Study On Surface Modification Of GCR15SiMn Bearing Steel By Ultrasonic Rolling Processing

As an important moving part of mechanical equipment,bearing plays a key role in the safe operation of equipment.Bearing failure will not only lead to the abnormal operation of the equipment but also serious accidents.Surface strengthening is one of the means to improve the service life of the bearing,which is of great significance to improve the quality of bearing manufacturing and the safe operation of mechanical equipment.In this paper,the surface of the GCr15SiMn bearing roller was treated by surface ultrasonic rolling(SURP).The strengthening effect of SURP was studied by analyzing and testing the surface morphology,surface microstructure,surface roughness,residual stress and residual austenite content before and after treatment.Furthermore,the influence of the surface ultrasonic rolling process on rolling contact fatigue life of GCr15SiMn bearing steel was studied by the thrust ball bearing,which was processed according to standard bearing size,hereinafter referred to as race sample.The results show that the surface microstructure of the bearing roller and seat ring after treatment has obvious plastic deformation,exhibiting an about 1.5μm plastic deformation layer.With the decrease of the distance from the surface,the degree of deformation increases.The grain size of martensite in the surface layer was obviously refined,and the grains were elongated along the surface at 30 degrees.The roughness Ra of the original roller sample is 0.36μm while the treated sample is reduced to 0.066μm.The roughness Ra of the original ring sample is 0.20μm while the treated sample decreases to 0.055μm.The average increase of surface hardness of roller sample after treatment is about 2.18%while seat ring sample is about3%.The increase of residual compressive stress of both samples can reach more than 70%,and that of the seat ring sample is slightly higher.The original surface roughness has an effect on the ultrasonic rolling treatment:the smoother the surface is,the easier it is to obtain the desired treatment effect.In addition,the SURP treatment changes the surface compressive stress distribution,making the maximum value of residual compressive stress located on the secondary surface instead of the most surface and increasing the depth of the residual compressive stress layer.The rolling contact fatigue life of the original samples is 2.6×10~7 turns while the treated sample is 3.7×10~7 turns,showing an increment of 29.6%.The rolling contact fatigue properties of GCr15SiMn bearing steel are improved significantly by surface ultrasonic rolling treatment.