrate in the range between about 10 kJ / mm 2 and about 45 kJ / mm 2 , preferably between about 14 kJ / mm 2 and about 40 kJ / mm 2 .

[0033] After cleaning, the amount of graphite on the substrate surface 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 intended to receive the deposited material to create a metal-based coating during subsequent laser deposition, laser welding, or laser cladding. These holes are usually in the shape 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%.The inventors have found that when a metal-based coating is applied to the already cleaned substrate (i.e., the substrate that has a lower amount of graphite on its surface after irradiation of the surface with a laser beam as described above), i.e., when a laser cleaning pretreatment is performed as a separate step before applying the laser cladding coating, the adhesion of the cladding layer(s) is increased (the cladding layer is well bonded to the substrate), thereby 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 applied cladding or coating material during the subsequent laser cladding.

[0034] 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 process of a metal-based coating is reduced, and unwanted pits and "bubbles" are therefore less likely to form during the deposition process due to abrupt graphite deposition (evaporation). This increases the contact area between the substrate and the deposited coating layer. It has also been found that particulate matter emissions typically generated during use of the brake disc are also significantly reduced.

[0035] The laser system must radiate at a wavelength suitable for graphite evaporation. The wavelength of the laser system used to irradiate the substrate surface is therefore preferably in the range between approximately 800 and approximately 1200 nanometers (nm, 10-9 m), for example, between approximately 1000 and approximately 1150 nm or between approximately 1030 and approximately 1100 nm. Alternatively, other wavelengths suitable for graphite evaporation can be used. This applies to both laser cleaning and laser cladding.

[0036] The laser radiation is emitted from a laser processing head, which carries, for example, a nozzle. The emitted laser radiation passes through the nozzle coaxially, along the longitudinal axis of the nozzle. To ensure that the laser beam can shine onto the surface of the substrate during cleaning and thus remove graphite from it, the laser beam preferably moves 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. The laser system can be a pulsed laser or a continuous wave laser, e.g., a scanned continuous wave laser. It is preferably a continuous wave laser. Typically, the selected pattern follows a linear trajectory along a radial axis of the substrate surface.

[0037] Preferably, the substrate simultaneously rotates around its axis of rotation at a specific angular velocity. 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 to the inner radius of the substrate forming the brake disc, and thus lying on the substrate's axis of rotation, to a point on the substrate surface corresponding to its outer radius, or vice versa) creates a spiral path. In other words, the substrate of the brake disc rotates while the laser processing head moves linearly on the surface of the substrate (according to a specific pattern), with this linear movement following a radial path on the surface of the substrate.

[0038] 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.This applies to both laser cleaning and laser cladding. In laser cladding, the speed of the laser beam can be adjusted along the radius of the substrate to regulate the distance between adjacent metal layers.

[0039] By applying the laser cleaning treatment to the substrate surface, the amount of lamellar graphite in the upper part of the substrate (i.e., its most superficial thickness of approximately 80 µm) is significantly reduced. In particular, it has been observed that between approximately 50 and approximately 100% of the graphite lamellae present in the surface, particularly within a thickness of approximately 30 µm from the surface, are evaporated by the laser radiation.

[0040] Thus, when the disclosed laser cleaning treatment 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 that uppermost part of the substrate (e.g., by affecting its homogeneity or altering its microstructure).

[0041] For cleaning, preferred laser beam power values ​​are in the range between about 2 and about 12 kW, which have proven to be accurate for cycle times in the range between about 20 and about 120 seconds, such as between about 20 and about 55 seconds, when appropriate laser spot diameters are selected, such as laser spot diameters in the range between about 1.5 and about 4 mm. Even more preferred laser beam power values ​​are in the range between about 4 and about 8 kW, and even more preferably between about 5 and about 7 kW.

[0042] 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 approximately 1.5 and approximately 2.1 mm will result in evaporation of the flake graphite from the substrate surface during cleaning without significant substrate damage. In this case, the energy density on the substrate surface is between approximately 17 and approximately 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 approximately 3.1 and 4.0 mm will achieve evaporation of the flake graphite from the substrate surface without significant damage. The applied energy density is also between approximately 17 and 32 kJ / mm 2 .

[0043] For example, if the laser beam power is set to 3 kW and the cycle time to 30 s, selecting a laser spot diameter between approximately 1.9 and approximately 2.55 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 17 and approximately 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 approximately 3.2 and approximately 3.82 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 20 and approximately 35 kJ / mm 2 .

[0044] For example, if the laser beam power is set to 4 kW and the cycle time to 30 s, selecting a laser spot diameter between approximately 2.2 and approximately 2.95 mm will achieve the evaporation of flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 17 and approximately 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 approximately 3.3 and approximately 4.00 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 20 and approximately 37.5 kJ / mm 2 .

[0045] For example, if the laser beam power is set to 5 kW and the cycle time to 30 s, selecting a laser spot diameter between approximately 2.45 and approximately 3.3 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 17 and approximately 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 approximately 3.4 and approximately 4.00 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 27 and approximately 38 kJ / mm 2 .

[0046] For example, if the laser beam power is set to 6 kW and the cycle time to 30 s, selecting a laser spot diameter between approximately 2.7 and approximately 3.6 mm will achieve the evaporation of flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 17 and approximately 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 approximately 3.3 and approximately 4.00 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 25 and approximately 38 kJ / mm 2 .

[0047] 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 approximately 2.91 and approximately 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 approximately 17 and approximately 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 approximately 3.5 and approximately 4.00 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 27 and approximately 38 kJ / mm 2 .

[0048] 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 approximately 3.11 and approximately 4.00 mm will achieve the evaporation of flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 19 and approximately 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 approximately 3.2 and approximately 4.00 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 27 and approximately 44 kJ / mm 2 .

[0049] 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 approximately 3.00 and approximately 4.00 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 23 and approximately 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 approximately 3.2 and approximately 4.00 mm will achieve evaporation of the flake graphite from the substrate surface without significant substrate damage. In this case, the energy density applied to the substrate surface is between approximately 28 and approximately 44 kJ / mm 2 .

[0050] 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.

[0051] 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, for example between about 200 W and about 2 kW, the performance of the cleaning process in this case is only relatively good at relatively long cycle times (e.g., about 120 s) compared to short ones (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.

[0052] If one considers a typical brake disc, when applying the parameters mentioned (laser beam with a power between approximately 2 and approximately 12 kW, diameter of the laser spot between approximately 1.5 and approximately 4 mm), with the substrate rotating at a linear speed between approximately 80 and approximately 240 m / minute 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 approximately 160 and approximately 230 mm and an outer diameter between approximately 270 and approximately 410 mm requires a pre-treatment to remove graphite (cleaning pre-treatment) with a duration of between approximately 20 seconds and approximately 55 seconds.

[0053] The deposition of a metal-based coating on the surface of the substrate, from which graphite was removed during the previous laser cleaning, is carried out by laser cladding, in which powder (metal-based powder or a mixture of metal-based powder and carbide-based powder) is applied to the surface to be coated while a laser beam is irradiated onto the surface to be coated, preferably while the substrate is rotating. Laser cladding is preferably carried out with a continuous laser beam that describes a linear trajectory. During the coating process, a laser beam is selected whose laser spot area (as projected onto the surface of the substrate) is larger than the area of ​​the powder spot (as deposited on the surface).Using a laser spot larger than the powder spot area allows for heating the area of ​​the surface to which the powder is to be applied immediately before the powder is actually applied. This allows for further cleaning of the surface, in addition to the previously performed laser cleaning of the surface.

[0054] The powder is fed from a powder nozzle coupled to the laser head from which the laser beam is emitted, so that as the laser head moves, the laser beam and powder nozzle move together radially along the surface to be coated. A laser system is used that creates a circular laser spot. The diameter of the laser spot is selected to be larger than the diameter of the powder spot, preferably between about 10 and about 40% larger. The inventors have found that this additional laser heating, which occurs immediately before the actual material deposition, conditions or prepares the surface in such a way that the adhesion of the subsequently deposited powder is improved because the laser beam used in the laser deposition process causes the removal of additional lamellar graphite that may be present, for example, deeper in the substrate compared to its most superficial thickness.For example, while between about 50 and about 100% of the graphite in the top 30 µm of thickness was evaporated in the initial cleaning, the additional laser cleaning performed during the material deposition process causes the evaporation of graphite in a deeper area of ​​the substrate, e.g., at a depth between about 30 and about 50 µm. Without this additional laser heating / cleaning process, performed immediately before deposition of the overlay material, the graphite still present in the surface of the substrate may 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 heating / cleaning treatment.

[0055] The diameter of the laser spot used in laser cladding may range between about 1.5 and about 4 mm, preferably between about 2 and about 4 mm, more preferably between about 2.2 and about 3.7 mm, and even more preferably between about 2.5 and about 3.5 mm, and the diameter of the powder spot as deposited on the substrate is smaller than the diameter of the laser spot and preferably ranges between about 1 and about 3.5 mm, more preferably between about 1 and about 2.5 mm, and even more preferably between about 1 and about 2 mm, provided that the diameter of the laser spot is between about 10 and about 40% larger than the diameter of the powder spot.

[0056] Furthermore, the inventors have surprisingly discovered that, unlike conventional laser cladding processes, in which the axis of the emitted laser beam (and thus the axis of the corresponding laser spot on the surface to be treated) is aligned with the axis of the nozzle or container from which the powder is fed, the cladding process is optimized when 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 layers. It is therefore desirable for the laser spot to interact with the substrate without material being deposited during a certain interaction time. This interaction time requires a certain misalignment between the axis of the laser beam (and thus of the laser spot) and the axis of the powder spot.Therefore, the interaction time depends on the size of the laser spot and the powder diameter, the axial offset, and the process speed. The interaction time is preferably in the range between approximately 0.05 and approximately 5 ms. Therefore, the axis of the laser beam should not be aligned with the axis of the nozzle that delivers the powder. By decentering the axis, or the axial offset, of the powder spot with respect to the axis of the laser beam spot during the linear movement of the laser beam while the brake disc substrate rotates, the laser spot reaches an area on the surface to be treated before the powder is applied to the surface in the form of metal plating. The decentering occurs in such a way that the laser spot interacts with the substrate without material being deposited during the aforementioned interaction time.

[0057] 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 on the other hand), 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 supplied 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 surface area where the powder is being applied at the same time as the powder is being applied to the thermally prepared area, allowing the applied powder to melt and form a coating that bonds well with the thermally prepared surface of the substrate. By laser irradiating the surface area before powder application, the area is minimally altered by the evaporation of the graphite present in the top layer of the substrate, thereby improving the contact surface where the material (applied 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, and thus prevents any deterioration of the deposited metal-based layer.

[0058] During laser deposition of a first metal-based coating, the surface is irradiated with a laser beam emitted at a power of preferably between about 6 and about 16 kW, with the diameter of the laser spot preferably in the range between about 1.5 and about 4 mm, during a suitably selected cycle time. As already mentioned, the cycle time of the laser cleaning is preferably selected to coincide with the cycle time during which a metal-based coating is applied to the surface of the substrate from which graphite has previously been removed, in order to optimize the production of finished brake discs.Preferred values ​​for the laser beam power are in the range between about 7 kW and about 12 kW (inclusive), preferably between about 7.5 kW and about 10 kW (inclusive), which have proven suitable when suitable laser spot regions are selected within the stated laser spot diameters. As already mentioned, preferred values ​​for the laser spot diameter are in the range between about 2 and about 4 mm, more preferably between about 2.2 and about 3.7 mm, and even more preferably between about 2.5 and about 3.5 mm.

[0059] In some embodiments, during laser cladding, the cycle time is selected to be in the range between about 20 and about 55 seconds. In this case, appropriate values ​​for the applied laser beam power and the laser spot diameter must be selected.

[0060] In some embodiments of laser cladding for depositing a first cladding layer, the laser beam provides an energy density on the surface of the substrate in the range between about 14 kJ / mm 2 and about 50 kJ / mm 2 .

[0061] As already mentioned, the axis of the powder spot is preferably offset relative to the axis of the laser spot in a range between 0 (excluding 0) and about 20% of the diameter of the laser spot, preferably between about 2.5 and about 15% thereof, more preferably between about 5 and about 12.5% ​​thereof. For example, if the difference between the diameter of the laser spot and the diameter of the powder spot is between about 0.3 and about 0.5 mm, the interaction time can be selected between about 0.05 and about 0.7 ms, depending on the disk size and speed.

[0062] By irradiating the area to which the powder is immediately applied, the surface is thermally influenced at the moment the deposition material is picked up. In other words, the decentering of the axis, or offset, of the laser beam relative to the axis of the powder spot causes a thermal influence on the substrate.Thus, the inventors surprisingly discovered that, in contrast to the simultaneous delivery of laser radiation and powder, which causes undesirable displacement of the deposited material on the substrate surface because the material just deposited on the substrate is under stress, hindering the integration and adhesion of the material with the substrate, the magmatic powder particles that reach the surface with the aforementioned misalignment (and thus delay) can more easily fuse with the thermally influenced surface of the substrate, increasing their adhesion to the substrate. Due to the axial offset, 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 thus slightly thermally influenced, contributing to the subsequent integration of the cast material and the substrate.Furthermore, thermally influencing the substrate surface prior to powder deposition promotes the evaporation of additional flake graphite still present in the most superficial thickness of the substrate or deeper within the substrate relative to the most superficial thickness (e.g., in a region of the substrate between 30 and 50 µm deep) before the actual powder dispensing and melting. This results in the deposition material being applied to a surface that has additional holes created by the evaporation of graphite and that has already been slightly preheated.In summary, the decentering of the axis or offset of the powder spot with respect to the axis of the laser beam spot helps to integrate the metal deposition with the substrate and increase the removal of graphite without causing bubbles that damage the substrate and improve the adhesion of the metal-based coating to the substrate.

[0063] The decentralization or misalignment of the axis of the powder nozzle with respect to the axis of the laser beam 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.

[0064] After repeated cladding over the entire surface of the substrate (longitudinally and transversely), a metal-based coating or overlay essentially covers the substrate. The coated surface can be a friction surface of a brake disc.

[0065] In certain embodiments, a shielding gas is applied to the surface of the substrate during cleaning and / or laser cladding. The shielding gas is ejected, for example, through a gas nozzle. The gas nozzle can be mounted on the same laser processing head as the laser processing head carrying the nozzle through which the laser radiation is emitted. The shielding gas can be, for example, nitrogen or argon. During laser cladding, the shielding gas is preferably applied to the surface of the substrate to which the laser beam is applied, but on which no powder has yet been deposited.The inventors have found that the application of a shielding gas helps prevent oxidation of the surface to be treated after cleaning (or laser deposition) and contributes to surface homogenization, for example, by masking or reducing the trace of laser passes, as the overlap between adjacent passes can be reduced. Without the shielding gas, the gas generated during graphite evaporation tends to oxidize the substrate surface. Furthermore, without the shielding gas, more time is required to homogenize the surface (i.e., reduce the trace of laser passes) because a greater overlap between adjacent passes is required.

[0066] Preferably, the distance between the substrate surface and the proximal end of the nozzle from which the powder is to be applied to the surface, and the distance between the substrate surface and the focal point of the laser beam, are selected to achieve a predetermined coating size (i.e., width or diameter). This predetermined size is typically smaller than the size (i.e., diameter) of the powder nozzle from which the powder is delivered. After a specific cycle time, a complete metal-based coating is deposited on the substrate.

[0067] In certain embodiments, the deposition of an overlay layer involves depositing a single layer, preferably consisting of a mixture of metal and a carbide, preferably tungsten carbide or titanium carbide. This layer is obtained from a powder containing a mixture of metal powder and carbide powder.

[0068] As already mentioned, in order to deposit a coating on the surface of the substrate, the surface is irradiated with a laser beam emitted with a power in the range between about 6 and about 16 kW, the diameter of the laser spot being in the range between about 1.5 and about 4 mm and the cycle time being selected accordingly.

[0069] 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 approximately 2.4 and 3.3 mm. In this case, the energy density applied to the substrate surface is between approximately 21 and approximately 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 approximately 3 and 4 mm. In this case, the energy density applied to the substrate surface is between approximately 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 approximately 3.5 and approximately 4 mm. In this case, the energy density applied to the substrate surface is between approximately 32 and approximately 44 kJ / mm 2At this power level, large laser spot diameters, e.g., between approximately 3.5 and approximately 4 mm, are less preferred, 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.

[0070] 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 approximately 2.5 and 3.3 mm. In this case, the energy density applied to the substrate surface is between approximately 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 choosing a laser spot diameter between approximately 3.2 and approximately 4 mm. In this case, the energy density applied to the substrate surface is between approximately 27 and approximately 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 choosing a laser spot diameter between approximately 3.8 and approximately 4 mm. In this case, the energy density applied to the substrate surface is between approximately 38 and approximately 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.

[0071] 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 approximately 2.7 and 3.7 mm. In this case, the energy density applied to the substrate surface is between approximately 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 approximately 3.3 and approximately 4 mm. In this case, the energy density applied to the substrate surface is between approximately 30 and approximately 46 kJ / mm 2 .

[0072] 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 approximately 2.7 and 3.7 mm. In this case, the energy density applied to the substrate surface is between approximately 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 selecting a laser spot diameter between approximately 3.5 and approximately 4 mm. In this case, the energy density applied to the substrate surface is between approximately 35 and approximately 46 kJ / mm 2 .

[0073] 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 approximately 3.2 and approximately 4 mm. In this case, the energy density applied to the substrate surface is between approximately 28 and approximately 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 approximately 2.6 and approximately 3.5 mm. In this case, the energy density applied to the substrate surface is between approximately 23 and approximately 43 kJ / mm 2 .

[0074] In certain embodiments, applying a coating layer comprises applying a first coating layer of metal and a second coating layer on top of the first coating layer, which second coating layer consists of a mixture of metal and a carbide, preferably tungsten carbide or titanium carbide. When two metallic coating layers are applied, cleaning (pretreatment) of the surface by irradiation with a laser beam (without powder deposition) is performed only before applying the first coating layer (and not before applying the second coating layer).As with laser cladding for depositing the first deposit layer onto the substrate, the second deposit layer is deposited using a laser beam in which the area of ​​the laser spot (as projected onto the substrate surface) is larger than the area of ​​the powder spot (as deposited onto the surface), the ratio between the diameters of the laser spot and the powder spot is similar, and the axis of the powder spot is decentered, or offset, with respect to the axis of the laser beam spot. The deposition of the second deposit layer is therefore essentially the same as the deposition of the first deposit layer, including the type and size of the powder material, except for the selection of certain operating parameters.

[0075] To deposit a second coating on an already deposited first coating, the surface is irradiated with a laser beam emitting at a power in the range between approximately 7 and approximately 18 kW, with the laser spot diameter in the range between approximately 1.5 and approximately 4 mm, during a suitably selected cycle time. Preferred values ​​for the laser beam power are in the range between approximately 7.5 kW and approximately 14 kW, more preferably between approximately 7.5 and approximately 12 kW, which have proven successful in selecting suitable laser spot diameters and cycle times. In particular, the selected cycle time is preferably in the range between approximately 20 and approximately 55 seconds. Since the second application layer is typically thicker than the first application layer, higher power and / or a longer cycle time are normally required to melt the required powder.

[0076] 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 about 25 kJ / mm 2 and about 70 kJ / mm 2 .

[0077] 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 approximately 2.2 and approximately 3.0 mm. In this case, the energy density applied to the substrate surface is between approximately 29 and approximately 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 approximately 2.7 and approximately 3.5 mm. In this case, the energy density applied to the substrate surface is between approximately 36 and approximately 60 kJ / mm 2 Small laser spot diameters are preferred because the powder diameter is only slightly smaller than the laser spot diameter, and large powder particles require higher power for melting.

[0078] 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 approximately 2.2 and approximately 3.0 mm. In this case, the energy density applied to the substrate surface is between approximately 33 and approximately 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 approximately 2.7 and approximately 3.3 mm. In this case, the energy density applied to the substrate surface is between approximately 46 and approximately 70 kJ / mm 2 Small laser spot diameters are preferred because the powder diameter is only slightly smaller than the laser spot diameter, and large powder particles require higher power for melting.

[0079] 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 approximately 2.3 and approximately 2.9 mm. In this case, the energy density applied to the substrate surface is between approximately 40 and approximately 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 approximately 3 and 4 mm. In this case, the energy density applied to the substrate surface is between approximately 35 and 63 kJ / mm 2 .

[0080] 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 approximately 2.7 and approximately 4 mm. In this case, the energy density applied to the substrate surface is between approximately 28 and approximately 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 approximately 3.1 and approximately 4 mm. In this case, the energy density applied to the substrate surface is between approximately 38 and approximately 63 kJ / mm 2 .

[0081] 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.

[0082] For laser cladding, the same or a different laser system can be used that is also used for cleaning or for the cleaning phase.

[0083] Another aspect of the disclosure relates to an apparatus for manufacturing brake discs, comprising: a laser cleaning system configured to remove graphite from a surface of a substrate for manufacturing a brake disc, the substrate being made of a graphite-containing metallic material, by applying a cleaning process in which the surface is irradiated with a laser beam emitted at 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; and a laser deposition system configured to apply a metal-based coating layer to the surface of the substrate from which graphite has been removed by the application of a laser coating.

[0084] In some embodiments, the laser cleaning system and the laser coating application system comprise a common laser head or different laser heads.

[0085] In some embodiments, the apparatus for manufacturing brake discs further comprises a 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) emitting the laser beam move(s) linearly on the surface of the substrate, wherein the linear movement follows a radial trajectory on the surface of the substrate.

[0086] In some embodiments, the rotating device is configured such that the brake disc rotates at a linear speed in the range of 80 to 240 m / minute, preferably in the range of 120 to 200 m / minute.

[0087] 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.

[0088] In some embodiments, the laser cleaning system is configured such that the surface is irradiated during cleaning with a laser beam emitted at a power in the range between 4 and 8 kW, preferably between 5 and 7 kW.

[0089] 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.

[0090] 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.

[0091] In some embodiments, the laser coating system comprises a powder feed and is configured to apply powder using a laser beam to apply a metal-based coating layer to the surface of the substrate from which graphite has previously been removed, wherein the diameter of the laser spot is larger than the diameter of the powder spot to be applied to the surface, wherein the diameter of the laser spot is preferably between 10 and 40% larger than the diameter of the powder spot.

[0092] In some embodiments, the diameter of the laser spot in the laser coating 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; 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 even more preferably between 1 and 2 mm.

[0093] In some embodiments, during laser cladding to deposit a metal-based coating, the axis of the laser beam and hence of the laser spot is offset with respect to the axis of the powder spot, preferably 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, more preferably between 2.5 and 15% thereof, even more preferably between 5 and 12.5% ​​thereof.

[0094] In some embodiments, the laser cladding system is configured such 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 more preferably between 7.5 and 10 kW, while the laser cladding system is configured to operate with a cycle time between 20 and 55 seconds.

[0095] In some embodiments, the laser cladding system is configured such that the diameter of the laser spot is in the 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.

[0096] In some embodiments, the laser cladding system is configured such that, during laser cladding to deposit a metal-based cladding layer, an energy density on the surface of the substrate in the range between 14 kJ / mm 2 and 50 kJ / mm 2 is applied.

[0097] A third aspect of the disclosure relates to a use of the brake disc manufacturing device according to the first aspect or of the device for manufacturing brake discs according to the second aspect of the disclosure for providing a brake disc, wherein during 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.

[0098] A fourth aspect of the disclosure relates to a use of the brake disc manufacturing device according to the first aspect or the device for manufacturing brake discs according to the second aspect of the disclosure for manufacturing a brake disc, wherein the production of a first metal-based coating layer by laser deposition welding further comprises the production of a second laser deposition weld, so that the second metal-based coating layer is applied to the first metal-based coating layer.

[0099] In some embodiments of the fourth aspect, the laser cladding system 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.

[0100] In some embodiments of the fourth aspect, the laser cladding system is configured to operate during laser cladding to deposit the second metal-based cladding layer such that the energy density on the surface of the substrate is in the range between 25 and 70 kJ / mm 2 lies.

[0101] In some embodiments of the fourth aspect, the laser cladding system or laser system for cladding is configured such that a layer of metal, preferably steel, is applied during the first laser cladding 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 cladding.

[0102] A fifth aspect of the disclosure relates to a brake disc which is / was produced with the brake disc manufacturing apparatus of one of the first and second aspects and / or by using one of the third and fourth aspects, wherein the substrate is preferably made of grey cast iron.

[0103] 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

[0104] 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 a treatment is applied to it. Fig. show photographs of the brake disc after application of a laser-based cleaning treatment according to this disclosure. Fig. show photographs of a brake disc as in Fig. after applying a laser-based cleaning treatment according to this disclosure. Fig. shows a photograph of a brake disc as in Fig. after applying a laser-based cleaning treatment according to this disclosure. The Fig. schematically show a cleaning treatment applied to a surface of a substrate of a brake disc 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. Fig. shows a SEM image of the surface of a brake disc substrate (as shown in Fig. shown) without laser cleaning. Fig. shows a SEM image of the surface of the substrate after applying laser cleaning according to embodiments of the disclosure. Fig. shows another SEM image of the substrate surface without laser cleaning. Fig. show SEM images of the substrate surface to which various laser cleaning processes were applied. Fig. shows a photo of the brake disc to which the surface shown belongs, before the application of a treatment. Fig. show the brake disc after laser cleaning. The Fig. show SEM images of the surface of the substrate from Fig. after treatment with laser cleaning according to the embodiments of the disclosure. The Fig. show cross sections of the substrate Fig. after treatment with laser cleaning according to the 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. The Fig. schematically show a laser cladding process applied to the previously cleaned surface of a substrate. 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 a brake disc manufactured after laser treatment and laser cladding to deposit two deposit layers 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 by laser cladding according to embodiments of the disclosure. The Fig. show cross-sections of a brake disc after it has been completely manufactured after laser treatment and laser deposition welding according to the embodiments of the invention. Fig. are SEM images. The Fig. are optical microscopy (OM) images. The Fig. show OM images of brake discs to which a single coating was applied. The Fig. show OM images of brake discs to which a single coating layer was applied without the axis of the laser spot and the axis of the powder spot being misaligned or offset. Fig. shows an OM image of a brake disc to which two coating layers were applied without the axis of the laser spot and the axis of the powder spot being misaligned. The Fig. show OM images of a brake disc to which a single coating was applied after the described laser deposition welding. Fig. shows an OM image of an overlay layer applied to a brake disc according to embodiments of this disclosure. The Fig. show a cross-sectional view of an AISI 316L coating applied to the surface of a brake disc substrate to which neither pre-cleaning nor axis offset was applied during laser cladding. 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 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. DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

[0105] 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 friction-circular annular 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 the outer diameter is 350 mm. In the top view of the Fig. only one friction surface 13' is visible. The Fig. show photographs of the brake disc 10 from Fig. after an outer friction surface 13' ( Fig. ) and the opposite outer friction surface 13 ( Fig. have been subjected to a laser cleaning treatment to remove graphite according to this disclosure. Fig. 4H shows a photo of the brake disc 10 from Fig. 4G, after an outer friction surface 13' of the disc has been subjected to a laser cleaning treatment according to the present disclosure. The Fig. 1D and Fig. 1E show detailed pictures of the brake disc from Fig. 1A after application of a laser-based cleaning treatment according to this disclosure.

[0106] 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.

[0107] The Fig. schematically show a laser cleaning treatment applied to a surface of the substrate 12. The surface can be one of the two surfaces 13, 13' of the outer disk part 14. In the Fig. Only a radial part of the disk 10 (and thus a radial part of the substrate 12, which forms a friction surface 13, 13') is shown. The section shown comprises the disk center (marked 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. The surface 13, 13' is cleaned by subjecting the surface 13, 13' to a 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.

[0108] The surface 13, 13' is irradiated with a laser beam that defines a laser spot 20 on the surface of the substrate. In one embodiment, the movement of the laser beam and thus of the laser spot 20 on the surface 13, 13' is in the Fig. represented by a straight dashed arrow. Fig. shows the beginning of a cleaning 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 (substrate 12). In preferred embodiments, the linear velocity of the laser beam is constant, and the angular velocity (rpm) of the disk is configured to vary depending on the radial position of the laser beam and thus of the laser spot 20 on the surface to be machined, so that the actual linear velocity of the disk is constant, and the interaction between the laser beam and the substrate is also constant. The simultaneous linear forward movement of the laser beam (laser spot 20) 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 generates a spiral laser beam trajectory on the substrate 12.

[0109] Once the laser beam, and thus the laser spot 20, has moved radially from the inner radius 141 of the substrate 12 to the outer radius 142, or vice versa, the laser spot 20 either follows a return trajectory while the substrate 12 rotates, or the laser equipment is returned to its original position (e.g., the home position at the inner radius 141) and a one-way motion of the laser beam is restarted while the substrate 12 rotates. This linear motion (either back and forth or in one direction) of the laser beam during the rotation of the substrate 12 is repeated over a certain period of time until the amount of graphite present on the surface 13 of the substrate 12 is reduced.

[0110] 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 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. It therefore heats the surface encountered by the laser beam evenly. The inventors have found that such a homogeneous power distribution contributes to the efficiency of the cleaning process.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.

[0111] The laser beam is moved or scanned in such a way that a specific pattern is created 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 trajectory. Fig. The laser beam is moved, for example, along a radial axis of the surface 13, 13' to be treated in a linear path. The laser system that emits the laser beam is conventional and not the subject of the present invention. It typically comprises a laser system with a laser head for generating a laser beam and a positioning system, such as a scanner. A scanner typically comprises two mirrors or the like for two-dimensional scanning of the laser beam in a horizontal plane. The movement of the laser head, which is suitably controlled, allows the laser beam to radiate onto the selected target and define a laser spot thereon. As shown in the Fig. As shown, the laser spot is circular.

[0112] 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.

[0113] In this way, lamellar graphite is removed from the surface 13, 13' of the substrate 12. In particular, lamellar graphite is reduced on the surface of the substrate and to a maximum depth of approximately 80 µm. Under these conditions, a typical brake disc substrate with an inner diameter between approximately 160 and approximately 230 mm and an outer diameter between approximately 270 and approximately 410 mm requires a graphite removal cleaning treatment lasting between approximately 20 seconds and approximately 55 seconds. This cleaning treatment has been found to enable the evaporation of between 50 and 100% of the graphite flakes present in the surface, particularly within a thickness of 30 µm from the surface.

[0114] The laser beam can be directed either vertically onto the surface to be treated, as in Fig. shown schematically, or with a specific inclination or tilt angle α, as in Fig. The inclination angle α is defined as the angle between the plane on which the surface 13, 13' to be treated lies and a plane perpendicular to the laser beam, as shown in Fig. shown. In the Fig. only schematically shows a section of the surface 13, 13' to be treated, which is limited by the inner 141 and the outer radius 142. Preferably, the tilt angle α is in the range between 0 and about 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 inclination of the substrate with respect to the laser beam axis does not affect the laser treatment or the removal of graphite. The substrate is tilted with respect 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 a protective or shielding gas to be delivered 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.

[0115] Although not shown, during operation of the laser system for applying a laser beam to the surface of the substrate to remove graphite therefrom, a shielding gas may be ejected onto the surface 13, 13' of the substrate 12. The shielding gas is ejected, for example, through a gas nozzle that preferably moves simultaneously with the laser head. The laser head and the gas nozzle may, for example, be rigidly connected to one another so that they move together in the same path. The shielding gas may 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 the cleaning treatment and contributes to the rapid homogenization of the surface, thereby improving overall cleaning.

[0116] The Fig. correspond to a first test. The surfaces 13 and 13' of the brake disc after laser treatment to remove graphite are shown in the Fig. The photos show a gray cast iron brake disc with an inner diameter of 177 mm and an outer diameter of 306 mm, which was lasered with a continuous wave laser with the following parameters: 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 disc constant), equivalent linear speed of the rotating substrate of 170 m / minute, applied energy density = 31438 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' appears matte after laser cleaning, while the surface of the untreated substrate is much brighter. This means that the surface of the brake disc has been affected by the laser treatment in the sense that the laser cleaning causes a significant reduction in the surface graphite, which is evaporated. As a result of the evaporation (removal) of 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 brake disc.

[0117] 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 left behind 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 taken 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 be essentially flat, now has a certain depth (holes) created by graphite evaporation. These holes lead to an increase in the contact area of ​​the substrate, which is intended to receive the deposited material during subsequent laser deposition.

[0118] The Fig. , which is still on the first attempt ( Fig. ) show microscopic images of a cross-section of the substrate of the wafer after treatment with the disclosed laser cleaning. Figures 6A and 6B 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 the laser cleaning process. These holes 52 allow for the deposition and integration of a subsequently applied metal-based coating with the substrate. Fig. shows a microscope image of a cross-section of the same substrate 12, on which a metal-based coating was subsequently applied after laser cleaning. The image resolution of Fig. is twice as high as that of Fig. It can be seen that the holes 52 on the surface and in their vicinity, which were created by the removal of the graphite, were filled with the coating layer 81. Thanks to the increase in the contact area of ​​the substrate by 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.

[0119] The positive effect of the application of a protective gas can be observed in a second experiment 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.

[0120] A third attempt was made with the disc in Fig. carried out. Fig. shows a photo of a cast iron brake disc with an inner diameter of 220 mm and an outer diameter of 350 mm, to which no laser cleaning was applied. 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, proving 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 of 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, during which some of the graphite lamellae were detached or evaporated from the substrate, voids remain caused by the missing graphite lamellae. 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.

[0121] A fourth and a fifth test were carried out with a brake disc as used in Fig. is shown.

[0122] In the fourth 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.

[0123] In the fifth 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, diameter of the laser spot = 3.3 mm and applied energy density = 24552.83 J / mm2 . 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.

[0124] 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.

[0125] Once the amount of graphite in the surface of the brake disc substrate has been reduced, one or more overlay layers are applied to the surface to obtain a manufactured brake disc, i.e., a brake disc with increased wear and corrosion resistance and / or increased coefficient of friction compared to the wear and corrosion resistance and / or coefficient of friction of an uncoated brake disc. The brake disc can be coated with one or more layers, for example, one or two layers, or even more than two layers, depending on various factors, such as the expected performance of the manufactured brake disc. The coated surface is a friction surface of a brake disc.

[0126] The at least one coating is applied by laser cladding, in which a metal-based powder is applied to the previously cleaned surface 13, 13', while a laser head, which is moved along the surface to be treated with a rotating disk, emits a laser beam onto the surface 13, 13' to be coated. The same laser system as used for cleaning or a different one can be used for laser cladding. In laser cladding, 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 while the laser head moves. Typically, a carrier gas is used to pull or drag the powder onto the surface to be treated.

[0127] 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 substrate 12 rotates in a similar manner as in the Fig. 2A and Fig. 2B. However, since in this case powder is applied to the surface 13, 13' in the form of powder spots 40 to apply a coating, each area of ​​the surface 13, 13' to be coated is preferably supplied with powder in a single pass. This means that 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 disc are thus designed so that the surface is ultimately covered with a substantially homogeneous coating layer.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 deposited layer is formed on the surface 13, 13' of the substrate 12. In the . Fig. a sketch of the metallic cords or layers 50 applied to the surface is shown.

[0128] 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 previously cleaned surface 13, 13'. 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. The powder, in turn, is applied from a nozzle onto the surface 13, 13' to be treated and forms a powder spot or layer 40 thereon. The laser head can be the same or different from the laser head used to emit a laser beam in the previously described laser cleaning.During operation of the laser system for performing laser cladding, a shielding gas 65 can be delivered to the surface of the substrate, for example, through a gas nozzle that moves simultaneously with the laser head. The gas nozzle can be the same as the powder nozzle, or there can be two different nozzles, preferably attached to one another so that they move together. The shielding gas can be, for example, nitrogen or argon. The area of ​​the laser spot 30 is 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 about 10% and about 40% larger than the diameter of the powder spot 40 applied to the surface 13, 13'.Furthermore, the axis 71 of the powder spot 40 is decentered (off-axis offset) relative to the axis 73 of the laser spot 30 by an amount between 0 and about 20% of the diameter of the laser spot, preferably between about 2.5 and about 15% thereof, and more preferably between about 5 and about 12.5% ​​thereof. In several tests, 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 offset from the axis 73 of the laser spot 30 by at least about 10% of the diameter of the laser spot 30.

[0129] As with the previously applied cleaning ( Fig. 2A and Fig. 2B), the laser beam 63 describes a radial movement between a point on the inner radius 141 of the substrate 12 and a corresponding point on its outer radius 142 or vice versa, while the substrate 12 rotates until a complete coating is deposited on the cleaned surface 13, 13'. Fig. show schematic examples of applying a laser layer to the previously cleaned surface 13, 13' of the substrate 12. As shown in the Fig. 2A and Fig. 2B is also in the Fig. 8A and Fig. 8B only a radial part of the substantially cleaned surface 13, 13' of the substrate 12 is shown schematically.

[0130] The Fig. show an embodiment of laser cladding, with which a coating layer is applied to the substrate 13, 13'. The energy distribution of the laser beam is a top-hat distribution. The laser head and the powder nozzle move radially together, either from the inner radius 141 to the outer radius 142 of the substrate 12, whose surface 13, 13' is being treated, or from the outer radius 142 to its inner radius. The diameter of the powder spot 40 is smaller than the diameter of the laser spot 30. The axis 73 of the laser beam 63 is not aligned with the axis 71 of the powder discharge nozzle 61. Due to the simultaneous linear movement of the laser beam and the rotation of the substrate 12, the laser spot 30 reaches an area on the surface 13 to be treated even earlier than the deposition of the powder (metal dot) 40 on the surface. In the 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 strand) 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 feed of the laser head and nozzle as well as the rotation of the substrate. Cladding is carried out over a certain period of time until a complete coating has been applied to the substrate 13.

[0131] By applying the disclosed laser cladding following laser cleaning, a substantially flat coating can be achieved compared to a coating without prior laser cleaning as previously disclosed. Fig. Figure 11 schematically shows the shape (outline) of the metallic coating 100 (deposited in the form of a "string") formed on the substrate during powder deposition after the disclosed laser cladding, in which the axis 71 of the powder spot 40 was decentered with respect to the axis 73 of the laser beam and the laser spot 30. It has been found that for a deposition layer with a thickness 108 of, for example, approximately 120 to 150 µm, the difference between the peaks 101 and the valleys 102 on the surface of the coating 100 typically does not exceed 30 µm.

[0132] The distance 105 between consecutive build-up welds (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 beam build-up welding immediately before powder deposition is referred to as 109.

[0133] As with the Fig. Laser cleaning shown, the laser cladding can be carried out either perpendicular to the surface to be treated (see e.g. Fig. which applies to the application, provided that in Fig. the powder nozzle is not shown) or with a certain tilt between the surface to be treated and the laser beam and the powder application (see e.g. Fig. , again assuming that in Fig. The inclination 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 nozzle and laser head (which move together and assume a fixed relative position) relative to a horizontal plane on which the substrate lies (not shown). Preferably, the tilt angle is between 0 and about 30 degrees, where 0° means that the laser beam is directed perpendicularly to the surface to be treated.

[0134] A sixth attempt was made with the brake disc from Fig. carried out after the laser treatment of the first experiment was performed. In the sixth experiment, a coating was applied using laser cladding as disclosed. The laser cladding process for depositing the coating was carried out with the following process 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 between 20-53 µm); Powder supplier: Höganäs. The powder cone axis was 400 µm off-center relative to the laser beam axis. Fig. shows a photo 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 demonstrates its quality and proper integration with the substrate. A suitable first coating was applied from AISI 316L. Its thickness is 100 µm ±40 µm.

[0135] The Fig. show microscope images of the brake disc after applying a single coating layer following the sixth test. Fig. shows an excerpt from Fig. It can be seen that the overlay layer 81 is free of holes or bubbles and the overlay layer 81 is well bonded to the substrate 12. This good performance is achieved by the combination of the pre-cleaning process and the offset of the powder spot and laser spot during the powder deposition process. Holes created by the evaporation of graphite during the laser cleaning pretreatment improve the contact area and are filled with metal-based material during the overlay welding. Heating the surface immediately before receiving the molten powder during the deposition process 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 processes has a maximum thickness of 47 µm (worst case). The resulting brake disc thus exhibits improved wear resistance and a better coefficient of friction.

[0136] The results ( Fig. ) of the sixth test can be compared with tests carried out on a brake disc with the same properties (material and dimensions) and the same laser cladding of the sixth test (laser type: Top Hat; circular laser beam; 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 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), but with some differences. In the Fig. In the test shown in the microscopic image, the coating was applied to a brake disc that had previously been cleaned with the laser according to the first test, with the axis of the powder spot being aligned with the axis of the laser beam and the laser spot during laser deposition welding. Fig. In the experiment shown (microscope image), the coating was applied to a brake disc that had not previously been cleaned with a laser, and during laser cladding, the axis of the powder spot was aligned with the axis of the laser beam and the laser spot.

[0137] The sample in Fig. performs very poorly. Many holes are observed in the coating layer 81. Holes or bubbles are also present 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 are caused by the explosion of the graphite lamellae during the powder deposition process. The samples of Fig. perform better than the sample in Fig. In both cases, a cleaning step according to this disclosure was carried out prior to the deposition process. They differ in the decentering of the axes or the axis offset, which in the test in Fig. was applied. Fig. shows optimal performance because the deposition layer 81 is free of holes or bubbles and the deposition layer 81 is well integrated with the substrate 12. This optimization is achieved by the combination of the pre-cleaning process and the offset of the powder spot and laser spot during the powder deposition process. Fig. shows a relatively good performance, although not as good as that of Fig. . The pre-cleaning process allows a significant reduction in holes or bubbles in the coating layer 81 compared to a sample without pre-cleaning process ( Fig. ). It also reduces the likelihood of graphite evaporation during the deposition process of the metallic coating. Fig. However, it can be seen 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 stress suffered by the material just deposited on the substrate, which hinders the integration and adhesion of the material with the substrate and provokes the explosion of graphite (abrupt evaporation) still present in the substrate, causing some holes in the deposition layer and poor contact between the deposition layer and the substrate.

[0138] The Fig. show more pictures of the sample from Fig. (Brake disc that was cleaned with a laser and then coated with a laser cladding, 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 process before laser cladding, essentially no holes are observed in the coating 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 applied to coat the substrate cannot bond well with the substrate, resulting in poor contact between the coating layer and the substrate. These defects are due to the stress on the material during the deposition process, which did not involve any axial displacement.

[0139] The poor integration and adhesion of the deposit material when neither pre-cleaning nor decentering of the axes was carried out during laser beam deposition welding is described in the Fig. The cross-sectional views of an AISI 316L coating 100 applied to a gray cast iron substrate without laser pre-cleaning or misalignment of the powder spot axis with respect to the laser spot axis are shown. Holes left open by the explosion of graphite during laser cladding can be seen.

[0140] A seventh test was carried out with a brake disc as in Fig. , without ( Fig. and with ( Fig. Pre-cleaning process. In both cases, a single coating layer was applied using the following laser cladding process: 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 = 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 in the range of 20-53 µm). A suitable overlay layer was made of AISI 316L. Its thickness is 100 µm ±40 µm.

[0141] In Fig. (Microscope image) The coating mentioned was applied to a brake disc that had previously been laser cleaned using the following parameters: 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 = 15 l / min; energy density of the laser beam used = 17,537.73 J / mm 2 . In Fig. (Microscope image) The coating was applied to a brake disc that had not previously been laser cleaned. In both cases, the axis of the powder spot during laser cladding was offset (decentered) by 400 µm from the axis of the laser beam and the laser spot.

[0142] The pattern in Fig. demonstrates optimal performance. The overlay layer 81 is free of holes and well bonded to the substrate 12. This optimization is achieved through the combination of the pre-cleaning process and the offset of the powder spot and laser spot during the powder deposition process. 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 cladding. The off-axis laser cladding process 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 caused by the explosion of additional graphite. The resulting brake disc thus exhibits improved wear resistance and a better coefficient of friction.

[0143] An eighth 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.

[0144] Optionally, a second layer can be applied on top of the first layer, using a similar procedure to the first layer. Fig. The schematic process shown is also suitable for applying the second layer.

[0145] A ninth attempt was made with a brake disc as in Fig. carried out after the laser cleaning treatment of the first trial and the first application layer of the Fig. (sixth experiment). In the ninth experiment, a second coating layer was deposited on the first using laser cladding as disclosed. The laser cladding process for depositing the second coating 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. 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 photograph by Fig. Macroscopically, the essentially flat coating layer is visible. The flatness and flawlessness (no holes or cracks) of the coating layer demonstrates its quality and correct integration with the first coating layer.

[0146] The Fig. show SEM images of two exemplary cross-sections of the substrate of the disc from Fig. (on which a laser cleaning and two coating 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 takes up 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 deposition welding. 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 that occurred immediately before the deposition of the metal-based powder by shifting the axis of the powder cone relative to the axis of the laser beam during the first 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.

[0147] A tenth test was conducted to compare the results of the ninth test (application of the second coating using misaligned axes) with the application of a second coating on a similar brake disc (after applying the laser cleaning treatment of the first test and the first coating of the sixth test, Fig. to compare, but in this case without any offset between the axis of the powder spot and the axis of the laser beam and the laser spot. As in the ninth experiment, laser beam cladding for the deposition of the second deposit 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. Certain defects 98 can be seen at the interface between the two layers 81 and 82, 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 subjected during the deposition process.

[0148] In an eleventh test, a second coating layer was applied to a brake disc as in Fig. deposited on a surface on which a first coating layer had already been applied. No laser cleaning was applied before the deposition of the first coating. The laser cladding process for the deposition of the first coating 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 coating 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.

[0149] In a twelfth test, a second coating layer was applied to a brake disc as in Fig. deposited on a surface on which a first coating layer had already been applied. No laser cleaning was applied before the deposition of the first coating. The laser cladding process for the deposition of the first coating 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 / mm 2The 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.

[0150] In a 13th test, a second coating layer was applied to a brake disc as in Fig. deposited on a surface on which a first coating layer had already been applied. No laser cleaning was applied before the deposition of the first coating. The laser cladding process for the deposition of the first coating 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.

[0151] 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.

[0152] 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 expression "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."

[0153] The invention is of course not limited to the specific embodiment(s) described herein, but also includes all variations that can be considered by any person skilled in the art (e.g. with regard to the choice of materials, dimensions, components, configuration, etc.) within the general scope of the invention as defined in the claims. 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 24382550.2

[0001] US 2013 / 0153345A1

[0008] 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 cleaning system arranged to remove graphite from the surface (13, 13') of the substrate (12) by applying a cleaning by irradiating the surface with a laser beam emitted with a power between 2 and 12 kW, wherein the diameter of the laser spot is between 1.5 and 4 mm; and a laser deposition welding system arranged to apply a metal-based coating layer to the surface (13, 13') of the substrate (12) from which graphite has been removed by laser deposition welding, wherein the laser cleaning system and the laser cladding system contain one or more laser heads. [2] Brake disc manufacturing apparatus according to claim 1, comprising a rotating device arranged to rotate the substrate of the brake disc during cleaning and / or during 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. [3] Brake disc manufacturing apparatus according to claim 2, wherein the rotating 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. [4] Brake disc manufacturing apparatus according to one of claims 1 to 3, further comprising a protective gas supply 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. [5] Brake disc manufacturing device according to one of claims 1 to 4, wherein the laser cleaning system is arranged to irradiate the surface during cleaning with a laser beam emitting with a power in the range between 4 and 8 kW, preferably between 5 and 7 kW. [6] Brake disc manufacturing apparatus according to one of claims 1 to 5, wherein the laser cleaning system is arranged to adjust the diameter of the laser spot used for graphite removal during cleaning to a value 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. [7] Brake disc manufacturing device according to one of claims 1 to 6, wherein the laser cleaning system is arranged to provide a laser beam during cleaning which has an energy density on the surface of the substrate in the range between 10 and 45 kJ / mm 2 delivers. [8] Brake disc manufacturing device according to one of claims 1 to 7, further comprising a powder feed, in particular with a powder nozzle, wherein the laser cladding system is arranged to apply powder using a laser beam during laser cladding for applying a metal-based coating to the surface of the substrate from which graphite has previously been removed, the laser spot diameter of which is larger than the diameter of a powder spot to be applied to the surface, wherein the diameter of the laser spot is preferably between 10 and 40% larger than the diameter of the powder spot. [9] Brake disc manufacturing device according to claim 8, wherein the laser cladding system is arranged to set the diameter of the laser spot used in the laser cladding to a value 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 to set the diameter of the powder spot to a value in a range between 1 and 3.5 mm, preferably between 1 and 2.5 mm and more preferably between 1 and 2 mm. [10] Brake disc manufacturing apparatus according to one of claims 8 to 9, wherein the laser cladding system is arranged to provide the axis of the laser beam and thus of the laser spot offset with respect to the axis of the powder spot during laser cladding for depositing a metal-based coating. [11] Brake disc manufacturing apparatus according to claim 10, wherein the laser cladding system is arranged to provide the axis of the powder spot 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 15% thereof, more preferably between 5 and 12.5% ​​thereof. [12] Brake disc manufacturing device according to one of claims 1 to 11, in which the laser cladding system is arranged to set the power of the laser beam to a value in the range between 6 kW and 16 kW, preferably between 7 kW and 12 kW and particularly preferably between 7.5 and 10 kW during laser cladding for depositing a metal-based coating, and a cycle time of between 20 and 55 seconds is selected. [13] Brake disc manufacturing apparatus according to one of claims 1 to 12, wherein the laser cladding system is arranged to set the diameter of the laser spot to a value in the 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 during laser cladding for depositing a metal-based coating. [14] Brake disc manufacturing device according to one of claims 1 to 13, wherein the laser cladding system 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. [15] Brake disc manufacturing device according to one of claims 1 to 14, wherein the laser cladding system is arranged to deposit a single layer during laser cladding, 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, wherein the laser cladding system is arranged to perform a second laser cladding to apply a second metal-based cladding layer to the first metal-based cladding layer. [17] Brake disc manufacturing device according to claim 16, wherein the laser cladding system is arranged to set the power of the laser beam to a value in a range between 7 and 18 kW, preferably between 7.5 and 14 kW and particularly preferably between 7.5 and 12 kW, and to set the cycle time between 20 and 55 seconds during the second laser cladding for depositing a second metal-based coating. [18] Brake disc manufacturing device according to claim 16 or 17, wherein the laser cladding system is arranged to achieve an energy density on the surface of the substrate in the range between 25 and 70 kJ / mm 2 to apply. [19] Brake disc manufacturing device according to one of claims 16 to 18, wherein the laser cladding system is arranged to apply a layer of metal, preferably steel, during the first laser cladding 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, during the second laser cladding. [20] Use of the brake disc manufacturing apparatus according to any one of claims 16 to 18, wherein the production of a first metal-based coating layer by laser cladding further comprises the production of a second laser cladding such that the second metal-based coating layer is applied to the first metal-based coating layer. [21] Use according to claim 20, wherein the laser deposition welding system is arranged to adjust the power of the laser beam to a value in the range between 7 and 18 kW, preferably between 7.5 and 14 kW and particularly preferably between 7.5 and 12 kW, and the cycle time is selected between 20 and 55 seconds. [22] Use according to one of claims 20 and 21, wherein the laser deposition welding system is arranged to achieve an energy density on the surface of the substrate in the range between 25 and 70 kJ / mm 2 to provide. [23] Use according to one of claims 20 to 22, wherein the laser cladding system is arranged for cladding to apply a layer of metal, preferably steel, during the first laser cladding 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, during the second laser cladding. [24] Brake disc manufactured with the brake disc manufacturing device according to one of claims 1 to 19 and / or by the use according to one of claims 20 to 23, wherein the substrate is preferably made of grey cast iron.

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