ROLE OF ALLOYING ELEMENTS IN THE STABILITY OF NITRIDES IN NITROGEN-IMPLANTED ALPHA-FE

The role of alloying elements, such as Cr, Al, Ti, and Mn, in the formation and stability of the nitride phases formed due to nitrogen ion implantation into metallic α-iron was studied by conversion electron Mössbauer spectroscopy. The thermal stability of the nitride phases of α-Fe implanted with N was greatly increased by coimplanting with N the alloying elements. For instance, the stability of α'-martensite at low N-dose implantation is strongly enhanced and also that of γ'-Fe4N at high N dose. Titanium stabilizes the ε-Fe3-xN-type nitride preventing the formation of the γ' phase. The presence of alloying elements influences the thermal stability of nitrides by increasing their binding energy and thus preventing the dissociation of nitrogen and also by forming traps that lead to the formation of TiN, AlN, or CrN nitrides. The thermal stability of nitrides, especially of ε-Fe3-xN and γ'-Fe4N ones, is improved in decreasing order by the presence of Ti, Al, Cr, and Mn. © 1995 American Institute of Physics.