Abstract: Ultra-high power laser-arc hybrid welding provides an effective method for realizing the efficient welding thick-walled components, however, spatter is a serious problem in this process. Aiming at the spatter problem of ultra-high power laser-arc hybrid welding, the spatter evolution behavior and suppression methods are studied, the influence of arc heat input on the spatter and its suppression mechanism. In addition, the impact of arc heat input on the macroscopic formation, microstructure and mechanical properties also discussed. Results show that the keyhole will be significantly enlarged and the spatter will be remarkably inhibited with the increase of arc heat input. The keyhole opening increases from 56.57 mm² to 243.29 mm² when arc heat input increases from 139 J/mm to 479 J/mm. The frictional shear force between molten metal and metal vapor/plasma around the keyhole decreases, which results in the molten metal column decreasing from 15.96 mm to 5.27 mm. Moreover, the molten metal column will be fell back to the molten pool under the action of surface tension and of molten metal at the front of keyhole and static pressure of fluid. The number of spatter on the weld surface is reduced by 78% and the quality of weld formation is conspicuously improved. It is also found that the increase in arc heat input will enhance the weld width and depth, which results in coarsening of microstructure and increase in the heat affected zone width, but all specimens present good tensile properties. The effective suppression of spatter in ultra-high power laser-arc hybrid welding provides data and theoretical support for the regulation of the process parameters of this technology in the field of thick plate welding.

Key words: ultra-high power laser-arc hybrid welding, spatter formation, suppression method, arc heat input, keyhole opening