Modeling the kinetics of the nitriding and nitrocarburizing of iron

Marcel A. J. Somers, Eric J. Mittemeijer

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    The growth kinetics of the iron-nitride compound layer during nitriding and nitrocarburizing of pure iron has been investigated for various temperatures and various combinations of imposed nitrogen and carbon activities. The results indicate that no local equilibrium occurs at the gas/solid interface during nitriding/nitrocarburizing, due to the slow kinetics of ammonia dissociation, the development and subsequent desorption of molecular nitrogen gas at the surface and, for the case of nitrocarburizing, the fast initial carbon uptake. The kinetics of gaseous nitriding of pure iron can be adequately described by a model that adopts local equilibrium at the solid/solid interfaces and a composition-weighted intrinsic diffusion coefficient of nitrogen in the Fe-N phases. For nitrocarburizing modeling appears not possible yet, due to compositions at gas/solid and solid/solid interfaces which change with treatment time and the lack of accurate thermodynamic and kinetic data for Fe-N-C phases.
    Original languageEnglish
    Title of host publication17th Heat Treating Society Conference Proceedings
    Place of PublicationMetals Park
    PublisherASM International
    Publication date1998
    Publication statusPublished - 1998
    EventASM heat treating society conference - Indianapolis
    Duration: 1 Jan 1997 → …


    ConferenceASM heat treating society conference
    Period01/01/1997 → …

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