Effect of pressure on HTHP sintering behavior of WC-6Co hard alloy

Abstract

The high-temperature and high-pressure (HTHP) method, recognized for its effectiveness in diamond synthesis, has found extensive application in the preparation of composite materials due to its advantages, including ultrahigh hydrostatic pressure and reduced synthesis time. This study investigates the sintering behavior of WC-6Co hard alloys with grain sizes ranging from 0.2 to 0.5 µm, subjected to HTHP sintering at pressures between 1.0 and 5.0 GPa. Results indicate that increasing sintering pressure correlates with enhanced Vickers hardness. Notably, the sample sintered at 5.0 GPa exhibited a 34.5% increase in Vickers hardness (from 17.3 ± 0.4 GPa to 23.0 ± 0.5 GPa) compared to the commercial hard alloy of identical composition, outperforming WC-6Co hard alloys produced via spark plasma sintering (SPS) and low-pressure sintering methods. Additionally, at constant temperature, rising sintering pressure led to a gradual decrease in WC grain size and a blurring of grain boundaries. The sintering temperature required for HTHP was significantly lower than that of traditional methods, with the temperature at 5.0 GPa being approximately 300°C lower than conventional sintering temperatures. This study enhances the understanding of WC-Co hard alloys’ sintering behavior under HTHP conditions and offers new insights for developing high-performance WC-Co hard alloys.