CrN films were made on surface of piston rings to improve its tribological properties and service life.Effects of nitrogen content to prepare the film on hardness and phase structure were studied.The high-temperature tribological properties of Cr plating and CrN films were compared with CETR friction tester.The results show that nitrogen partial pressure significantly affects the mechanical properties of CrN films.With increasing N2 partial pressure
preferential growth orientation of the film changed from Cr2N(211) to CrN(220) phase
leading to two hardness peaks corresponding to the Cr2N and CrN phases
respectively.Having higher high-temperature wear resistance and lower friction coefficient than Cr plating
the CrN films are suitable for piston rings under high temperature conditions.