HfB2-SiC (10–20 vol %) ceramic materials: Manufacture and behavior under long-term exposure to dissociated air streams

Ultra-high-temperature composite materials HfB2-SiC containing 10, 15, and 20 vol % SiC were prepared by spark plasma sintering. The behavior of the samples prepared under long-term exposure to subsonic dissociated airstreams of a high-frequency induction plasmatron was studied. The total test time per sample was 35–42 min. Under certain exposure conditions (which were dependent on the composition of a sample), some regions of the sample were found to experience a rapid increase in temperature up to 2700°C. These regions enlarged over time, so that most of the surface area of the sample experienced exposure to temperatures of up to 2500–2700°C for 19–38 min, while the rest of the surface had a temperature of up to 1800–1900°C during almost the entire duration of the experiment. The joint use of optical microscopy, scanning electron microscopy (with EDX analysis), and X-ray powder diffraction enabled us to study the microstructure and composition of a structurally complex oxidized layer.