Two-step electropolishing of internal surfaces of 316L stainless steel made by laser-based powder bed fusion

Abstract

Investigating electropolishing (EP) effects on the material removal process of laser-based powder bed fused internal surfaces is crucial for the application of EP in the polishing of complex internal structures. This study aims to electropolish various internal surfaces of 316L stainless steel fabricated by laser-based powder bed fusion (L-PBF). Un-sintered powders and sintered area on top, face up, side and face down internal surfaces were characterized. Based on the material removal characteristics of different surface features, a two-step EP was proposed using different potentials and polishing time for L-PBF internal surfaces after parametric study in a developed EP system which is capable of circulating electrolytes in high-speed. Material removal process and anodic dissolution of L-PBF internal surfaces were then discussed based on experimental results and impedance analysis. The comprehensive characterizations of morphology, roughness and cross sections with microstructure differences in consideration are important for analyzing the evolution of L-PBF surfaces during polishing. The study demonstrates the high efficiency of the two-step EP in polishing various L-PBF internal surfaces.