Fracture Toughness of As-Deposited Nickel-Aluminum Bronze Produced by WAAM

Nickel-aluminum bronze (NAB) is an excellent alloy for seawater service due to its unique combination of mechanical strength, corrosion resistance, and antifouling properties. When processed by wire arc additive manufacturing (WAAM), NAB alloys exhibit comparable or even superior properties to their cast counterparts. However, the fracture toughness of these alloys remains only partially characterized, despite being a critical property for structural integrity assessments of cracked components under loading conditions. This study focused on the experimental evaluation of the fracture toughness of as-deposited WAAM NAB alloys with cracks oriented in three perpendicular directions, as well as the determination of their tensile properties in two directions. The experimental results indicate that the tensile properties of the as-deposited material generally meet the requirements of relevant ASTM standards for cast NAB, although the ductility (expressed as %EL) in the vertical direction (across the layers) was slightly below the standard limit. In contrast, the fracture toughness under the described conditions can be considered high compared to values reported in the literature for similar alloys. The average JIc was 99 kJ/m2 for cracks in the plane of the deposited layers, and 109 and 111 kJ/m2 for the other two directions. These results indicate a low level of anisotropy from a fracture toughness perspective.