Microstructure and tribological property of Cr/CrN nano-multilayer film deposited on piston ring

Abstract：In order to improve the tribological property of an engine piston ring and increase its service life,a Cr/CrN nano-multilayer film was prepared on the surface of the piston ring with multi-arc ion plating technology.The microstructure,element distribution,nanohardness and slide wear resistance of the Cr/CrN nano-multilayer film with different modulation periods were systematically analyzed with X-ray diffractometer（XRD）,transmission electron microscope（TEM）,auger energy spectrometer（AES）,nanohardness tester as well as CETR friction and wear tester,respectively.The results show that the Cr/CrN multilayer film is composed of CrN,Cr2N and Cr phases,and the preferential orientation of the film appears in CrN（200） direction.With reducing the modulation period,the hardness and residual stress of the film increase.When the modulation period is 80 nm,the hardness of the film reaches the maximum value of 21.5 GPa.When the modulation period is 120 nm,the H3/E2 value attains the maximum level and the scratch critical load value is highest as well.The results of friction and wear experiment show that compared with the electroplated Cr and CrN layers,the Cr/CrN multilayer film has relatively better slide wear resistance,and the corresponding wear mechanism is mainly abrasive wear.The Cr/CrN multilayer film is possibly replace the electroplated Cr layer deposited on the piston ring.