Boosting the corrosion resistance of NiCoV medium entropy alloy against various corrosive environments by laser powder bed fusion fabrication

NiCoV medium entropy alloy (MEA) has been fabricated by laser powder bed fusion (LPBF) method, and its improved corrosion resistance than the casting counterpart with cold-rolling and annealing is testified in various solutions, including acidic (H₂SO₄, pH = 0), salt (3.5 % NaCl), and basic (NaOH, pH = 13) solutions through immersion and electrochemical tests. The NiCoV MEA develops a VO₂-rich passive film in H₂SO₄ and NaCl solutions, and a Co(OH)₂-rich passive film in NaOH. In all solutions, the LPBF MEA shows higher corrosion resistance than casting one by developing a passive film with higher stability and fewer defects, which is caused by lower grain boundary density, specific texture and higher residual stress. Compared with other methods like adding alloying elements, LPBF is a more effective way of preparing NiCoV MEAs with improved corrosion resistance in various corrosive environments.