Effect of electropulsing-assisted ultrasonic nanocrystal surface modification on microstructures and hardness of additive manufactured Inconel 718

Additive manufacturing can process parts with complex shapes and has great application potential in the biomedical and aerospace industries. However, additively manufactured parts have a poor surface finish, high porosity, and large tensile residual stresses and thus have poor mechanical properties compared with traditional cast or forged parts. To address this issue, an innovative surface process, namely electropulsing-assisted ultrasonic nanocrystal surface modification (EP-UNSM) technology, is proposed. A pulsed current is exerted on the specimen to improve the metal plasticity during the UNSM processing, thereby increasing the effectiveness of strengthening. The results indicate that compared with UNSM, EP-UNSM can further improve the surface quality, surface hardness and the depth of the plastic deformation layer of the specimen. Moreover, it is observed that UNSM is more effective at higher peak current densities. In addition, compared with continuous current with identical thermal effect, pulsed current can more effectively improve the plasticity of Inconel 718, which proves the existence of the athermal effect of electroplasticity.