Effects of (Ti, W)C Addition on the Microstructure and Mechanical Properties of Ultrafine WC–Co Tool Materials Prepared by Spark Plasma Sintering

In this study, powder mixtures containing (Ti, W)C additions (10, 20, 30 and 40 wt%) were prepared and then consolidated at 1200, 1250, 1300 and 1350 °C by spark plasma sintering. The effect of (Ti, W)C additions on the microstructure and mechanical properties of ultrafine WC–Co materials was investigated. The results demonstrate that the (Ti, W)C not only retards the sintering densification but also increases the porosity of sintered samples. The increasing sintering temperature is beneficial to the densification but results in the grain coarsening and the dissolution of W in (Ti, W)C. Moreover, there are no (Ti, W)C grains with obvious core/rim structure in the microstructure. With the (Ti, W)C increasing from 10 to 20 wt%, the hardness increases and fracture toughness changes hardly. However, the hardness and fracture toughness decrease slightly as the (Ti, W)C further increases. The transgranular fracture of (Ti, W)C phases is responsible for the slight reduction in fracture toughness. The sample with 20 wt% (Ti, W)C has high hardness and fracture toughness (HV: 21.3 GPa, KIC: 9.8 MPa m1/2).