Effect of composition on the tensile and corrosion performance of nickel aluminium bronze produced via laser powder bed fusion

Nickel Aluminium Bronze (NAB) is a key material for marine applications due to its combination of high strength and superior corrosion resistance in seawater. While wrought components show enhanced strength and corrosion resistance compared to their cast equivalent, casting is often required in order to achieve necessary component shapes. This study investigates the potential manufacturing of NAB components through laser powder bed fusion (L-PBF), which is known for its ability to create highly complex designs. NAB powders with compositions C63000 (Cu-10.2Al-4.8Fe-5.0Ni-0.2Si, wt%) and C95800 (Cu-9.0Al-4.0Fe-4.6Ni-1.9Mn, wt%), were tested for their manufacturability, mechanical performance, and corrosion behaviour in both as-built and heat treated conditions. As-built NAB shows a dominant β′ martensitic structure, which is unique to L-PBF due to the rapid heating/cooling rates of laser processing and leads to very high strength in excess of 1100 MPa but brittle performance. After heat treatment, the β′ decomposes into lamellar κIII which breaks down into a dense mixture of laths and particles through spheroidization. This allows AM NAB to attain the same tensile and corrosion behaviour as the wrought equivalent. As built C95800 has greater elongation but lower strength and worse corrosion performance compared to NAB owing to the formation of continuous soft and ductile α bands around β′ grains. After heat treatment, the prior α regions correspond to globular nickel rich spheroids and iron rich precipitates similar to κIV. This causes heat treated C95800 to show similar tensile performance to cast NAB, while the corrosion behaviour remains similar to wrought.