Effect of multifunction cavitation processing on fatigue properties of carburized steel rods with smooth surface

• MFC generated high compressive residual stress on the surface of carburized steel rods.9 • MFC suppressed the formation of dents on the surface of carburized steel rods. • The residual stress relaxation behavior during fatigue tests was revealed. • The mechanism of subsurface fatigue fracture in carburized steel rods was examined. • Fatigue limit of MFC treated carburized steel rods with red rust were estimated. The effect of multifunction cavitation (MFC) processing on the fatigue properties of carburized low-alloy steel rods was examined under rotating bending. MFC was conducted for electrochemically polished steel rods pre-treated with gas carburizing and tempering. In contrast to conventional surface modification techniques that use a cavitation jet, MFC can generate compressive residual stress and suppress the formation of surface dents on the surface of carburized rods during rotation. High compressive residual stress (∼800 MPa) was generated on the surface of carburized rods by MFC because of a martensitic transformation; however, MFC did not increase the fatigue limit of the carburized rods because the compressive residual stress generated by MFC was released during fatigue tests and the surface roughness value was slightly increased by MFC due to the formation of surface pits with red rust. By contrast, the compressive residual stress for the carburized specimens without MFC increased because of the stress induced martensitic transformation during fatigue tests, which is one of the reasons why the fatigue limit of the carburized rods subjected to MFC did not increase. The fatigue limit estimation based on a modified Goodman diagram and mechanism of subsurface fatigue fracture in carburized steel rods were also examined.