Papers by Keyword: Iron Nitrides

Abstract: The 32CrMoV13 low alloy steel was gas nitrided at 550°C, for three time durations (6.5, 13 and 20 h) and under a variable nitriding potential (1, 2.2 and 6 atm-0.5). The generated nitride layers were characterized by SEM observations, XRD and GDOS analyses as well as microhardness testing. The XRD analysis indicates that the compound layer was composed of and iron nitrides and CrN phase. The surface hardness (inside the compound layer) was found to be dependent on the nitriding potential value, its value increases as rises. It was shown by GDOS analysis that the upper and lower nitrogen concentrations at the (compound layer / diffusion zone) interface are approximatively: 4 and 0.88 wt. % N, respectively.

Abstract: α-Iron foils were exposed to various gas atmospheres containing all or a number of the components NH3, CO, H2 and N2 for different periods of time at 550°C. In this way surficial compound layers were generated which contain different iron nitrides (ε, γ’), iron carbonitride (ε) and/or iron carbide (cementite, Fe3C). These compound layers were used to study phase transformations associated with N- and/or Cdiffusion processes in the corresponding phases. These studies involved (a) the layer-growth kinetics of cementite and (b) various solid-state phase transformations occurring in compound layers upon annealing in vacuum.

Abstract: ε/γ'-iron nitride (ε-Fe3N1+x, γ'-Fe4N) compound layers with thicknesses of about 10 µm were grown on pure α-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 ε- and γ'-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 ε/γ'-iron nitride compound layers as a function of time and temperature are discussed.