Oxidation damage mechanisms of the CMC/Si/YDS system at high temperature: Kinetic, morphological and mechanical characterization

Abstract

Environmental Barrier Coating (EBC) systems are currently applied on silicon carbides (SiC) ceramic matrix composites (CMC) to protect them from the harsh environmental conditions of aircraft engines. During the thermal cycles of engines, various physicochemical and thermomechanical mechanisms damage the coating. These damages lead to the loss of the protection efficiency of the EBC up to its spallation. This work is focused on two main types of damages: the bond coat oxidation, which causes local stresses induced by volume variations with the formation of oxide scale, and the thermomechanical stresses across this layered system: CMC/bond coat/oxide/EBC. Oxidation tests (moist air) were carried out on polished Si samples and coated samples to discuss the effect of interface roughness and the presence of the top coat on kinetics and the stress generation.