Method for Producing a Coat on a Piston Ring and Piston Ring

Abstract

The invention relates to a method for producing a coat on the outer peripheral surface of a piston ring base. According to said method, a plurality of layers is applied layer by layer to the peripheral surface by applying, using a PVD method, at least one metal adhesive layer based on Cr to the peripheral surface without adding nitrogen to the process gas. Nitrogen is added to the process gas while increasing the partial pressure of the nitrogen, thereby forming a CrN gradient layer on the adhesive layer, and finally at least one cover layer having a constant composition based on CrN, Cr2N or a mixture of the two phases is applied to said gradient layer.

Description

The invention object is represented by an example diagram, and is described as follows. The diagram shows:

FIG. 1 Cross-section of a piston ring basic body with the operating surface layers depicted

FIG. 2 Concentration profile of Cr-N in the operating surface layers presented in FIG. 1

FIG. 1 shows the cross-section of a piston ring 1, containing a basic body 2, which has an external surface comprising the operating surface layer 3. On the external surface 3 in this example there are three layers 4, 5 and 6 laid out according to the PVD procedure. In this example layer 4 is depicted by the layer Cr, and having a layer thickness of 0.5 μ.

In the PVD procedure a CrN gradient layer 5 with a thickness of 3 μ is laid onto the layer 4. The layer composition within the CrN gradient layer 5 could be varied in such a way through the Nitrogen input as a process gas, that isolations of Cr over Cr—Cr₂N-mixture, Cr₂N, Cr₂—CrN-mixture through to CrN were available.

In the PVD procedure a cover layer 6 of consistent composition having a layer thickness of 30 μ was put on over the CrN gradient layer 5, where this layer was CrN. Cr₂N or a mixture of both phases is also an option.

In one test attempt a CrN layer having an overall thickness of 30 μ was isolated onto a piston ring 1. In one case a CR layer of 0.5 μ thickness was overlaid, in another case also a Cr layer of the same thickness and with an additional 3 μ gradient layer was overlaid. The variants having the gradient layer exhibited only as much self-tension pressure as did the layers without a gradient layer.

FIG. 2 depicts the concentration profile of the layering described in FIG. 1. The Cr and N content is indicated in Atom % as well as the layer thickness in μ. In the layering process a metallic Cr layer is first applied without Nitrogen as a process gas, ( layer 4). According to this invention the self tension levels in the Cr—N system are reduced at higher layer thicknesses, when the Nitrogen input as process gas is introduced at partial pressure with a continual increase in this example. The layer composition in the CrN gradient layer 5 is thereby varied from Cr to Cr—Cr₂N mixture, Cr₂N, Cr₂N—CrN mixture, on to CrN. After this a cover layer 6 of a constant composition is isolated, where this is CrN

Claims

1. Procedure to produce a layering on the outer surface area (3) of the piston ring body (2), in which multiple layers (4, 5, 6) are applied onto the surface area (3), so that in the PVD process at least one metallic adhesive layer (4) is applied to the surface area (3) on the basis of Cr without the introduction of Nitrogen as a process gas, after which process gas is introduced under increasing the Nitrogen partial pressure to form a CrN-gradient layer onto the adhesive layer (4), and finally at least one cover layer (6) of a constant composition on the basis of CrN, Cr2N or a mixture of both phases is applied to the gradient layering (5)

2. Procedure according to claim 1 wherein the increasing of the Nitrogen partial pressure occurs in a type of ramping function.

3. Procedure according to claim 1 wherein the increasing of the Nitrogen partial pressure occurs continuously.

4. Procedure according to claim 1 wherein the layer composition within the CrN gradient layers (5) from Cr to Cr—Cr2N mixture, Cr2N, Cr2N—CrN mixture, on to CrN.

5. Procedure according to claim 1 the wherein the adhesive layer (4) is produced with a layer thickness from 0.1 μ to 1 μ.

6. Procedure according to claim 1 wherein the CrN gradient layer (5) is produced with a layer thickness from 1 μ to 8 μ.

7. Procedure according to claim 6 the cover layer (6) is produced with a layer thickness from 10 μ to 80 μ.

8. Procedure according to claim 1 having an overall layer thickness between 30 μ and 50 μ for a CrN gradient layer (5) with a layer thickness between 2 and 6 μ and a layer (4) with a layer thickness <0/6 μ.

9. Piston ring comprising of basic body (2), onto the exterior surface area (3) of which multiple layers (4, 5, 6) are applied over one another, so that the exterior surface area (3) faced by the adhesive layer (4) is a PVD adhesive layer on the basis of Cr, on the adhesive layer (4) is a CrN-gradient layer (5) with a layer composition of Cr over Cr—Cr2N-mixture, Cr2N, Cr2N—CrN-mixture on to CrN, and on the CrN gradient layer (5) at least one cover layer (6) of constant composition on the basis of CrN, Cr2N or a mixture of both phases.

10. Piston ring according to claim 9 wherein the adhesive layer (4) exhibits a layer thickness from 0.1 μ to 1 μ.

11. Piston ring according to claim 9 wherein the CrN gradient layer (5) exhibits a layer thickness from 1 μ to 8 μ.

12. Piston ring according to claim 11 wherein the cover layer (6) exhibits a layer thickness from 10 μ to 80 μ.

13. Piston ring according to claim 9 wherein the overall layer thickness is between 30 μ and 50 μ, the adhesive layer (4) has a layer thickness <0.6 μ, and that the CrN gradient layer (5) thickness lies between 2 μ and 6 μ.