Microstructure, mechanical properties and oxidation behavior of short SiC fiber reinforced TaC- and HfC-based materials

TaC- and HfC-based composites containing 15 vol% short SiC fibers as reinforcing phase were produced by hot pressing at 1700-1750°C. Suitable sintering additives were selected in order to get a full densification at temperatures well-tolerated by SiC fibers. Microstructural characterization outlined a strong interaction between the carbide matrix and SiC fibers. The following properties were evaluated: Vickers hardness, fracture toughness by chevron notched beams, elastic modulus, 4-pt bending strength at room temperature and at 1200°C, linear CTE up to 1300°C in Ar, thermal conductivity up to 1900°C in Ar. Oxidation tests in air were carried out with thermogravimetric analysis up to 1500°C and in a bottom up furnace at 1600°C. TaC-based materials generally possessed higher thermo-mechanical properties compared to HfC, but lower oxidation resistance. Properties of fiber-reinforced composites were compared to those of unreinforced ones.