Oxygen depth profiling by resonant backscattering and glow discharge optical emission spectroscopy of Ti-6Al-4V alloy oxidized by ion implantation and plasma based treatment

The obtained results show that the oxygen content into the surface oxidized layer slightly increases in samples implanted at higher fluence and higher temperature. However the overall oxidized layer thickness (<200 nm) remains within the projected ion depth range and is not significantly increased by thermal diffusion at 550 °C. Taken into account the initial oxide layer, the incorporated oxygen quantity mainly corresponds to the implanted fluence but it can be slightly higher with 550 °C implantation, indicating a slight additional oxidation by residual oxygen or surface contamination. The oxygen penetrations and contents in samples oxidized by thermally activated diffusion treatments were more pronounced compared to implanted samples, especially with plasma assistance. A highly oxidized layer (>50 at.%) of about 100 nm was obtained after 7 h of treatment. X-ray diffraction revealed the presence of rutile TiO2 phase only after a long duration (24 h) thermally assisted treatment whereas oxygen incorporation mainly results in a c-axis expanded hexagonal titanium phase in all the other samples.