高速钢中贝氏体的二次硬化特征

SECONDARY HARDENING OF BAINITE IN HIGH SPEED STEEL

研究了6-5-4-2高速钢中贝氏体和马氏体回火后的力学性能和组织结构。结果表明,贝氏体比马氏体具有更高的二次硬化效应以及抗回火稳定性和冲击韧性。透射电镜观察发现,马氏体在二次硬化峰温度范围回火时,有Fe_3C析出,而贝氏体铁素体和奥氏体中只析出弥散的MC和M_2C合金碳化物。这表明在贝氏体长大过程中存在合金元素的扩散。

The mechanical properties and structure of bainite and martensite af-ter tempered in 6-5-4-2 high speed steel have been investigated. It was found thatthe secondary hardening effect and resistance to heat softening as well as impacttoughness are higher in the bainite than in the martensite. TEM observations showthat the Fe_3C precipitated in the martensite after temrering at the temperaturenear the peak of hardening-tempering temperature curve. However, no Fe_3C but thedispersive MC and M_2C precipitated in the ferrite and austenite of bainite aftertempering at the same temperature. This shows the diffusion of alloy elements form-ing carbide must be taken during the process of bainite growing.