Effects of Heat Treatment on Microstructure and Hardness of Spray Formed M42 Steel

The effects of quenching temperature and tempering temperature on the microstructure and hardness of the spray formed M42 steel were investigated.The results show that with the increase of quenching temperature,the hardness of the steel initially increases and then decreases when the quenching temperature becomes higher than 1180℃,meanwhile,the amount of carbide in the microstructure decreases.Martensite coarsens,and the amount of residual austenite increases.With the increase of tempering temperature,the hardness firstly increases up to a peak value at 550℃ and then decreases.The increase of tempering temperature makes more disperse carbides precipitate from the martensite gradually and grow up,and the martensite and part of the residual austensite transform into tempered martensite.