Heat-treatment of spray forming Nb-contained M3: 2 high speed steel

In order to explore the fitted heat treatment process of spray forming Nb-contained M3: 2 high speed steel,the effects of quenching and tempering temperatures on phase component,microstructure and hardness of the steel were investigated by XRD,SEM and hardness teast. The results show that the as-qunched microstructrue of the steel consists of martensite,retained austenite and carbides. The amount of carbides decreases with the increasing quenching temperatures. The hardness increases initially and then decreases with quenching temperature increasing. The second hardening of the steel is not found after quenching at low temperature and tempering processes. After quenching at 1220 ℃ and tempering at 560 ℃,the better hardness of the steel is 66. 7 HRC.