GLTRS--Glenn
TITLE AND SUBTITLE:
Surface Design and Engineering Toward Wear-Resistant, Self-Lubricating Diamond Films and Coatings

AUTHOR(S):
Kazuhisa Miyoshi

REPORT DATE:
February 1999

FUNDING NUMBERS:
WU-523-22-13-00

PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135-3191

PERFORMING ORGANIZATION REPORT NUMBER:
E-11425

SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
Washington, DC 20546-0001

REPORT TYPE AND DATES COVERED:
Technical Memorandum

SPONSORING/MONITORING AGENCY REPORT NUMBER:
NASA TM-1999-208905

SUPPLEMENTARY NOTES:
Prepared for the 128th Annual Meeting & Exhibition sponsored by The Minerals, Metals & Materials Society, San Diego, California, February 28-March 4, 1999. Responsible person, Kazuhisa Miyoshi, organization code 5140, (216) 433-6078.

ABSTRACT:
The tribological properties of chemical-vapor-deposited (CVD) diamond films vary with the environment, possessing a Jekyll-and-Hyde character. CVD diamond has low coefficient of friction and high wear resistance in air but high coefficient of friction and low wear resistance in vacuum. Improving the tribological functionality of materials (such as achieving low friction and good wear resistance) was an aim of this investigation. Three studies on the surface design, surface engineering, and tribology of CVD diamond have shown that its friction and wear are significantly reduced in ultrahigh vacuum. The main criteria for judging whether diamond films are an effective wear-resistant, self-lubricating material were coefficient of friction and wear rate, which must be less than 0.1 and on the order of 10-6 mm3/N·m, respectively. In the first study the presence of a thin film (<1 mm thick) of amorphous, nondiamond carbon (hydrogenated carbon, also called diamondlike carbon or DLC) on CVD diamond greatly decreased the coefficient of friction and the wear rate. Therefore, a thin DLC film on CVD diamond can be an effective wear-resistant, lubricating coating in ultrahigh vacuum. In the second study the presence of an amorphous, nondiamond carbon surface layer formed on CVD diamond by ion implantation significantly reduced the coefficient of friction and the wear rate in ultrahigh vacuum. Therefore, such surface layers are acceptable for effective self-lubricating, wear-resistant applications of CVD diamond. In the third study CVD diamond in contact with cubic boron nitride exhibited low coefficient of friction in ultrahigh vacuum. Therefore, this materials combination can provide an effective self-lubricating, wear-resistant couple in ultrahigh vacuum.

SUBJECT TERMS:
Materials; Coatings

NUMBER OF PAGES:
17

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1999/TM-1999-208905.pdf
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