Preparation and Tribological Properties of Carbon-Coated WS Nanosheets.

WS-C is produced from a hydrothermal reaction, in which WS nano-sheets are coated with carbon, using glucose as the carbon source. In order to investigate the tribological properties of WS-C as a lubricant additive, WS-C was modified by surfactant Span80, and friction tests were carried out on an MRS-10A four-ball friction and wear tester. The results show that Span80 can promote the dispersibility of WS-C effectively in base oil. Adding an appropriate concentration of WS-C can improve the anti-wear and anti-friction performance of the base oil. The friction coefficient reached its lowest point upon adding 0.1 wt % WS-C, reduced by 16.7% compared to the base oil. Meanwhile, the wear scar diameter reached its minimum with 0.15 wt % WS, decreasing by 26.45%. Moreover, at this concentration, the depth and width of the groove and the surface roughness on the wear scar achieved their minimum. It is concluded that WS-C dispersed in oil could enter friction pairs to avoid their direct contact, thereby effectively reducing friction and wear. At the same time, WS-C reacts with the friction matrix material to form a protective film, composed of C, FeO, FeSO, WO, and WS, repairing the worn surface.