Ultrasonic fatigue of wire arc additive manufactured (WAAM) nickel-Aluminum bronze (NAB): ex-situ corrosion

• Corrosion-induced pitting dominated crack initiation over WAAM internal defects. • Pre-corroded specimens failed in the HCF regime with no cracks from internal flaws. • At low stress, fatigue showed a binary response: early failure or run-out. • Ultrasonic fatigue testing proved fast and reliable for corrosion fatigue studies. The application of nickel-aluminum bronze (NAB) in marine and corrosive environments necessitates a thorough understanding of their fatigue behavior under extreme conditions. This study examines the ultrasonic fatigue performance of wire arc additive manufacturing (WAAM) NAB alloy in corrosive environments. The specimens were manufactured using optimized process parameters and subsequently annealed to improve mechanical properties and reduce residual stresses. Ultrasonic fatigue testing, operating at frequencies near 20 kHz, enables high-throughput fatigue testing, making it suitable for evaluating components subjected to prolonged service lifetimes. This research aims to evaluate the material’s fatigue life, crack initiation mechanisms, and overall durability by analyzing its response to corrosion. The results indicated that, unlike the failure mechanism observed in ambient air, where cracks were initiated from internal defects, none of the specimens in this study exhibited crack initiation from internal defects. Instead, fatigue cracks consistently initiated at the surface, highlighting that corrosion effects dominated the fatigue failure mechanism. Pitting played a key role in crack initiation, resulting in a significant reduction in the fatigue life of all specimens. These findings contribute to optimizing material design and processing for improved performance in real-world applications. Additionally, this research underscores the potential of ultrasonic fatigue testing as a fast and reliable method for evaluating the performance of additive manufacturing components in harsh operational environments.