Phase transformations in ε-/γ'-iron nitride compound layers in the temperature range of 613 K-693K

epsilon/gamma'-iron nitride (epsilon-Fe(3)N(1+x), gamma'-Fe(4)N) compound layers with thicknesses of about 10 gm were grown on pure alpha-Fe by gas nitriding at 823 K followed by quenching and were annealed at different temperatures in the range of 613 K - 693 K for different periods of time. These heat treatments led to a redistribution of nitrogen within the compound layer as well as between the compound layer and the adjacent ferrite, inducing thickness changes of the epsilon- and gamma'-layers. The changes were analysed by light microscopy, electron probe microanalysis and X-ray diffraction. Models to describe and interpret the phase transformations in the epsilon/gamma'-iron nitride compound layers as a function of time and temperature are discussed.