Enhanced CMAS resistance of EBCs using yttrium-silicon-iron oxide APS coating

Abstract

Environmental barrier coatings (EBCs) are proven to protect SiC-based materials against recession under water vapor at high temperatures. The state-of-the-art EBCs for CMCs consist of a Si bond coat and an ytterbium disilicate (Yb2Si2O7) top coat. However, Yb2Si2O7 is known to be susceptible to degradation by molten calcium-magnesium-aluminum-silicate (CMAS) deposits, which would compromise the durability of the SiC-based components. The magnetron sputtered multi-phase yttrium-silicon-iron oxide (YSiFe-Ox) coating has been proved its excellent CMAS resistance by enabling a quick reaction with CMAS, forming a reaction layer consisting of apatite+garnet with a minimum of consumption of the coating. This study aims to develop the multi-phase YSiFe-Ox coating using atmospheric plasma spray (APS) for the first time on top of an APS EBC system (SiC+Si+YbDS). This investigation involved the morphological, chemical, and phase characterization of YSiFe-Ox powder and its coatings. The implementation of YSiFe-Ox as a top coat layer on YbDS required a study of its crystalline behavior (HT-XRD), thermal conductivity (LFA), and coefficient of thermal expansion (dilatometry). Finally, the performance of YSiFe-Ox against CMAS corrosion was evaluated through infiltration experiments y the formation of the reaction products.