Layer structure, brake disc and method

Abstract

The invention relates to a layer structure (1) comprising a carrier layer (4), a cover layer (5), and an intermediate layer (6) which is placed between the carrier layer (4) and the cover layer (5) and is formed by a material (7) having a multiphase structure, wherein the cover layer (5) is kinetically sprayed, preferably cold sprayed.

Description

[0001] 1

[0002] Layer structure, brake disc and process

[0003] The invention relates to a layer structure according to the preamble of claim 1. Furthermore, the invention relates to a brake disc for a brake device with such a layer structure and a method for producing a layer structure according to the preamble of claim 13.

[0004] WO 2023 / 186 347 A1 discloses a brake disc for a friction brake of a motor vehicle, comprising a friction section with at least one friction surface and a mounting section for wheel-side attachment to the motor vehicle, wherein the friction section and the mounting section are formed on a base body made of grey cast iron or steel, and wherein a wear-resistant layer is thermally applied as the friction surface on the friction section, and wherein a hard interlayer is arranged between the wear-resistant layer and the base body, via which the wear-resistant layer is bonded to the base body.

[0005] The object of the invention is to create a layer structure, a brake disc for a braking device and a method for producing a layer structure, in such a way that the wear resistance of the layer structure can be particularly increased.

[0006] This problem is solved according to the invention by a layered structure with the features of claim 1, by a brake disc for a braking device with the features of claim 12, and by a method for producing a layered structure with the features of claim 13. Advantageous embodiments of the invention are the subject of the dependent claims and the description.

[0007] A first aspect of the invention relates to a layered structure, particularly for a component. The layered structure can be referred to as a layered system. For example, the component, particularly in its fully manufactured state, has the layered structure. 2

[0008] The component in question is, for example, a vehicle component, specifically a motor vehicle component. Therefore, the component can be a component for a vehicle, particularly a motor vehicle. The motor vehicle is, for example, a car, specifically a passenger car. The layer structure can thus be intended for use in the motor vehicle. Alternatively, the layer structure can be intended for other applications.

[0009] The layer structure includes at least one support layer, which can be referred to as the first layer. Thus, the layer structure can have the support layer as the first layer. The support layer is, for example, made of a cast material. In other words, the support layer is produced by casting. It can therefore be intended that the support layer is produced by casting.

[0010] Furthermore, the layer structure comprises at least one cover layer, which is distinct from the carrier layer and can be referred to as the second layer. The layer structure also comprises at least one intermediate layer, which is distinct from the carrier layer and the cover layer and can be referred to as the third layer. This intermediate layer is arranged, in particular directly, between the carrier layer and the cover layer and can be referred to as the third layer. In other words, the intermediate layer extends at least partially, in particular predominantly or completely, between the carrier layer and the cover layer. This means that the carrier layer and the cover layer are connected to each other via the intermediate layer, in particular directly. Thus, the layer structure comprises, in particular, several layers, which can be the first layer, the second layer, and the third layer.

[0011] The intermediate layer is, in particular at least partially, predominantly, or completely, composed of at least one material with a multiphase microstructure. This means that the material of the intermediate layer exhibits the multiphase microstructure. In other words, the intermediate layer has the multiphase microstructure. The microstructure can be understood, in particular, as the microstructure of the material. The microstructure can describe the arrangement and order of the material's constituents at the visible and microscopic levels. In particular, the term microstructure denotes the characteristics of a collection of those partial volumes, each of which is homogeneous in its composition and spatial arrangement of its constituents with respect to a fixed axis system placed within the material. Specifically, the microstructure is characterized by the type, shape, size, distribution, and / or orientation of its constituents.The material is, for example, a metal, preferably steel. The material can therefore be steel with a multiphase structure.

[0012] To significantly increase the wear resistance of the layer structure, and in particular of the component comprising the layer structure, the invention provides that the top layer is kinetically sprayed, for example at a speed greater than 300 meters per second. In other words, at least one manufacturing step for producing the top layer or the layer structure comprises a kinetic spraying process. Thus, it is particularly intended that the intermediate layer is coated with the top layer by means of the kinetic spraying process, i.e., by kinetic spraying. The speed can be understood to refer in particular to the spraying speed at which, for example, material is applied, in particular sprayed, to the intermediate layer to form the top layer.

[0013] To significantly increase the wear resistance of the layer structure, and in particular of the component comprising the layer structure, it is preferably provided that the top layer is or is cold gas sprayed. This means that the top layer is or is produced by means of cold gas spraying. In other words, at least one manufacturing step for producing the top layer or the layer structure includes cold gas spraying, i.e., the cold gas spraying of the top layer. Thus, it is particularly recommended that the intermediate layer is or is coated with the top layer by means of cold gas spraying. Therefore, the kinetic spraying process can be cold gas spraying.

[0014] Cold gas spraying can be understood as a coating process in which a coating material, that is, in particular a material intended for the top layer, is applied in powder form at very high or high speed to a substrate, that is, in this case, the intermediate layer. For this purpose, a process gas, such as nitrogen or helium, heated to a few hundred degrees Celsius, preferably more than 1000 degrees Celsius, for example, at least substantially 1100 degrees Celsius, can be accelerated to supersonic speed by expansion in a Laval nozzle. Subsequently, powder particles of the material can be injected into a gas jet of the process gas.The injected powder particles, which can also be called spray particles, can be accelerated to such a high speed that, unlike other thermal spraying processes, they can form a dense and firmly adhering layer upon impact with the substrate material, i.e., in this case, the intermediate layer, even without prior melting or smelting. Cold gas spraying can also be referred to as "cold gas spray" or "gas dynamic cold gas spray" in English.

[0015] The invention is based in particular on the following findings and considerations: Materials known and used to date for layered systems can, in principle, tend to crack under stress. This can then lead to pitting corrosion in combination with corrosive media, which can ultimately result in damage, in particular failure, of the component containing the layered structure. The stress can be, for example, mechanical and / or thermal stress, such as thermal shock.

[0016] In contrast, the aforementioned disadvantages can be avoided by means of the layer structure according to the invention. Because the intermediate layer material has a multiphase structure, the necessary ductility and strength can be achieved for the intermediate layer, particularly to withstand thermally and / or mechanically demanding applications. This has a positive effect on the wear resistance of the layer structure. Furthermore, because the top layer is kinetically formed, for example by cold spraying, it can be made particularly hard. Thus, the hardness of the top layer can be significantly increased.The substrate layer, especially if it is made of the same cast material, can be softer than the surface layer, while the intermediate layer can be moderately hard compared to both the surface layer and the substrate layer—that is, harder than the substrate layer and softer than the surface layer. This can be due to a ferritic phase in the intermediate layer, as the ferritic phase can impart hardness and / or strength to the intermediate layer. This allows the intermediate layer to act as an intermediary between the substrate and surface layers. In particular, this means that if cracks occur in the surface layer, they cannot penetrate through the intermediate layer to the substrate layer, but can instead be contained by the intermediate layer. The intermediate layer can thus absorb crack tips, meaning it can stop or slow down their propagation.Crack tips, for example, are geometric wedges, which can make them particularly susceptible to crevice corrosion. An austenitic phase can therefore be the 5th.

[0017] The intermediate layer imparts particularly high ductility and / or corrosion resistance. The described relationships are especially advantageous in relation to residual stresses in the topcoat resulting from cold gas spraying. The intermediate layer effectively prevents the so-called eggshell effect, i.e., cracking and delamination of the topcoat due to excessive flexibility of the substrate, particularly under point loads. This significantly enhances the corrosion resistance of the coating system, especially when cracks are present or imminent. Furthermore, the tensile strength of the coating system can be significantly increased.

[0018] In a further embodiment, the multiphase structure is designed to be a two-phase structure. This means that the aforementioned intermediate layer material has a two-phase structure. This allows the intermediate layer to act particularly well as an intermediary layer between the substrate and the top layer, thereby significantly increasing the overall stability of the layer structure.

[0019] In a further embodiment, the intermediate layer is designed to be made of duplex steel. This means that the intermediate layer is at least partially, and in particular predominantly or completely, composed of duplex steel. Thus, the material with the two-phase microstructure can be steel with a two-phase microstructure in the form of duplex steel. For example, the multi-phase microstructure comprises a ferrite (alpha-iron) matrix with islands of austenite. Specifically, the multi-phase microstructure consists of the ferrite (alpha-iron) matrix with islands of austenite. Therefore, duplex steel can be used as the aforementioned intermediate layer, enabling the intermediate layer to possess both the necessary ductility and strength to withstand thermally and / or mechanically demanding applications.Furthermore, the chemical properties of the layer structure can be significantly improved, for example, to drastically reduce corrosion in the event of chemical attack by a medium. Due to its properties, duplex steel is particularly well-suited to act as an intermediary layer between the substrate and the topcoat, thus effectively preventing the aforementioned cracks from penetrating to the substrate. This significantly increases the wear resistance, and especially the corrosion resistance, of the layer structure. Furthermore, this embodiment is based on the surprising finding that the combination of the cold-gas-sprayed topcoat and the intermediate layer formed from duplex steel can create an interlocking structure. This means that the intermediate layer and the topcoat can be connected to each other via this interlocking structure, particularly in a form-fit manner.The interlocking effect can be at least promoted, and in particular caused, by a wavy or especially wavy surface of the duplex steel. This interlocking effect can result in particularly good adhesion of the top layer to the intermediate layer. This, in turn, can significantly increase the bond strength between the top layer and the intermediate layer, thereby increasing the overall strength of the layer structure. Furthermore, wear resistance, and especially corrosion resistance, can be significantly enhanced. This can be achieved, in particular, because the particularly good adhesion of the top layer can significantly slow down or stop crack propagation.

[0020] In a further embodiment, the thickness of the intermediate layer is provided for to be at least 50 micrometers, for example at least 80 micrometers, and / or a maximum of 350 micrometers, for example a maximum of 250 micrometers. In other words, the thickness of the intermediate layer is at least 50, in particular 80, micrometers and / or a maximum of 350, in particular 250, micrometers. This allows the intermediate layer to act particularly well as an intermediary layer between the top layer and the substrate, thereby significantly improving the wear resistance of the layer structure. The term "thickness" can be understood to refer to the layer thickness.

[0021] In a further embodiment, it is stipulated that the material used for the intermediate layer has a PREN number greater than 27. This means that the PREN number of the intermediate layer material is greater than 27. The PREN number can also be referred to as the PREN index. PREN is an abbreviation that stands for "pitting resistance equivalent number" in English. The PREN number is, in particular, a measure of the corrosion resistance, for example, against pitting and / or crevice corrosion, of a material, especially stainless steel. This steel can be understood to be, in particular, a corrosion-resistant steel that, for example, has a chromium (CR) content greater than 12 percent by mass. Thus, the corrosion resistance of the layer structure can be particularly high.

[0022] In a further embodiment, it is provided that the material, that is, the material used, of the intermediate layer has a yield strength greater than 450 megapascals (MPa), which is 95141

[0023] A value of 7 indicates a yield strength above 450 MPa. This means that the yield strength of the intermediate layer material is greater than 450 MPa. This significantly increases the mechanical strength of the layer structure.

[0024] In a further embodiment, it is provided that the top layer and the intermediate layer are produced by different coating processes. This means that the top layer is produced by a first coating process, and the intermediate layer is produced by a second coating process that differs from the first. In other words, the substrate is coated with the intermediate layer using the second coating process, and the intermediate layer is coated with the top layer using the first coating process. The first coating process is the aforementioned cold gas spraying. Due to the different coating processes, different stress states can exist in the top layer and the intermediate layer.This allows desired properties in the intermediate and surface layers to be specifically adjusted. This enables, on the one hand, a particularly high hardness of the surface layer, and on the other hand, allows the intermediate layer to function particularly well as the aforementioned intermediary layer.

[0025] Preferably, the intermediate layer is applied to the substrate by laser powder deposition, preferably high-speed laser powder deposition. This means that the second coating process is laser powder deposition, in particular high-speed laser powder deposition. In other words, the intermediate layer is produced by laser powder deposition. Thus, the substrate can be coated with the intermediate layer by laser powder deposition. This allows the aforementioned and desired different stress states to be set particularly well and precisely. Furthermore, the layer structure can be produced with minimal effort.

[0026] Laser powder deposition welding can be understood as a process in which a surface coating is applied to a workpiece, i.e., in this case, the substrate, by melting and, in particular, simultaneously depositing a powdered material, for example, a metal powder. Laser powder deposition welding is, for example, HS-LMD (high-speed laser cladding) or EH LA (extreme high-speed laser cladding).

[0027] In a further embodiment, the surface layer is provided for to be at least partially composed of metal and / or ceramic and / or at least one carbide. In other words, the surface layer contains metal, ceramic and / or carbide. This allows the surface layer to be made particularly hard. In particular, its wear resistance can be significantly increased.

[0028] In a further embodiment, the surface layer, particularly in a base body of the surface layer, comprises hard particles embedded within it. In other words, hard particles are embedded in the surface layer, particularly in the base body. The base body can be understood to be, in particular, a matrix. For example, the base body or matrix is ​​at least partially, and in particular predominantly or completely, made of metal. Preferably, the hard particles are made of carbide and / or ceramic. In other words, the hard particles are carbide particles and / or ceramic particles. This allows the hardness of the surface layer to be significantly increased, thereby significantly increasing the wear resistance of the layer structure.

[0029] A second aspect of the invention relates to a brake disc for a braking device, in particular for a motor vehicle. Preferably, the braking device, especially in its fully manufactured state, comprises the brake disc. In particular, the motor vehicle, especially in its fully manufactured state, comprises the braking device, and thus, in particular, the brake disc. The braking device can be understood to be, in particular, a mechanical brake, especially a friction brake. The braking device is specifically designed for reducing the speed of a vehicle having the braking device, for example, the motor vehicle, particularly in a controlled manner. This can also be referred to as braking or deceleration.

[0030] The brake disc has at least one layer structure according to the first aspect of the invention. Advantages and advantageous embodiments of the first aspect of the invention are to be regarded as advantages and advantageous embodiments of the second aspect of the invention and vice versa.

[0031] The invention is based in particular on the understanding that the braking system can cause particulate emissions during braking, which can result from abrasion on the brake disc. Such particulate emissions should generally be kept as low as possible. Furthermore, legal requirements, such as EU Regulation 7, mandate measures for particle reduction in approved passenger cars. Materials known and used previously for brake disc coating systems can, in principle, be prone to cracking under stress. This, in combination with corrosive media, can lead to pitting corrosion, which can ultimately result in brake disc failure. The coating structure of the brake disc can significantly increase its wear resistance, and especially its corrosion resistance, particularly when cracks occur or threaten to occur in the surface layer.

[0032] A third aspect of the invention relates to a method for producing a layered structure, particularly according to the first aspect of the invention. Furthermore, the method can be understood to be, in particular, a method for producing a brake disc according to the second aspect of the invention. Advantages and advantageous embodiments of the first and second aspects of the invention are to be considered as advantages and advantageous embodiments of the third aspect of the invention, and vice versa.

[0033] In this process, a substrate layer is coated with an intermediate layer, which is formed from a material with a multiphase structure, in particular a two-phase structure. In other words, the substrate layer is provided with a coating in the form of the intermediate layer. This means that the intermediate layer is applied to the substrate layer, in particular by coating the substrate layer.

[0034] To particularly increase the wear resistance, and especially the corrosion resistance, of the layer structure, the intermediate layer is coated with at least one top layer by means of kinetic spraying, preferably by means of cold gas spraying, according to the invention. In other words, the intermediate layer is coated with a 10 by means of a kinetic spraying process, preferably by means of cold gas spraying.

[0035] The coating is applied in the form of a topcoat. This means that the topcoat is applied to the intermediate layer, particularly directly, by means of kinetic spraying, especially cold gas spraying.

[0036] Further features of the invention will become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features mentioned below in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations or on their own.

[0037] The invention will now be explained in more detail with reference to a preferred embodiment and the drawing. The single figure in the drawing shows a schematic representation of a layer structure according to the invention.

[0038] Fig. 1 shows a schematic partial sectional view of a layer structure 1. The layer structure 1 can be provided for a component 2 which has the layer structure 1. In the exemplary embodiment, the component 2 is a brake disc 3 for a braking system, in particular of a motor vehicle.

[0039] The brake disc 3, for example, has a base body designed as a brake disc hub, which can also simply be referred to as a hub. Furthermore, the brake disc 3 has, for example, a friction ring arranged, in particular directly, on the brake disc hub. Thus, brake pads of the braking system, for example, attached to a brake caliper of the braking system, can act on the brake disc, in particular via the friction ring, to brake the vehicle, for example, by decelerating the rotational movement of at least one wheel of the vehicle. The brake pad can therefore rub against the brake disc, in particular via the friction ring, thereby generating braking of the vehicle by converting kinetic energy into heat. This means that the friction ring is designed, in particular, for the mechanical application of pressure by the brake pad.The friction ring can have layer structure 1 or the friction ring can be provided with layer structure 1.

[0040] As shown in Fig. 1, the layer structure comprises a support layer 4 and a cover layer 5, which is formed separately from the support layer 4. The support layer 4 can be referred to as the support material, substrate, or substrate. 95141

[0041] 11. Furthermore, the layer structure 1 comprises an intermediate layer 6 arranged between the carrier layer 4 and the cover layer 5, and in particular formed separately from the carrier layer 4 and the cover layer 5, which is formed from a material 7 with a multiphase structure. In other words, the carrier layer 4 and the cover layer 5 are spaced apart from each other, at least in certain areas, with the intermediate layer being arranged at this distance. Thus, the carrier layer 4 adjoins the intermediate layer 6, in particular directly, on a first side 8, and the cover layer 5 adjoins the intermediate layer 6, in particular directly, on a second side 9 that is different from the first side 8, and in particular facing away from the first side 8.This means that the carrier layer 4, in particular on the first side 8, is provided or coated with a coating in the form of the intermediate layer 6, which, on a side facing away from the carrier layer 4, in particular on the second side 9, is provided or coated with a coating in the form of the top layer 5. In the present case, the carrier layer 4 and the top layer 5 are connected to each other, in particular directly, via the intermediate layer 6. In particular, the carrier layer 4 and the top layer 5 adjoin the intermediate layer 6 along one direction, in particular on both sides.

[0042] In this case, the surface layer 5 has an outer surface 10 that faces outwards, particularly with respect to the component 2 or the brake disc 3. Thus, the component 2 or the brake disc 3 can be bounded by the outer surface 10, or even formed by the outer surface 10, particularly in the axial direction. The surface layer 5, and in particular its outer surface 10, is designed, for example, to engage directly with the brake pad. This means that, for example, the brake pad can mechanically contact the brake disc 3 via the surface layer 5, in particular directly, to decelerate the vehicle. The surface layer 5 can therefore be the uppermost or outermost layer of the layer structure 1.

[0043] To significantly increase the wear resistance, and in particular the corrosion resistance, of the layer structure 1, especially of the brake disc 3, the top layer 5 is kinetically sprayed, preferably by cold gas spraying. In other words, the top layer 5 is designed as a kinetically sprayed layer, preferably a cold gas sprayed layer. This means that the intermediate layer 6, that is, in particular the carrier layer 4 and the intermediate layer 6, is coated with the top layer 5 by means of kinetic spraying, in particular by means of cold gas spraying. This allows for a particularly high 95141

[0044] 12 or a sufficient hardness of the top layer 5 is achieved, and by means of the intermediate layer 6 a particularly high or sufficient ductility can be achieved so that the intermediate layer 6 can act as an intermediary layer between the top layer and the base layer 4. This can reliably prevent any cracks in the top layer 5 from propagating to the base layer 4, thereby keeping corrosion due to such cracks to a minimum.

[0045] The multiphase microstructure is, for example, a two-phase microstructure. The material 7 of the intermediate layer 6 is particularly preferably duplex steel 11. The intermediate layer 6 can thus be formed at least partially, and in particular predominantly or completely, from the duplex steel 11. For example, the yield strength of the intermediate layer 6, or of the material 7 of the intermediate layer 6, in particular of the duplex steel 11, is greater than 450 MPa. For example, the PREN number of the intermediate layer 6, or of the material 7 of the intermediate layer 6, in particular of the duplex steel 11, is greater than 27. The PREN number can also be referred to as the PREN index. PREN is an abbreviation that means "pitting resistance equivalent number" in English.The PREN number is, in particular, a measure of the corrosion resistance, for example against pitting and / or crevice corrosion, of a material, especially stainless steel. Thus, the corrosion resistance of layer 1 can be particularly high.

[0046] The PREN number is calculated in particular according to ASTM G48. For example, the PREN number is calculated using the following formula:

[0047] PREN = 1 * %Cr + 3.3 * %Mo + 16 * %N (w / w)

[0048] Alternatively, the PREN number can be calculated according to DIN EN ISO 15156 using the following formula:

[0049] PREN = 1 * %Cr + 3.3 * (%Mo + 0.5 * %W) + 16 * %N

[0050] The thickness 12 of the intermediate layer 6, in particular of the duplex steel 11, is, for example, at least 50, in particular 80, micrometers. Alternatively or additionally, the thickness 12 is a maximum of 350, in particular 250, micrometers. As shown in Fig. 1, for example, the thickness 12 of the intermediate layer 6 is less than the thickness 13 of the carrier layer 4. The respective thicknesses 12 and 13 can be understood, in particular, as the respective thicknesses in the direction along which the carrier layer 4 and the cover layer 5 adjoin the intermediate layer 6, in particular on both sides.

[0051] For example, the support layer 4 is formed from a cast material 14, in particular a metallic one. For example, the cover layer 5, in particular a base body 15 of the cover layer 5, is formed at least partially, in particular predominantly, from a metal 16. The metal 16 is, for example, an alloy, such as a titanium alloy. The titanium alloy is, for example, Ti-6Al-4V, which can also be referred to as Ti64. For example, the metal 16 is steel, in particular a stainless steel, which can be understood to be, for example, a corrosion-resistant steel and / or a steel with a mass fraction of chromium (Cr) greater than 12 percent.

[0052] In this embodiment, the top layer 5, particularly in the base body 15, has hard particles 17 embedded within it. Thus, in this embodiment, it can be a hard-coated brake disc 3 with duplex steel 11 as an intermediate layer 6. The hard particles 17 are, for example, made of a carbide and / or a ceramic. Therefore, the top layer 5 can contain a ceramic component and / or a carbide component. The carbide is, for example, tungsten carbide, niobium carbide, titanium carbide, or silicon carbide.

[0053] Preferably, the top layer 5 and the intermediate layer 6 are produced by different coating processes. It is particularly preferred that the intermediate layer 6 is produced by laser powder deposition welding. In other words, the intermediate layer 6 is applied to the substrate layer 4 by laser powder deposition welding. The different coating processes can thus be laser powder deposition welding and the aforementioned cold gas spraying. This allows for significant differences in stress states between the top layer 5 and the intermediate layer 6, enabling the targeted adjustment of their respective properties. This, in turn, significantly improves corrosion resistance.

[0054] Numerals, such as "first", "second", "third", etc., are intended solely for differentiation and do not, in particular, denote an order. That is to say, the corresponding numerals can be interchanged at will. 14

[0055] Reference symbol list

[0056] 1 layer structure

[0057] 2 Component

[0058] 3 brake disc

[0059] 4 Carrier layer

[0060] 5 Top layer

[0061] 6 Intermediate shift

[0062] 7. Intermediate layer material

[0063] 8 first page of the intermediate layer

[0064] 9 second side of the intermediate layer

[0065] 10 Outside

[0066] 11 Duplex steel

[0067] 12 Thickness of the intermediate layer

[0068] 13 Thickness of the carrier layer

[0069] 14 Cast material

[0070] 15 basic shapes

[0071] 16 Metal

[0072] 17 Cardiac particle

Claims

15 Patent claims 1. Layer structure (1), comprising a carrier layer (4), a cover layer (5) and an intermediate layer (6) arranged between the carrier layer (4) and the cover layer (5), which is formed from a material (7) with a multiphase structure, characterized in that the cover layer (5) is kinetically sprayed.

2. Layer structure (1) according to claim 1, characterized in that the top layer (5) is cold gas sprayed.

3. Layer structure (1) according to claim 1 or 2, characterized in that the multiphase structure is a two-phase structure.

4. Layer structure (1) according to one of the preceding claims, characterized in that the material (7) of the intermediate layer (6) is duplex steel (11).

5. Layer structure (1) according to one of the preceding claims, characterized in that a thickness (12) of the intermediate layer (6) is at least 50 micrometers and / or at most 350 micrometers.

6. Layer structure (1) according to one of the preceding claims, characterized in that the material (7) of the intermediate layer (6) has a PREN number greater than 27.

7. Layer structure (1) according to one of the preceding claims, characterized in that the material (7) of the intermediate layer (6) has a yield strength greater than 450 megapascals. 16 8. Layer structure (1) according to one of the preceding claims, characterized in that the top layer (5) and the intermediate layer (6) are produced by different coating processes.

9. Layer structure (1) according to claim 8, characterized in that the intermediate layer (6) is applied to the carrier layer (4) by means of laser powder deposition welding, preferably laser powder high-speed deposition welding.

10. Layer structure (1) according to one of the preceding claims, characterized in that the cover layer (5) is formed at least partially from metal (16), ceramic and / or a carbide.

11. Layer structure (1) according to one of the preceding claims, characterized in that the top layer (5) has embedded hard material particles (17) which are formed in particular from a carbide or from ceramics.

12. Brake disc (3) for a braking device, in particular of a motor vehicle, with a layer structure (1) according to one of the preceding claims.

13. Method for producing a layer structure (1) wherein a support layer (4) is coated with an intermediate layer (6) which is formed from a material (7) with a multiphase structure, characterized in that the intermediate layer (6) is coated with a top layer (5) by means of kinetic spraying, preferably cold gas spraying.

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