Process Understanding of Plasma Electrolytic Polishing through Multiphysics Simulation and Inline Metrology.

Igor Danilov,Gunnar Meichsner,Mike Zinecker,Matthias Hackert-Oschätzchen,Jan Edelmann,Andreas Schubert

doi:10.3390/mi10030214

Abstract

Currently, the demand for surface treatment methods like plasma electrolytic polishing (PeP)—a special case of electrochemical machining—is increasing. This paper provides a literature review on the fundamental mechanisms of the plasma electrolytic polishing process and discusses simulated and experimental results. The simulation shows and describes a modelling approach of the polishing effect during the PeP process. Based on the simulation results, it can be assumed that PeP can be simulated as an electrochemical machining process and that the simulation can be used for roughness and processing time predictions. The simulation results exhibit correlations with the experimentally-achieved approximation for roughness decrease. The experimental part demonstrates the results of the PeP processing for different times. The results for different types of roughness show that roughness decreases exponentially. Additionally, a current efficiency calculation was made. Based on the experimental results, it can be assumed that PeP is a special electrochemical machining process with low passivation.

Highlights

A summary of the plasma electrolytic polishing (PeP) process is shown in Figure 1, where the workpiece is an anode connected to a DC energy source
PeP is a technology that is used as a finishing surface treatment for precision metallic parts because of low achievable roughness (Ra < 0.02 μm) and low removal rates [2,3]
In comparison to mechanical polishing, in PeP, the whole workpiece surface can be polished in a few minutes, as can complex free forms [2,4,5]

Summary

Introduction

Plasma electrolytic polishing (PeP) is a special case of electrochemical machining [1] which requires high voltage and uses an environmentally-friendly aqueous solutions of salts. In comparison to mechanical polishing, in PeP, the whole workpiece surface can be polished in a few minutes, as can complex free forms [2,4,5]. There is a lot of information on solutions used for polishing different metal alloys (e.g., steels, aluminium, titan and others) [5,6,7,8,9,10,11,12] and process parameters (e.g., temperature, electrolyte concentration, voltage, etc.). TThhee rreessuullttss aarree sshhoowwnn iinn FFiigguurree 33. N. Regardding tthhe pprroocceessss,, tthheerree aarree ssttiillll ttwwoo bbiigg ggaappss iinn oouurr uunnddeerrssttaannddiinngg ooff tthhee PPeePP pprroocceessss:: tthhee ddeettaaiilleedd ddeessccrriippttiioonn ooff condduuccttiivviittyy ooff the plasma-gas layer and the polishing mechanism of PeP.

Electrical Conductivity of the Plasma-Gas Layer

Experimental Results

Conclusions