Role of Environment on the Shear-Induced Structural Evolution of MoS2and Impact on Oxidation and Tribological Properties for Space Applications

Tomas F. Babuska, John F. Curry, Michael T. Dugger, Ping Lu, Yan Xin, Sam Klueter, Alexander C. Kozen, Tomas Grejtak, Brandon A. Krick

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24 Scopus citations

Abstract

This work investigates the role of water and oxygen on the shear-induced structural modifications of molybdenum disulfide (MoS2) coatings for space applications and the impact on friction due to oxidation from aging. We observed from transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) that sliding in both an inert environment (i.e., dry N2) or humid lab air forms basally oriented (002) running films of varying thickness and structure. Tribological testing of the basally oriented surfaces created in dry N2 and air showed lower initial friction than a coating with an amorphous or nanocrystalline microstructure. Aging of coatings with basally oriented surfaces was performed by heating samples at 250 °C for 24 h. Post aging tribological testing of the as-deposited coating showed increased initial friction and a longer transition from higher friction to lower friction (i.e., run-in) due to oxidation of the surface. Tribological testing of raster patches formed in dry N2 and air both showed an improved resistance to oxidation and reduced initial friction after aging. The results from this study have implications for the use of MoS2-coated mechanisms in aerospace and space applications and highlight the importance of preflight testing. Preflight cycling of components in inert or air environments provides an oriented surface microstructure with fewer interaction sites for oxidation and a lower shear strength, reducing the initial friction coefficient and oxidation due to aging or exposure to reactive species (i.e., atomic oxygen).

Original languageEnglish
Pages (from-to)13914-13924
Number of pages11
JournalACS Applied Materials and Interfaces
Volume14
Issue number11
DOIs
StatePublished - Mar 23 2022
Externally publishedYes

Funding

This material is based upon work supported by the National Science Foundation under Grant 2027029, Grant 1826251, and NSF GRFP 1842163. TEM work was performed at the National High Magnetic Field Laboratory, which is supported by National Science Foundation Cooperative Agreement DMR-1644779 and the State of Florida. This work was funded by the Laboratory Directed Research and Development (LDRD) program at Sandia National Laboratories, a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under Contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Keywords

  • MoS
  • aging
  • environment
  • friction
  • oxidation
  • wear

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