Microstructure and Thermal Cycling Behavior of Air Plasma-Sprayed YSZ/LaMgAl11O19 Composite Coatings

Abstract

Yttria-stabilized zirconia (YSZ) based composite coatings with the addition of LaMgAl11O19 (LaMA) as the secondary phase, were prepared by air plasma spraying in order to improve the performances of the traditional YSZ coating. Results indicate that the newly developed composite coating shows increased vertical crack density with the enhancement of the LaMA content during thermal cycling process, which results in increased strain tolerance and service lifetime. However, such composite coatings about 200 μm thick, exhibit inferior thermal cycling lifetimes with respect to the typical YSZ coating for surface temperatures above 1400 °C. The presence of amorphous LaMA phase in the composite coating results in increased thermal conductivity and a relative thin top coat leading to a reduced thermal insulation efficiency. These are believed to be responsible for the premature degradation of bond coat and final top coat spallation failure. Such an investigation gives useful guidelines to develop advanced composite coatings based on YSZ/LaMA systems.