Effect of process parameters on mechanical and tribological performance of pulsed-DC sputtered TiC/a-C:H nanocomposite films

Mechanical, structural, chemical bonding (sp(3)/sp(2)). and tribological properties of films deposited by pulsed-DC sputtering of Ti targets in Ar/C2H2 plasma were studied as a function of the substrate bias voltage, Ti-target current, C2H2 flow rate and pulse frequency by nanoindentation, Raman spectroscopy and ball-on-disc tribometry. The new findings in this study comprise: dense, column-free, smooth, and ultra-low friction TiC/a-C:H films are obtained at a lower substrate bias voltage by pulsed-DC sputtering at 200 and 350 kHz frequency. The change in chemical and phase composition influences the tribological performance where the TiC/a-C:H films perform better than the pure a-C:H films. In the case of TiC/a-C:H nanocomposite films, a higher sp(2) content and the presence of TiC nanocrystallites at the sliding surface promote formation of a transfer layer and yield lower friction. In the case of a-C:H films, a higher sp(3) content and higher stress promote formation of hard wear debris during sliding, which cause abrasive wear of the ball counterpart and yield higher friction. (C) 2010 Elsevier B.V. All rights reserved.