Study on flushing condition for improving silver deposition in silver nano-powder mixed EDM

Silver nano-powder mixed electrical discharge machining (PMEDM) has demonstrated its applicability for antibacterial surface modification. However, previous PMEDM studies indicated that jet flushing leads to a low powder concentration in the spark gap, which was the main reason for a low deposited silver content. Internal flushing with different dielectric pressures was therefore proposed and will be investigated in this study. To do so, Ti-6Al-4V hollow tool electrodes with an outer diameter of 3 mm and an inner diameter of 2.5 mm are selected to machine Ti-6Al-4V samples. Silver nano-powders with a size of 50 nm to 60 nm are suspended in the hydrocarbon-based dielectric fluid at a 5 g/l powder concentration. Surface roughness and resulting silver content and distribution on the modified surface are analysed and discussed. Results show that internal flushing significantly increases the deposited silver content when high pressure of the dielectric fluid was applied. In addition, with careful control, the internal flushing is a promising strategy for improving the uniformity of the deposited silver distribution.