Environmental Barrier Coatings for the Energy Efficient Heat Engines Program [electronic resource].

Published:: Washington, D.C. : United States. Dept. of Energy, 2004.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Additional Creators:: Northwestern University (Evanston, Ill.), United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information

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Summary:

This program aimed to develop a fundamental understanding of the microstructural, mechanical, and chemical properties of Ta₂O₅-based coatings for Si₃N₄ (AS800) substrates and optimize such coatings for environmental barriers. The program consisted of three tasks: processing of Ta₂O₅ coatings, phase and microstructural development, and life-limiting phenomena. Northwestern University formed a cross-functional team with Lehigh University, Honeywell Inc., and Oak Ridge National Laboratory. The major accomplishments are: (1) Conditions for the plasma spray of Ta₂O₅ and its alloys were optimized to provide maximum density and thickness. (2) Adherent small particle plasma spray coatings of Ta₂O₅ can be routinely prepared. (3) Ta₂O₅ can be stabilized against its disruptive phase transformation to 1400 C by the addition of one or more oxides of Al, La, and/or Nb. (4) Residual stresses in the Ta₂O₅ coatings were measured using X-rays and changed with thermal exposure. (5) Properly doped coatings are more resistant against thermal cycling than undoped coatings, and can be cycled many thousand times without spallation. (6) Water vapor testing in the ORNL Keiser Rig of adherent coatings showed that undoped Ta₂O₅ is not an effective barrier at preventing chemical changes to the AS800. (7) Limited water vapor testing of doped and adherent coatings, which had successfully survived many thermal cycles, showed that in the water vapor environment, de-cohesion may occur.

Report Numbers:

E 1.99:940178

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Note:

Published through SciTech Connect.
10/31/2004.
Katherine Faber.

Type of Report and Period Covered Note:

Final;

Funding Information:

FC26-01CH11086

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