SLIDING ELEMENT WITH MAX PHASE COATING

Abstract

The invention relates to a sliding element, in particular a piston ring, to a method for producing same, and to the use of the sliding element in a tribological system. The sliding element has a coating which has at least one adhesive layer and a MAX phase layer from the inside towards the outside. The MAX phase layer has the composition M.sub.n+1AX.sub.n (n=1, 2, 3), wherein M represents an element from the group Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, and Ta, A represents an element from the group Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Tl, and Pb, and X represents the elements C or N.

Claims

1. A sliding element with a coating, which from the inside outwards, has at least the following layers: one adhesive layer, and a MAX phase layer with the composition M.sub.n+1AX.sub.n (n=1, 2, 3), wherein M represents an element from the group Sc, Ti, V, Cr, Zr, Nb, Mo, Hf and Ta, A represents an element from the group Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Ti and Pb, and X represents the elements C or N.

2. The sliding element according to claim 1, wherein the adhesive layer contains chromium, chromium nitride, titanium and/or tungsten.

3. The sliding element according to claim 1, wherein the thickness of the adhesive layer is 0.1-3.0 m.

4. The sliding element according to claim 1, wherein the coating is applied onto a sliding element substrate and the sliding element substrate consists of cast iron or steel, and consists of one of the following materials: unalloyed, untempered cast iron with lamellar graphite alloyed, heat-treated or not heat-treated grey cast iron with carbides tempered spheroidal cast iron untempered vermicular graphite cast iron cast steel with at least 10% by weight chromium, nitrided or non-nitrided chromium steel with at least 10% by weight chromium, nitrided or non-nitrided chromium-silicon-carbon steel.

5. The sliding element according to claim 1, wherein the coating has an average roughness depth R.sub.z<7 m, a reduced peak depth R.sub.pk<0.4 m, and/or a core roughness depth R.sub.k<1 m.

6. The sliding element according to claim 1, wherein in the MAX phase layer with the composition M.sub.n+1AX.sub.n, element M represents either Ti or Cr, element A represents either Al or Si and n=1 or 2.

7. The sliding element according to claim 6; wherein the MAX phase layer is selected from one of the following layer types: Cr.sub.2AlC: type 211; proportion of Cr: 48-52 at. %; proportion of Al: 24-26 at. %; proportion of C: 24-26 at. % Cr.sub.2AlN: type 211; proportion of Cr: 48-52 at. %; proportion of Al: 24-26 at. %; proportion of N: 24-26 at. % Ti.sub.2AlC: type 211; proportion of Ti: 48-52 at. %; proportion of Al: 24 -26 at. %; proportion of C: 24-26 at. % T.sub.12AlN: type 211; proportion of Ti: 48-52 at. %; proportion of Al: 24-26 at. %; proportion of N: 24-26 at. % Ti.sub.3SiC.sub.2: type 312; proportion of Ti: 48 -52 at. %; proportion of Si: 16-18 at. %; proportion of C: 32-34 at. %,

8. The sliding element according to claim 1, wherein the coating has a hardness of 2 to 6 GPa.

9. The sliding element according to claim 1, wherein the coating has a modulus of elasticity of 150 to 350 GPa.

10. A method for producing a sliding element according to claim 1, comprising the following steps: providing a sliding element substrate, coating at least a partial surface of the sliding element substrate with an adhesive layer, wherein the adhesive layer contains chromium, chromium nitride, titanium and/or tungsten, and coating at least a part of the adhesive layer with a MAX phase layer, wherein the MAX phase layer has the composition M.sub.n+1AX.sub.n (n=1, 2, 3), and wherein M represents an element from the group Sc, Ti, V, Cr, Zr, Nb, Mo, Hf and Ta, A represents an element from the group Al, Si, P, S, Ga, Ge, As, Cd, In, Sn, Tl and Pb, and X represents the elements C or N.

11. The method according to claim 10, wherein the roughness of the MAX phase layer and/or adhesive layer can be reduced after the coating process by lapping, belt and/or brush polishing.

12. The method according to claim 10, characterised in that at least one layer of the coating is deposited by means of a PVD method, CVD method or thermal spraying.

13. A sliding element according to claim 1 in a tribological system, including said sliding element and, a pairing friction part which remains in frictional contact with said sliding element, and at least one lubricant, wherein the lubricant contains additives.

14. The element in a tribological system according to claim 13, wherein the additives comprise organic friction modifiers, inorganic friction modifiers and/or polymeric friction modifiers.

15. The sliding element according to claim 1, wherein the sliding element is a piston ring.

16. The sliding element according to claim 1, wherein the adhesive layer consists of chromium, chromium nitride, titanium and/or tungsten,

17. The sliding element of claim 5, wherein R.sub.z<4 m, R.sub.pk<0.2 m and R.sub.k<0.6 m.

18. The method according to claim 10, wherein the substrate is cast iron or steel.

19. The method according to claim 10, wherein the adhesive layer consists of chromium, chromium nitride, titanium and/or tungsten.

20. The method according to claim 12 wherein the coating deposition is carried out by means of High Power Pulsed Magnetron Sputtering (HPPMS) or Pulsed Laser Deposition (PLD).

21. The sliding element according to claim 13, wherein the tribological system is a Diesel or Otto engine.

22. The sliding element according to claim 13, wherein the lubricant is engine oil.

Description

PREFERRED EMBODIMENT

[0046] A preferred embodiment consists in a sliding element in the form of a piston ring whose base material is chromium-silicon-carbon steel. The outer circumferential surface of the piston ring has the function of a substrate onto which a chromium nitride-adhesive layer is first deposited by means of a PVD method to a thickness of 1 m. A MAX phase layer with a thickness of 1 m with the sum formula Ti3SiC2 is then applied onto the adhesive layer by means of High Power Pulsed Magnetron Sputtering (HPPMS), with the actual proportions of components Ti: 48-52 at. %, Si: 16-18 at. % and C: 32-34 at. %. The average roughness depth of the coating is finally adjusted by belt polishing to a value R.sub.z<4 m. A sliding element with the above-described coating shows more particularly an extreme robustness under thermal stress against oxidation and fracture.