Thermomechanical Properties of Bilayer La₂Zr₂O₇ Thermal Barrier Coatings

Abstract

La₂Zr₂O₇ is a promising thermal barrier coating material due to its low thermal conductivity and superior high temperature stability. In this work, Bilayer La₂Zr₂O₇ and conventional 8 wt% yttria stabilized zirconia (8YSZ) coatings were deposited using plasma spray technique. Both single-layer La₂Zr₂O₇ and double-layer 8YSZ/La₂Zr₂O₇ coating architectures were designed. Thermal cycling and thermal shock tests were used to evaluate coatings’ thermomechanical properties. All La₂Zr₂O₇ coats were delaminated in the furnace cycle test in less than 20 cycles. This is because residual thermal stresses accumulated during thermal cycling. In the jet engine thermal shock (JETS) tests, the SCL La₂Zr₂O₇ and DCL dense 8YSZ/La₂Zr₂O₇ coatings were fully delaminated. In contrast, the DCL porous 8YSZ/La₂Zr₂O₇ coating sample only partially delaminated on the edge. This is because of the porous 8YSZ layer provides strain compliance. The findings will help to propose efficient thermal barrier coating systems.