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<p>This study integrates experimental characterization and numerical modeling to establish processing–microstructure–corrosion correlations in SA-DED Inconel 718. SA-DED-fabricated Inconel 718 exhibits directionally solidified, columnar dendritic morphology with segregation-induced phase heterogeneity, consistent with its cyclic thermal history and high-heat-input deposition environment. Electrochemical testing in 3.5&#xa0;wt.% NaCl showed limited passivation in the as-deposited state, with higher corrosion current and lower charge-transfer resistance due to galvanic activity between segregated phases and the γ-matrix. Post-polarization FESEM imaging across magnifications (1649×–116,785×) confirmed localized corrosion driven by pit nucleation, passive-film rupture, and micro-crack formation, progressing to intergranular and transgranular crack propagation along Nb-rich networks. A multistage homogenization–solutionizing–aging heat treatment dissolved Laves phases, homogenized Nb distribution, and promoted γ′/γ″ precipitation, resulting in a more stable Cr<sub>2</sub>O<sub>3</sub>–NiO–Nb<sub>2</sub>O<sub>5</sub> passive film and markedly improved corrosion resistance. Combined regression and Pareto analysis identified optimal deposition parameters that minimize thermal load while enhancing build quality. This integrated framework offers a predictive basis for optimizing flux selection, heat treatment, and processing conditions to achieve corrosion-resistant DED-processed Inconel 718 components.</p>

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Microstructure, Phase Evolution, and Corrosion Resistance of SA-DED-Fabricated Inconel 718 Slabs: Experimental Study

  • 期刊论文

  • 发表日期：

    2026年4月6日

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  • Mahendra Singh,
  • Ajay Biswas

摘要

This study integrates experimental characterization and numerical modeling to establish processing–microstructure–corrosion correlations in SA-DED Inconel 718. SA-DED-fabricated Inconel 718 exhibits directionally solidified, columnar dendritic morphology with segregation-induced phase heterogeneity, consistent with its cyclic thermal history and high-heat-input deposition environment. Electrochemical testing in 3.5 wt.% NaCl showed limited passivation in the as-deposited state, with higher corrosion current and lower charge-transfer resistance due to galvanic activity between segregated phases and the γ-matrix. Post-polarization FESEM imaging across magnifications (1649×–116,785×) confirmed localized corrosion driven by pit nucleation, passive-film rupture, and micro-crack formation, progressing to intergranular and transgranular crack propagation along Nb-rich networks. A multistage homogenization–solutionizing–aging heat treatment dissolved Laves phases, homogenized Nb distribution, and promoted γ′/γ″ precipitation, resulting in a more stable Cr2O3–NiO–Nb2O5 passive film and markedly improved corrosion resistance. Combined regression and Pareto analysis identified optimal deposition parameters that minimize thermal load while enhancing build quality. This integrated framework offers a predictive basis for optimizing flux selection, heat treatment, and processing conditions to achieve corrosion-resistant DED-processed Inconel 718 components.