Effect of source gas chemistry on tribological performance of diamond-like carbon211 films

摘要

In this study, we investigated the effects of various source gases (i. e.,211u001emethane, ethane, ethylene, acetylene and methane + hydrogen) on friction and wear 211u001eperformance of diamond-like carbon (DLC) films. Specifically, we described the 211u001eanomalous nature and fundamental friction and wear mechanisms of DLC films 211u001ederived from gas discharge plasmas with very low to very high hydrogen content. 211u001eThe films were deposited on steel substrates by a plasma enhanced chemical vapor 211u001edeposition process at room temperature and the tribological tests were performed 211u001ein dry nitrogen. The results of tribological tests revealed a close correlation 211u001ebetween the friction and wear coefficients of the DLC films and the source gas 211u001echemistry. Specifically, films grown in source gases with higher hydrogen-to-211u001ecarbon ratios had much lower friction coefficients and wear rates than the films 211u001ederived from source gases with lower hydrogen-to-carbon ratios. The lowest 211u001efriction coefficient (0.002) was achieved with a film derived from 25% methane--211u001e75% hydrogen while the films derived from acetylene had a coefficient of 0.15. 211u001eSimilar correlations were observed on wear rates. Specifically, the films derived 211u001efrom hydrogen rich plasmas had the least wear while the films derived from pure 211u001eacetylene suffered the highest wear. We used a combination of scanning and 211u001etransmission electron microscopy and Raman spectroscopy to characterize the 211u001estructural chemistry of the resultant DLC films.