Stress Induced Concentration Dependent Nitrogen Diffusion In Plasma Nitrided Cocr Alloys

The nitrogen depth profiles obtained from plasma nitrided CoCr alloy are analyzed by the stress induced diffusion model. The model considers diffusion of nitrogen under the influence of internal stresses created during nitriding process. Besides, this model is supplemented with concentration dependent nitrogen diffusivity. The calculations were done using experimental nitrogen depth profiles for plasma nitrided medical grade CoCr (ISO 5831 - 12) alloy at 400 degrees C and different nitriding durations. Fitting results are in good agreement with experimental curves. The diffusion coefficients D were found from fitting of experimental data.