Effect of Base Oil Viscosity and Anti-Wear Additive of Grease on Rolling Fatigue of Ball Type Linear Motion Rolling Bearing

Abstract

This report confirmed the influence of the anti-wear additive on grease base oil viscosity. When the grease of low base oil viscosity is used for lubricating the linear motion rolling bearing, rolling fatigue life shortens. This fact is not shown in the rating life equation of the linear motion rolling bearing. Meanwhile, the fact is reported that MoDTC(Molybdenum Dialkyldithiocarbamate), one sort of the anti-wear additive, is effective with the bearing supporting rotary motion is reported, and many examples are in practical use. However, MoDTC hastens rolling fatigue life in the linear motion rolling bearing. The Nanoindenter hardness is associated with traveled distance in the linear motion rolling bearing. The anti-wear additive, reducing the hardness of the steel ball, shortens rolling fatigue life of the linear motion rolling bearing. The change of the steel ball hardness cannot be measured by the microVickers hardness. In addition, the change of color of a steel ball in linear motion rolling bearing is caused by the oxidation film. The change of color of the steel ball does not adversely affect rolling fatigue life.