Coated brake element and method for producing a coated brake element

Abstract

The invention relates to a coated brake element (1), in particular a brake disc or a brake drum, having a main body (10) and at least one friction surface (12, 15), which is arranged on the main body (10); a coating (13, 16) is arranged on the at least one friction surface (12, 15), the coating (13, 16) comprising an intermediate layer (23, 26) and a friction layer (33, 36), the intermediate layer (23, 26) is arranged between the base body (10) and the friction layer (33, 36) and is applied to the friction surface (12, 15) by means of laser coating welding, and the friction layer (33, 36) is applied by means of cold air injection and comprises at least one metallic material. The invention also relates to a method for producing a coated brake element (1).

Description

FIELD OF THE INVENTION

[0001] The present invention relates to a coated brake element, in particular a brake disc or a brake drum, and a method for manufacturing a coated brake element. BACKGROUND OF THE INVENTION

[0002] Brake elements, such as brake drums or brake discs, for example for vehicle brakes (such as drum brakes or disc brakes), typically have a substrate made of grey cast iron, cast steel or cast aluminium. In the case of a brake disc, both sides of the brake disc are configured as friction surfaces. In a drum brake, the friction surface is typically configured on a cylindrical surface (brake drum).

[0003] Drum brakes and disc brakes are respectively friction brakes. The braking action or deceleration of a vehicle is achieved by pressing brake linings against the friction surfaces mechanically, hydraulically or pneumatically.

[0004] Due to high frictional forces and the resulting heat generation, known brake discs and brake drums are subject to severe wear. In addition, particles of the brake disc or brake drum are worn off during braking. This wear generates fine dust and increases the environmental load.

[0005] Another problem is that known brake discs and brake drums are vulnerable to corrosion. Different solutions are known to reduce wear and thus also reduce the formation of fine dust.

[0006] For example, known brakes operate as closed systems from which brake wear debris cannot escape or can only escape in a controlled manner (e.g. via a suction system). In addition, brake discs or brake drums with coated friction surfaces are known. The coating should increase the service life of the brake disc / brake drum and minimize wear.

[0007] Known coatings are generally prone to delamination, such that the coating detaches from the substrate. This leads to a sharp drop in the braking action and thus constitutes a safety risk. In addition, known coatings generally have low thermal conductivity, so that the heat generated during braking is only poorly dissipated and causes additional thermal loads on the brake, especially the coating. SUMMARY OF THE INVENTION

[0008] The object of the present invention is to provide a brake element, in particular a brake disc or a brake drum, which at least partially overcomes the above-mentioned disadvantages. In addition, a method for manufacturing such a brake element should be provided.

[0009] According to the present invention, the object is solved by a coated brake element according to claim 1, by a brake device according to claim 14 and by a method for manufacturing a coated brake element according to claim 15. Other aspects of the present invention are set out in the dependent claims and in the following description.

[0010] In particular, the task is solved by a coated brake element having a substrate and at least one friction surface arranged on the substrate.

[0011] For example, the brake element can be a brake disc or a brake drum. In the case of a brake disc, one or more friction surfaces can be provided. These friction surfaces can be located on opposite sides of the brake disc and / or arranged offset in the radial direction, preferably concentrically. In the case of a brake drum, the one / more friction surfaces are typically arranged on the inner cylindrical surface, and the friction surfaces can be arranged offset in the axial direction.

[0012] The coated brake element can be a brake element of a bicycle brake, a motorcycle brake, a car brake, a heavy vehicle brake, a commercial vehicle brake, a rail vehicle brake, and / or a similar brake. The use of the brake element or the corresponding braking device is not limited to vehicles. Thus, the coated brake element can be a brake element of a machine.

[0013] A coating is arranged on the at least one friction surface, wherein the coating includes at least one intermediate layer and a friction layer. In one aspect, additional layers are provided (e.g., below the intermediate layer, between the intermediate layer and the friction layer, and / or above the friction layer). In another aspect, the coating consists of the intermediate layer and the friction layer, wherein the coating is arranged directly (i.e., non-indirectly) on the friction surface of the substrate.

[0014] The intermediate layer is arranged between the substrate (especially the friction surface of the substrate) and the friction layer and is applied to the friction surface by laser cladding welding. As described above, the intermediate layer can be applied directly or indirectly to the friction surface.

[0015] Laser cladding welding is a coating process particularly suitable for coating metallic materials. Via a laser (e.g., a Nd:YAG laser, a CO 2 laser or a similar device), the surface of the component (here, for example, the friction surface of the substrate to be coated) is melted in a targeted and controlled manner. Thus, a locally narrow-limited molten pool is formed. Due to the local limitation of the molten pool, less heat is input into the substrate.

[0016] At the same time, (metal) material is applied to the molten pool generated by the laser, and this (metal) material then forms the intermediate layer. In addition to metals and metal alloys, the material can also include additives.

[0017] The material of the intermediate layer is applied to the molten pool, for example, as powder via a nozzle or as a metal wire. In the molten pool, the molten material of the component (such as the substrate) is mixed with the applied material, so that a fixed, especially metallurgical (such as welding) bond is formed between the intermediate layer and the component.

[0018] Thus, the intermediate layer formed by laser cladding welding can be structurally identified from the transition region (also known as the mixing zone). In the mixing zone, the applied material of the intermediate layer and the material of the component (especially the substrate) exist in a mixed form.

[0019] In particular, when laser cladding welding the intermediate layer, a mixture of different coating materials can also be applied simultaneously or sequentially. For example, an alloy of nickel and / or iron can be applied to the friction surface. Via the components of the alloy and via optional additives, the hardness, thermal conductivity, and / or coefficient of thermal expansion of the intermediate layer can be adjusted.

[0020] In principle, different laser cladding welding methods can be used to apply the intermediate layer. For example, it includes laser cladding welding (LC), high-speed laser cladding welding (HSLC), and extremely high-speed laser cladding welding (EHLA).

[0021] In laser cladding welding (LC), a laser beam is used to apply the material of the intermediate layer to the friction surface. The applied material (e.g., in the form of a wire or powder) is heated in the molten pool and melted together with the material of the friction surface or the substrate. Laser cladding welding enables precise control of the coating thickness, microstructure, and material composition of the intermediate layer.

[0022] High-speed laser cladding welding (HSLC) is based on laser cladding welding but can achieve a higher coating speed. In high-speed laser cladding welding, the coating material (especially powder) has been heated almost to the melting temperature by the laser above the surface of the component (i.e., outside the molten pool). Thus, less time is required in the molten pool to melt the material of the intermediate layer.

[0023] Extremely high-speed laser cladding welding (EHLA) is also based on laser cladding welding and can achieve a further increased coating speed. In the EHLA method, the laser has melted the coating material above the molten pool. Therefore, it is liquid material droplets, rather than solid powder particles, that enter the molten pool. Thus, in addition to a higher coating speed, a smoother surface is also obtained.

[0024] The friction layer of the brake element is applied by means of cold gas injection. The friction layer includes at least one metal material. The friction layer can be made of a metal material or can include other materials (additional materials and / or wear-resistant materials).

[0025] In particular, the friction layer can include wear-resistant materials. In the friction layer, the wear-resistant materials are at least partially embedded in the metal material. Thus, the metal material forms a matrix for the wear-resistant materials.

[0026] The friction layer may comprise a metallic material in a weight percentage between 95% and 5%. Correspondingly, the friction layer may comprise a wear-resistant material in a weight percentage between 5% and 95%. In one embodiment, the friction layer comprises a metallic material in a weight percentage between 75% and 25% and a wear-resistant material in a weight percentage between 25% and 75%. Additives may also be part of the friction layer. In this case, the proportion of the metallic material and / or the wear-resistant material is reduced accordingly.

[0027] During cold gas spraying, the coating material (i.e., the material of the later friction layer) is applied in powder form at a very high speed to a carrier material (here the intermediate layer). In addition to the metallic material and the optional wear-resistant material, the coating material may also comprise other additives, such as copper particles. The hardness, friction resistance strength, thermal conductivity and / or coefficient of thermal expansion of the friction layer can be adjusted via the components of the coating material.

[0028] The coating material may be present in the form of a uniform powder or may comprise different powders (powder mixture).

[0029] In the case of a uniform powder, the powder may be made of a metallic material, for example. If the friction layer is to comprise at least one wear-resistant material (and / or additives) in addition to the metallic material, the powder particles may comprise the at least one wear-resistant material, the precursor of the at least one wear-resistant material and / or the at least one additive in addition to the metallic material. Thus, the wear-resistant material (or precursor and / or additive material) is at least partially embedded in the metallic material before cold gas spraying.

[0030] In the case of a powder mixture, the different powders may be cold gas sprayed simultaneously or successively. For example, the first powder may comprise a metallic material and the second powder may comprise a wear-resistant material. Other powders (e.g., powders of additives or precursors of wear-resistant materials) may be provided accordingly. In this case, the wear-resistant material (or additive) is at least partially embedded in the metallic material (matrix) during cold gas spraying.

[0031] If a precursor of the wear-resistant material is provided (e.g., as a separate powder or embedded in the metallic material), the precursor may be chemically converted into the wear-resistant material during cold gas spraying, for example by carbonization and / or oxidation. For this purpose, the precursor and the process gas may be selected accordingly and preheated if necessary. The precursor may also correspond to the metallic material, i.e., be configured to be integral with the metallic material. In this case, a part of the metallic material is converted into the wear-resistant material before and / or during cold gas spraying.

[0032] In order to accelerate the coating material accordingly, a process gas (such as air, carbon dioxide, nitrogen, argon, water vapor or helium) is introduced into the spraying device under high pressure (for example, at least 20 bar or at least 40 bar or at least 50 bar or at least 60 bar or at least 80 bar) and temperature-controlled. The temperature-controlled temperature is in the range of 300 to 1300 °C, or in the range of 500 to 1200 °C, or in the range of 800 to 1100 °C. In the spraying device, the process gas is mixed with at least a part of the powdery coating material, wherein the heating temperature is lower than the melting temperature of the coating material.

[0033] If the precursor is to be converted into a wear-resistant material, the powdery precursor can be mixed with the process gas and temperature-controlled before being mixed with the metallic material, so as to form a wear-resistant material. The wear-resistant material can also be formed at the moment when the metallic material and the precursor have been mixed. In addition, the precursor can be configured to be integral with the metallic material. In this case, a part of the metallic material is converted into a wear-resistant material before and / or during the cold gas spraying.

[0034] Then, the powder-gas mixture is guided through a converging-diverging nozzle (Laval nozzle). This results in the powder-gas mixture being accelerated to a very high speed, especially to supersonic speed (for example, at least 300 m / s, or at least 500 m / s, or at least 800 m / s, or at least 1000 m / s or at least 1200 m / s). In addition, the powder-gas mixture is strongly cooled, for example, cooled to a temperature below 100 °C.

[0035] The strongly accelerated powdery coating material can be guided in the jet stream onto the carrier material or the intermediate layer. In addition, the jet stream can be focused so that it impinges on the carrier material, for example, with a cross-sectional area of 3 mm 2 to 100 mm 2 、or 5 mm 2 to 80 mm 2 、or 10 mm 2 to 50 mm 2 .

[0036] Then, the powdery coating material is firmly connected to the carrier material due to its high kinetic energy. Each powder particle causes the carrier material (especially the intermediate layer) to be point-deformed and deforms itself upon impingement. Therefore, the carrier material is compacted at least on the surface and a firm connection is established between the carrier material (such as the intermediate layer) and the coating material or the friction layer. The coating material sprayed by cold gas adheres basically form-locked. In addition, the coating material neither melts nor fuses during the cold gas spraying, so that the risk of unwanted oxidation of the coating material is small.

[0037] Surprisingly, it has been shown that a coating consisting of a friction layer sprayed with cold gas and an interlayer welded by laser cladding has a very high adhesion strength on the substrate and very good layer adhesion within the coating. Because the interlayer welded by laser cladding adheres very well to the friction surface due to the connection by material locking. However, laser cladding welding first results in a high internal stress and a high surface roughness in the interlayer. Therefore, although the interlayer adheres well (before the cold gas sprayed friction layer), it is still prone to cracking. The subsequent cold gas spraying, i.e., applying the friction layer, reduces the stress in the interlayer and compacts it at least on the surface. This is achieved by the deformation effect of the incident powder particles of the coating material, so the cracking risk is significantly reduced. The roughness of the interlayer also leads to good adhesion of the friction layer.

[0038] The coating according to the invention is extremely dense and has a high cohesive strength, so that crack growth due to thermal load and / or mechanical load can be avoided (especially from the friction layer through the interlayer to the friction surface or the substrate). In addition, the coating has corrosion resistance (especially crevice corrosion, pitting corrosion and galvanic corrosion).

[0039] In addition, the interlayer can compensate for the differences in thermal conductivity and / or coefficient of thermal expansion that may exist between the substrate and the friction layer. For this purpose, the interlayer has a thermal conductivity that is, for example, higher than the thermal conductivities of the substrate and the friction layer or between the two, so that the heat generated during braking can be quickly dissipated from the surface. In addition, the interlayer has a coefficient of thermal expansion that is, for example, between the coefficients of thermal expansion of the substrate and the friction layer. Therefore, thermal-induced stresses in the braking element can be avoided or at least reduced.

[0040] In addition, laser cladding welding results in the following surface topology (especially roughness) of the interlayer, which allows for an optimal bonding of the cold gas sprayed friction layer. This leads to a high layer adhesion of the friction layer.

[0041] Due to the good adhesion and high density of the coating, high wear resistance can be achieved and microdust emissions during braking can be reduced. By applying wear-resistant materials embedded in the friction layer, the wear resistance can be further improved.

[0042] In one aspect, the coating consists of an interlayer and a friction layer, wherein the coating can be directly arranged on at least one friction surface of the substrate. In this case, the friction surface of the substrate is coated with a two-layer coating.

[0043] In another aspect, the substrate has at least two friction surfaces. These friction surfaces are optionally arranged on opposite sides of the substrate. For example, the substrate is the substrate of a brake disc, which has coated friction surfaces on both sides.

[0044] In addition, the substrate can be single-piece or multi-component. In the case of a multi-component substrate, the components are typically firmly connected to each other (such as by fusion welding, screwing, riveting, bonding, and / or soldering). Each component of the multi-component substrate can have a coated friction surface. An example of a multi-component substrate is a two-component brake disc.

[0045] The substrate can comprise or be made of at least one of the following materials: gray cast iron, cast steel, steel, aluminum, especially cast aluminum, aluminum-based alloys, titanium, titanium-based alloys, ceramics, polymers, metal polymers, or composite materials (such as fiber-reinforced ceramics). It is shown that laser cladding welding is not limited to metal substrates, but can be used to coat, for example, polymer substrates or ceramic substrates. Thus, wear-resistant brake elements made of polymers or ceramics can be manufactured.

[0046] In one aspect, the intermediate layer and the substrate form a hybrid zone. The thickness of this hybrid zone in the coated brake element is in the range of 0.05 μm to 100 μm, or in the range of 0.5 μm to 50 μm, or in the range of 0.5 μm to 20 μm, or in the range of 0.6 μm to 1 μm. It has been shown that these thicknesses result in particularly good adhesion of the intermediate layer.

[0047] In addition, the intermediate layer can have a layer thickness in the range of 10 μm to 1500 μm, or in the range of 20 μm to 500 μm, or in the range of 25 μm to 250 μm. These layer thicknesses result in an ideal balance, especially an ideal balance of the coefficient of thermal expansion, because possible thermal stress is distributed over the layer thickness of the intermediate layer. Thus, local stress peaks can be avoided.

[0048] The intermediate layer can comprise and / or be made of iron-based alloys and / or nickel-based alloys. The iron-based alloy can have a chromium content of 4% to 40% by weight. The copper content is preferably less than 0.5% by weight. The nickel-based alloy can have a chromium content of 3% to 25% by weight. The copper content is preferably less than 0.5% by weight.

[0049] In addition (alternatively or additionally), the intermediate layer can comprise or be made of one of the following materials: iron-based alloys, nickel, nickel-based alloys, titanium, titanium alloys, copper, copper alloys, cobalt-chromium alloys, and / or aluminum alloys.

[0050] By selecting the material of the intermediate layer and possible additives or material components, the coefficient of thermal expansion and / or the thermal conductivity of the intermediate layer can be adjusted.

[0051] In one aspect, the intermediate layer has a value in the range of 8*10 -6 / K to 25*10 -6 / K, or in the range of 9*10 -6 / K to 18*10-6 in the range of / K, or in the range of 13*10 -6 / K to 17*10 -6 / K. In addition, the intermediate layer may have a thermal expansion coefficient in the range of 15 W / (mK) to 450 W / (mK), or in the range of 50 W / (mK) to 300 W / (mK), or in the range of 80 W / (mK) to 100 W / (mK).

[0052] The friction layer may have a layer thickness in the range of 10 μm to 500 μm, or in the range of 20 μm to 400 μm, or in the range of 25 μm to 250 μm.

[0053] In particular, the ratio d of the thickness of the friction layer to the thickness of the intermediate layer R :d Z can be in the range of 4:1 to 1:3, or in the range of 3:1 to 1:1, or in the range of 2:1 to 3:2. For example, the thickness of the friction layer can be about 200 μm, and the thickness of the intermediate layer can be about 125 μm (d R :d Z = 1.6).

[0054] The metal material of the friction layer may at least include one of the following materials or be made of one of the following materials: steel (such as 316L, 430L, 447 or duplex steel), iron-based alloy, nickel, nickel-based alloy (such as Inconel, Hastelloy, Incoloy), titanium, titanium-based alloy (such as Ti2.5Cu, Ti6Al4V, Ti8Al1Mo1V, Ti3Al8V6Cr4Zr4Mo), copper, copper-based alloy (such as CuCrZr, CuAl, CUSn, CuZn), aluminum, aluminum-based alloy (such as AlSiMg, Al2024, A357, Al6061, Al7050) and / or similar materials. In particular, the titanium-based alloy may contain 5.5 to 6.75% by weight of aluminum and 3.5 to 4.5% by weight of vanadium.

[0055] The wear-resistant material of the friction layer may at least include one of the following materials or be made of one of the following materials: tungsten carbide, boron nitride, titanium carbide, iron carbide, silicon carbide, silicon nitride, chromium carbide, niobium carbide, titanium nitride, aluminum oxide, zirconium oxide and / or similar materials.

[0056] The wear-resistant material may exist in the friction layer in the form of particles and / or fibers. The particle size or fiber diameter may be in the range of 0.5 μm to 80 μm, particularly in the range of 1 μm to 50 μm, or in the range of 5 μm to 25 μm.

[0057] The metal material and the wear-resistant material can be selected in such a way as to adjust the desired thermal conductivity and / or the desired coefficient of thermal expansion. For example, the friction layer may have a coefficient of thermal expansion in the range of 8×10 -6 / K to 25×10 -6 / K, or in the range of 9×10 -6 / K to 18×10 -6 / K, or in the range of 13×10 -6 / K to 17×10 -6 / K. In addition, the friction layer may have a thermal conductivity in the range of 15 W / (mK) to 450 W / (mK), or in the range of 50 W / (mK) to 300 W / (mK), or in the range of 80 W / (mK) to 100 W / (mK).

[0058] The above task is also solved by a braking device. The braking device includes at least one braking element with a coating as described above, wherein the braking element is arranged to be rotatable. The braking device further includes at least one brake lining, wherein the brake lining is arranged to be movable relative to the braking element. The brake lining is configured to cooperate and engage with the friction surface of at least one coating of the braking element to achieve a braking effect on the braking element. The braking device is characterized by low wear, long service life, and low fine ash emissions.

[0059] The braking device can be a drum brake or a disc brake and can be configured for use in vehicles, especially bicycles, motorcycles, cars, trucks, commercial vehicles, rail vehicles, and / or similar vehicles.

[0060] Furthermore, the above task is solved by a method for manufacturing a coated braking element, especially a brake disc or a brake drum, wherein the braking element is the braking element as described above. The method includes the following steps:

[0061] - Providing a substrate, wherein the substrate has at least one friction surface. Providing may include the actual manufacture of the substrate (such as casting, sintering,...) and its possible machining, as well as simply providing the substrate.

[0062] - Laser cladding and welding an intermediate layer onto the at least one friction surface (a nickel and / or iron-based alloy as described above). The laser cladding and welding is preferably carried out as described above. In particular, the laser cladding and welding can be a laser cladding welding process (LC), a high-speed laser cladding welding process (HSLC), or an extremely high-speed laser cladding welding process (EHLA).

[0063] - Cold gas spraying a coating material onto the intermediate layer while forming a friction layer, wherein the coating material includes a metal material or is made of a metal material.

[0064] The coating material may further include a wear-resistant material and / or a precursor of the wear-resistant material.

[0065] During cold gas spraying, the wear-resistant material may be at least partially embedded in the metallic material. Thus, the coating material may include metallic material powder and wear-resistant material powder (powder mixture).

[0066] Alternatively or additionally, the wear-resistant material and / or the precursor of the wear-resistant material may be at least partially embedded in the metallic material before cold gas spraying. Thus, all or part of the powder particles of the coating material may include the at least one wear-resistant material, the at least one precursor of the wear-resistant material, and / or the at least one additive material in addition to the metallic material.

[0067] As described above, the precursor of the wear-resistant material may be chemically converted into the wear-resistant material during cold gas spraying.

[0068] Before laser cladding the intermediate layer, the method may further include machining the friction surface to be coated. The machining may include at least one of the following steps:

[0069] Spraying the at least one friction surface (e.g., sandblasting, shot peening, water spraying...);

[0070] Machining the at least one friction surface, in particular mechanically roughening or smoothing the at least one friction surface (e.g., by turning, milling, grinding, honing...);

[0071] Laser machining the at least one friction surface, in particular laser cleaning and / or laser structuring, and / or

[0072] Thermally conditioning the at least one friction surface (cooling or heating). BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The present invention will be described in more detail below with reference to the accompanying drawings. The drawings show:

[0074] Figure 1 : A schematic cross-sectional view of a brake disc according to an embodiment of the present invention;

[0075] Figure 2 : Figure 1 An enlarged detail view of the shown brake disc;

[0076] Figure 3 : A schematic view of the manufacturing method according to the present invention;

[0077] Figure 4 : A schematic view of the coating of the intermediate layer;

[0078] Figure 5 : A schematic view of the coating of the friction layer, and

[0079] Figure 6 :Highly magnified schematic view of the cross-section of the coating. Detailed implementation

[0080] Figure 1 There is shown a brake element, in particular a brake disc 1 for a disc brake used in a vehicle, such as a car, a heavy vehicle, a motorcycle, a bicycle or a rail vehicle.

[0081] The brake disc 1 includes a base body 10 which includes a central part in the form of a cup in the illustrated embodiment and an annular disc body extending radially outwards from the central part. In the illustrated embodiment, the base body 1 is integral, but it can also be multi-component. Preferably, the base body is made of cast steel, grey cast iron, cast aluminium, polymer or composite material.

[0082] The central part is used in a known manner to fix the brake disc 1 to a rotating component, such as on the wheel hub of a vehicle. The annular disc body extending radially beyond the central part is arranged in a main plane which extends perpendicular to the central axis M of the brake disc 1.

[0083] On opposite sides 11, 14 of the brake disc 1 there are respectively provided a friction surface 12, 15. Each of the friction surfaces 12, 15 is coated with a coating 13, 16.

[0084] The coating 13 on the first side 11 of the brake disc 1 is shown in more detail in detail A, and the coating 16 on the second side 14 of the brake disc 1 is shown in more detail in detail B (see Figure 2 ). The coatings 13 and 16 are substantially the same.

[0085] As Figure 2 shown, the coatings 13, 16 include an intermediate layer 23, 26 and a friction layer 33, 36. The intermediate layers 23, 26 are arranged between the base body 10 and the friction layers 33, 36 and are applied to the friction surfaces 12, 15 by laser cladding welding. The intermediate layer includes, for example, an iron-based and / or nickel-based alloy.

[0086] The friction layers 33, 36 are applied by cold gas spraying and include a metallic material 320 (see Figure 5 ) and a wear-resistant material 325 (see Figure 5)。The metallic materials may include steels (such as 316L, 430L, M3 / 2, M152), iron-based alloys, nickel, nickel-based alloys (such as IN625, IN718, Invar36, NICR, MCRAlY), titanium, titanium-based alloys (such as Ti6Al4V, TiAl), copper, copper-based alloys (such as CuCrZr, CuAl, CUSn, CuZn), aluminum, aluminum-based alloys (such as AA2024, A357, AA6061, AA7050) and / or similar materials. The wear-resistant materials may for example include tungsten carbide, boron carbide, titanium carbide, iron carbide, silicon carbide, silicon nitride, chromium carbide, niobium carbide, titanium nitride, aluminum oxide and / or zirconium oxide.

[0087] Figure 3 Disclosed is a method for manufacturing a braking element 1 for a coating, in particular a brake disc. First, in step 100, a substrate 10 is provided, wherein the substrate 10 has at least one friction surface 12.

[0088] In step 200, an intermediate layer 23 is laser cladded and welded onto the at least one friction surface 12. The material 220 of the intermediate layer is provided, for example, in powder form via a nozzle. The laser beam 210 locally melts the substrate. The material 220 of the intermediate layer is applied to the resulting molten pool and melted, so that it is partially mixed with the material of the substrate and finally adheres to the friction surface 12. Additionally, a protective gas 240 such as argon can be directed at the molten pool to avoid undesired oxidation.

[0089] In step 300, the friction layer 33 is applied by cold gas injection. For this purpose, the material of the friction layer (metallic material 320 and wear-resistant material 325 together with process gas 310 (such as nitrogen, helium, argon, CO 2 , air, water vapor) is strongly accelerated in a Laval nozzle 305 and sprayed onto the intermediate layer 23, while forming the friction layer 33.

[0090] Figure 4 Laser cladding welding 200 is again shown by way of example. Via a laser (such as a Nd:YAG laser, a CO 2 laser or a similar device) or a laser beam 210, the surface or the friction surface 12 of the substrate 10 is selectively melted. Thus, a locally narrow-limited molten pool 234 is formed. Due to the local limitation of the molten pool 234, less heat is input into the substrate 10, so that only a small heat-affected zone 236 is formed.

[0091] At the same time, the material 220 of the intermediate layer (here in powder form) is applied to the molten pool 234 generated by the laser. In addition to metals and metal alloys, the material may also include additives. In the molten pool 234, the molten material of the substrate is mixed with the applied material 220, thereby forming a firm welded connection between the coated material 230 and the substrate 10. Between the intermediate layer 23 and the substrate 10, a transition region is formed due to melting, and this transition region is also called the mixing zone 232. In order to completely coat the friction surface, the laser can be moved relative to the substrate and / or the substrate can be moved relative to the laser. The movement direction of the laser is indicated by an arrow.

[0092] Figure 5 The cold gas injection 300 is shown again by way of example. During the cold gas injection 300, the coating material (i.e., the material of the later friction layer 33) is applied to the intermediate layer 23 in powder form at a very high speed. Here, the intermediate layer 23 is compacted at least on the surface, as shown here in the compaction region 335. Thereby, in particular, the stress in the intermediate layer 23 is reduced and the cracking risk is significantly reduced.

[0093] In addition to the metallic material 320 and the wear-resistant material 325, the coating material may also include other additives, such as copper.

[0094] In order to accelerate the coating materials 320, 325 accordingly, the process gas 310 is guided into the injection device at high pressure and heated, for example, via the heating element 315. The heating temperature is in the range of 300 °C to 1300 °C. In the injection device, the process gas 310 is mixed with the powdered coating material (i.e., the metallic material 320 and the wear-resistant material 325), and the heating temperature is lower than the melting temperature of the coating material.

[0095] Then, the powder-gas mixture is guided through a converging-diverging nozzle (Laval nozzle 305). This results in the powder-gas mixture being accelerated to a very high speed, especially to supersonic speed. In addition, the powder-gas mixture is strongly cooled.

[0096] The strongly accelerated powdered coating material can be guided onto the intermediate layer 23 in the injection beam 328. Due to the high kinetic energy, the powdered coating materials 320, 325 then firmly connect to the intermediate layer 23. The coated material 330 forms the friction layer 33. In the friction layer 33, the wear-resistant material (e.g., particles) 325 is at least partially or completely embedded in the metallic material 320.

[0097] In order to completely coat the intermediate layer, the injection beam 328 or the Laval nozzle 305 can be moved relative to the substrate, and / or the substrate can be moved relative to the injection beam 328 or the Laval nozzle 305. The movement direction of the injection beam is indicated by an arrow.

[0098] Figure 6Highly magnified schematic view showing a cross-section of the coating 13. The coating 13 is applied to the substrate 10, in particular to the friction surface of the substrate 10 (here made of gray cast iron). The coating 13 is a two-layer coating comprising an intermediate layer 23 and a friction layer 33. The intermediate layer 23 is applied to the substrate 10 by laser cladding welding. A mixing zone 232 is formed between the substrate 10 and the intermediate layer, which is here configured to be very thin (e.g., less than 0.5 μm) compared to the layer thicknesses of the respective layers. Due to the laser cladding welding, a material-locking, in particular metallurgical, bond is formed. After the laser cladding welding, the intermediate layer 23 has a high roughness (compared to the substrate). This results in the friction layer 33 applied by cold gas injection adhering well and substantially form-locked to the intermediate layer 23. In the illustrated embodiment, the particulate wear-resistant material (such as tungsten carbide) 325 is at least partially embedded in the metallic material 320 of the friction layer 33. Some of the particles are completely surrounded by the matrix of the metallic material 320, while others are exposed on the surface and only partially embedded or surrounded. It is understood that the friction layer 320 can have other compositions and can in particular be made of the metallic material 320.

[0099] For example, the illustrated friction layer may have a thickness d of approximately 200 μm R . The intermediate layer may have a thickness d of approximately 125 μm Z .

[0100] List of reference numerals

[0101] 1 Brake element

[0102] 2 Hub

[0103] 10 Substrate

[0104] 11 First side

[0105] 12 Friction surface

[0106] 13 Coating

[0107] 14 Second side

[0108] 15 Friction surface

[0109] 16 Coating

[0110] 23 Intermediate layer

[0111] 26 Intermediate layer

[0112] 33 Friction layer

[0113] 36 Friction layer

[0114] 100 Provide substrate

[0115] 200 Laser cladding weld intermediate layer

[0116] 210 Laser beam

[0117] 220 Material of the intermediate layer

[0118] 230 Coated material

[0119] 232 Mixing zone

[0120] 234 Molten pool

[0121] 236 Heat affected zone

[0122] 240 Protective gas

[0123] 300 Cold gas injection of the friction layer

[0124] 305 Laval nozzle

[0125] 310 Process gas

[0126] 315 Heating element

[0127] 320 Metal material

[0128] 325 Wear-resistant material

[0129] 328 Jet beam

[0130] 330 Coated material

[0131] 335 Compaction area

[0132] M central axis

Claims

1. A coated brake element (1), in particular a brake disc or a brake drum, wherein the coated brake element (1) has A base body (10) and at least one friction surface (12, 15), wherein the friction surface (12, 15) is arranged on the base body (10); A coating (13, 16) is arranged on at least one friction surface (12, 15), wherein the coating (13, 16) comprises an intermediate layer (23, 26) and a friction layer (33, 36). The intermediate layer (23, 26) is arranged between the base body (10) and the friction layer (33, 36) and is applied to the friction surface (12, 15) by means of laser coating welding, and The friction layer (33, 36) is applied by means of cold air spraying and comprises at least one metallic material.

2. The coated brake element (1) according to claim 1, wherein: The friction layer further comprises at least one wear-resistant material, and the wear-resistant material (325) in the friction layer (33, 36) is at least partially embedded in the metal material (320).

3. The coated brake element (1) according to claim 1 or 2, wherein: The coating (13, 16) consists of an intermediate layer (23, 26) and a friction layer (33, 36), and the coating (13, 16) is arranged directly on the at least one friction surface (12, 15) of the base body (10).

4. The coated brake element (1) according to claim 1, wherein: The base body has at least two friction surfaces (12, 15), which are optionally arranged on opposite sides (11, 14) of the base body (10).

5. The coated brake element (1) according to claim 1, wherein: The substrate (10) comprises at least one of the following materials, or is made of at least one of the following materials: Grey cast iron; Cast steel; steel; Aluminum, especially cast aluminum; Aluminum-based alloys; titanium; Titanium-based alloys; ceramics; polymer; Metal polymers; or Composite materials.

6. The coated brake element (1) according to claim 1, wherein: The intermediate layer (23, 26) forms a mixed zone (232) with the base body, which in the coated brake element (10) has a thickness of 0.05 to 100 μm, or in the range of 0.5 to 50 μm, or in the range of 0.5 to 20 μm, or in the range of 0.6 to 1 μm.

7. The coated brake element (1) according to claim 1, wherein: The intermediate layer (23, 26) has a layer thickness in the range of 10 μm to 1500 μm, or in the range of 20 μm to 500 μm, or in the range of 25 μm to 250 μm.

8. The coated brake element (1) according to claim 1, wherein: The intermediate layer (23, 26) comprises at least one of the following materials, or is made of one of the following materials: nickel; Nickel-based alloys; titanium; Titanium alloys; copper; Copper alloys; Cobalt-chromium alloy; Aluminium alloy; and / or Iron-based alloy.

9. The coated brake element (1) according to claim 1, wherein: The intermediate layers (23, 26) have a width of 8*10 -6 / K to 25*10 -6 / K, or within the range of 9*10 -6 / K to 18*10 -6 / K, or within the range of 13*10 -6 / K to 17*10 -6 / K, and / or The intermediate layer (23, 26) has a thermal conductivity in the range of 15 W / (mK) to 450 W / (mK), or in the range of 50 W / (mK) to 300 W / (mK), or in the range of 80 W / (mK) to 100 W / (mK).

10. The coated brake element (1) according to claim 1, wherein: The friction layer has a layer thickness in the range of 10 μm to 500 μm, or in the range of 20 μm to 400 μm, or in the range of 25 μm to 250 μm.

11. The coated brake element (1) according to claim 1, wherein: The metal material (320) of the friction layer (33, 36) comprises at least one of the following materials or is made of one of the following materials: steel; Iron-based alloys; nickel; Nickel-based alloys; titanium; Titanium-based alloys; copper; Copper-based alloys; Aluminium; or Aluminum based alloys.

12. The coated brake element (1) according to claim 1, wherein: The wear-resistant material (320) comprises at least one of the following materials or is made of one of the following materials: Tungsten carbide; Boron carbide; Titanium carbide; Iron carbide; Silicon carbide; Silicon nitride; Chromium carbide; Niobium carbide; Titanium nitride; Alumina; Zirconia; Furthermore, the wear-resistant material (320) exists in the friction layer (33, 36) in the form of particles and / or fibers.

13. The coated brake element (1) according to claim 1, wherein: The friction layer (33, 36) has a thickness of 8*10 -6 / K to 25*10 -6 / K, or within the range of 9*10 -6 / K to 18*10 -6 / K, or within the range of 13*10 -6 / K to 17*10 -6 / K, and / or The friction layer (33, 36) has a thermal conductivity in the range of 15 W / (mK) to 450 W / (mK), or in the range of 50 W / (mK) to 300 W / (mK), or in the range of 80 W / (mK) to 100 W / (mK).

14. Braking device comprising at least one coated brake element (1) according to one of claims 1 to 13, wherein: The brake element is arranged to be rotatable; The brake device also includes at least one brake lining which is movably arranged relative to the brake element and is configured to cooperate with a friction surface (12, 15) of at least one coating of the brake element (1) to achieve a braking effect on the brake element (1).

15. Method for producing a coated brake element (1), in particular a brake disc or a brake drum, according to one of claims 1 to 13, wherein: The method includes the following: Providing (100) a base body (10), the base body (10) having at least one friction surface (12, 15); Laser coating and welding (200) the intermediate layer (23, 26) to the at least one friction surface (12, 15); as well as The coating material is sprayed (300) onto the intermediate layer (23, 26) with cold gas to form the friction layer (33, 36) at the same time. The coating material includes a metal material (320) or is made of a metal material.

16. Method for producing a coated brake element (1) according to claim 15, wherein: The coating material also includes a wear-resistant material (325) and / or a precursor of a wear-resistant material, and The wear-resistant material (325) is at least partially embedded in the metal material (320) when the cold gas is sprayed, and / or The wear-resistant material (325) and / or a precursor of the wear-resistant material is at least partially embedded in the metal material (320) before the cold gas spraying, and / or The precursor of the wear resistant material is chemically converted into the wear resistant material during the cold gas spraying (325).

17. Method for producing a coated brake element (1) according to claim 15 or 16, wherein: The method also includes machining the friction surface (12, 15) to be coated, wherein: The processing is performed before the laser coating welding (200), and Processing includes at least one of the following steps: - spraying at least one friction surface (12, 15); - mechanically processing the at least one friction surface (12, 15), in particular mechanically roughening or smoothing the at least one friction surface (12, 15); - laser processing of at least one friction surface (12, 15), in particular laser cleaning and / or laser structuring, and / or - Temperature control of at least one friction surface (12, 15).

18. Method for producing a coated brake element (1) according to one of claims 15 to 17, wherein: The laser coating welding (300) is a laser cladding welding method, a high-speed laser cladding welding method or an ultra-high-speed laser cladding welding method.

Images