Reduced-friction coatings

• US 20090074522A1
• Filed: 09/16/2008
• Published: 03/19/2009
• Est. Priority Date: 09/17/2007
• Status: Abandoned Application

• Current Assignee: Northwestern University
• Original Assignee: Northwestern University
• Inventors: Koshy, Robin A., Marks, Laurence D., Graham, Michael E.
• Application Number:
  US12/283,918
• Publication Number:
  US 20090074522A1
• Time in Patent Office: Days
• US Class Current: 407/119
• CPC Class Codes: B23B 2222/64 Nickel
• CPC Class Codes: B23B 2228/10 Coatings
• CPC Class Codes: B23B 2228/105 with specified thickness
• CPC Class Codes: B23B 2228/52 Solid lubricants
• CPC Class Codes: B23B 27/14 Cutting tools of which the bits or tips or cutting inserts are of special material
• CPC Class Codes: C10M 103/06 Metal compounds
• CPC Class Codes: C10M 2201/0613 used as base material
• CPC Class Codes: C10M 2201/0873 used as base material
• CPC Class Codes: C10N 2010/12 Groups 6 or 16
• CPC Class Codes: C10N 2030/06 Oiliness; Film-strength; Anti-wear; Resistance to extreme pressure
• CPC Class Codes: C10N 2050/02 dissolved or suspended in a carrier which subsequently evaporates to leave a lubricant coating
• CPC Class Codes: C23C 28/044 coatings specially adapted for cutting tools or wear applications
• CPC Class Codes: C23C 28/42 characterized by the composition of the alternating layers
• CPC Class Codes: C23C 30/005 on hard metal substrates
• CPC Class Codes: Y10T 407/27 comprising tool of specific chemical composition

Abstract

A coating is provided having a first metal or non-metal nitride layer and a second metal or non-metal nitride layer wherein the first and second nitride layers are sufficiently resistant to interdiffusion to maintain respective individual layer structure and strength at an elevated operating temperature when a coating contact surface is in sliding contact with another material and wherein one of the first layer or second layer includes a component that is oxidizable at the contact surface to form a friction-reducing lubricous oxide material at the contact surface.

Claims

1. A coating having a first layer comprising a first nitride and a second layer comprising a second nitride wherein the first nitride and the second nitride are sufficiently immiscible to maintain respective layer individuality at an elevated service temperature when a contact surface of the coating is in sliding contact with another material and wherein one of the first layer or second layer includes a component that is oxidizable at the contact surface to form a friction-reducing lubricious oxide at the contact surface.

2. The coating of claim 1 wherein the first nitride comprises a metal nitride.

3. The coating of claim 2 wherein the metal nitride comprises CrN.

4. The coating of claim 1 wherein the second nitride comprises a metal nitride.

5. The coating of claim 4 wherein the metal nitride comprises Mo₂N

6. The coating of claim 1 wherein one of the first nitride or second nitride comprises comprises a non-metal nitride.

7. The coating of claim 6 wherein the non-metal nitride comprises BN.

8. The coating of claim 1 wherein the first layer and the second layer are deposited one on the other in a repeating pattern to provide a multi-layered coating.

9. The coating of claim 1 wherein the first nitride and the second nitride each has a thickness in the range of 1 to 30 nanometers.

10. The coating of claim 1 wherein the first nitride and the second nitride each has a hardness at room temperature in the range of 20 GPa to 30 GPa.

11. A cutting tool comprising a tool substrate and the coating of claim 1 on the substrate.

12. A bearing surface comprising a load-bearing substrate and the coating of claim 1 on the substrate.

13. A method of cutting a workpiece using a coated cutting tool, comprising contacting a contact surface of a coated cutting tool and the workpiece while providing little or no lubricant from an external source, wherein the coating comprises a first layer comprising a first metal nitride and a second layer comprising a second metal nitride and wherein the first metal nitride and the second metal nitride are sufficiently immiscible to maintain respective layer individuality at elevated cutting temperature when the contact surface of the coated cutting tool is in cutting contact with the workpiece and wherein one of the first layer or second layer includes a component that is oxidizable at the contact surface to form a friction-reducing lubricious oxide at the contact surface.

14. The method of claim 13 wherein the first nitride comprises a metal nitride.

15. The method of claim 14 wherein the metal nitride comprises CrN.

16. The method of claim 13 wherein the second nitride comprises a metal nitride.

17. The method of claim 16 wherein the metal nitride comprises Mo₂N

18. The method of claim 13 wherein one of the first nitride or second nitride comprises a non-metal nitride.

19. The method of claim 18 wherein the non-metal nitride comprises BN.

20. The method of claim 13 wherein the first layer and the second layer are deposited one on the other in a repeating pattern to provide a multi-layered coating.

21. The method of claim 13 wherein the first nitride and the second nitride each has a thickness in the range of 1 to 30 nanometers.

22. The method of claim 13 wherein the first nitride and the second nitride each has a hardness at room temperature in the range of 20 GPa to 30 GPa.

23. The method of claim 13 including controlling oxidation of the contact surface by introducing a cover gas that is not oxygen.