Modeling the Nano Indentation Behavior of Recast Layer and Heat Affected Zone on Reverse Micro EDMed Hemispherical Feature

Abstract

Electrical discharge machined surfaces inherently possess recast layer on the surface with heat affected zone (HAZ) beneath it and these have a detrimental effect on the mechanical properties viz., hardness, elastic modulus, etc. It is very difficult to experimentally characterize each machined surface. Therefore, an attempt is made in this study to numerically calculate the mechanical properties of the parent material, HAZ and the recast layer on a hemispherical protruded micro feature fabricated by reverse micro EDM (RMEDM). In the first stage, nano indentation was performed to experimentally determine the load–displacement plots, elastic modulus and hardness of the parent material, HAZ, and the recast layer. In the second stage, finite element analysis (FEA) simulation was carried out to mimic the nano indentation process and determine the load–displacement plots for all the three cases viz., parent material, recast layer, and HAZ. Results demonstrated that the load–displacement plots obtained from numerical model in each case was in good agreement with that of the experimental curves. Based on simulated load–displacement plots, hardness was also calculated for parent material, HAZ, and the recast layer. A maximum of 11% error was observed between simulated values of hardness and experimentally determined values. This model can be utilized to predict the mechanical properties of surfaces fabricated by micro scale EDM process and this will help in reducing the number of experiments thereby saving time and cost.