Research on the microstructure and space tribology properties of electric-brush plated Ni/MoS2–C composite coating

In order to expand the application field of MoS2 lubricant coatings (films) and to improve their adaptability in harsh environments, a Ni/MoS2–C composite coating composed of Ni metallic matrix and two lubricating components was prepared on AISI 52100 steel substrates with a nano electro-brush plating process. The relationship between microstructure and properties of the coating was analyzed via microstructure characterization. The tribological properties of the as-received coating samples and the samples treated in humid air (HA), high vacuum (HV), atomic oxygen (AO) erosion and ultraviolet (UV) irradiation exposure were investigated comparatively. The results show that the surface of the obtained Ni/MoS2–C coating is smooth and clean. The micro and nano MoS2–C grains are dispersed in the Ni matrix homogeneously. The MoS2 and C particles also showed good synergistic effects. The added nano graphite particles not only increased the moisture resistance of the composite coating, but also reduced the residual stress and enhanced the mechanical properties of the coating. The composite coating still showed good lubricating properties after long-duration treatments in HA, HV, AO and UV environments, and the friction coefficients during the stable running periods remained at about 0.1. The influence of vacuum outgassing on the properties of the lubricants is not obvious. The coatings were oxidized slightly by AO, and thus their initial friction coefficients in AO conditions also increased, but the coating still showed good friction reduction properties after a short running-in period. The changes in microstructure and properties of the coating after UV irradiation were also inconspicuous. All test results indicate that the Ni/MoS2–C composite coating has excellent space tribological properties and good adaptability in harsh environments. So it is promising to use Ni/MoS2–C composite coating in a space solid lubrication area.

► A Ni/MoS2–C coating was prepared using a nano electro-brush plating process.
► The microstructure and tribology properties of the coating were analyzed in detail.
► The MoS2 and graphite particles in the coating showed good synergistic effects.
► The coating showed good tribology properties in simulated space environments.