Abstract
The corrosion of additively manufactured (AM) metallic materials, such as stainless steels (SS), is a critical factor for their qualification and reliable use. This review assesses the emerging knowledgebase of powder-based laser AM SS corrosion and environmentally assisted cracking (EAC). The origins of AM-unique material features and their hierarchal impact on corrosion and EAC are addressed relative to conventionally processed SS. The effects of starting material, heat treatment, and surface finishing are substantively discussed. An assessment of the current status of AM corrosion research, scientific gaps, and research needs with greatest impact for AM SS advancement and qualification is provided.
Highlights
Additive manufacturing (AM) has become desirable for manufacturing, complex, net-shape, and small batch metal parts across nearly every sector, from energy to medicine
Additive selective laser melting (SLM) and directed energy deposition (DED) alloys possess a cellular substructure with elemental microsegregation, the nature of which and its corrosion effects vary by process and alloy compositiondependent solidification behavior
The fine substructure imparted by SLM may act like that proposed for nanocrystalline metals—enhancing passivity in environments where it is operative and enhancing active dissolution in environments that promote it
Summary
Additive manufacturing (AM) has become desirable for manufacturing, complex, net-shape, and small batch metal parts across nearly every sector, from energy to medicine. Zeitala reported lower breakdown potential of DED 316L versus wrought, attributing the difference to the presence of δ and solute segregation.[5] These initial studies combined with those on autogenous laser fusion welds and laser surface melting, with similar microstructures, evidence larger and more numerous δ features accompanied by chemical microsegregation at the δ/γ interface can decrease corrosion resistance of austenitic SS.[58,59,60,61] This trend breaks down, when considering the large amount ferrite (e.g., 50%) in duplex SS which has a high corrosion resistance compared to austenitic SS despite similar pitting resistance equivalence number.[62,63] A holistic understanding of how the amount and distribution delta along with nature of δ/γ interfaces affects corrosion behavior is lacking. Mn-rich sulfide and Al, Mg, Mn, Si, Ca, Cr oxide inclusions are most common in conventionally produced SS and are known to act as preferential pit initiation sites.[70,71,72,73] The relatively fast solidification rates of DED and SLM processing suppress growth and
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