Numerical Simulation of Thermal Barrier Coatings with Volcanic Ash Penetration

Abstract

CMAS attack is known to be occurred owing to the deposition of volcanic ash on the surface of thermal barrier coating (TBC) at a high-temperature environment. The serious problem is TBC spallation resulting from the penetration of molten volcanic ash into the porous microstructure of TBC. The penetration induces inner stress and phase transformation, which leads to TBC spallation. In this study, the diffusional equation for expressing the infiltrating process of the molten ash into the porous structure of TBC and the associated constitutive equation involving phase transformation are formulated. The simulation results are compared with the cross-sectional SEM observation for the volcanic-ash-deposited TBC sample exposed at a high-temperature. As a result, it was found that tensile stress was widely distributed in penetration area of molten volcanic ash in TBC. Through the comparison with experimental result, it can be stated that the crack in TBC was initiated and propagated due to this tensile stress.