Process stabilization in laser welding of copper using high-speed spatial beam oscillation by means of dynamic beam shaping

This paper reports on the process stabilization of laser welding of copper using high-speed spatial beam oscillation by means of dynamic beam shaping. Laser welding of copper is challenged by welding defects such as spatter and voids due to the instability of the keyhole and melt pool behavior during the welding. In this study, spatial beam oscillation by means of dynamic beam shaping was applied to copper welding to stabilize the welding process. Using coherent beam combining for the dynamic beam shaping, the position of the intensity maximum was moved at different oscillation frequencies up to 150 kHz. The effect of the laser oscillation frequency on the defect formation and welding behavior of copper was investigated via in-situ observation of the keyhole and the melt pool by high-speed and X-ray imaging. The results show that the spatial beam oscillation in welding direction by dynamic beam shaping significantly influences the process behavior of copper welding. The keyhole and melt pool behavior is stabilized by increasing the laser oscillation frequency to 60 kHz and above. Due to the process stabilization, welding defects such as spatter and voids are minimized. It was concluded that dynamic beam shaping has the potential to stabilize the welding behavior of copper even more than the conventional method owing to a higher oscillation frequency of the laser beam.