Stability of oxide-sulfate mixtures and implications for deposit-induced degradation of advanced alloys and coatings

Atharva S. Chikhalikar, Eeshani P. Godbole, David L. Poerschke

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Turbine engines ingest atmospheric aerosols that include multi-cation oxide-sulfate mixtures, which deposit onto surfaces within the engine. These deposits are often implicated in hot corrosion of alloys and bond coats and can accelerate thermomechanical failure of ceramic coatings through reaction and infiltration mechanisms. Understanding the intrinsic stability of oxide-sulfate deposits, including the tendency for sulfate decomposition, is important to identify efficient testing protocols. This work addresses that need by integrating experiments and computational thermodynamics models to systematically analyze the effect of deposit composition and temperature on the sulfate decomposition and melting behavior of five model mixed-anion deposits. Mass loss analysis and energy dispersive x-ray spectroscopy show that sulfate decomposition occurs much faster in the mixtures compared to pure calcium sulfate. The thermodynamic computations show that reaction pathways forming ternary and quaternary silicates accelerate sulfate decomposition faster than those forming binary reaction products. The results also show that multi-cation mixtures can suppress the evaporation of sodium and potassium sulfates, retaining the sulfate-bearing liquid to higher temperatures. The results can be used to differentiate the behavior of sulfate-, sulfate-oxide-, and oxide-based deposits, and to guide the discovery of new high temperature alloys and coating materials.

Original languageEnglish (US)
Article number118184
Pages (from-to)118184
JournalActa Materialia
Volume237
DOIs
StatePublished - Sep 15 2022

Bibliographical note

Funding Information:
This research has been supported by t he Office of Naval Research (Award number N68335-20-C-0472 monitored by Dr. David Shifler) in collaboration with QuesTek Innovations LLC. Part of this work was carried out in the Characterization Facility, College of Science and Engineering, University of Minnesota, which receives partial support from the NSF through the MRSEC (Award Number DMR-2011401 ) and the NNCI (Award Number ECCS-2025124 ) programs. The sponsors were not involved in the detailed study design, or the data collection, analysis, or interpretation. The authors are grateful to Drs. Pin Lu, Changning Niu, Jiadong Gong (QuesTek Innovations LLC) for insightful discussions.

Publisher Copyright:
© 2022

Keywords

  • Corrosion
  • Decomposition
  • Phase stability
  • Sulfates
  • Thermodynamic Modeling

MRSEC Support

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