High-temperature deformation in bulk polycrystalline hafnium carbide consolidated using spark plasma sintering

In this study, we report the three-point flexural strength and fracture toughness of monolithic hafnium carbide up to 2000 degrees C. HfC with different grain sizes was consolidated using the spark plasma sintering method. Coarsegrained monoliths showed a weak dependence on the strain rate during high-temperature tests at 1600 degrees C-2000 degrees C. In contrast, results for the ceramics with a grain size below 20 mu m indicated a positive dependence of the yield strength vs strain rate. This allowed us to identify the activation energy for high-temperature deformation in flexure as 370 kJ/mol. This level of activation energy is in satisfactory agreement with reports about the diffusion of C in hafnium carbide.