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Health Monitoring of Thermal Barrier Coatings by Mid-Infrared ReflectanceMid-infrared (MIR) reflectance is shown to be a powerful tool for monitoring the integrity of 8wt% yttria-stabilized zirconia (8YSZ) thermal barrier coatings (TBCs). Because of the translucent nature of plasma-sprayed 8YSZ TBCs, particularly at MIR wavelengths (3 to 5 microns), measured reflectance does not only originate from the TBC surface, but contains strong contributions from internal scattering within the coating as well as reflectance from the underlying TBC/substrate interface. Therefore, changes in MIR reflectance measurements can be used to monitor the progression of TBC delamination. In particular, MIR reflectance is shown to reproducibly track the progression of TBC delamination produced by repeated thermal cycling (to 1163 C) of plasma-sprayed 8YSZ TBCs on Rene N5 superalloy substrates. To understand the changes in MIR reflectance with the progression of a delamination crack network, a four-flux scattering model is used to predict the increase in MIR reflectance produced by the introduction of these cracks.
Document ID
Document Type
Preprint (Draft being sent to journal)
Eldridge, J. I.
(NASA Glenn Research Center Cleveland, OH, United States)
Spuckler, C. M.
(NASA Glenn Research Center Cleveland, OH, United States)
Nesbitt, J. A.
(NASA Glenn Research Center Cleveland, OH, United States)
Street, K. W.
(NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
August 21, 2013
Publication Date
December 30, 2002
Subject Category
Quality Assurance And Reliability
Meeting Information
27th Annual Cocoa Beach Conference(Cocoa Beach, FL)
Funding Number(s)
WBS: WBS 22-714-04-30
Distribution Limits
Work of the US Gov. Public Use Permitted.
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