Microstructure and Mechanical Properties of ZrB(2)–HfC Ceramics Influenced by HfC Addition

ZrB(2)–HfC ceramics have been fabricated using the liquid phase sintering technique at a sintering temperature as low as 1750 °C through the addition of Ni. The effects of HfC addition on the microstructure and mechanical properties of ZrB(2)–based ceramics have been investigated. These ceramics were composed of ZrB(2), HfC, Ni, and a small amount of possible (Zr, Hf)B(2) solid solution. Small HfC grains were distributed among ZrB(2) grain boundaries. These small grains could improve the density of ZrB(2)–based ceramics and play a pinning role. With HfC content increasing from 10 wt % to 30 wt %, more HfC grains were distributed among ZrB(2) grain boundaries, leading to weaker interface bonding among HfC grains; the relative density and Vickers hardness increased, and flexural strength and fracture toughness decreased. The weak interface bonding for 20 and 30 wt % HfC contents was the main cause of the decrease in both flexural strength and fracture toughness.