Effect of travel speed on the microstructure and mechanical properties of laser beam welded nitronic-50 stainless steel joints

Abstract

In this study, fiber laser beam welding was used to join 3 mm-thick nitronic-50 stainless steel. The effect of travel speed on the mechanical, microstructural, and corrosion properties of the weld joints was studied. The experimental findings reveal that travel speed significantly affected the size of bead geometry and the fusion boundary of the weld joints. The microstructure of columnar grains transformed into equiaxed dendritic grains at the center of the weld nugget due to fast cooling at higher travel speeds. The increase in ferrite content was due to the incomplete transformation of ferrite to austenite at higher travel speeds, which led to higher strength and microhardness in the weld joints. Similarly, the corrosion studies demonstrate that the weld joints made at higher travel speeds have superior corrosion resistance due to a higher fraction of equiaxed dendritic grains and smaller dendrites with less inter-dendritic arm spacing.