Behavior of a sample of the ceramic material HfB2-SiC (45 vol %) in the flow of dissociated air and the analysis of the emission spectrum of the boundary layer above its surface

Ceramic HfB2-SiC samples with a silicon carbide content of 45 vol % have been obtained by spark-plasma sintering, their density and calculated porosity determined, and certain studies performed using IR spectroscopy, XRD, and other methods. The behavior of the HfB2-SiC (45 vol %) material has been studied using the VGU-4 high-frequency induction plasmatron with heating by a subsonic flow of dissociated air. It has been shown that the average temperature of the surface of the samples in the process of heating rises up to 2680-2690A degrees C, which is connected with the formation on the surface, which has the temperature of similar to 1700-1900A degrees C, of local regions with the temperature of 2600-2700A degrees C with gradually expanding areas. The total time during which the average surface temperature is higher than 2000A degrees C is similar to 30 min. The change in the composition of the gas phase above the sample surface in the course of the experiment was investigated using optical emission spectroscopy. Assumptions, which explain the changes in the concentration of boron and silicon under the action of a high-enthalpy flow, have been advanced. The elemental composition and the phase composition have been determined, and the microstructure of the surface and of various cuts of the samples have been studied.