MORTON ANTLER’
Previous Work
Chemical Research Division,
Simard, Russell, and Nelson (70) showed that lead naphthenate in active sulfur oils forms lead sulfate or lead sulfide on metals during rubbing, and implied that these films are good lubricants. Hugel ( 4 ) attempted unsuccessfully to produce molybdenum sulfide from a variety of oil additives. Molybdenum xanthates, however, were effective antiwear additives, and Hugel presumed that a complex molybdenum oxysulfide, MOO&,was the antiwear film. Hugel’s experiments with the molybdenum xanthates were repeated in this laboratory (8). Actually, the antiwear mechanism involved EP activity in part, as FeS was identified on worn hard steel surfaces by electron diffraction in runs with molybdenum isobutylxanthate.
Ethyl Corp., Detroit 20, Mich.
BOUNDARY
lubrication of metals by the extreme pressure (EP) mechanism involves thermal decomposition of the lubricant during rubbing to produce a compound with the metal surface. In another mechanism which involves some features of EP activity, inorganic solids are deposited, but without corroding the rubbing surfaces. All atoms in the film are from the lubricant which is degraded by frictional heat. This mechanism, in this discussion called “noncorrosive film formation,” is applicable to all types of systems, such as noble and base metals, ceramics, glass, and plastics. The lubricating film can be regenerated as it is worn away, or preformed by a run-in followed by rubbing without the film-former compound. In principle, any solid can be deposited, including recognized solid lubricants. In the work described, noncorrosive film formation has been studied with several simple organometallics. Organometallics contain one or more metal-carbon bonds. This chemical definition excludes soaps and other compounds in which a metal is joined to carbon through oxygen, sulfur, or other atoms. These distinctions have not been made in several recent technical publications in lubrication. These compounds include tetraethyllead (TEL), (methylcyclopentadienyl) manganese tricarbonyl (AK33X), and di-n-butyltin sulfide (BuzSnS), chosen solely because they have very different structures and properties and are readily available. Present address, Borg-Warner Research Center, Des Plaines, Ill.
Experimental Technique
Studies were made in a four-ball wear machine and four-ball extreme pressure tester (6). Friction force in the wear machine was measured continuously with a cantilever and strain gages coupled to a Sanborn carrier preamplifier and recorder. Commercial grade TEL, AK-33X, and BuzSnS were purified by several days’ contact with activated alumina.
Other organometallics were well-purified laboratory materials. The mineral oil base lubricant, Bayol 85 (Enjay Co., Inc.), a paraffinic white oil having a viscosity of 17.15 cs. at 100’ F., 3.64 cs. a t 210’ F., and a viscosity index of 107.5, was used without further purification. Mineral oil blends of these additives did not spread on water at pH 3 or 10.5, which indicates that they were free of hydrophylic impurities (12). The silicone fluids, Dow Corning 200 (a dimethylpolysiloxane of 100-cs. viscosity at 25’ C.) and 710 (a phenylmethylpolysiloxane of 500-cs. viscosity at 25’ C.), were used as received. All blends were on a weight per cent basis. Test specimens were commercial ball bearings, except for the 0.001-inch thick gold-plated and the 0.015-inch chro~ mium-plated 52100 stpel and the cast iron balls. The cast iron was representative of automotive piston ring material. All specimens and machine parts in contact with the lubricants were cleaned in multiple baths of hot reagent grade benzene and n-hexane before use. Except where otherwise indicated, 52100 steel was used. Test conditions in the hear machine were 2-hour runs at 50’ C. and 570 r.p.m.; in the extreme pressure tester, 1-minute runs at room temperature and 1750 r.p.m.
Organometallics are proposed for lubricant applications. Some are uniquely effective wear inhibitors and function by a hitherto little studied mechanism, which involves degradation of the compound on contacting asperities due to frictional heat generated during rubbing. Inorganic lubricating solids are produced without chemical attack of the surfaces. VOL. 51, NO. 6
JUNE 1959
753
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ELSE OIL
