The improved process of austenitic nitriding by applying the controlled nitrogen potential theory could achieve high nitrogen austenite samples without a descend nitrogen profile from the surface to the center. The key of this nitriding process is that the pure iron foil can be thoroughly nitrided to high-N austenite which is thermally stable at room temperature by adjusting the nitrogen potential within the temperature range of 640oC-645oC. The nitrogen concentration of the austenite was determined ...