Thermochemical compatibility of ytterbia-(hafnia/silica) multilayers for environmental barrier coatings

D. L. Poerschke, J. S. Van Sluytman, K. B. Wong, C. G. Levi

Research output: Contribution to journalArticlepeer-review

79 Scopus citations

Abstract

Environmental barrier coating (EBC) systems consisting of multiple layers tailored to address individual protection needs may offer improved performance relative to conventional architectures. If the requirements of thermochemical and thermomechanical compatibility are met, the deposition of a segmented thermal barrier coating on a dense rare earth silicate EBC could provide additional thermal protection and resistance to attack by molten deposits. The thermochemical compatibility between silicates in the YbO1.5-SiO 2 system and phases in the YbO1.5-HfO2 system was investigated by equilibrating powder compacts of selected ternary compositions; diffusion couples were used to simulate interactions at the layer interfaces in the proposed architectures. The deduced 1500 C ternary isothermal section reveals that the ordered δ-Yb4Hf3O 12 and H3-Yb6HfO11 phases are only compatible with ytterbium monosilicate (Yb2SiO5) EBC. Implementation of these hafnates in contact with ytterbium disilicate (Yb 2Si2O7) leads to interfacial reactions that facilitate layer debonding. The results provide criteria to guide the design of future thermal/environmental barrier coating architectures.

Original languageEnglish (US)
Pages (from-to)6743-6755
Number of pages13
JournalActa Materialia
Volume61
Issue number18
DOIs
StatePublished - Oct 2013

Bibliographical note

Funding Information:
This investigation was performed as part of AFOSR STTR Phase II FA9550-11-C-0010 funded collaboration with Directed Vapor Technology International Inc. (DVTI). DP received additional support from the Department of Defense through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program, and ONR Grant N00014-06-1-0322. The research made use of the MRL Shared Experimental Facilities, a member of the NSF-funded Materials Research Facilities Network (www.mrfn.org) supported by the MRSEC Program of the NSF under Award No. DMR 1121053. The authors are grateful to Drs. S. Eustis and D. Hass of DVTI, Dr. K. Lee of Rolls Royce and Dr. M Cinibulk of US Air Force Research Laboratory for helpful discussions, and to Drs. S. Krämer and G. Seward, UCSB, for assistance with TEM and EPMA compositional analysis, respectively.

Copyright:
Copyright 2013 Elsevier B.V., All rights reserved.

Keywords

  • Diffusion
  • Environmental barrier coatings
  • Interfaces
  • Phase diagram
  • Thermal barrier coatings

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