Laser powder bed fusion processing of UNS C63020 nickel aluminum bronze powder

Nickel aluminum bronze (NAB) alloys are widely used in marine applications due to their high strength and superior corrosion resistance in sea water. NAB components, such as propellers and seawater valves, are traditionally manufactured using casting techniques and exhibit complex microstructures consisting of intermetallic kappa-phase precipitates distributed in alpha and beta solid solution phases. Laser powder bed fusion (LPBF) is an additive manufacturing technique that selectively fuses layers of metal powders into a desired part geometry. Materials processed using LPBF generally experience very high cooling rates, which lead to a refinement of the microstructure and better control of phase precipitation through subsequent heat treatments. As a result, NAB alloys processed via laser AM techniques have exhibited improved strength and corrosion properties. In the present work, a fully pre-alloyed NAB powder corresponding to UNS C63020 chemistry was processed using LPBF. Solid test specimens were fabricated via LPBF processing using a linear manipulation of the laser power and scan speed while holding the hatch spacing and spot size constant. The densities of the as-printed test specimens were measured and the microstructures were analyzed using laser confocal microscopy. A LPBF parameter set which produced high-density NAB was selected for heat treatment and tensile property investigation. An effective heat treatment temperature was identified for LPBF NAB which produced superior tensile properties to wrought NAB.