Effect of molten-pool inertia in variable-width arc-based direct energy deposition by regulating parameters

Varied-thickness deposition faces the challenge of simultaneously achieving the expected width and maintaining a flat layer. Herein, the current and wire feed speed (WFS) were synchronously regulated for variable-width deposition. In forward regulation, the parameter values were changed from large to small, corresponding to the changes in the formation from wide to narrow. The opposite was true for the reverse regulation. During consecutive alternating deposition, the width for forward regulation was greater than that for reverse regulation at the same position, corresponding to the phenomenon of lag formation. To explain this phenomenon, the concept of molten-pool inertia and its corresponding mechanism were established. It was found that the inertia was directly proportional to the quality of the molten pool and was consistently directed toward a smaller parameter. The forward inertia of the molten pool in forward regulation promoted its stabilization, while the reverse inertia of the pool in reverse regulation hindered its stabilization. As a result, staggered arrangements were produced, and multilayer deposition caused varying degrees of lag formation. A more significant inertial effect was observed for higher molten-pool quality. Finally, an optimization method was proposed to weaken the molten-pool inertia and reduce bidirectional lag formation. Using this method, the sidewall surface roughness, Sa, of the variable-width region was reduced by 17.3 % compared with that before optimization.