Al-O-N based duplex coating system for improved oxidation resistance of superalloys and NiCrAlY coatings

    Authors

    S. K. Jha; Y. H. Sohn; S. Sastri; N. Gunda;J. A. Haynes

    Comments

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    Abbreviated Journal Title

    Surf. Coat. Technol.

    Keywords

    oxidation; thermally grown oxide; coatings; residual stress; photostimulate luminescence; THERMAL BARRIER COATINGS; PHOTO-STIMULATED LUMINESCENCE; ISOTHERMAL; OXIDATION; SCALE ADHESION; ALLOYS; ALUMINA; SPALLATION; MECHANISM; PLATINUM; FAILURE; Materials Science, Coatings & Films; Physics, Applied

    Abstract

    Performance of an Al-O-N based duplex coating system (DCS) was examined in order to improve the high-temperature oxidation resistance of superalloys and the low-pressure plasma sprayed NiCrAlY coatings. The DCS (similar to5 mum thick) was deposited using pulsed DC reactive magnetron sputtering as an external coating on Rene'N5 superalloy with and without NiCrAlY coating. DCS coatings were characterized using photo-stimulated luminescence spectroscopy, optical microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy before and after high-temperature oxidation. As-deposited DCS contained varying amounts of alpha-, gamma-Al2O3 and amorphous phases depending on the chemistry and surface characteristics of the substrate. Heat treatment at 1121 degreesC (2050 degreesF) for 2 h in air facilitated complete phase transformation to equilibrium alpha-Al2O3 in the DCS. Improvement in oxidation resistance was observed or DCS specimens during 250-h oxidation at 1121 degreesC (2050 degreesF). In particular, DCS was found to be very effective as an external coating on the rough (as-sprayed) NiCrAlY surface. The superior oxidation resistance of the specimens with DCS may be attributed to the formation of slow-growing and adherent alumina scale and the prevention of Ni/Cr-rich oxide formation. (C) 2003 Elsevier B.V. All rights reserved.

    Journal Title

    Surface & Coatings Technology

    Volume

    183

    Issue/Number

    2-3

    Publication Date

    1-1-2004

    Document Type

    Article

    Language

    English

    First Page

    224

    Last Page

    232

    WOS Identifier

    WOS:000221512300014

    ISSN

    0257-8972

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