Effect of Carbon and Boron on the High‐Temperature Oxidation of Silicon Carbide

Silicon carbide has good oxidation resistance, due to the formation of a protective silica layer. Although amorphous silica is an excellent oxygen barrier, it is very sensitive to impurity elements, which affect its viscosity, oxygen diffusivity, and crystallization kinetics. This paper compares the oxidation rates of CVD SiC, sintered α‐SiC, and CVD SiC‐ coated graphite in 1 atm oxygen at 1500 deg; C to determine the effects of small additions of boron and carbon. The formation of bubbles in the silica scale formed on sintered α‐SiC in oxygen between 1230° and 1550 deg; C is also discussed.