YSZ–Al2O3 thermal barrier nanocomposites coatings: Electrophoretic deposition and characterization

Abstract

AbstractThis paper presents the development of yttria‐stabilized zirconia–alumina (YSZ–Al2O3) nanocomposite coatings deposited on Inconel 738LC superalloy substrates using the electrophoretic deposition technique. To prepare stable suspensions of YSZ and Al2O3 nanoparticles, a mixture of 75 mL acetone and 25 mL ethanol was used as a medium with .4 g/L iodine as a dispersant. The effects of Al2O3 concentration on suspension stability, electrical conductivity, and pH were studied in detail to optimize the suspension chemistry. The deposition kinetics were systematically investigated as a function of suspension concentration, deposition voltage, deposition time, and iodine concentration () to optimize the process parameters. The as‐dried coatings deposited at Vd = 10 V for 90 s were uniform, crack‐free, and sintered at 1150°C for 4 h. The microstructure, phase composition, hardness, and adhesion strength of the coatings were analyzed using scanning electron microscopy, X‐ray diffraction, Vickers microhardness measurements, and conducting shear loading tests, respectively. The results showed that adding Al2O3 to YSZ reduces porosity, crack density, and sintering temperature while stabilizing the tetragonal phase and retarding the martensitic transformation and crack formation. Among the studied coatings, the YSZ–20 wt.% Al2O3 nanocomposite coating deposited at Vd = 10 V for 90 s exhibited the most improved microstructural features, hardness, and adhesion strength.