Oxidation of an Environmental Barrier Coated Ceramic Matrix Composite in a Combustion Environment

Oxidation is a key failure mechanism for environmental barrier coatings (EBCs) deposited on ceramic matrix composites (CMCs). Current generation EBC/CMC systems incorporate a silicon (Si) bond coat between the CMC substrate and the EBC topcoat. Oxidation occurs at the interface between the Si bond coat and the EBC topcoat due to diffusion of water vapor and oxygen creating a thermally grown silica (SiO2) scale. As the SiO2 scale increases in thickness, the adhesion strength of the EBC topcoat becomes compromised leading to delamination and spallation. This work investigates the oxidation kinetics of an EBC/CMC system with an Si bond coat utilizing a natural gas/oxygen (NG/O2) burner rig at atmospheric pressure. An oxidation model is presented to predict the oxidation kinetics of the EBC/CMC system. The model exhibits good agreement with experimental data obtained in the NG/O2 rig up to 250 hours after which the oxidation kinetics deviate from the predicted behavior. A reason for the observed change in oxidation kinetics is presented along with directions for future work.