Oxidation Resistance and Mechanical Enhancement of Ferro-Silicon Nitride on Silica Sol Bonded SiC Castable

Abstract

Silica sol bonded SiC castable have obvious advantages of slag resistance and thermal stress damage resistance. However, they are not widely used due to their weak oxidation resistance at high temperature. Ferro-silicon nitride is added to improve the oxidation resistance of SiC castable. The efficiency of SiC castable in the presence of different contents of ferro-silicon nitride was evaluated through sintered properties, isothermal oxidation behaviors and microstructural analysis. The results show that sample with 5wt% ferro-silicon nitride possessed good mechanical behavior after heat treatment due to its acceleration for the formation of SiC whiskers. At 1500 °C, Isothermal oxdation curve indicated that the oxidation progress performed two-stage model controlled by chemical reaction at the earlier period and diffusion at the later period. Sample with 5wt% ferro-silicon nitride present faster oxidation rate (kc) at the earlier stage versus the contrast sample (0.025 mg·cm-2·min-1 vs 0.087 mg·cm-2·min-1), and slower oxidation rate (kd) at the later stage (0.145 mg·cm-2·min-1 vs 0.137 mg·cm-2·min-1). After 470 min isothermal oxidation test, the weigh gain of sample with 0 wt% ferro-silicon nitride exceeded the sample with 5wt% ferro-silicon nitride.