Abstract
Cross-sectional optical micrograph (left) and corresponding Raman ZrO 2 -phase map (right) of CMAS-penetrated 7YSZ air-plasma sprayed thermal barrier coating. In situ Raman spectroscopy is used to understand the high-temperature interactions between air-plasma-sprayed 7 wt.% Y 2 O 3 -stabilized ZrO 2 (7YSZ) thermal barrier coatings (TBCs) and calcium-magnesium-alumino-silicate (CMAS) sand. These interactions result in the depletion of Y 3+ 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.
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