High temperature oxidation of two- and three-dimensional hafnium carbide and silicon carbide coatings

International audienceThe difficulty in using above 2000°C in an oxidizing atmosphere C/C composites as structural components is their poor life time. The solution proposed here consisted in combining two refractory carbides, hafnium and silicon carbides, in coating with a complex architecture, named a three dimensional coating, over a C/C substrate. Such a coating protects the C/C composite at 2050°C under air. The oxidation of the coating leads to the formation of a Si x O y Hf z hafnium-containing silicate liquid, combined with HfO 2(s). This liquid limits oxygen diffusion more than pure SiO 2 does, so it is a better protection against oxidation. Furthermore, HfO 2(s) acts as a grip holding Si x O y Hf z in place. From these results, an oxidation mechanism is proposed and discussed