We studied, in steady and in unsteady state, the gas-solid reaction of gas nitriding
(NH3-H2) of steel, in order to control the atomic nitrogen
transfer in α-iron as a function of the inlet flow rates. We obtained the simultaneous
simulation of the gas phase variations, and the nitrogen transfer in the sample. The
evolution of the nitrogen concentration at the surface and inside of the α-iron, as a
function of the time, is presented. The results are in good agreement with the experiment
and with previous work. We also established a correlation between the gas composition
around the sample and the inlet conditions, in order to obtain an optimal nitrogen
transfer at the sample’s surface, and thus control the nitride layer growth.