Surface degradation of ultrahigh-temperature ceramics based on HfB2–30vol%SiC in subsonic nitrogen plasma flow

The behavior of ultrahigh-temperature ceramics of the composition (HfB 2 –30vol%SiC)-2vol%C(graphene) under the influence of subsonic flow of dissociated nitrogen has been studied. It is shown that at the chosen exposure parameters, at the steady-state surface temperature ~ 2170–2190°С, surface degradation of the material is observed to a depth of about 10–20 μm. This is expressed by the fact that, as a result of the ongoing reactions, silicon carbide is removed from the near surface zone and HfB 2 is transformed into the hexagonal phase of low hafnium nitride Hf 3 N 2 . It is noted that the phase composition of the surface in this case is significantly different from that observed after impact on ceramics based on HfB 2 -SiC supersonic flow of air plasma. The data obtained may be useful for evaluating the prospects of using ceramic composites for the exploration of space bodies with atmospheres of high nitrogen content. • The behavior of UHTC based on HfB 2 –30vol%SiC in a subsonic nitrogen plasma flow has been studied. • It is shown that the selected conditions set the surface temperature to ~2170–2190°С. • The peculiarities of changes in phase composition and surface microstructure are revealed. • It was found that SiC removal and Hf 3 N 2 formation occurred on the surface. • It is shown that the sample degradation depth over 600 s of exposure is predominantly ≤10–20 μm.