Multi-physics coupling mechanism of droplet transfer in CMT-P arc additive manufacturing of Inconel 718 alloy

By combining in-situ observation and numerical simulation, this study investigated the effects of different pulse counts on droplet transfer behavior, temperature distribution, flow characteristics and the main forces acting on the droplet during the Cold Metal Transfer with Pulse(CMT-P) arc manufacturing of Inconel 718. Unlike previous CMT-P studies that typically fixed the CMT/P ratio, this work systematically varies the pulse number and suggests a new overheating-induced Marangoni detachment mechanism in Inconel 718. The results reveal that the transition of droplet transfer modes in Inconel 718 is governed by a multi-physics coupling mechanism rather than a single volume threshold. Specifically, by altering the cumulative heat input, the number of pulses can regulate the force balance and heat distribution within the droplet. A single pulse leads to retraction dominated by surface tension; two pulses trigger a projected transfer driven by gravity and electromagnetic force; while three pulses induce an overheating-induced Marangoni backflow, which locally reduces surface tension and enables low-velocity, small-volume detachment. These findings provide a theoretical foundation for optimizing thermal input and improving droplet transfer stability in high-performance nickel-based alloy repair.