Dissolution Effects with Different Microstructures of Inconel 718 on Surface Integrity in Electrochemical Machining

Abstract

Inconel 718, a nickel-based superalloy widely used in the aviation field, is difficult to machine using traditional methods such as milling. Electrochemical machining (ECM) is a recommended manufacturing method forInconel 718 due to its effective and economical processing characteristics. This paper investigates the dissolution effects on surface integrity in ECM of Inconel 718. Two types of materials with different heat treatments, solid solution, and solution and aging were studied to analyze their electrochemical behavior. They have different metallographic microstructures and precipitate phases. There are many Laves phase (Fe2Nb), δ phase (Ni3Nb), and carbides in material of solid solution state, while there are fewer in material of solution and aging state. Experiments were then performed on these materials under identical ECM conditions. The results show that the surface roughness of the solid-solution material was about Ra 1.378 μm while it was Ra 0.188 μm for the solution and aging material. A dissolution model was proposed to illustrate the electrochemical behavior of solid solution Inconel 718, revealing that the uneven distribution of the metallographic phase and the rich content of the element niobium (Nb) will influence the surface integrity of the ECMed sample.