Thermal diffusivity of TBC layers of RE₂Zr₂O ₇ type

The paper presents the results of basic thermal properties of thermal barrier coatings on the base of rare earth zirconate of type Gd ₂Zr₂O₇, deposited by the air plasma spraying (APS) method. Measurements of thermal diffusivity with the laser-flash method were performed within the temperature range of 25°C-1100°C with two and ten hours of annealing. The measurements were performed on the single-layer (AMS 5599 alloy), double-layer (AMS 5599 alloy + NiCrAlY interlayer) and three-layer samples (AMS 5599 alloy + NiCrAlY interlayer + ceramic layer of RE ₂Zr₂O₇). By using the NETZSCH Proteus software and the results for the single-layer sample, thermal diffusivity of the interlayer itself was determined by means of the double-layer model. A similar method was used to determine the thermal diffusivity of the ceramic layer. The obtained results showed lower thermal diffusivity and thermal conductivity for the new type of coatings in comparison with the standard zirconium concerning TBCs. Those results are slightly different compared with the results obtained for the initial powders, which indicates a crucial role of the ceramic layer microstructure (architecture of cracks and porosity).