Effect of SiO₂ nanoparticles as additive on antiwear and extreme pressure properties of lithium grease

Surface modified SiO₂ nanoparticles were synthesized. A four-ball machine was used to investigate the tribological behavior of SiO₂ 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 SiO₂ nanoparticles as additive can increase antiwear ability and load-carrying capacity of lithium grease. The reason is that SiO₂ nanoparticles can deposited in boundary film play the role of self-replenish in the worn surface.