Ultrasonic assisted electropolishing to reduce the surface roughness of laser powder bed fusion based additively manufactured copper heat exchanger components

As-built additively manufactured components for heat exchanger applications, suffer from high surface roughness. In this study, a novel ultrasonic-assisted electropolishing setup is designed and tested to reduce the internal surface roughness of a Laser Powder Bed Fusion (L-PBF) additively manufactured copper (GRCop-42) heat exchanger component. In the electropolishing setup, the surface of the as-built heat exchanger is used as the anode while a bulk copper rod is used as the cathode. An electropolishing fluid consisting of CuCl2, HCl, and SiC abrasive particles was used as electrolyte media, along with ultrasonication. The effect of chemical constituents, ultrasonic duration, and abrasive particles on surface roughness reduction was studied. It was observed that the ultrasonic agitation condition assisted with the abrasive particles was beneficial to reduce the surface roughness of the heat exchanger sample (over 50%) through acoustic streaming and scrubbing effect. An addition of 1% bio-based trihexyltetradecyl phosphonium saccharinate ionic liquid improved the corrosion properties for the copper surface. Overall, to reduce the roughness of L-PBF additively manufactured samples of complicated shapes with internal features, this process could be a viable technique, where mechanical polishing is not possible and internal surfaces are not accessible.