Fatigue crack growth under corrosive environments of Ti-6Al-4V specimens produced by SLM

Additive manufactured parts made of Ti-6Al-4V alloy are increasingly used in medical devices and in the aeronautical industry, because of its high strength, low weight and excellent biocompatibility. Most of these components work under environmentally assisted cyclic loading, i.e. under corrosion-fatigue. Anisotropic microstructure of additive manufactured materials significantly influences the propagation of cracks, particularly under corrosion-fatigue. This paper presents the results of the failure mode and fatigue crack propagation study in titanium Ti-6Al-4V specimens produced by selective laser melting (SLM), under corrosive ambient. Three environment solutions were used: artificial saliva, Ringer's solution and 3.5%wt NaCl solution. Tests were performed using standard 6 mm thick compact specimens (CT) tested at R = 0.05 with frequencies of 1 and 10 Hz. The main objective was to study the effect of the corrosion potential on da/dN-Delta K curves and on the fatigue failure mechanisms. It was observed a very important accelerating effect on the crack initiation and fatigue crack propagation for tests under corrosion ambient, particularly for 3.5%wt NaCl solution, for which fatigue crack growth is 3.3 times higher in comparison with inert ambient tests.