Effects of welding parameters on microstructural development and mechanical properties of autogenous laser welded 316L stainless steel plates

Laser welding of AISI 316L stainless steel plates is carried out and the microstructure and the mechanical properties are related to welding parameters. An optical microscope and a scanning electron microscope (SEM) were utilized to study the microstructure while hardness profile across the welded region was obtained using Vickers microhardness tester. X-ray diffraction (XRD) was conducted to observe the phase transition in the fusion zone. It is found that grain coarsening is evident in the heat affected zone (HAZ) while highly directional fine grains consisting of mainly dendritic and cellular structures are present in the fusion zone. Furthermore, detailed examination of the welded region reveals that the fusion zone is free from cracks, defect sites and voids. Increasing laser beam power and welding speed resulted in grain coarsening in the HAZ and grain refining in the core zone respectively in the welded section. The sample thickness also influences temperature distribution, microstructural development, and the size of the weld bead width.