Abstract: After carburizing treatment with theoretical case depths of 1.1 and 1.3 mm on BG801 gear steel, the microstructure, room temperature hardness, 500 ℃ high temperature hardness, residual stress, and 500 ℃ high temperature rotating bending fatigue of this two specimens were tested and characterized, and the main factors affecting fatigue property were analyzed. The results show that in the carburized zone, the carbide content, hardness, and residual compressive stress of the specimens with a theoretical case depth of 1.3 mm are higher than those of the specimens with a theoretical case depth of 1.1 mm. The rotating bending fatigue strength of the specimens with theoretical case depths of 1.1 and 1.3 mm at 500 ℃ is 675 and 850 MPa, respectively. In the carburized zone, the specimen with a theoretical case depth of 1.3 mm has relatively high hardness, which can suppress the initiation of microcracks to a certain extent. In addition, combined with the effect of residual stress and carbide size, the fatigue crack propagation driving energy of the specimen with a theoretical case depth of 1.3 mm is smaller than that of the specimen with a theoretical case depth of 1.1 mm under the same external applied cyclic stress, which is another reason why the fatigue property of the specimen with a theoretical case depth of 1.3 mm is better.

Key words: BG801 gear steel, carburization, hardness, residual stress, high temperature rotating bending fatigue