Abstract—Ultrahightemperature composite materials HfB2SiC containing 10, 15, and 20 vol % SiC were prepared by spark plasma sintering. The behavior of the samples prepared under longterm exposure to subsonic dissociated airstreams of a highfrequency 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 tem peratures 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 Xray powder diffraction enabled us to study the microstruc ture and composition of a structurally complex oxidized layer.

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