The Effect of Adsorption and Molecular Structure of Antiwear Additives on Wear Mitigation

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Abstract
The mechanisms by which antiwear additives mitigate wear in lubricated contacts are not unequivocally known. This study examined the effects of adsorption, sulfur, and steric hinderance on the wear mitigation properties for a series of model antiwear additives. A direct relationship was found between the amount of additive adsorbed and the wear-mitigating properties of that additive. The presence of sulfur, even in a nonreactive form, had a profound effect on reducing microscopic galling and improving surface appearance. Steric hindrance significantly reduced the wear-mitigating properties of the best antiwear additive tested in this study. The results are consistent with a previously proposed model which consists of micro-EHD, antiwear films, and local EP properties in the overall mitigation of wear by antiwear additives in lubricated contacts.