Effects of ultrasonic surface rolling processing on the surface microstructure and properties of a tungsten heavy alloy

Ultrasonic surface rolling processing (USRP) is an effective method of improving the surface properties of materials without changing their internal structure. In this work, the effects of USRP on the surface structure and properties of an R2M tungsten alloy for die-casting molds were studied, and the microstructure, surface roughness, microhardness and surface residual stress of the specimens were analyzed. The results show that the surface roughness of the specimens decreases obviously after USRP. The compressive residual stress of the specimens first increases and then decreases with increasing static pressure, whereas it decreases with increasing spindle speed. The optimal surface properties of the R2M tungsten alloy were obtained after USRP at a static pressure of 0.10 MPa and spindle speed of 180 r min(-1); the microstructure was the most uniform, and the surface roughness, microhardness, and surface compressive residual stress were 0.09 mu m, 524 HV, and -706 MPa, respectively.