Powder mixed electrical discharge machining for antibacterial coating on titanium implant surfaces

Infection in medical implantation requires a long and often costly treatment procedure which affects patient's psychology and causes death in many cases. Some methods such as ion implantation, physical vapor deposition and magnetron sputtering have demonstrated their efficiency in antibacterial coating. However, these are purely coating methods and until now, there is no method that has the ability to concurrently machine and coat an antibacterial layer on the surface of medical implants. Powder mixed electrical discharge machining (PMEDM) is therefore proposed and investigated in this study since it's a machining method with precise surface modification potential. This includes the transfer of tool electrode material as well as powder material suspended in the dielectric fluid to the workpiece. Preliminary research findings have shown that varying silver content (from 0.2% to 1.12%), depending on powder concentration suspended in the dielectric fluid, can be transferred to the modified layer. In this study, different silver nano-powder concentrations are added to a hydrocarbon-based dielectric fluid and used to machine titanium workpieces. Surface roughness, material removal rate, tool wear, pulse signals, recast layer, micro crack and resulting silver content on the workpiece are analyzed and discussed. Results show that powder concentration plays a vital role in regulating the amount of silver deposited on the machined surface. Since this directly affects the effectiveness of the coated antibacterial layer, it can therefore be shown that, with careful control, PMEDM is a promising method for concurrent machining and coating an antibacterial layer on the surface.