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 E corr (- 0.633 V), higher I corr (2.314X10 −6 A), lower Rp (9920.8 Ω-cm 2 ), 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-cm 2 , and 16.30 mils/year, respectively). For high-temperature assessment, specimens were exposed to molten LiCl–KCl-EuCl 3 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/cm 2 compared to uncoated IN718, which recorded a mass gain of 0.95 g/cm 2 . 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.
Abhiram et al. (Tue,) studied this question.