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<p>This study investigates the microstructural evolution and corrosion behaviour of a CoCrFeMnNi high-entropy alloy (HEA) weld overlay applied to additively manufactured Inconel 718 (IN718) for high-temperature solar concentrator tube applications. Potentiodynamic polarization tests in 3&#xa0;M NaCl solution revealed that the as-built AM IN718 exhibited a corrosion rate of 16.30 mils/year, indicating superior resistance in aqueous chloride media. In comparison, the HEA overlayed IN718 exhibited a more negative E<sub>corr</sub> (- 0.633&#xa0;V), higher I<sub>corr</sub> (2.314X10<sup>−6</sup> A), lower Rp (9920.8 Ω-cm<sup>2</sup>), and an elevated corrosion rate of 49.66 mils/year, relative to AM IN718 (-0.526&#xa0;V, 6.827X10<sup>−7</sup> A, 35,078.9 Ω-cm<sup>2</sup>, and 16.30 mils/year, respectively). For high-temperature assessment, specimens were exposed to molten LiCl–KCl-EuCl<sub>3</sub> salt at 500&#xa0;°C for 96&#xa0;h. Under molten salt conditions, the HEA weld overlay significantly enhanced corrosion resistance as reflected by the reduced mass gain of 0.34&#xa0;g/cm<sup>2</sup> compared to uncoated IN718, which recorded a mass gain of 0.95&#xa0;g/cm<sup>2</sup>. Microstructural characterization demonstrated pronounced grain refinement, formation of stable phases, and suppression of oxygen and chlorine ingress within the HEA-coated region. The overlay effectively mitigated salt-induced degradation and preserved substrate integrity. Hence, CoCrFeMnNi HEA weld overlay is a promising surface engineering approach to extend the service life of IN718 components in aggressive, high-temperature environments.</p> Graphical abstract <p></p>

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High-entropy alloy cocrfemnni weld overlay for additive manufactured IN718: a microstructural and molten-salt corrosion study for concentrated solar powerplant applications

  • 期刊论文

  • 发表日期：

    2026年1月13日

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  • R. Abhiram,
  • Sudheer Reddy Beyanagari,
  • R. Vaira Vignesh,
  • M. Govindaraju,
  • P. S. Samuel Ratna Kumar,
  • K. Rajesh Kannan,
  • Kamel Moussaoui,
  • Redouane Zitoune

摘要

This study investigates the microstructural evolution and corrosion behaviour of a CoCrFeMnNi high-entropy alloy (HEA) weld overlay applied to additively manufactured Inconel 718 (IN718) for high-temperature solar concentrator tube applications. Potentiodynamic polarization tests in 3 M NaCl solution revealed that the as-built AM IN718 exhibited a corrosion rate of 16.30 mils/year, indicating superior resistance in aqueous chloride media. In comparison, the HEA overlayed IN718 exhibited a more negative Ecorr (- 0.633 V), higher Icorr (2.314X10−6 A), lower Rp (9920.8 Ω-cm2), and an elevated corrosion rate of 49.66 mils/year, relative to AM IN718 (-0.526 V, 6.827X10−7 A, 35,078.9 Ω-cm2, and 16.30 mils/year, respectively). For high-temperature assessment, specimens were exposed to molten LiCl–KCl-EuCl3 salt at 500 °C for 96 h. Under molten salt conditions, the HEA weld overlay significantly enhanced corrosion resistance as reflected by the reduced mass gain of 0.34 g/cm2 compared to uncoated IN718, which recorded a mass gain of 0.95 g/cm2. Microstructural characterization demonstrated pronounced grain refinement, formation of stable phases, and suppression of oxygen and chlorine ingress within the HEA-coated region. The overlay effectively mitigated salt-induced degradation and preserved substrate integrity. Hence, CoCrFeMnNi HEA weld overlay is a promising surface engineering approach to extend the service life of IN718 components in aggressive, high-temperature environments.

Graphical abstract