Random Sequential Simulation of the Resulting Surface Roughness in Plasma Electrolytic Polishing of Stainless Steel

Abstract

Plasma electrolytic polishing (PeP) is an electrochemical method for surface treatment. Unlike electrochemical polishing, PeP requires higher voltage and uses environment friendly aqueous solutions of salts. This process can be realised by immersing a workpiece inside an electrolyte bath or by using an electrolyte jet (Jet-PeP process).In this work a new stochastic method for modelling the plasma electrolytic polishing process is presented. The model was developed to predict the possible achievable surface roughness based on the defined initial one after PeP and Jet-PeP processes. The model describes the workpiece surface and the plasma-gas layer in 2D. The method formulation is based on the assumption, that PeP can be described as an electrochemical process. The physical parameters of the plasma-gas layer were calculated based on the experimental data.To realise the surface roughness change during PeP process a random method for the generation of the initial rough surface and a random method for the removal process were developed. The rough surface generation is based on the random deposition method and the Monte Carlo method. Initial Ra roughness is given as an input parameter.The removal process is simulated using locally defined probability. This probability is based on the Poisson point process depending on the current density on the surface. The simulation model uses the finite difference method (FDM) for the calculation of the electric potential and electric field.In this work, the calculation of various surface roughness variables is implemented and the results of polishing simulation are discussed. It is shown that with the help of the developed stochastic method it is possible to simulate the surface roughness change during the PeP process.