Analysis of Stirring Action to Control Grain Refinement of Inconel 625 Superalloy Bead on Plate Using Laser Wobble Technology

In this paper, the influence of various laser wobbling patterns, such as circle, ellipse, figure eight, bowtie, Celtic, flower, atomic, hexagon, triangle and star, on grain refinement mechanisms during welding of Inconel 625 sheets is evaluated. An in-depth analysis of molten pool stirring mechanisim during welding was addressed to understand the effectiveness of wobble patterns in grain refinement and fusion zone (FZ) strengthening. The dynamic stirring effect of the laser beam’s wobble motion significantly influences the solidification process and resulting microstructure. Laser spot trajectories and temporal energy deposition were analyzed to elucidate their impact on the FZ. Electron backscatter diffraction (EBSD) micrographs showed significant grain refinement during the welding. However, the wobbling patterns with elliptical and flower-type paths resulted in coarse equiaxed grains with an average grain size of ~ 52 µm. Furthermore, the optimal patterns for refining the grain structure of Inconel 625 superalloy during laser welding are circular and atomic-type wobble patterns with grain refinement of ~ 35%. These findings highlight the potential of tailored laser wobble patterns for optimizing weld quality through controlled grain nucleation and refinement.