Atmospheric Plasma Spraying of High Melting Temperature Complex Perovskites for TBC Application

 

           High melting materials have always been very attractive candidates for materials development in thermal barrier coating (TBC) applications. Among these materials, complex perovskites with Ba(Mg_1/3Ta_2/3)O₃ and La(Al_1/4Mg_1/2T_1/4)O₃ compositions, having melting temperatures of ~3000ºC are among the most refractory oxides ever known to science.   Their bulk properties show low values of thermal conductivity (~2W/m-K) and high coefficient of thermal expansion (~11/K), which are promising for TBC applications. These materials have been developed and deposited in TBC systems by atmospheric plasma spraying. Spray parameters were optimized and actual in-flight particle temperatures were also recorded. The as-prayed coatings were then characterized in terms of phase composition and stability, morphology and porosity. Finally, the thermal cycling lifetime of the TBC systems at high temperatures were investigated. It has been found that the nature of the starting materials plays a critical role during atmospheric plasma spraying, which ultimately affects the lifetime performance of the TBC.