Elucidating the impact of laser beam shape on the as-printed microstructure in 316L stainless steel

Abstract

In Laser Powder Bed Fusion (L-PBF), the intrinsic inclination of the laser beam creates variability in the interaction between the laser and the melt pool, which along with thermal conditions within the pool, results in the formation of defects in the parts. To elucidate the impact of laser beam inclination on the melt pool, a deposition scale model using the finite volume method (FVM) is developed. The laser model demonstrates that as the laser beam inclines towards the periphery of the build plate, the projected laser spot size enlarges, resulting in lowered energy density. To assess how the laser beam inclination affects multi-layer printing, cubic specimens are printed at both the center and the far corner of a rectangular build plate of 280 mm x 280 mm size. X-ray computer tomography (X-CT) is used to investigate internal porosities and electron backscatter diffraction (EBSD) is used to characterize the microstructure of the printed cubes. The experimental results are discussed based on the FVM simulations.