Anti-oxidation properties of the mullite/yttrium silicate bilayer coating for C/SiC composites

Abstract:

Continuous carbon fibre reinforced silicon carbide (C/SiC) composites exhibit superior properties such as high strength, low density and high temperature tolerance, however, their applications are limited because of the rapid oxidation of carbon fibre and SiC matrix at elevated temperature. In this work, a mullite/yttrium silicate bilayer coating was prepared by plasma spray method as the oxidation protective coating. The morphology, composition, microstructure and adherence strength of the coating were analyzed. The efficiency of the coating against oxidation was characterized by means of heat treatment of the C/SiC composites at 1500 °C in static air for 1 hour. The structural change of the coating was studied, the weight and flexural strength of the C/SiC composites before and after the heat treatment were investigated. The results indicated that the mullite/yttrium silicate bilayer coating exhibited excellent oxidation resistance as the flexural strength of the composites retained 95.3 % of the original strength.