Investigation of the strengthening mechanism and corrosion behaviours of Vanadis 4 extra tool steel adding ZrC-TiC powders through vacuum sintering, and sub-zero and heat treatments

In the present research, different ratios of zirconium carbide (ZrC) and titanium carbide (TiC) powders were added to Vanadis 4 Extra (V4 Extra) steel powders. The composite powders (V4 Extra-ZrC-TiC) utilised vacuum sintering at 1275, 1300, 1325 and 1350 degrees C for 1 h, respectively. The experimental results showed that good mechanical properties were obtained by the addition of 1.8 mass% ZrC and 1.2 mass% TiC (Z1.8T1.2) sintered at 1350 degrees C for 1 h. Meanwhile, the apparent porosity was decreased to 0.02 vol.-%, and the transverse rupture strength (TRS) and hardness reached 1872 +/- 24 MPa and 82.5 HRA, respectively. When optimally sintered V4 Extra composites (Z1.8T1.2) underwent a series of heat treatments, the TRS value was obviously enhanced to 2007 +/- 17 MPa after quenching, and sub-zero and tempering heat treatments. Moreover, the sub-zero and heat treatments improved the distribution of MC carbides, which effectively enhanced the strength of sintered V4 Extra composites.