织构化热处理对钢轨钢耐磨性和寿命的影响

Effect of Surface Texturing Treatment on the Wear Resistance and Service Life of Rail Steel

目的减小钢轨钢表面因离散硬化产生的硬化区与基材边界处的硬度突变,从而消除磨损过程中硬化区与基材边界处因材质不连续而产生的早期碎裂现象,进一步提高钢轨钢的耐磨性和寿命。方法提出了一种基于层流等离子体束离散硬化的表面织构化热处理方法。与之前的离散圆点状硬化不同,通过调节等离子体束在试样表面的运动速度,改变试样表面的加热时间,在硬化区与基材之间人为地附加了一个过渡区。为了揭示织构化热处理对钢轨钢滚滑性能的影响,在摩擦磨损试验机上进行了磨损试验。磨损后的试样经切割、打磨、抛光和腐蚀,在光学显微镜和扫描电子显微镜下进行了观察,以分析试样的磨损过程和织构化热处理提高试样耐磨性的机理。结果由于附加过渡区的存在,相变区的一边被拉长,形状变为泪滴状。硬化区到基材的硬度变化率由3500 HV/mm降低至200 HV/mm,在圆点状硬化中可观察到的硬度突变消失。同时,在磨损实验中,泪滴状硬化试样的磨损量较圆点状硬化试样降低了27%,边界碎裂消失。结论具有附加过渡区的试样比圆点状硬化的试样具有更好的耐磨性和抗塑性变形能力,该方法对提高钢轨钢的使用寿命具有一定的应用前景。

To reduce the hardness difference between the hardened zone and the substrate and then, eliminate the early spalling caused by material discontinuity at the boundary and improve the wear resistance and the life of rail steel, a surface texturing treatment based on laminar plasma jet discrete hardening was proposed. Different from the previous discrete hardening, an additional transitional zone was created between the hardened zone and the substrate by adjusting the velocity of the plasma jet on the specimen surface to change the heating time of the specimen surface. To reveal the effect of texturing treatment on the rail steel, the wear test was carried out on a friction and wear test machine. The worn specimens were cut, polished, etched. Then these were observed under an optical microscope and scanning electron microscope to analyze the wear behavior and the mechanism of improving the wear resistance of the specimens by surface texturing treatment. Because of the transitional zone, one side of the phase transformation zone is stretched into a teardrop shape. The rate of hardness change from the hardened zone to the substrate decreased from 3500 HV/mm to 200 HV/mm and the abrupt hardness boundary disappeared. In the wear test, the wear of the specimen by teardrop hardening was 27% lower than that of the specimen by the circular point hardening, and the spalling disappeared. It is concluded that this method has a certain application prospect to improve the service life of rail steel.