Effect of the Surface Relief of HfB2-SiC Ceramic Materials on Their High-Temperature Oxidation

Samples of an ultra-high-temperature HfB2-30 vol % SiC ceramic material with an SiC crystallite size of 50 nm have been fabricated by hot pressing of an HfB2-(SiO2-C) composite powder synthesized through a sol-gel route. It has been found that the selected hot-pressing conditions (1800 degrees C, 15 min, 30 MPa) ensure complete conversion of silica to silicon carbide and afford a material with a relative density of 96.9%. The effect of a relief applied to the sample surface in the form of ring grooves with a depth of <0.5 mm on the oxidation of the material exposed to a subsonic dissociated air flow-temperature distribution over the surface, elemental and phase composition, and microstructure-has been studied using a high-frequency induction plasmatron.