Extreme Pressure Lubrication Research Articles

The mechanism of lubrication by molybdenum disulphide dispersed in oil and the effect of a zinc dialkyldithiophosphate additive

The effectiveness of the lubrication of hard smooth steel surfaces by molybdenum disulphide (MoS 2) dispersed in a mineral oil, both with and without a zinc dialkyldithiophosphate (ZDDP) additive, has been investigated using a four-ball extreme pressure lubricant test machine. Each oil, additive-oil or MoS 2 dispersion, exhibited a wear scar diameter-load curve with an abrupt transition from mild to severe wear at a characteristic load. When ZDDP was present in the oil, MoS 2 was effective at pre-transition but not post-transition loads, whereas in the absence of ZDDP the converse applied, with MoS 2 only beneficial above the transition load. These results are explained in terms of the adherence (or not) of MoS 2 particles to the films physically adsorbed on the steel surfaces at pre-transition loads. At the transition load the surface temperature reaches the desorption (or decomposition) temperature of the particular oil or additive film and MoS 2 then adheres to exposed metal, unless the latter chemically reacts with oil constituents to form a chemisorbed film.

Electrochemical deposition of solid lubricant films

This paper describes a new technique for producing adherent solid lubricant films with full control of thickness and location. MoS2 and FeCl2/CrCl3 coatings are formed on Mo and Fe/Cr wires respectively by electrochemical deposition from a bath of molten LiCl/KCl, and their frictional behaviour is studied at 400 C. It is suggested that this method has applications in fundamental studies of solid-film and extreme-pressure lubrication, and also in warm wire-drawing and other metal-forming processes. Presented at the first ASLE International Conference on Solid Lubrication held in Denver, Colorado, August 24–27, 1971

Effect of Surface Temperatures in Extreme Pressure Lubrication

Effect of Surface Temperatures in Extreme Pressure Lubrication

Electrochemical Deposition of Solid Lubricant Films

This paper describes a new technique for producing adherent solid lubricant films with full control of thickness and location. MoS2 and FeCl2/CrCl3 coatings are formed on Mo and Fe/Cr wires respectively by electrochemical deposition from a bath of molten LiCl/KCl, and their frictional behaviour is studied at 400 C. It is suggested that this method has applications in fundamental studies of solid-film and extreme-pressure lubrication, and also in warm wire-drawing and other metal-forming processes. Presented at the first ASLE International Conference on Solid Lubrication held in Denver, Colorado, August 24–27, 1971

Influence of Chemical Structures in Sulfurized Fats on Antiwear Behavior

Sulfurized methyl 10-undecenoate was used as the substance typifying sulfurized fatty extreme-pressure lubricant additives. The characteristic chemical structures in sulfurized methyl un-decenoate are sulfur-bridged long-chain di-esters, of which 1,20-dicarbomelhoxy-9,12-dimethyl-10,11 -dithiaeicosane is an example. The antiwear performance of this dithio-ester with respect to hardened AISI1095 steel in a pin-and-disk apparatus was indistinguishable from that of sulfurized methyl undecenoate. Esters such as methyl laurate and 1,18-dicarbomethoxyocta-decane did not show the antiwear behavior typical of sulfurized methyl undecenoate. Organic sulfides—-di-n-octyl monosulfide, di-n-octyl disulfide, di-n-octyl tetrasulfide, di-sec-octyl disulfide, d-t-octyl disulfide—behaved much differently than sulfurized methyl undecenoate. A mixture of methyl laurate and di-sec-octyl disulfide showed the same kind of antiwear behavior as sulfurized methyl undecenoate.

The Slow-Speed Frictional Behavior of Some Lubricant Additive Type-Substances

The slow-speed frictional behavior of white oil solutions of stearic acid and of lauric acid was found to be in accord with established concepts of film formation and in quantitative agreement with reliable results already in the literature. The shape of the speed-dependent friction function of decalin solutions of triphenyl phosphate and of diphenyl phosphate was similar to that for the fatty acids, but numerically the coefficients of friction for the phosphate esters were higher. There was evidence for both an acidity effect and a film effect in the action of the phosphates. Di-t-octyl disulfide, di-t-octyl tetrasulfide and t-octyl chloride were associated with stick-slip friction only. The relation between antiseizure in extreme-pressure lubrication and the frictional behavior for these substances is discussed. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Lubrication Conference held in Houston, Texas, October 14–16, 1969

The Load-Carrying Properties of Metal Dialkyl Dithiophosphates: The Effect of Chemical Structure

The extreme pressure (e.p.) and mixed lubrication or antiwear (a.w.) properties of a range of metal dialkyl dithiophosphates have been examined using the four ball machine. The results show that the nature of the metal atom is a major factor in determining these properties, and that the factors governing e.p. and a.w. activities are different. Thus the order of decreasing e.p. activity is Bi(III) > Ag(I), Pb(II) > Sb(III), Sn(II) ≥ Cd(II), Fe(III), Ni(II) > Zn(II), whilst the order of decreasing a.w. activity is Cd(II), Zn(II), Ni(II) ≥ Fe(III) > Ag(I) > Pb(II) > Sb(III), Sn(II) > Bi(III) for a series of 4-methylpentyl-2 and n-hexyl salts. The nature of the alkyl group has a lesser effect on either e.p. or a.w. properties. Possible explanations for these results are presented.

Load-Carrying Properties of Metal Dialkyl Dithiophosphates: Application of Electron Probe Microanalysis

The surface topography and the nature of the surface layer of wear scars obtained with Bi(III), Pb(II), Cd(II), Ni(ll), and Zn(II) di-(4-methylpentyl-2) dithiophosphates, using the four-ball machine, have been studied using an electron probe microanalysis (EPMA) technique. The results show that the nature of the dithiophosphate markedly affects the surface topography, element content, and distribution of the wear scar in both the extreme pressure and mixed lubrication or antiwear regions. The implication of these EPMA results on the load-carrying mechanism of metal dialkyl dithiophosphates is discussed.

Paper 11: Lubrication of Involute Gearing

This paper appraises the last ten years' work in the field of gear lubrication. The problems associated with the application of the critical temperature hypothesis to lubricant failure are discussed. Engineering characteristics of extreme-pressure lubricants are defined and illustrated.

Iodine as an extreme pressure lubricant additive

Iodine charge transfer complexes have been investigated as lubricants for stainless steels and low carbon steels. These complexes, either by themselves or as additives to hydrocarbon oils, function as effective boundary lubricants over a wide range of surface pressure. The addition of as little as a fraction of one per cent iodine, in the form of a charge transfer complex, to a hydrocarbon oil increased its load carrying capacility by a factor of almost one hundred and markedly reduced the wear. The effect of iodine concentration on both friction and wear has been evaluated for a number of steels. Preliminary experiments indicate that iodine complexes also function as good boundary lubricants for nickel, babbitt, and cobalt. The mechanism of lubrication appears to be the reaction of iodine with the wearing metal surface to form a metal diiodide, a lamellar solid having a crystal structure similar to molybdenum disulfide.

Radiotracers Reveal Activity of Extreme-Pressure Additives in Lubrication

The mechanism of extreme-pressure (EP) lubrication has been studied with various approaches in a number of laboratories over the past years. An investigation in this area was initiated recently in this laboratory with a modified four-ball tester [Manteuffel and Wolfram, ASLE Trans. 3, 157] wherein the lubricant temperature leaving the ball interfaces is recorded as the load is continuously increased. The patterns of the temperature-load curves generated under these conditions are dependent on the lubricant compositions. This investigation has now been extended with radiotraced phosphorus and sulfur to study the comparative reactivities of these elements in EP lubrication and as functions of temperature and load. A procedure was devised to measure the contents of the radiotraced elements in the ball scar area surfaces. The results indicated that phosphorus is much more reactive than sulfur in the EP lubrication. The data also confirmed that the lubrication reaction is very temperature-dependent. The phosph...

Role of Extreme Pressure Lubricants in Boundary Lubrication and in Metal Cutting

REBINDER et al.1 have examined the effects of surface-active agents such as mineral oil solutions of oleic acid to alter the creep and fatigue character of metals. Observed changes are attributed to the adsorption of oleic acid by the metal, thereby hastening the strain-hardening of the metal's surface.

Chemical changes in steel surfaces during extreme pressure lubrication : D. Godfrey. ASLE Trans., 5 (1962) 57–66, Discussion p. 64–65; 3 figs., 3 tables, 47 refs.

Chemical changes in steel surfaces during extreme pressure lubrication : D. Godfrey. ASLE Trans., 5 (1962) 57–66, Discussion p. 64–65; 3 figs., 3 tables, 47 refs.

Extreme pressure lubrication and wear. The chemical reactivity and the extreme pressure action of two aliphatic disulfides : A. Dorinson and V. E. Broman. ASLE Trans., 5 (1962) 75–90, Discussion p. 89–90; 18 figs., 3 tables, 17 refs.

Extreme pressure lubrication and wear. The chemical reactivity and the extreme pressure action of two aliphatic disulfides : A. Dorinson and V. E. Broman. ASLE Trans., 5 (1962) 75–90, Discussion p. 89–90; 18 figs., 3 tables, 17 refs.

Extreme Pressure Lubrication and Wear. The Chemical Reactivity and the Extreme Pressure Action of Two Aliphatic Disulfides

Reaction rates were studied for the action of di-tert-octyl disulfide and di-n-cetyl disulfide in white oil on iron powder over the temperature range 165–250 C. The data were fitted to the Arrhenius equation, and the tertiary disulfide was found to be 1500 times as reactive as the normal disulfide. White oil solutions of the two disulfides were subjected to the Falex test and to the four-ball extreme-pressure test, and the tertiary disulfide was found to be the more effective lubricant additive in these tests. Wear studies were carried out with a pin and disk apparatus under conditions which approximated the above bench tests as regards specimen material, rubbing speed and pressure. The complex nature of the course of wear made it difficult to compare the two disulfides quantitatively. It was found that the tertiary disulfide was 2 to 20 times as efficacious as the normal disulfide in reducing the terminal steady-state wear rate. By treating the additive action of the disulfides as a competition between t...

Chemical Changes in Steel Surfaces During Extreme Pressure Lubrication

Films and wear fragments from unfailed test cups from SAE extreme pressure runs with sulfurized mineral oil and films from unfailed hypoid gear teeth run in commercial gear oils were analyzed by six methods. The major compound was Fe3O4 or a similar spinel. Minor constituents were FeS, FeO, and an “iron carbide.” Emission spectrographic analysis showed silicon in much greater concentrations than in the base metal. The beneficial effects of silicon enrichment are discussed and the mechanisms that might cause it to concentrate in the surface, Bench test data are given demonstrating how poly (methylphenylsiloxane) can increase the load-carrying capacity and reduce the wear of gear oils.

Extreme-pressure lubrication and wear. The influence of rubbing speed on metallic wear at two contact pressures : A. Dorinson and V. E. Broman. ASLE Trans., 3 (2) (1960) 176–183; 9 figs., 2 tables, 4 refs

Extreme-pressure lubrication and wear. The influence of rubbing speed on metallic wear at two contact pressures : A. Dorinson and V. E. Broman. ASLE Trans., 3 (2) (1960) 176–183; 9 figs., 2 tables, 4 refs

Extreme-pressure lubrication and wear. The influence of contact stress on metallic wear : A. Dorinson and V. E. Broman. ASLE Trans., 3 (2) (1960) 165–175; 14 figs., 4 tables, 5 refs

Laminated lithium-ion polymer cells with gel electrolytes and laminate-film package are expected to replace the conventional alkaline batteries for space application due to their high energy density and high flexibility in configuration. To facilitate this, we assessed the effect of operation conditions, charge rate and taper voltage, on cycle-life testing of commercial lithium-ion polymer cells by simulating a satellite's LEO operation with 40% DOD profile in this work. So far, 6000 cycles have been completed. A lower charge rate was found to be promising for long-term satellite operation. Impedance analysis disclosed a little change in cell internal impedance with charge rate. This encouraged us to attribute the poor cycling performance at high charge rate to excessive lithium-ion exhaust in electrode surface-film formation due to a longer holding duration at taper voltage. The taper voltage was also found to affect charge performance of lithium-ion polymer cells. Good cycling performance, such as the minimum current at the end of the charge and the maximum voltage at the end of the discharge were observed when using taper voltage range from 4.05 to 4.10 V. Theoretical analysis deduced that low current at the end of the charge correlated to (1) a low cell internal impedance and (2) a large slope in the capacity–voltage charge curve measured at a low rate. We further evaluated cell cycling behavior at a low rate and indeed observed the largest slope of capacity–voltage charge curve at voltages ranging from 4.05 to 4.10 V.

Lubricant behaviour in concentrated contact. The effect of temperature : F. W. Smith (National Research Council of Canada) NRC Mechanical Engineering Rept. MP-17, August 1960. 13 pp.& illus

Experiments are described on the frictional behaviour of a petroleum oil in the contact zOne between a steel roller ~nd an aluminum one at 23° C and between steel rollers and between tungsten carbide rollers at 23°C, 100°C and 190°C. The coefficient of sliding friction decreases with increasing temperature. Qualitatively, this is taken to indicate that the frictional force represents the shearing of a thick plastic film of lubricant; quantitative agreement between experiments with steel and with carbide rollers is poor. To explain disaccord with other experiments in which the coefficient of friction increases with increasing temperature, it is proposed that mechanical instability of the lub ri cant film may be a factor in extreme pressure lubrication. On general physico-chemical grounds, it is suggested that an intermolecular sliding process occurs at a shear plane in typical concentrated contact lubricant films at low temperature and high stresses. The relationship between such shear-plane processes and the Ree-Eyring theory of non-Newtonian viscosity is discussed.

Extreme pressure lubricants for marine gears : A. D. Newman. Proc. Inst. Mech. Engrs. (London), 174 (5) (1960) 241–246

Extreme pressure lubricants for marine gears : A. D. Newman. Proc. Inst. Mech. Engrs. (London), 174 (5) (1960) 241–246