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

Abstract

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 mounting, wherein the friction section (6) and the mounting section (7) are formed on a base body (2) made of gray cast iron or steel and have a wear-resistant layer (3) as the friction surface (3a) on the friction section (6), wherein the wear-resistant layer (3) extends beyond the friction surface (3a) on the base body (3) into an angled area (3b) and terminates there, characterized in that the wear-resistant layer (3) is welded on by laser cladding and is applied completely without defects and without gaps to the base body (2) in the angled area (3b) of the base body (2).

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 mounting section for vehicle-side attachment, wherein the friction section and the mounting section are formed on a base body made of gray cast iron or steel and a wear-resistant layer is welded onto the friction section as a friction surface by laser cladding.

[0002] Furthermore, the invention relates to a method for manufacturing a brake disc for a friction brake of a motor vehicle, comprising 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 attachment, and applying a wear protection layer at least in the area of ​​the friction surface by laser cladding.

[0003] Brake discs are typically made of gray cast iron. Gray cast iron is characterized by 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 relatively straightforward. However, the material's high susceptibility to corrosion and its rapid wear during vehicle operation are problematic. Corrosion leads to visual defects, as red rust can form very quickly, which is readily visible through the often-used open wheel rims. The material's strong corrosion tendency can lead to increased surface degradation in fuel-efficient driving or in electric and hybrid vehicles with high regenerative braking due to infrequent brake application, necessitating premature replacement of the brake disc.

[0004] Ceramic brake discs are also known, which, while offering a long service life and excellent durability, have not yet become established for mass production due to their very high price. As an alternative, it has been proposed to coat a gray cast iron base with a wear-resistant layer in the friction surface area. Such solutions also achieve a significantly longer service life and durability compared to pure gray cast iron brake discs, but are considerably less expensive 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 worn away from the friction surface during the first few braking operations and cannot provide lasting corrosion protection. Such corrosion protection coatings are primarily suitable for protecting non-friction-stressed sections of a brake disc and, if necessary, for temporarily preserving an attractive surface appearance of the friction surface when delivering new vehicles.

[0006] A generic brake disc with a wear-resistant layer and a generic manufacturing process for it are known, for example, from WO 2020 / 234144 A1 and WO 2021 / 008744 A.

[0007] In conventional brake discs of this design, the interface between the wear-resistant 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 material, 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-resistant 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 water can collect there especially easily in the installed position of the brake disc.

[0008] Conventional corrosion protection coatings are unsuitable for permanently suppressing crevice corrosion in this area, partly due to the proximity to the friction surface. For example, a sacrificial coating with a zinc alloy only offers temporary protection, as the zinc, being the least noble component, dissolves first. Paints are suitable for keeping a corrosive medium away from a welded-on wear-resistant coating and the base material. However, paints are sensitive to impact and tend to flake off locally, for example, when struck by stones. As soon as the welded-on wear-resistant coating or the base material is exposed due to paint flaking, increased corrosion occurs because the surface area is very unfavorable for the corrosion rate. This results in a significantly faster and more aggressive corrosion attack. Therefore, even in this case, no lasting corrosion protection is achieved.

[0009] The invention is based on the objective of providing a remedy for this problem. In particular, the invention aims to further increase the service life of brake discs with a laser-deposited wear protection layer.

[0010] This problem is solved by a brake disc according to claim 1. Such a disc is characterized in particular by the fact that the wear-resistant layer on the base body extends beyond the friction surface into an area angled relative to the friction surface and terminates there, and that the wear-resistant layer is applied in the angled area of ​​the base body in a fully covering and gap-free manner. Although the wear-resistant layer terminates in this area, this significantly reduces the susceptibility to corrosion, because the point at which corrosion can now occur is considerably further away from the friction surface. Any corrosion at the end of the wear-resistant layer therefore no longer impairs the bond between the wear-resistant layer and the material of the base body, or any additional layers arranged between them for the purpose of adhesion promotion or the like, in a functionally relevant area.The service life of the brake disc according to the invention with wear protection layer is thus considerably extended.

[0011] Special embodiments of a brake disc according to the invention are the subject of further patent claims.

[0012] In particular, it can be provided that a contact plane exists on the friction surface between the wear-resistant layer and the substrate on the base body, and that the wear-resistant layer, extending into the angled area, seals the edge of this contact plane. This significantly lengthens the path of any corrosion attack penetrating to the friction surface area and thus further increases the service life of the brake disc.

[0013] According to another special embodiment, the friction surface transitions directly or via a chamfer into a circumferential section perpendicular to the friction surface. In this case, the wear-resistant layer continues uninterrupted from the friction surface into the chamfer or the circumferential section. The wear-resistant layer may terminate in the region of the chamfer or the circumferential section.

[0014] The layer thickness in the angled area preferably corresponds approximately to the layer thickness on the friction surface, so that the welding parameters for overlay welding can be nearly identical in both areas, and a preferably continuous application of the wear-resistant layer across the friction surface and the angled area is possible. Preferably, the layer thickness of the wear-resistant layer in the angled area is 80 to 120% of the layer thickness on the friction surface, measured perpendicular to the respective substrate.

[0015] According to another special design, the wear protection layer can have an edge section in the angled area, wherein the edge section tapers in thickness towards the edge of the wear protection layer.

[0016] According to another special design, an additional corrosion protection layer, particularly of the type described above, is provided. This layer 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 at the interface and further increases the service life of the brake disc. It is advantageous 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 manufacturing, as this simplifies application. However, in the area of ​​the friction surface, the corrosion protection layer is worn away within just a few braking cycles.It remains only in those areas that are not covered by the brake shoes of the friction brake and unfolds its protective effect against corrosion there.

[0017] In one version, the wear-resistant layer is directly bonded to the base material. Unlike thermal spraying processes such as flame spraying, laser cladding melts the base material slightly, resulting in a particularly strong bond. Surface pretreatment, as required by thermal spraying processes which only create a mechanical bond, is unnecessary with laser cladding. This allows for a single-layer application of the wear protection directly onto the base material.

[0018] In another design variant, a two- or multi-layer structure is provided for wear protection. In this case, the wear-resistant layer is applied to at least one intermediate layer, which in turn is bonded to the base material by laser cladding.

[0019] The aforementioned problem is further solved by a method for manufacturing a brake disc for a friction brake of a motor vehicle according to 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 mounting section for vehicle-side attachment, as well as applying a wear-resistant layer at least in the area of ​​the friction surface by laser cladding using a welding head. It is characterized in that, upon reaching an edge of the friction surface, the welding jet is tilted in order to continue the cladding into an area of ​​the brake disc angled to the friction surface beyond the friction surface, whereby the distance of the welding head to the respective surface is kept constant.

[0020] This makes it relatively easy and inexpensive to manufacture a brake disc of the type described above with a long service life, in particular high resistance to corrosion-related damage to the adhesion of the wear protection layer.

[0021] Specific embodiments of the method according to the invention are the subject of further patent claims.

[0022] 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 axis of rotation, the turns of which overlap significantly, preferably by 70 to 95%, to achieve a homogeneous layer thickness. This process can also be continued continuously over the edge of the friction surface, in particular to efficiently create a chamfer and / or a circumferential section of the brake disc perpendicular to the friction surface.

[0023] In a specific implementation of the process, the wear-resistant layer is applied using a laser powder deposition welding process. A laser beam locally melts the base material, and optionally any intermediate layer already applied to it, and introduces a powder material into the molten material. Depending on the type of powder, it may also be melted in the process. A laser welding head allows for good access to areas angled relative to the friction surface, ensuring comparable welding parameters for both areas. In particular, the distance between the welding head and each surface can be kept constant.

[0024] In principle, however, other welding processes are also possible, such as those described in WO 2020 / 234144 A1 and WO 2021 / 008744 A. The relevant content from these documents is hereby expressly incorporated into the present disclosure.

[0025] According to another special embodiment of the process, after the application of the wear-resistant layer, 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 aforementioned corrosion protection paints, zinc coatings, and powder coatings, for example, can be used.

[0026] Preferably, the wear protection layer in the angled area can be overlapped by the corrosion protection layer in order to further increase the corrosion resistance against damage to the adhesion of the wear protection layer.

[0027] Suitable materials for the wear-resistant layer include those with higher wear resistance than the base material, particularly both higher wear and corrosion resistance. The wear-resistant layer material can be a non-oxide ceramic and / or a metal or metal alloy. Preferred non-oxide ceramic materials include carbides, borides, nitrides, or mixtures thereof. Carbides, especially chromium carbide, tungsten carbide, and mixtures containing these, are preferred. Suitable metals or metal alloys include, for example, iron and iron alloys. Alloying elements such as nickel, chromium, and / or manganese can be used.

[0028] The material for the wear-resistant coating can be prepared as a powder. In particular, a wear-resistant coating can be produced from the powder in which the ceramic components are present in the form of particles embedded in a metal alloy matrix.

[0029] The invention will now be explained in more detail with reference to exemplary embodiments illustrated in the drawing. The drawing shows: Fig. 1 a schematic view of a brake disc in section according to an embodiment of the invention, Fig. 2 a detailed view of the friction surface and an angled area adjoining it of the exemplary embodiment Fig. 1, Fig. 3 a detailed view of the friction surface and an angled area adjoining it analogously Fig. 2 for a modified second embodiment, Fig. 4 a detailed view of the friction surface and an angled area adjoining it analogously Fig. 2 for a modified third embodiment, Fig. 5 a detailed view of the friction surface and an angled area adjoining it analogously Fig. 2 for a modified fourth embodiment, Fig. 6 a detailed view of the friction surface and an angled area adjoining it analogously Fig. 2 for a modified fifth embodiment, Fig. 7 a detailed view of the friction surface and an angled area adjoining it analogously Fig. 2 for a modified sixth embodiment, Fig. 8 a detailed view of the friction surface and an angled area adjoining it analogously Fig. 2 for a modified seventh embodiment, and in Fig. 9. A diagram illustrating the production of the wear-resistant layer.

[0030] The present invention relates to a process-technical further development of a laser powder deposition welding for wear protection layer friction surfaces 3 on brake discs 1 with a base body 2 made of grey cast iron or steel and associated with a novel design of such brake discs 1.

[0031] The advantages of a welded-on wear-resistant layer 3 as a friction surface with a suitably designed material system lie in high corrosion resistance at the heavily stressed friction surface, combined with a high degree of 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.

[0032] However, the process engineering development is expressly not tied to a specific material system, but includes all wear protection layer materials suitable for laser cladding processes, since the primary aim here is a process engineering development to the advantage of corrosion protection.

[0033] The excellent braking performance of wear-resistant coating friction surfaces 3 in combination with matched brake pads was demonstrated on test benches. Furthermore, the wear of 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.

[0034] Typically, material is only applied to the friction surface during build-up welding. 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 substrate, be it the base material 2 itself, an intermediate layer, or an intermediate layer system for adhesion promotion, thus potentially causing the wear protection layer 3 to partially detach due to corrosion.

[0035] This is countered in the present case by a continuation of the wear protection layer 3, which radially covers the edge of the contact plane K, thereby moving the location of a possible corrosion attack away from said contact plane K.

[0036] The applied wear-resistant layer 3 can, for example, be applied in a spiral pattern. For this purpose, the brake disc 1 is rotated 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, the individual turns of which overlap.

[0037] The welding beam 11 of the welding head 10 can, in principle, be aligned perpendicular to the friction surface. However, by tilting the welding head 10 by up to + / - 45° to the perpendicular of 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.

[0038] It is recommended to keep the distance between the welding head 10 and the workpiece surface as constant as possible in order to achieve good and, above all, uniform adhesion of the wear protection layer 3.

[0039] For brake discs 1, which have a chamfer 4 at the edge of the friction surface 3a at the transition to a circumferential section 5 perpendicular to the friction surface 3a, radially inside and / or outside, guiding the welding head solely in a plane parallel to the friction surface 3a in the area of ​​such a chamfer 4 would result in 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 its adhesion would be significantly impaired in the area of ​​the chamfer 4. The consequence would be a wear protection layer that is not completely opaque, incomplete, and / or non-adherent at the chamfer ends. In this area, liquid media such as water with dissolved salts could enter the contact plane and cause crevice corrosion or contact corrosion.

[0040] 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 progress occur in the presence of an aqueous corrosive medium, as the gray cast iron, being a less noble alloy compared to the material of the wear-resistant layer 3, is destroyed by electrochemical erosion. Due to the associated increase in volume caused by the formation of iron oxide, the wear-resistant layer 3 could be lifted and thus detached.

[0041] According to the invention, a well-adhering wear-resistant layer extending beyond the friction surface ensures corrosion protection at this particularly sensitive geometric point and prevents the formation of gaps and / or detachment of the wear-resistant layer 3. This design significantly extends the service life of the brake disc 1.

[0042] To prevent gap formation and / or incomplete application of the wear-resistant layer 3, the bonding of the wear-resistant layer 3 and its completeness on the chamfer 4 and, if applicable, on the circumferential section 5 must be ensured at all times during the process, and especially the beginning and end areas of the process must be well bonded. It should be noted that corrosion attack can never be completely prevented. However, this should prevent corrosion from occurring 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.

[0043] In this way, corrosion must first occur across chamfer 4 and can only reach the edge Ra or Rb of the contact plane K of the friction surface 3a much later. This allows for a significantly delayed corrosion effect on the friction surface 3a. In other words, the corrosion attack no longer occurs linearly with respect to the extent of the contact plane K of the friction surface, but rather at the angle of inclination of chamfer 4, for example 45°, and significantly offset from the contact plane K towards the base body 2, as shown in the Fig. 2 to Fig. 8 clearly visible.

[0044] The wear protection layer 3 extends beyond the friction surface 3a and reaches into the chamfers 4 and / or the circumferential 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 circumferential sections 5 or 5a and / or 5b is ensured, as is complete coverage without defects.

[0045] 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 its thickness may taper towards the end. A continuous coating of the brake disc 1 over its entire circumference is avoided because the material for the wear protection layer 3 would be expensive and the manufacturing effort required would be high.

[0046] For laser cladding on a chamfer 4 or a circumferential section 5, it is provided that the welding head 10 is tilted at the beginning and / or at the end of the process, as shown in Fig. Figure 9 shows this process. During the ongoing spiral application of the wear-resistant layer 3, the angular position of the welding head 10 is controlled. Both at the beginning and at the end of the coating welding process, the angular position and the height of the welding head 10 are adjusted to the position of the chamfer 4 and the circumferential section 5, such that the working distance of the welding head 10 to the workpiece surface lies within a relatively narrow tolerance band, thereby achieving a completely covering, gap-free coating in these areas.

[0047] The brake disc 1 can, for example, be coated with a wear-resistant layer 3 from the inside out in a counterclockwise rotating process. Other possibilities arise from a coating strategy that proceeds from the outside in. Furthermore, the direction of rotation of the brake disc 1 can be varied from a counterclockwise to a clockwise rotating process, and the starting positions can be chosen to be either the outside or the inside. Since the different coating strategies result in a complete coating of the friction surface, these variations are of minor importance for 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 circumferential sections 5 beyond the friction surface within a single manufacturing step.

[0048] This allows the data contained in the Fig. 1 to Fig. 8 illustrated embodiments can be implemented without limiting the present disclosure to these embodiments.

[0049] How Fig. Figure 1 shows that 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 example two opposing, annular friction surfaces, and furthermore a mounting section 7 for attachment to the vehicle. The mounting section 7 is in this case cup-shaped and is radially surrounded by the friction section 6, but can also be designed differently than shown.

[0050] Both the friction section 6 and the fastening section 7 are formed on the base body 2 mentioned above, which is preferably made of grey cast iron, but can also be made of steel.

[0051] The friction section 6 has at least one friction surface 3a with a wear-resistant layer 3 applied by laser cladding. The wear-resistant layer 3 is preferably applied directly to the cast surface. No special preparation of the cast surface is required for this.

[0052] The friction section 6 can be designed in the form of a ring disk, on each of whose opposing ring surfaces there is a friction surface 3a.

[0053] As already explained, the wear protection layer 3 on the base body 2 extends beyond the friction surface 3a into an area 3b angled to the friction surface 3a, in order to end there, and is applied in the angled area 3b of the base body 2 in a covering and gap-free manner to the base body 2.

[0054] The angled area 3b forms an angle greater than 0°, preferably 15° to 95° and more preferably 30° to 90°, with the friction surface 3a.

[0055] The area 3b angled towards the friction surface 3a can be formed by the chamfers 4 already explained above (see above). Fig. 2, Fig. 3, Fig. 5 and Fig. 7) The angled area 3b can also include the circumferential sections 5 or 5a and 5b that are perpendicular to the friction surface 3a (see Fig. 3 and Fig. 5), which connect to the chamfers 4. If the chamfers 4 are omitted, the angled area 3b can be formed by the circumferential sections 5 or 5a and 5b perpendicular to the friction surface 3a (see figure). Fig. 4 and Fig. 6).

[0056] 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 not connected to each other.

[0057] At the friction surface 3a, a contact plane K exists between the wear-resistant layer 3 and the substrate on the base body. In all embodiments of the Fig. 1 to Fig. 8 The wear protection layer 3, which extends into the angled area 3b, seals the edge Ra, Rb of that contact plane K towards the environment. The contact point of the wear protection layer 3 exposed to the environment is thus spaced away from the contact plane K towards the side of the base body 2.

[0058] At the in Fig. In the embodiment shown in Figure 2, the friction surface 3a transitions via a chamfer 4 into a circumferential section 5 perpendicular to the friction surface 3a. The wear-resistant layer 3 extends continuously from the friction surface 3a into the chamfer 4 and terminates radially flush with the circumferential section 5.

[0059] The thickness of the wear-resistant layer 3 remains approximately constant, measured perpendicular to the respective substrate. However, the thickness of the wear-resistant layer can 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.

[0060] The thickness of the wear protection layer 3 on the friction surface 3a is 10 µm to 500 µm, preferably 50 µm to 200 µm.

[0061] Fig. Figure 3 shows, as a second embodiment, a modification of Fig. 2 with increased thickness of the wear protection layer 3. In addition, unlike Fig. 2 beyond the chamfer 4 into the area of ​​the circumferential section 5, thereby further increasing the path for through-corrosion to the contact plane K.

[0062] Fig. Figure 4 shows, as a third embodiment, a modification of Fig. 2 and Fig. 3, in which no chamfer 4 is provided at the edges of the friction surface 3a. In this case, the friction surface 3a transitions directly into the circumferential section 5 perpendicular to the friction surface 3a. The wear-resistant layer 3 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-resistant layer 3 in the angled area 3b. The thickness of the wear-resistant layer 3 remains approximately constant, being measured perpendicular to the respective substrate, and deviations in the range of 80 to 120% mentioned above are possible.

[0063] Fig. Figure 5 shows, as a fourth embodiment, a variation of the second embodiment according to Fig. 3. The wear-resistant layer 3 has an edge section in the angled area 3b where the layer thickness tapers towards the edge of the wear-resistant layer 3. The taper 9 only affects the area that covers the circumferential section 5, but as a modification, it can begin in the area of ​​the chamfer 4, but not in the area of ​​the friction surface 3a.

[0064] Fig. Figure 6 shows, as the fifth embodiment, a variation of the third embodiment according to Fig. 4. As in Fig. In section 5, the wear-resistant layer 3 has an edge section in the angled area 3b where the layer thickness tapers towards the edge of the wear-resistant layer 3. Due to the lack of chamfer 4, the taper 9 ends at the edge of the wear-resistant layer 3 at the circumferential section 5.

[0065] Fig. Figure 7 shows, as a sixth embodiment, a tapering 9 of the wear protection layer 3 in the area of ​​the chamfer 4.

[0066] Furthermore, it shows 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. An 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 to delay corrosion at the interface between the wear protection layer 3 and its substrate, thereby further increasing the service life of the brake disc 1.

[0067] Such an overlap by a corrosion protection layer 8 can also occur in the embodiments according to the Fig. 1 to Fig. 6 are planned. In the Fig. 2 to Fig. Figure 4 illustrates this by way of example for the outer edge of the brake disc 1, but it can optionally also be provided for the inner edge and any other edge areas. The overlap can be limited to selected edge areas of the wear protection layer 3 or it can cover the entire edge area of ​​the wear protection layer 3.

[0068] In the embodiments described above, the wear-resistant layer 3 is directly bonded to the material of the base body 2 by laser cladding. Here, the filler material for the wear-resistant layer 3 is melted into the material of the base body 2, since the latter is partially melted during laser cladding, and does not merely adhere to the surface like a weld bead, as is usually the case with thermal spatter processes. This ultimately enables a single-layer structure of the wear protection directly on the material of the base body 2 with sufficient bond strength.

[0069] However, it is also possible to provide a multi-layer structure for wear protection, as in Fig. Figure 8 shows, by way of example, that the wear-resistant layer 3 is applied to at least one intermediate layer 3' by laser cladding. The intermediate layer 3' is in turn metallurgically bonded to the material of the base body 2 by laser cladding. Such a multilayer structure can be implemented analogously in the [reference to the following]. Fig. 2 to Fig. The 7 illustrated embodiments are used.

[0070] The intermediate layer 3' is preferably made somewhat more ductile than the wear-resistant layer 3. For example, an iron-based alloy can be used for the intermediate layer 3'. The wear-resistant layer 3 additionally contains hard particles, in particular carbides, borides and / or nitrides.

[0071] Fig. Figure 9 shows a representation illustrating a process for manufacturing a brake disc 1 with a wear-resistant layer 3 as explained above.

[0072] 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 mounting section 7 for attachment to the vehicle. The friction section 6 and the mounting section 7 are preferably integral, i.e., formed in one piece.

[0073] The base body 2, possibly after the production of further functional surfaces, is placed in a laser cladding device, as shown in Fig. Figure 9 shows that the wear protection layer 3 is applied by laser cladding using a welding head 10, whereby the welding beam 11 of the welding head 10 is guided over the respective workpiece surface on the base body 2.

[0074] 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 these two movements produces a spiral weld bead whose adjacent turns overlap by approximately 70 to 95%.

[0075] Upon reaching an edge Ra, Rb of the friction surface 3a, the welding jet 11 of the welding head 10 is tilted, as shown in Fig. 9 is indicated by the reference numeral 10' to continue the welding in the area 3b of the brake disc 1 angled to the friction surface 3a beyond the friction surface 3a, such that the welding head 10 continues to be moved at a constant distance over the surface of the workpiece, namely over the angled area 3b.

[0076] The welding jet 11 can be oriented essentially perpendicular to the workpiece surface. A deviation of approximately + / - 45° from a strictly perpendicular orientation of the welding jet 11 is permissible without impairing the quality of the wear-resistant layer 3.

[0077] The welding process continues continuously beyond the friction surface 3a, and therefore does not need to be interrupted for the angled area 3b. The distance of the welding head 10 to the material surface remains constant throughout.

[0078] If angled areas 3b are to be traversed at both edges Ra, Rb of the friction surface 3a, welding preferably begins with one of the angled areas 3b and then continues to the other angled area 3b.

[0079] In laser cladding, the hard layer 3 is bonded to its substrate. The substrate material is partially melted using a laser beam, and simultaneously the material for the wear-resistant layer 3, preferably in powder form, is introduced.

[0080] 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 cladding. The wear-resistant layer 3 is then welded onto this or several such intermediate layers 3'.

[0081] The wear protection layer 3 is basically ready for use after the overlay welding, but may be subjected to a smoothing process if necessary.

[0082] Furthermore, in one embodiment of the process, after the application of the wear protection layer 3, a corrosion protection layer 8 can be applied to sections of the base body 2 not covered by the wear protection layer 3. In this case, less resistant and significantly less expensive coatings are typically used, which do not require welding.

[0083] 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 worn away within a few braking cycles, so that this area ultimately remains unaffected during operation of the brake disc or can be omitted during coating. However, the wear protection layer 3 in the angled area 3b can be overlapped by the corrosion protection layer 8, or remain overlapped, in order to delay corrosion at 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 the brake disc 1. The overlap can extend right 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.

[0084] The advantage of this approach is that no gap exists or can develop between the laser-deposited wear-resistant layer 3 and the base body 2. Instead, the wear-resistant layer 3 adheres completely and securely, even in the angled area 3b adjoining the friction surface 3a, particularly in the chamfers 4 and, if applicable, the circumferential sections 5. This reduces corrosion in areas of the brake disc 1 that are particularly relevant to its function and prevents delamination of the wear-resistant layer 3. An additional corrosion protection layer 8 can further delay corrosion towards the friction surface 3a.

[0085] The invention has been explained in more detail above with reference to exemplary embodiments and further modifications. In particular, individual technical features, which were explained above in the context of further individual features, can be implemented independently of these features and in combination with further individual features, even if this is not expressly described, as long as this is technically possible. The invention is therefore expressly not limited to the described exemplary embodiments and modifications, but encompasses all embodiments defined by the claims. Reference symbol list 1 brake disc 2 basic shapes 3 Wear protection layer 3' Intermediate shift 3a Friction surface 3b angled area 4th phase 5 Scope section 5a outer circumferential section 5b inner circumferential section 6 Friction section 7 Mounting section 8 Corrosion protection layer 9 Rejuvenation 10 welding heads 10' welding head, tilted 11 Welding beam A axis of rotation K Contact level Ra (radial) outer edge of the friction surface 3a Rb (radial) inner edge of the friction surface 3a QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2020 / 234144 A1 [0006, 0024, 0031] WO 2021 / 008744 A [0006, 0024, 0031]

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 fastening section (7) for vehicle-side fastening, wherein the friction section (6) and the fastening section (7) are formed on a base body (2) made of grey cast iron or steel and a wear-resistant layer (3) is welded onto the friction section (6) as a friction surface (3a) by laser cladding, characterized by , that the wear-resistant layer (3) on the base body (3) extends beyond the friction surface (3a) into an area (3b) angled to the friction surface (3a) and ends there and the wear protection layer (3) is applied in the angled area (3b) of the base body (2) in a covering manner and without gaps to the base body (2). [2] Brake disc (1) according to claim 1, characterized by, that a contact plane (K) exists on the friction surface (3a) between the wear protection layer (3) and the substrate on the base body, and that the wear protection layer (3) extending into the angled area (3b) seals the edge of that contact plane (K). [3] Brake disc (1) according to claim 1 or 2, characterized by , 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), 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-resistant layer (3) continues uninterrupted from the friction surface (3a) into the chamfer (4) or into the circumferential section (5, 5a, 5b). [4] Brake disc (1) according to one of claims 1 to 3, characterized by, that the thickness of the wear protection layer (3) in the angled area is 80 to 120% of the layer thickness at the friction surface (3a), in each case measured perpendicular to the respective substrate. [5] Brake disc (1) according to one of claims 1 to 4, characterized by , that the wear protection layer (3) has an edge section in the angled area (3b), wherein the edge section tapers in thickness (9) towards the edge of the wear protection layer (3). [6] Brake disc (1) according to any one of claims 1 to 5, characterized by , 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 one of claims 1 to 6, characterized by, that the wear protection layer (3) is directly bonded to the material of the base body (2), or that the wear protection layer (3) is applied to an intermediate layer (3') which in turn is bonded to the material of the base body (2) by laser cladding. [8] Method for manufacturing a brake disc (1) for a friction brake of a motor vehicle, comprising: - Providing a base body (2) made of grey cast iron or steel, which extends over a friction section (6) with at least one friction surface (3a) and a fastening section (7) for vehicle-side attachment, - Application of a wear-resistant 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 by, that when an edge (Ra, Rb) of the friction surface (3a) is reached, the laser welding is continued into an area (3b) of the brake disc (1) angled to the friction surface (3a) beyond the friction surface (3a), whereby the distance of the welding head (10) to the respective surface is kept constant. [9] Method according to claim 8, characterized by , that during welding 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 when the edge (Ra, Rb) of the friction surface (3a) is reached the welding head (10) is tilted. [10] Method according to claim 8 or 9, characterized by, 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) is overlapped by the corrosion protection layer (8) in the angled area (3b).

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