Experiments and molecular dynamic simulations on the cryogenic tribological behaviors of pure silver in liquid nitrogen

Pure silver alone or in cooperation with other self-lubricating materials exerts outstanding frictional modification effects owing to its remarkable ductility and low shear stress. In this study, puzzling tribological behaviors of pure silver in liquid nitrogen, characterized by larger coefficient of friction but slighter wear degree compared with room-temperature condition, were experimentally observed on a self-developed reciprocating-type cryogenic tribometer at first. Molecular dynamic simulations about the adsorption and tribological properties of pure silver in the environments of liquid nitrogen, water, room temperature, and low temperature, were conducted to reproduce the experimental phenomena and reveal the underlying mechanism. Furthermore, a physical explanation based on the generated hexagonal close-packed (HCP) dislocations by sliding friction was given.