Printed cellular structure enhancing re-passivation of stress corrosion cracking in high-temperature water

Abstract

Cellular structure with high-density dislocations and elemental segregation is a unique characteristic for laser powder bed-fusion (L-PBF) 316 L stainless steels (SSs), but the role of such structure to stress corrosion cracking (SCC) remains pending. Herein we adopt multiple verification methods, including transmission electron microscope, atomic force microscopy and density-functional theory calculations to unveil its advantageous contribution to SCC resistance in high-temperature oxygenated water. Convincing evidence verify that the intrinsic Cr/Mo segregation across cellular boundaries (CBs) initiates a diffusion-induced stress and a nano-scale galvanic cell to provide a robust and stable Cr/Mo source towards near-surface grain boundaries (GBs). Consequently, there exists a Cr/Mo-rich enrichment zone at the crack tip, improving the re-passivation capacity of the SCC tip.