Unexpectedly High Corrosion Susceptibility Near Fusion Boundaries of Inconel 625 Manufactured by Laser Powder Bed Fusion

The intergranular corrosion (IGC) resistance of Inconel 625 produced by laser powder bed fusion was investigated according to ASTM-G28 method A. Unexpected severe corrosion near fusion boundaries was found. The initiation and expansion of corrosion along fusion boundaries and the relationship between microstructure and corrosion behavior were analyzed. This unusual corrosion behavior was related to the Volta potential variation near fusion boundaries. This Volta potential difference was caused by the Al2O3 nanoparticles and Mo, Nb-rich precipitates near the fusion boundaries. This finding may enhance the understanding of corrosion behavior of LPBFed nickel alloys.