Surface quality improvement using electro chemical machining process for γ-TiAl parts produced by electron beam melting

Abstract

This study aims to improve the surface finish of γ-TiAl AM parts produced via Electron Beam Melting (EBM) process. The sample parts were machined by Electro Chemical Machining (ECM) by changing main variables such as electrolyte type, pulse and feed rate and their effects on the surface qualities are presented and discussed. ECM workshop trials have showed that NaCl type of electrolyte is less effective to machine the material than NaNO3. Additionally, it is also observed that it is unable to remove the sludge (machined material particles) from the workpiece with continuous voltage due to high machining areas (25x25 mm2). Pulsing during the machining process and fresh electrolyte transferred without current pass clean the surface and brighter surfaces are obtained. It is also observed that the higher feed rates above 1 mm/min causes short circuit occurrence between the workpiece and the tool therefore machining time increases, and the material removal rates decreases. Before and after ECM process, EBM part surfaces were measured via an optical profilometer. It was found that the Ra values decreased from 35.39 µm to 3.25 µm in build direction and from 26.73 µm to 2.47 µm in scan direction. The surface roughness is improved by approximately % 91 for both directions. Therefore, it is proposed that ECM is an effective method to be applicable for improving the surface finish of EBM parts surfaces as post-processing.