Inspecting thermal barrier coatings by IR thermography

Paolo Giulio Bison; Sergio Marinetti; Ermanno G. Grinzato; Vladimir P. Vavilov; Federico Cernuschi; Daniele Robba

doi:10.1117/12.486019

1 April 2003 Inspecting thermal barrier coatings by IR thermography

Paolo Giulio Bison, Sergio Marinetti, Ermanno G. Grinzato, Vladimir P. Vavilov, Federico Cernuschi, Daniele Robba

Proceedings Volume 5073, Thermosense XXV; (2003) https://doi.org/10.1117/12.486019
Event: AeroSense 2003, 2003, Orlando, Florida, United States

Abstract

As far as power generation is concerned, coating technologies find the main and more advanced applications. Nowadays, superalloys available for manufacturing hot path components in gas turbine like combustion liners, blades and vanes can not sustain temperatures up to 1100°C. In order to guarantee a significative temperature drop ceramic thermal barrier coatings are deposited onto the metallic core. The thickness of thermal barrier coatings (TBC) ranges from a few hundreds microns up to 1 millimetre or more, depending on component and deposition technique (mainly Air Plasma Spray or Electron Beam Physical Vapour Deposition). The structural integrity of both the substrate and the coating and their mutual adhesion is a key point because any loss of the protective layer exposes the bulk material to an extremely aggressive environment in terms of oxidation and temperature. Therefore, TBC must be tested for detecting of defects during both quality control and periodic in-service inspections. Because of the key role played by thickness and low thermal diffusivity of TBC in the decreasing of the substrate material temperature, both delaminations and thickness variation must be detected and classified. Pulsed Thermography has been successfully applied to this application field. Nevertheless, the procedure gives ambiguous results when thickness or thermal properties change in a continuous way within the thermal barrier. In this paper, a specific study on the detection performances of NDE techniques is presented, even when a non-uniform TBC thickness is superimposed to the disbonding defect. Tests performed at workshop on real and specifically manufactured components are reported. Dedicated processing algorithms improving the test reliability and effectiveness are presented as well. Tests on real components on the field are also reported.

Citation Download Citation

Paolo Giulio Bison, Sergio Marinetti, Ermanno G. Grinzato, Vladimir P. Vavilov, Federico Cernuschi, and Daniele Robba "Inspecting thermal barrier coatings by IR thermography", Proc. SPIE 5073, Thermosense XXV, (1 April 2003); https://doi.org/10.1117/12.486019

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