Evaluation of Ti-6Al-7Nb femoral stem fabricated by centrifugal investment casting using fatigue test

Abstract

Ti-6Al-7Nb is widely used for medical implant application due to its excellent biocompatibility, good corrosion resistance and low density. Another essential feature that needs to be demonstrated from materials for this application is its endurance to withstand the cyclic load for certain period of time. In this paper, the fatigue properties of Ti-6Al-7Nb used in femoral stem component were investigated corresponding to ISO 7206:4 standard. The femoral stem was fabricated by centrifugal investment casting and then subjected on to fatigue test. The result shows that the femoral stem ruptured at 5.2 x 105 cycle, below ISO 7206:4 requirement of 5 x 106 cycles. It was examined with non-destructive test using gamma radiation prior to the fatigue test. The fracture surface was also studied with Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX). There were found several casting defects such as shrinkage porosities and inclusion that presumably led to early failure. It can be assumed that the casting defects significantly affect the fatigue properties of Ti-6Al-7Nb femoral stem.