Surface Flattening of Directed Energy Deposited Parts through Jet Electrochemical Machining

Abstract

For additive manufacturing (AM) processes, post-processing is usually needed before application, and electrochemical machining is considered a promising candidate for this purpose. Here, the possibility of using jet electrochemical machining (Jet-ECM) as a semi-finishing post-processing for directed energy deposition (DED) was investigated. The main purpose is to flatten the wave-like surface and improve dimensional accuracy. First, polarization, EIS, and current efficiency measurements were conducted, and it was found that the electrochemical dissolution behaviors of the DED-produced Inconel 718 alloy in NaNO3 solution were isotropic and irrelevant to the DED parameters, which can be attributed to the effect of the passive film. Pa and Pz values from the primary profile were considered more suitable than surface roughness for the characterization of the surface flatness. In the Jet-ECM experiments, the small inter-electrode gaps and high applied voltages were found to be beneficial to surface flattening, while the influence of the scanning speed was not evident. Multiple reciprocating scans could further improve the surface flatness, but most of the improvements were obtained in the first scan. This demonstrates the great potential of Jet-ECM in the post-processing of AM parts, and provide several essential guidelines for further researches.