Carbon containing layer

Abstract

A workpiece comprises a substrate having a sliding surface provided with a friction-reducing coating. Such coating consists essentially of elemental carbon dispersed in a matrix formed of at least one metallic element in the proportions of 50.1 to 99.1 at % of the elemental carbon and 0.1 to 49.9 at % of the metallic element. The ratio of the metallic element to the elemental carbon differs from the stoichiometric ratio of the carbide.

What is claimed is: 
     
       1. A workpiece comprising a substrate having a sliding surface provided with a friction-reducing coating; said coating consisting essentially of elemental carbon dispersed in a matrix formed of at least one metallic element in the proportions of 50.1 to 99.9 at % of the elemental carbon and 0.1 to 49.9 at % of the metallic element, the ratio of the metallic element to the elemental carbon differing from the stoichiometric ratio of a carbide.   
     
     
       2. A workpiece according to claim 1, in which the substrate is metallic. 
     
     
       3. A workpiece according to claim 1, in which the coating consists essentially of 60 to 97 at % of elemental carbon and 40 to 3 at % of at least one metallic element. 
     
     
       4. A workpiece according to claim 3, in which the coating consists essentially of 80 to 95 at % of elemental carbon and 20 to 5 at % of at least one metallic element. 
     
     
       5. A workpiece according to claim 1, in which the metallic element is an element of group Ib, IIb, IIIa, IV, Vb, VIb, VIIb or VIII of the periodic table. 
     
     
       6. A workpiece according to claim 5, in which the metallic element is silicon, tantalum, tungsten, ruthenium or iron. 
     
     
       7. A method of making a workpiece according to claim 1, which includes coating the sliding surface of the substrate by chemical or physical vapour deposition of the elemental carbon and the metallic element. 
     
     
       8. A method according to claim 7, which includes depositing the elemental carbon and the metallic element by cathode sputtering of a target formed from carbon and the metallic element. 
     
     
       9. A method according to claim 7, which includes depositing the elemental carbon and the metallic element by cathode sputtering of a target formed from the metallic element in an atmosphere of an inert gas and a hydrocarbon gas. 
     
     
       10. A method according to claim 9, which includes starting the deposition in an atmosphere containing only the inert gas and then continuing the deposition under an inert gas-hydrocarbon gas atmosphere. 
     
     
       11. A method according to claim 9, in which the inert gas comprises argon. 
     
     
       12. A method according to claim 9, in which the hydrocarbon gas comprises acetylene. .Iadd. 
     
     
       13.  A workpiece comprising: a substrate having a surface; and a friction-reducing coating on the surface of the substrate having a coefficient of sliding friction;   characterized in that the friction-reducing coating consists essentially of elemental carbon dispersed in a matrix formed by at least one metallic element, the ratio of carbon to the metallic element ranging from 50.1/49.9 to 99.9/0.1, said ratio differing from the stoichiometric ratio of a carbide. .Iaddend. .Iadd.   
     
     
       14.  A workpiece as claimed in claim 13, characterized in that the friction-reducing coating is X-ray amorphous. .Iaddend. .Iadd.15. A workpiece comprising: a substrate having a surface; and   a friction-reducing coating on the surface of the substrate, said friction-reducing coating having a coefficient of sliding friction;   characterized in that the friction-reducing coating consists essentially of elemental carbon dispersed in a matrix formed by at least one metallic element, the ratio of carbon to the metallic element ranging from 50.1/49.9 to 99.9/0.1 said ratio differing from the stoichiometric ratio of a carbide, said coating further containing impurities in amounts which do not materially increase the coefficient of sliding friction of the coating as compared to such a coating without such impurities. .Iaddend. .Iadd.16. A workpiece as claimed in claim 15, characterized in that the   
     
     
        friction-reducing coating is X-ray amorphous. .Iaddend. .Iadd.17.  A system comprising: a first workpiece having a surface;   a second workpiece having a surface, the surface of the first workpiece bearing against and sliding with respect to the surface of the second workpiece; and   a friction-reducing coating on the surface of the first workpiece;   characterized in that the friction-reducing coating consists essentially of elemental carbon dispersed in a matrix formed by at least one metallic element, the ratio of carbon to the metallic element ranging from 50.1/49.9 to 99.9/0.1 said ratio differing from the stoichiometric ratio of a carbide. .Iaddend. .Iadd.18. A system as claimed in claim 17, characterized in that the friction-reducing coating is X-ray amorphous. .Iaddend. .Iadd.19. A system as claimed in claim 18, further comprising a friction-reducing coating on the surface of the second workpiece.