κ-phase precipitation in nickel-aluminum bronze alloy fabricated by oscillating laser wire additive manufacturing

Abstract

High-strength, corrosion-resistant nickel-aluminum bronze (NAB) is extensively employed in marine and offshore engineering applications. In this study, high-quality NAB alloy components are fabricated using oscillating laser wire additive manufacturing. The as-fabricated specimen exhibits excellent formation without porosity or cracking defects. The initial coarse columnar grains in the as-fabricated state are remelted and converted into fine equiaxed grains, driven by the intense agitation of the molten pool induced by the oscillating laser. Additionally, the effect of normalizing heat treatment (675 ℃ for 6 h) on the as-fabricated specimen is thoroughly investigated. After heat treatment, internal grain strain decreases, recrystallized grains increase, and texture strength weakens significantly, leading to reduced anisotropy. The ultimate tensile strength increases by 12.39% (626 MPa), with only a slight 1% reduction in elongation (16.5%), while hardness rises by 13.03% (182.93 HV), attributed to the large increase in fine κ-phase precipitates. However, corrosion resistance decreases after heat treatment, attributed to the increase in κ-phase precipitates and the reduction in Σ3 grain boundaries. This study demonstrates that oscillating laser wire additive manufacturing, combined with appropriate heat treatment, offers an alternative solution for fabricating high-performance NAB alloy.