A prominent driving force for the spallation of thermal barrier coatings: Chemistry dependent phase transformation of the bond coat

L. T. Wu, R. T. Wu, P. Xiao, T. Osada, K. I. Lee, M. Bai

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)

Abstract

The influence of substrate and bond coat chemistry on the degradation mechanism leading to the early spallation of thermal barrier coatings (TBCs) has not been well understood despite years of research effort. This is largely due to the sheer number of factors (i.e. interfacial rumpling and oxide growth kinetics) that all seem to contribute to the degradation of TBCs. To clarify the chemical effect, extensive characterizations and in-depth analysis near the oxide-bond coat interface, were carried out on the isothermally exposed TBC specimens. It is evident that the formation of γ′ along the grain boundaries can significantly enhance rumpling, while martensitic transformation during cooling creates out-of-plane stresses and causes crack nucleation at the oxide-bond coat interface. These partial phase transformations in the β bond coat system were determined to be a prominent driving force for the TBC spallation. To prevent the early spallation of TBCs, it is necessary to minimize the formation rate of γ′ and martensitic phases, which can be achieved by tailoring the inherent substrate/bond coat composition as elucidated in this paper.

Original languageEnglish
Pages (from-to)22-35
Number of pages14
JournalActa Materialia
Volume137
DOIs
Publication statusPublished - 2017 Sep 15
Externally publishedYes

Keywords

  • Interfacial adhesion
  • Phase transformation
  • Platinum aluminide
  • Rumpling

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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