Lubricant additives, friend or foe: What the equipment design engineer needs to know

Lubricant formulations and lubricant additives have been slanted heavily toward protecting gear concentrated contacts from galling and wear. Much of the performance differentiation of these lubricants has been dependent on highly accelerated standardized laboratory testing. The area of contact fatigue has played a less important role in shaping lubricant formulations, but new test results for several commercially available gear lubricants suggest this area warrants a closer examination. The performance effects of fully and partially additized lubricants were studied using standard bearing industry rolling contact fatigue and wear testing procedures for tapered roller bearings. These test results indicate significant detrimental effects to wear, and fatigue life performance can occur with some additized lubricant formulations. Observations of functional surfaces, before and after testing, are made and examined for several lubricant formulations. The implications of these findings for equipment applications are discussed, and suggestions are made for ways to minimize or avoid potential detrimental performance effects. 10 refs., 11 figs., 3 tabs.