Brake Disc Provided with Protection from Wear and Corrosion and Method for Production Thereof

Abstract

The present invention concerns the field of vehicle technology and industrial-plant technology and relates to a brake disc provided with protection from wear and corrosion and to a method for production thereof. The known solutions have the disadvantage that the coating for providing protection from corrosion and wear is applied to the frictional surfaces of the brake disc and is rubbed off straight away during the first braking operations. The present invention addresses the problem of providing a brake disc that has improved and durable protection from corrosion and wear. The significantly improved properties of the brake disc in terms of protection from corrosion and wear are achieved according to the invention by at least the region of the frictional surfaces (2) having an AlSi-based diffusion layer (3), which has a layer thickness of 0.1 mm to 0.6 mm and is formed in the process of interaction with the steel or grey cast iron of the metal main body (1). The brake disc according to the invention can be used for example in vehicles or as a braking system for industrial brakes or in wind turbines.

Claims

1. A brake disk having a main metallic body (1) made of steel or gray iron, having at least one region with formed friction surfaces (2) and at least one region with a formed contact surface (6) for securing of the brake disk, wherein a diffusion layer (3) formed from iron, aluminum and silicon present within the main metallic body (1) at least in the region of the friction surfaces (2) has a layer thickness of 0.1 mm to 0.6 mm and is formed collectively with the steel or gray iron of the main metallic body (1) via diffusion processes.

2. The brake disk as claimed in claim 1, in which ventilation ducts are additionally present.

3. The brake disk as claimed in claim 1, in which the diffusion layer (3) takes the form of a gradated layer system composed of iron and aluminum in the layer thickness, wherein silicon is distributed homogeneously in the gradated layer system.

4. The brake disk as claimed in claim 3, in which the gradated layer system is formed in such a way that the proportion of iron decreases continuously toward the layer surface and the proportion of aluminum increases continuously toward the layer surface, with silicon distributed homogeneously in the gradated layer system.

5. The brake disk as claimed in claim 1, in which the at least one diffusion layer (3) is formed by coating the main metallic body (1) with an AlSi.sub.12 and/or AlSi.sub.6 alloy, followed by thermal treatment.

6. The brake disk as claimed in claim 1, in which the region of the contact surface (6) and/or the ventilation ducts (4) additionally has the diffusion layer (3).

7. The brake disk as claimed in claim 1, in which the diffusion layer (3) has a greater hardness compared to the hardness of the material of the main metallic body (1).

8. The brake disk as claimed in claim 1, in which the diffusion layer (3) is formed by means of a thermal treatment at 250° C. to 650° C. and a treatment duration of 40 to 300 minutes.

9. The brake disk as claimed in claim 1, in which the ventilation ducts (4) have the diffusion layer (3) and an Al-based surface layer having a layer thickness of 0.01 mm-0.4 mm.

10. The brake disk as claimed in claim 1, in which coloring substances are present at least within the diffusion layer (3).

11. A process for producing the brake disk as claimed in claim 1, in which the surface of the main metallic body (1) is mechanically processed at least in the region of the formed friction surfaces (2), then an AlSi-based alloy is disposed at least in the region of the formed friction surfaces (2) by means of a coating process, then a thermal treatment of the brake disk is conducted under protective gas atmosphere, and finally the surface of the main metallic body (1) is mechanically processed at least in the region of the friction surfaces (2).

12. The process as claimed in claim 11, in which the contact surface (6) and/or the ventilation ducts (4) are additionally coated with an AlSi-based alloy.

13. The process as claimed in claim 11, in which the coating is implemented with an AlSi.sub.12 or AlSi.sub.6 alloy.

14. The process as claimed in claim 11, in which the mechanical treatment and/or the coating method is conducted under a protective gas atmosphere.

15. The process as claimed in claim 11, in which the thermal treatment of the brake disk is conducted for a treatment duration of 40 to 300 minutes and at a temperature of 250° C. to 650° C., particularly advantageously at a temperature of 550° C. to 600° C.

16. The process as claimed in claim 11, in which the brake disk is preheated prior to the coating to a temperature of 250° C. to 650° C. under a protective gas atmosphere.

17. The process as claimed in claim 11, in which the brake disk is preheated prior to the coating to a temperature of 150° C. to 200° C. without a protective gas atmosphere.

18. The process as claimed in claim 11, in which the coating is implemented by means of arc wire spraying, modified arc wire spraying with increased kinetic energy of the splat, high-velocity wire flame spraying, liquid aluminum dipping, paint dipping, paint spraying, laser powder buildup welding, powder spraying or electrocoating.

19. The process as claimed in claim 18, in which coating with a paint is followed by implementation of a first inductive heating of the brake disk to a temperature of 250° C. to 650° C. over a period of 5 to 240 seconds.

20. The process as claimed in claim 11, in which coloring substances are fed in before or during the coating, and these are used to create color markings within the diffusion layer (3) at least in the region of the friction surfaces (2).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The invention is to be elucidated in detail hereinafter by a working example. The figures show:

[0074] FIG. 1—schematic view of a cross section through a brake disk and

[0075] FIG. 2—schematic partial view of the brake disk with diffusion layer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0076] An internally ventilated brake disk for a vehicle, made from gray iron, is provided, having a hardness of 220 HV. The brake disk has two friction surfaces 2 arranged diametrically opposite one another, and a contact surface 6 for the securing of the brake disk to an axle. The two friction surfaces 2 are connected by ventilation ducts 4 in the form of lands. By means of corundum (99.81% Al.sub.2O.sub.3, 0.1% Na.sub.2O, 0.04% TiO.sub.2, 0.02% SiO.sub.2, 0.03% Fe.sub.2O.sub.3) and using a protective nitrogen gas atmosphere, the surface of the two friction surfaces 2 is mechanically processed twice in and opposite the direction of rotation of the brake disk at an angle of 45°, and hence soiling and iron oxides are removed, in order to provide improved diffusion conditions for subsequent formation of the diffusion layer. In addition, the lamellar structure of the gray iron is modified and eliminated in the near-surface region.

[0077] Subsequently, the brake disk is sent to a coating plant and coated under a protective nitrogen gas atmosphere by means of arc wire spraying with an AlSi.sub.12 alloy having a layer thickness of 0.4 mm in the region of the friction surfaces 2, the contact surface 6 and the ventilation ducts 4. After the coating, a thermal treatment of the entire brake disk is undertaken in an oven under a protective argon gas atmosphere. The thermal treatment is conducted at 580° C. for 240 minutes, and then the brake disk is cooled. The thermal treatment formed a diffusion layer 3 of iron aluminides having a layer thickness of 170 μm to 200 μm, and an Al-based surface layer having a layer thickness of about 50 μm.

[0078] The excess Al-based surface layer is then mechanically processed by means of grinding in the region of the friction surfaces 2 and the contact surface 6 and removed down to the diffusion layer 3, such that exclusively the diffusion layer 3 composed of grown iron aluminides remains in the region of the friction surfaces 2 and the contact surface 6. Silicon is distributed homogeneously in the diffusion layer. There is no mechanical processing of the surfaces in the region of the ventilation ducts 4.

[0079] The friction surfaces 2, contact surface 6 and the ventilation ducts 4 have a hardness of 350 HV and have long-term protection from wear and corrosion.

LIST OF REFERENCE NUMERALS

[0080] 1—main metallic body [0081] 2—friction surface [0082] 3—diffusion layer [0083] 4—ventilation ducts [0084] 5—rotating axle [0085] 6—contact surface