Spallation is a major failure condition experienced by thermal barrier coatings (TBCs) subjected to thermal and mechanical loads. Although evidence of spallation is substantiated and mechanistic models to describe the failure condition is prevalent in literature, the progressive nature of damage evolution leading to spallation has not been addressed adequately. In this study, the effect of holding time on damage evolution in partially stabilized zirconia TBC on Nickel-based single crystal superalloy, Rene N5, was studied. Button specimens with Electron Beam - Physical Vapor Deposition (EB-PVD) TBC coating were thermally cycled. The bond coat was PtAl. Two different thermal cycle profiles were used to assess damage development. Damage state was tracked using microscopy and thermal wave imaging technique on samples subjected to a series of thermal cycles. It was found that if the sum of hold times at the same peak temperature are kept constant for two different thermal cycles profiles, similar damage states can be obtained.

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