| Solid lubricants are often used for mechanical surface protection in complex and demanding environments,such as spatial film lubrication at macro-scale and micro lubrication in microelectromechanical devices,where they can provide excellent friction and wear reduction.In which,the surface morphology is an important factor affecting the tribological properties of the substrate and the solid lubricant.At the micro-scale,the actual contact will be reduced from millions of asperities at the macro-scale to only a few due to the reduction in contact size and load.The surface roughness and actual contact morphology will play a more significant role in micro-scale.Therefore,it is necessary to investigate the effect of substrate surface morphology on the tribological properties of typical solid lubricants at multiple scales.In this study,Mo S2 solid lubricating coatings were prepared on the surface of 304 stainless steel substrates with different roughness by electrophoretic deposition method.The homemade reciprocating microtribometer was used to evaluate the tribological properties of Mo S2 coatings on substrates with different roughness at micro and macro scales.The morphology and composition of the wear tracks were analyzed.The dynamic sliding process was simulated by ANSYS finite element simulation software,and thus the mechanism of the influence of the substrate’s surface morphology on the tribological properties of Mo S2 coatings was explored.The main research results are as follows:（1）According to the requirements of the assessment conditions of tiny load and short stroke,high-precision and high-reliability components were reasonably selected,and a data processing system was developed based on Lab VIEW.After integrating the hardware and software,a reciprocating microtribometer can be flexibly applied for tribotest at macro and micro scales.It can provide an important experimental foundation for revealing the effect of surface morphology on the tribological behavior of solid lubricants.（2）The surface of 304 stainless steel substrate was polished and grooved to prepare substrates with significantly different surface morphology.And the Mo S2 coating was prepared on the surface of 304 stainless steel substrate by electrophoretic deposition method.According to the results of the characterization of the substrate surface and the coating,it can be found that the deposited Mo S2 coating spreads uniformly and has a porous structure on the substrate surface,and the grooves on the substrate surface were covered by the Mo S2 coating completely.（3）The tribological properties of Mo S2 coatings on substrates with different surface morphologies were evaluated by reciprocating tribotest at the micro and macro scales using a homemade reciprocating microtribometer.Scanning Electron Microscope（SEM）,Energy Dispersive X-ray Spectroscopy（EDS）,and three-dimensional profilometer were also used to analyze the morphology and composition of the wear track surface in order to investigate the mechanism of the influence of substrate surface morphology on the tribological behavior of solid lubricants.The results show that surface-grooved substrates can significantly improve the tribological properties of Mo S2 coatings.This is due to the fact that substrates with rougher surface morphology have better resistance to tangential deformation,can maintain more initial morphology and store Mo S2 lubricant effectively during tribotest,and thus exhibit excellent lifetime.（4）Substrate models with different surface morphologies were constructed.The actual contact area,tangential stiffness,and tangential deformation of substrates with different surface morphologies during sliding at micro and macro scales were simulated by ANSYS finite element simulation software to investigate the contact behavior of substrates with different surface morphologies during sliding.The results show that the substrate with rougher apparent morphology has higher tangential stiffness and less tangential deformation during the sliding process.Furthermore,the effect of the surface morphology of the substrate on the tribological behavior of the surface solid lubricant phase was discussed. |
