Chapter 73. Health Monitoring of Thermal Barrier Coatings by Mid-Infrared Reflectance

  1. Waltraud M. Kriven and
  2. Hua-Tay Lin
  1. J. I. Eldridge,
  2. C. M. Spuckler,
  3. J. A. Nesbitt and
  4. K. W. Street

Published Online: 27 MAR 2008

DOI: 10.1002/9780470294802.ch73

27th Annual Cocoa Beach Conference on Advanced Ceramics and Composites: A: Ceramic Engineering and Science Proceedings, Volume 24, Issue 3

27th Annual Cocoa Beach Conference on Advanced Ceramics and Composites: A: Ceramic Engineering and Science Proceedings, Volume 24, Issue 3

How to Cite

Eldridge, J. I., Spuckler, C. M., Nesbitt, J. A. and Street, K. W. (2003) Health Monitoring of Thermal Barrier Coatings by Mid-Infrared Reflectance, in 27th Annual Cocoa Beach Conference on Advanced Ceramics and Composites: A: Ceramic Engineering and Science Proceedings, Volume 24, Issue 3 (eds W. M. Kriven and H.-T. Lin), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470294802.ch73

Author Information

  1. NASA Glenn Research Center Cleveland, OH 44135

Publication History

  1. Published Online: 27 MAR 2008
  2. Published Print: 1 JAN 2003

ISBN Information

Print ISBN: 9780470375839

Online ISBN: 9780470294802

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Keywords:

  • thermal barrier coatings;
  • anisotropy;
  • neutrons;
  • yttna-stabilized zirconia;
  • air plasma spray

Summary

Mid-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 μm), 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 pure-scattering model is used to predict the increase in MIR reflectance produced by the introduction of these cracks.