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<p>This study investigates the anisotropic mechanical behavior and microstructural evolution of Inconel 825 walls fabricated using cold metal transfer (CMT)-based directed energy deposition (DED). Mechanical specimens were extracted along the build direction (Z), perpendicular direction (X), and 45° orientation (Y) to systematically evaluate orientation-dependent tensile, hardness, and impact properties. Radiographic examination confirmed defect-free interlayer bonding, validating the structural integrity of the fabricated wall. The Z-direction exhibited superior ultimate tensile strength (750&#xa0;MPa) and yield strength (540&#xa0;MPa), whereas the X-direction showed comparatively lower strength (UTS: 580&#xa0;MPa; YS: 410&#xa0;MPa). The Y-direction demonstrated intermediate behavior. Hardness followed a similar trend (Z &gt; X &gt; Y), consistent with columnar grain alignment along the build direction. However, impact toughness revealed an inverse trend, with the Z-direction exhibiting the lowest absorbed energy (40&#xa0;J), attributed to preferential crack propagation along aligned columnar grains under high-strain-rate loading. Optical and SEM analyses revealed fine equi-axed grains near the substrate transitioning to coarse columnar grains toward the top due to progressive thermal accumulation. SEM-EDS line scans indicated slight molybdenum enrichment and compositional gradients along the build height, contributing to localized solid solution strengthening and ductility variation. Fractographic analysis confirmed ductile dimple rupture under tensile loading and cleavage-dominated features under impact loading, highlighting orientation-sensitive failure mechanisms. A process–structure–property anisotropy framework is proposed to rationalize the thermally governed evolution of mechanical asymmetry in CMT-based DED Inconel 825. The findings establish that anisotropy (22–28%) arises from directional solidification, thermal gradients, and microstructural alignment intrinsic to arc-based additive manufacturing.</p>

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Mechanical Anisotropy in Additively Manufactured Inconel 825 Walls Fabricated Using Directed Energy Deposition

  • 期刊论文

  • 发表日期：

    2026年3月26日

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  • T. S. Senthil

摘要

This study investigates the anisotropic mechanical behavior and microstructural evolution of Inconel 825 walls fabricated using cold metal transfer (CMT)-based directed energy deposition (DED). Mechanical specimens were extracted along the build direction (Z), perpendicular direction (X), and 45° orientation (Y) to systematically evaluate orientation-dependent tensile, hardness, and impact properties. Radiographic examination confirmed defect-free interlayer bonding, validating the structural integrity of the fabricated wall. The Z-direction exhibited superior ultimate tensile strength (750 MPa) and yield strength (540 MPa), whereas the X-direction showed comparatively lower strength (UTS: 580 MPa; YS: 410 MPa). The Y-direction demonstrated intermediate behavior. Hardness followed a similar trend (Z > X > Y), consistent with columnar grain alignment along the build direction. However, impact toughness revealed an inverse trend, with the Z-direction exhibiting the lowest absorbed energy (40 J), attributed to preferential crack propagation along aligned columnar grains under high-strain-rate loading. Optical and SEM analyses revealed fine equi-axed grains near the substrate transitioning to coarse columnar grains toward the top due to progressive thermal accumulation. SEM-EDS line scans indicated slight molybdenum enrichment and compositional gradients along the build height, contributing to localized solid solution strengthening and ductility variation. Fractographic analysis confirmed ductile dimple rupture under tensile loading and cleavage-dominated features under impact loading, highlighting orientation-sensitive failure mechanisms. A process–structure–property anisotropy framework is proposed to rationalize the thermally governed evolution of mechanical asymmetry in CMT-based DED Inconel 825. The findings establish that anisotropy (22–28%) arises from directional solidification, thermal gradients, and microstructural alignment intrinsic to arc-based additive manufacturing.