Enhanced localized corrosion resistance of Ni-based alloy 625 processed by directed energy deposition additive manufacturing

Abstract

We report a significant improvement in localized corrosion resistance of Ni-based alloy 625 processed by directed energy deposition (DED) in 7.6 mol/L LiCl at 50 oC. Disparities observed in polarization behavior between DED and wrought alloy 625 are analyzed through compositional and microstructural differences. The exceptional localized corrosion resistance of the DED alloy likely stems from the refinement of secondary phases resultant from the DED process. The prototypical precipitates larger than ≈1 μm in the wrought material, primarily Nb,Ti-enriched face centered cubic nitrides with the stoichiometry of MN where M = Nb, Ti, Cr, served as pit initiation sites and likely degraded the corrosion resistance.