Structure and properties of heat-treated and coated W-Mo-V + Si + Nb high-speed steels

This paper presents the results of investigations regarding the phase transformations occurring during the heat treatment of W-Mo-V + Si + Nb high-speed steels. It was found that investigated steels demonstrate their maximum secondary hardness, about 66 HRC, in connection with the precipitation of M₄C₃ carbides in tempered martensite after austenitizing at 1240°C and tempering at 540-570°C. The paper presents also results of investigations regarding the erosion resistance of TiN and Ti(C,N) PVD coatings deposited on the investigated steels. TiN and Ti(C,N) coatings deposited in the PVD process yield, respectively, three and seven times greater erosion resistance of the steel surface and demonstrate good adhesion to the investigated steels forming the substrate. Quantitative metallography methods as well as mass loss and created craters 3-D measurements were employed to evaluate the erosion resistance of the investigated coatings. It was found that the surface topography influences the erosion resistance of PVD vacuum arc method coatings. The investigated coatings are not affected by the type of the substrate high-speed steels.