Numerical treatment of the plasma carburising process

The purpose of this article is to present a simple model for describing the carbon transport phenomena during the boost period of plasma carburising process. In that sense, the following interconnected subprocesses are considered: steady state diffusion with concentration source/sink in surrounding plasma and unsteady state diffusion in steel surface layer. The concept of steady state diffusion with source/sink is used to substitute the net deviation of plasma carbon concentration in surrounding plasma as well as to determine the surface carbon content. The model employs a finite difference scheme to solve the governing partial differential equation (the Fick's second law) to predict the carbon profile in the surface layer of a steel. The procedure has to be based on a correction of the carbon diffusion coefficient according to the actual carbon concentration and temperature in the diffusion layer.