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<p>Advanced additive manufacturing technology of laser powder bed fusion (LPBF) enables the production of metallic components for various applications. Thermomechanical post-processing is used for the LPBF-produced superalloys to eliminate various manufacturing defects and anisotropy. Controlling the anisotropy of elastic and mechanical properties by the formation of appropriate microstructure, texture, and phase state is crucial for responsible 3D-built products. In this study, a two-fold post-processing is applied to improve the LPBF-built Inconel 718 alloy samples. The outcomes of the thermal post-processing, i.e., hot isostatic pressing (HIP), solution annealing / homogenization, double aging hardening, and mechanical surface post-processing using advanced multi-pin ultrasonic impact treatment (UIT) were studied. The microstructure was analysed using scanning electron (SEM) and transmission electron (TEM) microscopy. The elastic and mechanical properties were evaluated using the ultrasonic non-destructive analysis. In contrast to the LPBF-built IN 718 sample with predominantly elastic isotropy, the thermally post-processed samples using HIP followed by the double annealing with or without intermediated homogenization revealed elastic anisotropy (5–6%) for Young and shear moduli. SEM/TEM confirmed that sufficiently high hardness (<i>HV</i> = 5.9–6.1 GPa) and diminished plasticity (<i>δ</i><sub>H</sub>&#xa0;≈&#xa0;0.75–0.78) after post-fabrication heat-treatments are due to the precipitation strengthening by <i>γ</i>′ and <i>γ</i>′′ phases and carbide particles. The UIT finishing results in a further hardening and increase in the elastic anisotropy (~ 11–13%) both in near-surface layers and material volume owing to the severe plastic deformation and alternating component of ultrasonic tool load. Optimum combination of the heat treatment and UIT finishing can be chosen considering the observed microstructure and properties relationship.</p>

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Controlling microstructure, elastic anisotropy and mechanical properties of LPBF 3D-manufactured Inconel 718: Effects of post-fabrication heat-treatment and ultrasonic surface finishing

  • 期刊论文

  • 发表日期：

    2025年12月1日

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  • Bohdan Mordyuk,
  • Oleg Zaporozhets,
  • Vladyslav Mykhailovskyi,
  • Andrii Kotko,
  • Aitzol Lamikiz,
  • Dmytro Lesyk

摘要

Advanced additive manufacturing technology of laser powder bed fusion (LPBF) enables the production of metallic components for various applications. Thermomechanical post-processing is used for the LPBF-produced superalloys to eliminate various manufacturing defects and anisotropy. Controlling the anisotropy of elastic and mechanical properties by the formation of appropriate microstructure, texture, and phase state is crucial for responsible 3D-built products. In this study, a two-fold post-processing is applied to improve the LPBF-built Inconel 718 alloy samples. The outcomes of the thermal post-processing, i.e., hot isostatic pressing (HIP), solution annealing / homogenization, double aging hardening, and mechanical surface post-processing using advanced multi-pin ultrasonic impact treatment (UIT) were studied. The microstructure was analysed using scanning electron (SEM) and transmission electron (TEM) microscopy. The elastic and mechanical properties were evaluated using the ultrasonic non-destructive analysis. In contrast to the LPBF-built IN 718 sample with predominantly elastic isotropy, the thermally post-processed samples using HIP followed by the double annealing with or without intermediated homogenization revealed elastic anisotropy (5–6%) for Young and shear moduli. SEM/TEM confirmed that sufficiently high hardness (HV = 5.9–6.1 GPa) and diminished plasticity (δH ≈ 0.75–0.78) after post-fabrication heat-treatments are due to the precipitation strengthening by γ′ and γ′′ phases and carbide particles. The UIT finishing results in a further hardening and increase in the elastic anisotropy (~ 11–13%) both in near-surface layers and material volume owing to the severe plastic deformation and alternating component of ultrasonic tool load. Optimum combination of the heat treatment and UIT finishing can be chosen considering the observed microstructure and properties relationship.