Surface Degradation of Ceramic Material Based on the ZrB2–HfB2–SiC System under the Influence of a Subsonic Flow of Dissociated Nitrogen Containing 5 mol % CO2

Ultra-high-temperature ceramics based on zirconium and hafnium diborides are of great scientific and technical interest, as they can be very promising, including as components of descent vehicles for space exploration. To study the behavior of these ceramics under the influence of high-speed flows of dissociated gases of complex composition and to determine the effect of modifying the ZrB2–HfB2–SiC system with carbon nanotubes, the process of surface degradation under the influence of a subsonic flow of dissociated nitrogen containing 5 mol % CO2 was examined. Despite the relatively low CO2 content in the nitrogen plasma, the surface oxidation process dominated the conversion of the initial ZrB2/HfB2 into solid solutions based on monocarbonitrides of these metals. In this case, it was noted that a protective layer of silicate glass does not form on the surface, unlike similar materials under the influence of subsonic flows of dissociated air at temperatures <1750–1800°C.