NDE of degradation of thermal barrier coating by means of impedance spectroscopy

Kazuhiro Ogawa, Dorian Minkov, Tetsuo Shoji, Minoru Sato, Hideo Hashimoto

Research output: Contribution to journalArticlepeer-review

78 Citations (Scopus)


Nondestructive evaluation of thermal barrier coating (TBC) degradation during service operation has received a wide attention for service life prediction of advanced gas turbines. In this work, TBC on nickel base superalloy degraded at various degrees by thermal aging is investigated. Particularly, TBC and Metal-Chromium-Aluminum-Yttrium alloy (McrAlY) (M indicates iron (Fe), cobalt (Co), nickel (Ni) or these combinations) bond coating interface where a detrimental reaction takes place and forms various reaction products during thermal aging, is studied in detail. Formation kinetics and physical properties of the reaction layer are evaluated by means of Impedance Spectroscopy (IS). Specimens aged at higher temperature and a longer aging time shows larger impedance. The impedance behavior of TBC and bond coating is found to be markedly changed by the formation of the reaction layer. Physical properties and thickness of the reaction layer are evaluated using the change of the impedance. A mechanistic interpretation of the cause of change in the physical properties and IS behavior are described.

Original languageEnglish
Pages (from-to)177-185
Number of pages9
JournalNDT and E International
Issue number3
Publication statusPublished - 1999 Apr


  • Alumina
  • Impedance spectroscopy
  • Reaction layer
  • TBC/MCrAlY interface

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering


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