Initial Study of the Relative Localized Corrosion Susceptibility of Additively Manufactured and Wrought Corrosion Resistant Alloys
Abstract
Additively manufactured alloys (AMA) offer many potential benefits for theconstruction of engineering components, from reducing was"te and time-toavailabilityto the opportunity for radically new mechanical designs which cannot beconstructed from conventionally p"rocessed stock products (e.g., plate, rod, sheet).They also may allow the introduction of graded composition within components.Cor""rosion resistant alloys (e.g., stainless steels, nickel alloys, titanium alloys) areoften the base material from which AMA parts ar"e constructed. The rapiddevelopment of additive manufacturing (AM) processes has outpaced efforts tocharacterize the performance o"f the materials so created, particularly with regard totheir resistance to corrosion. It is generally assumed that the componentma"nufactured by AMA will have a corrosion resistance equivalent to that ofcomponents manufactured from wrought materials of the same" nominalcomposition. However, the highly non-equilibrium nature of AM processes resultsin complicated microstructures, composition""al heterogeneities, and surfacestructures that can all influence corrosion resistance, potentially beneficially ordetrimentally. T"he introduction of components manufactured by AM into servicecarries with it an unknown level of risk for failure by corrosion processes. Afundamental understanding of the means by which AM processing interacts withcorrosion resistance is required to allow risks to be mitigated and AMAs to reachtheir tremendous potential. This work will focus on testing two major hypothesesthat propose to explain the reduced resistance to localized corrosion of AM 316Land AM 625 relative to their wrought counterparts: (a) the very fine porosity that ispresent on the as-manufactured surfaces of AMA components serves as localizedcorrosion resistance sites akin to" very tight crevices; and (b) heterogeneousdistribution of key alloying elements occurs during the AM process, leading to areaslea""n in Cr, Ni, or Mo, making these sites more susceptible to dissolution. The resultsof this preliminary study would be used to infor"m the design of a larger scale effortthat would focus on extending this work to other forms of corrosion attack as wellas provide" a scientific basis for understanding the factors that control the effects ofAMA defects, including the role of porosity connectedn""ess, on corrosion behavior.Although this work will focus on Alloy 625 and Type 316L stainless steel, itsfindings will be extendabl""e to localized corrosion susceptibility of AMAs moregenerally. Finally, this work could be connected to efforts to exploit the proc"essmicrostructure-chemical/electrochemical properties linkages leading to afundamental understanding of corrosion mechanism in AMAs to enable design ofcorrosion resistant AMAs.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2017
- Source ID
- N000141712533
Entities
People
- Robert M. Kelly
Organizations
- Office of Naval Research
- United States Navy
- University of Virginia