Abstract: Selective laser melting (SLM) and directed energy deposition (DED), as two important additive manufac-turing (AM) methods, have garnered widespread industrial applications attributing to their advantages in fabricating complex structures. Since the complex nature of microstructures produced by different AM technologies, it is necessary to carry out a thorough investigation of the stress corrosion cracking (SCC) behavior affected by these microstructures in harsh environments (i.e. hydrofluoric acid (HF)). In this study, the SCC susceptibility of DED and SLM-fabricated 316 L in HF vapor was first systematically studied by comparing it with commercial wrought (WR) 316 L to reveal the effect of microstructures (columnar crystals, melt pools, δ-ferrites, and dislocation cells) on the SCC behavior. Results show that DED-316 L has excellent SCC resistance and such resistance exhibits a low correlation with loading direction. This is because the reticulated distributed skeletal δ-ferrite facilitates enhancing film protection and hindering dislocation slip transfer. In contrast, SLM-316 L exhibits high SCC sensitivity together with a strong load-ing direction correlation. An SLM-316L-V with melt pool boundaries oriented perpendicular to the stress exhibits a high SCC tendency. Moreover, the dislocation cells without elemental segregation in SLM-316 L activate the corrosion reactivity and favor dislocation proliferation and transport, making SCC deterio-ration of SLM-316L-V in HF vapor. While a proper loading relationship can shield the adverse effect of dislocation cells on the stress corrosion of SLM-316 L (e.g. SLM-316L-H). Our effort s provide import ant theoretical guidance for the rational selection of fabrication technologies and microstructural design of materials in harsh environments.

Key words: 316 L, Selective laser melting, Directed energy deposition, Stress corrosion cracking, Dislocation cell