Phase field modeling of V2O5 hot corrosion kinetics in thermal barrier coatings

Abstract

It has been found that the use of low grade fuels in land-based turbines in Saudi Arabia results in the hot corrosion (Type-I) degradation due to the diffusion of a molten salt, V2O5, into top coat of thermal barrier coatings. Consequently, volumetric expansion of the coating occurs due to the tetragonal-to-monoclinic transformation of zirconia in the planar reaction zone near the surface of the coating. In the present study, a phase field model that estimates the kinetics of microstructure evolution during the corrosion process is estimated at 900°C, and close agreement between numerical and experimental results is achieved. The transformation-induced stresses are predicted by coupling the phase transformation with elasticity. The governing equations are implemented numerically using the finite element method. The result shows that very high compressive stresses that are developed within the coating cross section eventually cause the spallation failure of the coating.