Oxidation characteristics of MoS2 and other solid lubricants

SYSTEMATIC ABSTRACTS OF CURRENT LITERATURE tion of base stock and additive quality is demonstrated. The relationship of acid phosphate rather than TCP concentration to antiwear properties of compounded lubricants is suggested by transition load studies. The Load-carrying Mechanism of Organic Sulfur Compounds-Application of Electron Probe Microanalysis. K. G. AHum and E. S. Forbes, ASLE Trans., II (z) (1968) 162-175; 7 figs., 4 tables, 25 refs. A detailed literature survey has shown that considerable controversy exists on the mode of action of organic sulfur compounds as load-carrying additives. Previous work by the authors, using the four ball extremepressure and wear tests, has suggested that under mixed lubrication (anti-wear) conditions, organic disulfides arc adsorbed on to the metal surface with cleavage of the sulfursulfur bond to form an iron mercaptide layer. However, under more severe conditions such as exist in the extreme-pressure region, cleavage of the carbon-sulfur bond occurs to give an inorganic sulfur-containing layer. Thus the different relative performances of disulfides in the mixed lubrication and extreme-pressure regions are readily explained. This paper now presents the results of a detailed examination of the wear scars obtained with certain disulfides using an electron probe microanalyser. The results illustrate the use of this new technique for studying the nature of worn surfaces but, even more important, lend strong support to the suggested mechanism of action of organic disulfides. The results of this study also offer an explanation for the apparently conflicting rig test results often reported in the literature. Some Effects of Non-hydrocarbon Base Oil Constituents on the Friction and Surface Coating Formation Obtained with Three AdditiGes. F. G. Rounds, ASLE Trusts., II (I) (1968) 19-30; 10 figs., 6 tables, 12 refs. The effects of antiwear, e.p., and friction modifying additives on the friction of steelon-steel are greater when blended in more highly refined base oils. To explain this observation, non-hydrocarbons (sulfur, nitrogen, and oxygen compounds) of the types either (a) initially present in less well-refined oils or (b) formed by oil oxidation during use, were added to base blends consisting of a chlorinated wax, a sulfurized terpene oil, or didodecyl phosphite in a highly refined mineral oil. The resulting changes in friction and surfacecoating formation were measured as a fnnction of the non-hydrocarbon concentration. The additive effects on friction were canceled selectively by some of the 34 non-hydrocarbons studied at concentrations that could be encountered in less well-refined oils,

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whereas pure hydrocarbon additions had little effect. Mechanisms for the observed friction and surface coating changes have been proposed. Contribution of Additives to formance of Petroleum Products. Proc.

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Elsevier, London, 1968, Vol. papers + panel discussion.

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The Lubricating Performance of an “in situ” Process Moss Film in Air and in Liquids. ,4. Di Sapio and J. Maloney, ASLE Trans., ZI (I) (1968) 56-63: 9 figs., 6 tables, 15 refs. The performance of a synthetic MoSz film, produced by electrodeposition of molybdic oxide followed by a temperature-pressure HzS conversion to a molybdenum sulfide is examined under extremecompound, pressure conditions immersed in various fluids. Friction, wear and e.p. characteristics, measured on various test machines, are compared to those of the fluids alone and also to conventional bonded films. The fluids examined include: mineral oil, jet fuel, hydraulic fluid, sihcone fluid. The dry films include: burnished MoSz MIL-L-8937 resin-bonded film, powder, MlL-L-8129 silicate-bonded film and the synthetic “in situ” MoSz film. The performance of the svnthetic MO& film on titanium and stainless steel is also examined. Oxidation Characteristics of Moss and other Solid Lubricants. M. T. Lavik, T. M. Medved and G. D. Moore, ASLE Tvans., II (I) (1968) 44-5.5; 12 figs., 3 tables, rg refs. Thermogravimetric oxidation data are presented for fifteen refractory meta dichalcogenides. Interpretation of these data is supported by oxidation thermograms of the chatcogens and the refractory metals and by X-ray diffraction analysis of the oxidized products. The effects of humidity, heating rate, and particle size on oxidation of the dichalcogenides are presented. Thermogravimetric analysis is shown to be helpful in detecting impurities, such as unreacted elements, in commercial samples. Some dichalcoaenides are shown to retain the same relative oxidation stabilitv, when bonded in thin films with a ceramic, -as for pure powder samples. A table is presented summarizing these oxidation characteristics together with information from the literature on crystal structures, electrical resistivities, and densities. Solid Film Lubrication of Worm Gears. H. S. Hass, ASLE Trans.. IL (I) (1968) 81-87: 6 figs., I table, 8 refs. ’ ~_ A study was conducted to determine the W&Z+‘,X2 (1968)&+305