利用无氦横流CO_2激光加工机对40Cr表面进行激光相变硬化处理,并采用金相显微镜(OM)、显微硬度计、滑动摩擦磨损试验机和恒电位仪研究了不同工艺参数下硬化层的显微组织及性能.结果表明:相变硬化区的组织为细小的针状马氏体+残余奥氏体,过渡区组织为回火马氏体+残余奥氏体+铁素体+碳化物;40Cr经过激光相变硬化处理后,硬度、耐磨性和耐蚀性均显著提高. The surface of 40Cr was laser hardened with a helium-free cross-flow CO_2 laser machine. The hardness of the hardened layer was measured by metallographic microscope (OM), microhardness tester, sliding friction and wear tester and potentiostat. The microstructure and properties of the microstructure were studied.The results show that the microstructure of the phase transformation hardening zone is fine needle-shaped martensite + retained austenite, the transition zone is tempered martensite + retained austenite + ferrite + carbide ; 40Cr after laser transformation hardening, hardness, wear resistance and corrosion resistance were significantly improved.