Dominant effect of oriented 2D pores on heat flux in lamellar structured thermal barrier coatings

Thermal barrier coatings (TBCs) provide thermal insulation to metallic components served at high temperatures. The oriented 2D pores are primarily responsible for the efficient prevention of heat flux. Thus, structural design of TBCs with higher thermal insulation requires clear understanding on the thermal conduction inside coatings. Up to now, previous analytical models to investigate the heat conduction were mainly based on the concept of thermal contact resistance. However, the related assumption was far away from the real coating microstructure. In this study, the intrinsic structural characteristics of plasma sprayed TBCs were firstly investigated. Subsequently, an analytical model based on the structural features was developed to understand the dominant effect of oriented 2D pores on heat flux inside the coatings. Results showed that the insulative ratio of 2D pores dominantly determine the effective prevention of heat flux. Moreover, effects of the microstructural parameters, including splat thickness, bonding ratio and unit size, on the total thermal resistance was discussed. Overall, the understanding of the dominant effect of 2D pores would make it possible to design new TBCs with high performance in future applications.