Preparation, Microstructure and Thermal Conductivity of Plasma-Sprayed (Y0.8Gd0.2)3Al5O12 Coatings

Abstract

Garnet-type rare earth aluminate compounds are one class of promising potential candidate materials for thermal barrier coatings (TBCs). In this paper, (Y0.8Gd0.2)3Al5O12 (GYAG) coatings are fabricated by air plasma spraying, with the microstructure, high-temperature phase stability, and thermal conductivity investigated. The results showed that the as-deposited GYAG coating was relatively dense, and contained garnet-type (Y0.8Gd0.2)3Al5O12 phase and a small amount of (Y,Gd)AlO3 and amorphous phases. The crystallized GYAG coating exhibited good phase stability from room temperature to 1450 °C. The coating had the lowest thermal conductivity of 1.17 W·m−1·K−1 at 800 °C, approximately 15% lower than that of the yttria-stabilized zirconia (YSZ) coating. After heat treatment at 1100 °C, the coating became denser with some fine grain precipitation, and formed a number of transverse and longitudinal cracks.