Effect of mechanical action and passive film on electrochemical mechanical finishing

In order to improve the mechanical system performances such as wear resistance and vibration damping behavior, it was focused on the micro-topography of the surface machined by electro-chemical mechanical finishing (ECMF) in this paper. The ECMF was applied in this investigation as a result of it providing more controllable process parameters including the electric potential gradient (EPG), current density, mechanical force, and passive film. The simulation based on the finite element method was applied to analyze the influence of the EPG and the current density on the surface micro-topography under the different magnitudes of mechanical pressure and thicknesses of the passive film. It was shown that the mechanical pressure and the mass percent of the electrolyte which had been controlled are profitable and necessary to gain the feature of arc-like micro-topography on the surface and the growth in material removal rate. The unusual micro-topography of the surface with Ra0.2024μm was finished by using ECMF within 2 min on the condition of 20% NaNO3 electrolyte and 0.2 MPa of mechanical pressure. The investigation on dynamic pressure effect was carried out to confirm the influence of the unusual micro-topography on the thickness in the oil film. The result indicated that compared with the surface machined by fine grinding (FG), the surface finished by ECMF can make an increase in the average film thickness of 3% and a reduction in the square deviation of 46.5%. A discussion was set up to determine the cause of the difference in the results of the experiment. It was shown that the reason for the difference is the distinction in the micro-topography of the surface obtained by ECMF and FG. The micro-topography of the surface finished by ECMF is more favorable to establish a stranger and stable dynamic pressure effect as the result of its fractal dimension, scale coefficient, kurtosis and skewness. The discussion indicated that the finish method impacts the surface topography, and the machining accuracy affects the cross-scale effect of the surface dynamic pressure effect.