Surface Flattening of Directed Energy Deposited Parts through Jet Electrochemical Machining

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 research.

New insights on manipulating the material removal characteristics of Jet-Electrochemical machining through nozzle design

Jet-Electrochemical machining (Jet-ECM) is a novel variation of traditional electrochemical machining in which electrically conductive material is removed through anodic dissolution by means of a fine jet of electrolyte. In this study, the effect of nozzle geometry on material removal characteristics are investigated through physical experiments performed on a Jet-ECM system under development at the university of Manchester. A total of 8 nozzles with holes encompassing converging, diverging and rounded features are studied at flow rates between 0.125 and 0.225 l/min. The results show that the nozzle hole geometry has a significant effect on the machined profile produced due to variations in flow velocity, pressure, and electric current distribution with converging hole nozzles providing an increased depth of cut than the symmetrical cylindrical channel by up to 9.7%. A 2D Star CCM+ simulation is also proposed, and numerical results developed and compared with experimental ones to investigate the feasibility of using simulation to develop future nozzle designs. The simulated results show good profile comparison to the experimental results, however, the model needs developing to improve the process repeatability for future use in nozzle design.

High-performance nickel coating on SLM 316L stainless steel processed by jet electrochemical machining and jet electrodeposition

Selective laser melting (SLM) is an important method in additive manufacturing. SLM has obvious advantages for the fabrication of metal parts with complex structure that cannot be processed directly and are manufactured in relatively low amounts. However, the surfaces of the SLM-formed parts contain more adhesive particles and pores than those manufactured by traditional methods, leading to the poor corrosion resistance of the parts and preventing the widespread use of SLM. To solve these problems, jet electrochemical machining and jet electrodeposition combined processing techniques were investigated for the treatment of the substrate surface in this work. Jet electrochemical machining was used to remove the surface defects of the SLM-formed parts, and the results were compared with the traditional sandblasting and sandpaper grinding surface treatment methods. Then, the nickel coating was deposited on the surface of the SLM-formed parts using jet electrodeposition to protect the surface and extend the service life of the parts. The mechanisms of the different processing techniques were analyzed, and properties such as the substrate morphology, coating morphology, corrosion resistance of the coating, and adhesion of the coating were compared. The results show that holes, adhesive particles and other defects are still present on the substrate surface after sandpaper grinding and sandblasting and affect the quality of the nickel coating. After electrochemical machining, the SLM surface defects were almost completely removed, forming a uniform microporous structure that interlocked with the nickel coating. The coating was smooth and dense and showed the best corrosion resistance and binding force. In 3.5 wt% NaCl solution, the corrosion potential reached −0.196 V, and the maximum binding force reached 35 N.

Optimization of laser-assisted jet electrochemical machining parameters by grey relational analysis and fuzzy logic

Purpose The purpose of this paper is to optimize the laser-assisted jet electrochemical machining parameters, namely, supply voltage, inter-electrode gap, duty cycle and electrolyte concentration during machining of WC-Co composite using grey relational analysis and fuzzy logic. Design/methodology/approach In this work, experiments were carried out as per the Taguchi methodology and an L16 orthogonal array was used to study the influence of various combinations of process parameters on material removal rate, hole taper angle and surface roughness height. As a dynamic approach, the multiple response optimization was carried out using grey relational analysis and fuzzy logic. Findings The process parameters were optimized using grey relational analysis and fuzzy logic for different machining conditions such as balanced manufacturing, high-speed manufacturing and high-quality manufacturing. The research documented in this paper can be scaled up for case studies regarding industrial applications to compare optimization methods for manufacturing processes that are already being carried out. Originality/value An attempt to optimize material removal rate, hole taper angle and surface roughness height together by a combined approach of grey relational analysis and fuzzy logic has not been previously done.