Wire additive metal transfer for the development of high-frequency induction heating-based directed energy deposition process

Abstract

The high-frequency induction heating-based directed energy deposition (IH-DED) has emerged as a clean and environment-friendly process capable of depositing high melting point materials. The current study aims to achieve a continuous and uniform metal transfer from a 4 mm diameter mild steel wire using a developed IH-DED system. A unique multi-loop and multi-turn induction coil is designed to investigate the metal transfer mode and the frequency by varying the coil current and wire feed speed (WFS). The role of Lorentz force for the molten droplet detachment is analyzed in pertinent to the DED process. A high-speed camera is employed to capture the droplet necking and transfer mechanism to the substrate. The mode of metal transfer is observed as uniform globular form for the coil current range of 300 A − 400 A. However, the droplet detachment takes significant time to produce inconsistent droplets and non-uniform deposition at relatively high current. Hence, the coil current and WFS are optimized for continuous droplet formation at the end location of the induction coil and to ensure uniform deposition. The widening of Lorenz force distribution mainly delays the droplet detachment. However, the metal transfer rate improves significantly by enhancing the WFS (>200 mm/min) at relatively high current (>350 A). The WFS of 400 mm/min and coil current of 400 A produces a uniform and straight bead where the maximum deposition rate is achieved as 43 g/min. The current development of IH-DED process shows the future prospective for other high melting point materials.