Chemical Effects of Lubrication in Contact Fatigue—Part III: Load-Life Exponent, Life Scatter, and Overall Analysis

Abstract

A brief review of relevant literature is presented with the logic underlying the selection of lubricant base stocks, additives, materials, surface textures, and other variables used in contact fatigue tests under rolling-sliding conditions. Tests of selected combinations (mineral oil with and without a zinc dialkyldithiophosphate additive and a polyolester synthetic with and without its typical additive package) showed that lubricant chemistry affects the stress/life slope and the Weibull slope (scatter in life). Results of the overall program show that the relative contact fatigue life for different lubricant chemistries should be evaluated using operating conditions, especially stress and slip levels, near to expected application conditions.