Carbon containing layer

Claim 2

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.

Claim 3

A workpiece according to claim 1, in which the substrate is metallic.

Claim 4

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.

Claim 5

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.

Claim 6

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.

Claim 7

A workpiece according to claim 5, in which the metallic element is silicon, tantalum, tungsten, ruthenium or iron.

Claim 8

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.

Claim 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 carbon and the metallic element.

Claim 10

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.

Claim 11

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.

Claim 12

A method according to claim 9, in which the inert gas comprises argon.

Claim 13

A method according to claim 9, in which the hydrocarbon gas comprises acetylene. .Iadd.

Claim 14

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.

Claim 15

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.

Claim 16

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

Claim 17

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.