The impact of co-deposited silicon impurity on oxidation of silicon carbide coatings in the air and in steam at high temperatures

We report a study on the oxidation behaviour of stoichiometric and hyper-stoichiometric silicon carbide (SiC) with silicon impurity. In air, silica growth was parabolic at 1200 °C and 1600 °C on both SiCs but was faster on hyper-stoichiometric SiC. However, the oxidation kinetics was reversed in the steam due to the generation of a larger quantity of gaseous products and pore networks in silica on stoichiometric SiC, which resulted in easy ingress of steam and a reaction-controlled linear oxidation behaviour. In contrast, the pores in silica on hyper-stoichiometric SiC were mostly isolated, resulting in diffusion-controlled parabolic growth of the silica layer.