Thermal Conductivity, Phase Stability, and Oxidation Resistance of Y₃Al₅O₁₂ (YAG)/Y₂O₃–ZrO₂ (YSZ) Thermal-Barrier Coatings

Author： Su Y. J. Trice R. W. Faber K. T. Wang H. Porter W. D.

Publisher： Springer Publishing Company

ISSN： 0030-770X

Source： Oxidation of Metals, Vol.61, Iss.3-4, 2004-04, pp. : 253-271

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Abstract

This paper describes a new multilayer TBC that incorporates a 10 μm-thick oxygen barrier layer of yttrium–aluminum garnet (YAG) into a typical YSZ TBC system. The thermal conductivity of as-sprayed YAG/YSZ coatings was reduced due to excessive porosity and amorphous areas in the YAG layer. After long-term heat treatments, the conductivity of the multilayer was unaffected by the presence of YAG. Sintering and recrystallization of the amorphous YAG regions occurred during high-temperature heat treatments. While YAG itself possesses excellent phase stability, its presence also improved the phase stability of zirconia near the YAG/YSZ interface, inhibiting the outward diffusion of yttrium from high-yttria t-ZrO₂ The YAG layer reduced the NiCoCrAlY bond-coat oxidation rate by a factor of three during isothermalfurnace tests conducted at 1200° C.