The austenitic stainless steel 316L was additively manufactured using Selective Laser Melting (SLM). The corrosion characteristics of the additively manufactured (3D printed) specimens were investigated by both potentiodynamic and potentiostatic techniques. The production parameters were deliberately varied during SLM, to produce 316L specimens fabricated by different laser scan speed (in the range of 860-1160 mm/s) and laser power (in the range of 165-285 W). The fabrication parameters were found to influence the porosity of the resulting specimens. The pitting potentials, metastable pitting rates and repassivation potentials of the 3D printed specimens are presented herein as a function of the laser scan speed and laser power, and also discussed in the context of specimen porosity. The corrosion characteristics of the 3D printed 316L were also compared with wrought 316L, revealing higher pitting potentials and lower rates of metastable pitting for most SLM 316L specimens, the related concepts of which are discussed herein. Stainless steels are a critically important class of alloy in several industries.1 The corrosion resistance of stainless steel (SS) is attributed to the presence of alloyed chromium (> ∼11 wt%), enabling the formation of a chromium oxide (Cr 2 O 3 ) based passive film upon the metal surface.1-3 The addition of elements such as nickel, nitrogen, molybdenum, carbon, aluminum, copper, sulfur and selenium can modify the corrosion resistance, strength, ductility, machinability, and the phases present (and their stability) in stainless steels.1-3 The types of stainless steel are most conveniently categorized according to their microstructure, classified as: austenitic, martensitic, ferritic and austenoferritic (duplex). Such structures are realized by specific alloying additions and metallurgical processing.1-4 Additive manufacturing has recently been explored as a means to produce SS components in net shape, 5-7 circumventing the requirement of traditional manufacturing methods such as casting, rolling, welding, machining, forging, etc. Selective Laser Melting (SLM) is one such additive manufacturing method, which can produce dense products by laser processing of metal powders. In SLM, metal powder layers are successively fused in a layer-by-layer manner into the requisite 3D structure, employing a fiber laser. [8][9][10][11] The metallic component in essence is therefore 3D printed into the requisite shape, by additive manufacturing processes like SLM. The process takes place in chamber of well-controlled inert atmosphere (either nitrogen or argon). The primary parameters that govern the microstructure of a 3D printed specimen are the laser power and the laser scan speed, as they influence the thermal gradients and growth rate of the metal at the solid-liquid interface (in the melt pool). 12 The porosity that may develop in 3D printed specimens depends upon the heating and cooling rates of the melt pool. 13 The laser scan speed relates to the duration for which the laser beam is in contact with ...

Additive manufacturing (AM), often termed 3D printing, has recently emerged as a mainstream means of producing metallic components from a variety of metallic alloys. The numerous benefits of AM include net shape manufacturing, efficient use of material, suitability to low volume production runs, and the ability to explore alloy compositions not previously accessible to conventional casting. The process of AM, which is nominally performed using laser (or electron) based local melting, has a definitive role in the resultant alloy microstructure. Herein, the corrosion of alloys prepared by AM using laser and electronbased methods, relating the corrosion performance to the microstructural features influenced by AM processing, are reviewed. Such features include unique porosity, grain structures, dislocation networks, residual stress, solute segregation, and surface roughness. Correlations between reported results and deficiencies in present understanding are highlighted.

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