Effect of beam oscillation on the mechanical properties of fiber-laser-welded thin-plate X2CrTiNb18 ferritic stainless-steel joints

This study adopted fiber laser welding (FLW) and oscillating fiber laser welding (OFLW) to weld 1.2 mm-thick X2CrTiNb18 ferritic stainless steel (FSS) in the form of square butt joint. The microstructure and mechanical properties of two types of joints were characterized and compared. The results showed that beam oscillation had a marginal effect on the unidirectional tension properties of the joints. However, the plasticity and fracture toughness of the joint were markedly increased. The beam oscillation changed the morphology and microstructure of the weld. It transformed the outer profile of the weld cross-section into an inverted trapezoid, and formed an equiaxed grain zone in the weld. Beam oscillation decreased the angle between the growth direction of columnar crystals around the equiaxed grains and the weld centerline, which improved the deformation coordination of the grains. The plasticity and fracture toughness of X2CrTiNb18-FSS joints were also improved accordingly.