Plasma sprayed gadolinium zirconate thermal barrier coatings that are resistant to damage by molten Ca-Mg-Al-silicate glass

Air plasma sprayed (APS) Gd ₂Zr ₂O ₇ thermal barrier coatings (TBCs) are found to be highly effective in resisting high-temperature (1200°C) penetration of molten Ca-Mg-Al-silicate (CMAS) glass deposit for prolonged durations (up to 1week). In contrast, conventional APS 7YSZ TBCs are found to be fully penetrated by the molten CMAS glass under the same testing conditions. This resistance is attributed to the formation of a sealing layer made of crystalline Ca-apatite phase (based on Ca ₂Gd ₈(SiO ₄) ₆O ₂) as a result of the high-temperature chemical interactions between the APS Gd ₂Zr ₂O ₇ TBC and the CMAS glass. The resistance to penetration of molten silicate deposits offered by Gd ₂Zr ₂O ₇ composition TBCs is relatively insensitive to both the type of molten silicate deposits (CMAS sand, volcanic ash, coal fly ash) and the TBC microstructure (APS, EB-PVD).