Influences of Laser Remelting on Hot Corrosion Resistance of Plasma-sprayed Nanostructured Al₂O₃-13wt.%TiO² Coating

Abstract

Nanostructured Al2O3-13wt.%TiO2 ceramic coatings were prepared on the TiAl alloy surface by using the plasma spraying and plasma spraying-laser remelting composite technology, respectively. Hot corrosion behaviors of these two coatings in 75%Na2SO4+25%NaCl (mass fraction) fused salts under 850 °C were discussed. Moreover, phases and microstructures of specimens after the corrosion were analyzed by X-ray diffractometer (XRD) and scanning electro microscope (SEM). Effects of laser remelting on hot corrosion resistance of coatings were explored. Results demonstrated that hot corrosion of ceramic coating prepared by plasma spraying is serious, but the hot corrosion resistance can be improved effectively after laser remelting. Laser remelting specimens show the higher hot corrosion resistance for two reasons. On the one hand, laser remelting forms a uniform and dense remelting layer by eliminating the lamellar structures and most pores of the coating layer, thus decreasing the corrosion diffusion channels during hot corrosion. On the other hand, laser remelting changes the metastable-phase γ-Al2O3 into stable-phaseα-Al2O3.