Étude de la diffusion dans un système multiphasé appliqué à l'aluminisation du fer et des aciers

Abstract

Diffusion coatings of aluminium on iron and steels were obtained by an aluminization pack-cementation process, principally at 900 °C. A mathematical analysis of diffusion during aluminization allows the calculation of the concentration profiles in the coatings and of the incorporation rates of aluminium to be made. Analytical solutions are employed for the one-, two- and three-phase, semi-infinite planar diffusion problem. The theoretical and experimental results on pure iron are in good agreement; the theoretical predictions can be extended to 13% and 17% Cr steels, to a first approximation. On 24% Cr steel the diffusion rate is very low and the coatings obtained on austenitic stainless steel exhibit a diffusion barrier of nickel.

The aluminium surface concentration, the incorporation rate and concentration profiles can be controlled by changing the aluminium activity in the pack.