Interaction between Laser Beam and Arc in Hybrid Welding Processes for Dissimilar Materials

Abstract

Industrial solutions for joining of similar and, most recently, of dissimilar materials are increasingly based on hybrid laser-arc welding processes. To increase the understanding of the synergistic effects of such hybrid processes, it is necessary to investigate the interaction between laser beam and arc. For such investigations, a working head was developed which combines a Nd:YAG laser beam and a plasma arc in a coaxial way. With this equipment the interaction effects between laser and arc were investigated in dependence of laser power, focal position and arc current (AC mode). For process analysis, a high-speed-camera synchronized with a transient recorder (measuring arc current and voltage) was used. In the experimental series reported, an interaction between laser beam and plasma arc resulting in a constriction of weld bead and arc zone and a stabilisation of the foot point of the arc was observed for a wide range of parameter settings. Moreover, for a laser beam intensity exceeding approximately 6*105 W/cm2 and an AC current below 80 A, the effective arc voltage was significantly reduced. As a working hypothesis, this effect was attributed to the occurrence of laser-induced metal vapour at higher intensities.