Thermodynamics of Hot Corrosion of SiC Fiber/CAS Matrix Composites

An investigation was undertaken to determine the potential benefits of utilizing a thermodynamic data base as a tool in characterizing the hot corrosion process of a ceramic matrix composite (CMC). the most stable products were determined by an iterative process which calculated the Gibbs free energy of the system. the computations considered all of the elements and potential compounds which pertained to the hot corrosion of a calcium aluminosilicate (CAS) system. Calcium Aluminosilicate was examined both as a monolithic and as a composite material with silicon carbide (SiC) reinforcement. the hot corrosion exposure consisted of a sodium sulfate (Na2SO4) coated specimen at 900°C in air for varying lengths of time. the results from the experimental study were compared to thermodynamic predictions for the system. Both the theoretical model and experimental results supported similar findings when comparing the monolithic material. However, the complexity of the hot corrosion process is enhanced with the introduction of SiC fibers, and the thermodynamic computations did not accurately predict the product phases after exposure