Effect of Ultra-high Temperature Heat Treatment on Microstructures of W/ZrC Cermets Fabricated by Different Routes

W/ZrC cermets were fabricated by displacive compensation of porosity (DCP) and hot pressing (HP) separately, and then they were heat treated at 2600 °C for 1 h. Microstructure changes of W/ZrC cermets before and after heat treatment was investigated. Results show that both of two W/ZrC cermets have an increase in open porosity, a linear expansion and mass loss after the heat treatment. Annealed DCP-derived W/ZrC cermets are still composed of dispersive W phases and continuous ZrC phases, but residual WC, W2C and Zr-Cu alloy are gone; instead, a large increase of pores and a sharp reduction of W phases appear. While a new phase of W2C forms in annealed HP-derived W/ZrC cermets, W grains have a tendency to congregate together to form a big agglomerate phase.