Microparticle Shot Peening Process of Nitrided X210CrW12 Steel Tappet

Taking steel shot with diameter of 0.3 mm, ceramic shot with diameter of 0.1 mm and glass shot with diameter of 0.1 mm as shots, X210CrW12 steel tappet with overall nitriding was subjected to microparticle shot peening by using glass shot (shot peening intensity of 0.07 mm, measured by A test piece, the same as below), ceramic shot (shot peening intensity of 0.15 mm)+glass shot (shot peening intensity of 0.07 mm), and steel shot (shot peening intensity of 0.30 mm)+ceramic shot (shot peening intensity of 0.15 mm)+glass shot (shot peening intensity of 0.07 mm). The surface morphology, surface roughness, residual stress, residual austenite content and microhardness of the tappet after different process shot peening were studied. The results show that the shot peening had little effect on the surface roughness of nitrided X210CrW12 steel tappet, but could increase the value and depth of residual compressive stress and hardness of the surface and reduce the residual austenite content. After shot peening with a single type of glass shot, the tappet surface layer had relatively low and shallow - distributed residual compressive stress, the relatively high austenite content and the relatively low hardness. Compared with those after shot-peening with a single type of glass shot, after shot peening with ceramic shot+glass shot, the residual compressive stress and its layer depth and hardness increased, and the residual austenite content decreased. After shot peening with steel shot+ceramic shot+glass shot, the surface residual compressive stress was the largest, with the residual compressive stress on the outer circular surface and the end face of 1 180, 1 238 MPa, respectively, and the residual compressive stress layer depth was more than 200 μm; the residual austenite content was the lowest, with the austenite volume fraction on the outer circular surface and the end face of 1.34%, 2.65%, respectively; the microhardness was the highest, with the hardness on the outer circular surface and the end face of 1 036, 1 009 HV, respectively; this shot-peening process had the best strengthening effect on the tappet surface layer.