Cr ion impantation into Ti: Part II. Cr diffusivity

High fluence chromium ion implantations were used in the attempt to improve titanium surface properties. Depending on the particular type of property, this can be achieved either by forming Ti–Cr intermetallic compounds or simply by promoting different Ti–Cr solid solutions in the surface region of Ti. Annealings at elevated temperatures were performed in implanted samples leading to a loss of Cr from the implanted region as seen by Rutherford Backscattering Spectrometry (RBS). In these situations, standard RBS spectrometry is totally unable to yield a depth profile and thus to answer the question whether Cr was lost from Ti or diffused inwards at a fast pace. A proton microbeam was used to perform cross-sectional analysis and to successfully extract Cr profiles down to depths that extend far beyond the reach of standard RBS with MeV He+ beams. It allowed to prove that, rather than being lost through the surface, chromium diffused inwards at a very high rate. Diffusion coefficients and an activation energy for Cr diffusion in Cr-implanted Ti were derived from the experimental data.