Oxidation Behavior of Chemically Vapor-Deposited Silicon Carbide

The oxidation behavior of chemically vapor-deposited SiC was studied from 1,200{degree} to 1,800{degree}C. A cristobalite scale was observed on specimens heated in air to 1,500{degree}C. At 1,650{degree}C, a smooth, uniform film of amorphous silica grew. This film formed bubbles between 1,700{degree} and 1,800{degree}C, probably because of the high CO pressure at the SiC-SiO{sub 2} interface. Longer soak periods above 1,700{degree}C caused the formation of deep, narrow holes in the SiC underneath the bubbles, which is tentatively explained with a reaction of the exposed SiC with CO. Above 1,800{degree}C the coatings became destroyed within a few minutes.