epsilonFe3N

Epsilon-Fe3N, often written as ε-Fe3N, is an iron nitride compound with the approximate composition Fe3N. It is one of several nitride phases that can form in iron when it is exposed to nitrogen under controlled conditions. The epsilon phase is typically metastable and is commonly observed in nitrided iron and steel as a surface nitride layer or within the diffusion zone.

Crystal structure and chemistry are characteristic of ε-Fe3N by a hexagonal arrangement in which nitrogen atoms occupy interstitial sites within an iron lattice. This structure and its specific stoichiometry distinguish it from other iron nitrides such as Fe4N and Fe2N, which can appear under different nitriding conditions.

Formation and stability are governed by nitrogen activity, temperature, and processing environment. ε-Fe3N forms under moderate nitriding conditions and can appear during gas nitriding or plasma nitriding. Its stability is typically limited to certain temperature ranges and nitrogen activities; with further changes in conditions, ε-Fe3N can transform into other nitride phases such as Fe4N or Fe2N, or to ferritic iron with dissolved nitrogen.

Properties of ε-Fe3N include ferromagnetism and increased hardness relative to pure iron, contributing to improved surface wear resistance when present as a nitride layer. The phase is primarily of interest in materials science and engineering for understanding nitriding kinetics, diffusion processes, and the development of hard, magnetic surface coatings.

Applications and research focus on ε-Fe3N center on coatings and diffusion-barrier materials in nitrided steels, as well as fundamental studies of phase relationships within the iron-nitrogen system. See also iron nitrides, nitriding, and the Fe–N phase diagram.