| As we all know,wettability of surfaces with a liquid in air is an significant property of the surface of the material,which is closely related to the physical and chemical processes on the surface of related materials such as adsorption,lubrication and friction.Due to its high energy density,high precision,and no macroscopic cutting forces,Electrical Discharge Machining(EDM)technology occupies a central position in the processing of materials and parts with high melting points,high hardness,high strength,and complex topography.And the EDM surface is formed by discharge pits,random and disordered,which is a periodic microstructure of different and traditional machined surfaces.Therefore,the wetting of its surface is complicated.Until now,only a small amount of experimental research has been reported and no relevant theoretical research has been done about it.Therefore,in this paper,the surface morphology of beryllium copper alloy(C17200)was studied in detail through a series of characterization methods.Based on this way,a theoretical model of surface wettability of EDM and a surface wettability evaluation system were established,which can predict the wetting characteristics.And the correctness and effectiveness of the theoretical model and the evaluation system were verified through experiments.In this paper,the surface prepared by different EDM processes was analyzed,and the characteristics of uniformity in surface topography were dug out firstly.Then it is easy to see that the surface bulge has a certain similarity with the specific curve by observing the topography of the EDM milling surface,which can be measured by using AFM and other measuring instruments.After that,a mathematical analysis method was used to construct a theoretical model of the surface topography,and three characteristic parameters were defined according to the requirements of the model.Then further research was taken,which performed parametric extraction of the actual surface topography,and finally a theoretical model of surface morphology of EDM is established.The definition and theoretical model of wettability are studied,and the quantitative relationship between apparent contact angle and dynamic contact angle of superhydrophobic surface is established in this paper.This paper analyzes the effects of multi-scale structures,different micro-morphologies,and combinations of various wetting states on wettability in view of surface morphology characteristics of EDM machining.And the quantitative relation between wettability and surface morphology was established by the structural parameters of the three-dimensional model.What's more,a primary and secondary wetting model was established for the EDM milling plane and the EDM array structure according to this quantitative connection.This paper analyzes the influence of the capacitance and resistance of the RC power supply on the wettability of the machined surface.The basic process test of the wetted surface of the beryllium copper material is performed by an EDM milling machine.Considering that the process rules and the wettability model requirements for data processing respectively,beryllium copper surfaces with different wettability were prepared and the theoretical values of wettability of the machined surface were obtained.And by comparing the theoretical value with the actual measured value,the first-order wetting model was verified.Finally,the semi-sine model was selected as the basic model for subsequent studies,and the roughness Sq=0.91 ?m was defined as the cutoff value for hydrophilicity and hydrophobicity.An array structure with superhydrophobic characteristics was designed according to the theory of secondary wetting in the paper.By analyzing the super hydrophobic surface of beryllium copper prepared by WEDM,the influence of structural parameters on wettability was obtained and the verification of the secondary wetting model was completed.It is easy to see that the apparent contact angle of the model has good conformity and can correct the dynamic contact angle.Finally,it was found that the prepared surface has better anti-icing performance for the freezing rain application environment. |
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