Impact of Density on the Behavior of Suspension Plasma-Sprayed TiB2 Coatings in the Presence of Molten Aluminum

TiB2-coated graphite substrates are potential wettable cathodes for aluminum electrolysis. However, their properties must be improved to prevent the infiltration of molten aluminum into the coating, which can result in delamination of the coating. Here, a suspension plasma spray process was used to deposit TiB2 coatings (60-110 mu m thick) on graphite substrate. The coating's porosity can be controlled through the SPS deposition parameters, resulting in a porosity range between 4 and 25%. A double-layered TiB2 coating was also prepared, consisting of a denser top layer (4% porous, 40 mu m thick) and a porous bottom layer (19% porous, 65 mu m thick). No cracks were observed in the as-sprayed porous and double-layered coatings, in contrast to the denser single-layer (5% porosity) coating. Sessile Al drop tests were performed on TiB2 coatings to investigate their behavior in contact with molten aluminum. It was shown that the coating porosity impacts the spreading kinetics of Al drop, and all TiB2 coatings have a much better molten aluminum wettability than the graphite substrate. Moreover, after 8 h of contact with molten Al, no Al infiltration nor coating delamination was observed in the double-layered TiB2 coating, in contrast to single-layer coatings.

Automated summary

TiB2-coated graphite substrates have the potential to be wettable cathodes for aluminum electrolysis. The properties of the coatings can be improved, and a double-layered coating shows better performance in contact with molten aluminum.