Effect On The Surface Properties Of GCr15 By Ultrasonic Rolling

Bearings are one of the most important key components of various types of equipment,widely used in the major equipment fields such as mining machinery,precision machine tools,and metallurgical equipment field.The working environment of bearing steel parts is extremely poor,and higher demands are placed on its surface properties.By comparing the characteristics of various surface deformation strengthening techniques,ultrasonic rolling surface strengthening is suppose to be an ideal emerging surface deformation strengthening technology.In this paper,ultrasonic rolling strengthening technology is applied to GCr15 bearing steel.The surface properties of roughness,surface microhardness,metallographic microstructure,residual stress and resistance and the mechanics properties of corrosiveness,friction,wear and fatigue crack growth with different reductions are compared and analyzed.The results show that surface roughness of the sample is reduced by 3 grades,the lowest is Ra=0.063 ? m,the microhardness is increased from 592.2HV to 839.11 HV,which is increased by 41.69%.It improves with the increase of the reduction;after ultrasonic strengthening,the surface grains are remarkably refined,the cementite is granular and evenly distributed,and the thickness of the grain refinement layer becomes thicker with the increase of the reduction.The residual stress of the surface layer is changed from tensile stress to compressive stress.After ultrasonic rolling strengthening,the residual stress of the surface is-425.7MPa and the topest is-560.6MPa.Within a certain range,with the increase of the reduction,the residual stress is improved;the corrosion resistance of the ultrasonic rolling is significantly improved compared with the finish turning,and the ultrasonic sample is placed in the natural environment,and the surface is almost the same after three months.The friction coefficient of the ultrasonic rolling strengthening specimens are obviously reduced,and the wear amounts were lower than the original specimens;The fatigue crack growth rate da/d N was significantly reduced.