Corrosion Behavior of Laser Melted Alumina-40 wt% Titania Coated High Density Graphite in Molten Salt

Plasma sprayed alumina-40 wt% titania (A40T) coatings deposited on high density graphite were laser melted and immersed in molten LiCl-KCl salt for 24 h at 873 K to compare the corrosion behavior of the coatings before and after laser surface treatment. The as-sprayed and laser melted coatings after exposure to molten salt were characterized to evaluate their microstructure and phase composition. Uniform microstructure and homogeneous surface generated by laser melting process facilitated enhanced protection of the A40T coatings from molten salt attack. Absence of phase change in the coating after corrosion test, implied that no reaction occurred between the molten salt and coating. While keeping other beam parameters constant, increasing the laser average power from 6.4 to 8 W had not only resulted in improving the surface quality and the corrosion resistance of A40T coating, but also reduced the penetration and settling of molten salt on the coating.