Microstructure and corrosion behavior of 316L stainless steel lattice and bulk parts manufactured by LPBF using fiber and CO2 lasers

Abstract

AISI 316L stainless steel lattices were manufactured using two distinct Laser Powder Bed Fusion (LPBF) techniques: a commercial printer equipped with a fiber laser and a novel system equipped with a CO2 laser. Fiber laser systems produce parts exhibiting superior detail, finer cell size, and lower porosity compared to CO2 laser ones because of the stability of the laser beam and the higher absorptivity of the laser light by the material powder. Electrochemical tests indicated that lattices exhibited inferior corrosion resistance compared to solid counterparts for both manufacturing techniques. This disparity is caused by the distinct corrosion mechanisms exhibited by lattices and solid parts, as observed through Electrochemical Impedance Spectroscopy (EIS). The observed differences are attributed not only to the increased different specific surface areas but also to the distinctive morphologies formed in the material beneath the surface. CO2 LPBF lattices demonstrated higher corrosion sensitivity than the fiber LPBF lattices due to their distinct microstructure and the more prevalent presence of defects