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The surface microstructure of the surfacing layer was optimized by refining the coarse grains to nanocrystalline by means of pre-loading rolling treatment(PLRT). By using of field emission scanning electron microscope and transmission electron microscopy observations, the microstructural features in the treated surfacing layer were characterized, and processing parameters were optimized. The experimental results show that the obvious plastic deformation layer is formed on the surfacing layer after rolling processing. A uniform refining nanostructured surface layer up to 10μm is fabricated on the surfacing layer. The grain size of the nanocrystalline surface layer is about 10nm. The roughness of PLRTed sample is reduced. The surface residual stress of PLRTed sample change from tensile stress of untreated sample to compressive stress. Analysis shows that the coarse grain of surfacing layer can be effectively refined into nanocrystalline by means of PLRT, and surface physical condition is optimized.

The solid lubrication film containing sulphide was prepared on the surface nanocrystallized surfacing layer by low-temperature ion sulphurizing technology. The microstructure of the sulphurized layer was analysed. The tribological behaviour of the sulphurized layer based on the nanocrystalline layer was investigated in a dry friction condition. The sulphurized layer on the nanocrystalline layer has high sulphide content, with the FeS phase accounting for a large proportion of this layer. The sulphurized layer based on the nanocrystalline layer is thicker and denser and has a significantly lower friction coefficient than the untreated sample, with 25% reduction in wear volume. Analysis demonstrated that the high active nanocrystalline layer is also beneficial for the formation of a sulphurized layer. In addition, the high-hardness nanocrystalline layer provides an excellent support for the lubricating layer and is beneficial for enhancing the antifriction property.