Study On Preparation And Friction Properties Of Surface Texture Produced By Picosecond Laser Electrochemical Composite Etching

With the development of social economy,modern industry is increasingly pursuing energy conservation and emission reduction,the problems of wear and tear in mechanical systems has received more and more attentions.The surface texturing technology has become a research hotspot in the field of tribology due to its advantages in friction reduction,lubrication improving of the working life of components.Picosecond laser composite electrochemical etching technology is a manufacturing method combining picosecond laser processing and electrochemical etching processing,it can effectively solve the defects of melt and recast layer on the laser processed surface and significantly improve the localization of electrochemical etching.Therefore,this composite technology has obvious advantages and wild application prospects in the preparation field of friction pair surface texturing.Aim at the facts that surface texturing mostly adopts a single processing,this dissertation applied picosecond laser composite electrochemical etching processing to the fabrication of the surface texture on aluminum alloy,experimented and tested the friction properties of textured surface prepared by composite processing.The main research contents and results are as follows:1.The processing and material removal principles of the composite etching technology were studied.According to the thermodynamic and electrochemical effects of composite etching processing,it studied the thermal-force effects of picosecond laser and electrochemical effects during the composite process,analyzed the coupling of laser and electrochemical,including the enhancement on electrochemical reaction caused by the thermal and force effects of laser and the influences of electrochemical reaction on the thermal and force effects.The results indicated that the laser thermal and force effects work together with the electrochemical effect to improve the composite etching efficiency and machining quality on the surface.2.The experimental system of picosecond laser composite electrochemical etching processing was constructed and the composite etching experiments were conducted.It textured the micro-dimples and micro-grooves on the surface of aluminum alloy and analyzed the influences of laser power,laser repetition frequency,laser scanning speed and laser scanning numbers on the processing results,the surface topography of composite etching processing and picosecond laser processing were compared.It revealed that the composite processing could effectively improve the melt and recast layer on the laser-textured surface,the preparation of surface micro-texture with high processing precision and good surface quality can be realized by reasonable composite processing parameters.3.Based on the Reynolds equation,the mathematical model of fluid dynamic pressure lubrication of dimple texture was established and numerical simulation was carried out.The effects of lubricating medium viscosity,dimple diameter and dimple depth on the bearing capacity of lubricating oil film were investigated.The results show that the larger viscosity lubricant medium and the smaller aspect ratio pit texture can increase the bearing capacity of the lubricating film and improve its hydrodynamic lubrication performance.4.The friction and wear experiments were carried out to verify the surface friction properties of the dimple and groove textures.The effects of dimple diameter,dimple depth,dimple area density,groove width and groove area density on the surface friction coefficient were analyzed.The results show that the dimple and groove texture on the specimen surface were able to effectively improve the surface lubrication and antifriction performance.The variations in geometric parameters of dimples and grooves would affect the surface friction coefficient.Within the parameter of the experiment,compared with a smooth surface,the friction coefficient of a dimple texture with an area density of 15%,a depth of 30 μm and a diameter of 120 m could be reduced up to 27%.Besides,the friction coefficient of a groove texture with an area density of 30%,a depth of 10 μm and a width of 130 μm could be reduced up to 38% as well.There would be an optimum area density for both the dimple and groove to minimize the surface friction coefficient of the specimen,and the optimum value varies with the friction condition.The results of this paper provided experimental verification and research basis for the application of picosecond laser composite electrochemical etching processing to the preparation of surface texture.