Correlation of Lack of Fusion Pores with Stress Corrosion Cracking Susceptibility of L-PBF 316L: Effect of Surface Residual Stresses

Abstract

Stress corrosion cracking (SCC) of laser powder bed fusion-fabricated 316L was studied under the variation in energy input density to emulate the existence of distinctive types of defects. Various electrochemical polarization measurements were performed in as-received polished and ground states, to elucidate the effect of defect type on corrosion and SCC behaviour in marine solution. The results revealed severe localized corrosion attack and SCC initiation for specimens with a lack of fusion pores (LOF). Moreover, the morphology of SCC was different, highlighting a more dominant effect of selective dissolution of the subgrain matrix for gas porosities and a more pronounced effect of brittle fracture at laser track boundaries for the specimens with LOF pores.

Laser Powder Bed Fusion Fabrication of a Novel Carbide-Free Bainitic Steel: The Possibilities and a Comparative Study with the Conventional Alloy

“…Porosity assessment was performed by optical microscopy (OM) using a LEICA DMRE optical microscope (Leica Microsystems S.r.l., Milan, Italy). With the aim of having a good statistical model for the pore characterization, 5 pictures were taken from each magnification of 50, 100, and 200× from both the center and surface of the cross-sectioned surface, according to the procedure reported by the authors in [9,10,60]. Subsequently, the images were analyzed with ImageJ 1.54d [61], and statistical analysis was performed utilizing the OriginLab 2023b software [62].…”

“…These techniques can be categorized into different groups [1], with laser powder bed fusion (L-PBF) being the most diffused method. Extensive research on L-PBF is available in the literature [5][6][7][8][9][10], highlighting its superior accuracy and the high quality of the final components it produces. L-PBF involves the deposition of layers of powders on a build platform and the subsequent melting, adopting a high-power laser beam.…”