Thermodynamics, kinetics and process control of nitriding

Eric J. Mittemeijer, Marcel A. J. Somers

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    As a prerequisite for predictability of properties obtained by a nitriding treatment of iron-based workpieces, the relation between the process parameters and the composition and structure of the surface layer produced must be known. At present (even) the description of thermodynamic equilibrium of pure iron-nitrogen phases has not been achieved fully. It has been shown that taking into account ordering of nitrogen in the epsilon and gamma' iron-nitride phases, leads to an improved understanding of the Fe-N phase diagram. Although thermodynamics indicate the state the system strives for, the nitriding result is determined largely by the kinetics of the process. The nitriding kinetics have been shown to be characterised by the occurring local near-equilibria and stationary states at surfaces and interfaces, and the diffusion coefficient of nitrogen in the various phases, for which new data have been presented. The necessary background has been given for process control of gaseous nitriding, by monitoring the partial pressure of oxygen in the furnace, utilising a solid state electrolyte.
    Original languageEnglish
    Title of host publicationProceedings of the tenth congress of the IFHT
    Place of PublicationLondon
    PublisherIOM Communications Ltd.
    Publication date1999
    Publication statusPublished - 1999
    EventThe tenth congress of the IFHT - Brighton, England
    Duration: 1 Jan 1996 → …


    ConferenceThe tenth congress of the IFHT
    CityBrighton, England
    Period01/01/1996 → …

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