Ultrasonic Vibration assisted Silver Integration by Powder Mixed EDM for Antibacterial Surfaces

Powder mixed electrical discharge machining (PMEDM) with silver nano-powder has demonstrated its potential capability in antibacterial surface modification. Analyses in the cross-sectional layer showed that silver was mainly integrated near the topmost surface layer, and its content is reduced within the layer towards the substrate. However, to achieve a long-term antibacterial efficacy, silver needs to be deeply integrated in the modified layer.

Previous studies indicated that ultrasonic vibration (UV) assisted PMEDM can homogenize the silver content in the deposited layer. In this study, the effect of UV on the silver distribution within the modified layer is investigated. Ti6Al4V workpieces were stimulated by UV with a frequency of 22.3 kHz and an amplitude of 2.5 µm. Hydrocarbon-based dielectric fluid, mixed with silver nano-powder with concentrations up to 15 g/L, were internally flushed through a hollow tool with a pressure of 4 bar. PMEDM without UV was investigated for comparison. The layer thickness, micro-cracks and the cross-sectional distribution of deposited silver were analysed by confocal microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Results indicate that applying UV leads to the highest silver content in the middle region of the layer, a significant decrease of micro-cracks and a slight reduction of the layer thickness.