Influence of Magnesium Stearate as Lubricant Additive on Fretting Wear under Oil Lubrication

INTRODUCTION There is concern regarding the fretting wear of rolling bearings used in various types of machines, especially those that oscillate minutely. Because fretting wear results in the deterioration of the acoustic properties of bearings, rise in the bearing torque, and flaking originating from wear scar, fretting wear has a negative impact on the performance of rolling bearings. Maruyama et al. [1] conducted fretting wear experiments using lubricating oil containing no additives, and found that fretting wear could be reduced by using high-viscosity oil when the amplitude of oscillatory motion increased. Lubricants used for rolling bearings, on the other hand, contain various types of additives such as extreme pressure additives, oily formulations, and antioxidants. However, little is known about the effects of additives on fretting wear. The research described herein involved a study of the effects of magnesium stearate for reducing fretting wear. Specifically, the mineral oil (VG32) containing magnesium stearate, which was heated to 160 °C for 500 h or more, could reduce fretting wear, comparing with the oil without additives. Moreover, the heat-resisting property of lubricant also could be improved by using this additive.