A numerical study on the effect of laser beam shaping on surface roughness and texture in laser powder bed fusion

Abstract

Spatial laser beam shaping is investigated to assess its influence on surface roughness in laser powder bed fusion (PBF-LB) of 316L stainless steel. A high-fidelity CFD model developed in FLOW-3D simulates Gaussian (GBP) and Ring-spot (RSBP) beam profiles, resolving laser absorption, free-surface evolution, recoil pressure, and Marangoni flow. Analytical heat sources are calibrated to measured beam profiles, and the predictions are validated against single-track melt-pool cross-sections (RMSE ≈ 6.5%) and single-layer surface topography. Under baseline conditions, the RSBP produces a wider and shallower melt pool that suppresses tail-end humping and reduces surface roughness, with simulated decreases of ~10.2% in Sa, ~36.2% in Sq, and ~44.9% in Sz relative to the GBP. Texture becomes more isotropic with the RSBP, as indicated by the Str index increasing from 0.0714 to 0.1429. Although open pores appear on RSBP surfaces at baseline power, increasing the laser power to 300 W eliminates these defects while maintaining superior surface quality compared to the GBP. Abbott–Firestone analysis shows a lower Smr1 for the RSBP, indicating fewer high peaks and a narrower functional core height. The simulations reproduce these experimental trends, establishing a predictive link between beam profile, melt-pool morphology, and resulting surface roughness and texture.