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Recently updated on Maggio 11th, 2021 at 08:33 am
TURBINE FORUM 2006 – Advanced coatings for high temperatures NIZZA – France – 26-28 Aprile 2006 Claudia Rinaldi*, Letizia De Maria*, Alessio Martinelli*, Valter Sergo** *CESI RICERCA **DIMCA Università di Trieste In the frame of a National Research Project on Technologies for Gas Turbine Monitoring and Life Assessment, innovative non destructive techniques (Photoluminescence Piezospectroscopy (PLPS) and Frequency Scanning Eddy Current (FSECT)) were applied to TBC integrity estimation before and after thermal cycled exposure both on samples and on components. Photo-Luminescence Piezospectroscopy characterisation was successfully applied not only to EB-PVD but also to Pseudo-Columnar Air Plasma Sprayed thermal barrier coated samples. In a first phase of the study, PLPS technique was validated on specimens with EB-PVD thermal barriers, at increasing time intervals during exposure at high temperatures, both in isothermal and cyclic conditions; in such way some reference knowledge was obtained on the evolution of the interface between NiCoCrAlYRe (or PtAl) BC and columnar TBC. Low TGO stress values were detected associated to localised damage still undetectable by thermography, but confirmed by metallography. A portable PLPS was developed. Measurements were performed on some components both as received and after operation (about 22000 EOH). Mapping of the TGO Residual stress on both new and service exposed blades were integrated with the FSECT results. On the service exposed blade PLPS results showed that the oxidation process was generally low. Nevertheless an extended area of morphological interface change was not-destructively detected; further destructive metallographic analyses on sections of the component indicated that the low value of residual stress measured was associated to degradation processes such as local TGO penetration into the BC and microcracking in the TGO layer, even if the TGO thickness was limited. Finally the application of PLPS to Pseudo-Columnar Air Plasma Sprayed coated samples, after exposure to cyclic oxidation tests of increasing duration was successful; further activity is ongoing to confirm that this technique is able to monitor the TGO stress and evolution also on this type of TBC.
31 Dicembre 2006
Tecnologie innovative volte alla flessibilizzazione degli impianti a ciclo combinato (WP 1.1 (PROD))