Abstract: Effect of induction hardening treatment on sectional microstructure and residual stress of the 42CrMo steel crankshaft connecting rod journal was analyzed by means of OM, SEM, X-ray stress analysis and mechanical property test. The effect of quenching power on morphology, microstructure and mechanical properties of the hardened layer was discussed. The results show that the 42CrMo steel crankshaft connecting rod journal is composed of three parts: the hardened layer, the transition layer and the matrix. The microstructure of the hardened layer is uniform and fine martensite, the transition layer is a mixture of martensite and tempered sorbite, and the matrix is tempered sorbite. After induction hardening, the surface residual stress of the 42CrMo steel crankshaft connecting rod journal changes from tensile stress to compressive stress. With the increase of induction hardening power, the depth of hardened layer increases and the microstructure is refined continuously. When the quenching power is 2500 W, the microstructure is the most uniform and fine, the surface hardness reaches 751.3 HV0.1, and the wear resistance is greatly improved. However, too high induction hardening power will lead to microstructure coarsening. When the induction hardening power is 2600 W, the microstructure is coarsened and the hardness is reduced.

Key words: 42CrMo steel crankshaft connecting rod journal, induction hardening, microstructure, mechanical properties