Effect of Alumina Content on the Oxidation of Hot‐Pressed Silicon Carbide

The oxidation behavior at 1370°C of dense SiC, hot‐pressed with the aid of Al 2 O 3 , has been investigated as a function of Al 2 O 3 content. Increasing amounts of the Al 2 O 3 hot‐pressing aid increased the oxidation rate. Observations of the oxide surface show that a glassy phase (indicating formation of a liquid at the oxidation temperature) containing Si, Al, Fe, and K forms over the residual Al 2 O 3 in the hot‐pressed material. It is suggested that the oxygen transport through an impure aluminosilicate liquid is faster than that through a pure SiO 2 scale, thus causing an increased oxidation rate.