Processing of ZrC-TiC Composites by SPS
ZrC – TiC composites containing 20 wt.% TiC, along with and without 0.2 wt.% graphite were prepared by spark plasma sintering (SPS) at temperatures between 1600 - 1900 °C for 10 min under pressure up to 100 MPa. The addition of free carbon tends to reduce the appearance of tertiary phases in the microstructure according to scanning electron microscope (SEM) images. However, free carbon also reduced the mechanical properties of Vickers’ hardness and fracture toughness of the composites. SPS data showed when pressure was increased to 100 MPa, evident grain growth started to occur at a temperature as low as 1600 °C resulting in relative density > 100%. Samples produced at 1600 °C, but with maximum allowable pressure according to the SPS machine, yielded samples with greater hardness and fracture toughness compared to samples produced at 1900 °C.