Wear Behavior and Microstructure Evolution of Spheroidized Annealed Heavy Load Wheel Steel CL70

Spheroidized pearlite structure was obtained by spheroidizing annealing of heavy load wheel steel CL70. The steel CL70 with either lamellar pearlite microstructure or spherical pearlite microstructure, was subjected to dry friction pure rolling test on a rolling friction and wear tester against rail steel U75V. The wear was determined by the mass loss. Scanning electron microscope (electron backscattered image) and the micro-hardness tester were used to observe and analyze the microstructure evolution and hardness variation of the rolling surfaces of steel CL70. The results show that the wear performance of steel CL70 with spheroidal pearlitic microstructure was poorer than that of steel CL 70 with lamellar pearlitic structure. The wear mechanism and strengthening mechanism of the two alloys were different. For the one with lamellar pearlitic microstructure, wear mechanism was mainly fatigue wear by plastic deformation and subsequent grain refinement (fiber structure at first and then nanocrystal), strengthening effect was attributed by accumulation of dislocations. Adhesive wear was observed for the one with spherical pearlitic structure. Deformation and fragmentation of ferrite and cementite were identified. The increase in hardness was mainly due to the concentration of dislocations around the cementite particles, and therefore the hardening effect was poor.