Anti-wear and friction properties of nanoparticles as additives in the lithium grease

Abstract

TiO2/CuO nano-particles were dispersed into lithium grease to improve the lubricating properties of the greases. Then, the process of sliding friction was tested. The friction force of the contact interface between a ball and a flat surface with TiO2/CuO nano-grease was measured for a ball on a flat sliding wear tester. The worn surface was examined by a surface roughness tester and scanning electron microscopy (SEM). The tested lithium grease was synthesized with 0.5wt.%, 1.0wt.%, 1.5wt.% and 2.0wt.% TiO2/CuO nano-particles. Results indicate that the TiO2/CuO nano-particle additives can improve the wear resistance of lithium grease and decrease the friction coefficient. In addition, the results show that a 1.0 wt% content of TiO2 nano-particles is the most efficient in reducing friction and wear, and can significantly reduce the friction coefficient of the rubbing interface by about 40%, according to the friction tests. The wear of the lithium grease with a 2.0wt.% content of CuO nano-particles added can reduce wear about by 60% in comparison with lithium grease. Furthermore, the SEM analysis results demonstrate that the addition of tribo-film forms and TiO2/CuO nano-particles on the worn surface is responsible for the decrease in friction and wear.