Lubricant and Ball Steel Effects on Fatigue Life

Pitting of rolling contact bearings has been generally considered to be a metallurgical problem since it is a metal part that fails. However, both the physical and the chemical properties of the lubricant have been shown to affect fatigue life. To further study interactions between the ball steel and the lubricant, 4 ball fatigue data were obtained with base oils (25–30 cs at 210 F) and additive-treated lubricants using seven different alloy steels. Both the magnitude and direction of additive effects as well as the magnitude of the base oil viscosity effect on fatigue life were found to depend on the ball steel. The nature of the surface reaction products formed appears to be the principal factor controlling the effect of lubricants on fatigue. These results show that the steel and the lubricant must be considered together to obtain maximum life.