Mechanical properties and oxidation resistance of plasma-sprayed multilayered Al2O3/ZrO2 thermal barrier coatings

Coupled with functionally graded materials (FGM) concept, Al2O3 was proposed as a potential candidate as an interlayer to improve the oxidation resistance of thermal barrier coating (TBC) system due to its low oxygen diffusivity. Plasma spray process was utilized to produce Al2O3/ZrO2 functionally graded thermal barrier coating (FG-TBC). This article discusses physical and mechanical properties, thermal behavior, and high-temperature oxidation resistance of the FG-TBC system as compared to a typical duplex TBC system. The results showed that the proposed FG systems exhibit superior mechanical properties and oxidation resistance at the expense of a slightly lower thermal-insulating effect. Thin interlayer is preferred in order to minimize the detrimental effect of phase transformation of γ-Al2O3 to α-Al2O3 that results in tensile residual stresses at the interface.