Abstract: Effect of sub-zero treatment at -120°C. and -150°C on properties of high speed steel W6Mo5Cr4V2 is studied by means of hardness and wear resistance tests. The microstructure and wear morphology are analyzed by means of scanning electron microscope (SEM). It is concluded that the hardness and wear resistance of the high speed steel increase by sub-zero treatment. With the sub-zero temperature decrease, the performance of high speed steel improves significantly. The performance of cycle sub-zero treatment sample is better than a long time sub-zero treatment sample. After sub-zero treatment for 3 times 1 h at -150 °C ,the high speed steel can obtain the optimal comprehensive performance. The results show that the significant performance improvement of high speed steel is attributed to the transformation of retained austenite to martensite in the samples after sub-zero treatment. At the same time, the wear resistance performance improved is attributed to that a large amount of carbides precipitate from high speed steel work as the rigid particles during the friction and wear process. There is super-cooling degree that continuously exists during the cycle cryogenic treatment process. The transformation of retained austenite to martensite and the tiny carbides precipitated from matrix martemsite can be promoted by super-cooling each cycle to improve the performance of the high speed steel.

摘要： 对经-120℃和-150℃深冷工艺处理的W6Mo5Cr4V2高速钢进行了硬度及摩擦磨损性能测试,并用扫描电镜分析了其显微组织与磨损形貌。深冷处理使高速钢硬度和耐磨性能得到提高。随深冷温度的降低,性能改善明显,经循环深冷处理试样的性能均好于一次长时间深冷处理试样,-150℃温度下经3次1 h深冷处理试样的性能最优。结果表明,高速钢性能改善的主要原因是深冷处理可促进试样中残余奥氏体向马氏体转变,同时,高速钢组织中析出的大量碳化物在摩擦磨损过程中作为硬质颗粒可提高耐磨性能。循环深冷处理过程中过冷度一直存在,每次循环过程都可促进残余奥氏体转变为马氏体,促进基体马氏体上析出细小的碳化物,从而提高高速钢的性能。

关键词: 深冷工艺, 高速钢, 循环深冷处理, 硬度, 耐磨性能