TEM Investigation of the As-Quenched Compound Layer Formed by Austenitic Nitrocarburizing

The as-quenched compound layer of a 0.2% C steel formed by austenitic nitrocarburizing is found to be composed of single-phase ϵ-nitrocarbide with an hexagonal structure, as determined by electron diffraction. The difference in the site occupancy of nitrogen or carbon atoms may result in the formation of various types of ϵ-nitrocarbide; that is, ϵ-Fe2(N,C), ϵ-Fe2•3(N,C), and ϵ-Fe3(N,C). By a comparison of the intensities of the superlattice reflection spots observed in the electron diffraction patterns with those in computed simulation patterns, the phase in the compound layer of the as-quenched sample was identified as ϵ-Fe2•3(N, C).