Wear and/or friction reduction by using molybdenum nitride based coatings

Abstract

The present invention relates to a component comprising a surface coated with a coating comprising a MoxCryN layer, where x and y correspond to the coefficients of Mo content and Cr content in atomic percentage, respectively, when only Mp and Cr are considered, and so x+y is considered to be 100 at %.

Claims

1. A component comprising: a surface coated with a coating comprising a MoxCryN layer, where x and y correspond to the coefficients of Mo (molybdenum) content and Cr (chromium) content in atomic percentage (at%), respectively, when only Mo and Cr are considered, and so x_+_y=100 at%, wherein the MoxCryN layer is a monolayer, wherein the surface of the component which is coated has a hardness equal or lower than 65 HRC, wherein the Cr content in the MoxCryN layer is varied along the thickness of the MoxCryN layer.

2. The component of claim 1, wherein 5 at %<y<50 at %.

3. The component of claim 1, wherein 20 at %<y<40 at %.

4. The component of claim 1, wherein the coating comprises a CrN layer deposited between the surface of the component and the MoxCryN layer.

5. The component of claim 2, wherein the coating comprises a CrN layer deposited between the surface of the component and the MoxCryN layer.

6. The component of claim 3, wherein the coating comprises a CrN layer deposited between the surface of the component and the MoxCryN layer.

7. The component of claim 2, wherein the component is an automotive component or a precision component.

8. The component of claim 3, wherein the component is an automotive component or a precision component.

9. The component of claim 4, wherein the component is an automotive component or a precision component.

10. The component of claim 2, wherein the thickness of the MoxCryN layer is about 2 μm.

11. The component of claim 3, wherein the thickness of MoxCryN layer is about 2 μm.

12. The component of claim 4, wherein the thickness of the MoxCryN layer is about 2 μm.

13. The component of claim 1, wherein the component is an automotive component or a precision component.

14. A method for producing the component of claim 1, wherein the MoxCryN layer is deposited by means of a reactive PVD process.

15. The method of claim 14, wherein the reactive PVD process is a reactive Arc PVD process, and wherein during deposition of the MoxCryN layer, at least one target comprising Mo and Cr or at least one target comprising Mo and at least one target comprising Cr are evaporated by using Arc PVD techniques in an atmosphere comprising nitrogen as reactive gas.

16. The method of claim 14, wherein the surface of the component is not modified prior to deposition of the MoxCryN layer.

17. The method of claim 14, wherein the component surface is not nitrided.

18. The method od claim 14, wherein the reactive PVD process is conducted at 200° C.

19. The component of claim 1, wherein the thickness of the MoxCryN layer is about 2 μm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a picture of a coated surface after Rockwell indentation HRC, where the hardness of the substrate is between 50 and 65 HRC and the substrate is coated with MoN;

(2) FIG. 2 shows a picture of a surface coated according to the above mentioned first possible solution and afterwards was tested according to the standard HRC Rockwell test;

(3) FIGS. 3a and 3b show pictures of tested surfaces after Rockwell indentation, where FIG. 3a shows the coated surface of the qualified reference sample and FIG. 3b shows the piston pin, respectively, which were only coated with a MoN coating;

(4) FIGS. 3c and 3d shows pictures of tested surfaces after Rockwell indentation, where FIG. 3c shows the coated surface of the qualified reference sample and FIG. 3d shows the piston pin, respectively, which were coated according to example 1; and

(5) FIG. 4 shows a picture of the tested surface after Rockwell indentation, which was coated according to example 2.

DETAILED DESCRIPTION OF EXAMPLES

Example 1

(6) A qualified reference sample made of 1.2842 19MnCrV8 with hardness 64 HRC before coating (following referred to as QRS) test piece having a steel surface and a piston pin were coated with a coating comprising a first layer consisting of CrN, which was deposited as adhesion improving layer, and a MoxCryN monolayer according to the present invention was deposited onto the CrN layer. The CrN layer was deposited by evaporating two Cr targets by using Arc PVD techniques in a nitrogen containing atmosphere. MoxCryN layer was also deposited by means of a reactive Arc PVD process. For depositing the MoxCryN layer two targets comprising Mo and two targets comprising Cr were evaporated by using Arc PVD techniques in nitrogen comprising atmosphere. The desired element composition of the MoxCryN layer was adjusted by varying the arc current at the targets operated as cathodes. The element composition of the MoxCryN layer was measured by EDX and it was determined that y was approximately 34 at %. The thickness of the CrN and MoxCryN layer was also measured and it was determined that it was 0.4 μm for the CrN layer and 2 μm for the MoxCryN, respectively. No nitriding treatment was performed before coating.

(7) With the intention of comparing the inventive coated surfaces with not inventive coated surfaces, a QRS and a piston pin were coated with a MoN coating (including a thin CrN adhesion layer) without performing previously a nitriding treatment.

(8) Afterwards corresponding Rockwell tests were carried out on all coated surfaces.

(9) The pictures of the tested surfaces after Rockwell indentation are shown in FIGS. 3a-d. FIGS. 3a and 3b on the left side show the coated surface of the QRS (on the top) and the piston pin (on the bottom), respectively, which were only coated with a MoN coating. FIGS. 3c and 3d on the right side show the coated surface of the QRS (on the top) and the piston pin (on the bottom), respectively, which were coated according to the above described example of the present invention.

(10) Neither ring-shaped fracture lines nor any sign of adhesive failure were observed on the surfaces coated according to the present invention.

Example 2

(11) A nozzle needle was coated with a coating comprising a first layer consisting of CrN, which was deposited as adhesion improving layer, and a MoxCryN monolayer according to the present invention was deposited onto the CrN layer. The same method as described in example 1 was used for depositing the coating in this example. Only the arc current at the Cr targets was adjusted to be 20 Amperes higher during deposition of the MoxCryN monolayer in order to obtain a higher Cr content in comparison with example 1. The thickness of the CrN and MoxCryN layer was measured and it was determined that it was 0.7 μm for the CrN layer and 2.3 μm for the MoxCryN, respectively.

(12) Afterwards corresponding HRC Rockwell tests were carried out on the coated surface of the nozzle needle.

(13) A picture of the tested surface after Rockwell indentation is shown in FIG. 4. Neither ring-shaped fracture lines nor any sign of adhesive failure were observed.

(14) Particularly good results were observed with 20≤y≤40.

(15) The components coated according to the present invention can be produced by using any PVD technique. For example the MoxCryN layer can be deposited by means of a reactive PVD process. The reactive PVD process can be a reactive Arc PVD process, wherein during deposition of the MoxCryN at least one target comprising Mo and Cr or at least one target comprising Mo and at least one target comprising Cr are evaporated by using Arc PVD techniques in an atmosphere comprising nitrogen as reactive gas.

(16) However the methods for producing coated components according to the present invention are not limited by this description.

(17) The surfaces of the components coated according to the present invention exhibit additionally very good tribological properties, in particular concerning wear resistance and reduced friction.