In-situ Characterization of High Temperature Ceramic Coating Degradation within a Replicated Aeroengine Environment using Synchrotron X-ray Diffraction

High temperature ceramic protective coatings are used to protect metallic components within a gas turbine aircraft engine. Calcium-magnesium-alumino-silicate (CMAS) particulates, found in sand, are ingested by these aero-engines and reduce the engine’s operational performance and durability. The subsequent rapid CMAS infiltration and microscale dynamic interactions between the CMAS melt and ceramic coating poses a challenge to capture the coating’s degradation with high resolution within the replicated extreme engine environment. Synchrotron X-ray diffraction was used to capture these CMAS-coating interactions and degradation-causing mechanisms on standard 7-8 wt% yttria-stabilized zirconia (YSZ) coating applied on an internally cooled hollow dogbone sample under thermal gradient conditions. Thermomechanical degradation of the YSZ coating was observed through minor compressive shifts in the average d-spacing of the tetragonal-phase associated YSZ Debye-Scherrer rings. Thermochemical degradation was observed through a decrease in tetragonal YSZ peak intensities and the formation of the monoclinic phase from yttria-lean zirconia at the surface of the coating. These results showcase the successful capture of coating degradation in a replicated aircraft flight cycle. This work establishes a basis for quantitatively assessing the mechanisms responsible for coating degradation and their severity towards premature coating failure. The findings can be used to better guide the development of targeted mitigation strategies to reduce CMAS-related damage in high temperature ceramic coatings.