Development and Characterization of Environmentally Benign, Corrosion-Inhibiting, Dry Film Lubricant Coatings
Solid film lubricants have found highly specialized utility in demanding, extreme-pressure tribology applications where conventional oils and greases cannot be employed. Early examples of dry film lubricants (DFL) contained toxic materials such as lead, antimony oxide and arsenic, as well as flammable, ozone-depleting solvents suspected carcinogenic activity. The best performing lubricants still m use today continue to employ these noxious components. Graphite is also prevalent in many conventional solid film lubricants. Unfortunately graphite promotes galvanic corrosion, particularly on steel substrates where these lubricants are widely utilized. Few changes have been made to early dry film lubricant formulations that are used in modem applications. However, on-going promulgation of strict environmental and safety regulations has severely restricted further use and development of solid film lubricants based on miasmatic chemistries. The goal of this work was to develop and characterize a solid film lubricant coating that does not contain volatile organic solvents, is free of human and environmental toxins, provides exceptional corrosion protection and cures at ambient temperature. It was to provide equal or improved endurance and lubricating properties as the nearly defunct chemistries from previous generations. The solid film lubricant coating developed in this study was tested to meet all performance requirements in Military Specification MIL-L-23398. An optimized combination of waterborne polyurethane resin, molybdenum disulfide, polytetrafluoroethylene, and coating additives produced a lubricant that met all requirements. Falex Pin and Vee Block testing for endurance life and load carrying capacity were extensively used to determine tribological performance. X-ray photoelectron spectroscopy, atomic force microscopy, optical microscopy and Fourier transform infrared analysis were employed to characterize underlying physical and chemical mechanisms of wear subjected to the lubricant. XPS and FTIR analysis showed dynamic reactions occurred on the surface of the lubricant during wear. Molybdenum oxidized under extreme pressure loads and sulfide changed to sulfate.
Coatings, Volatile organic compounds, Lubrication, Tribology
Perez, A. (2005). <i>Development and characterization of environmentally benign, corrosion-inhibiting, dry film lubricant coatings</i> (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.