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<p>Inconel 617 (IN617) is a high-performance nickel-based superalloy widely used in extreme environments. However, its adoption in Laser Directed Energy Deposition (LDED) remains limited due to a lack of understanding of how thermal input influences microstructural evolution during additive manufacturing. This study investigates the effect of laser energy per unit length (LEL) on the grain structure, crystallographic orientation, boundary characteristics, porosity, and hardness of LDED-processed IN617. At lower LEL, rapid solidification drives the formation of fine columnar grains (~ 32&#xa0;μm), strong [001] texture, and a high fraction of Σ3 twin and high-angle grain boundaries. These features, combined with minimal porosity, enhance grain-boundary strengthening and directional alignment, contributing to a hardness of 234 HV. As LEL increases, prolonged thermal exposure reduces cooling rates, leading to grain coarsening (~ 56&#xa0;μm), breakdown of twin boundaries, elevated low-angle grain boundary fractions, and reduced texture intensity. Simultaneously, increased thermal input promotes the formation of large, interconnected pore networks, further compromising mechanical integrity. This microstructural coarsening and porosity accumulation diminish the effectiveness of boundary strengthening, resulting in lower hardness (~ 216 HV). Kernel misorientation distributions corroborate these transitions, revealing elevated substructure formation at higher LEL. Overall, this work offers key insights into the process–structure–property relationships that govern IN617 during LDED and provides a framework for optimising processing strategies for high-performance structural applications.</p>

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Elucidating the process–structure–property relationships in laser directed energy deposition based additive manufacturing of Inconel 617 structures

  • 期刊论文

  • 发表日期：

    2026年4月2日

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  • Jinoop Arackal Narayanan,
  • Denny John,
  • Sam Morten,
  • C. P. Paul,
  • Sean John,
  • Helen Davies,
  • Chameekara T. Wanniarachchi,
  • Manpreet Singh,
  • John Robinson,
  • Arun Arjunan

摘要

Inconel 617 (IN617) is a high-performance nickel-based superalloy widely used in extreme environments. However, its adoption in Laser Directed Energy Deposition (LDED) remains limited due to a lack of understanding of how thermal input influences microstructural evolution during additive manufacturing. This study investigates the effect of laser energy per unit length (LEL) on the grain structure, crystallographic orientation, boundary characteristics, porosity, and hardness of LDED-processed IN617. At lower LEL, rapid solidification drives the formation of fine columnar grains (~ 32 μm), strong [001] texture, and a high fraction of Σ3 twin and high-angle grain boundaries. These features, combined with minimal porosity, enhance grain-boundary strengthening and directional alignment, contributing to a hardness of 234 HV. As LEL increases, prolonged thermal exposure reduces cooling rates, leading to grain coarsening (~ 56 μm), breakdown of twin boundaries, elevated low-angle grain boundary fractions, and reduced texture intensity. Simultaneously, increased thermal input promotes the formation of large, interconnected pore networks, further compromising mechanical integrity. This microstructural coarsening and porosity accumulation diminish the effectiveness of boundary strengthening, resulting in lower hardness (~ 216 HV). Kernel misorientation distributions corroborate these transitions, revealing elevated substructure formation at higher LEL. Overall, this work offers key insights into the process–structure–property relationships that govern IN617 during LDED and provides a framework for optimising processing strategies for high-performance structural applications.