Abstract
Super alloys are high-performing alloys used in gas turbine components that are exposed to high temperatures and pressures. When alloys are exposed to temperatures beyond the operating limit of turbines, the material fails. To avoid such a failure, a thermal barrier coating is provided on the substrate. In this work, a single-layer coating of CeO₂ doped with YSZ in the proportion of 1:3 percentage is applied on Inconel X750 using the air plasma spray technique. Additionally, a double-layer coating of CSZ as the first layer and, Al₂O₃-TiO₂ as the second layer in the proportion of 3:2, is applied on another Inconel sample by the same process. The presence of bond coat and ceramic top coat on the substrate are confirmed by the SEM images. It is perceived from the investigations that, the porosity of the single CSZ layer is more compared to that of the double-layer (CSZ-Al₂O₃-TiO₂) coating. The XRD analysis of the CSZ sample shows the phase transformation of monoclinic to tetragonal ZrO₂ and that of double-layer coating (CSZ-Al₂O₃-TiO₂) shows the transformation of alumina. Raman spectroscopy is done to ascertain the states of various oxides present in the coatings. The double-layer coating exhibits more hardness when compared to the single - layer coating. The hot corrosion test is carried out for 50 hours for both single and double-layer coating in the medium of the mixture containing 25% NaCl and 75% Na₂SO₄ solution. The change in mass per unit area of the CSZ single layer coated sample is more compared to that of CSZ-Al₂O₃-TiO₂ double layer coating.

Key words
Thermal Barrier Coatings (TBC), ceria doped YSZ, alumina, titania, hot corrosion, air plasma spraying

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