Electrochemical machining: The role of steel microstructure in high-rate anodic dissolution

Abstract

Electrochemical machining (ECM) of metals, particularly steels, plays an important role in many industrial microsystem technologies. This paper presents an overview of investigations into the anodic metal dissolution at high current densities of the technically important carbon steel 100Cr6 in aqueous NaCl- and NaNO3-electrolytes. The practice of ECM was simulated in flow channel experiments, where high current densities (up to 70 A/cm2) and turbulent electrolyte flow velocities (7 m/s) were applied. Insoluble carbide particles, enriching at the substrate surface, cause an apparent current efficiency > 100% in NaCl and > 67% in NaNO3 at high current densities. The role of the steel microstructure as controlled by its prior heat treatment is discussed with reference to a qualitative erosion-corrosion model proposed for the anodic dissolution process.