A study on the antiwear behaviour of S-P-type gear oil additives in four-ball and falex machines

Abstract

We report the results of a controlled experiment using both Falex and four-ball antiwear tests. The tested oils, containing sulphurized isobutylene (SO) and dibutyl phosphite (DBP), show distinct antiwear behaviour in the two kinds of test. Auger spectroscopy analysis indicates a common antiwear mechanism for the oils in both testers. The different antiwear behaviour is attributed to the effect of the specimen surface temperature on the phosphorus-type additive. It is assumed that at low temperature competing adsorption is the dominating effect for DBP while at higher temperature DBP acts as catalyst for the SO erosion of the friction surface.