Influence of Laser Welding Parameters on Weld Geometry and Defect Formation in Haynes 282 Superalloy

This study systematically investigated the effects of process parameters on weld geometry and defect formation in the laser butt welding of Haynes 282. Fifteen conditions were applied using a fiber laser (300–700 W, 3–5 mm/s), with heat input quantified by power density, interaction time, and energy density. Cross-sectional observations revealed that partial penetration occurred at all 300 W conditions and 400 W–5 mm/s due to insufficient heat input, while full penetration was achieved in all other conditions. The weld pool morphology indicated that conduction mode was dominant throughout the investigated range. As laser power increased or welding speed decreased, both face and root widths expanded. Specifically, the expansion of the face width was attributed to the enhancement of outward Marangoni flow; this flow was significantly intensified by the elevated peak temperatures associated with increased power density, which promoted lateral melt pool expansion even under constant energy density conditions. Furthermore, recoil pressure and gravity drove the molten metal toward the root, causing a simultaneous increase in underfill depth and root reinforcement. Internal defect analysis via X-ray CT revealed a complex, non-linear distribution of pores relative to process conditions. The 400 W–5 mm/s condition exhibited the highest pore count, while the 500 W–4 mm/s condition showed maximum porosity. Considering both external geometry and internal integrity, the 500 W–5 mm/s condition was determined as optimal, ensuring full penetration while minimizing underfill, root reinforcement, and porosity.