Molten calcium-magnesium-aluminum-silicate (CMAS) particles cause significant degradation of thermal barrier coatings (TBCs) in aero-engines. One way to protect TBCs against CMAS attack is through the application of a sacrificial topcoat. In this work, Al2O3 coatings were deposited on top of EB-PVD 7wt% YSZ layers via suspension thermal spraying using an aqueous Al2O3 suspension. Spray parameters were varied in order to obtain Al2O3 layers with two different microstructures and porosity levels. The coating systems were evaluated by means of CMAS infiltration testing at 1250 °C. It was found that the porosity and morphology of Al2O3 strongly influence CMAS infiltration and the formation of reaction products and that CMAS mitigation is a function of coating morphology and the speed at which Al2O3 reacts with CMAS deposits.

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