The behavior of ZrO2/20%Y2O3 and Al2O3 coatings deposited on aluminum alloys at high temperature regime

Aluminum alloy present numerous advantages like lightness, high specific strength and diversity which recommend them to a high number of applications from different fields. In extreme environments the protection of aluminum alloys is difficult and requires a high number of requirements like high temperature resistance, thermal fatigue resistance, corrosion fatigue resistance and galvanic corrosion resistance. To obtain these characteristics coatings can be applied to the surfaces so they can enhance the mechanical and chemical properties of the parts. In this paper two coatings were considered for deposition on an AA2024 aluminum alloy, ZrO2/20%Y2O3 and Al2O3. To obtain a better adherence of the coating to the base material an additional bond layer of NiCr is used. Both the coatings and bond layer were deposited by atmospheric plasma spraying on the samples. The samples were subjected to a temperature of 500 °C and after that slowly cooled to room temperature. The samples were analyzed by electron microscopy and X-ray diffraction to determine the morphological and phase changes that occurred during the temperature exposure. To determine the stress level in the parts due to thermal expansion a finite element analysis was performed in the same conditions as the tests.