Abstract

ZrO27Y2O3 plasma sprayed coatings were applied on high temperature Ni-based alloys precoated with a thin, dense, stabilized zirconia coating produced by Physical Vapour Deposition. This contribution concerns with the experimental and numerical analysis of residual stresses in PVD/Plasma Sprayed TBC's systems after coating deposition and after high temperature testing, such as cyclic oxidation and rapid thermal cycling. The thermal residual stress developed in the plasma sprayed top coating during spraying was simulated by using an heat transfer FEM program and an elasto-plastic biaxial stress model which calculate the stress gradients in coating/substrate system. The residual stress distributions within the TBC undergoing thermal cycling is then calculated by a biaxial stress model, taking into account the residual stress due to the deposition technique of the PVD and plasma sprayed top coating and the presence of the growing oxide interlayer. The residual stress within the upper layers of the top coating was verified experimentally by X-ray Diffraction for the as-deposited and thermal cycled samples, and the stresses within PVD bond coating and oxide interlayer were measured by microRaman spectroscopy technique in cross-sectioned samples. The measurements are in good agreement with residual stress modelled results.

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