Laser Direct Energy Deposition of Stainless Steel 316L:Investigation of Processing Parameters on Porosity andMicrostructural Evolution

Abstract

Laser direct energy deposition (LDED) was employed to fabricate low-carbon stainless steel 316L and
to evaluate the influence of processing parameters on porosity, relative density, and microhardness. A fiber laser
system operating at 1070 nm (YLS-3000-CUT, IPG ABB) was used. The spot size was 1.2 mm, the powder feed
rate was 9.5 g/min, the layer thickness was 0.2 mm, the carrier gas flow rate was 7.5 L/min, and the shielding gas
flow rate was 25 L/min. Laser power (420, 600, and 800 W) and scan speed (20, 25, and 30 mm/s) were
systematically varied, producing nine samples with linear energy densities between 14 and 40 J/mm and volumetric
energy densities from 59 to 167 J/mm³. Microstructural features and pore morphology were examined using optical
microscopy and scanning electron microscopy. Porosity and relative density were quantified by full cross-sectional
image analysis. Microhardness was measured using a Vickers indenter with a 300 g load and 10 s dwell time.
Microhardness values ranged from 185.4 to 207.3 HV. Porosity values varied between 0.198% and 0.831%, while
relative density ranged from 99.169% to 99.802%. Lower volumetric energy densities produced reduced porosity
and increased relative density at all scan speeds. The minimum porosity (0.198%) and maximum relative density
(99.802%) were obtained at a scan speed of 30 mm/s and a volumetric energy density of 59 J/mm³. The results
quantify the effect of laser power and scan speed on densification and mechanical response in LDED-processed
316L and define a limited processing window for defect minimization.