Thermal cyclic lifetime and oxidation behavior of air plasma sprayed CoNiCrAlY bond coats for thermal barrier coatings

    Authors

    T. Patterson; A. Leon; B. Jayaraj; J. Liu;Y. H. Sohn

    Comments

    Authors: contact us about adding a copy of your work at STARS@ucf.edu

    Abstract

    Furnace thermal cycling lifetime and microstructural degradation are reported for thermal barrier coatings (TBCs) with air plasma sprayed (APS) ZrO(2)-8 wt.%Y(2)O(3) (YSZ) and APS CoNiCrAlY bond coats. TBCs examined in this study consisted of 600 mu m-thick APS YSZ, 175 mu m-thick APS CoNiCrAlYSi and 5 mm-thick Haynes 230 superalloy substrate. Furnace thermal cycling was carried out using 1-, 10- and 50-hour thermal cycles that consisted of 10-minute heat-up to 1121 degrees C, dwell at 1121 degrees C and followed by 10-minute forced-air-quench. To further document microstructural degradation of APS CoNiCrAlY coatings, free-standing APS CoNiCrAlY coatings were produced and isothermally oxidized at 1124C for LIP to 300 h. Despite the significant internal oxidation of APS CoNiCrAlY bond coats, APS TBCs exhibited excellent thermal cycling lifetime. Microstructural evolution of TBCs with an emphasis on the development of thermally grown oxide including internal oxidation was examined by scanning electron microscopy, transmission electron microscopy (TEM) and scanning TEM. Site-specific TEM specimen was prepared by using Focus Ion Beam In-situ Lift-out technique. Extensive internal oxidation was observed including formation of Al(2)O(3), (Al,Cr)(2)O(3) and (Ni,Co)(Al, Cr)(2)O(4) identified by electron diffraction. Quantitative microscopy and a simple rule of mixture were employed to understand the excellent performance of these TBCs with APS CoNiCrAlY bond coats based on reduced thermal expansion mismatch. (C) 2008 Elsevier B.V. All rights reserved.

    Journal Title

    Surface & Coatings Technology

    Volume

    203

    Issue/Number

    5-7

    Publication Date

    1-1-2008

    Document Type

    Article

    First Page

    437

    Last Page

    441

    WOS Identifier

    WOS:000261654100009

    ISSN

    0257-8972

    Share

    COinS