Article having a hard lubricious coating
A valving assembly for a motor vehicle includes a hard, lubricious and chemically inert coating of graphitic carbon. The coating may include a metal. Preferred metals include chromium or other transition metals.
1. A valving assembly for a fuel injector, said valving assembly comprising:
a valve member and a seat member, said valve member and said seat member being selectably engageable so as to control the flow of a fuel therebetween, wherein at least a portion of at least one of said valve member and said seat member is coated with an essentially graphitic carbon coating which contains no more than 10 atomic percent of hydrogen.
2. The valving assembly of claim 1 , wherein said graphitic carbon coating further includes a metal.
3. The valving assembly of claim 2 , wherein said graphitic carbon coating includes 0.5-10 atomic percent of said metal.
4. The valving assembly of claim 2 , wherein said metal is a transition metal.
5. The valving assembly of claim 4 , wherein said transition metal is a Group Va-VIIa transition metal.
6. The valving assembly of claim 4 , wherein said transition metal is a Group VIa transition metal.
7. The valving assembly of claim 4 , wherein said transition metal is chromium.
8. The valving assembly of claim 4 , wherein said transition metal comprises 1-4 atomic percent of said coating.
9. The valving assembly of claim 2 , wherein said graphitic carbon coating includes no more than 0.5 atomic percent of a metal carbide.
10. The valving assembly of claim 1 , wherein said coating has a thickness in the range of 1-5 microns.
11. The valving assembly of claim 1 , wherein no more than 20 atomic percent of said graphitic carbon coating is comprised of tetrahedral carbon.
12. The valving assembly of claim 1 , wherein said graphitic carbon coating is a sputtered coating.
13. The valving assembly of claim 2 , wherein said coating is a co-sputtered film of graphitic carbon and said metal.
14. The valving assembly of claim 2 , wherein said coating is is prepared by a non-reactive sputtering process.
15. The valving assembly of claim 14 , wherein said non-reactive sputtering process is an unbalanced magnetron sputtering process.
16. The valving assembly of claim 1 , wherein a metallic bonding layer is disposed beneath said graphitic carbon coating.
17. The valving assembly of claim 16 , wherein said metallic bonding layer has a thickness in the range of 0.2-0.8 microns.
18. The valving assembly of claim 16 , wherein said bonding layer comprises chromium.
19. The valving assembly of claim 16 , wherein the interface between said bonding layer and said graphitic carbon coating is compositionally graded.
20. The valving assembly of claim 1 , wherein said coating has a film hardness in the range of 1000-2000 Vickers, and a coefficient of friction in the range of 0.05-0.15.
21. The valving assembly of claim 1 , wherein said coating has an electrical resistivity in the range of 1×10 −3 −5×10 −3 Ω-cm.
22. A valving assembly for an internal combustion engine, said valving assembly comprising;
a valve member and a seat member, said valve member and said seat member being selectably engageable so as to control the flow of a fluid therebetween, wherein at least a portion of at least one of said valve member and said seat member is coated with a carbon coating, said coating including 1-4 atomic percent of a transition metal, no more than 10 atomic percent of hydrogen and no more than 0.5 atomic percent of a metal carbide, said coating being further characterized in that it has a hardness in the range of 1000-2000 Vickers, a coefficient of friction of 0.05-0.15, and an electrical resistivity in the range of 10×10 −4 −1×10 −2 Ω-cm.