Effect of nitrogen implantation on the hydrogen depth distribution and fatigue properties of Ti6Al4V

Depth distributions and fatigue of nitrogen-implanted Ti6Al4V alloy were investigated using backscattering spectrometry, nuclear reaction analysis and rotating bending tests. A hydrogen accumulation (up to 2.6 at.%) occurs in the region enriched in nitrogen. High hydrogen concentrations occur when a mixture of titanium nitride (TiN) and α-titanium is formed; the concentration decreases below 1.5 at.% when a continuous TiN layer is formed. Nitrogen implantation does not reduce fatigue life. Fatigue cracks preferentially form in regions where the enrichment of nitrogen and hydrogen is close to the surface.