Development of melt pool profile in Nd:YAG and fiber pulsed laser spot welding of 316 stainless steel foils

In this research, a pulsed Nd:YAG and a pulsed fiber laser are compared and assessed for the micro-welding of thin foils of stainless steel. The study concerned weld pool profile in spot welding of 175 μm stainless steel 316 thin foils, and the effects of the pulse duration of the Nd:YAG laser, the duty cycle of the fiber laser, and the nominal power of both lasers were investigated. A quantification approach was applied to assess the degree of asymmetry in the weld profiles. For the Nd-YAG laser, as the nominal power increased from 100 A to 140 A across different pulse durations, the asymmetry increased by up to 60 %. On the other hand, the weld profile obtained from the pulsed fiber laser showed central underfill depth, which increased with the increasing duty cycle. The largest underfill occurred at a nominal power of 4 V, at a duty cycle of 30 %. These observations examine the spatial and temporal intensity distributions of the laser sources and their effect on melt pool dynamics, providing insight that can be employed for optimizing laser micro-welding processes in growing industrial applications.