CHARACTERIZATION OF TRANSFER LAYERS ON STEEL SURFACES SLIDING AGAINSTDIAMOND-LIKE HYDROCARBON FILMS IN DRY NITROGEN

Carbon-rich transfer layers on sliding contact surfaces play important roles in the tribological performance of diamond-like hydrocarbon (DL HC) films. In this study, we investigated the nature of these layers f ormed on M50 balls during sliding against DLHC films (1.5 mu m thick) prepared by ion-beam deposition. Long-duration sliding tests were perf ormed with steel balls sliding against the DLHC coatings in dry nitrog en at room temperature, approximately 22 +/- 1 degrees C. Results indi cated that the friction coefficients of test pairs were initially abou t 0.12 but decreased steadily with sliding distance to 0.02-0.03 and r emained constant throughout the tests, which lasted for more than 2500 00 sliding cycles (approximately 30 km). This low-friction regime appe ared to coincide with the formation of a carbon-rich transfer layer on the sliding surfaces of M50 balls. Micro-laser Raman spectroscopy and electron microscopy were used to elucidate the structure and chemistr y of these transfer layers and to reveal their possible role in the we ar and friction behavior of DLHC-coated surfaces.