High Temperature Aging Behavior and Order-Disorder Transformation of Plasma Sprayed Sm₂Zr₂O₇ Coatings

Rare-earth zirconates with a pyrochlore structure have attracted great attention for potential application in thermal barrier coatings to further improve the performance and durability of gas turbines. In present work, the Sm₂Zr₂O₇ coating was deposited by air plasma spraying technology, and its microstructure and phase composition were examined. The as-sprayed Sm₂Zr₂O₇ coating exhibited anion-disordered while cation-ordered fluorite-type structure. Degree of ordering was considerable enhanced after high temperature aging, and transformed to ordered pyrochlore-type structure after thermal aging at temperatures above 1200 ºC. The typical lamellar structure for the as-sprayed Sm₂Zr₂O₇ coating gradually decreased with increasing thermal aging temperature, which was caused by microcrack healing at high temperatures.