Study On Wettability Of Two-Scale Array Microstructure Based On WEDM

The excellent properties of superhydrophobic surface provide a feasible way for the protection of metal materials and the expansion of application fields.And studying the influence of multi-scale rough microstructure on wettability in theory can make a great sense in guidance,such as the design and preparation of superhydrophobic surfaces.Due to its special material removal method,the wire electrical discharge machining(WEDM)process has shown significant advantages in the preparation of hydrophobic microstructures on the surface of metal materials.In this paper,a continuous discharge surface topography model of WEDM is established,and the surface roughness of EN-GJL-250(gray cast iron)under different discharge parameters is predicted by this model.The finite element analysis method is used to simulate the distribution of material surface temperature and flow field in the process of single pulse discharge machining,and the crater model of single pulse discharge was established.Based on the random distribution of continuous discharge position,a random function is constructed to determine the discharge position of different machining areas.The surface morphology of the workpiece under continuous discharge is simulated by MATLAB,and the surface roughness is calculated.The accuracy of the prediction model was verified by the continuous discharge experiment of WEDM.The response surface method was used to explore the influence of discharge parameters on surface roughness.The core problem in the theoretical design of superhydrophobic surface is to elucidate the relationship between surface micro-structure and wettability.In this paper,four kinds of dual-scale array microstructures with different shapes are designed.The mechanical equilibrium method is used to analyze the droplets placed on the surface of the smooth array microstructure,and an equation containing the apparent contact angle is constructed.Based on the continuous discharge surface morphology of WEDM,the equivalent geometric model is constructed to calculate the surface roughness coefficient under different discharge parameters.The wetting state of the two-scale array microstructure was comprehensively analyzed,and the prediction model of the apparent contact angle of the two-scale array microstructure was established.The effects of the shape,size and surface roughness of the array microstructure on the wettability were studied.Rectangular,semi-circular,sawtooth and square column array microstructures were prepared on the surface of EN-GJL-250 by HS-WEDM.Superhydrophobic surfaces were prepared by chemical immersion with low surface energy.The effects of array microstructure shape,peak current and pulse width on the apparent contact angle were studied.The accuracy of the apparent contact angle prediction model of dual-scale array microstructure was verified.The average relative error was 7.83 %.