On the pitting behaviour of laser powder bed fusion prepared 316L stainless steel upon post-processing heat treatments. (1st April 2022)

• Record Type: Journal Article
• Authors: Wang, Ke; Chao, Qi; Annasamy, Murugesan; Hodgson, Peter D.; Thomas, Sebastian; Birbilis, Nick; Fabijanic, Daniel
• Is Part Of: Corrosion science. Volume 197(2022)
• Publication Date: 2022-04-01
• Subjects: Stainless steel -- Polarisation -- Potentiostatic -- Pitting corrosion -- Repassivation; Corrosion and anti-corrosives -- Periodicals; 620.11223
• DOI: 10.1016/j.corsci.2021.110060
• Languages: English
• ISSNs: 0010-938X

Abstract

Abstract: Type 316L stainless steel manufactured by laser powder bed fusion (LPBF) in conjunction with appropriate post-treatment has been demonstrated to offer superior pitting resistance and a distinct pitting mechanism compared to wrought 316L. This work examines the effect of post-processing annealing time, temperature and microstructural changes on the pitting behaviour of LPBF 316L using potentiodynamic and potentiostatic polarisation in 0.6 M NaCl. Preferential pitting at melt pool boundaries was observed, due to heterogeneity of micro-strain or lattice imperfection. High temperature annealing resulted in the transformation of amorphous oxides with associated Cr-depletion, leading to a reduction of E pit and E rp . Highlights: An essentially porosity-lean 316L stainless steel was prepared by LPBF and subjected to cyclic potentiodynamic and potentiostatic polarisation analysis in 0.6 M NaCl. Preferential pitting at melt pool boundaries was observed, due to heterogeneity of micro-strain or lattice imperfection. An increased pitting potential was detected in the LFBF 316L after annealing at 800 °C for 2 h despite the presence of sigma phase formation. Simultaneous formation of MnS precipitates and coarsened oxides was observed after annealing at 1000–1100 °C and the latter predominantly contributed to a reduced pitting potential.