Effect of laser assistance on arc stability and droplet transfer in hybrid welding with C276 Hastelloy filler wire

: With the growing demand for large-scale, high-precision, and industrialized LNG storage tanks, Hastelloy C276 as a key filler metal faces significant challenges in welding efficiency and process stability. This study investigates the instability mechanisms of droplet transfer in the gas metal arc welding (GMAW) process of C276 alloy through differential scanning calorimetry (DSC), electrical signal analysis, and high-speed imaging of droplet transfer. To enhance process stability and weld formation quality, Assistance lasers with varying power levels were introduced for coordinated regulation. The results reveal that the introduction of laser irradiation significantly improves arc stability, with its influence mechanisms varying across power levels. At 0.5 kW, arc behavior is governed by a dynamic interplay between laser plasma guidance and weld pool geometry. At 1.0 kW, droplet size decreases and arc disturbances are stabilized, improving weld consistency. In the 1.5–3.0 kW range, increased laser plasma attraction further enhances arc directionality and reduces instability. However, when laser power exceeds 3.5 kW, enlarged droplets and keyhole oscillations introduce risks of spatter and porosity. This work is aimed at clarifying the regulation effect of laser assistance on process stability and providing guidance for process optimization., and provide valuable guidance for the engineering application of laser-assisted arc welding in the fabrication of large-scale LNG inner tanks.