An experimental technique to evaluate the effective thermal conductivity of Y2O3 stabilized ZrO2 coatings

Abstract

An experimental device was set up to determine thermal resistance and conductivity of 8% yttria-stabilized zirconia deposited by plasma spray method on cylindrical specimen. In this experimental setup, coated surface of the sample was exposed to a high temperature environment and inner metal surface was cooled by flowing air, simulating actual gas turbine applications. Overall heat resistance at the outside surface of thermal barrier coating was adopted to assess thermal advantage due to the thermal barrier coating deposited on air-cooled cylindrical specimen. 28% less heat was extracted at 1000°C by applying 1.2 mm thick thermal barrier coating. Temperatures of the outside surface of the coated samples increased with increasing coating thickness with respect to the same furnace temperature since the sample with thicker coating was less thermally conductive and retarded heat transfer. The overall heat resistances of samples between the outside surface of sample and the flowing air inside the sample assembly were estimated. Then, the thermal conductivity of coating could be determined from the difference of overall thermal resistances of two selected samples with varying coating thickness.