Molybdenum disulfide as a lubricant: A review of the fundamental knowledge

Abstract

This report consists of a review and evaluation of the work presented in the literature over the past 40 years on the behavior of MoS2 as a lubricant. The discussion is concerned with the behavior of MoS2 as a lubricant, its frictional characteristics, the apparent reasons for these characteristics, and the physical and chemical properties which are important to its use as a lubricant.The low friction and easy cleavage of molybdenum disulfide is intrinsic to the material and a result of its crystal structure. Although it is clear that the presence of condensable vapors is not required for molybdenum disulfide to exhibit low friction, as it is in the case of graphite, it is true that condensable vapors play an important role in determining the friction and wear characteristics of a lubricant film of MoS2. The presence of oxidizing agents, particularly water vapor and oxygen, tends to reduce the wear life of the MoS2 film. This is particularly true in the case of burnished films. Although a great deal of knowledge exists concerning the behavior of molybdenum disulfide as a lubricant, there are still voids in our understanding of this subject.