Effect of Nd:YAG Laser Beam Welding on Microstructure and Mechanical Properties of Super Duplex Stainless Steel Sheets

Laser beam welding (LBW) is a relatively low heat input process and beneficial for joining heat sensitive super duplex stainless steels (SDSS). In this research work, 2 mm thick SDSS plates were joined by LBW using Nd:YAG laser source. Six weld joints were made at different welding speeds (90-140 mm/s). The fusion zone did not show any pores or cracks, and full penetration was obtained in all the joints. Coarse-grained dendritic microstructure was observed inside the fusion zone. The HAZ was narrow and did not show any coarse grains. The duplex structure underwent a phase transformation. The ferrite content varied in the range of 60-77%. The grain growth and the transformation of the austenite phase subsided at higher welding speeds. The grain size and the austenite content influenced the fusion zone hardness and the fracture location. Overall, all the joints displayed typical cup and cone ductile mode of fracture.