球化退火态重载车轮钢CL70磨损性能及组织演化

对CL70重载车轮钢进行球化退火获得球状珠光体组织. 将组织为片状珠光体和球状珠光体的CL70分别与U75V钢轨钢在滚动摩擦磨损试验机上以相同参数进行干摩擦纯滚动试验. 使用称重法测量磨损量、利用带电子背散射衍射附件的扫描电子显微镜及显微硬度计对两种组织形态的试样运行表面进行组织及硬度变化情况的观察与分析. 结果表明:球状珠光体组织磨损性能不及片状珠光体组织. 二者的磨损机制和强化机制不同，片状珠光体组织以疲劳磨损为主，通过塑性变形和晶粒不断细化至纤维状再到纳米晶，位错不断累积并达到良好的强化效果. 球状珠光体组织以黏着磨损为主，只有铁素体和少量渗碳体变形和碎化，硬度提升主要来自于渗碳体颗粒周围的位错集中，硬化效果较差. 

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.