Microstructure, Strengthening Mechanism and Mechanical Properties of Vanadis 60-Ta_0.5Nb_0.5C-B₄C High-speed Steel Composite via Vacuum Sintering, Sub-zero, and Heat Treatments

Abstract

This research added different ratios of Ta₅₀Nb₅₀C and B₄C powders to Vanadis 60 high-speed steel powders, and then, sintered the Vanadis 60 composite from 1205 to 1225°C by vacuum sintering for 1 hour. Subsequently, a series of heat treatments were conducted, including quenching, sub-zero, and tempering processes. The study results show that the optimal sintering temperature and the additive ratio for Vanadis 60 composites were 1205°C and 0.975 mass% Ta₅₀Nb₅₀C-0.025 mass% B₄C powders, respectively. Simultaneously, the transverse rupture strength (TRS) value was 2328.2±0.90.7 MPa and the hardness value was 81.3±0.1 HRA, respectively. In particular, when the optimally sintered Vanadis 60 composite underwent sub-zero plus heat treatments, the TRS and hardness values obviously increased to 2456.6±76.3 MPa and 85.7±0.3 HRA, respectively. Finally, the TEM and EBSD study results also revealed that various MC and M₆C-type carbides significantly appeared in the Vanadis 60 composite after vacuum sintering and sub-zero plus heat treatments.