Moessbauer surface analysis of nitrogen ion implanted austenitic and ferritic steels

This work aims to examine the effects of ion energy and current density during nitrogen implantation of steel. The microstructure and the nitrogen distribution at the surface of austenitic and ferritic steels were compared and discussed. The surface of the austenitic X2CrNiMo17-13-2 and ferritic X1CrNiMoNb28-4-2 steel was nitrided by N+ ions implantation at doses of 0.3-10 x 1017 N+cm-2, with an energy of 60 or 100 keV. The beam current density is 1.5 - 3.5 μAvcm-2. X ray diffraction (XRD), conversion electron Moessbauer spectroscopy (CEMS) were used to investigate the nitride phases resulting from the nitrogen implantation. The formation of Cr2N, α'-martensite, γR-N enriched austenite, Fe4N γ'-like structure, h.c.p. ε and metastable f.c.c. phases is also detected depending on steel grade and nitriding conditions. Evolution of the phase formation is associated with chromium and nitrogen migration and segregation during the nitriding process. (orig.)