Transient Simulation of the Removal Process in Plasma Electrolytic Polishing of Stainless Steel

I. Danilov [1], M. Hackert-Oschätzchen [1], I. Schaarschmidt [1], M. Zinecker [1], A. Schubert [1],
[1] Professorship Micromanufacturing Technology, Chemnitz University of Technology, Chemnitz, Germany

Plasma electrolytic polishing (PeP) is an electrochemical method for surface treatment. In detail PeP is a special case of anodic dissolution [1] that unlike electrochemical polishing requires higher voltage and uses environment friendly aqueous solutions of salts. When the process starts, the anode is covered with a plasma-gas layer. During processing, the surface of the workpiece becomes smoother and get higher gloss level. Due to small achievable roughness (Ra < 0.02 μm) and small removal rates [2], this process is applied for finishing of precision parts. In recent years, a lot of studies on PeP have been made. Nevertheless, at presence, only a few research work has been focused on the understanding of the process basics. To investigate the basics of PeP a 2D simulation model was developed. Geometry and boundary conditions are based on principle scheme shown in Figure 1. The model set up and calculation were made in COMSOL Multiphysics ®. Electric Currents and Deformed Geometry interfaces were chosen for this model.The initial anode surface profile was generated in COMSOL Multiphysics® using Spatial Frequencies method [3]. This was made to simulate the polishing effect of PeP. The anode is placed inside the basin with electrolyte with a conductivity of 120 mS/cm. The side and bottom boundaries of the basin are grounded. Voltage of 200 V is applied to the anode boundaries. In this model, a special interest is focused on the plasma-gas layer and the electric potential. The thickness of the plasma-gas layer and its conductivity are based on experimental data [4, 5]. Material removal is realised as a function of the current density at the workpiece surface. The paper shows that the main voltage drop in PeP occurs in the plasma-gas layer and that primarily the profile of the surface determines the distribution of current density. Both effects have a main significance in the polishing process. Furthermore, the polishing effect on the surface profile will be analysed.

[1] K. Nestler, F. Böttger-Hiller, W. Adamitzki, G. Glowa, H. Zeidler, and A. Schubert, “Plasma Electrolytic Polishing - An Overview of Applied Technologies and Current Challenges to Extend the Polishable Material Range,” Procedia CIRP, vol. 42, no. Isem Xviii, pp. 503–507, 2016, ISSN: 22128271, DOI:10.1016/j.procir.2016.02.240 [2] H. Zeidler, F. Boettger-Hiller, J. Edelmann, and A. Schubert, “Surface Finish Machining of Medical Parts Using Plasma Electrolytic Polishing,” Procedia CIRP, vol. 49, pp. 83–87, 2016, ISSN: 22128271, DOI:10.1016/j.procir.2015.07.038 [3] B. Sjodin, “How to Generate Random Surfaces in COMSOL Multiphysics® | COMSOL Blog.” [Online]. Available: [Accessed: 24-May-2018] [4] A. S. Rajput, H. Zeidler, and A. Schubert, “Analysis of voltage and current during the Plasma electrolytic Polishing of stainless steel,” Proc. 17th Int. Conf. Eur. Soc. Precis. Eng. Nanotechnology, EUSPEN 2017, no. May, pp. 2–3, 2017, ISBN: 9780995775107 [5] I. S. Kulikov, S. V. Vashenko, and A. Y. Kamenev, Electrolytic plasma processing of materials. Minsk: Belarusskaya Nauka, 2010, ISBN: 978-985-08-1215-5