Dynamic oxidation mechanism of SiC fiber reinforced SiC matrix composite in high-enthalpy plasmas

摘要

A plasma wind tunnel was utilized to explore the dynamic oxidation mechanism of SiC fiber reinforced SiC matrix composite in high-enthalpy plasmas. The results suggest the occurrences of active and passive oxidations on SiC fiber/matrix with atomic oxygen at 900-1600 degrees C and 1-6 kPa. Increasing plasma pressure could retard the active oxidation and promote the passive oxidation. Severe corrosion of SiC fibers due to active oxidation is highlighted. The as-formed SiO2 layers cannot fully seal the open porosities and the interfacial gaps formed by oxidation of pyrocarbon interphases. This led to penetration of oxidized species and failure of fiber bundles directly exposed to heat flows. In addition, the spatial heat flux and temperature distributions were not homogeneous on the oxidized surface, which triggered early 'temperature jump' at approximate to 1600 degrees C (approximate to 4.5 kPa) and severe localized ablation. If sealing the composite surface with SiC coating, the ablation resistance was significantly improved.