Effect of Lubricant Additives on Scoring-Proof Capability of Gear Oils

Abstract

Scoring-proof capability and frictional characteristics of oils containing solid lubricants such as molybdenum disulfide and graphite, a S-P-type EP additive and organomolybdenum compounds such as MoDTP and MoDTC were evaluated using atwo-roller machine under a step load condition. In the case of the addition of molybdenum disulfide or graphite, scoring load and frictional conditions, such a scoefficient of friction, surface temperature and the state of oil-film formation, were similar to those of the base oil in which those additives were not added. The addition of the S-P-type EP additive and the organomolybdenum compounds improved the scoring limits. These improvements can be attributed to the formation of substances which inhibit the occurrence of scoring. The substance is insulating and has a high coefficient of friction in the case of the S-P-type EP additivt, while it is conductive and has a low coefficient of friction in the case of organomolybdenum compounds. Two diagrams of the surface temperature-friction coefficient and insulating voltage-friction coefficient clarified the effects of these additives.