Electrochemical behavior of laser powder bed fused nickel aluminum bronze: As-built and tempered alloys

Nickel-aluminum bronze (NAB), as an attractive material for the marine industry in corrosive environments, was considered for additive manufacturing (AM) through the laser powder bed fusion (LPBF) technique. A fully martensitic microstructure was developed from the LPBF process due to high cooling rates inherent in the process. In addition, different heat treatment procedures applied on the samples. These two sets of samples possessed different k -phases in the microstructure with various morphologies along with martensitic packs and laths boundaries. The fully martensitic structure of the alloy in as-built and heat treated conditions were considered for electrochemical testing. The results showed a superior corrosion resistance for the alloy in the as-built condition, accrediting to the development of a protective passive surface film and supersaturated structure of alloying elements on the sample. In addition, the tempering precipitation procedure increased the alloy’s corrosion rate due to the accelerated boundary/interface corrosion effect. • The as-built NAB alloy displayed the highest resistance to corrosion due to its super-saturated martensitic structure. • The annealing process increases the number of defects in the passive film after exposing to corrosive solution. • Different corrosion behaviors for HT-1 and HT-2 samples exhibited in progress of martensitic tempering by annealing temperature and time. • For long-term corrosion tests, the corrosion rate reduces at higher times for all three states of processing. • Copper and aluminum have a significant role in formation of protective film which leads to improving the corrosion resistance.