Tribological behavior of mineral and synthetic ester base oil containing MoS2 nanoparticles

0.2, 1.0, and 2.0 wt.% concentration of molybdenum disulfide (MoS2) nanoparticles were dispersed in mineral and synthetic ester base oil. Their tribological behavior investigated using a tribometer with pin-on-disk and four-ball configuration under different conditions of contact pressures, sliding speeds and oil bath temperatures, respectively. The results demonstrate that nano-MoS2 in mineral oil can reduce wear and friction coefficient characteristics at all concentrations tested, especially at 2.0 wt.%. XPS analysis of the worn surfaces indicated that decomposed MoS2 was adsorbed on worn surface, and S and Mo elements of the compound reacted with the metal and existed in the form of sulfide or molybdenum compounds, both of which contributed to the formation of a mix lubricating film. A wear mechanism of MoS2 as antiwear additive is proposed.