Effect Of Ultrasonic Rolling Process On Contact Fatigue Performance Of GCr15SiMn Bearing Steel

Bearing is known as the heart of industry and mechanical joints.As basic parts and key parts,bearing is widely used in all walks of life,which is the key to the good reliability and safety of the whole equipment.However,fatigue failure is one of the most important failure forms of bearing.Fatigue failure generally occurs first on the surface of bearing ring.Therefore,surface strengthening treatment to improve the fatigue resistance of bearing seat ring can greatly improve the service life of bearing.As an efficient surface strengthening technology,ultrasonic rolling can improve the surface quality by improving the surface strength and surface roughness.Therefore,it is of great significance to explore the appropriate ultrasonic rolling process for improving the fatigue resistance of bearing seat ring.In this paper,GCr15 Si Mn bearing ring was taken as the research object,and six different processes were used for ultrasonic rolling processing.The differences in morphology,hardness,fatigue resistance and microstructure between the original and processed rings and their causes were analyzed and compared by using optical microscope,scanning electron microscope(SEM)and hardness tester.The second-order response surface methodology was used to optimize the ultrasonic rolling processing technology.The results show that after ultrasonic rolling processing,the grinding furrow depth on the bearing ring surface becomes shallow,the micro-crack tip angle decreases,and the defects are reduced.The surface roughness Ra value decreases by 67%,and the surface hardness increases by 2%.The surface hardness and surface microstructure uniformity are improved,and the surface hardening layer and plastic deformation layer are preset.The current is the main factor affecting the surface roughness,followed by the static pressure,and the feed rate is minimal.The static pressure is the dominant factor affecting the surface hardness,followed by the current,and the feed rate is minimal.With the increase of current and static pressure,the decrease of feed rate,the surface roughness decreases,the surface hardness increases,the thickness and uniformity of plastic deformation layer increase.The contact fatigue life of the three groups of bearing rings after ultrasonic rolling processing is increased,and the optimal fatigue life of the processed bearing ring is about three times that of the original bearing ring.The main failure reason of original bearing ring is the spalling of fine grain structure in surface grinding.Ultrasonic rolling processing mainly improves the contact fatigue life of bearing ring by eliminating surface defects and strengthening the difference of microstructure weakening.Compared with the original bearing ring fatigue part,the processed bearing ring fatigue part has smaller raceway depth and width,smaller surface roughness,fewer cracks,spalling and other damage,smaller size.Parallel arctype fatigue cracks appear on the surface of ultrasonic rolling processing bearing ring with long life.