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

doi:10.13251/j.issn.0254-6051.2022.07.002

Abstract

Abstract: 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.

Key words: high temperature bearing steel, vacuum gas quenching, isothermal salt bath quenching, carbide, mechanical properties

CLC Number:

Tong Rui, Yu Xingfu, Liu Yongbao, Xia Yunzhi, Su Yong, Jin Yingli. Comparative analysis on properties of 8Cr4Mo4V steel for bearing after vacuum gas quenching and isothermal salt bath quenching[J]. Heat Treatment of Metals, 2022, 47(7): 9-14.

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