轴承用8Cr4Mo4V钢真空气淬及等温盐浴淬火后的性能对比分析

通过显微组织观察及性能测定,对轴承用8Cr4Mo4V钢真空气淬及等温盐浴淬火处理后的性能进行了对比分析。结果表明,8Cr4Mo4V钢真空气淬后得到马氏体组织,等温盐浴淬火后得到马氏体+贝氏体混合组织。真空气淬后钢的晶界有碳化物析出,腐蚀后晶界特征明显,而等温盐浴淬火后晶界碳化物析出量少,钢的晶界特征不明显。再经回火处理后,钢中析出大量碳化物,与真空气淬相比,等温盐浴淬火钢中析出的碳化物在尺寸和数量上都更大。钢的硬度和耐磨性测试表明,等温盐浴淬火钢的硬度为61.78 HRC,而真空气淬钢的硬度为60.28 HRC,硬度提高了1.5 HRC,等温盐浴淬火钢的摩擦磨损性能比真空气淬钢高。与真空气淬相比,等温盐浴淬火处理后钢的力学性能提升,室温拉伸强度提高了164 MPa,高温拉伸强度提高了50 MPa,冲击吸收能量提高了46.9%,旋转弯曲疲劳强度极限由860 MPa提高至1050 MPa,提高了22%。

Comparative analysis on properties of 8Cr4Mo4V steel for bearing after vacuum gas quenching and isothermal salt bath quenching

Properties of 8Cr4Mo4V steel for bearing after vacuum gas quenching and isothermal salt bath quenching were comparatively analyzed by microstructure observation and property test. The results show that the martensite in the 8Cr4Mo4V steel is obtained after vacuum quenching, while the mixed microstructure of martensite and bainite is obtained after isothermal salt bath quenching. There is carbide precipitation at the grain boundary of vacuum quenched steel, and the grain boundary characteristics are obviously shown after chemical etching. However, the amount of carbide precipitation at the grain boundary of isothermal salt bath quenched steel is less, and the grain boundary characteristics of the steel are not obvious. Then after tempering treatment, a large number of carbides precipitate in the steels, and that in the steel isothermal salt bath quenched are larger in size and quantity than that of vacuum quenched. The test results of hardness and wear resistance show that the hardness of the isothermal salt bath quenched steel is 61.78 HRC, higher by 1.5 HRC than that of the vacuum quenched steel (60.28 HRC). The friction and wear resistance of the isothermal salt bath quenched steel is higher than that of the vacuum quenched. Compared with that of vacuum quenching, the mechanical properties of the steel after isothermal salt bath quenching are better: the tensile strength is higher by 164 MPa and 50 MPa respectively at room temperature and at high temperature, the impact absorbed energy is increased by 46.9%, and the rotary bending fatigue strength is increased by 22%, from 860 MPa to 1050 MPa.