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

The features of oxidation of ultra-high-temperature ceramic material HfB[sub.2]-30 vol.%SiC modified with 1 vol.% graphene as a result of supersonic flow of dissociated CO[sub.2] (generated with the use of high-frequency induction plasmatron), as well as under the influence of combined heating by high-speed CO[sub.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[sub.2]-SiC-C[sub.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[sub.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[sub.2]-SiC as part of high-speed flying vehicles in planetary atmospheres predominantly composed of CO[sub.2] (e.g., Venus and Mars).