Abstract: Surface stress distribution of tooth root of the carburized and quenched 18CrNiMo7-6 steel gear with modulus of 20 mm after different shot peening treatment was tested and compared with the specimen without shot peening. The results show that the top layer of the tooth root of the carburized and quenched 18CrNiMo7-6 steel gear before and after shot peening is all in compressive stress state, which increases first and then decreases from surface to inside. The residual stress at top layer of the tooth root without shot peening is about -75 MPa, and the maximum residual stress is about -250 MPa at the subsurface of 110-120 μm. Shot peening treatment can increase the surface compressive stress of tooth root by 4-5 times, the residual stress at top layer is about -350 MPa, and the maximum residual stress of -900 to -1000 MPa is beneath the subsurface of 90 to 110 μm.

Key words: 18CrNiMo7-6 steel, carburizing and quenching, shot peening, stress