Effect of spraying ceramic powder pore structure on thermophysical properties of plasma-sprayed thermal barrier coatings

Abstract

Pore structure is one of the major factors influencing the failure mechanisms of thermal barrier coatings (TBCs) during high-temperature service. Powders exhibiting different pore structures have been produced using the plasma spheroidization technique. To improve the strain tolerance of an aircraft engine's hot sections, the preparation method of the TBCs material—8-wt% yttria-stabilized zirconia powders—has been continuously optimized. In this paper, the constrained effects of pores on the ceramic top coating of plasma-sprayed lamellar TBCs were investigated. Furthermore, the crystal phase structures, thermophysical properties, porosity, microstructures, and synthesis mechanism of powders and coatings were analyzed. Results revealed that the top ceramic coating, which was made from powders cooled by air and distilled water, can influence the coating porosity. Moreover, thermal insulation was substantiated by the finite element analysis method. Consequently, dense powders cooled by water can be used on the top surface in direct contact with high temperature flame flow to resist the diffusion of oxides, and the porous powder cooled by air can be applied in the middle coating to decrease the thermal conductivity. Hence, TBCs with various layers of different porosities can prolong the service life of thermal barrier coatings.