Anisotropic crack propagation behavior for the silicon-bond coat layer in a multilayer coated system

Yutaro Arai, Ryo Inoue, Hideki Kakisawa

Research output: Contribution to journalArticlepeer-review


This study sought to examine the relationship between the degradation mechanism, thermal stress, and crack propagation behavior in environmental barrier coating (EBC) systems. An EBC system composed of a mullite topcoat (TC), Si-bond coat (BC), and SiC substrate was prepared by atmospheric plasma spraying. Heat exposure tests were conducted to evaluate the microstructure of the EBC system at 1300°C for 1, 10, 50, and 100 h. The fracture resistance of the Si BC for the in-plane (direction parallel to each layer, 0.4–0.6 MP (Formula presented.)) and through-thickness directions (direction from the TC to substrate, 1.7–2.1 MP (Formula presented.)) differed because a thermal compressive stress was induced for the in-plane direction owing to the mismatch of the thermal expansion coefficients for each layer, which acted as a barrier for crack propagation. However, cracks tended to propagate in the in-plane direction because they were not affected by the in-plane compressive stress. These results clearly showed that Si BC exhibited in-plane anisotropy and crack propagation after heat exposure, which were the major sources of delamination of the EBC system.

Original languageEnglish
Pages (from-to)947-956
Number of pages10
JournalInternational Journal of Applied Ceramic Technology
Issue number3
Publication statusPublished - 1 May 2021


  • barrier coatings
  • bond coat
  • mechanical properties
  • plasma spraying
  • silicon

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