Effect of Vanadium Carbide on Sintering Properties and Microstructure Evolution of Powder High Speed Steel

The effects of different proportions of vanadium carbide(VC) particles instead of V powder on the density, microstructure and properties of powder metallurgy high-speed steel(PM HSS) were studied in this paper. The difference of strengthening phase composition and the mechanism of material properties under different sintering time were analyzed. The testing results show that the bonding state between elemental V and matrix is improved and the sintering densification of HSS is effectively promoted with the increasing proportion of VC particles. When holding time is 90 minutes, a large number of lath-like M2C carbides appear in the sample structure with VC particles. When holding time is extended to 120 minutes, the M2C carbides in the high-speed steel structure decompose completely, and a large number of fine M6C and MC carbides are produced. The mechanical properties of HSS can be improved by increasing the proportion of VC particles. The maximum strength of HSS is up to 2597 MPa when the proportion of VC particles is 150% and the sintering time is 120 minutes. The hardness of HSS is mainly related to density and properties of strengthening phase. The hardness of HSS prepared in this experiment is about 51~52 HRC