An Investigation on Volcanic Ash Infiltration Resistance of Plasma-Sprayed Indigenous Yb2Zr2O7 and Conventional YSZ Coatings at Elevated Temperatures

The modern turbines aimed to work at enhanced efficiencies demand the use of a novel high-performance thermal barrier coating (TBC) which may be susceptible to multiple failure modes. Specifically, ingestion of calcium–magnesium–alumino–silicate (CMAS) or volcanic ash (VA) at elevated temperatures induce accelerated deterioration of conventional yttria-stabilized zirconia (YSZ) TBCs. The ability to form an impervious and rapidly crystallizing rare earth-based apatite layer upon interaction with CMAS/VA salt favors the choice of rare earth zirconates (REZs) as novel TBCs. Among diverse REZs, Yb2Zr2O7 (YbZ) exhibits ideal TBC characteristics. A detailed insight into YbZ coating characteristics and performance is vitally needed to qualify these materials for TBC applications. Accordingly, in this study indigenously developed YbZ and commercial YSZ were deposited by air plasma spraying. Subsequently, the VA infiltration resistance of deposited coatings was comprehensively compared up to 1350 °C. The SEM analysis of VA-infiltrated YSZ and YbZ coatings revealed the thickness of the infiltration zone and the corresponding mechanism. YbZ coatings displayed significantly better VA infiltration resistance attributed to forming an impervious Yb-apatite-based arresting layer and pinning the further seepage of the VA salt front. Besides, VA rapidly infiltrated YSZ coatings, which failed to form an arresting layer. Overall, the study provides essential insights and thrust in developing next-generation TBCs.