Effect of TiO2 content on the thermal control properties of Al2O3-xTiO2 composite coatings prepared by supersonic plasma spraying technology

Abstract

The main challenge faced by spacecraft is the large temperature difference in its operating environment. Thermal control coatings prepared on spacecraft and instrument surfaces are currently the most efficient ways for heat dissipation and control. In this work, Al2O3-xTiO2 composite coatings with different TiO2 contents were prepared on 7075-Al alloy substrate by supersonic plasma spraying technology. The microstructure, phase composition, mechanical properties, thermal control properties, and corrosion resistances of the coatings were investigated. The raw stock feeds were mainly composed of α-Al2O3 and anatase TiO2, but the coatings were mainly γ-Al2O3 and rutile TiO2. The average Vickers microhardness of the coatings decreased from 1198.9 to 810.4 HV0.2 with the increase of TiO2 contents, but the elastic modulus increased from 158.5 to 244.3 GPa. The thermal control properties of the coatings were promoted with the growth of TiO2 contents, and the absorptance increased from 27.1 to 89.2% with the emittance from 83.7 to 86.5%. The corrosion potential and corrosion resistance of the coating gradually increased with TiO2 content due to its gradually improved hydrophobicity. This work broadens the application boundary of Al2O3-xTiO2 composite coating and provides an innovative idea for material selection of thermal control coatings.

Keywords

• Al2O3-xTiO2 composite coating
• Supersonic plasma spraying
• Mechanical properties
• Absorptance
• Emittance