Analysis of melting-to-solidification flow patterns with changes in depositional position during the wire-arc direct energy deposition process

Molten pool behavior plays an important role during bead formation in wire-arc direct energy deposition (DED) processes. However, this pool is susceptible to external forces, particularly the changes in direction of gravity when the depositional position is changed. In this study, a 3D simulation of the wire-arc DED was performed using computational fluid dynamics (CFD) considering various depositional positions. The experiments in - 30 degrees, 0 degrees, and 30 degrees positions were performed using a tilting table to visualize the influence of the components of gravity. The volume of fluid method was used to represent the deposition and solidification process of the molten pool. A high-speed camera and cross-sections of the bead were used to evaluate the CFD model by comparing the molten pool lengths and bead geometries; the simulation and experimental results were similar. Based on these verified results, flow patterns, temperature distributions, and solid fractions were used to elucidate the changes in each position (such as a 14.3% decrease in the molten pool length and a 13.3% increase in the bead width between downward and flat positions) and the unstable deposition in the upward position.