LEAD-FREE ALUMINIUM SLIDING BEARING MATERIAL HAVING A FUNCTIONAL SURFACE

Abstract

The invention relates to a sliding element having a coating, which comprises at least one functional layer, said functional layer having a mixed oxide-matrix and in the mixed-oxide matrix and solid lubricant particles and/or hard particles are embedded in the mixed oxide-matrix.

Claims

1. A sliding element with 3 coating comprising at least one functional layer, characterised in that the functional layer comprises a mixed oxide matrix, and solid lubricant particles and/or hard particles are embedded in the mixed oxide matrix.

2. The sliding element according to claim 1, characterised in that the coating comprises at least the following layers from the inside to the outside: an aluminum alloy layer consisting of an aluminium-based alloy, and the functional layer.

3. The sliding element according to claim 1 or 2, characterised in that the aluminium-based alloy consists of up to 10.0 wt % Fe, up to 10.0 wt % Mg, up to 15.0 wt % Zn, up to 15.0 wt % Si, up to 30.0 wt % Sn, up to 5.0 wt % Cu, up to 5.0 wt % Ni, up to 5.0 wt % Mn, up to 5.0 wt % Cr, up to 1.0 wt % Zr, V, Sr and/or Ti and the remainder is aluminium and unavoidable impurities.

4. The sliding element according to one of the preceding claims, characterised in that the functional layer is applied onto the aluminium alloy layer which is in turn bonded to a substrate backing, and the substrate backing consists of steel, preferably one of the steel grades C06-C45.

5. The sliding element according to claim 4, characterised in that an intermediate layer preferably consisting of pure aluminium is provided between the substrate backing and the coating.

6. The sliding element according to one of the preceding claims, characterised in that the solid lubricant particles comprise BaSO.sub.4, h-BN, graphite, MoS.sub.2, PTFE, WS.sub.2, ZnS and/or SnS.sub.2.

7. The sliding element according to one of the preceding claims, characterised in that the hard particles comprise oxides, nitrides, phosphides, phosphates, fluorides, WC, TiC, TaC, CrC, B.sub.4C, CaC.sub.2 and/or Al.sub.4C.sub.3.

8. The sliding element according to one of the preceding claims, characterised in that organically modified particles, particles with sinter additives such as preferably N.sub.3HCO.sub.3, core-shell particles, nanocapsules which are preferably filled with solid lubricant, and/or particles embedded in a polymeric sol are embedded in the mixed oxide matrix.

9. The sliding element according to one of the preceding claims, characterised in that the coating has a hardness of 10 to 1500 HV0.1, preferably 10-500 HV0.1.

10. The sliding element according to one of the preceding claims, characterised in that the functional layer has a thickness of 10 nm to 100 m.

11. The sliding element according to one of claims 2 to 10, characterised in that the aluminium alloy layer has a thickness of up to 200 m.

12. The sliding element according to one of the preceding claims, characterised in that the embedded particles have an average diameter of 1 nm to 15 m.

13. The sliding element according to one of the preceding claims, characterised in that the functional layer has a thermal conductivity of 5 to 100 W/m*k, preferably 20 to 40 W/m*k.

14. The sliding element according to one of the preceding ciaims, characterised in that the distribution of the solid lubricant particles and/or hard particles in the mixed oxide matrix has a gradient from the inside to the outside.

15. The sliding element according to one of the preceding claims, characterised in that the coating has on its outside a cover layer which is preferably applied electrolytically.

Description

DETAILED DESCRIPTION

[0028] According to a preferred embodiment, there is provided a sliding bearing with a coating on a C06 steel substrate backing. The following layer structure is particularly preferred: a so-called aluminium alloy layer with the elements mentioned in claim 3 is located on the steel backing. The functional layer is then produced by chemical-physical processes (anodisation) and can in turn contain solid lubricant particles and/or hard particles. In this case, an aluminium alloy is first cast by means of strip casting and then roiled down to a thickness of maximum 1.5 mm by the subsequent rolling steps. When an intermediate film is used for improving the adhesion, the strip and the film are then joined to form a strand by means of roll-cladding. Subsequently, the strand is ground and applied onto the C06 steel by roll-cladding. The sliding bearing material subsequently obtains bearing shell dimensions by means of conventional shaping steps. The mixed oxide matrix is subsequently produced galvanostatically or potentiostatically by electrolytic oxidation of the aluminium alloy layer using direct current, alternating current or pulsed current sources. The methodology required for this purpose is known to the skilled person from the prior art, for example from the final Report of the IGF Project 321 ZBG (Optimierung der Modifizierung von Anodisierschichten auf Aluminiumwerkstoffen durch chemische Nanotechnologie und industrielle Anpassung des Verfahrens; Frbeth et al.; chapter 2.5). At the same time, B.sub.4C particles are deposited in parallel by means of electrophoretic deposition and are thereby embedded in the mixed oxide matrix. To ensure homogeneous particle distribution, an agglomeration of the particles is ensured by using stabilised dispersions, finally, the sliding bearing surfaces are aftertreated.