Pages 389-390
Metallic materials are widely used for orthopedic implants like artificial hip joints that bear high loads throughout its use. However, they are not capable of bonding directly to living bone. This problem will be solved if the metallic material forms hydroxyapatite (HAp) on its surface enabling living bone to bond to the metal. In this study we tried to evaluate fatigue crack propagation properties of bone-induced Ti-6Al-4V alloys in simulated body fluid (SBF), which simulates the human blood plasma in terms of ion concentrations. Bone-inducing function was added on Ti-6Al-4V alloys by coating HAp through surface treatment The fatigue crack propagation test of bone-induced Ti-6Al-4V alloys was performed under a SBF environment at 37℃. The result of the fatigue test is analyzed in terms of the fatigue crack extension rate (da/dN) vs. the stress intensity factor plots (⊿k). At stable crack propagation filed in the da/dN- ⊿k curve, the crack propagation rates of the HAp coated Ti-6Al-4V alloys and alkali-heat treatment Ti-6Al-4V alloys specimens were higher than the Ti-6Al-4V alloys without the coating. This difference is possibly caused by the stress corrosion cracking (SCC). The SEM observations of fatigue fracture surface during stable crack extension showed the evidence of SCC that occurs during fatigue crack extension in SBF environment that is observe in the coated Ti-6Al-4V and Alkali-Heat Treatment Ti-6Al-4V alloys specimens.
