Influence of fabricating processes on microstructure and properties of high speed steel containing Nb

The high-speed steels W6Mo5Cr4V2 containing Nb(M2-Nb) were produced by traditional casting and spray-forming,respectively.According to the relationship between room temperature hardness and microstructure of the two forged alloys after heat treatment,the optimum quenching and tempering temperatures were obtained for the two high-speed steels.Then,the elevated temperature properties of the two kinds of high-speed steels were analyzed in optimum heat treatment conditions.The results show that the microstructure of as-deposited billet of the spray-forming M2-Nb high speed steel is composed of fine equiaxed grains,and the carbides are uniformly distributed along grain boundaries.After quenching at 1180 ℃ and tempering at 560 ℃ for three times,the hardness of forged spray-forming M2-Nb high speed steel is 2.6 HRC higher than that of the forged as-cast high speed steel under its optimum heat-treatment condition.In addition,the red-hardness and high temperature hardness of the forged spray-forming high speed steel are also higher than that of the forged as-cast one.