Hot Corrosion Behavior of a Novel Enamel-Based Thermal Barrier Coating

A novel thermal barrier coating comprised two layers: sputtered bond coat and enamel-zirconia composite top layer. The hot corrosion tests were carried out at 900 °C for 100 h. The salt used in the tests was 25wt% NaCl + 75wt% Na2SO4. Mass loss and spalltion of oxide scales of uncoated K444 specimens was obvious. For the coated specimens, no oxide scale spallation and no weight loss were observed. The TGO formed on the coated specimens was thin layer of mixture oxides of Al, Ti and Cr, while thick multi-layered oxide scales formed on the uncoated specimens. Besides, deep internal oxidation zone was observed on the uncoated specimens. The coatings after hot corrosion tests contained t-ZrO2 and NaAlSi3O8, while the oxide scales formed on the uncoated K444 were TiO2, Cr2O3, NiCr2O4 and Na2Cr2Ti6O16.