SECONDARY HARDENING OF BAINITE IN HIGH SPEED STEEL

摘要

The mechanical properties and structure of bainite and martensite after tempering m 6-5-4-2high speed steel have been investigated.It was found that the secondary hardening effect andresistance to heat softening as well as impact toughness are higher in the bainite than in themartensite.TEM observations show that the（Fe,M）₃C precipitated in the martensite aftertempering at temperature near the peak of hardness-tempering temperature curve.However,no（Fe,M）₃C but the dispersive MC and M₂C precipitated in the ferrite and austenite ofbainite after tempering at the same temperature.This indicates that the diffusion of alloy ele-ments forming carbide might exist during the process of bainite growing.