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Vertical up welding of 5A06 aluminum alloy thick plates was conducted by 10-KW-level oscillation laser beam, and the process characteristics were investigated. Results showed the circle oscillation resulted in the most satisfied stability state in terms of laser plasma and spatters due to its actual laser moving speed was the fastest, while its weld bead formation tilted because the melt metal was repel to one of the lateral walls. With linear oscillation, spatters were severe due to the laser actual moving speed drop to zero at reversal points, while the melt metal was repel to both lateral walls. Infinity oscillation resulted in the most satisfied weld bead formation due to its laser moving speed was in between and the melt metal was mainly repel to the tail of the weld pool. 20-mm-thick plates were successfully welded with 10-KW-level linear, circle, and infinity oscillations. Average tensile strength by linear, circle, and infinity oscillations were 355.5 MPa, 338.7 MPa, and 343.7 MPa, reaching 98.7%, 94%, and 95.4% of the base material (360 MPa).

This study used a nickel-based filler metal to fabricate a surfacing layer on a low-carbon steel substrate by a hybrid welding process with a rotating laser and arc. The surfacing layer's weld formation was studied using optical microscopic observation (OM). The microstructure of the layers was studied by using the scanning electron microscope (SEM), energy dispersive spectrum (EDS) and X-ray diffraction (XRD). The arc, metal transfer, molten pool flow behaviors, and U–I characteristics during hybrid laser arc welding (HLAW) were analyzed using the arc analyzer and high-speed camera. The results show that a rotating laser improves the weld formation of gas metal arc welding (GMAW). The microstructure of the two surfacing layers consists of dendritic γ phase and a small amount of Laves and NbC phases. The high dilution rate of the HLAW surfacing layer results in relatively more Laves and fewer NbC phases. The arc length of HLAW is dynamically deflected with the rotation of the laser, which expands the arc action and heating area of the molten pool. The droplet transfer mode changed from globular transfer dominant in GMAW to the projected transfer dominant in HLAW. The location where the droplet transfer into the molten pool is dynamic changed, forming a multi-point impact on the molten pool. Combined with the deflected arc with the laser rotating laser, the HLAW has a broad and deep molten pool. Understanding the metal transfer behavior of Ni-based alloys in rotating laser-induced arc hybrid surfacing is of great significance for improving surfacing forming.

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The influences of laser defocusing amount Delta z, laser power P, space distance DLA between laser and arc on weld penetration, arc modality and stability are investigated in low power YAG laser and metal active gas (laser-MAG) hybrid welding process. The experimental results indicate that the effects of laser-induced attraction and contraction of MAG arc are emerged in hybrid welding process, which result in the augmentation of hybrid welding energy. When DLA=-0.5-2 mm, Delta z=-2-2 mm and P?73 W, the synergic efficiency between laser and MAG arc is obvious, the cross section at the root of hybrid arc is contracted and the hybrid weld penetration is increased. The maximal ratio of hybrid/MAG weld penetration is 1.5 and the lowest YAG laser power that augments MAG arc is 73 W. The input of YAG laser makes the stabilities of arc ignition and combustion prominent in hybrid welding process.