Abstract: Under certain technological condition, the surface nitrogen concentration holds a certain value after Alternative Current Ion Nitrogen (ACIN) for half an hour, as nitriding time goes further. The kinetics of layer growth for each phase zone in nitrided layers obeys the parabolic law , and the mathematical formulas of the kinetic factor K are deduced. The function of the nitrogen concentration profile in the ACIN-ed layers are also deduced. The computer simulated nitrogen conentration profiles coincide with the experimental results well.

Key words: alternative current ion nitriding, kinetic factor, the function of the nitrogen concentration profile, computer simulation