Experimental Investigation on the Removal of Recast Layer after EDM Machining

The viability of eliminating the recast layer (RCL) utilizing etching and mechanical grinding for Ni based super alloy materials employing electrical discharge machining (EDM) is investigated in this work. EDM is a widely utilised sophisticated thermoelectric non-conventional machining technology in a variety of fields such as dentistry, medicine, and the materials which is difficult to machine by standard methods. The material is removed by melting and vaporisation, and the energy source for the material removal is heat generated by sparking. Due to improper dielectric fluid flushing, a hard and brittle coating forms on the periphery of the workpiece. If flushing is not done properly, then the molten metal re-solidifies, hardens, and adheres to the machining surface due to the cooling impact of the dielectric fluid. The layer created above the surface is called as RCL. This experiment is divided into three stages. In first stage RCL generation on the workpiece using EDM. In second stage optimizes the RCL removal, using L9 orthogonal array with Taguchi approach and create experimental plan, with different etching parameters. To find the most significant etching parameters, an analysis of variance (ANOVA) was performed. In the third stage, mechanical grinding was used to remove the RCL completely. Finally, the experiment investigates the workpiece metal removal rate and surface roughness value. The most significant parameter for all response characteristics is found to be temperature and acid composition. Metal removal rate and surface roughness value is highly affected with temperature and acid composition respectively.