Effect of SiO2 Nanoparticles as Additive on Antiwear and Extreme Pressure Properties of Lithium Grease

Surface modified SiO_2 nanoparticles were synthesized. A four-ball machine was used to investigate the tribological behavior of SiO_2 nanoparticles as additive in lithium grease. The worn surfaces of steel balls were analyzed by means of scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Analytical results indicate that SiO_2 nanoparticles as additive can increase antiwear ability and load-carrying capacity of lithium grease. The reason is that SiO_2 nanoparticles can deposited in boundary film play the role of self-replentish in the worn surface.