Strong Impact of Minor Elements on the Microstructural Evolution of an Additively Manufactured Inconel 625 Alloy

Mo Rigen He*, Arunima Banerjee, Christopher J. Marvel, Sam Price, Ian McCue, Edwin J. Schwalbach, Kevin J. Hemker

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Inconel 625, whereas designed as a single-phase solid-solution-strengthened alloy, is prone to formation of various precipitate phases under processing or service conditions. When this alloy is fabricated with additive manufacturing, the enhanced segregation of alloying elements to grain boundaries, interdendritic regions, or dislocation cores can influence microstructural evolution and modify local precipitation pathways. In this study, an Inconel 625 made with laser powder-bed fusion is characterized with comprehensive electron microscopy techniques combined with thermodynamic calculations, with emphasis on element segregation, precipitate formation, and their relation to the columnar sub-grains associated with additive manufacturing. Enrichment of both major (Nb, Mo) and minor (Si, N) solutes at dislocation cell walls is observed in the as-built samples, whereas stress-relief heat treatments promote formation of two types of globular precipitates, i.e., (Nb, Mo, Si, N)-rich M6X and (Nb, N)-rich MX. Absence of the detrimental, needle- or plate-shaped δ-Ni3(Nb, Mo) phase leads to improved mechanical properties and is attributed to the higher concentrations of Si and N at cell walls, although the overall composition remains within the standard range for powder-bed fused alloys. These new insights into the critical role of minor alloying elements provide a potent guide for the design and processing of additively manufactured metallic materials.

Original languageEnglish (US)
Pages (from-to)2926-2942
Number of pages17
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume53
Issue number8
DOIs
StatePublished - Aug 2022

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys

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