High-temperature properties of liquid-phase-sintered α-SiC

We have characterized the high-temperature subcritical crack growth and oxidation resistance of a liquid-phase-sintered (LPS) SiC with 20% volume fraction yttrium aluminum garnet (YAG) second phase. Constant stress-rate testing in air in the temperature range 1100–1300°C yielded a crack growth exponent, n=38.9±9.9 and an activation energy, Qscg=(380±237) kJ mol−1. Oxidation followed parabolic kinetics in the temperature range 1100–1300°C with an activation energy, Qox=(246±33) kJ mol−1. At 1350°C reaction between the growing oxide layer and the YAG second phase produced a low-melting eutectic, resulting in accelerated oxidation. Below 1100°C, oxidation rates were also anomalously high for reasons we do not understand. In the intermediate temperature range, both the oxidation and subcritical crack growth resistance compare favorably with other silicon carbides.