Elastic modulus evolution and behaviour of Si/Mullite/BSAS-based environmental barrier coatings exposed to high temperature in water vapour environment

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DOIResolve DOI: http://doi.org/10.1007/s11666-010-9599-4
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TypeArticle
Journal titleJournal of thermal spray technology
Volume20
Issue1-2
Pages9299; # of pages: 8
SubjectBSAS; Elastic modulus; subject topic C; Environmental barrier coatings; Heat-exposure; Mullite; water vapor
AbstractSi-based ceramics (e.g., SiC and Si3N4) are known as promising high-temperature structural materials in various components where metals/alloys reached their ultimate performances (e.g., advanced gas turbine engines and structural components of future hypersonic vehicles). To alleviate the surface recession that Si-based ceramics undergo in a high-temperature environmental attack (e.g., H2O vapor), appropriate refractory oxides are engineered to serve as environmental barrier coatings (EBCs). The current stateof- the-art EBCs multilayer system comprises a silicon (Si) bond coat, mullite (3Al2O3 2SiO2) interlayer and (1 2 x)BaO xSrO Al2O3 2SiO2, £ x £ 1 (BSAS) top coat. In this article, the role of hightemperature exposure (1300 °C) performed in H2O vapor environment (for time intervals up to 500 h) on the elastic moduli of air plasma sprayed Si/mullite/BSAS layers deposited on SiC substrates was investigated via depth-sensing indentation. Laser-ultrasonics was employed to evaluate the E values of as-sprayed BSAS coatings as an attempt to validate the indentation results. Fully crystalline, crack-free, and near-crack-free as-sprayed EBCs were engineered under controlled deposition conditions. The absence of phase transformation and stability of the low elastic modulus values (e.g., ~60-70 GPa) retained by the BSAS top layers after harsh environmental exposure provides a plausible explanation for the almost crack-free coatings observed. The relationships between the measured elastic moduli of the EBCs and their microstructural behavior during the high-temperature exposure are discussed.
Publication date
LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); NRC Industrial Materials Institute
Peer reviewedYes
NRC number52514
NPARC number16541829
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Record identifier3a57beb2-4426-4fa0-8c61-bbab2c844de7
Record created2010-12-22
Record modified2016-05-09
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