Potential of Powder Mixed Electric Discharge Machining to Enhance the Wear and Tribological Performance of β-Ti Implant for Orthopedic Applications

In this research work, a new innovative technology called powder mixed electric discharge machining (PMEDM) was explored as new approach for surface modification of β-Ti implant in order to enhance its surface properties. The surface modification has been carried out by material migration/alloying from suspended silicon powder particles in dielectric fluid of electric discharge machining (EDM). The surface topography and phase composition of the un-machined and machined (PMEDMed) surfaces has been investigated using field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. The micro-hardness of the un-machined and PMEDMed surfaces has been measured on a Vickers hardness tester. The friction and wear properties of the surfaces have been evaluated via pin-on-disc tribometer. The results reviled that the application of PMEDM not only altered the surface topography, but also imparted the surface chemistry with oxides and carbides. The microhardness of PMEDMed surface has been increased by 2-fold than that of the base material (β-Ti alloy), primarily because of the formation of the hard carbide phases on the machined layer. The tribological analysis has revealed that the modified layer has excellent friction-reducing and better wear resistance than un-machined β-Ti specimens. This results have been attributed to the formation of TiC, NbC and SiC like carbides on the machined surface. The wear mechanism of the self-lubricating coating was fatigue wear and abrasive wear.