Mathematical simulation of the layer growth kinetics during post-discharge nitriding: From early stage to quasi-steady stage

Nitriding by microwave post-discharge process involves molecular nitrogen dissociation. It has been observed that nitrogen flux from surface to solid during the early stage does not follow a parabolic regime and that the growth rate of concomitant nitride layers is sensitive to atomic nitrogen concentration on the surface. s work a mathematical model has been developed in order to describe the kinetics of the compound layer formation during a post-discharge nitriding process. The model is related to a moving boundary value problem and considers different stages: diffusion process, formation of the layers, layer growth and quasi-stabilization of the layer growth. An analytical approximate solution of Goodmanʹs type is sought and representations of the motion of the interfaces and the nitrogen concentration profiles are analyzed.