Corrosion-Fatigue of Ti-6Al-4V Coupons Manufactured by Directed Energy
Deposition
Abstract
Titanium is a versatile biocompatible metal that is desirable in
additively manufactured medical implant devices. However, additively
manufactured parts have particular microstructures, porosity, residual
stress and surface conditions which can have a strong impact on fatigue
performance. Implants have an added complexity from the saline operating
environment and the associated impact on the safe design life. Equally,
direct energy deposition induces a complex thermal history which, if not
carefully controlled, can significantly alter the mechanical/material
properties of the component. This study investigates the decrease in
fatigue life, in an in-vitro body fluid simulation using Ringer’s
solution, observed in Ti-6Al-4V specimens extracted from coupons
manufactured by directed energy deposition. An interrupted deposition
strategy was employed to control build regularity, which appeared to
influence certain mechanical properties, including corrosion fatigue
life. An ≈50% decrease in fatigue life was observed in Ringer’s
solution at 6 Hz loading frequency, clearly important in designing
implants.