Formation of thermal barrier coatings using Zr-Y salt pyrolysis in Ar-He-H2 plasma
An experimental set-up has been designed and manufactured. Samples with heat protective ceramic coating have been obtained at the set-up by injecting in Ar-He-H2 plasma ZrO <sub>2</sub>-Y <sub>2</sub>O <sub>3</sub> precursor. Spray coating modes have been established. The results of thermal-cycle testing in 100°C-1150°C(15 min)-100°C cycle mode showed the advantage of the obtained coatings over the traditional plasma one by 40%. The authors assume that ZrO <sub>2</sub>-Y <sub>2</sub>O <sub>3</sub> precursor alloying with rare earth metal oxides will increase the operating temperature of the coating. The injection of ZrO <sub>2</sub> — 7%Y <sub>2</sub>O <sub>3</sub> precursor in plasma was performed with air atomizing burner. During spray coating, the surface temperature of the samples did not exceed 700-750°C. The characteristic surface texture of the thermal barrier coating is shown in Fig.4. The study of the coating microstructure by means of JEOL JSM6510LV electron microscope showed existence of ZrO2+7%Y2O spherical particles, particles with full and partial penetration, fusion and cross-sectional microcracks. Prior to TBC formation the samples were covered with PKH-27YU7SZI (ПКХ-27Ю7С3И) 170 μm metal heat-proof layer using a traditional plasma method. Thermal-diffusion vacuum annealing at a temperature of 1050°C was executed during 4 hours.