Steam oxidation and microstructural evolution of rare earth silicate environmental barrier coatings

A primary failure mode for environmental barrier coatings (EBCs) on SiC ceramic matrix composites (CMCs) is the oxidation of the intermediate Si‐bond coating, where the formation of SiO2 at the bond coating–EBC interface results in debonding and spallation. This work compares the microstructure evol...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 2023-01, Vol.106 (1), p.613-620
Main Authors: Ridley, Mackenzie, Kane, Kenneth, Lance, Michael, Parker, Cory, Su, Yi‐Feng, Sampath, Sanjay, Garcia, Eugenio, Sweet, Marshall, O'Connor, Molly, Pint, Bruce
Format: Article
Language:English
Subjects:
Ceramic matrix composites
Coatings
environmental barrier coatings (EBC)
Evolution
Failure modes
Kinetics
Microstructure
oxidation
Oxidation rate
Raman spectroscopy
Reaction kinetics
Silicon dioxide
Spallation
Ytterbium
Yttrium
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Summary:A primary failure mode for environmental barrier coatings (EBCs) on SiC ceramic matrix composites (CMCs) is the oxidation of the intermediate Si‐bond coating, where the formation of SiO2 at the bond coating–EBC interface results in debonding and spallation. This work compares the microstructure evolution and steam oxidation kinetics of the Si‐bond coating beneath yttrium/ytterbium disilicate ((Y/Yb)DS) and ytterbium disilicate/monosilicate (YbDS/YbMS) EBCs to better understand the impact of EBC composition on oxidation kinetics. After 500 1‐h cycles at 1350°C, (Y/Yb)DS displayed a decreasing concentration of the monosilicate minor phase and increasing concentration of porosity as furnace cycling time increased, whereas the YbDS/YbMS EBC displayed negligible microstructural evolution. For both EBC systems, thermally grown oxide growth rates in steam were found to increase by approximately an order magnitude compared to dry air oxidation. The (Y/Yb)DS EBC displayed a reduced steam oxidation rate compared to YbDS/YbMS.
ISSN:0002-7820
1551-2916
DOI:10.1111/jace.18769