Masuhiko Kawamura

Antiwear property of lubricant additives for high silicon aluminium alloy under boundary lubricating conditions

Abstract The antiwear effects of phosphates, phosphites and zinc dialkyldithiophosphates (ZnDTPs) were examined by the use of a cross-pin-type lubricant tester for a high silicon aluminium alloy under boundary lubrication conditions. The reactivity of the additives with metals was studied by differential thermal analysis. Phosphates and phosphites containing straight chain alkyl groups showed smaller wear scar diameters than those containing branched or aryl groups. The reactivity of the additives did not correlate with the antiwear property. The results suggest that the oiliness effect is a dominant factor. ZnDTPs showed good antiwear properties, which may be attributed to the adsorption of the additives or the formation of a friction polymer.

Organic sulphur and phosphorus compounds as extreme pressure additives

Abstract The chemical reactivity with iron of sulphur-containing or phosphoruscontaining extreme pressure (EP) additives was investigated using differential thermal analysis (DTA). The lubrication properties of the EP additives were examined with a cross-pin-type lubricant tester. The chemical reactivity of the EP additives correlates with the wear properties. Sulphur compounds may be classified into four groups according to the reactivity estimated by DTA. The wear scar diameter increased with increasing additive reactivity. The reaction products corresponding to individual DTA peaks indicate that wear properties are controlled by the type of reaction product. When phosphites are used the wear scar diameter decreases linearly with increase in the reaction starting temperature while when phosphates are used the scar diameter shows little variation: the reaction starting temperature has no effect. Study of the molecular structure of the additives indicates that the difference between wear properties of phosphites and phosphates may be due to their adsorption abilities.

The correlation of antiwear properties with the chemical reactivity of zinc dialkyldithiophosphates

Abstract The chemical reactivity of zinc dialkyldithiophosphates (ZnDTPs) with iron was investigated using differential thermal analysis (DTA). The antiwear property was examined with a cross-pin-type lubricant tester. The types of alkyl groups in the ZnDTPs were identified by DTA. With primary alkyl ZnDTPs, an exothermic peak was observed, corresponding to the formation of FeS. The wear scar diameter increased with increase in peak height. Corrosive wear may be a dominant factor. With secondary alkyl ZnDTPs, an endothermic valley and an exothermic peak were observed at temperatures near 200°C. No reaction product was detected beyond the valley and the peak. FeS was detected as a reaction product at the second exothermic peak, which was observed at a higher temperature than those of the valley and the peak. The wear scar diameter decreased with increase in the height of the second peak. Secondary alkyl ZnDPTs may behave as non-sacrificial extreme pressure additives.

Deterioration of antiwear properties of diesel engine oils during use

Abstract A systematic investigation has been made to clarify the causes of deterioration of the antiwear properties of diesel engine oils during use. Adsorption of the antiwear additives on soot intermixed in the oil was examined using solvent-less paper chromatography. Little adsorption has been detected and may not affect the increase in wear. The soot was observed using a transmission electron microscope with a freeze fracture replica method. Most soot disperses well in the oil as small aggregates of a few particles. The results of the lubrication tests indicate that the small aggregates have no effect on the increase in wear. In some cases, large aggregates of the soot were observed. From the analytical results, the large aggregates contain decomposition products of the additives which behave as a binder for the soot. The large aggregates can intrude between the sliding surfaces and may cause abrasive and/or corrosive wear.

THE LUBRICATING PROPERTIES OF USED ENGINE OIL

Abstract The lubricating properties of oil samples from four cars using either leaded or unleaded gasolene were examined using a cross-pin-type lubricant tester and a JIS four-ball tester. The zinc dialkyldithiophosphate (ZnDTP) content in the oil samples was determined by thin layer chromatography (TLC). The wear scar diameter increased with running distance up to 2000 km. At running distances above 2000 km, the wear scar diameter decreased for oil from cars using unleaded gasolene but increased for oil from cars using leaded gasolene. The load-carrying capacity also varied depending on the type of fuel used. The TLC spot characteristic of ZnDTP disappeared after running distances of 3000 km with both fuels. However, another spot, characteristic of lead dialkyldithiophosphate (PbDTP), appeared below the ZnDTP spot for oil from cars using leaded gasolene. These results indicate that the differences in the lubricating properties of oils from cars using leaded and unleaded gasolene are due to the formation of PbDTP.

The antiwear property of zinc dialkyldithiophosphates in used engine oils

Abstract The change in the lubrication properties of vehicle engine oils with driving distance was studied by using a cross-pin type of lubricant tester and a Fourier transform IR spectrometer. The effect of the thermal decomposition of zinc dialkyldithiophosphates (ZnDTPs) on their antiwear property was also examined. The amount of the ZnDTP in engine oil decreased and the amounts of the decomposition products increased with increasing running distance but a good antiwear property was still observed. After 60 h of heating at 135°C, the ZnDTP in sample oils had decomposed into a precipitate and the antiwear property of the oil had deteriorated. With sample oils containing ZnDTP and a detergent or a dispersant, the decomposition products dissolved in the oil and the antiwear property was maintained even after 80 h of heating. The results suggest that the decomposition products of ZnDTPs have a good antiwear property and that the good antiwear property of the used engine oils was retained because of the solubilization of decomposition products into the oil with the aid of a dispersant or a detergent.

A Cold Forging Oil Containing Phosphorus Type EP Additives

The galling prevention property of oils containing oleyl acid phosphate (OLAP) and/or phosphoric acid has been investigated. A synergistic effect was observed with the oil containing these two additives. Heat-treatment was found to effectively enhance the galling prevention property of the oil. Surface analyses showed more phosphate formed on workpiece surfaces after the tests, using the oils with superior galling prevention property. Oil analyses suggested that OLAP, phosphoric acid and water associated to form molecular aggregates, and that the association between OLAP and phosphoric acid was promoted by heat-treatment. An oil with the highest, chemical reactivity and galling prevention property was obtained by the addition of the two additives to the base oil, followed fry heat-treatment at 120°C for one hour with stirring. The pretreatment of the workpieces in this oil further increased the galling prevention property due to the effect of phosphate films preformed on the. workpiece surfaces. Presented...

The Mechanism of Synergism Between Sulfur- and Phosphorus-Type EP Additives

A synergistic effect was observed for systems of phosphites and sulfur-type additives, while no interaction was observed for systems of phosphates and sulfur-type additives. The mechanism of synergism was studied by EPMA, FT-IR, GC-FPD, and MS. From a synergistic mixture, a new compound containing phosphorus and sulfur was detected. The new compound which was separated by distillation showed good antiwear properties comparable with the synergistic system and was identified as a thiophosphate. The synergism between the sulfur-type additive and phosphite may be caused by the formation of thiophosphate. The chemical reaction between them is discussed and a reaction formula is proposed. Presented as an American Society of Lubrication Engineers paper at the ASLE/ASME Tribology Conference in Atlanta, Georgia, October 8–10, 1985

Change of ZnDTP in Engine Oils During Use

Modifications du dialkyldithiophosphate de zinc dans les huiles de moteur pendant le fonctionnement

Evaluation of galling prevention properties of cold-forging oils by ball penetration test

Abstract A ball penetration test has been devised as a new laboratory-scale cold-forging test for determining the galling prevention properties of lubricants. The galling prevention properties of cold-forging oils were clearly classified by this test. After the tests, various reaction products were detected on the workpiece surfaces. The oils with higher reactivity exhibited superior galling prevention properties. The order of performance as determined by the ball penetration test correlated well with that determined by the backward can extrusion test, which is generally recognized as a standard cold-forging test. Moreover, the ball penetration test requires no tedious test procedures, in contrast with conventional cold-forging tests. Judging from the results obtained, the ball penetration test is effective as a means of evaluating the galling prevention capacity of cold-forging oils adequately and easily.