Localization of the Anodic Dissolution of Inconel 718 by Using an Electrodeposited Nickel Film

Abstract

In electrochemical machining (ECM), the machining accuracy is to a great extent affected by the stray corrosion at low current density. In this paper, an electrodeposited nickel film is used to localize the anodic dissolution of Inconel 718 in counter-rotating ECM (CRECM). The anodic dissolution behavior of nickel in NaNO3 solution is investigated by linear sweep voltammetry, cyclic voltammetry, and dissolution efficiency measurement, and the surface evolution process is monitored by using a charge-coupled device. The results indicate that nickel is a favorable material with desired passivation characteristic that can be used for the localization of anodic dissolution of Inconel 718 in CRECM. The cylindrical Inconel 718 workpiece is covered by a thin nickel film, and is tested in the CRECM experiment. The experimental results show that the electrodeposited nickel film on the cylindrical surface can be rapidly dissolved under high current density. In contrast, the nickel film on the low-current-density area can be well reserved, and thereby protect the surface of the convex structure from stray corrosion. As a result, the anodic dissolution of Inconel 718 is located merely in the high-current-density region, and the surface quality and the profile of the convex structure are significantly improved.