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.

Spheroidal pearlite microstructure was obtained via spheroidizing annealing of CL70 heavy-duty wheel steel. CL70 specimens with lamellar pearlite and spheroidal pearlite microstructures were separately subjected to dry friction pure rolling tests with U75V rail steel on a rolling friction and wear testing machine under identical parameters. Wear loss was measured using the weighing method, and the microstructure and hardness variations on the running surfaces of the two types of specimens were observed and analyzed by means of a scanning electron microscope equipped with an electron backscatter diffraction (EBSD) attachment and a microhardness tester. The results indicate that the wear resistance of spheroidal pearlite microstructure is inferior to that of lamellar pearlite microstructure. The wear and strengthening mechanisms of the two microstructures differ significantly. Lamellar pearlite is dominated by fatigue wear: it undergoes plastic deformation, with grains continuously refined from fibrous to nanocrystalline, and dislocations accumulate continuously to achieve favorable strengthening effects. Spheroidal pearlite is dominated by adhesive wear, where only ferrite and a small amount of cementite deform and fragment; the increase in hardness mainly stems from dislocation accumulation around cementite particles, leading to poor hardening performance.