Processing, mechanical properties and oxidation behavior of TaC and HfC composites containing 15 vol% TaSi2 or MoSi2

Fully dense HfC and TaC-based composites containing 15 vol% TaSi2 or MoSi2 were produced by hot pressing at 1750-1900°C. TaSi2 enhanced the sinterability of the composites and nearly fully dense materials were obtained at lower temperatures than in the case of MoSi2-containing ones. The TaC-based composites performed better than HfC composites at room temperature, showing values of mechanical strength up to 900 MPa and a fracture toughness of 4.7 MPam1/2. However, preliminary oxidation tests carried out in air at 1600°C revealed that HfC-based composites have a superior high temperature stability compared to TaC-based materials