Synthesis of superlow-friction carbon films from highly hydrogenated methane plasmas

In this study, we investigated the friction and wear performance of diamond -like carbon films (DLC) derived from increasingly hydrogenated methane pla smas. The films were deposited on steel substrates by a plasma-enhanced che mical vapor deposition process at room temperature and the tribological tes ts were performed in dry nitrogen. Tests results revealed a close correlati on between the hydrogen in the source gas plasma and the friction and wear coefficients of the DLC films. Specifically, films grown in plasmas with hi gher hydrogen-to-carbon ratios had much lower friction coefficients and wea r rates than did films derived from source gases with lower hydrogen-to-car bon ratios. The lowest friction coefficient (0.003) was achieved with a fil m derived from 25% methane, 75% hydrogen, while a relatively high coefficie nt of 0.015 was found for films derived from pure methane. Similar correlat ions were observed for wear rates. Films derived from hydrogen-rich plasmas had the least wear, while films derived from pure methane suffered the hig hest wear. We used a combination of surface analytical methods to character ize the structure and chemistry of the DLC films and worn surfaces. (C) 200 0 Published by Elsevier Science B.V. All rights reserved.