Citation:
Xin Wang, Alan Atkinson, Laura Chirivì, John R. Nicholls, Evolution of stress and morphology in thermal barrier coatings, Surface and Coatings Technology, Volume 204, Issue 23, 25 August 2010, Pages 3851–3857.
Abstract:
Residual stress in the thermally grown oxide (TGO) in thermal barrier coatings
(TBCs) was measured by photoluminescence piezospectroscopy (PLPS) and stress
maps created to track local stress changes as a function of thermal cycling. The
local stress images were observed to be correlated with morphological features
on the metal surface that were purposely introduced during specimen preparation.
Local stress relaxation and morphological evolution with thermal cycling were
studied using the stress maps combined by post-mortem SEM examination. It was
found that the morphology in the specimen having an initial polished surface was
quite stable, while that in the specimen with a rough surface was unstable. The
average residual stress in the specimen with the unstable morphology decreased
with thermal cycling and it eventually failed along TGO/YSZ interface. The
specimen with stable morphology maintained a high TGO stress throughout the
thermal cycling process and failed along TGO/bond coat interface. The rough
surface was also found to give rise to the formation of transition alumina
(theta-Al2O3) in the TGO which was correlated with a reduced TGO stress. (C)
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