Direct fabrication and performance of ultrahigh vanadium powder metallurgy high speed steels

Near-full densified (>99.2%) powder metallurgy high-speed steels (PM HSS) enhanced by ultrahigh content of vanadium additions (0–40 wt.%) were successfully prepared using a novel direct fabrication technology (DFT) involving ball-mixing and vacuum activated sintering. Uniformly distributed carbides, low impurity content, fewer alloying limitations, and near-net shaping were achieved. Variations in microstructure, phase, chemical homogeneity, mechanical properties, and scratch abrasive resistance of both sintered and heat-treated ultrahigh vanadium steels were studied. Microscratch tester, scanning electron microscope (SEM), electron probe micro-analyzer (EPMA), X-ray diffraction, and differential scanning calorimetric (DSC) analysis were used. Only the MC carbide (V 8 C 7 structure) was detected in the steels containing more than 5 wt.% vanadium. The overall chemical homogeneity, and local vanadium-lack and tungsten-lack areas, were detected in MC carbide. Dispersedly introduced vanadium additions linearly improve the Vickers hardness, scratch hardness, and scratch wear resistance of steels, but impose negative effects on bend strength. The steels containing 10–30 wt.% vanadium show superior integrated performance. Knowledge about vanadium in steel will be enriched.