表面淬火工艺对大型轴承套圈用42CrMo钢淬硬层的影响

Effect of surface quenching process on hardened layer of 42CrMo steel for large bearing ring

对42CrMo中碳轴承钢进行不同温度中频感应加热及淬火介质的表面淬火处理,并使用洛氏硬度计、光学显微镜、扫描电镜及透射电镜对淬火试样不同区域组织及硬度进行测试分析。结果表明,经表面淬火处理后,按硬度由大到小试样可分为淬硬区、过渡区及基体3个区域,随着表面淬火加热温度的升高,表面淬硬层的深度增加,并且相对于水淬,油淬的淬硬层深度显著减少。组织分析表明,水淬淬硬区组织均为马氏体,而油淬工艺由于冷速较慢,淬硬层组织为马氏体+铁素体组织,不同表面淬火工艺条件下过渡区组织均为马氏体+回火索氏体,基体为原始调质态的回火索氏体。淬硬区、过渡区及基体的组织差异导致不同区域的硬度差异。实际应用中应根据所需淬硬层深度选择合适的水淬加热温度。

42 CrMo medium carbon bearing steel was surface quenched with different temperatures and quenching mediums. Then the microstructure and hardness of different regions of the quenched specimens were tested and analyzed by means of Rockwell hardness tester, metallographic microscope, scanning electron microscope and transmission electron microscope. The results show that after surface quenching treatment, according to the hardness from large to small, the specimen can be divided into three different regions: hardened zone, transition zone and base material. The depth of surface hardened layer increases with the increase of surface quenching heating temperature, and that of oil quenching is significantly reduced compared with that of water quenching. Microstructure analysis shows that the microstructure in the water quenching hardened zones are all martensite, while the oil quenching has a slow cooling rate, which causes that the hardened zone is martensitic+ferrite. The transition zones under different surface quenching conditions are all martensite+tempering sorbite. Furthermore, the base material is the tempered sorbite in the original quenched and tempered state. Differences in the microstructure of hardened zone, transition zone and base material leads to differences in hardness in different regions. In practical applications, appropriate heating temperature for water quenching should be selected according to the required depth of the hardened layer.