Main body comprising a coating system

Abstract

The invention relates to a main body (1) comprising a coating system (2), the coating system (2) comprising at least one layer (3, 4) having a matrix alloy (5), at least one of the layers (3, 4) comprising at least the following elements in wt.% of the matrix alloy (5): iron; from 10 wt.% to 26 wt.% chromium; from 0.3 wt.% to 5 wt.% carbon; and from 0.5 wt.% to 15 wt.% the sum of niobium, titanium and vanadium, wherein the coating system (2), in at least one of the layers (4) having the matrix alloy (5), also comprises separately added carbide particles (6) in a proportion of at least 20 vol.% to 70 vol.% of the entire layer (4). The proposed main body comprising a coating system makes it possible to achieve an outstandingly corrosion-resistant and wear-resistant surface, especially for the friction surface of a brake disc.

Description

[0001] Base body with a coating system

[0002] The invention relates to a base body with a coating system, a powder material mixture with such a base body for a coating system of a base body, and a method with such a powder material mixture for coating a base body.

[0003] In industries such as the automotive industry, balancing component quality criteria with a high degree of cost awareness is a perpetual challenge. Sustainability issues are also becoming increasingly relevant in this equation. This problem is particularly evident in the area of ​​brake discs or other coated parts subject to high levels of stress.

[0004] Brake discs, for example, are known in the state of the art as cost-effective components made of gray cast iron. However, one problem with cast brake discs is their tendency to corrosion and insufficient abrasion resistance, which contributes to increased particulate pollution. Braking on uncoated cast brake discs, for example, accounts for approximately 15% of a vehicle's total particulate emissions. These negative properties can be reduced by coating the brake disc base. Laser coating processes have generally prevailed over paint coatings because they can create a functional layer that achieves greater abrasion resistance, improved corrosion protection, and a reduction in particulate emissions.

[0005] A well-known method in the prior art for coating substrates, such as brake discs, is flame spraying. In this process, a welding filler material made of wire or powder is introduced into a nozzle. When a powdered welding filler material is added, the powder material is conveyed evenly from a powder container and guided by a conveying gas stream through the burner nozzle to the burner flame. This ensures that molten or partially melted particles adhere to the surface to be coated, accelerated by the combustion flame. Flame spraying is a comparatively simple and cost-effective process; however, the resulting coatings can have a relatively high degree of porosity, lack a molten metallurgical bond with the substrate, and have high gas consumption.

[0006] An alternative is laser cladding [LA], which, for example, can achieve lower porosity with reduced gas consumption. LA is a welding process that uses laser radiation to melt the welding filler material used, supplied in powder or wire form. When a powdered welding filler material is supplied, this powder material is guided to a processing point using a carrier gas in a protective gas atmosphere. The processing point is aligned with the base body surface. A laser beam is focused on the processing point and melts the substrate as well as any powder material passing the processing point. Unmelted powder particles of the powder material are completely melted in the molten pool. The powder nozzle is moved over the surface using movable axes, creating weld beads.The result is a coating that consists essentially of the powder material (i.e., within technical tolerances, completely apart from a transition area, the so-called dilution zone). This allows, for example, material tests on the finished coating to directly determine the composition of the powder material. Beneath the coating is the dilution zone, which consists of the filler material and the substrate material. The molten powder material collects above the dilution zone and forms the coating system.

[0007] A person skilled in the art will immediately recognize that, regardless of the coating thickness and / or number of layers, a fused-metallurgical bond forms, resulting in a technical improvement over, for example, thermally sprayed coatings. The fused-metallurgical bond leads to a dilution between the coating and the substrate. However, because the dilution zone is minimal in LA compared to other welding processes, the coating material can be determined from the coating.

[0008] High-speed laser cladding (HVLA) has evolved from LA. In order to achieve higher feed rates than with LA, in HVLA the welding filler material, provided as powder, is melted or partially melted using laser energy before it reaches the substrate, i.e. above the substrate surface. This is achieved by crossing the powder streams to be melted in a so-called powder focus one or more millimeters above the substrate surface. It should be noted that HVLA is preferably carried out with the welding equipment in the earth's gravitational field above the substrate. However, this can vary in some applications. Above therefore means at least merely at a distance from the substrate surface. The powder focus is overlaid with a laser beam so that powder particles pass through the laser beam and cast a shadow.As a result, not all of the laser energy reaches the substrate surface. The ratio of the total laser power [LI] to the laser power reaching the substrate is typically calculated by those skilled in the art as the transmittance. By adjusting various process parameters and the resulting transmittance, a coating can be achieved using HVLA as a fused-metallurgical composite.

[0009] A special HVLA process (referred to there as extreme high-speed laser cladding [EHLA]) is described, for example, in Schopphoven et al. ("Experimental and model-theoretical investigations into extreme high-speed laser cladding," dissertation at the Fraunhofer Institute for Laser Technology ILT, 2019, published online on the university library website), as well as DE 102011 100 456 A1.

[0010] Documents WO 2021 / 007 209 A1 and WO 2021 / 126 518 A1 disclose coatings. These coatings use the expensive carbide formers titanium and niobium, and sometimes also chromium, in large quantities. Based on this, the present invention seeks to at least partially overcome the disadvantages known from the prior art. The features of the invention emerge from the independent claims, for which advantageous embodiments are presented in the dependent claims. The features of the claims can be combined in any technically reasonable manner, whereby the explanations from the following description and features from the figures, which comprise supplementary embodiments of the invention, can also be consulted for this purpose.

[0011] The invention relates to a base body with a coating system, the coating system comprising at least one layer with a matrix alloy, wherein at least one of the layers comprises in wt.% proportionate to the matrix alloy at least the following elements:

[0012] Iron; and from 10 wt% to 26 wt% chromium; and from 0.3 wt% to 5 wt% carbon; and the sum of niobium, titanium and vanadium 0.5 wt% to 15 wt%, wherein the coating system in at least one of the layers with the matrix alloy further comprises separately added carbide particles in a proportion of the entire layer in question of at least 20 vol% to 70 vol%.

[0013] Unless explicitly stated otherwise, ordinal numbers used in the preceding and following descriptions serve only to clearly distinguish them and do not reflect the order or ranking of the designated components. An ordinal number greater than one does not necessarily imply that another such component must be present.

[0014] It should first be understood that all quantities with regard to the powder material used or the powder material mixture, as well as the coating system according to the present invention, are to be understood in the stated amounts as weight percent [wt.%] based on the total weight of the corresponding powder material or the matrix alloy of the coating system. It should also be understood that iron serves as the base material of the powder material in the coating system and is preferably included in a balanced form.

[0015] It should be expressly noted that the wt. % does not refer to the finished coating system with the separately added carbide particles. Compared to a (for example, glass fiber) reinforced plastic, the separately added carbide particles correspond to the reinforcing material, while the matrix alloy forms the matrix in which the separately added carbide particles are embedded. The carbide particles are classified as hard material particles.

[0016] Furthermore, it should be noted that the separately added carbide particles are not formed during the welding process by means of the so-called carbide formers, but already as carbide particles (for example elementally pure and / or in a chemical compound), for example as titanium carbide [TiC], tungsten carbide [WC], vanadium carbide [VC], chromium carbide [Cr x C y] or others are added to the coating system. The mass of the carbide particles varies greatly; for example, titanium carbides are much lighter than tungsten carbides. These are therefore specified in volume percent [vol.%] with reference to the respective layer or to the entire coating system. In a preferred embodiment, the mixing zone is free of separately added carbide particles; thus, no separately added carbide particles are present there.

[0017] Percentages used in the preceding and following descriptions are to be understood as weight percent of the specified matrix alloy of a respective layer, unless another definition (e.g. volume percent [vol.%]) is explicitly stated.

[0018] The alloy of the coating system itself, which can be formed using the matrix alloy of the welding material shown here (i.e., without the separately added carbide particles), already exhibits excellent wear and / or abrasion resistance. This is largely due to the carbides, and sometimes also borides, formed in the coating system as a result of the carbide formers present (primarily niobium, titanium, and / or vanadium). At the same time, this welding material makes it possible to form the coating system by applying the welding material directly to the base body during build-up welding. The established standard to date has been that a mediating primer (a so-called adhesion layer, bonding layer, or buffer layer) must first be applied.With a single welding material or a single layer on the base body, shorter process times, lower susceptibility to errors, thinner layer thicknesses and, if necessary, a smaller number of layers, i.e. less frequent repeated applications, can be achieved to create the (single) layer of the coating system.

[0019] It should be noted that, as used herein, a layer refers to a material area of ​​the same chemical composition or a (possibly multi-layer) application of chemically identical welding consumable. In the latter case, the areas of the respective dilution zones with adjacent material are ignored; for example, a layer is defined up to the middle of a respective dilution zone.

[0020] Furthermore, it should be noted that a layer is formed as a single application in a single pass from start to finish, for example in the case of a friction surface of a brake disc from radially inside to outside or vice versa. Interruptions in the application between the start and finish due to the process or a result to be achieved are not significant. In another definition, a single layer is an application which is applied to a surface that is cold from a welding point of view and cools down to form a new surface (without the further addition of welding energy). In one embodiment, a single layer is not necessarily formed to cover a surface. In one embodiment, a single layer is not necessarily formed by a single welding device.

[0021] The result is a coating system in the form of a corrosion-resistant, naturally hard alloy, combining the properties of corrosion protection and wear protection. The use of different carbide formers with different precipitation kinetics and thus different distributions results in good resistance to wear particles (e.g., dirt or carbide particles released between the brake disc and brake pad) of various sizes.

[0022] It is therefore proposed here that carbide particles, and possibly other hard material particles, be added to the coating system (preferably as a component of the powder material). It has been determined that these hard material particles do not participate in the welding process, i.e., they are not melted. It should be noted that with very small grain sizes, hard material particles are certainly melted or even vaporized. However, this proportion is negligible. For example, such hard material particles of a desired grain size are only melted on the surface or heated during the build-up welding process.

[0023] In a supplementary embodiment, hard material particles are additionally added depending on the layer of a plurality of layers (forming the coating system). In this case, a different amount of or exclusively in at least one of the layers is present in different layers. Preferably, the bottommost (i.e., closest to the base body) layer or a plurality of (adjacent) bottom layers, including the very bottom layer, is free of separately added carbide particles, preferably free of hard material particles, i.e., no carbide particles or hard material particles are embedded. Alternatively or additionally, the topmost (i.e., outer) layer or a plurality of (preferably adjacent) top layers, preferably including the very topmost layer, is free of separately added carbide particles, preferably free of hard material particles, i.e., no carbide particles or hard material particles are embedded.

[0024] In one embodiment, the carbide particles are added separately in a proportion of the entire layer in question of at least 20 vol.% [twenty volume percent] to 70 vol.%, preferably of at least 35 vol.% to 70 vol.% or 20 vol.% to 60 vol.%, particularly preferably of 40 vol.% to 50 vol.%. In a preferred embodiment, the separately added carbide particles are larger than 1 μm [one micrometer], particularly preferably larger than 1.5 μm [fifteen tenths of a micrometer].

[0025] According to one embodiment, the volume percent is measured according to the amount of welding filler material added. In one embodiment, the volume percent is measured according to the microscopically detectable number and their volume fraction in a micrograph of a formed coating system, wherein preferably only those carbide particles with a grain size greater than 1 pm, particularly preferably greater than 1.5 pm, are regarded as separately added. Metallographic analyses known from the prior art are used for this purpose. In particular, after preparation and etching under the light microscope, the number of carbide particles and preferably the area fraction can be determined directly by visual inspection, optionally with computer-assisted image recognition. The area fraction corresponds to the volume percent.

[0026] In one embodiment, the volume percentage is determined based on a (preferably microscopic) examination of an outer surface of a finished coating system. The area fraction is equated to the volume fraction, at least when the layer forming the outer surface is provided with separately added carbide particles. If the layer forming the outer surface is free of separately added carbide particles, the protruding carbide particles and elevations in the otherwise smooth outer surface are counted and multiplied by an area factor, where the area factor corresponds, for example, to the square of the average grain diameter multiplied by TT / 2 [half the number of pi]. Alternatively, the area factor is another mathematical-statistical approximation of the area or volume of an average carbide particle.In one embodiment, the manufacturer's specifications are used as the mean grain diameter. In one embodiment, individual carbide particles are released from the coating system, and they themselves and / or the remaining hole, or holes already created as a result of use (by releasing particles), are measured for their diameter and / or their respective area. The average is calculated from the diameters or areas of the randomly selected carbide particles and / or holes. The calculated product corresponds to the volume fraction. This method for determining the volume percentage can be used regardless of the type of layer forming the outer surface.

[0027] It should be noted that in one embodiment, the material of the coating system described here, or the matrix alloy in the welding consumable, is provided as an alloy of the welding material, for example as a wire or powder. The powder material does not necessarily have to have the described composition in every powder particle; it may even differ significantly, provided that different base materials are combined to form a powder mixture or are combined in situ. In one embodiment, the desired separate carbide particles (and optionally other hard material particles) are added to the welding consumable. However, as particles not participating in the welding process, these are not counted as part of the welding material, but are referred to as separately added particles.

[0028] Powder material or powder material mixture, as used herein, preferably refers to the welding material with which the coating system of the base body is created. It should be understood that the welding material is preferably reserved for build-up welding as a powder material for powder build-up welding.

[0029] Balanced as used herein preferably means that the amount of iron is adjusted accordingly (to make up 100%) to achieve the specified weight percent of other components, so that the main component of a coating system proposed herein is an iron-based alloy.

[0030] This coating system represents a cost-effective coating system for a base body compared to a coating known from the prior art. This is achieved primarily by the use of niobium, titanium and / or vanadium, preferably by avoiding relatively expensive components and using a very small amount of these compared to previously known coatings.

[0031] The present inventors have surprisingly found that the coating system proposed here additionally has advantageous properties for its use and is not excessively prone to cracking and / or pore formation, shows a generally high corrosion resistance and good bonding of the weld layers, and has a hardness advantageous for its use.

[0032] In a preferred embodiment of the base body with the coating system, the matrix alloy of the coating system comprises: iron; and preferably from 0.5 to 15.0 wt.% vanadium; and preferably at most 4.0 wt.% niobium; and further preferably at most 0.35 wt.% titanium; and further preferably at most 0.3 wt.% nickel; and further preferably from 0.3 to 3.0 wt.% carbon; and further preferably from 10 wt.% to 26 wt.% chromium; and further preferably from 1.0 to 10 wt.% manganese; and further preferably from 0.05 to 1.0 wt.% molybdenum; and further preferably from 0.25 to 1.25 wt.% silicon; and further preferably at most 0.75 wt.% tungsten; and further preferably at most 0.15 wt.% phosphorus; and further preferably at most 0.25 wt.% sulfur; and further preferably from 0.01 to 0.5 wt.% nitrogen; and more preferably 0.01 to 0.09 wt% oxygen.

[0033] The present inventors have surprisingly found that the coating system proposed herein can be prepared using vanadium. Vanadium [V] is a relatively inexpensive component compared to tungsten [W], niobium [Nb], and / or titanium [Ti]. Vanadium, titanium, and / or niobium serve primarily as carbide formers in the coating system.

[0034] With the use of vanadium, more expensive components such as niobium and titanium can be used in significantly smaller quantities. Preferably, the welding material should not contain niobium or titanium, at least not beyond the usual impurities.

[0035] It was surprisingly discovered that the property profile of corresponding alloys can be precisely tailored through the balanced addition of monocarbide formers such as vanadium. Through fine distribution (finely dispersed precipitation of primary vanadium carbide), combined with grain refinement effects, the crack length of the often heavily cracked weld layers can be shortened. Impact wear stresses thus no longer lead to immediate breakouts. This offers advantages in abrasive and impact wear stresses. A further advantage lies in the extremely high hardness and high melting point of vanadium carbide, which ranks in the range of titanium carbide and above tungsten carbide.Vanadium carbide has a hardness of 2950 HVo,oi [two thousand nine hundred and fifty Vickers hardness], with a test force of 0.102 kp [one hundred and two thousandths of a kilopond] and a standard loading time of 10 s [ten seconds] to 15 s and a melting point of 2830 °C [two thousand eight hundred and thirty degrees Celsius].

[0036] The resulting mixed carbides of the (Cr, Fe) 7C3 type have a hardness of 1700 HV10 [1,700 Vickers hardness] to 2100 HV10. Boron hardens the (Cr, Fe) 7C3 carbides at a content of approximately 0.6% or more. The most important hard materials besides Cr7C3 are the chromium carbides Cr3C2 and Cr23C6. The Cr7C3 and Cr23C6 carbides, which exhibit a needle-like to plate-like microstructure, have proven particularly effective under abrasive wear.

[0037] In addition, the addition of manganese [Mn] and silicon [Si] leads to an increase in the wear resistance of the applied coating system (in addition to a typically significant improvement in the welding properties due to the high oxygen affinity and thus to deoxidation).

[0038] A higher vanadium content, in particular, can increase the hardness of the coating system. However, too high a vanadium content can lead to excessive strain on the lattice.

[0039] It should be noted that the comparisons listed here are made to a composition with a lesser or a moreer of the respective element in the coating system. It is at least correct that a lesser or moreer of this element is present as a basis due to a corresponding more or lesser amount of iron [Fe]. Alternatively or additionally, a moreer or lesser amount of another of the mentioned elements is present in a considerable amount within the stated quantities. This is explicitly pointed out in some examples, provided that the respective element can be used as a substitute. However, it is also within the skill of the art, at least on the basis of the explanations listed here, to use a suitable alloy within the scope of the invention proposed here in which the elements are present in a combination that is not listed here as an explicit example.

[0040] The more vanadium is used, the more additional carbide formers, such as niobium and titanium, but also molybdenum, can be dispensed with. It should be noted that replacing the other carbides in equal quantities is not necessary here, because vanadium carbide is very finely dispersed and, due to its high hardness and high melting point, is considered one of the highest quality carbides.

[0041] Such a coating system preferably comprises at least 0.75 wt.%, more preferably at least 1.0 wt.%, more preferably at least 1.6 wt.%, more preferably at least 2.5 wt.%, and more preferably at least 5.0 wt.% vanadium.

[0042] At the same time, a relatively low vanadium content is advantageous because it reduces the tendency to crack. However, too low a vanadium content can be disadvantageous because sufficiently high hardness may not be achieved.

[0043] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system comprises at most 15 wt.%, preferably at most 12.5 wt.%, more preferably at most 12 wt.% and more preferably at most 10 wt.% vanadium.

[0044] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system comprises: preferably from 0.5 to 15.0 wt.%, more preferably from 0.75 to 15.0 wt.%, more preferably from 1.0 to 15.0 wt.%, more preferably from 1.6 to 15.0 wt.%, more preferably from 2.5 to 15.0 wt.%, more preferably from 5.0 to 15.0 wt.%, more preferably from 0.5 to 12.5 wt.%, more preferably from 0.75 to 12.5 wt.%, more preferably from 1.0 to 12.5 wt.%, more preferably from 1.6 to 12.5 wt.%, more preferably from 2.5 to 12.5 wt.%, more preferably from 5.0 to 12.5 wt.%, more preferably from 0.5 to 12.0 wt.%, more preferably from 0.75 to 12.0 wt.%, more preferably from 1.0 to 12.0 wt.%, more preferably from 1.6 to 12.0 wt.%, more preferably from 2.5 to 12.0 wt.% and more preferably from 5.0 to 12.0 wt.%, preferably from 0.5 to 10.0 wt.%, more preferably from 0.75 to 10.0 wt.-%, more preferably from 1.0 to 10.0 wt.%, more preferably from 1.6 to 10.0 wt.%, more preferably from 2.5 to 10.0 wt.% and more preferably from 5.0 to 10.0 wt.% vanadium.

[0045] In an advantageous embodiment, the coating system comprises a proportion of niobium. A proportion of niobium is present in the coating system as a carbide former.

[0046] At the same time, a relatively low proportion of niobium is advantageous in order to keep the costs of the coating system low.

[0047] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further comprises at most 4.0 wt.% niobium. In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further comprises: preferably at most 3.5 wt.%, further preferably at most 3.0 wt.%, further preferably at most 2.0 wt.%, further preferably at most 1.0 wt.%, further preferably at most 0.75 wt.%, further preferably at most 0.5 wt.%, further preferably at most 0.25 wt.%, further preferably at most 0.1 wt.% and further preferably at most 0.01 wt.% niobium.

[0048] In an advantageous embodiment, the coating system comprises a proportion of titanium.

[0049] A proportion of titanium is present in the coating system as a carbide former and / or corrosion protection element. At the same time, a relatively low titanium content is advantageous in keeping the cost of the coating system low.

[0050] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further comprises at most 0.4 wt.% titanium.

[0051] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system preferably further comprises at most 0.35 wt.%, further preferably at most 0.25 wt.%, further preferably at most 0.1 wt.% and further preferably at most 0.01 wt.% titanium.

[0052] In an advantageous embodiment, the coating system comprises a proportion of nickel.

[0053] Nickel [Ni] in the coating system serves primarily to increase corrosion protection. A higher nickel content also improves weldability. At the same time, a relatively low nickel content is advantageous for minimizing the amount of harmful substances and for complying with more modern standards, such as the REACH regulation.

[0054] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further comprises at most 0.5 wt.% nickel, preferably at most 0.3 wt.%, at most 0.2 wt.%, further preferably at most 0.1 wt.% and further preferably at most 0.01 wt.% nickel.

[0055] In an advantageous embodiment, the coating system comprises a proportion of carbon [C].

[0056] Carbon serves primarily as a carbide former in the coating system. A higher carbon content can be detrimental to weldability. At the same time, a higher carbon content can advantageously increase hardness. Likewise, a relatively low carbon content is advantageous for improving weldability. Likewise, a relatively low carbon content advantageously reduces crack formation.

[0057] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system preferably further comprises at least 0.3 wt.% carbon.

[0058] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system preferably further comprises at least 0.5 wt.%, more preferably at least 0.75 wt.%, more preferably at least 1.0 wt.% and more preferably at least 1.5 wt.% carbon.

[0059] Such a high carbon content is beneficial for austenite formation. It should be noted that a high proportion of the carbon in the powder material reacts during the buildup welding process and does not reach the coating system alloy, for example, due to atmospheric oxygen penetration. For example, in the coating system alloy, with the aforementioned amount in the weld material, a carbon content of 0.5% to 1.5% by weight is achieved.

[0060] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at most 4.5 wt.%, further preferably at most 3.0 wt.%, further preferably at most 2.5 wt.% and further preferably at most 2.0 wt.% carbon.

[0061] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system comprises: more preferably from 0.3 to 5 wt.%, more preferably from 0.5 to 5 wt.%, more preferably from 0.75 to 5 wt.%, more preferably from 1.0 to 5 wt.%, more preferably from 1.5 to 5 wt.%, more preferably from 0.3 to 4.5 wt.%, more preferably from 0.5 to 4.5 wt.%, more preferably from 0.75 to 4.5 wt.%, more preferably from 1.0 to 4.5 wt.%, more preferably from 1.5 to 4.5 wt.%, more preferably from 0.3 to 3.0 wt.%, more preferably from 0.5 to 3.0 wt.%, more preferably from 0.75 to 3.0 wt.%, more preferably from 1.0 to 3.0 wt.%, more preferably from 1.5 to 3.0 wt.%, more preferably from 0.3 to 2.5 wt.%, more preferably from 0.5 to 2.5 wt.%, more preferably from 0.75 to 2.5 wt.%, more preferably from 1.0 to 2.5 wt.%, more preferably from 1.5 to 2.5 wt.-%, more preferably from 0.3 to 2.0 wt.%, more preferably from 0.5 to 2.0 wt.%, more preferably from 0.75 to 2.0 wt.%, more preferably from 1.0 to 2.0 wt.% and more preferably from 1.5 to 2.0 wt.% carbon.

[0062] In an advantageous embodiment, the coating system comprises a proportion of chromium.

[0063] Chromium is an important component for corrosion resistance, especially in aqueous solutions, such as (salt-containing) rainwater. In combination with molybdenum, it is particularly effective against pitting corrosion. The lower the proportion, the more cost-effective the welding material. However, too low a proportion of chromium can significantly impair corrosion resistance. Chromium in the coating system effectively prevents iron oxide formation, particularly in the presence of (low) oxygen exposure—especially during processing in a protective gas atmosphere. A proportion of chromium in the coating system advantageously provides increased corrosion protection and acts as a carbide former. In addition, chromium in the proposed welding material is a component for hard phase formation.

[0064] A higher proportion of chromium increases the corrosion resistance of the coating system in particular.

[0065] In another preferred embodiment of the base body with the coating system, the chromium is present freely in the matrix. This is particularly advantageous for ensuring corrosion protection. Bound chromium in the form of chromium carbides may not contribute to corrosion protection under certain circumstances. Those skilled in the art will recognize that vanadium is thus simultaneously used as a sacrificial element (at a sufficiently high level) in the coating system proposed here, so that carbon is advantageously bound to vanadium rather than to chromium.

[0066] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at least 10 wt.%, further preferably at least 12.5 wt.%, further preferably at least 13 wt.% and further preferably at least 15.0 wt.% chromium.

[0067] A proportion of at least 12.0 wt.% chromium in the coating system is particularly preferred.

[0068] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at most 25 wt.%, further preferably at most 20 wt.% chromium.

[0069] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises from 10 wt.% to 25 wt.%, further preferably from 12.5 wt.% to 25 wt.%, further preferably from 13 wt.% to 25 wt.%, further preferably from 15.0 wt.% to 25 wt.%, further preferably from 10 wt.% to 20 wt.%, further preferably from 12.5 wt.% to 20 wt.%, further preferably from 13 wt.% to 20 wt.%, further preferably from 15.0 wt.% to 20 wt.% chromium.

[0070] In an advantageous embodiment, the coating system comprises a proportion of manganese.

[0071] Manganese [Mn] in the coating system serves primarily to improve weldability, strength, and wear resistance, as well as to optimize hardenability. A pronounced balance of manganese is advantageous to avoid high proportions of brittle phases. The carbon, together with the manganese, supports the formation of austenite (the face-centered cubic lattice structure of an iron alloy) and thus the desired toughness of the coating system. The manganese component also acts as an effective work-hardening agent.

[0072] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at least 1.0 wt.%, further preferably at least 1.25 wt.% and further preferably at least 1.4 wt.% manganese.

[0073] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at most 10 wt.%, further preferably at most 7.5 wt.% and further preferably at most 6.5 wt.% manganese.

[0074] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises from 1.0 to 10 wt.%, further preferably from 1.25 to 10 wt.%, further preferably from 1.4 to 10 wt.%, further preferably from 1.0 to 7.5 wt.%, further preferably from 1.25 to 6.5 wt.%, further preferably from 1.4 to 6.5 wt.% and further preferably from 1.4 to 6.5 wt.%, of manganese.

[0075] In an advantageous embodiment, the coating system comprises a proportion of molybdenum. Molybdenum [Mo] in the coating system is particularly advantageous for improving weldability and fine grain formation. In addition to the properties described above, molybdenum provides corrosion resistance to non-oxidizing solutions, such as hydrochloric acid, which also occur in the environment in non-negligible quantities. Molybdenum is also a further carbide former. A higher molybdenum content therefore increases corrosion resistance in particular.

[0076] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at least 0.05 wt.%, further preferably at least 0.1 wt.% and further preferably at least 0.25 wt.% molybdenum.

[0077] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at most 1.0 wt.%, further preferably at most 0.75 wt.% and further preferably at most 0.6 wt.% molybdenum.

[0078] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises from 0.05 to 1.0 wt.%, further preferably from 0.1 to 1.0 wt.%, further preferably from 0.25 to 1.0 wt.%, further preferably from 0.05 to 0.75 wt.%, further preferably from 0.1 to 0.75 wt.%, further preferably from 0.25 to 0.75 wt.%, further preferably from 0.05 to 0.6 wt.%, further preferably from 0.1 to 0.6 wt.% and further preferably from 0.25 to 0.6 wt.% molybdenum.

[0079] In an advantageous embodiment, the coating system comprises a proportion of silicon.

[0080] A higher proportion of silicon [Si] advantageously increases the wear resistance and strength of the coating system.

[0081] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at least 0.1 wt.% silicon. In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at least 0.25 wt.%, further preferably at least 0.3 wt.%, and further preferably at least 0.5 wt.% silicon.

[0082] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at most 1.25 wt.%, further preferably at most 1.0 wt.% and further preferably at most 0.7 wt.% silicon.

[0083] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises from 0.25 to 1.25 wt.%, further preferably from 0.3 to 1.25 wt.%, further preferably from 0.5 to 1.25 wt.%, further preferably from 0.25 to 1.0 wt.%, further preferably from 0.3 to 1.0 wt.%, further preferably from 0.5 to 1.0 wt.%, further preferably from 0.25 to 0.7 wt.%, further preferably from 0.3 to 0.7 wt.%, and further preferably from 0.5 to 0.7 wt.% silicon.

[0084] In an advantageous embodiment, the coating system comprises a proportion of tungsten.

[0085] Even in very small amounts, tungsten [W] is beneficial as a carbide former (e.g., for a highly abrasion-resistant and / or highly heat-resistant surface). However, even in small amounts, it is particularly beneficial as a solid solution strengthener and for the high-temperature resistance of the coating system.

[0086] Tungsten carbides have proven to be an effective hard material additive in the state of the art, particularly in so-called dual-layer systems. They significantly increase the hardness of a welded layer. The disadvantage is that they complicate the welding process because an even distribution of the carbides in the melt must be ensured. In addition, melting of the carbides should be prevented in order to utilize the technological advantage of the carbides and reduce the risk of matrix embrittlement. Furthermore, their high price poses a problem for economic viability. A higher proportion of tungsten, in particular, advantageously increases the high-temperature strength of the coating system. Tungsten also serves advantageously as a carbide former. However, a high proportion of tungsten can be uneconomical due to high material costs.

[0087] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at most 0.75 wt.%, further preferably at most 0.6 wt.%, further preferably at most 0.5 wt.%, further preferably at most 0.25 wt.%, further preferably at most 0.05 wt.%, and further preferably at most 0.01 wt.% tungsten.

[0088] In an advantageous embodiment, the coating system comprises a proportion of phosphorus.

[0089] A relatively low proportion of phosphorus [P] is advantageous because phosphorus is a detrimental pest to steel.

[0090] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at most 0.15 wt.%, further preferably at most 0.1 wt.%, further preferably at most 0.05 wt.%, and further preferably at most 0.25 wt.% phosphorus.

[0091] In one embodiment, the coating system comprises a proportion of sulfur.

[0092] A relatively low sulfur [S] content is advantageous. Those skilled in the art will recognize that sulfur is bound by manganese.

[0093] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system more preferably comprises at most 0.25 wt.%, more preferably at most 0.1 wt.%, and more preferably at most 0.01 wt.% sulfur. In one embodiment, the coating system comprises a proportion of nitrogen.

[0094] Nitrogen-alloyed steels are increasingly being used in the state of the art. However, the skilled person will generally consider nitrogen to be a steel pollutant and keep the nitrogen [N] content as low as possible. Nitrogen can be used as an alloying component.

[0095] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at most 0.5 wt.%, further preferably at most 0.25 wt.%, and further preferably at most 0.1 wt.% nitrogen.

[0096] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises at least 0.01 wt.%, further preferably at least 0.02 wt.% and further preferably at least 0.05 wt.% nitrogen.

[0097] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises from 0.01 to 0.5 wt.%, further preferably from 0.02 to 0.5 wt.%, further preferably from 0.05 to 0.5 wt.%, further preferably from 0.01 to 0.25 wt.%, further preferably from 0.02 to 0.25 wt.%, further preferably from 0.05 to 0.25 wt.%, further preferably from 0.01 to 0.1 wt.%, further preferably from 0.02 to 0.1 wt.%, further preferably from 0.05 to 0.1 wt.% nitrogen.

[0098] In one embodiment, the coating system comprises a proportion of oxygen.

[0099] A relatively low proportion of (elemental) oxygen [O] is advantageous because it can lead to embrittlement and other negative properties. It is worth mentioning that some of the other alloy components described may also have a deoxidizing effect. Those skilled in the art will recognize that oxygen should be avoided, and other alloy components can also be designed to counteract oxygen contamination.

[0100] In a further preferred embodiment of the base body with the coating system, the matrix alloy of the coating system further preferably comprises 0.01 to 0.09 wt.% oxygen.

[0101] It should be understood that the coating system according to the present invention can be suitable for coating any base body that requires wear and corrosion protection. Within the context of the present invention, the term "base body" preferably refers to a component that requires wear and corrosion protection.

[0102] The present inventors have further surprisingly discovered that the coating system proposed herein can be used as a single-layer coating system, i.e., can be applied directly to the base body. This significantly simplifies the process for producing coated base bodies and thus makes them more cost-effective.

[0103] It is further proposed in an advantageous embodiment of the base body that the coating system is formed in a single layer.

[0104] The single-layer coating system as used herein preferably refers to a coating system which is applied as a single layer to the surface of the base body to be coated, without the use of a primer.

[0105] This does not mean (as already explained above) that such a layer is or has necessarily been welded on in a single pass. It is known to those skilled in the art that the presence of a single-layer coating can be determined from a cross-sectional image. Metallographic analyses known from the prior art are used for this purpose. In particular, after preparation and etching under the light microscope, the number of layers can be determined directly by visual inspection. It should be understood that, in comparison to coating systems described in the prior art, the single-layer coating consists of the actual functional layer, which is usually referred to as the friction layer when used in brake discs and similar applications, and is not applied to a primer.

[0106] Experts know that materials differ in their weldability. One criterion in this regard is the material's carbon content. Generally speaking, the higher the carbon content, the more difficult a material is to weld. In order to weld a layer made from or onto a material that is difficult to weld, it is therefore already recommended in the state of the art to first weld a primer. This bonding layer made of an easily weldable material is placed between the substrate (the surface of the base body to be coated) and the weld seam that actually creates or enables the desired properties of the newly formed outer surface. The material of the bonding layer is selected so that it can both achieve a fusion-metallurgical bond to the substrate and create a bond to the layer above.

[0107] In an advantageous embodiment of the base body, it is further proposed that the coating system be formed in multiple layers, wherein at least a first layer is formed without separately added carbide particles, and wherein at least one layer arranged further up, preferably a penultimate and / or last layer, is formed from the matrix alloy with the separately added carbide particles. Preferably, the at least one first layer, and optionally a last layer, is formed from the matrix alloy, further preferably the matrix alloys of the first layer and the layer with the separately added carbide particles, particularly preferably of all layers, are identical.

[0108] In this embodiment, preferably no primer is provided or such a primer is formed (at the bottom) by a first layer according to the above description. This (at least one) first layer is preferably formed with a matrix alloy according to the description here, particularly preferably without separately added carbide particles. The matrix alloy of this at least one first layer and the further layer containing carbide particles is not necessarily identical. For example, in the at least one first layer applied directly to the surface of the base body to be coated, preferably all of the first layers, the proportion of chromium [Cr], carbide formers or other elements tending to embrittlement is lower than in the layer containing carbide particles.

[0109] In one embodiment, for example, a first layer is formed as a primer (multi-layer or single-layer) consisting of at least one layer of the matrix alloy, then a second layer (multi-layer or single-layer) consisting of at least one layer with separately added carbide particles with the (chemically identical or different) matrix alloy, and finally a third layer as an outer surface (for example the friction surface of a brake disc) consisting of at least one layer of the matrix alloy (chemically identical or different to the first layer and / or second layer) free of separately added carbide particles. Alternatively, the first layer and / or third layer are omitted, i.e. only a first layer and a second layer or only a second layer and a third layer or only a second layer are formed, preferably in each case without a primer.

[0110] It is further proposed in an advantageous embodiment of the base body that at least the layer with the matrix alloy and the separately added carbide particles of the coating system is applied by means of high-speed laser deposition welding, preferably with an area rate of at least 500 cm 2 / min to a reference layer thickness of 100 pm.

[0111] The coating system is provided by a method for coating a base body with a coating system according to the preceding description and / or a powder material mixture according to the following description, by means of build-up welding, for example LA and / or HVLA at an area rate of at least 500 cm 2 / min [five hundred square centimeters per minute],

[0112] It should be understood that an area rate of at least 500 cm 2 / min, preferably at least 850 cm 2 / min makes the coating process particularly economical. An area rate is preferably standardized here to a layer height of 100 pm [one hundred micrometers]. This means that if a lower layer height is desired, a higher area rate can be achieved, for example, by increasing the feed rate with otherwise identical process parameters. In embodiments in which the coating system is designed as a single-layer coating system, a significant increase in cost-effectiveness can be achieved compared to a two-layer system with similar area rates, because the production of two-layer coatings known from the prior art takes longer due to the correspondingly larger number of layers and / or a necessary conversion of the device for a different powder material. It should be understood, however, that the coating system proposed here is not limited to being designed as a single-layer coating.

[0113] It is further proposed in an advantageous embodiment of the base body that the coating system has a hardness of 300 HVo.oi to 1100 HVo.oi.

[0114] In one embodiment, the coating system preferably has a hardness of at least 350 HVo.oi, more preferably at least 400 HVo.oi, more preferably at least 450 HVo.oi, and more preferably at least 500 HVo.oi. In one embodiment, the coating system preferably has a hardness of at most 700 HVo.oi, and more preferably at most 600 HVo.oi.

[0115] A higher hardness advantageously achieves improved wear resistance of the coating. At the same time, excessive hardness can promote undesirable cracking. It should be noted that in one embodiment, the specified values ​​refer to the pure welding material, i.e., the matrix alloy exhibits the stated hardness without separately added carbide particles. In one embodiment, high values, for example, 1100 HVo.oi, are determined statistically averaged, with the hardness measured on a carbide particle and the hardness measured on the matrix alloy being calculated weighted according to the area fraction and / or volume percent.

[0116] In an advantageous embodiment of the base body, it is further proposed that the proportion of separately added carbide particles comprises at least 35 vol.%, preferably at least 40 vol.%, more preferably at least 50 vol.%. Preferably, the separately added carbide particles are selected from titanium carbides and / or tungsten carbides, and particularly preferably, the separately added carbide particles are exclusively titanium carbides.

[0117] The lower the volume fraction of separately added carbide particles, the more cost-effective the coating system. The more separately added carbide particles, the better the wear resistance of a friction surface. Furthermore, it has been shown that braking behavior, i.e., the response (the so-called sharpness of braking), improves with the increasing number of separately added carbide particles.

[0118] Titanium carbides are particularly cost-effective. Tungsten carbides are suitable for higher temperatures, for example, for a coating system on a brake disc for a sports car's braking system.

[0119] It is further proposed in an advantageous embodiment of the base body that the base body is a gray cast iron base body and / or a brake disc.

[0120] The skilled person will immediately recognize that such a base body, which is exposed to increased wear, friction, or other mechanical stresses, can benefit from the coating system. The coating system is particularly advantageous for base bodies that serve as braking devices, such as brake discs. Brake discs are exposed to particularly high levels of wear and corrosion. The coating system proposed here counteracts wear and corrosion particularly advantageously and protects the base body. Furthermore, the coating system advantageously creates a base body that also achieves particularly advantageous particulate matter reduction, such as that required, for example, by ELIRO7.

[0121] It is further proposed in an advantageous embodiment of the base body that the carbide particles have a grain size window of 6 pm to 120 pm, preferably comprising at least one, particularly preferably exclusively one, of the following separate grain size windows:

[0122] - 3 pm to 4 pm; and

[0123] - 45pm to 90pm, preferably until 106pm.

[0124] The grain size window specified here is a balance between the required layer thickness or overall thickness of the coating system and a good strengthening effect. If the grain size window is too large, statistically some carbide particles will no longer be able to be effectively bonded into the matrix alloy and will detach from the matrix alloy under load. This, in turn, can lead to adverse results in applications such as the friction surface of a brake disc, if such released carbide particles eat into a brake pad and thus cause scoring in the friction surface of the brake disc. If the grain size window is too small, the desired results in terms of wear resistance will not be achieved.

[0125] However, it has also been found that with increasing grain size, the volume fraction of separately added carbide particles can be reduced. This allows cost advantages to be achieved in applications other than brake discs.

[0126] It was also found that with a large grain size range, the advantages of high hardness and good braking performance (see above), which are particularly relevant for a friction surface, can be achieved very well at the same time. According to a further aspect, a powder material mixture for a coating system of a base body according to an embodiment as described above is proposed, wherein the powder material mixture contains the elements of the matrix alloy and the carbide particles to be added separately.

[0127] The powder material mixture proposed here makes it possible to produce the coating system proposed above. At the same time, it is particularly simple and therefore cost-effective because the powder material mixture already contains the carbide particles that need to be added separately, eliminating the need for separate addition.

[0128] According to a further aspect, a method for coating a base body according to an embodiment according to the above description and / or a powder material mixture according to an embodiment according to the above description is proposed, wherein at least one, preferably all, of the layers are applied by means of deposition welding, preferably laser deposition welding, particularly preferably high-speed laser deposition welding, preferably with an area rate of at least 500 cm 2 / min to a reference layer thickness of 100 pm.

[0129] Reference is made to the previous description of the coating system, at least with regard to the coating process. It should be noted that although laser cladding requires less energy, the energy intensity of, for example, high-velocity oxyfuel spraying [HVOF] can reach similar values ​​and is therefore suitable for creating a coating system, for example using the powder material mixture described above. The advantages of laser cladding, particularly high-speed laser cladding [HVLA], are the quality and lower achievable layer thickness of the coating system, so that not only less energy is required for the respective welding process, but also less material and, under certain circumstances, in a shorter time, and thus again less energy consumption. The specific advantages, however, depend heavily on the specific application.

[0130] The invention described above is explained in detail below against the relevant technical background with reference to the accompanying drawings, which show preferred embodiments. The invention is in no way limited by the purely schematic drawings, whereby it should be noted that the drawings are not to scale and are not suitable for defining proportions. It is shown in

[0131] Fig. 1 : a coating device with a base body;

[0132] Fig. 2: a section of a schematic micrograph of a coated base body;

[0133] Fig. 3: a micrograph of an embodiment according to Example No. 3;

[0134] Fig. 4: Example No. H according to Table 1;

[0135] Fig. 5: Example No. W according to Table 1;

[0136] Fig. 6: a coating system on a brake disc;

[0137] Fig. 7: an alternative coating system on a brake disc;

[0138] Fig. 8: an enlargement of the micrograph from Fig. 3;

[0139] Fig. 9: a hardness measurement according to Vickers;

[0140] Fig. 10: first brake discs before and after a corrosion resistance test;

[0141] Fig. 11 : second brake discs before and after a corrosion resistance test; and

[0142] Fig. 12: a micrograph of the right brake disc according to Fig. 11.

[0143] Fig. 1 shows a schematic view of a coating device 10 with a base body 1, for example a brake disc 7. The coating device 10 shown here comprises (here two) storage containers 15 for the welding material, for example for a powder mixed from two powder components. The powder is, for example, partly metallic and partly an additive, for example hard material particles, which are used, for example, in a friction coating of a brake disc 7. A supply line 16 is connected to the storage containers 15 and opens into a feed device 12, here an annular gap nozzle. Here, it is optionally shown that a flow measurement 17 is arranged at a bypass line 18 and thus the flow in the supply line 16 (extrapolated from the data of the bypass line 18) can be recorded by means of the flow measurement 17.The feed device 12 (here an annular gap nozzle) is aligned such that the (here powdery) welding material can be fed into a focus and the focus can be moved in a defined manner by means of a feed actuator 13 (here only schematically indicated for a single feed direction in the image plane from right to left). The coating device 10 further comprises a welding device 11, here for example a laser for LA, preferably for HVLA. The welding device 11 is configured such that the welding material (here by the laser) is melted or molten in the focus, so that the welding material (preferably in a molten pool) impinges on the surface 21 of the base body 1 to be coated in the region (as shown) below the focus and thus (after curing) a coating is formed on the workpiece.

[0144] Fig. 2 schematically shows a section of a micrograph of a coated base body 1, for example a brake disc 7. A coating system 2 is formed with several (purely optionally two) layers 3, 4. The bottom (first) layer 3 is formed solely from the matrix alloy 5. The upper or outer (second) layer 4 is formed from a matrix alloy 5 and separately added carbide particles 6, which are shown here in different grain sizes as a representation of the grain size window 8. Preferably, the second layer 4 is produced directly from a premixed powder material mixture 9 as a welding filler material.

[0145] Production of embodiments

[0146] The powder material is used in an HVLA process using a device, as shown schematically in Fig. 1, and applied as a coating to a gray cast iron base body. The hard material particles used, which improve wear protection, are to be replaced by naturally hard materials. The iron-based alloy is to replace the tungsten carbide used in the prior art as the hard material. For the PS, if present, a matrix alloy as described above is used, for example. It should be noted that the powder material mentioned here can be applied directly to the surface of the gray cast iron base body to be coated or to a previously applied PS (also referred to as HS). It is irrelevant whether the respective layer is formed in a single pass or in several passes (i.e., multi-layered).With suitable process control, the weld layers and thus their number in a single layer with a single powder material are no longer discernible. The number of layers in a layer is determined for a required minimum thickness and / or for guaranteed coverage due to the track width of the laterally rounded weld beads caused by the process.

[0147] To conduct various comparative experiments, (working) examples 1 to 9 of the present coating were prepared and analyzed for their chemical composition. The results of the chemical analysis are shown in Table 1.

[0148] Table 1 - Chemical analysis of welding material applied as a coating on a base body in weight percent

[0149] Table 1 shows working examples No. 1 to No. 9 of the present invention, as well as No. W and No. H, which are considered limitations and not part of the invention. These examples were analyzed for their composition by chemical analysis. Table 1 shows the composition by element and in weight percent. Iron (Fe) is present in a balanced (bal) amount.

[0150] Production of designs according to two-layer model

[0151] In a two-layer model, coatings according to the present invention are applied to the PS (also referred to as HS) as a functional layer (in this case designed as a friction layer), which comprise a high proportion of titanium carbides. The PS here is an AISI 316 steel. The friction layer is the coating proposed here, namely in this example according to Example No. 2 above (see Table 1). In Table 2 below, various examples (Nos. 10 to 13) are shown and compared with each other with regard to their properties in use with a gray cast iron brake disc. Table 2 describes the layers, as well as the carbide content and the grain size of the carbides in the carbide content. The carbide content in Table 2 refers to those carbides which are added during the welding process (using HVLA) in addition to the powder material applied as a friction layer.It should be understood that this does not refer to the carbides present in the powder material as described above or those formed during the welding process. It should be noted that these additional carbides are introduced into the powder focus and thus directly into the liquid material. The carbides themselves, provided they have the specified grain size, are not melted in the process because their respective intrinsic melting temperatures are significantly higher than the process temperatures. The carbides are available as powder material with the specified grain size or grain size range.

[0152] Table 2 - List of examples of coatings containing carbides

[0153] PS in Table 2 stands for the buffer layer, which is made of the AISI 316 steel specified below. RS in Table 2 stands for the functional layer, i.e., the friction layer, which is mixed with the respective carbide, i.e., 50 wt.% in the respective layer, or (in examples No. 10 and No. 11)

[0154] 60 wt.%. The carbides are TiC [titanium carbide]. Alternatively, WC [tungsten carbide] is used partially or partially as a replacement. The grain size windows can be viewed as approximately a Gaussian distribution, with a negligible amount of the powder being smaller than the minimum value and larger than the maximum value of the grain size window. The grain size windows are usually achieved by sieving. Example product from manufacturers such as Durum Verschleißschutz GmbH, HC Starck Tungsten GmbH, Gesellschaft für Wolfram Industries mbH or Höganäs Germany GmbH. The PS is made of a material commonly referred to as austenitic stainless steel. It is alloy 1 .4404, also known as 316L or AISI 316, which has very good corrosion resistance due to its high chromium and molybdenum content combined with a low carbon content.The strength in the annealed state is approximately 600 MPa [600 megapascals] for large diameters, but can be increased for smaller sections through cold working. RS_1 denotes the friction layer, which is made of stainless steel, here more specifically alloy 1.4016 or 430L. RS_2 (in examples 11 and 12) denotes the friction layer, which is made of the same material as the PS. The values ​​are specified according to DIN EN 10095:2018, Appendix D.

[0155] RS_3 denotes the friction layer (in example no. 13), which is made of the material of example no. 2 (see Table 1).

[0156] Test results

[0157] A performance test was conducted for exemplary embodiments 10, 11, 12, and 13 according to Table 2 using the two-shift model. The performance test was conducted in accordance with the so-called WLTP standard. WLTP (Worldwide Harmonized Light Vehicles Test Procedure) is an international EU driving cycle standard, valid from September 1, 2017, in the version valid on the filing date. The result will be positive for embodiments according to the present invention.

[0158] Table 3 - Overview of the performance of the examples shown in Table 2

[0159] Table 3 shows the results of the performance test. The symbol "O" represents average performance, the symbol "-" represents poor performance, the symbol "--" represents very poor performance, and the symbol "+" represents good to very good performance.

[0160] The evaluation criteria for brake disc performance are wear in the form of a profile height variance across the radius of the brake disc, i.e., the distance between the highest and lowest points on the surface of the brake disc. A profile height variance of less than 3 pm (three micrometers) is rated as good, and 7 pm as poor. An average friction coefficient of 0.48 (forty-eight hundredths) is rated as very good, with pressures of 20 bar (twenty-bar), 30 bar, and 40 bar applied to a piston with a diameter of 57 mm (fifty-seven millimeters) on a brake disc with a diameter of 330 mm (three hundred thirty millimeters). An average friction coefficient of less than 0.45 is rated as poor.

[0161] The evaluation criteria for the performance of the brake pads are whether grains from the brake disc have eaten into the surface, causing scoring in the brake disc, and whether scoring has formed on the brake pads themselves. This is done after a visual inspection. For comparison, a brake pad rated as poor in this context is shown in Fig. 6 (Example 12). A brake pad rated as very good in this context is shown in Fig. 7 (Example 13).

[0162] In Fig. 3, a micrograph of an embodiment according to Example No. 3 according to Table 1 above of the coating proposed herein is produced, in which the following parameters were achieved:

[0163] Process parameters:

[0164] • Beam intensity: about 1300 W / mm 2 [one thousand three hundred watts per square millimeter]

[0165] • Energy density: 1.3 J / mm 3[thirteen tenths of a joule per cubic millimeter]

[0166] • Powder mass density: 0.2 mg / mm 3 mg / mm 3 [one hundred twelve tenths of a milligram per cubic millimeter]

[0167] • High-quality coating without layer defects (bonding, pores, cracks)

[0168] • Hardness about 400 to 440 HVo.oi

[0169] • Cr content > 12 wt.%

[0170] Fig. 4 and Fig. 5 show an embodiment of the coating made from a powder material. Fig. 4 shows, in the result of Example No. H according to Table 1, an increased hard phase due to a higher chromium content compared to the coating in Fig. 3, which leads to stresses that could cause cracking and / or flaking. Due to the increased hard phase, the coating hardness increases to > 450 HVo,oi.

[0171] Fig. 5 shows an embodiment of the coating according to Example No. W in Table 1, which is made from a powder material. Fig. 5 shows the result of a reduced hard phase with a high-quality coating. Due to the reduced hard phase, the hardness is approximately 350 HVo.oi.

[0172] Fig. 6 shows photographs of brake disc 7 and brake pad (each on a brake block) in a braking system. The two rows of images in Fig. 6 and Fig. 7 show the result on the inside (bottom row) and outside (top row), with the right-hand image showing brake disc 7 and the left-hand image showing the brake pad corresponding to the side of brake disc 7 shown on the right.

[0173] The photographs show the braking system after a driving cycle. Such a driving cycle test can be conducted according to the aforementioned WLTP [Worldwide Harmonized Light Vehicles Test Procedure, valid from September 1, 2017]. The result will be positive for embodiments according to the present invention.

[0174] In particular, a 7-day driving cycle test can be conducted. Using a coating according to Example 12 and Example 3 according to Table 2, the following results can essentially be achieved:

[0175] Fig. 7 shows the results on the inside and outside using a coating according to Example 13. The suitability of the coating according to Example 13 is significantly improved compared to the coating according to Example 12 (see circled and arrowed damage in Fig. 4a). The comparisons following visual assessment of the coatings tested in Example 12 and Example 13 clearly show that the coating according to Example 13 is superior to the prior art examples in all tested parameters.

[0176] Fig. 8 shows an enlargement of the micrograph from Fig. 3 with the same material combination and with a length of 100 pm. The cross-sectional sample was analyzed using energy dispersive X-ray spectroscopy (EDX) [according to DIN ISO 22309 as of November 2015]. The measurement was taken in the axial direction of the brake disc 7, from top to bottom to the base body 1 (see the middle illustration). Within the coated surface 21, a virtually defect-free coating and a molten metallurgical bond were observed; in addition, an inhomogeneity was detected by EDX analysis. The spectroscopic analysis is shown on the right and illustrates the transition from base body 1 to the coating.

[0177] Fig. 9 shows a Vickers hardness measurement [according to EN ISO 6507-1:2018] on a cross-section of a brake disc 7 with a coated surface 21 according to Fig. 3, based on a length indication of 30 pm, in a scanning electron microscope image. A section of the polished cross-section is shown at the bottom left. The indentations of the Vickers test specimen can be seen crosswise on the cross-sections at the bottom left and right. The hardness test was carried out axially through the coating and orthogonally, approximately centrally within the coating. The test parameters here were 10 Ponds indentation force with a 15-second force ramp and a holding time of 20 seconds.

[0178] The Vickers hardness determined over the horizontal measurement series is shown in the upper left corner. The Vickers hardness is almost constant at 400 HVo,oi along the horizontal axis.

[0179] In Fig. 10 and Fig. 11, two brake discs 7 are shown from both sides, before and after a corrosion resistance test [according to the draft of ISO / DIS 9227:2021]. The outer side is shown at the top and the inner side at the bottom. On the left in Fig. 10, a brake disc 7 with a coating not based on the invention (two-layer structure, with PS [buffer layer] and RS [friction layer] made of AISI 316) is shown. The cup of the brake disc 7 is free of any coating.

[0180] It can be clearly seen here that the pot is subject to significantly more severe corrosion than the contact surface of the brake disc 7. Fig. 11 shows a brake disc 7 with a coating based on the invention, namely in a single-layer structure without PS [buffer layer] and with RS [friction layer] (i.e. applied directly to the base body 1) according to Example No. 3 in Table 1. Analogous to the left brake disc 7, the pot here is also free of a coating, so that it is also subject to similar or the same corrosion as the left brake disc 7. Both contact surfaces of the brake discs 7 show only slight to no corrosion in this view.

[0181] Fig. 12 shows a microscopic close-up of the right brake disc 7 shown in Fig. 11. Here, it is clearly visible that the coating only has surface rust 19 at its upper end (see upper arrow), but that this rust has not spread into the coating, or has spread only to a very small extent.

[0182] At the left end shown, the edge area of ​​the brake disc 7, it is uncoated and exhibits subsurface corrosion, causing the base body 1 to be attacked (see lower arrow). However, this subsurface corrosion is within an acceptable target range, which is below the standards at the time of the corrosion resistance test and within the market requirements.

[0183] With the base body and coating system proposed here, an outstandingly corrosion-resistant and wear-resistant surface can be achieved, especially for the friction surface of a brake disc.

[0184] Base body Coating system First layer Second layer Matrix alloy Carbide particles Brake disc Grain size window Powder material mixture Coating device Welding device Feeding device Feed actuator Brake fluid Reservoir Feed line Flow measurement Bypass line Surface rust Welding beam Surface to be coated

Claims

Patent claims Base body (1) with a coating system (2) which Coating system (2) comprising at least one layer (3,4) with a matrix alloy (5), wherein at least one of the layers (3,4) comprises in wt.% proportionate to the matrix alloy (5) at least the following elements: Iron; and from 10 wt.% to 26 wt.% chromium; and from 0.3 wt.% to 5 wt.% carbon; and the sum of niobium, titanium and vanadium 0.5 wt.% to 15 wt.%, wherein the coating system (2) in at least one of the layers (4) with the matrix alloy (5) further comprises separately added carbide particles (6) in a proportion of the entire respective layer (4) of at least 20 vol.% to 70 vol.%. Base body (1) according to claim 1, wherein the coating system (2) is designed in a single layer. Base body (1) according to claim 1, wherein the coating system (2) is designed in multiple layers, wherein at least a first layer (3) is designed without separately added carbide particles (6), and wherein at least one layer (4) arranged further up, preferably a penultimate and / or last layer, is formed from the matrix alloy (5) with the separately added carbide particles (6). wherein preferably the at least one first layer (3), and optionally a last layer (3), is formed from the matrix alloy (5), wherein more preferably the matrix alloys (5) of the first layer (3) and the layer (4) with the separately added carbide particles (6), particularly preferably of all layers (3, 4), are identical. Base body (1) according to one of the preceding claims, wherein at least the layer (3, 4) with the matrix alloy (5) and the separately added carbide particles (6) of the coating system (2) by means of high-speed laser deposition welding, preferably with an area rate of at least 500 cm 2 / min to a reference layer thickness of 100 pm.

5. Base body (1) according to one of the preceding claims, wherein the coating system (2) has a hardness of 300 HVo.oi to 1100 HVo.oi.

6. Base body (1) according to one of the preceding claims, wherein a proportion of separately added carbide particles (6) comprises at least 35 vol.%, preferably at least 40 vol.%, more preferably at least 50 vol.%. Preferably, the separately added carbide particles (6) are selected from titanium carbides and / or tungsten carbides, particularly preferably the separately added carbide particles (6) are exclusively titanium carbides.

7. Base body (1) according to one of the preceding claims, wherein the base body (1) is a grey cast iron base body and / or a brake disc (7).

8. Base body (1) according to one of the preceding claims, wherein the carbide particles (6) have a grain size window (8) of 6 pm to 120 pm, preferably comprising at least one, particularly preferably exclusively one, of the following separate grain size windows (8): - 3 pm to 4 pm; and - 45pm to 90pm, preferably until 106pm.

9. Powder material mixture (9) for a coating system (2) of a base body (1) according to one of the preceding claims, wherein the powder material mixture (9) contains the elements of the matrix alloy (5) and the carbide particles (6) to be added separately. Method for coating a base body (1) according to one of Claim 1 to Claim 8 and / or a powder material mixture (9) according to Claim 9, wherein at least one, preferably all, of the layers (3, 4) are applied by means of build-up welding, preferably laser build-up welding, particularly preferably high-speed laser build-up welding, preferably with an area rate of at least 500 cm 2 / min to a reference layer thickness of 100 pm.

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