Oxidation of Ceramic Materials Based on HfB 2 -SiC under the Influence of Supersonic CO 2 Jets and Additional Laser Heating.

The features of oxidation of ultra-high-temperature ceramic material HfB 2 -30 vol.%SiC modified with 1 vol.% graphene as a result of supersonic flow of dissociated CO 2 (generated with the use of high-frequency induction plasmatron), as well as under the influence of combined heating by high-speed CO 2 jets and ytterbium laser radiation, were studied for the first time. It was found that the addition of laser radiation leads to local heating of the central region from ~1750 to ~2000-2200 °C; the observed temperature difference between the central region and the periphery of ~300-550 °C did not lead to cracking and destruction of the sample. Oxidized surfaces and cross sections of HfB 2 -SiC-C G ceramics with and without laser heating were investigated using X-ray phase analysis, Raman spectroscopy and scanning electron microscopy with local elemental analysis. During oxidation by supersonic flow of dissociated CO 2 , a multilayer near-surface region similar to that formed under the influence of high-speed dissociated air flows was formed. An increase in surface temperature with the addition of laser heating from 1750-1790 to 2000-2200 °C (short term, within 2 min) led to a two to threefold increase in the thickness of the degraded near-surface area of ceramics from 165 to 380 microns. The experimental results indicate promising applications of ceramic materials based on HfB 2 -SiC as part of high-speed flying vehicles in planetary atmospheres predominantly composed of CO 2 (e.g., Venus and Mars).