In situ Raman spectroscopy studies of high-temperature degradation of thermal barrier coatings by molten silicate deposits

In situ Raman spectroscopy is used to understand the high-temperature interactions between air-plasma-sprayed 7 wt.% Y2O3-stabilized ZrO2 (7YSZ) thermal barrier coatings (TBCs) and calcium-magnesium-alumino-silicate (CMAS) sand. These interactions result in the depletion of Y3+ in the YSZ grains. During cooling the Y-depleted YSZ grains transform to the monoclinic phase starting at ∼600 °C. The significant volume expansion associated with this phase transformation could play a role in determining the thermomechanical failure of CMAS-penetrated 7YSZ TBCs during thermal cycling.

Cross-sectional optical micrograph (left) and corresponding Raman ZrO2-phase map (right) of CMAS-penetrated 7YSZ air-plasma sprayed thermal barrier coating.Figure optionsDownload high-quality image (60 K)Download as PowerPoint slide