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

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, and 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.