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Progress obtained in NDTs for GT coatings in the frame of COST 538 – WP1

pubblicazioni - Articolo

Progress obtained in NDTs for GT coatings in the frame of COST 538 – WP1

– WP1 Claudia Rinaldi*, Federico Cernuschi*, Letizia De Maria*, Ada Del Corno* 10th MC & Joint WG meeting COST 538 Praga, 7-8 Dicembre 2008 PRESENTAZIONE POWER POINT * CESI RICERCA In the frame of the COST ACTION 538 ( Life Extension of High Temperature Components), WP1 was devoted to develop models and NDT to detect coating degradation of components exposed to high temperatures in power plants. CESI RICERCA performed both modelling and NDT activities in the two projects I3 devoted to quantitative describe the TBC coating failure mechanisms and I5 aimed at developing thermographic and photoluminescence piezospectroscopy ( PLPS) techniques for the assessment of coating damage level on ex-service gas turbine blades. CESI RICERCA was required to present the progress obtained on NDTs in the frame of WP1. The presentation describes the following techniques: F-SECT ( frequency scanning eddy current method), PLPS , thermography and Acoustic Emission For each of them the results obtained in the four years of COST 538 are presented: – F-SECT lets to measure the loss of protective capability of the metallic bond coat; together with the coating life prediction model A non destructive estimation of the local temperature of the component can be obtained ( examples on ex-service blades are shown in the WP5 presentation). – PLPS measures the residual compressive stresses of the thermally Grown Oxide at the interface between metallic and ceramic layer of the columnar thermal barrier. The perfomed studies demonstrated that the measured parameter is an indicator of the spent life of the thermal barrier – A new thermographic method to detect the incipient cracking of the TBC near the interface with the metallic layer was developed at CESI RICERCA. The german partner FZJ developed a methodology to distinguish different types of defects applying the FFT to cooling curves of pulse thermography.

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