Etching of Silicon Carbide Materials at Elevated Temperatures in a Nitrogen‐Based Gas

Two sintered SiC‐based materials were heat‐treated for 150 h at 1300°C in a nitrogen‐based gas (1.2% H 2 , 0.6% CO) at a total pressure of 130 Pa. Sintered SiC samples were also preoxidized and then exposed to this gas under the same conditions to evaluate the protective nature of an SiO 2 scale. In this atmosphere, SiO gas and cyanogens are predicted to form, rather than SiO 2 . Experimental studies confirmed that etching of sintered SiC occurs. Preoxidation does not provide protection from etching, because of the rapid removal of SiO 2 by H 2 as H 2 O and SiO.