Microstructure, retained austenite, and mechanical properties evaluation of Vanadis 60-HfC-Ta0.6Nb0.4C steel matrix composite by vacuum sintering, sub-zero, and heat treatments

Abstract

This study added different ratios of HfC and Ta60Nb40C powders to Vanadis 60 high-speed steel powders, and then, the Vanadis 60 composite was sintered from 1215 to 1260 °C by vacuum sintering for 1 h. The experimental results reveal that the optimal sintering temperature and the additive amount for Vanadis 60 composites were 1230 °C and 0.5 mass% HfC-0.5 mass% Ta60Nb40C powders, respectively. Moreover, the optimally sintered Vanadis 60 composite possessed an apparent porosity of 0.37%, the transverse rupture strength (TRS) value was 2212.1 MPa, and the hardness value was 80.3 HRA. In addition, it underwent sub-zero plus heat treatments, where the TRS and hardness values were significantly enhanced to 2451.7 MPa and 86.0 HRA, respectively, after quenching, sub-zero, and tempering treatments. The research results of TEM and EBSD show that MC, M6C, M7C3, and M23C6-type carbides obviously appeared in the composite after vacuum sintering, heat treatment, and sub-zero treatments.