Corrosion of SiC/SiC composite in Na2SO4 vapor environments from 1000 to 1500 °C

Corrosion of a three-dimensional SiC/SiC composite with a CVD Sic coating was investigated in environments containing Na2SO4 vapor, oxygen and water vapor at temperatures from 1000 to 1500 degrees C. The corrosion behavior was greatly related to temperature. Below 1200 degrees C, the composite exhibited excellent resistance to corrosion, and then the residual flexural strength nearly kept the same value as the as-received strength. From 1200 to 1300 degrees C, the interaction of oxidation and corrosion led to a rapid weight gain. Above 1300 degrees C, weight loss due to volatilization and sublimation of Si(OH)(4) and Na2O center dot xSiO(2) on the surface increased continuously. At the same time, the gas release resulted in the formation of bubbles/corrosion pits and the maximum diameters of them increased with an increasing temperature. Additionally, above 1200 degrees C, with an increasing temperature, the residual flexural strength of the composite decreased greatly. (c) 2005 Elsevier Ltd. All rights reserved.