Abstract
This study investigated the hot corrosion behavior of various Nd2Zr2O7-yttria-stabilized zirconia (YSZ) thermal barrier coatings. Double-phase top coatings containing 25, 50, or 75 wt% Nd2Zr2O7 and functionally graded systems (FGS) comprising Nd2Zr2O7-YSZ were deposited on a substrate using an atmospheric plasma spraying method. The coatings were examined in terms of their exposure to pure Na2SO4 at 920, 970, and 1000 °C. The results indicate that in FGS, only neodymium sulfates and chromite are formed on the topcoat surface. In contrast, with dual-phase coatings containing Nd2Zr2O7 + YSZ, the diffusive decomposition of the pyrochlore Nd2Zr2O7 phase generated zirconate phases with lower neodymium contents and fluorite structure. The mechanism of pyrochlore phase decomposition is governed by basic and acidic reactions involving Na2SO4 decomposition products.
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