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| Abstract No.: |
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Scheduled at:
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Wednesday, May 04, 2022, Hall D 11:50 AM
Aviation Industry I
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| Title: |
Porosity in atmospheric plasma sprayed Yb-silicate environmental barrier coatings before and after crystallization heat treatment
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| Authors: |
Emine Bakan* / Forschungszentrum Jülich GmbH, Germany
Emine Bakan / Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research IEK-1, Germany
Robert Vaßen/ Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research IEK-1, Germany
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| Abstract: |
Environmental Barrier Coatings (EBCs) are used to shield SiC-based hot section components from water vapor in gas turbine engines. A baseline EBC system consists of a Si bond coat for oxidation protection and a Yb-silicate topcoat used as a volatilization barrier. Atmospheric plasma spray (APS) is a well-established and widely used process for the deposition of such coatings. In order to minimize the oxidation rates via diffusivity of oxidants through Yb-silicate topcoat, which results in a thermally growing silica scale at the interface that ultimately leads to a delamination failure, low open porosity volume is desired in the topcoats. In this presentation, the interplay between plasma spray conditions and coating microstructure such as crack density and crack length/width, the volume of secondary phase e.g. Yb2SiO5 phase in the coating deposited from Yb2Si2O7 feedstock as well as amorphous content will be examined. Furthermore, the microstructural evolution of the as-sprayed Yb-silicate coatings during a post crystallization heat treatment and a crack healing mechanism will be discussed in correlation with the plasma spray conditions. Finally, the open pore volume of the Yb-silicate coatings in the as-sprayed and crystalline state measured via mercury intrusion porosimetry will be presented.
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