The Self-Ordered Lamellar Texture of MoS2 Transfer Film Formed in Complex Lubrication

In virtue of the porous microstructure and permeability of a novel MoS2 coating constituted of loosely stacked nanosheets, low viscous polyalphaolefin-4 lubricating oil is infused to form a solid-liquid complex lubrication coating. Compared with single lubrication mode, complex lubrication shows noticeable reduction of friction as the friction coefficient is just one-fourth of that for solid coating and half of that for lubricating oil; meanwhile, the load-carrying capability is drastically improved by more than six times and the lifetime is greatly prolonged from 1300 to beyond 16 000 cycles even under the high contact pressure of 0.5 GPa. Detailed microscopic observation and analysis are conducted to explore the reason behind this excellent performance. A thin, coherent MoS2 transfer film is found to cover the whole contact area on counter surface. The high-resolution cross-sectional view further shows there is highly ordered lamellar texture inside the transfer film. Through effective physical adhesion and reorientation, this self-ordered texture plays a key role in lubrication process. It endows the MoS2 with high-performance lubrication irrespective of the initial orientation. Meanwhile, this finding gives evidence that the lubricity of MoS2 strongly depends on the cleavage within the crystallites rather than intercrystallite slip.