Advanced silicate-based lubricant additive induced diamond-like carbon structured restoration layer

An advanced silicate based lubricant additive has been employed in long-term pin-on-disk tribological experiments. The worn steel/steel surfaces were characterized using nano-indentation, SEM, XPS, and Raman spectroscopy for their physical, mechanical, and chemical properties. The average nano-hardness of the repaired layers on the disk and the pin is 10.2 GPa and 16.7 GPa respectively, which is substantially higher than that of the disk (HV 221, or 0.71 GPa) and the pin (HRC55, or 1.8 GPa) before tribological tests, forming super hard surfaces on the contact pair surfaces. Combined Raman spectroscopy and XPS studies suggest the formation of diamond-like carbon based restoration layers. A new formation mechanism of the restoration DLC layer contributing to hard and smooth contact surfaces is proposed. (C) 2015 Elsevier Ltd. All rights reserved.