FRICTION BRAKE BODY FOR A FRICTION BRAKE OF A MOTOR VEHICLE, FRICTION BRAKE AND METHOD FOR PRODUCING A FRICTION BRAKE BODY

Description

[0001] The invention relates to a friction brake body for a friction brake of a motor vehicle, in particular a brake disc, with a base body made in particular of grey cast iron, with a wear protection layer applied to the base body and with an intermediate layer lying between the wear protection layer and the base body.

[0002] Furthermore, the invention relates to a friction brake for a motor vehicle, having at least one brake disc and at least one brake pad assigned to the brake disc and displaceable, as well as a method for producing the friction brake body described above. State of the art

[0003] Friction brakes for motor vehicles usually have a brake disc and at least one brake block with a brake lining as the friction brake body, with the brake block being pressed against the brake disc to achieve a braking effect. The brake disc is usually connected to a wheel of the motor vehicle in a rotationally fixed manner, and the brake block is arranged so that it can be displaced fixedly to the body. If the brake block is pressed against the brake disc, the frictional contact between the brake block and the brake disc causes abrasion on the brake disc, which leads to wear of the brake disc and to brake dust that is released into the environment. In order to reduce this wear, it is known to provide the friction brake body with a wear protection layer, at least in the contact area with the brake block. For example, it is known to apply wear protection layers based on hard metals or carbides to a base body of the friction brake body made of gray cast iron.In addition, it is known to provide an intermediate layer between the wear protection layer and the base body, which serves in particular as an adhesion promoter and corrosion protection layer between the wear protection layer and the base body.

[0004] German Patent Application DE 10 2009 008 114 A1 discloses a brake disc and a method for its production, comprising a base body made of gray cast iron and at least one wear-resistant layer applied to the base body, with an intermediate layer arranged between the wear-resistant layer and the base body. A brake disc of this type is further disclosed in German Patent Application EP 3 034 902 A1. Disclosure of the invention

[0005] The friction brake body according to the invention with the features of claim 1 has the advantage of improving the adhesion of the wear-resistant layer to the intermediate layer, as well as the crack resistance and corrosion resistance of the friction brake body. For this purpose, the intermediate layer according to the invention is a metallic intermediate layer and is applied to the base body by laser deposition welding.

[0006] In particular, the metallic intermediate layer is a nickel-, cobalt-, or iron-based alloy. The low porosity achievable through laser cladding and the resulting high crack resistance of this intermediate layer prevent crack propagation and corrosion in the layer system of the friction brake body. Laser cladding also ensures high layer adhesion between the intermediate layer and the base body due to the material bond, on the one hand, and between the wear-resistant layer and the intermediate layer due to the preferably high surface roughness of the intermediate layer applied by laser cladding and the resulting high bond strength, on the other.

[0007] Particularly preferably, the surface of the intermediate layer facing the wear-resistant layer is thermally pretreated, resulting in even better adhesion of the wear-resistant layer to the intermediate layer. In particular, the pretreatment cleans the surface of the intermediate layer, for example, by means of laser beam treatment.

[0008] According to a preferred embodiment of the invention, the metallic intermediate layer has at least a two-phase structure. The different phases increase the fracture toughness of the intermediate layer because the different phase formations inhibit crack propagation during the transition from one phase to the adjacent phase.

[0009] Preferably, the respective phase makes up at least 5 vol.% of the intermediate layer. This results in a favorable microstructure that increases fracture toughness.

[0010] Furthermore, it is preferably provided that the wear-resistant layer is a wear-resistant layer applied to the intermediate layer by thermal spraying or laser deposition welding. Thus, the wear-resistant layer is also preferably applied to the intermediate layer by laser deposition welding, resulting in a cost-effective manufacturing process for the layer system.

[0011] According to the invention, the wear-resistant layer is formed as an iron-based alloy with embedded hard material particles consisting of carbides, oxides, nitrides, or borides. These additives strengthen the iron-based alloy and make it abrasion-resistant. According to the invention, the thickness of the intermediate layer corresponds to at least twice the average particle size of the hard material particles embedded in the wear-resistant layer. This ensures effective corrosion protection through a closed, sealed intermediate layer, even if a hard material particle is inadvertently incorporated into the intermediate layer during production.

[0012] The friction brake according to the invention with the features of claim 7 is characterized by the design of the brake disc as a friction brake body according to the invention. This results in the advantages already mentioned.

[0013] The method according to the invention with the features of claim 8 is characterized in that the metallic intermediate layer is applied to the base body by laser deposition welding. This results in the aforementioned advantages.

[0014] Further advantages and preferred embodiments emerge in particular from the claims and from the above description.

[0015] In particular, the base body is made of gray cast iron. Preferably, the metallic intermediate layer is applied first, followed by the wear-resistant layer. Preferably, the base body is mechanically or thermally pretreated prior to the application of the intermediate layer, in particular to meet geometric requirements. Preferably, the intermediate layer is also thermally pretreated, in particular cleaned, for example by laser beam treatment, prior to the application of the wear-resistant layer in order to ensure good adhesion between the wear-resistant layer and the intermediate layer. In particular, a nickel-, cobalt-, or iron-based alloy is applied to the base body as the intermediate layer. The intermediate layer is preferably produced in such a way that it has at least a two-phase structure in order to increase fracture toughness.Preferably, the intermediate layer is produced in such a way that the respective phase constitutes at least 5 vol.% of the intermediate layer. The wear-resistant layer is preferably applied to the intermediate layer by laser deposition welding or thermal spraying, particularly as an iron-based alloy and particularly with embedded hard material particles, preferably consisting of carbides, oxides, nitrides, or borides.

[0016] The invention will be explained in more detail below with reference to the drawings. Figure 1 shows an advantageous friction brake body in a simplified perspective view, Figure 2 shows a simplified representation of a manufacturing method of the friction brake body and Figure 3 shows a flow chart to explain the manufacturing method.

[0017] Figure 1shows a simplified perspective view of a friction brake body 1 designed as a brake disc 2 for a friction brake of a motor vehicle (not shown in detail here). The friction brake body 1 has a circular base body 3 made of gray cast iron. An optionally available brake disc chamber of the brake disc 2 is shown in Figure 1not shown. On each of its two end faces, the base body 3 has an annular frictional contact surface 4 formed by a wear-protection layer 5 of the friction brake body 1. When used as intended, the wear-protection layer 5 forms a frictional contact partner for at least one brake pad or brake lining of the friction brake, which is pressed against the frictional contact surface 4 to achieve frictional braking. The brake disc 2 is usually connected to a wheel of the motor vehicle in a rotationally fixed manner, while the brake pad is fixed to the housing and can only be displaced in the direction of the brake disc 2. Due to the relative movement between the brake disc 2 and the brake pad, when the brake pad is pressed against the frictional contact surface 4, abrasion occurs on the friction brake body 1, which leads to wear of the friction brake body 1, as well as to brake dust that enters the environment of the motor vehicle.

[0018] The wear protection layer 5 reduces this wear and increases the abrasion resistance of the friction brake body 1. According to the invention, the wear protection layer is designed as an iron-based alloy which has embedded hard material particles consisting of carbides, oxides, nitrides or borides in order to ensure the above-mentioned advantages.

[0019] To ensure secure adhesion of the wear-resistant layer 5 to the base body 3, a metallic intermediate layer 6 is formed between the wear-resistant layer 5 and the base body 3. The intermediate layer 6 is applied to the base body 3 by laser deposition welding.

[0020] This shows Figure 2A simplified sectional view of the process of laser cladding. In this process, a surface layer 7 of the base body 3 is heated by a laser beam 8 such that the surface layer 7 melts. At the same time, an additive 9 for producing the metallic intermediate layer, a nickel-, cobalt-, or iron-based alloy, is melted by the laser beam and subsequently mixed with the molten surface layer 7, creating, in particular, a weld bead 10, which forms the intermediate layer 6.

[0021] The wear protection layer 5 is applied to the intermediate layer 6 thus produced, in particular also by means of laser deposition welding.

[0022] Preferably, the metallic intermediate layer 6 is applied to the base body 3 in such a way that it has at least a two-phase structure. In particular, the phases each make up at least 5 vol.% of the intermediate layer to ensure advantageous crack resistance or fracture toughness of the intermediate layer. The presence of different phases ensures that a developing crack is stopped or inhibited at the transition from one phase to the adjacent one, thus advantageously preventing crack propagation through the intermediate layer 6.

[0023] Figure 3shows, using a flow chart, an advantageous method for producing the friction brake body 1. In a first step S1, the base body 3 is provided. Preferably, the base body is made of gray cast iron, as already mentioned. In a subsequent step S2, at least one end surface of the base body 3 is mechanically or thermally pre-machined or pre-treated, in particular to roughen or geometrically adapt the surface to which the metallic intermediate layer 6 is to be applied. Subsequently, in a step S3, the metallic intermediate layer 6 is applied to the end surface of the base body 3 by laser deposition welding. In particular, the intermediate layer is a nickel-, cobalt-, or iron-based alloy.The material bonding resulting from laser deposition welding ensures advantageous adhesion of the intermediate layer 6 to the base body 3. Subsequently, after the intermediate layer 6 has solidified or cooled sufficiently, the intermediate layer 6 is optionally thermally pretreated on its free surface in a step S4, for example by laser beam treatment. Subsequently, the wear-resistant layer 5 is applied to the intermediate layer 6 in a step S5, in particular by laser deposition welding or thermal spraying. As already mentioned, the wear-resistant layer 5 is formed in particular as an iron-based alloy containing carbides, oxides, nitrides, or borides to increase wear resistance.

[0024] The finished friction brake body 1 is then obtained in a step S6. Optionally, the wear-resistant layer 5 is mechanically or thermally reworked, in particular ground, to ensure a desired surface roughness for interaction with the brake pad of the friction brake.

Claims

1. Friction brake body (1) for a friction brake of a motor vehicle, in particular a brake disk (2), with a base body (3) made in particular of grey cast iron, with at least one wear protection layer (5) applied onto the base body (3) and at least one intermediate layer (6) located between the wear protection layer (5) and the base body (3), wherein the wear protection layer (5) is formed as an iron-based alloy with embedded hard material particles consisting of carbides, oxides, nitrides or borides, wherein the intermediate layer (6) is a metallic intermediate layer (6) applied by laser deposition welding, wherein the layer thickness of the intermediate layer (6) corresponds to at least twice the mean particle size of the hard material particles incorporated in the wear protection layer (5).

2. Friction brake body according to claim 1, characterized in that the intermediate layer (6) is a nickel-, cobalt- or iron-based alloy.

3. Friction brake body according to one of the preceding claims, characterized in that the intermediate layer (6) has an at least two-phase structure.

4. Friction brake body according to claim 3, characterized in that the respective phase makes up at least 5% by volume of the intermediate layer (6).

5. Friction brake body according to one of the preceding claims, characterized in that the wear protection layer (5) is a wear protection layer (5) applied onto the intermediate layer (6) by thermal spraying or laser deposition welding.

6. Friction brake body according to one of the preceding claims, characterized in that the surface of the intermediate layer (6) facing the wear protection layer (5) is thermally pre-treated.

7. Friction brake for a motor vehicle, with at least one brake disk (2) and at least one displaceable brake pad associated with the brake disk (2), characterized by the design of the brake disk (2) as a friction brake body (1) according to one of claims 1 to 6.

8. Method for producing a friction brake body (1) for a friction brake of a motor vehicle, wherein a base body (3), which is made of in particular grey cast iron, is provided with at least one wear protection layer (5) and at least one metallic intermediate layer (6) situated between the wear protection layer (5) and the base body (3), wherein the wear protection layer (5) is produced as an iron-based alloy with embedded hard material particles consisting of carbides, oxides, nitrides or borides, wherein the intermediate layer (6) is applied onto the base body (3) by laser deposition welding, wherein the intermediate layer (6) is applied onto the base body (3) in such a way that the layer thickness of the intermediate layer (6) corresponds to at least twice the mean particle size of the hard material particles incorporated in the wear protection layer (5).

9. Method according to claim 8, characterized in that the intermediate layer (6) is applied onto the base body (3) in such a way that it has an at least two-phase structure.