Abstract

Aluminium is one of the most widely used materials across the world. Its elaboration process, based on the Hall-Héroult electrolysis process, has an energetic efficiency too low for such an important industry. In this research work, we worked upon the elaboration of wettable cathodes, meaning cathodes with a high molten aluminium wettability, in order to decrease the energetic cost of the process, as well as its environmental impact. These cathodes are based on a titanium diboride coating. In our studies, and for the very first time in history, these coatings were elaborated by suspension plasma spray.
High quality coatings with a very low degree of oxidation were produced by suspension plasma spraying coupled with a gas shroud to protect the in-flight particles from oxidation. Such an approach made it possible to significantly improve the deposited coatings as compared to the coatings from the literature deposited with atmospheric plasma spraying. Then, parametric studies led progressively to an increase in the percentage of molten particles, and, consecutively, an increase in the coatings’ density. This increased density came along with augmented thermomechanical strains, leading to fracture and delamination. A multilayer approach, as well as a refined control of the cooling of the samples after deposition, allowed for the mitigation of the stresses and led to dense un-oxidized coatings. These coatings have shown a very high aluminium wettability, better than the one of the cathodes currently in use today.