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The effect of a high thermal gradient on sintering and stiffening in the top coat of a thermal barrier coating (TBC) system

Tsipas, S.A., Golosnoy, I.O., Damani, R. and Clyne, T.W. (2004) The effect of a high thermal gradient on sintering and stiffening in the top coat of a thermal barrier coating (TBC) system Journal of Thermal Spray Technology, 13, (3), pp. 370-376. (doi:10.1361/10599630420380).

Record type: Article


Superalloy substrates coated with plasma-sprayed CoNiCrAlY bond coats and yttria-stabilized zirconia top coats (TCs) have been subjected to a high heat flux under a controlled atmosphere. The sintering exhibited by the TC under these conditions has been studied and compared with the behavior observed during isothermal heating. Sintering has been characterized by (a) microstructural examinations, (b) dilatometry, in both the in-plane and through-thickness directions, and (c) stiffness measurements, using both cantilever bending and nanoindentation. A numerical model has been used to explore the stress state under isothermal and thermal gradient conditions. Dilatometry data indicate significant linear contractions during holding at elevated temperatures, particularly in the through-thickness direction. This is largely attributed to microstructural changes associated with sintering, with any volume changes due to phase transformations making relatively small contributions. Sintering proceeds faster at higher temperatures but is retarded by the presence of tensile stresses (from differential thermal expansion between the coating and substrate) within the TC. Thus, it occurs preferentially near the free surface of the TC under gradient conditions, not only due to the higher temperature, but also because the in-plane stress is more compressive in that region.

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Published date: September 2004
Keywords: high thermal gradient, sintering, stiffness, thermal barrier coatings, thermal conductivity
Organisations: EEE


Local EPrints ID: 265202
ISSN: 1059-9630
PURE UUID: 7025dbe1-883a-4d67-812a-c585e10402d1

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Date deposited: 26 Feb 2008 12:57
Last modified: 18 Jul 2017 07:28

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Author: S.A. Tsipas
Author: I.O. Golosnoy
Author: R. Damani
Author: T.W. Clyne

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