Effect of pre-corrosion on the fatigue performance of direct energy deposited nickel–aluminum bronze (NAB)

This study investigates the ex-situ corrosion–fatigue response of nickel–aluminum bronze (NAB) fabricated via wire arc additive manufacturing (WAAM), a subset of directed energy deposition (DED). Fatigue tests were performed under fully reversed loading following controlled pre-corrosion exposure. Post-mortem fractography was employed to assess the influence of corrosion-induced surface degradation on crack initiation and fatigue life. Results showed that localized corrosion-pitting caused a pronounced shift in crack initiation sites from internal WAAM-caused volumetric defects to surface pits, leading to a substantial reduction in fatigue performance in the pre-corroded specimens relative to virgin (non-corroded) ones. Surface pits and internal volumetric defects competed as crack initiation sites, with surface pits dominating in most cases and only occasional contributions from large internal defects. Crack initiation was also frequently associated with additive layer bands, suggesting these interlayer regions are particularly susceptible to corrosion fatigue damage. The findings highlight the detrimental role of localized corrosion on the fatigue resistance of WAAM NAB and the need for effective surface protection strategies in corrosive environments like marine applications. • Ex-situ corrosion fatigue of WAAM nickel–aluminum bronze systematically studied. • Corrosion pits shift crack initiation from internal defects to the surface. • Fatigue strength drops 53% after pre-corrosion at 5×10 6 cycles. • Pre-corroded WAAM NAB shows strength comparable to virgin cast NAB. • Additive layer bands identified as preferential crack initiation sites.