2018 Volume 59 Issue 10 Pages 1596-1602
In this study, different amounts of vanadium carbide (VC) powders (1, 3 and 5 mass%) are mixed and added to Vanadis 4 steel powders. The composite powders are sintered at 1225, 1250, and 1275°C for 1 h, respectively. The experimental results show that the optimal sintering temperature for Vanadis 4-VC composites is 1250°C. The Vanadis 4 specimens with a 3% VC addition possess the highest transverse rupture strength (TRS) value of 1953.3 MPa, as well as the highest polarization resistance (1.84 × 104 Ω·cm2), while with a 1% VC addition obtain the highest hardness value of 82.9 HRA after sintering at 1250°C. Furthermore, a microstructural evaluation reveals that the round-shaped M23C6 carbides uniformly located on the grain boundaries are gradually increased as VC particles are added, and the fine particle-shaped (V, Fe) carbides are uniformly dispersed in the matrix. After heat treatment, the VC carbides decompose and re-precipitate refined M23C6 and (Cr, Fe) carbides around the grain boundaries and within the grains, which results in dispersion strengthening and precipitation hardening. The results clearly show that heat treatment effectively improves the microstructure and strengthens the matrix of the Vanadis 4-VC composites.
