Research On Surface Integrity Of Austenitic Stainless Steel Strengthened By Ultrasonic Burnishing Process

Ultrasonic surface rolling processing(USRP)is a method to achieve high efficiency surface hardening by ultrasonic vibration assisted surface rolling.USRP has obtained the comprehensive advantage of traditional rolling and traditional shot peening,so it shows excellent processing ability.Many scholars have carried out a lot of research on different workpiece materials or different process modes.However,due to the addition of high frequency excited vibration(generally greater than 20KHz),USRP is far more complex than the traditional rolling technology.Therefore,the existing research is mostly based on the analysis of the process effect,and a mature theory has not been formed on the mechanism of its processing.304 stainless steel belongs to austenitic stainless steel,because of its good mechanical properties,it is widely used in various industries.However,this material can not improve hardness by high temperature heat treatment.A series of comparative experiments were carried out using spherical roller head and arc face cylindrical roller head.The effect of USRP parameters on surface roughness,surface hardness and surface residual stress was studied by single factor experiment.The response surface experiment of Design-Expert software was used to study the primary and secondary order and optimal machining parameters on the surface roughness.The microhardness tester was used to measure the surface hardness and the hardness in the direction of thickness.The method of X ray diffraction was used to measured the surface residual stress.The results of experimental research and finite element analysis show that,the feed rate is 0.1-0.27mm/r,the back engagement is 0.2-0.3mm,the spindle speed is 120-530r/min,the processing times is 3,the better surface quality can be obtained.The better surface strengthening effect can be obtained,the phenomenon of "sticking knife" and "burning knife" can be improved by using arc face cylindrical roller head with reasonable radian.Roughness of the specimen is 0.102?m after the experiment,the improvement degree can reach 94.3%,the hardness can reach 507 HV and increase 69%.During the process of USRP,the static pressure and the high frequency excited vibration simultaneously act on the surface of the material,it makes the surface and subsurface material produce strong plastic deformation,which can form the nanoscale surface layer,effectively reduce the surface roughness of the component,improve the surface hardness,and introduce the comprehensive residual compressive stress.For different processing materials,reasonable matching of process parameters is the key to obtain good processing effect.Reasonable process parameters can significantly increase the thickness of surface hardening layer and the peak value of residual compressive stress,and obtain an ideal surface integrity inde.