Abstract
This paper presents a physical model which describes the layer growth kinetics and the nitrogen concentration profiles during gaseous or plasma nitriding of pure iron. The model is related to a one dimensional moving boundary value problem where the initial concentration profiles are assumed to be linear and a new boundary condition at the diffusion zone is proposed. The model is solved by using a classical finite difference scheme (FDM-CS) and the Heat Balance Integral Method (HBIM). Due to the proposed boundary condition at the diffusion zone, the numerical solutions can be validated through a simple physical analysis of mass transport theory in the asymptotic time limit. The results obtained are compared, and observed to be in good agreement with available experimental data and other approximate solutions reported in the literature. Key words: Advanced characterization, coatings, plasma nitriding, finite difference, heat balance.
Highlights
A basic framework for modeling the physical processes during nitriding is provided by moving boundary diffusion problems
This paper presents a physical model which describes the layer growth kinetics and the nitrogen concentration profiles during gaseous or plasma nitriding of pure iron
The kinetics of layer growth in pure iron is obtained by a simple diffusion model that assumes a diffusion zone of constant thickness
Summary
A basic framework for modeling the physical processes during nitriding is provided by moving boundary diffusion problems. From a practical point of view, in order to get a good control of the process during the growth of concomitant layers, it is desirable to have a good estimate of the compact nitrided layers evolution. The study and solution of such models have been performed mainly by using error function approaches, HBIM, finite difference, and finite element methods. Each of these supply acceptable results for large values of time under
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