Migration studies of nitrogen implanted iron by improved depth profiling

It has been established that the implantation of nitrogen ions into steel can improve the tribological properties of the metal. The mechanism responsible for these improvements is not well understood. In many cases, properties such as wear, corrosion and friction were improved to a depth greater than the range of the implanted ions.

In an attempt to elucidate the mechanism of the nitrogen ion diffusion under thermal treatment, pure iron foils were implanted at 50 keV with fluences ranging between 1016 and 2 × 1017 N+ cm−2 with enriched nitrogen (70% 14N plus 30% 15N). The depth profiling of 15N and 14N is performed on the same sample using the 15N(p, αγ) reaction at Ep = 429 keV and the 14N(α,γ) reaction at Eα = 1531 keV.

Initial results indicate a well-resolved two-component distribution in the species implanted. Profiling 15N using the 429 keV resonance does not resolve this structure because of the poor depth resolution, but with the 14N(α,β) reaction it is possible to observe the migration kinetics of each component vs. the temperature of implantation and vs. the fluence of the nitrogen ions implanted.