적층제조 된 316L 스테인리스강의 염수 분위기에서의 기계적 특성

Abstract

Since the application of additive manufacturing with stainless steels expands to extreme conditions (e.g. oceanic and polar), sustainability in moist and salty environments becomes an important issue. Thus, in this study, the mechanical properties of additively manufactured 316L SS under conventional NaCl solution is investigated. The significant heat input from directed energy deposition (DED) induces both coarse grains and cell size in the austenitic matrix, which results in more active planar slip behavior compared with the sample manufactured by powder bed fusion (PBF). Under 3.5% NaCl solution, a little hydrogen infiltration occurs, and the dislocation cells not only act as preferential hydrogen diffusion paths but also suppress the hydrogen concentration at specific boundaries. Consequently, the PBF sample exhibits lower hydrogen content per unit boundary than the DED sample, thus resulting in ductility conservation in the PBF sample at a salty condition. In addition, infiltrated hydrogen enhances the slip planarity, thus providing extra-planar slip bands initiation under NaCl solution. Because of the enhanced slip planarity, both strain-hardening enhancement and prolonged ductility can evolve, even in the NaCl solution. This result demonstrates that the appropriate defect structure in AM alloys will be helpful to sustain in the oceanic environment without severe degradation.