Factors governing slurry aluminization of steels

Slurry aluminization has been used for a long time. This work presents the study of several important parameters affecting the formation of aluminum diffusion coatings onto iron base alloys via slurry application. The study concentrates on the formation mechanism of aluminides using the coating surface coverage and the coating thickness of different steels as evaluation method. Steel composition, heat treatment atmosphere, and steel surface finishes were the studied parameters. These three parameters have to be in accordance in order to obtain aluminum in the melted phase, avoid excessive substrate oxidation, promote fast diffusion of elements forming aluminides, and avoid diffusion of elements blocking the exothermic reaction that forms aluminides during the heat treatment.