Method for producing a coated surface of a tribological system

Abstract

A method is proposed for producing a cylinder working surface of an internal combustion engine that is optimized in terms of friction and wear.

Claims

1. A method for producing a wear-resistant surface on or within a workpiece that is made of aluminum or an aluminum alloy, the method comprising the steps of: a) premachining and thereby activating a surface of the workpiece by honing or precision boring the workpiece to produce an activated surface having a surface roughness Rz value ranging from 1 to 4 microns; and b) applying a wear-resistant coating onto the activated surface of the workpiece by means of electrolysis, said electrolysis by one of plasma electrolytic deposition (PED) or plasma electrolytic oxidation (PEO), to produce a wear-resistant coating having a surface roughness Rz ranging from 2 to 3 microns, a Rpk value ranging from 1.0 to 2.0 microns and pores, with said pores having a size ranging from 2 to 3 microns in the surface.

2. The method according to claim 1, wherein after the wear-resistant coating has been applied, the surface of the wear-resistant coating is smoothed, and wherein the porosity of the wear-resistant coating surface is retained after the wear-resistant coating surface has been smoothed and wherein the pores retain oil applied to the surface of the wear-resistant coating.

3. The method according to claim 2, wherein the surface of the wear-resistant coating is smoothed by honing the surface.

4. The method according to claim 3, wherein during the honing of the surface of the wear-resistant coating a layer of less than 5 m of thickness of the surface is removed during the honing process.

5. The method according to claim 2, wherein the wear-resistant coating is smoothed using a smooth-honing tool having freely suspended honing segments.

6. The method according to claim 2, wherein the step of smoothing the surface produces a surface having a surface roughness, Rz, ranging from 2.0 to 2.5 microns.

7. The method according to claim 1, wherein the activated surface of the workpiece is subjected to an alkaline degreasing step prior to application of the wear-resistant coating onto the activated surface.

8. The method according to claim 1, wherein a cylindrical surface is produced in the workpiece during the premachining step.

9. The method according to claim 1, wherein the workpiece is made of a hypoeutectic aluminum alloy.

10. The method according to claim 1, wherein the premachining of the workpiece is used to produce a cylinder bore of an internal combustion engine in the workpiece and wherein the cylinder bore is coated with the wear-resistant coating.

11. The method according to claim 1, wherein the electrolysis step produces a wear-resistant coating comprising aluminum oxide.

Description

(1) In the drawings:

(2) FIG. 1 shows the bore surface line after pre-treatment by precision boring or honing;

(3) FIG. 2 shows the bore surface line with a layer applied;

(4) FIG. 2.1 shows the undulations in the layer;

(5) FIG. 2.2 is a highly enlarged reproduction of the surface of the layer before smoothing;

(6) FIG. 3 shows the bore surface line with a layer applied after smoothing;

(7) FIG. 3.1 shows the undulations in the layer after smoothing;

(8) FIG. 3.2 is s highly enlarged reproduction of the surface of the layer after smoothing; and

(9) FIG. 4 is a schematic view of a honing tool for smoothing.

(10) FIG. 1 shows the surface line 2 of a (cylinder) bore premachined by honing. In this state, the substrate is activated for the subsequent coating and has the desired target shape.

(11) FIG. 2 shows the surface after treatment by means of PED. From this figure, it is clear that approximately one third (reference sign 4) of the thickness of the coating 9 makes up a change in the rim zone of the substrate and approximately two thirds (reference sign 3) of said thickness produce a layer structure on the outside.

(12) It should be noted the premachining dimensions of the bore (see the surface line 2) are such that the surface line 5 of the coating 9 is within the tolerance range of the finished bore.

(13) FIG. 2.1 shows the undulations in the surface line 5 according to FIG. 2. The undulations are too great for many uses, and therefore a smoothing process also needs to be carried out in order to reduce the undulations.

(14) FIG. 2.2 shows an SEM picture of the surface after coating. In this picture, the pores 8 of the coating are apparent.

(15) FIG. 3 shows the smoothed surface line 6, which has for example been achieved by honing using the tool shown in FIG. 4. In this figure, the surface line has been smoothed such that a straight surface line 6 has been produced while retaining the pores 3. After smoothing, the smoothed surface line 8 is also within the tolerance range of the finished bore.

(16) The surface of the smoothed surface line is also shown in FIG. 3.1 in the scanned section and in the SEM picture in FIG. 3.2.

(17) FIG. 4 shows the principle of smooth-honing using a spring-mounted honing stone 7, at the start of the smooth-honing process. The radial action on the coating is produced by the radial force FR. Owing to the springs, the honing stone 7 has the option of reducing the shallow undulations in the coating without changing the target shape of the cylinder bore. During smoothing, the pore structures are largely retained.