The tribological behaviour and application of rare earth lubricants

Abstract

The effects of some rare earth compounds on the resistance and/or the tribological properties of a phenolic/epoxy-resin-MoS 2 bonded solid film, a phenolic/epoxy-resin-MoS 2C (graphite) bonded solid film, a lithium grease, and a lubricating paste were investigated. The action of rare earths as lubricating additives was explored, while the applications of rare earth lubricants were summarized. It was found that the wear resistance of a phenolic/epoxy-resin-MoS 2 bonded solid film was increased by a factor of 1–2 with the addition of rare earth trifluorides, while the corrosion resistance was improved as well. The wear resistance of the phenolic/epoxy-resin-MoS 2 bonded solid film was increased by a factor of 4 with the addition of cerium di-n-butylphosphate, while the corrosion resistance of a phenolic/epoxy-resin-MoS 2C bonded solid film was improved considerably. Moreover, the load-carrying capacity of a lithium grease was doubled by the addition of rare earth trifluorides, while lubricating paste exhibited good lubricity even under 7840 N. The improvement in the tribological properties of rare-earth-containing lubricants can be attributed to the protective action of the rare earth with respect to the substrate and to the fact that the rare earths restrain the oxidation of MoS 2 in the MoS 2-containing bonded solid films.