Influence of Atmosphere on Thermal Conductivity of Thermal Barrier Coatings

Abstract

The thermal conductivity of the ceramic top-coat (TC) for thermal barrier coatings was examined in various atmospheres in order to clarify the influence of the atmosphere on its thermal conductivity. Some kinds of TCs with different microstructures were prepared by plasma sprayings. The thermal conductivity was determined from the thermal diffusivity, the specific heat capacity and the bulk density. The thermal diffusivity was measured in air, argon, nitrogen and vacuum. It was found that the thermal conductivity in any TCs depends strongly on the atmosphere. Since the plasma sprayed TC has open pores which are connected to its surface, the gas of the atmosphere can be penetrate into the open pores. The thermal conductivity of the gas affects that of the TC. Therefore, the atmosphere should be considered as an important factor for measuring the thermal conductivity of the plasma sprayed TC.[Keywords: thermal barrier coatings, thermal conductivity, atmosphere, microstructure, plasma spraying] * 首都大学東京 大学院理工学研究科機械工学専攻, 〒192-0397 八王子市南大沢 1-1.