Highly Oriented MoS2 Coatings: Tribology and Environmental Stability
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Molybdenum disulfide (MoS2) coatings have been prepared via nitrogen (N2) spray deposition, a process which deliberately impinges particulates of MoS2 onto a substrate yielding a preferential basally oriented state. Adherent and highly oriented 100- to 300-nm-thick coatings were produced. These coatings exhibited lower initial friction coefficients than sputtered films in dry and humid environments. Such reductions likely stem from a higher degree of basal plane orientation throughout the film as confirmed by XRD. Initial friction in humid air for sprayed coatings (µ = 0.10) was half that of sputtered coatings (µ = 0.21), showing the ability of oriented surface films to produce a low shear strength interface. Aging of these coatings in a humid nitrogen environment also showed the propensity for the films to resist poisoning of their structure which could otherwise result in degraded tribological performance. These results also support the hypothesis that water vapor does not contribute to the oxidation of MoS2.
KeywordsMoS2 Nitrogen spray Aging Roughness Friction Wear Oxidation Water vapor
The authors would like to thank Sandia National Laboratories staff members Paul Kotula for acquisition of TEM images, Michael Rye for FIB sample preparation, and Bonnie McKenzie for SEM and EDS microscopy. We thank Lehigh University Tribology Lab members Mark Sidebottom and Guosong Zeng for discussions and help in setting up instrumentation. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
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