Study On Laser Electrodeposition Composite Preparation And Lubrication Mechanism Of Functional Micro-nano Structures

In the daily operation of industrial equipment,the friction,wear,and lubrication of various motion pairs directly affect the performance such as function,efficiency,and service life of the equipment.As an effective means to improve lubrication,reduce wear,and enhance load-bearing capacity,functional textured surface has received widespread attention from scholars.Abundant micro/nano textured surfaces in nature have surpported references for the design of functional textured surfaces.Meanwhile,researches have shown that the wetting performance of surface has a significant impact on the adhesion,corrosion,wear and other properties of the contact interface.However,current researches on antifriction textures mainly focus on the oil and chip storage performance of the textures,and researches on superoleophobicity mainly focus on hydrophobicity,oil repellency,and anti-corrosion performance of the surfaces.The combination of super wetting property and texture lubrication can further enrich and improve the hydrodynamic lubrication theory and technology,and also provide new ideas for texture antifriction lubrication.This dissertation uses laser-electrochemical composite processing to prepare functional micro/nano composite structures,and conducts intensive research on their tribological properties under different wetting performance conditions.The main work and research achievements are as follows:（1）The thermal mechanism of picosecond laser etching on copper surface and reliable prediction of machining accuracy for micrometer structures.The thermal conduction mechanism of picosecond laser etching on copper was studied,and the prediction and controllability of machining scale of micro pyramid was realized.The results indicate that the processing of picosecond laser etching on copper is neither a complete thermal equilibrium ablation nor a complete"cold processing".Although this process can be regarded as direct solid evaporation or solid plasma evaporation,there is still a liquid phase transition inside the material.With the response surface method,it was found that the response surface model is effective when the effective laser action radius≥the scanning gap,and the reliability of machining accuracy was effectively controlled and predicted.When the effective laser action radius≤the scanning gap,the regression analysis of the response surface model is no longer significant.（2）Multi-level nanostructures electrodeposited on micron structured surface and their mapping mechanism with the superoleophobic properties.With the morphology of micro prisms after laser etching,the electrodeposition process of micro prisms and the influence of crystal modifier(C₂H₁₀Cl₂N₂)on Ni nanocone electrodeposition were studied.Electrodeposition processing parameters were optimized to prepare Ni sub-micro/nano-nano structures,and a mapping relationship between the surface morphology and superoleophobic performance was established.The results indicated that when electrodepositing Ni nanocone on a micro pyramid,the tip effect and the addition of C₂H₁₀Cl₂N₂ cause the elemental Ni ions with high equilibrium potential electrodeposited and grow along helical dislocations at the tip and inclined plane,forming a nanocone;Ni ions with lower equilibrium potential form a coating at the bottom.With studying the mapping relationship between surfaces morphology and wetting performances after electrodeposition,it is concluded that for the superoleophobic micro/nano structures,the current density of sub micron/nano structures should be about 2.5A/dm²and the deposition time should be about 300s in order to form slender and dense primary micro/nano structures;The electrodeposition of nanostructures should choose a higher current density（about 5 A/dm²）and shorter deposition time（about 50 s）in order to grow suitable secondary structures on the basis of the primary structures.And the contact angle（CA）of oil is 153°±2°,with the sliding angle less than 8°.（3）Friction and lubrication characteristics of superoleophobic micro nano structure surface.The effect of superoleophobic micro-nano structured surfaces on the lubrication process of friction pairs was studied,and the mechanism of anti friction lubrication on superoleophobic surfaces was obtained.The results indicate that for superoleophobic surfaces,there are partial solid-liquid-gas contact and interface slip at the interface under oil depletion conditions,resulting in a smaller friction coefficient;Under oil rich conditions,the time-varying effect of superoleophobic has a significant impact on the friction coefficient the vast majority of surfaces initially are solid-liquid-gas three-phase contact,and there is a micro zone air cushion effect at the contact interface,resulting in interface slip and low friction coefficient;As the wear and superoleophobic areas are gradually destroyed,the friction coefficient gradually increases.Under boundary lubrication conditions,the contact between the superoleophobic micro/nano structures and the liquid is a solid-liquid-gas three-phase contact,and there is interface slip and micro zone air cushion effect.The"pump"pushing effect of the micro air cushion pushes a small amount of oil into the small gap between the pins and discs to form lubrication,reducing the friction coefficient;Under hydrodynamic lubrication,the interface at low speed is solid-liquid-gas contact,and the interface slip and micro zone air cushion effect reduce the friction coefficient;At high speeds,the fluid pressure increases and disrupts the Cassie-Baxter state,resulting in the gradual disappearance of interface slip and micro zone air cushion effects,and a gradual increase in friction coefficient.（4）Lubrication characteristics of superoleophobic micro nano structure on the surface of radial sliding bearings.A working condition experimental bench was designed and built to study its lubrication and friction reduction performance under simulated actual working conditions,and the corresponding tribological mechanism was obtained.The results indicated that:At low speeds,superoleophobic structures is not conducive to oil film formation and has a high friction coefficient;After the rotational speed increases,there is a solid liquid gas contact on the surface of the s superoleophobic structures,and the interface slip and micro cavitation effect reduce the friction coefficient and power consumption;After the rotational speed increases to a certain value,the solid liquid gas three-phase contact on the super hydrophobic oil surface changes into solid liquid contact,and the friction coefficient rapidly increases.The research results further enrich and improve the theory and technology of hydrodynamic lubrication,which helps to solve the problems of friction,wear,and lubrication at the interface of motion pairs.It is of great significance for national economic development,environmental resource protection,and the promotion of science and technology.