Custom Cathode Optimization for Electropolishing Additively Manufactured 316L Stainless Steel

Laser powder bed fusion (LPBF) has become increasingly popular for its ability to rapidly manufacture complex metallic parts. However, the surface properties of as-built LPBF parts may degrade overall performance due to tortuous surface features. Consequently, post-processing like electropolishing (EP) to reduce the surface asperities is often needed for LPBF parts to perform as expected. Utilizing experimental and computational approaches, this project aims to more uniformly EP complex shaped parts made from LPBF 316L. For the experimental approach, parts with a three-dimensional T-shape were printed out of 316L stainless steel and EP using an acidic-based and a polyethylene glycol/NaCl-based electrolyte. A series of cathodes were designed to show how the uniformity of material removal across the T-shaped parts entire surface varies when different combinations of electrolyte, cathode, and electrode spacing were used in the EP process. The first three cathodes tested had a flat, cylindrical, and conformal shape, each with two different electrode spacings (2 and 20 mm). The results from the experiments using different cathode shapes were then compared to a COMSOL model designed to capture the impact of cathode shape on material removal. A cathode was then optimized using COMSOL, designed in Solidworks, printed out of LPBF 316L, and used to polish an anode selectively and uniformly. Based on all the metrics tested before and after EP; mass loss, surface roughness, reflectivity, and local thickness removal from 3D optical scans, the selective cathode performed the best compared to the other cathodes. The relationship between cathode shape and uniformity of material removal across the entire T-shaped parts surface will be discussed in depth.