Chloride Induced Secondary Passive Film Failure for Laser Additive Manufacturing Nickel-Based Superalloys during Electrochemical Machining

We investigated the influence of chloride on the secondary passive film (SPF) on laser directed energy deposition Alloy 718 during electrochemical machining. The results show that SPF formed in chloride-containing electrolyte is more defective than that formed in chloride-free solution, due to the stepped-up cation ejection by chloride. Chloride accelerates the SPF failure via enhanced cation vacancy condensation, SPF dissolution and possibly via surface vacancy pairs’ coalescence, restraining the formation of CrO 3 and inducing a better surface quality than does the chloride-free electrolyte. Based on the Point Defect Model, a mechanism describing the influence of chloride on SPF was developed.