Numerical simulation of the influence of fluid motion in mushy zone during micro-EDM on the crater surface profile of Inconel 718 alloy

The micro-EDM, due to its ability to machine any electrically conductive material, has been one of the preferred manufacturing methodologies for machining difficult to machine materials. The micro-EDM is a thermal energy-based material removal process where the material removal occurs by spark erosion. In majority of the modeling associated with micro-EDM, the effect of the fluid motion in the liquid and mushy phase of the workpiece alloy is not considered. This paper aims at numerically simulating the crater surface profile formed on Inconel 718 incorporating the effects of material movement in the mushy zone using micro-EDM. Navier–Stokes equations were used as the governing equations. Temperature-dependent specific heat, thermal conductivity, density and viscosity were incorporated, in three ranges, i.e., solid ( T < 1523 K ), liquid ( T > 1609 K ) and mushy ( 1523 K < T < 1609 K ). The mushy zone properties were calculated using enthalpy porosity method, and the properties were updated after each iteration. Specific boundary conditions like Gaussian distributed heat flux on the top surface, fixed percentage of heat to the anode and Marangoni stress on the top surface of the workpiece were applied. The simulations were performed using CFD package ANSYS 15.0 FLUENT for three distinct voltages 100, 125 and 150 V, keeping capacitance constant at 0.4 μ F . User-defined functions were written in C language to incorporate the temperature-dependent properties and the boundary conditions. These simulated results were compared with the experimental values at same input condition, and the maximum calculated deviation in crater profile prediction was less than 14%.