In-situ measurement of heat and mass transfer behavior in alternating-arc through polarity-switching self-adaptive shunt

Abstract

Correctly integrating and planning the use of heat source to provide heat and mass transfer on demand is the key factor to achieving high forming efficiency and high forming accuracy in arc-based directed energy deposition. The Alternating-Arc through Polarity-Switching Self-Adaptive Shunt (PSSAS) method precisely manages current distribution between wire and substrate, effectively decoupling heat and mass transfer. This allows tailored heat input for each deposition layer while maintaining high efficiency. Using in-situ measurements, this study quantifies heat transfer to the substrate and wire, calculates droplet temperature, and captures droplet size via high-speed imaging. Results show that PSSAS transfers anode heat from the substrate to the wire during the electrode negative (EN) phase, reducing substrate heat transfer by 45.9 % to 55.7 %. As EN current increases, substrate heat transfer grows slowly, rising only 41.7 % within 70A to 150A. At the same welding current, wire heat transfer in PSSAS is 31.3 % to 43.9 % higher than in traditional Variable Polarity Plasma Arc (VPPA), indicating superior wire melting efficiency. Overall, PSSAS reduces heat transfer to the substrate by approximately 50 % compared to the traditional VPPA mode, while increasing heat transfer to wire by about 35 %. Further analysis reveals that electromagnetic and plasma flow forces drive droplet transfer in PSSAS, ensuring controlled transfer and good forming quality. PSSAS thus offers decoupled heat and mass transfer with controllable droplet transfer, providing a novel approach for arc-based directed energy deposition.