Experiments and modeling study on growth behavior of Cr-nitrides formed on electroplated hard Cr during ion-nitriding

The structure and composition of Cr-nitrides formed on an electroplated hard Cr layer during an ion-nitriding process were analyzed, and its growth kinetics was examined as a function of the ion-nitriding temperature and time to establish a computer simulation model for the prediction of growth behavior of the Cr-nitride layer. The Cr-nitrides formed during the ion-nitriding at 550–770 °C were composed of outer CrN and inner Cr₂N layers. A nitrogen diffusion model in the multilayer, based on fixed-grid finite difference method, was applied to simulate the growth kinetics of Cr-nitride layers. By measuring the thickness of Cr-nitride layers as a function of ion-nitriding temperature and time, the activation energy (Q) and nitrogen diffusion constant (D_o) were determined for growth of CrN and Cr₂N; the result was applied to simulate the growth kinetics of Cr-nitride layers, and reasonable good agreement was obtained with the experimental results.