A holistic corrosion understanding in IN625 alloy based on additive manufacturing history and microstructure modification

Abstract

Alloy design for harsh environments, such as Nickel-based IN625, is critically contingent on deciphering the process-microstructure-corrosion linkages inherent to additive manufacturing (AM) techniques. While prior research has emphasized the advantages of AM over conventional manufacturing, a limited understanding persists regarding how distinct AM methodologies, e.g., laser powder bed fusion (LPBF), wire directed energy deposition (DED), and wire arc additive manufacturing (WAAM), influence corrosion performance, impeding corrosion-targeted strategic selection of AM procedures. This study systematically investigates the microstructural evolution of as-built IN625 produced via LPBF, wire-DED, and WAAM, correlating processing histories with microstructural features (e.g., grain morphology, element segregation, and unavoidable defects) and resultant distinct corrosion behavior. Our key findings demonstrate that LPBF IN625 exhibits superior corrosion resistance compared to both DED and WAAM counterparts, attributable to refined grain structures, enhanced solid-solution element distribution, and minimal defects. However, WAAM specimens witness a significant variability in corrosion resistance across different WAAM history accompanied by element segregation. Accelerated galvanic corrosion in WAAM components can be further linked to Titanium (Ti) segregation within Laves phases, promoting higher micro-galvanic activity. DED, with less controllability for defects like porosity, unfortunately further sacrifices its corrosion resistance. Crucially, this work introduces a quantitative predictive framework, correlating grain size, secondary phase distribution, and porosity defects with corrosion kinetics through an extended empirical model. These insights advance the fundamental understanding of AM process-microstructure-corrosion relationships, enabling physics-driven optimization of AM parameters to tailor IN625 components for demanding corrosive environments from aerospace to energy systems.