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Title: Initial Assessment of Environmental Barrier Coatings for the Prometheus Project

Abstract

Depending upon final design and materials selections, a variety of engineering solutions may need to be considered to avoid chemical degradation of components in a notional space nuclear power plant (SNPP). Coatings are one engineered approach that was considered. A comprehensive review of protective coating technology for various space-reactor structural materials is presented, including refractory metal alloys [molybdenum (Mo), tungsten (W), rhenium (Re), tantalum (Ta), and niobium (Nb)], nickel (Ni)-base superalloys, and silicon carbide (Sic). A summary description of some common deposition techniques is included. A literature survey identified coatings based on silicides or iridium/rhenium as the primary methods for environmental protection of refractory metal alloys. Modified aluminide coatings have been identified for superalloys and multilayer ceramic coatings for protection of Sic. All reviewed research focused on protecting structural materials from extreme temperatures in highly oxidizing conditions. Thermodynamic analyses indicate that some of these coatings may not be protective in the high-temperature, impure-He environment expected in a Prometheus reactor system. Further research is proposed to determine extensibility of these coating materials to less-oxidizing or neutral environments.

Authors:
Publication Date:
Research Org.:
Knolls Atomic Power Laboratory (KAPL), Niskayuna, NY
Sponsoring Org.:
USDOE
OSTI Identifier:
883656
Report Number(s):
MDO-723-0018
TRN: US0603536
DOE Contract Number:
DE-AC12-00SN39357
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS; 36 MATERIALS SCIENCE; 42 ENGINEERING; 22 GENERAL STUDIES OF NUCLEAR REACTORS; ALLOYS; BUILDING MATERIALS; CERAMICS; COATINGS; DEPOSITION; ENVIRONMENTAL PROTECTION; HEAT RESISTING ALLOYS; MOLYBDENUM; NICKEL; NIOBIUM; NUCLEAR POWER PLANTS; PROTECTIVE COATINGS; REFRACTORY METALS; RHENIUM; SILICIDES; SILICON CARBIDES; TANTALUM; THERMODYNAMICS; TUNGSTEN; NESDPS Office of Nuclear Energy Space and Defense Power Systems; NRPCT

Citation Formats

M. Frederick. Initial Assessment of Environmental Barrier Coatings for the Prometheus Project. United States: N. p., 2005. Web. doi:10.2172/883656.
M. Frederick. Initial Assessment of Environmental Barrier Coatings for the Prometheus Project. United States. doi:10.2172/883656.
M. Frederick. Thu . "Initial Assessment of Environmental Barrier Coatings for the Prometheus Project". United States. doi:10.2172/883656. https://www.osti.gov/servlets/purl/883656.
@article{osti_883656,
title = {Initial Assessment of Environmental Barrier Coatings for the Prometheus Project},
author = {M. Frederick},
abstractNote = {Depending upon final design and materials selections, a variety of engineering solutions may need to be considered to avoid chemical degradation of components in a notional space nuclear power plant (SNPP). Coatings are one engineered approach that was considered. A comprehensive review of protective coating technology for various space-reactor structural materials is presented, including refractory metal alloys [molybdenum (Mo), tungsten (W), rhenium (Re), tantalum (Ta), and niobium (Nb)], nickel (Ni)-base superalloys, and silicon carbide (Sic). A summary description of some common deposition techniques is included. A literature survey identified coatings based on silicides or iridium/rhenium as the primary methods for environmental protection of refractory metal alloys. Modified aluminide coatings have been identified for superalloys and multilayer ceramic coatings for protection of Sic. All reviewed research focused on protecting structural materials from extreme temperatures in highly oxidizing conditions. Thermodynamic analyses indicate that some of these coatings may not be protective in the high-temperature, impure-He environment expected in a Prometheus reactor system. Further research is proposed to determine extensibility of these coating materials to less-oxidizing or neutral environments.},
doi = {10.2172/883656},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Dec 15 00:00:00 EST 2005},
month = {Thu Dec 15 00:00:00 EST 2005}
}

Technical Report:

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  • The present state of development of thick thermal barrier coatings for truck diesel engines is assessed and areas where improved fundamental understanding is needed to properly pursue development are identified. Emphasis is given to the coating systems and design approaches that are being developed for the next generation of truck diesel engines under DOE/NASA support. It is noted that, while considerable progress has been made, the current level of understanding of coating system behavior is inadequate and this lack of fundamental understanding may impede current and future development. Several areas where improved understanding would be especially valuable are identified andmore » recommendations for research into those areas are offered. 106 refs., 12 figs., 1 tab.« less
  • This program aimed to develop a fundamental understanding of the microstructural, mechanical, and chemical properties of Ta{sub 2}O{sub 5}-based coatings for Si{sub 3}N{sub 4} (AS800) substrates and optimize such coatings for environmental barriers. The program consisted of three tasks: processing of Ta{sub 2}O{sub 5} 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 Ta{sub 2}O{sub 5} and its alloys were optimized to provide maximum density and thickness. (2) Adherent small particle plasma spray coatingsmore » of Ta{sub 2}O{sub 5} can be routinely prepared. (3) Ta{sub 2}O{sub 5} 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 Ta{sub 2}O{sub 5} 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 Ta{sub 2}O{sub 5} 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.« less
  • A program was initiated to evaluate the thermomechanical stability of plasma-deposited thermal barrier systems of the two-layer (duplex) type with an oxide outer layer and MCrAlY undercoat. Two oxides were included: MgO.ZrO/sub 2/ and ZrO/sub 2/.20 wt % Y/sub 2/O/sub 3/. Effects of oxide density and layer thickness were investigated. A CoNiCrAlY undercoat was used on all test specimens. Advantages of an intermediate layer of Cr or Ni-Cr were evaluated. Twenty-two combinations of intermediate layer composition and oxide composition, density, and thickness were evaluated. The work described includes specimen preparation thermal fatigue and oxidation test procedures, test results, metallurgical, microprobemore » and x-ray analyses. 25 figures, 14 tables.« less
  • Purpose is to determine the effects of variations in deposition parameters on the thermomechanical integrity of plasma deposited thermal barrier coatings for utility gas turbine airfoils. A much higher percentage of ZrO/sub 2/-20Y/sub 2/O/sub 3/ samples spalled than did MgO.ZrO/sub 2/ samples. Sample failure always involved shearing within the oxide near the undercoat interface. The ZrO/sub 2/-20Y/sub 2/O/sub 3/ samples appeared to be more prone to shear failure because they had a more lamellar structure as compared with the more interlocking structure of the MgO.ZrO/sub 2/. Surprisingly, although the MgO.ZrO/sub 2/ converted primarily to monoclinic during testing, destabilization did notmore » seem to impair thermal fatigue performance in this test sequence. The ZrO/sub 2/-20Y/sub 2/O/sub 3/ did not significantly change from the original cubic ZrO/sub 2/ structure during testing. Regarding density, the isothermal exposure overstressed the high density (90% theoretical) ZrO/sub 2/-20Y/sub 2/O/sub 3/ samples resulting in sample failure.« less