U74钢轨表面激光淬火工艺及其对耐磨性的影响

本文研究了U74钢轨表面激光淬火工艺及其对表面耐磨性能的影响。激光淬硬层分为表面过热区、均匀相变区和过渡区。淬硬层深度约为0.5-0.8mm，单道淬火宽度约4mm，表面硬度可达Hv850-Hv1000，淬硬层组织为高碳马氏体，细晶混合马氏体和少量奥氏体。激光淬火造成的组织细化和大量高碳马氏体的形成是硬度提高的主要原因。在扫描速度为6mm/秒，离焦量60mm的条件下，U74钢轨表面激光淬火的最佳功率约为1.8kW。在该功率下，可以获得最高硬度、最大硬化层深度和最佳能量利用系数。摩擦学试验表明，经过激光淬火，钢轨表面的耐磨性能有了明显提高。

Laser quenching of U74 steel and its effect on wear resistance

Laser quenching of U74 steel and its effect on the wear resistance are studied. The surface hardness is increased from Hv300 to Hv850 -Hv1000 with thickness of 0.5-0.8mm after laser quenching. The hardened layer consists of three sub- layers:overheated layer, uniform phase transformation layer and transition layer. A mixed structure of martensite and retained austenite was obtained in the surface layer. The elevation of the hardness is attributed to the refining of the crystalline and the formation of the high?carbon martensite during laser quenching. With scanning speed of v = 6mm/s and off-focus length 60mm, the optimal laser power for U74 steel quenching is about 1. 8kW. The maximum hardness, largest thickness of the hardened layer and optimal energy utilization coefficient could be obtained under this laser power. The surface wear resistance is enhanced after laser quenching.