In situ TEM observation of the microstructure characteristics of the vacuum sintering, sub-zero and heat treatments of Vanadis 23 high-speed steel by adding Cr3C2–TaC–TiC powders

ABSTRACT This research added different ratios of chromium carbides, tantalum carbide, and titanium carbide powders to Vanadis 23 high-speed steel powders. The composite powders utilised vacuum sintering at 1230, 1245, 1260, and 1275°C for 1 h, respectively, and the experimental results show that good mechanical properties were obtained by the addition of 0.6 mass% Cr3C2–0.2 mass% TaC–0.2 mass% TiC sintered at 1245°C for 1 h. Meanwhile, the apparent porosity was decreased to 0.23%, and the transverse rupture strength and hardness reached 2470.7 MPa and 78.5 HRA, respectively. When optimally sintered Vanadis 23 composites (0.2 T) underwent a series of heat treatments, the transverse rupture strength and hardness values were obviously enhanced to 2693.6 MPa and 84.0 HRA after quenching, and sub-zero and tempering treatments. The EBSD and TEM results confirm that the MC, M 6C, M 7C3, and M 23C6-type carbides appeared in the 0.2 T specimen after vacuum sintering and sub-zero heat treatments.