Gefuge und Eigenschaften - Modellierung der Keimbildungs- und Wachstumskinetik der Verbindungsschicht beim Nitrieren von Reineisen

Nucleation and the growth rate of the compound layer during gaseous nitriding are to a high degree governed by the kinetic phenomena at the surface. The competition between nitrogen arrival at and nitrogen departure from the surface establish a dynamic state. In the present article the incubation time for the nucleation of gamma’-Fe4N1-x at the surface of pure iron is calculated from literature data and compared to experimental results.

The influence of an oxide layer on nitride nucleation was experimentally investigated. On the basis of the results obtained a hypothesis was put forward to explain the accellerating effect of an oxidizing pretreatment on the nucleation on iron nitrides. A model was developed for describing growth of a double layer, which consists of epsilon-Fe2N1-z at the surface und gamma’-Fe4N1-x at the substrate.

The model takes the dynamic state at the surface into account, and was fitted to experimental data for double layer growth.