Abstract
Molybdenum disulfide (MoS2) is well known for exceptional friction and wear properties in inert and high vacuum environments. However, these tribological properties degrade in humid and high temperature environments for reasons that are not fully understood. A prevailing hypothesis suggests that moisture and thermal energy facilitate oxidation, which increases the shear strength of the sliding interface. The purpose of this study is to elucidate the contributions of water, oxygen, and temperature to the tribological degradation of MoS2. Generally speaking, we found a minimum friction coefficient that occurred at a temperature we defined as the transition temperature. This transition temperature ranged from 100 to 250 °C and was a strong function of the MoS2 preparation and thermal sliding history. Below the transition temperature, friction increased with increased water, but was insensitive to oxygen. Above the transition, friction increased with increased oxygen, but decreased to a limited extent with increased water. These results are generally consistent with prior results, but clarify some inconsistencies in the literature discussions. Contrary to the prevailing hypothesis, the results suggest that water does not promote oxidation near room temperature, but directly interferes with lamellar shear through physical bonding. Increased temperatures drive off water and thereby reduce friction up to the transition temperature. The results suggest that oxidation causes increased friction with increased temperature above the transition temperature. The data also suggest that water helps mitigate high temperature oxidation by displacing the environmental oxygen or by preferentially adsorbing to the surface.
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References
Lansdown, A.R.: Molybdenum Disulphide Lubrication, 1st ed. Tribology Series, 35. Elsevier, Amsterdam (1999)
Donnet, C., Martin, J.M., LeMogne, T., Belin, M.: Super-low friction of MoS2 coatings in various environments. Tribol. Int. 29(2), 123–128 (1996)
Sliney, H.E.: High-temperature solid lubricants. 1. Layer lattice compounds and graphite. Mech. Eng. 96(2), 18–22 (1974)
Fusaro, R.L.: Lubrication and Failure Mechanism of Molybdenum Disulfide Films. I. Effect of Atmosphere. NASA, Cleveland, OH (1978)
Stewart, T.B., Fleischauer, P.D.: Chemistry of sputtered molybdenum-disulfide films. Inorg. Chem. 21(6), 2426–2431 (1982)
Dudder, G., Zhao, X., Krick, B., Sawyer, W.G., Perry, S.: Environmental effects on the tribology and microstructure of MoS2–Sb2O3–C films. Tribol. Lett. 42(2), 203–213 (2011)
Zhao, X.Y., Perry, S.S.: The role of water in modifying friction within MoS(2) sliding interfaces. ACS Appl. Mater. Interfaces 2(5), 1444–1448 (2010)
Midgley, J.W.: The frictional properties of molybdenum disulfide. J. Inst. Petroleum 42, 312–315 (1956)
Pritchard, C., Midgley, J.W.: The effect of humidity on the friction and life of unbonded molybdenum disulphide films. Wear 13(1), 39–50 (1969)
Gao, C., Bredell, L., Kuhlmannwilsdorf, D., Makel, D.D.: Micromechanics of Mos2 lubrication. Wear 162, 480–491 (1993)
Holinski, R., Gänsheimer, J.: A study of the lubricating mechanism of molybdenum disulfide. Wear 19(3), 329–342 (1972)
Johnston, R.R., Moore, A.J.W.: Water adsorption on molybdenum disulfide containing surface contaminants. J. Phys. Chem. 68(11), 3399–3406 (1964)
Uemura, M., Saito, K., Nakao, K.: A mechanism of vapor effect on friction coefficient of molybdenum-disulfide. Tribol. Trans. 33(4), 551–556 (1990)
Degee, A.W.J., Salomon, G., Zaat, J.H.: On mechanisms of Mos2-film failure in sliding friction. ASLE Trans. 8(2), 156–163 (1965)
Fleischauer, P.D., Lince, J.R.: A comparison of oxidation and oxygen substitution in MoS2 solid film lubricants. Tribol. Int. 32(11), 627–636 (1999)
Haltner, A.J., Oliver, C.S.: Effect of water vapor on friction of molybdenum disulfide. Ind. Eng. Chem. Fundam. 5(3), 348–355 (1966)
Panitz, J.K.G., Pope, L.E., Lyons, J.E., Staley, D.J.: The tribological properties of Mos2 coatings in vacuum, low relative-humidity, and high relative-humidity environments. J. Vac. Sci. Technol. A Vac. Surf. Films 6(3), 1166–1170 (1988)
Pardee, R.P.: Effect of humidity on low-load frictional properties of a bonded solid film lubricant. ASLE Trans. 15(2), 130–142 (1972)
Salomon, G., De Gee, A.W.J., Zaat, J.H.: Mechano-chemical factors in MoS2-film lubrication. Wear 7(1), 87–101 (1964)
Cannon, P., Norton, F.J.: Reaction between molybdenum disulphide and water. Nature 203(494), 750–751 (1964)
Fleischauer, P.D.: Effects of crystallite orientation on environmental stability and lubrication properties of sputtered MoS2 thin-films. ASLE Trans. 27(1), 82–88 (1984)
Ross, S., Sussman, A.: Surface oxidation of molybdenum disulfide. J. Phys. Chem. 59(9), 889–892 (1955)
Kingsbury, E.P.: Solid film lubrication at high temperature. ASLE Trans. 1(1), 121–123 (1958)
Kubart, T., Polcar, T., Kopecky, L., Novak, R., Novakova, D.: Temperature dependence of tribological properties of MoS(2) and MoSe(2) coatings. Surf. Coat. Technol. 193(1–3), 230–233 (2005)
Godfrey, D., Nelson, E.C.: Oxidation characteristics of molybdenum disulfide and effect of such oxidation on its role as a solid film lubricant. NACA TN No. 1882 (1949)
Sliney, H.E.: Solid lubricant materials for high-temperatures—a review. Tribol. Int. 15(5), 303–315 (1982)
Muratore, C., Bultman, J.E., Aouadi, S.M., Voevodin, A.A.: In situ Raman spectroscopy for examination of high temperature tribological processes. Wear 270(3–4), 140–145 (2011)
Windom, B.C., Sawyer, W.G., Hahn, D.W.: A Raman spectroscopic study of MoS(2) and MoO(3): applications to tribological systems. Tribol. Lett. 42(3), 301–310 (2011)
Lancaster, J.K.: A review of the influence of environmental humidity and water on friction, lubrication and wear. Tribol. Int. 23(6), 371–389 (1990)
Deacon, R.F., Goodman, J.F.: Lubrication by lamellar solids. Proc. R. Soc. Lond. Ser. A Math. Phys. Sci. 243(1235), 464–482 (1958)
Burris, D.L., Sawyer, W.G.: Addressing practical challenges of low friction coefficient measurements. Tribol. Lett. 35(1), 17–23 (2009)
Chromik, R.R., Baker, C.C., Voevodin, A.A., Wahl, K.J.: In situ tribometry of solid lubricant nanocomposite coatings. Wear 262(9–10), 1239–1252 (2007)
Pierce, D.E., Burns, R.P.: Evaluation of Solid Lubricants: The Chemistry of Sputtered MoS(x) Films Using Combined Thin Film Analysis Techniques. US Army Materials Technology Lab, Watertown, MA (1990)
Burris, D.L., Santos, K., Lewis, S.L., Liu, X., Perry, S.S., Blanchet, T., Schadler, L., Sawyer, W.G.: Polytetrafluoroethylene matrix nanocomposites for tribological applications. In: Friedrich, K. (ed.) Tribology of Polymeric Nanocomposites. Elsevier Science (2008)
Acknowledgments
The authors gratefully acknowledge the AFOSR (YIP FA9550-10-1–0295) and the University of Delaware Graduate Fellowship for financial support of this work. We would also like to thank Prof. Joshua Hertz (UD) and Dr. Andy Korenyi-Both (Tribologix) for discussions of the sputtering process and resulting structures.
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Khare, H.S., Burris, D.L. The Effects of Environmental Water and Oxygen on the Temperature-Dependent Friction of Sputtered Molybdenum Disulfide. Tribol Lett 52, 485–493 (2013). https://doi.org/10.1007/s11249-013-0233-8
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DOI: https://doi.org/10.1007/s11249-013-0233-8