Two-step hot-pressing sintering of nanocomposite WC–MgO compacts

Two-step hot-pressing sintering (TSS) was applied to consolidate nanocomposite tungsten carbide–magnesia (WC–MgO) powders. The first step sintering was employed at a higher temperature to obtain an initial high density, and the second step was held at a lower temperature by isothermal sintering for several hours to increase bulk density without significant grain growth. The experimental results showed the sintering temperature plays an important role in densification and grain growth of WC–MgO compacts. The optimum TSS regime consisted of heating at 1750 °C (1st step) and 1550 °C (2nd step), resulting in the formation of near full dense microstructure (0.99 TD) with suppressed grain growth (2.59 μm). Accordingly, the improvement on the mechanical properties, including increase in the hardness (from 16.7 to 18.4 GPa), fracture toughness (from 10.2 to 12.95 MPa m1/2) and flexural strength (from 976.6 to 1283.7 MPa), was also observed due to the grain refining and full dense bulk.