Effects of additives on wear mode and morphology of wear debris generated in the lubricated sliding of steel

The predominant wear mechanisms were studied as a function of contact pressure and sliding velocity in thin-film-lubricated sliding under conditions of concentrated contact with a hard chromium steel ball from the view point of additives. Three kinds of lubricants were used in this study: (1) alkylnaphthalene oil (base oil), (2) base oil plus 0.044 wt.% stearic acid and (3) base oil plus 1.0 wt.% tricresyl phosphate (TCP). The results were arranged in the form of a wear mode diagram. The effects of additives on the diagram and morphology of wear debris generated in each wear mode regime were studied and discussed. It was found that additives contributed to the ability to achieve mild flow wear. The degree of contribution was as follows: TCP > stearic acid > base oil. The shape of wear debris generated did not depend on the kind of additive in each wear mode regime; however, the size was strongly dependent on the kind of additive.