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Recent Advances in NDT techniques for gas turbine coatings

pubblicazioni - Articolo

Recent Advances in NDT techniques for gas turbine coatings

Claudia Rinaldi*, Letizia De Maria*, Steve Osgerby** 8th Liege Conference – Materials for Advanced Power Engineering Liege, 18-20 Settembre 2006 * CESI RICERCA ** NATIONAL PHYSICAL LABORATORY, TEDDINGTON, MIDDLESEX, TW11 0LW UK The quality and endurance of metallic and thermal barrier coatings used on gas turbine components is a key issue for life management. As a consequence there is increasing industrial interest in techniques that assess coating condition not only prior to introduction into service but also after operation ie to monitor the actual degradation level of the metallic coating (bond coat) and the integrity of TBCs. Recently there has been increasing interest in the development of reliable non-destructive techniques that are able to evaluate the condition of coatings, thus avoiding irreversible component damage. In this paper a range of non-destructive techniques applicable to such complex coatings are reviewed. Examples are drawn from work contributed to COST522 and COST538; activities with the authors’ Institutes; and from published literature. This review describes the complementary capabilities and peculiar characteristics (eg spatial resolution) of the following techniques: frequency scanning eddy-current technique (F-SECT); photo-luminescence piezospectroscopy (PLPS); pulsed thermography; laser back scattering; and impedance spectroscopy. The potential for each of these techniques for in-situ monitoring of component condition is also discussed.

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