Influence of gaseous dielectrics on the wettability of Al-6061 alloy using dry µ-electrical discharge milling

Superhydrophobic surfaces have a wide range of applications in multi-disciplinary fields. Researchers have employed various methods to meet the growing demand for superhydrophobic surfaces on metals, with EDM being a commonly used technique. Changes in surface texture and chemical composition are crucial in transforming EDM-machined surfaces. The choice of dielectric in EDM significantly influences surface wettability. This study specifically investigates the impact of gaseous dielectrics on the surface wettability of Al-6061 alloy under atmospheric conditions. Samples machined in an oxygen environment exhibit a surface roughness (Sa) of 4.68 µm, which is 73.3% higher than the Sa observed in an argon environment. Energy Dispersive X-ray Analysis shows a higher O/Al ratio of 0.80 for oxygen-machined samples, which is 73.9% higher than that for argon-machined samples, indicating the presence of more hydrophilic compounds such as AlO(OH) and Al2O3. X-ray Diffraction analysis confirms the presence of oxides on the oxygen-machined surfaces, contributing to their hydrophilic nature. X-ray Photoelectron Spectroscopy analysis reveals broadened aluminium oxide peaks post-machining, shifting to higher binding energies, which reduces contact angles. Additionally, XPS survey data shows a higher C/Al atomic ratio of 4.87 in argon-machined samples, suggesting increased surface adsorption of organic compounds, resulting in greater hydrophobicity.