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Proceedings Paper

The prediction of lifetime failure of thermal barrier coatings using piezospectroscopic techniques
Author(s): Christopher J. Chunnilall; James P. Banks; Guofeng Chen; Jessica Y. Cheung; Stuart R. J. Saunders
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Paper Abstract

Thermal barrier coatings are widely used in heat engines for improving efficiency by allowing higher operating temperatures; yttria stablised zirconia is the most widely used material. Their use has been extended to rotating parts, in particular to gas turbine engine blades, and any loss of coating would represent a major problem. During deposition of the coating, a thin (< 1μm) alumina layer grows due to oxidation of the bondcoat, and it is this alumina layer which promotes bonding between the coating and the coated substrate. The spectral shape and position of the R-line fluorescence of Cr3+ ions normally present in small amounts in the alumina is sensitive to stress, temperature and other environmental effects. Stress is the key factor determining spallation, and piezospectroscopy refers to the use of spectroscopic measurement to determine stress within a material. Measurements have been carried out as a function of various ageing treatments in order to evaluate the potential of the technique to be a non-destructive probe for determining the onset of spallation. Interpreting the changes in the fluorescence spectra requires the use of sophisticated curve-fitting techniques and therefore requires reliable and accurate measurements. This paper will discuss these measurement requirements and their potential for development into a non-destructive tool for lifetime prediction of these structures.

Paper Details

Date Published: 14 November 2003
PDF: 11 pages
Proc. SPIE 5192, Optical Diagnostic Methods for Inorganic Materials III, (14 November 2003); doi: 10.1117/12.509186
Show Author Affiliations
Christopher J. Chunnilall, National Physical Lab. (United Kingdom)
James P. Banks, National Physical Lab. (United Kingdom)
Guofeng Chen, National Physical Lab. (United Kingdom)
Jessica Y. Cheung, National Physical Lab. (United Kingdom)
Stuart R. J. Saunders, National Physical Lab. (United Kingdom)

Published in SPIE Proceedings Vol. 5192:
Optical Diagnostic Methods for Inorganic Materials III
Leonard M. Hanssen, Editor(s)

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