Surface finish control by electrochemical polishing in stainless steel 316 pipes

Abstract

Electrochemical machining (ECM) is a non-conventional machining process which is based on the localised anodic dissolution of any conductive material. One of the main applications of ECM is the polishing of materials with enhanced characteristics, such as high strength, heat-resistance or corrosion-resistance, i.e. electrochemical polishing. The present work presents an evaluation of the parameters involved in the ECM of Stainless Steel 316 (SS316) with the objective of predicting the resulting surface finish on the sample. The interest of studying ECM on SS316 resides on the fact that a repeatable surface finish is not easily achieved. ECM experimental tests on SS316 pipes of 1.5" (0.0381 m) diameter were conducted by varying machining parameters such as voltage, interelectrode gap, electrolyte inlet temperature, and electrolyte flow rate. The surface finish of the samples was then evaluated in order to find the significance of each of these parameters on the surface quality of the end product. Results showed that overvoltage, which is dependent on the interelectrode gap and the electrolyte temperature, is one of the main parameters affecting the surface finish; additionally there is a strong relationship between the resulting surface finish and the electrolyte flow. The interelectrode gap and inlet electrolyte temperature also affect the resulting surface finish but their influence was not so evident in this work. Finally, the variation of the electrolyte temperature during the process was found to have a great impact on the uniformity of the surface finish along the sample. We believe that this contribution enables the tailoring of the surface finish to specific applications while reducing manufacturing costs and duration of the ECM process

Microstructural and chemical surface and rim zone changes of ferrite‐perlite 42CrMo4 steel after electrochemical machining

“…As the pulse‐pause ratio was constant for the whole sample, only a change in the electrolyte composition along the electrolyte flow is assumed to change the electrochemical conditions and result in different surface qualities. A high current density is supposed to result in a reflective surface, whereas a low current density result in a rough surface as the passive film is not or only inhomogeneously removed [1]. Nevertheless, the reported results were not unambiguously.…”

“…Electrochemical machining is not only used for generating profiles that cannot be gained with any other process, but also for achieving high quality polished surfaces without undesirable tensile residual stresses. Investigations on ferrite‐pearlite 42CrMo4 showed that optically different surface areas are formed by electrochemical machining, varying between a shiny (reflective) and a dark (rough) surface appearance already after one machining step [1]. A reflective surface can be generated by micro‐smoothing which results from suppression of the influence of surface defects and crystal orientation and depends on the passivation behavior and on the chemical and microstructural composition of the material [2, 3].…”

3D multiphysics model for the simulation of electrochemical machining of stainless steel (SS316)

“…The work described in this paper is part of a project where a multiphysics ECM simulation model was constructed by the authors, originally in a 2D environment, further developed into a 3D computational simulation, and subsequently linked with a real-world application example [23].…”

Evaluation of Electrochemical and Laser Polishing of Selectively LaserMelted 316L Stainless Steel

“…Like overpotential, current density must be sufficiently high to maintain the proper dissolution of metal, but it must not be too high. The interplay between current density and overpotential plays a deciding factor in the type of surface finish produced by electrochemical polishing, as seen by (Gomez-Gallegos, Mill, & Mount, 2016), who performed electrochemical polishing of 316 stainless steel pipes.…”

“…Different surface finishes of 316 SS as a function of current density and overpotential(Gomez-Gallegos et al, 2016).The rhomboids inFigure 15represent areas where a non-uniform surface finish was achieved. These regions are also referred to as being below the oxygen evolution potential, and at it.…”