Studies on Electrochemical Machining of Heat-Resistant Nickel-Base Alloys

Anodic Dissolution Properties of Commercial Alloys

Abstract

The anodic properties involved in electrochemical machining of four heat-resistant nickel-base alloys and pure nickel were studied in NaCl and NaNO₃ solutions. The polarization curve and dissolution current efficiency were measured in a flow channel cell. The results show that during electrochemical machining of Inconel 718 and Hastelloy X, anodic dissolution occurres only in the transpassive state and that the dissolution current efficiencies of these alloys are about 100% independent of the current densities in NaCl and NaNO₃ solutions. From the above results it is estimated that in electrochemical machining of these alloys, good dimensional control cannot be achieved even in NaNO₃ solution. The influences of the alloy composition on the anodic properties were discussed briefly.