Combined electrochemical and mechanical polishing of interior channels in parts made by additive manufacturing

Components fabricated using metal additive manufacturing (MAM) without post-processing are unsuitable for high-performance applications due to their relatively poor surface quality. Therefore, a novel electrochemical-mechanical combined polishing (EMCP) process is proposed for MAM parts with interior channels, in which a tool component consisting of a coarse grinding wheel, a fine grinding wheels, and a cathode is used. The surface quality of a Φ30 mm straight interior channel is significantly improved, and its roughness values Sa and Sq are reduced by approximately 71.2% and 68%, respectively. During the EMCP process, the electrochemical dissolution is dominant for material removal with a percentage contribution of 72.2%, and the mechanical grinding has limited effect on the weight loss. Under the combined action of electrochemical dissolution and mechanical grinding, the adhesive powders are almost completely removed by the coarse grinding wheel, the band protrusions are dissolved by electrochemical machining, and the passivation film and products produced during electrochemical machining are destroyed and scraped off by the fine grinding wheel. A curved interior channel with a diameter of Φ18 mm is also efficiently polished using the proposed EMCP process. The remarkable reduction in the roughness values Sa, and Sq by approximately 79.9% and 81.1% is achieved. Furthermore, smooth surfaces of straight and curved channels with smaller diameters of around Φ5 mm and Φ9 mm are obtained. The surface roughness Sa decreased from 15.92,18.18 µm to 5.06, 6.02 µm, respectively.