Nanocatalyst-Driven Sustainable Electrochemical Machining

Electrochemical machining (ECM) is an advanced, non-traditional machining process that employs high current and low voltage to remove material from electrically conductive workpieces through anodic dissolution. In the case of alloy steels like 20MnCr5, operating at elevated current densities can lead to the formation of adherent and passivating oxide layers on the workpiece surface. These oxide films, typically around 10 nm thick, form a supersaturated, high-field layer that not only consumes a significant portion (approximately 20%) of the anodic charge due to oxygen evolution but also impedes effective ion transport, decreasing the conductivity of the electrolyte and consequently the metal removal rate (MRR). To address this challenge, this study investigates the electrocatalytic role of gold nanoparticles (AuNPs) in enhancing anodic dissolution during ECM. Specifically, the work explores how the performance of AuNPs in oxygen reduction reactions (ORR) depends on their particle size. Two distinct size ranges of AuNPs (28-40 and 150-180 nm) were dispersed in the basic NaNO 3 electrolyte at a concentration of 100 cc per unit volume. Experimental observations revealed that the inclusion of AuNPs improved the metal removal rate by facilitating ORR but also contributed to a significant enhancement in surface finish by suppressing oxide film formation. Comparative results between the two particle size ranges suggest that the catalytic efficiency of AuNPs is strongly size dependent, with smaller particles offering more active surface area for ORR. This study highlights the potential of nanocatalyst-based electrolyte modification as an effective strategy for improving ECM performance.