Abstract: Segregation phenomenon of 42CrMoA steel inner gear ring was characterized, and the microstructure and hardness gradient of the induction hardened layer of the inner gear ring were analyzed. The results show that the microstructure of the 42CrMo steel inner gear ring forging is uneven, with severe banded structure and compositional segregation, which leads to uneven induction hardened layer structure, and the distribution of banded structure still exists. The banded structure and compositional segregation of inner gear ring forgings have a significant impact on the hardness gradient of the induction hardened subsurface and transition zone. The hardness gradient of the induction hardened subsurface and transition zone of the inner gear ring fluctuates greatly and exhibits a steep rise and fall phenomenon.

Key words: segregation, 42CrMoA steel inner gear ring, induction hardening, microstructure, hardness gradient