深冷处理对低碳高合金马氏体轴承钢力学性能及组织的影响

利用洛氏硬度计、X射线衍射仪、扫描电子显微镜及透射电子显微镜等研究了低碳高合金马氏体轴承钢深冷处理后的硬度变化及组织演化。结果表明:深冷处理促使部分残留奥氏体转变为马氏体,导致深冷处理后实验钢的硬度较淬火态硬度有所升高。经深冷处理后实验钢在0~100 h回火过程中的硬度均比未深冷处理实验钢的硬度高。深冷处理促使钢中碳原子偏聚并在回火过程中以碳化物的形式析出,与未经深冷处理的实验钢相比,经深冷处理的实验钢回火后马氏体基体中的含碳量更低,表明实验钢经深冷处理后在回火过程中析出更多的碳化物。透射电镜分析表明,实验钢在回火过程中析出的大量弥散分布的纳米级M2C和M6C型碳化物是实验钢长时间回火后保持高硬度的主要原因。

Effect of Deep Cryogenic Treatment on Mechanical Property and Microstructure of a Low Carbon High Alloy Martensitic Bearing Steel during Tempering

The hardness and microstructure evolution of a low carbon and high alloy martensite bearing steel after deep cryogenic treatment were studied by means of Rockwell hardness tester, X-ray diffractometer, and scanning electron microscope and transmission electron microscope. The results show that the deep cryogenic treatment promotes the transformation of retained austenite to martensite, which leads to an increase in the hardness after quenching. In addition, the hardness of the steel subjected to deep cryogenic treatment was higher than that of the non-cryogenically treated one during tempering. The deep cryogenic treatment causes the carbon atoms in the steel to segregate and precipitate as carbides during the tempering process. Compared with the steel without deep cryogenic treatment, the carbon content in the martensite matrix of the steel subjected to deep cryogenic treatment was lower after tempering, which indicated that more carbides were precipitated in the deep cryogenic treated steel during the tempering process. According to the results of transmission electron microscope images, a large number of nano-sized M₂C and M₆C carbides precipitated from the martensite matrix during tempering, which may be the main reason for the maintenance of high hardness of the steel after longtime tempering.