Morphology and energy distribution characteristics of ultra-high frequency adjustable multi-pulse GTAW arc

To address the limitations of conventional gas tungsten arc welding (GTAW), such as shallow penetration, low welding speed, and inefficiency, this paper proposes an ultra-high frequency adjustable multi-pulse GTAW (UFMP-GTAW) process. By introducing a medium-current phase, this process generates multi-pulse waveforms within a single cycle, achieving a welding current frequency of 100 kHz and a current change rate of 150 A/μs, with adjustable pulse duration and amplitude at each stage. An experimental platform for UFMP-GTAW was established to compare the morphology and energy distribution characteristics of ultra-high frequency arcs with conventional high-frequency pulsed arcs using high-speed imaging and spectral analysis. Results indicate that under the same average current, the high-frequency effect of ultra-high frequency current compresses the arc, concentrating its temperature distribution. The 100 kHz UFMP-GTAW arc exhibits a high-temperature region (>14,000 K) proportion of 42.18 % and a 16.7 % increase in conductivity compared to conventional pulsed arcs. Welding tests demonstrate that the 100 kHz UFMP-GTAW process significantly refines weld grain structure and enhances joint strength. For Inconel 718 nickel-based alloy, grain size decreases from 1200 μm to 50–150 μm, with tensile strength and elongation improving by 12 % and 28 %, respectively. This study provides theoretical and experimental foundations for optimizing high-frequency pulsed arc welding processes and high-performance material welding.