Study on the droplet transfer behavior and microstructure of wire arc additive manufactured Inconel 718 alloy assisted by an alternating magnetic field

Abstract

• The alternating magnetic field changes arc morphology and reduces droplet size. • Appropriate excitation current effectively reduces surface roughness. • The alternating magnetic field can effectively refine the grains and deflect the grains growth direction. In this paper, the bead geometric characteristics, droplet transfer behavior and microstructure of wire arc additive manufactured Inconel 718 alloy using cold metal transfer process assisted by an alternating magnetic field (AMF) are investigated by varying the excitation current. The results show that the AMF reduces the droplet size from 1.7 mm to 1.4 mm, and changes the arc shape from bell shape to “broom shape”. With increasing excitation current, the surface roughness first drops from 0.14 at 0 A to 0.08 at 20 A and then rises to 0.25 at 40 A, finally reaching a maximum value of 0.39 at 60 A. The grain growth direction is deflected along the build direction by the AMF, and the average grain size decreases to 69.5 μm.