Electrophoretically deposited alumina as protective overlay for thermal barrier coatings against CMAS degradation

    Authors

    P. Mohan; B. Yao; T. Patterson;Y. H. Sohn

    Comments

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    Abbreviated Journal Title

    Surf. Coat. Technol.

    Keywords

    Thermal barrier coating; CMAS degradation; Overlay barrier coating; Electrophoretic deposition; Environmental degradation; TEMPERATURE; Materials Science, Coatings & Films; Physics, Applied

    Abstract

    TBCs are increasingly susceptible to degradation by airborne CMAS deposits. In order to mitigate the CMAS attack, we fabricated a dense, crack-free alumina overlay for TBCs by electrophoretic deposition (EPD) technique. Overlay coatings of controlled thickness were successfully fabricated for YSZ TBCs, by EPD followed by controlled sintering at 1200 degrees C. YSZ with alumina overlay coatings were tested for CMAS attack at 1300 degrees C. Detailed examination of microstructural changes and phase evolution in CMAS tested specimens was performed by X-ray diffraction and electron microscopy. Dense alumina overlay produced by EPD was found to physically suppress the infiltration of CMAS. Furthermore, CMAS was found to crystallize into anorthite (CaAl(2)Si(2)O(8)) and MgAl(2)O(4) spinel by chemically interacting with EPID alpha-Al(2)O(3). A shift in CMAS glass composition to a crystallizable Al-rich glass composition promoted the formation of anorthite platelets (CaAl(2)Si(2)O(8)) and localized enrichment of Mg promoted the formation of MgAl(2)O(4) spinel. EPD alumina overlay on commercial-production TBCs retained its adhesion and structural integrity after 20cycles of 1-hour furnace thermal cycle test at 1100 degrees C. (C) 2009 Elsevier B.V. All rights reserved.

    Journal Title

    Surface & Coatings Technology

    Volume

    204

    Issue/Number

    6-7

    Publication Date

    1-1-2009

    Document Type

    Article; Proceedings Paper

    Language

    English

    First Page

    797

    Last Page

    801

    WOS Identifier

    WOS:000272859500011

    ISSN

    0257-8972

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