Plasma-sprayed CeO2 overlay on YSZ thermal barrier coating: Solution for resisting molten CMAS infiltration

Abstract

In high-temperature turbine engines, the components face severe interaction with airborne particles of CaO–MgO–Al2O3–SiO2 (CMAS). Generally, YSZ based TBCs are used in these applications to protect the components. Although, the YSZ coatings enhance the properties of the components, but were found to be vulnerable to the molten CMAS penetration. To tackle this serious issue, we report the performance of an atmospheric plasma sprayed CeO2 overlay on the YSZ coating (CYSZ) against CMAS and compared it with the established YSZ coatings. The hot corrosion test with CMAS was performed on the coatings at different temperatures viz. 1200 °C, 1300 °C and 1400 °C for 4 h. The evolution of microstructure after the CMAS infiltration and the depth of penetration for both YSZ and CYSZ coatings were studied in greater details. The molten CMAS reacts with the CeO2 overlay coat in the CYSZ coatings and forms a compound phase of CeAlSiO, which acts as a sealant and prevents the further infiltration of the melted CMAS towards YSZ coating. The thermal insulation of CYSZ coatings was also found to be improved by 45% as compared to the conventional YSZ coatings. This work suggests the application of CeO2 overlayed YSZ coating for CMAS infiltration resistance as well as a good thermal insulating coating.