Tribological Properties of CaCO3 Nanoparticles as an Additive in Lithium Grease

CaCO3 nanoparticles with an average size of 45 nm were synthesized via the carbonation method. The tribological properties of the CaCO3 nanoparticles as an additive in lithium grease were evaluated with a four-ball tester. The results show that these CaCO3 nanoparticles exhibit good performance in anti-wear and friction-reduction, load-carrying capacity, and extreme pressure properties. The action mechanism was estimated through analysis of the worn surface with X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). The results indicate that a boundary film mainly composed of CaCO3, CaO, iron oxide, and other organic compounds was formed on the worn surface during the friction process.