Some Investigations on the Influence of Particle Size on the Lubricating Effectiveness of Molybdenum Disulfide

In trying to clarify the effect of particle size on the lubricating effectiveness of molybdenum disulfide, extensive tests with different MoS₂ powders and MoS₂ suspensions have been run. Because many of the test results available were obtained with the four-ball tester, these tests were also accomplished mainly with this machine, in order to provide a comparison. As a result, it was found that using larger MoS₂ particles at increasing loads, the wear rate also increased. With finer particles at aggravating sliding conditions, the lubricating effectiveness was improved. This result may be explained in that at a given concentration, finer particles more easily will form a complete and continuous film than coarser particles, because there are more particles available. But the temperature, the materials and, especially, the roughness of the surfaces of the sliding parts must be taken into account, in order to transfer these results to other conditions.