Effects of the electrolytes on the electrochemical behavior of nickel-base superalloys prepared by laser directed energy deposition

The electrochemical behavior of Inconel 718 prepared by laser directed energy deposition with single γ-phase and dual (γ + γ″)-phase was investigated using 10 wt% NaNO₃, 5 wt% NaNO₃ + 5 wt% NaCl and 10 wt% NaCl, respectively. It is found that the Cl^- ion weakens the inhibitive effect of the transpassive film, resulting in a uniform electrochemical dissolution for deposits with the single γ-phase, but an inferior surface quality for deposits with the dual (γ + γ″) phases due to the γ″ phase inducing uneven pits expansion. Two qualitative models are proposed to demonstrate their electrochemical dissolution mechanism.