Microstructure - corrosion performance correlation of laser directed energy deposited Inconel 625

Abstract

The primary objective of the current work is to understand the influence of process parameters on the corrosion performance of laser directed energy deposited Inconel 625 (IN625). In this regard, IN625 bulk samples were deposited using optimized laser power and three different scanning speeds. The as-deposited (AD) samples are named as AD-L, AD-M, and AD-H corresponding to low, medium, and high scanning speeds, respectively. Comprehensive microstructural characterization, microhardness evaluation, and electrochemical corrosion testing (medium: 3.5 wt% NaCl solution) were performed to correlate the process parameters with the microstructural features and corrosion performance. The results revealed that average grain size of the AD-H sample was lowered by 22.8 % and 19 %, respectively than the AD-L and AD-M samples, resulting in an enhancement of 8.4 % and 3.3 % in microhardness. Electrochemical corrosion tests indicated that AD-H sample possessed a higher corrosion potential (E<inf>corr</inf>) and a lower corrosion current density (I<inf>corr</inf>) when compared to other samples, confirming the corrosion resistance of the samples in the order of AD-H > AD-M > AD-L. The higher scanning speed resulted in finer grains, high dislocation density, and lowered volume fraction of secondary phases, which are attributed to superior corrosion resistance of the AD-H sample. Surface analysis of the corroded samples suggested a greater susceptibility to localized corrosion over pitting corrosion. The current work provides valuable insights to the correlation between process parameters, microstructure, and corrosion performance of LDED fabricated IN625, confirming notable influence of scanning speed on the corrosion behavior. © 2025 Elsevier B.V.