Microstructural characterization of thermal barrier coatings on high pressure turbine blades

    Authors

    Y. H. Sohn; E. Y. Lee; B. A. Nagaraj; R. R. Biederman;R. D. Sisson

    Comments

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    Abbreviated Journal Title

    Surf. Coat. Technol.

    Keywords

    scanning electron microscopy; X-ray diffraction; thermal barrier; coatings; photostimulated luminescence spectroscopy; turbine blade; failure analysis; NONDESTRUCTIVE EVALUATION; OXIDATION; ALUMINA; STRESS; PIEZOSPECTROSCOPY; Materials Science, Coatings & Films; Physics, Applied

    Abstract

    Thermal barrier coated high pressure turbine blades were characterized before and after the service by microstructural analysis and Cr3+ photostimulated luminescence piezo-spectroscopy. Thermal barrier coatings, in this study, consisted of electron beam physical vapor deposited yttria partially stabilized zirconia (YSZ; ZrO2-8 wt.% Y2O3), vapor-deposited aluminide bond coat and Ni-base superalloy. Compressive residual stress in thermally grown oxide, measured by Cr3+ photostimulated luminescence piezospectroscopy, was observed to be in the order of 2.5 similar to3.0 GPa and varied slightly as a function of substrate geometry. X-Ray diffraction and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy were utilized to investigate the microstructural development of thermal barrier coatings. The as-deposited non-equilibrium tetragonal (t') phase in the YSZ coatings was observed to decompose after the service, but the monoclinic (m) phase was only found in the YSZ coatings with concave substrate curvature on the pressure side of the HPT blade. Also, a significant sintering of ZrO2-8 wt.% Y2O3 coating after the service was observed in the microstructure. Localized spallation of YSZ occurred within the thermally grown oxide (mostly alpha -Al2O3) and within the ZrO2-8 wt.% Y2O3 coating for pressure and suction sides of the serviced high pressure turbine blade near the tip, respectively. (C) 2001 Elsevier Science B.V. All rights reserved.

    Journal Title

    Surface & Coatings Technology

    Volume

    146

    Publication Date

    1-1-2001

    Document Type

    Article; Proceedings Paper

    Language

    English

    First Page

    132

    Last Page

    139

    WOS Identifier

    WOS:000172611700020

    ISSN

    0257-8972

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