Preparation and tribological properties of Mo/MoS2-Pb-PbS composite films

Molybdenum disulfide (MoS2) solid lubricant coating has excellent lubricating properties in harsh space environment, but it has weak film-substrate cohesion which limits the application. In order to further improve MoS2 solid lubrication film's performance and enlarge application range, the Mo/MoS2-Pb-PbS composite film was deposited on 9Cr18 bearing steel by composite process of PVD coating + low-temperature ion sulfide in this study. The single metal (Mo) bonding layer ensures strong bearing capacity, as well as high bond strength between film and substrate. Lubricating surface layer with Mo/MoS2 dispersed Pb (PbS) particles, possesses low shear strength and good plastic deformation capacity. The tribological properties of Mo/MoS2-Pb-PbS composite films in dry air and vacuum (8 x 10(-5) Pa) were investigated by scanning electron microscopy (SEM), energy dispersive spectrometers (EDS) and X-ray diffraction (XRD). The results showed that the composite film's friction coefficient was 0.05 in vacuum when the normal load was 6 N and the sliding rate was 100 rpm. Because transfer film was formed on mating surface, the wear (partly) occurred between transfer film and lubricating film, and Mo/MoS2-Pb-PbS composite film showed good friction-reduction and anti-wear. In particular, the friction mechanism of composite film in vacuum and dry air was analyzed and proposed.

Automated summary

By depositing the Mo/MoS2-Pb-PbS composite film using PVD coating + low-temperature ion sulfide composite process, a strong and lubricating layer was successfully achieved on 9Cr18 bearing steel, solving the issue of weak film-substrate cohesion in molybdenum disulfide solid lubricant coating in harsh space environment. The composite film exhibited good friction-reduction and anti-wear properties in vacuum, with wear (partly) occurring between transfer film and lubricating film due to the formation of a transfer film on mating surface.