Fig. 8(a and b) illustrate the SEM micrographs of the top surface
of the conventional YSZ and the laser clad coating, respectively, after the hot corrosion test. As seen, after 30 h of hot corrosion test, rod-type crystals have formed on the conventional YSZ coating. The EDS analysis (Fig. 8-c) proves that this elongated phase is rich in yttrium and therefore is formed as a result of the reaction of yttria with the molten salt at elevated temperature, showing poor resistance of the YSZ coating. In contrast, these elongated features are scarce on the surface of the laser clad coating (Fig. 8-b), proving significant improvement of the hot corrosion resistance of the TBCs after laser cladding of alumina on the surface of YSZ as a result of the formation a dense impermeable layer on the top surface of the YSZ coating. The elimination of the imperfections such as voids and cracks after laser cladding, reduces the penetration paths of molten salts into the YSZ layer. The smooth layer of the TBCs after laser cladding (having lower roughness) also decreases the effective contact surface between the YSZ and the molten corrosive salts. The fact that no