Optimization process parameters in laser welding of CLF-1/316LN-IG dissimilar steels for improved welded joint formation and mechanical performance

This study investigates the laser welding of dissimilar materials between CLF-1 steel and 316LN-IG austenitic stainless steel (ASS), which are two typical structural materials used for critical components fabrication in nuclear fusion reactors. The focus of this work is primarily on the optimization of the key process parameters to ensure welded joints integrity and mechanical performance. A Response Surface Methodology (RSM) approach was employed to analyze the effects of laser power (LP), welding speed (WS), and focal position (FP) on penetration depth (PD), weld width (WW), and weld reinforcement height (WRH). Based on the statistical modelling, it was found that LP emerged as the predominant factor influencing the weld profile among the three variables, while WS and FP exhibited significant effects on WW and WRH, respectively. A high quality 10 mm thick CLF-1/316LN-IG dissimilar steels laser welded joint was achieved under the optimized welding parameters in accordance with the weld acceptance criteria. In addition, numerical simulation and microstructural analysis results revealed that there were significant differences in solidification behavior between the 316LN-IG ASS side fusion zone and CLF-1 steel side fusion zone. Mechanical testing further confirmed that the CLF-1/316LN-IG dissimilar steels welded joints obtained with the optimized welding parameters possessed excellent tensile strength with all the welded specimens failed in the 316LN-IG ASS base material. These findings offer significant perspectives on the formation mechanisms and mechanical behavior of dissimilar materials welded joints, thereby supporting their application in advanced nuclear fusion reactor systems.