An investigation of oxidation, hot corrosion , and thermal shock behavior of atmospheric plasma-sprayed YSZ-Al2O3 composite thermal barrier coatings

Abstract

In the current study, different types of thermal barrier coatings with various mass fractions were investigated in terms of oxidation, hot corrosion, and thermal shock resistance. The thermal barrier coatings consisted of six different samples, which included the usual YSZ, Al2O3, hybrid composites with 65 wt.% YSZ and 35 wt.% Al2O3, 50 wt.% YSZ and 50 wt.% Al2O3, 35 wt.% YSZ and 65 wt.% Al2O3 and the final one, which was a double layer composite (Al2O3 and YSZ). High temperature isothermal oxidation behavior of the coatings was tested at 1050 degrees C, using an air furnace for 48 h. 80 h. and 120 h respectively. Hot corrosion tests were applied at 1050 degrees C using a 45 wt.% Na2SO4 and 55 wt.% V2O5 mixture of salts. The microstructure and phase stability of coatings were evaluated by means of scanning electron microscopy and X-ray diffraction techniques. The usual YSZ showed better hot corrosion and thermal shock resistance, while Al(2)O(3 )showed the lowest hot corrosion and oxidation resistance. Thermally grown oxide formation, thermal expansion coefficient mismatch and phase transformation in the thermal barrier coatings could be the main causes of degradation after thermal shock testing.