Brake disc for a friction brake of a motor vehicle and method for producing the same

Description

[0001] The invention relates to a brake disc for a friction brake of a motor vehicle, comprising a friction section with at least one friction surface and a fastening section for fastening to the vehicle, wherein the friction section and the fastening section are formed on a base body made of grey cast iron or steel and a wear protection layer is welded to the friction section as a friction surface by laser deposition welding.

[0002] Furthermore, the invention relates to a method for producing a brake disc for a friction brake of a motor vehicle, comprising providing a base body made of grey cast iron or steel, which extends over a friction section with at least one friction surface and a fastening section for fastening to the vehicle, and applying a wear protection layer at least in the region of the friction surface by laser deposition welding.

[0003] Brake discs are typically made of gray cast iron. Gray cast iron is characterized by its high volumetric heat capacity and good thermal shock resistance. Furthermore, it is a cost-effective material, and the production of gray cast iron brake discs is easily controlled. However, the material's high tendency to corrosion and its high wear during vehicle operation are problematic. Corrosion leads to visual defects, as red rust can develop within a very short period of time, which is directly visible through frequently used open rims. The material's high tendency to corrosion can lead to increased surface deterioration in economical driving or in electric and hybrid vehicles with high levels of recuperation due to the infrequent braking, necessitating early replacement of the brake disc.

[0004] Ceramic brake discs are also known. While they offer a long service life and excellent durability, their very high price has prevented them from being adopted for mass production. As an alternative, it has been proposed to apply a wear-resistant coating to a gray cast iron base body in the area of the friction surfaces. Such solutions also achieve significantly longer service life and durability compared to pure gray cast iron brake discs, but are significantly more cost-effective than ceramic brake discs.

[0005] Pure corrosion protection coatings such as temporary paint, zinc, or powder coatings are unsuitable for this purpose, as they are abraded from the friction surface during the first braking applications and are unable to provide lasting corrosion protection. Such corrosion protection coatings are particularly suitable for protecting non-frictionally stressed sections of a brake disc and, if necessary, for temporarily preserving an attractive surface appearance of the friction surface during delivery of new vehicles.

[0006] A generic brake disc with a wear protection layer and a generic manufacturing method therefor are known, for example, from WO 2020 / 234144 A1 and WO 2021 / 008744 A.

[0007] In conventional brake discs of this type, the interface between the wear protection layer—which can be, for example, a non-oxide ceramic material or a metal alloy with increased wear resistance compared to the base material—and the base body, and possibly also one or more intermediate layers on it, is exposed to the environment and therefore susceptible to corrosion. This can lead to delamination of the wear protection layer at the inner and outer edges of the friction surface. It has been shown that the outer edge of the friction surface is particularly affected, presumably because dripping water can collect there particularly easily in the installed position of the brake disc.

[0008] Conventional corrosion protection coatings are not suitable for completely suppressing crevice corrosion in this area over the long term, partly due to their proximity to the friction surface. A sacrificial coating with a zinc alloy offers only temporary protection, as zinc, being the least noble component, is the first to dissolve. Paints are suitable for keeping a corrosive medium away from a welded wear protection layer and the base body. However, paints are sensitive to impact and tend to experience localized layer flaking, for example, in the event of stone chips. As soon as the welded wear protection layer or the base body is exposed due to flaking of the paint layer, an increased corrosion attack occurs, as the surface conditions are very unfavorable for the corrosion rate. This results in a significantly faster and more aggressive corrosion attack. Therefore, in this case, no permanent corrosion protection effect is achieved.

[0009] Furthermore, from US 2013 / 161132 A, corresponding to DE 10 2011 089 864 A1, it is known to apply a wear protection layer, which is applied by flame spraying or arc welding, to the base body beyond the friction surface in an area angled to the friction surface, where it also ends.

[0010] Masoumeh et al., "Investigation of stand-off distance effect on structure, adhesion and hardness of copper coatings obtained by the APS technique," from the Journal of Theoretical and Applied Physics (2018) 12:85-91, describe problems with flame spraying and shed light on the influence of the distance between the spray head and the surface to be coated on the microstructure of the coating. With greater distance, the defects become larger. Thin layers result in insufficiently covered areas.

[0011] The invention is based on the object of remedying this problem. In particular, the invention aims to further increase the service life of brake discs with a laser-welded wear protection layer.

[0012] This object is achieved by a brake disc according to patent claim 1. Such a disc is characterized in particular in that the wear protection layer on the base body extends beyond the friction surface into a region angled to the friction surface and ends there, and the wear protection layer is applied in the angled region of the base body so that it covers the base body and leaves no gaps. Although the wear protection layer ends in this region, the susceptibility to corrosion is significantly reduced because the point at which corrosion can now occur is significantly spaced from the friction surface. Any corrosion at the end of the wear protection layer therefore no longer impairs the bond between the wear protection layer and the material of the base body or any additional layers arranged in between for the purpose of promoting adhesion or the like in a functionally relevant area.The service life of the brake disc with wear protection layer according to the invention is thus considerably extended.

[0013] Special embodiments of a brake disc according to the invention are the subject of further patent claims.

[0014] In particular, it can be provided that a contact plane exists at the friction surface between the wear protection layer and the base body, and that the wear protection layer, which continues into the angled area, seals the edge of that contact plane. This significantly extends the path of corrosion attack penetrating the friction surface area, thereby further increasing the service life of the brake disc.

[0015] According to another special embodiment, the friction surface transitions directly or via a chamfer into a peripheral section perpendicular to the friction surface. The wear protection layer extends uninterrupted from the friction surface into the chamfer or the peripheral section. The wear protection layer can end in the area of the chamfer or the peripheral section.

[0016] The layer thickness in the angled area preferably corresponds approximately to the layer thickness on the friction surface, so that during build-up welding, approximately identical welding parameters can be used in both areas, enabling a preferably uninterrupted application of the wear protection layer over the friction surface and the angled area. The layer thickness of the wear protection layer in the angled area is preferably 80 to 120% of the layer thickness on the friction surface, measured perpendicular to the respective substrate.

[0017] According to a further special embodiment, the wear protection layer can have an edge section in the angled region, wherein the edge section tapers in layer thickness towards the edge of the wear protection layer.

[0018] According to another special embodiment, an additional corrosion protection layer, in particular of the type explained above, is provided, which extends over the wear protection layer at least in the angled area and also over surface sections of the brake disc outside the wear protection layer. This delays corrosion attack on said interface and further increases the service life of the brake disc. It is advantageous for this purpose that the edge of the wear protection layer is significantly spaced from the friction surface and is therefore not affected by braking. The corrosion protection layer can also be applied over the friction surface during production, as this facilitates application. In the area of the friction surface, however, the corrosion protection layer is removed within a few braking operations.It only remains in those areas that are not affected by the brake shoes of the friction brake and there it exerts its protective effect against corrosion.

[0019] In one design variant, the wear protection layer is bonded directly to the material of the base body. Unlike thermal spraying processes such as flame spraying, laser cladding slightly melts the material of the base body, resulting in a particularly tight bond. Surface pretreatment, as required with thermal spraying processes, which only create a mechanical bond, is unnecessary with laser cladding. The latter allows for a single-layer buildup of wear protection directly on the material of the base body.

[0020] In another design variant, a two- or multi-layer structure is provided for wear protection. The wear protection layer is applied to at least one intermediate layer, which in turn is bonded to the material of the base body by laser deposition welding.

[0021] The above-mentioned object is further achieved by a method for producing a brake disc for a friction brake of a motor vehicle according to patent claim 7. The method comprises providing a base body made of gray cast iron or steel, which extends over a friction section with at least one friction surface and a fastening section for vehicle-side fastening, and applying a wear-protection layer at least in the region of the friction surface by laser deposition welding using a welding head. It is characterized in that when an edge of the friction surface is reached, the welding beam is tilted in order to continue welding into a region of the brake disc that is angled to the friction surface and beyond the friction surface, wherein the distance of the welding head to the respective surface is kept constant.

[0022] This makes it possible to produce a brake disc of the type described above with a long service life, in particular with high resistance to corrosion-related damage to the adhesion of the wear protection layer, relatively easily and cost-effectively.

[0023] Particular embodiments of the method according to the invention are the subject of further patent claims.

[0024] For example, during welding, the brake disc can be rotated in the plane of the friction surface while the welding head is moved radially relative to the brake disc. This creates a spiral weld bead around the rotation axis, the turns of which overlap significantly, preferably by 70 to 95%, to achieve a uniform layer thickness. Such a process can be continued continuously, particularly beyond the edge of the friction surface, to efficiently create a chamfer and / or a peripheral section of the brake disc perpendicular to the friction surface.

[0025] According to a special version of the process, the wear-resistant layer is applied using a laser powder deposition welding process. A laser beam locally melts the base body, and any intermediate layer already applied to it, and a powder material is introduced into the melt. Depending on the type of powder material, this material can also be melted in the process. Using a laser welding head, areas angled to the friction surface can be easily reached, and comparable welding parameters can be maintained for both areas. In particular, the distance of the welding head from the respective surface can be kept constant.

[0026] In principle, however, other deposition welding processes are also possible, as described, for example, in WO 2020 / 234144 A1 and WO 2021 / 008744 A. The relevant content of these documents is hereby expressly incorporated into the present disclosure.

[0027] According to another special embodiment of the process, after the wear-resistant layer has been applied, an additional corrosion protection layer can be applied to sections of the base body not covered by the wear-resistant layer. For this purpose, the corrosion protection paints, zinc coatings, and powder coatings mentioned above can be used, for example.

[0028] Preferably, the wear protection layer can be overlapped by the corrosion protection layer in the angled area in order to further increase the corrosion resistance against damage to the adhesion of the wear protection layer.

[0029] Materials that offer greater wear resistance than the base material, in particular greater wear and corrosion resistance, can be used for the wear protection layer. The material for the wear protection layer can be a non-oxide ceramic material and / or a metal or a metal alloy. In preferred embodiments, a carbide, a boride, a nitride, or mixtures thereof are used as the non-oxide ceramic material. Carbides, in particular chromium carbide, tungsten carbide, and mixtures containing these are preferably used. Suitable metals or metal alloys include, for example, iron and iron alloys. Alloying components that can be used include, for example, nickel, chromium, and / or manganese.

[0030] The material for the wear-resistant coating can be prepared as a powder. In particular, the powder can be used to create a wear-resistant coating in which the ceramic components are present in the form of particles embedded in a metal alloy matrix.

[0031] The invention is explained in more detail below with reference to exemplary embodiments illustrated in the drawing. The drawing shows: Figure 1 is a schematic view of a brake disc in section according to an embodiment of the invention, Figure 2 is a detailed view of the friction surface and an adjacent angled area of the embodiment of Figure 1 , Figure 3 a detailed view of the friction surface and an adjacent angled area analogous Figure 2 for a modified second embodiment, Figure 4 shows a detailed view of the friction surface and an adjacent angled area analogous Figure 2for a modified third embodiment, Figure 5 shows a detailed view of the friction surface and an adjacent angled area analogous Figure 2 for a modified fourth embodiment, Figure 6 a detailed view of the friction surface and an adjacent angled area analogous Figure 2 for a modified fifth embodiment, Figure 7 shows a detailed view of the friction surface and an adjacent angled area analogous Figure 2 for a modified sixth embodiment, Figure 8 shows a detailed view of the friction surface and an adjacent angled area analogous Figure 2 for a modified seventh embodiment, and in Figure 9 a representation to illustrate the production of the wear protection layer.

[0032] The present invention relates to a process-related further development of a laser powder deposition welding process for wear-resistant friction surfaces 3 on brake discs 1 with a base body 2 made of grey cast iron or steel and, associated therewith, to a novel design of such brake discs 1.

[0033] The advantages of a welded wear protection layer 3 as a friction surface with a correspondingly designed material system lie in high corrosion resistance on the highly stressed friction surface combined with high wear minimization, which leads to a long service life and durability and also reduces the emission of friction particles. Suitable material systems are described, without limitation, for example, in WO 2020 / 234144 A1 and WO 2021 / 008744 A and can be used here.

[0034] However, the process engineering development is expressly not tied to a specific material system, but includes all wear protection layer materials suitable for laser deposition welding processes, since the primary aim here is a process engineering development for the benefit of corrosion protection.

[0035] The outstanding braking performance of wear-resistant friction surfaces 3 in combination with matched brake pads was demonstrated on test benches. Furthermore, wear on the brake disc 1 and the brake pads was significantly reduced compared to an uncoated brake disc made of the same material as the base body 2.

[0036] Typically, material is applied during build-up welding only at the friction surface. Without further measures, the inner and outer edges of the contact plane K between the wear-protection layer 3 and the substrate are exposed to the environment, so that corrosion can occur directly at the interface between the wear-protection layer 3 and its substructure, whether directly at the material of the base body 2 or an intermediate layer or an intermediate layer system for adhesion promotion, so that the wear-protection layer 3 can be partially removed by corrosion.

[0037] This is counteracted in the present case by a continuation of the wear protection layer 3, which radially covers the edge of the contact plane K, whereby the location of a possible corrosion attack is shifted away from said contact plane K.

[0038] The applied wear protection layer 3 can, for example, be applied in a spiral pattern. For this purpose, the brake disc 1 is set in rotation in the plane of its friction surface 3a. A radially movable welding head 10 with a powder nozzle and coaxial laser beam moves, for example, from the innermost radius of the friction surface 3a of the brake disc 1 radially to the outermost radius, thus applying a coating in a spiral pattern whose individual turns overlap.

[0039] In principle, the welding beam 11 of the welding head 10 can be aligned perpendicular to the friction surface. However, by inclining the welding head 10 by up to + / - 45° to the perpendicular to the friction surface, preferably in a radial direction, back reflections of the laser beam from the workpiece into the optical beam path can be better avoided.

[0040] It is recommended to keep the distance of the welding head 10 to the workpiece surface as constant as possible in order to achieve good and, above all, uniform adhesion of the wear protection layer 3.

[0041] In the case of brake discs 1 which have a chamfer 4 on the edge of the friction surface 3a at the transition to a circumferential section 5 perpendicular to the friction surface 3a, radially inward and / or outward, if the welding head were guided solely in a plane parallel to the friction surface 3a in the region of such a chamfer 4, there would be a significant change in the distance between the nozzle of the welding head 10 and the workpiece surface, with unsatisfactory quality of the wear protection layer 3. Both the completeness of the wear protection layer 3 and the adhesion would be significantly impaired in the region of the chamfer 4. The result would be an incomplete, incomplete and / or non-adherent wear protection layer at the chamfer ends. In this region, liquid media such as water with dissolved salts could penetrate into the contact plane and cause crevice corrosion or contact corrosion.

[0042] Since the material of the base body 2 of the brake disc 1 is preferably gray cast iron, a very rapid corrosion effect and rapid corrosion progression occur in the presence of an aqueous corrosion medium, since the gray cast iron, as a less noble alloy compared to the material of the wear protection layer 3, is destroyed by electrochemical erosion. Due to the associated increase in volume due to the formation of iron oxide, the wear protection layer 3 could be lifted up and thus removed.

[0043] According to the invention, however, a well-adhering wear protection layer extending beyond the friction surface ensures corrosion protection at this particularly sensitive geometric location and prevents the formation of gaps and / or detachment of the wear protection layer 3. The service life of the brake disc 1 is significantly extended by this design.

[0044] To prevent gap formation and / or incomplete application of the wear protection layer 3, the bonding of the wear protection layer 3 and the completeness of the wear protection layer on the chamfer 4 and, if applicable, on the circumferential section 5 must be ensured at all times during the process, and, above all, the initial and final areas of the process must be well bonded. It should be noted that corrosion attack can never be completely prevented. However, in this way, the corrosion attack should not occur directly on the friction surface 3a, but rather at a significant distance from it, for example, at the boundary between the tapered chamfer 4 and the outer circumferential section 5a and / or the inner circumferential section 5b of the brake disc 1.

[0045] In this way, a corrosion attack must first occur across the chamfer 4 and can only hit the edge Ra or Rb of the contact plane K of the friction surface 3a much later. This allows a significantly delayed corrosion effect on the friction surface 3a. In other words, the corrosion attack no longer occurs linearly to the extent of the contact plane K of the friction surface, but at the angle of attack of the chamfer 4 of, for example, 45° and significantly offset from the contact plane K towards the base body 2, as shown in the Fig. 2 to 8 easy to recognize.

[0046] For this purpose, the wear protection layer 3 extends beyond the friction surface 3a and extends into the chamfers 4 and / or the peripheral sections 5 or 5a and / or 5b. The gap-free connection of the wear protection layer 3 to the substrate at the chamfers 4 and the peripheral sections 5 or 5a and / or 5b is ensured, as is complete coverage without defects.

[0047] As mentioned, the wear protection layer 3 is applied completely and with good adhesion to the chamfers 4 and / or the circumferential sections 5 or 5a and / or 5b perpendicular to the friction surface, and can taper in thickness. A continuous coating of the brake disc 1 over the entire circumference is avoided, since the material of the wear protection layer 3 would be expensive and the manufacturing effort required for this would be high.

[0048] For laser deposition welding on a bevel 4 or a peripheral section 5, the welding head 10 is tilted at the beginning and / or at the end of the process, as shown in Fig. 9is shown. The angular position of the welding head 10 is controlled during the ongoing spiral application of the wear-resistant layer 3. Both at the beginning and at the end of the build-up welding process, the angular position and the height of the welding head 10 are adapted to the position of the chamfer 4 and the peripheral section 5, such that the working distance of the welding head 10 from the workpiece surface lies within a relatively narrow tolerance band, thereby achieving a completely covering, gap-free coating in these areas.

[0049] For example, the brake disc 1 can be coated with a wear-resistant layer 3 from the inside out in a counterclockwise process. Other possibilities arise from a coating strategy that moves from the outside in. Furthermore, the direction of rotation of the brake disc 1 can be varied from a counterclockwise process to a clockwise process, and the starting positions can be selected from the outside or the inside. Since the different coating strategies result in a complete coating on the friction surface, these variations play a minor role in the final result. In each of the coating strategies, however, the welding head 10 is tilted at the beginning and end of the welding process in order to apply the complete wear-resistant layer 3 to the friction surface 3a as well as to the chamfers 4 and / or peripheral sections 5 beyond the friction surface within a single production step.

[0050] This allows you to Figures 1 to 8 illustrated embodiments, without the present disclosure being limited to these embodiments.

[0051] How Fig. 1 As shown, a brake disc 1 according to the invention for a friction brake of a motor vehicle has a friction section 6 with at least one flat friction surface 3a, in this case, for example, two opposing, annular friction surfaces, as well as a fastening section 7 for vehicle-mounted fastening. The fastening section 7 is cup-shaped in this case and is radially surrounded by the friction section 6, but can also be designed differently than shown.

[0052] Both the friction section 6 and the fastening section 7 are formed on the above-mentioned base body 2, which is preferably made of grey cast iron, but can also be made of steel.

[0053] At least one friction surface 3a is located on the friction section 6, with a wear-resistant coating 3 applied by laser deposition welding. The wear-resistant coating 3 is preferably applied directly to the cast surface. The cast surface does not require any special preparation for this purpose.

[0054] The friction section 6 can be designed in the form of an annular disc, on the opposite annular surfaces of which there is a friction surface 3a.

[0055] As also already explained, the wear protection layer 3 on the base body 2 continues beyond the friction surface 3a into a region 3b angled to the friction surface 3a, in order to end there, and is applied in the angled region 3b of the base body 2 in a covering manner and without a gap to the base body 2.

[0056] The angled region 3b encloses an angle greater than 0° with the friction surface 3a, preferably 15 to 95° and more preferably 30° to 90°.

[0057] The area 3b which is angled to the friction surface 3a can be formed by the chamfers 4 already explained above (cf. Fig. 2, 3 , 5 and 7 ). The angled area 3b can also include the circumferential sections 5 or 5a and 5b perpendicular to the friction surface 3a (cf. Fig. 3 and 5 ), which adjoin the chamfers 4. If the chamfers 4 are omitted, the angled region 3b can be formed by the circumferential sections 5 or 5a and 5b perpendicular to the friction surface 3a (cf. Fig. 4 and 6 ).

[0058] The wear protection layer 3 is designed such that it ends in the angled area 3b. If opposing wear protection layers 3 are provided, they are unconnected to each other.

[0059] At the friction surface 3a there is a contact plane K between the wear protection layer 3 and the base body side of the same. In all embodiments of the Fig. 1 to 8 The wear protection layer 3, which continues into the angled region 3b, seals the edge Ra, Rb of that contact plane K from the environment. The contact point of the wear protection layer 3 exposed to the environment is thus spaced from the contact plane K to the side of the base body 2.

[0060] In the Fig. 2 In the illustrated embodiment, the friction surface 3a transitions via a chamfer 4 into a circumferential section 5 perpendicular to the friction surface 3a. The wear protection layer 3 continues uninterrupted from the friction surface 3a into the chamfer 4 and ends radially flush with the circumferential section 5.

[0061] The layer thickness of the wear protection layer 3 remains approximately constant, measured perpendicular to the respective substrate. However, the layer thickness of the wear protection layer can also vary slightly. For example, the layer thickness in the angled area 3b can be approximately 80 to 120% of the layer thickness on the friction surface 3a, measured perpendicular to the respective substrate.

[0062] The layer thickness of the wear protection layer 3 on the friction surface 3a is 10 µm to 500 µm, preferably 50 µm to 200 µm.

[0063] Fig. 3 shows as a second embodiment a modification of Fig. 2 with increased layer thickness of the wear protection layer 3. In addition, this can, in contrast to Fig. 2 be continued beyond the chamfer 4 into the area of the circumferential section 5, whereby the path for corrosion through to the contact plane K is further increased.

[0064] Fig. 4shows as a third embodiment a modification of Fig. 2 and 3 , in which no chamfer 4 is provided on the edges of the friction surface 3a. In this case, the friction surface 3a merges directly into the circumferential section 5 perpendicular to the friction surface 3a. The wear protection layer 3, in turn, continues uninterrupted from the friction surface 3a into the circumferential section 5. Here, too, the edge Ra, Rb of the contact plane K is covered and sealed by the wear protection layer 3 in the angled area 3b. The layer thickness of the wear protection layer 3 remains approximately constant, although this is always measured perpendicular to the respective substrate, and deviations in the above-mentioned range of 80 to 120% are possible.

[0065] Fig. 5 shows as a fourth embodiment a variation of the second embodiment according to Fig. 3. The wear protection layer 3 here has an edge section in the angled region 3b, in which the layer thickness tapers towards the edge of the wear protection layer 3. The taper 9 here only affects the area that covers the peripheral section 5, but, in a modification thereof, can already begin in the area of the chamfer 4, but not in the area of the friction surface 3a.

[0066] Fig. 6 shows as a fifth embodiment a variation of the third embodiment according to Fig. 4 . As in Fig. 5 In the angled region 3b, the wear protection layer 3 again has an edge section in which the layer thickness tapers towards the edge of the wear protection layer 3. Due to the lack of a chamfer 4, the taper 9 tapers towards the edge of the wear protection layer 3 at the peripheral section 5.

[0067] Fig. 7 shows as a sixth embodiment a taper 9 of the wear protection layer 3 in the area of the chamfer 4.

[0068] Furthermore, Fig. 7 the additional application of a corrosion protection layer 8. This corrosion protection layer 8 consists of a paint, a zinc, or powder coating without requiring high wear resistance for a friction surface 3a and is considerably more cost-effective than the wear protection layer 3. One example is a water- or solvent-based zinc flake coating, which can be sprayed on. The corrosion protection layer 8 is applied to surface sections outside the friction surface 3a. It can also overlap the wear protection layer 3 in the angled area 3b in order to delay corrosion attack at the interface between the wear protection layer 3 and its substrate, thereby further increasing the service life of the brake disc 1.

[0069] Such an overlap by a corrosion protection layer 8 can also be achieved in the embodiments according to the Fig. 1 to 6 be provided. In the Fig. 2 to 4 This is illustrated by way of example for the outer edge of the brake disc 1, but can optionally also be provided on the inner edge and any other edge points. The overlap can be limited to selected edge areas of the wear protection layer 3 or can cover the entire edge area of the wear protection layer 3.

[0070] In the embodiments explained above, the wear protection layer 3 is directly bonded to the material of the base body 2 by laser deposition welding. The additional material for the wear protection layer 3 is fused into the material of the base body 2, as the latter is slightly melted during laser deposition welding, and does not merely adhere to the surface in the manner of a weld bead, as is typically the case with thermal welding processes. This ultimately enables a single-layer structure of the wear protection directly on the material of the base body 2 with sufficient bonding.

[0071] However, it is also possible to provide a multi-layer structure for wear protection by applying the following as in Fig. 8As shown by way of example, the wear protection layer 3 is applied to at least one intermediate layer 3' by laser deposition welding. The intermediate layer 3' is in turn bonded to the material of the base body 2 by laser deposition welding. Such a multi-layer structure can be used analogously in the Fig. 2 to 7 shown embodiments are used.

[0072] The intermediate layer 3' is preferably somewhat more ductile than the wear-resistant layer 3. For the intermediate layer 3', an iron-based alloy can be used, for example. The wear-resistant layer 3 also contains hard particles, in particular carbides, borides, and / or nitrides.

[0073] Fig. 9 shows a representation to illustrate a method for producing a brake disc 1 with wear protection layer 3 as explained above.

[0074] The method first involves providing the base body 2, which is preferably made of gray cast iron, but can also be made of steel. The base body 2 extends over the friction section 6 with at least one friction surface 3a and over a fastening section 7 for vehicle-mounted attachment. The friction section 6 and the fastening section 7 are preferably integral, i.e., formed in one piece with one another.

[0075] The base body 2 is, if necessary after manufacturing further functional surfaces, placed in a device for laser deposition welding, as in Fig. 9 In such a process, the wear protection layer 3 is then applied by laser deposition welding using a welding head 10, wherein the welding beam 11 of the welding head 10 is guided over the respective workpiece surface on the base body 2.

[0076] In a preferred embodiment, the brake disc 1 is rotated in the plane of the friction surface 3a, in this case about the axis A perpendicular to the brake disc 1. In addition, the welding head 10 is moved radially relative to the brake disc 1. The interaction of both movements creates a spiral-shaped weld bead whose adjacent turns overlap by approximately 70 to 95%.

[0077] When an edge Ra, Rb of the friction surface 3a is reached, the welding beam 11 of the welding head 10 is tilted, as shown in Fig. 9 is indicated by the reference number 10', in order to continue the welding in the area 3b of the brake disc 1 which is angled to the friction surface 3a beyond the friction surface 3a, in such a way that the welding head 10 continues to be moved at a constant distance over the surface of the workpiece, namely here it moves over the angled area 3b.

[0078] The welding beam 11 can be aligned essentially perpendicular to the workpiece surface. A deviation from a strictly perpendicular alignment of the welding beam 11 can be achieved by approximately + / - 45° without compromising the quality of the wear-resistant layer 3.

[0079] The welding process continues continuously beyond the friction surface 3a, thus not needing to be interrupted for the angled area 3b. The distance of the welding head 10 from the material surface remains constant throughout.

[0080] If angled areas 3b are to be passed over on both edges Ra, Rb of the friction surface 3a, welding is preferably started with one of the angled areas 3b and then welded continuously up to the other angled area 3b.

[0081] During laser cladding, the hard layer 3 is bonded to its substrate. The substrate material is slightly melted using a laser beam, and the material for the wear-resistant layer 3, preferably in powder form, is simultaneously applied.

[0082] If necessary, for a multi-layer structure, an intermediate layer 3' can first be bonded to the material of the base body 2 by laser deposition welding. The wear protection layer 3 is then welded onto this or several such intermediate layers 3'.

[0083] The wear protection layer 3 is in principle ready for use after the build-up welding, but may still be subjected to a smoothing process if necessary.

[0084] Furthermore, in one embodiment of the method, after applying the wear-resistant layer 3, a corrosion-protection layer 8 can be applied to sections of the base body 2 not covered by the wear-resistant layer 3. In this case, less resistant and significantly more cost-effective coatings are typically used, which do not require welding.

[0085] For manufacturing reasons, the corrosion protection layer 8 is preferably applied not only to the sections of the base body 2 not covered by the wear protection layer 3, but also to the wear protection layer 3. On the friction surface 3a, such a corrosion protection layer 8 is removed within a few braking operations, so that during operation of the brake disc, this area ultimately remains uncoated or can also be left uncoated during the coating process. However, the wear protection layer 3 can be or remain overlapped by the corrosion protection layer 8 in the angled area 3b in order to delay corrosion attack on the interface between the wear protection layer 3 and its substrate and thus further improve the service life of the wear protection layer 3 and brake disc 1. The overlap can reach up to the friction surface 3a, i.e.up to those areas which ultimately come into frictional engagement with the brake shoes of the friction brake.

[0086] The advantage of this approach is that there is no longer any gap between the laser-welded wear protection layer 3 and the base body 2, nor can there be one that could develop. Rather, the welded wear protection layer 3 adheres completely and well, even in the angled area 3b adjacent to the friction surface 3a, in particular the chamfers 4 and, if applicable, the circumferential sections 5. This reduces corrosion formation in areas of the brake disc 1 that are particularly relevant to its function, and prevents delamination of the wear protection layer 3. An additional corrosion protection layer 8 can further delay the onset of corrosion in the direction of the friction surface 3a.

[0087] The invention has been explained in more detail above with reference to exemplary embodiments and further modifications. In particular, individual technical features explained above in the context of further individual features can be implemented independently of these and in combination with further individual features, even if not expressly described, as long as this is technically feasible. The invention is therefore expressly not limited to the described exemplary embodiments and modifications, but encompasses all configurations defined by the patent claims. List of reference symbols

[0088] 1Brake disc 2Base body 3Wear protection layer 3'Intermediate layer 3aFriction surface 3bAngled area 4Bevel 5Circumferential section 5aOuter circumferential section 5bInner circumferential section 6Friction section 7Fastening section 8Corrosion protection layer 9Taper 10Welding head 10'Welding head, tilted 11Welding beam ARotation axis KContact plane Ra(radial) outer edge of the friction surface 3a Rb(radial) inner edge of the friction surface 3a

Claims

1. Brake disc (1) for a friction brake of a motor vehicle, comprising a friction section (6) with at least one friction surface (3a) and a mounting section (7) for vehicle-side attachment, wherein the friction section (6) and the mounting section (7) are formed on a base body (2) made of cast iron or steel, and a wear protection layer (3) is welded onto the friction surface (3a) of the friction section (6) by laser cladding, characterized in that the wear protection layer (3) extends on the base body (2) beyond the friction surface (3a) into an area (3b) angled relative to the friction surface (3a) and terminates there, and the wear protection layer (3) is applied in the angled area (3b) of the base body (2) in a covering and gap-free manner.

2. Brake disc (1) according to claim 1, characterized in that a contact plane (K) exists at the friction surface (3a) between the wear protection layer (3) and the base body-side substrate thereof, and the wear protection layer (3) extending into the angled area (3b) seals the edge of said contact plane (K).

3. Brake disc (1) according to claim 1 or 2, characterized in that the angled area (3b) is defined by a chamfer (4) and / or a circumferential section (5, 5a, 5b) perpendicular to the friction surface (3a), wherein the friction surface (3a) transitions directly or via the chamfer (4) into the circumferential section (5, 5a, 5b) perpendicular to the friction surface (3a), and the wear protection layer (3) is continuously extended from the friction surface (3a) into the chamfer (4) or the circumferential section (5, 5a, 5b).

4. Brake disc (1) according to any of claims 1 to 3, characterized in that the layer thickness of the wear protection layer (3) in the angled area amounts to 80 to 120% of the layer thickness at the friction surface (3a), each measured perpendicular to the respective substrate.

5. Brake disc (1) according to any of claims 1 to 4, characterized in that the wear protection layer (3) in the angled area (3b) comprises an edge section, wherein the edge section tapers (9) in layer thickness towards the edge of the wear protection layer (3).

6. Brake disc (1) according to any of claims 1 to 5, characterized in that a corrosion protection layer (8) is provided, which extends over the wear protection layer (3) at least in the angled area (3b) and further over surface sections of the brake disc outside the wear protection layer (3).

7. Brake disc (1) according to any of claims 1 to 6, characterized in that the wear protection layer (3) is directly materially bonded to the material of the base body (2), or that the wear protection layer (3) is applied onto an intermediate layer (3'), which in turn is materially bonded to the material of the base body (2) by laser cladding.

8. Method for producing a brake disc (1) for a friction brake of a motor vehicle, comprising: • Providing a base body (2) made of cast iron or steel, which extends over a friction section (6) with at least one friction surface (3a) and a mounting section (7) for vehicle-side attachment, • Applying a wear protection layer (3) at least in the area of the friction surface (3a) of the friction section (6) by laser cladding using a welding head (10), characterized in that upon reaching an edge (Ra, Rb) of the friction surface (3a), the laser cladding is continued beyond the friction surface (3a) into an area (3b) of the brake disc (1) angled relative to the friction surface (3a), wherein the distance of the welding head (10) to the respective surface is kept constant.

9. Method according to claim 8, characterized in that during cladding, the brake disc (1) is rotated in the plane of the friction surface (3a) and the welding head (10) is moved radially relative to the brake disc (1), and upon reaching the edge (Ra, Rb) of the friction surface (3a), the welding head (10) is tilted.

10. Method according to claim 8 or 9, characterized in that after applying the wear protection layer (3), a corrosion protection layer (8) is applied to sections of the base body not covered by the wear protection layer (3), wherein preferably the wear protection layer (3) in the angled area (3b) is overlapped by the corrosion protection layer (8).