ABRASIBILITY: Some Experiments with an ASTM Abrasion Tester (Modified)

THE ASTM TENTATIVE TEST METHOD D 1367–55T was designed to test the abrasive quality of different graphites, because it was recognized that such a solid additive for greases could vary considerably in quality. It is a fact that a graphite will show a purity of over 99.9% carbon content while there are grades marketed for lubricating purposes which show impurities as high as 10%. If these impurities are mainly silicious the graphite will be abrasive rather than lubricating. Therefore, care is required in specifying a graphite for lubricating purposes with respect to the nature of the impurities as well as the total content. The ASTM tentative test referred to above takes care of both of these requirements.