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Anisotropic crack propagation behavior for the silicon‐bond coat layer in a multilayer coated system
Author(s) -
Arai Yutaro,
Inoue Ryo,
Kakisawa Hideki
Publication year - 2021
Publication title -
international journal of applied ceramic technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.4
H-Index - 57
eISSN - 1744-7402
pISSN - 1546-542X
DOI - 10.1111/ijac.13679
Subject(s) - materials science , composite material , thermal barrier coating , mullite , microstructure , anisotropy , substrate (aquarium) , delamination (geology) , layer (electronics) , stress (linguistics) , fracture mechanics , fracture (geology) , coating , silicon , metallurgy , optics , paleontology , ceramic , linguistics , oceanography , physics , subduction , philosophy , biology , tectonics , geology
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 a m ) and through‐thickness directions (direction from the TC to substrate, 1.7–2.1 MP a m ) 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.