摘要 利用CO2轴流激光加工机对40Cr钢表面进行激光熔凝硬化处理。利用扫描电子显微镜、金相显微镜和显微硬度计研究了不同工艺下熔凝硬化层及基体的显微组织和硬度分布特征。实验表明：熔凝硬化层由熔化区、相变硬化区和热影响区组成；由表及里组织分别为极细隐晶马氏体＋少量残余奥氏体、隐晶马氏体＋碳化物＋残余奥氏体、马氏体+回火屈氏体+铁素体。硬化层最高硬度约是基体的3倍；随着扫描速度的增加表层硬度先增加后减小，当扫描速度为2.5 m·min－1时，表层硬度最大，为1097.9HK。
关键词 激光熔凝 硬化层 扫描速度 硬度
Study on Microstructure and Hardness of Laser Melting of 40Cr Steel
QIU Ling，LI Gang，QIU Xingwu
( Department of Materials Science and Engineering, Liaoning Technical University, Fuxin 123000)
Abstract 40Cr steel is molten by the axis flow CO2 laser. The hardness distribution character and microstructure of remelting hardening layer and substrate in different parameters are analyzed by scanning electron microscope, optical microscope and microhardeness tester. The experiments show that the remelting hardening layer consists of melting zone, quenching zone and heat affected zone. From surface to internal, the respective microstructures are extremely small hidden-crystal martensite and a few residual austenites, hidden-crystal martensite and carbides and residual austerite, martensite and backfire troostite and ferrite. The highest hardeness of hardening layer is as about 3 times as that of the substrate. The hardeness of surface increases first and decreases with scanning speed. When the scanning speed is 2.5 m·min-1, the highest hardeness of surface is 1097.9HK.
Keywords laser melting, hardening layer, scanning speed, hardness