Additive influence on wear and friction performance of environmentally adapted lubricants

In this paper, the influence of concentration level and chemical compositio n of three different additive types on friction and wear coefficient are pr esented for a synthetic ester base fluid and a mineral base oil. One extrem e-pressure (EP), two antiwear (AW) and two yellow metal passivator (Cu-pass ivators) additives were used. Factorial experimental design was used as the basis for a systematic evaluation of wear rates under mixed and boundary l ubrication conditions. A total of 33 different lubricant blends were tested in a Plint and Partner High Frequency Friction Machine. For the synthetic ester, the extreme-pressure (EP) additive, containing phosphorus and nitrog en, was found to be much more effective in reducing wear than either of the two antiwear (AW) additives tested. In fact, the AW and Cu-passivator addi tives made little or no contribution to the wear protection in most of the cases studied. A synergy effect between the three additive combinations was observed only for the reference mineral oil blend. A significant differenc e between the antiwear performance of the test lubricants was found. This s tudy suggests that the traditional "AW" and "EP" labels associated with com monly used additives are poor aids when designing of ester based lubricants . (C) 2001 Published by Elsevier Science Ltd.