Durable TBCs with self-enhanced thermal insulation based on co-design on macro- and microstructure

During thermal exposure of thermal barrier coatings (TBCs), sintering causes degradation of the thermal barrier performance, as well as spallation. However, it is difficult to simultaneously enhance the thermal insulation and extend the lifetime, because the dominant factors (e.g., micropores and the macroscopic thickness) may have opposite effects on these two performances. In this study, a co-design of the macro- and microstructure is proposed to enhance multiple performance characteristics of TBCs. The microstructural design is achieved by using a co-spraying method, to form a hybrid layered coating. During thermal exposure, new pores are formed because the contractions of dense splats and loose porous nanoheaps are reversed. Consequently, the thermal barrier performance is self-enhanced by 40% with respect to that of mono-layered coatings. The macrostructural design is realized by tailoring the thickness according to the equivalent thermal insulation. As a result, the lifetime is extended by 35%. The mechanisms responsible for the simultaneously enhanced performance characteristics are discussed. This study is expected to contribute to structural tailoring of advanced TBCs with both high thermal insulation and long lifetimes.