Microstructure characteristics of ZrO2 coating produced by atmospheric pressure chemical vapor deposition

To settle the problem of low growth rate when prepare ZrO2 thermal barrier coating by Metalorganic CVD (MOCVD), a simple method was employed-atmospheric pressure CVD (APCVD). The paper firstly thermodynamic calculated the effect of O/Zr ratio and temperature on phase formation at various H/C ratios for ZrCl4-CO2-H2-Ar system. With temperature increment, the solid phase changes from C+ monoclinic ZrO2 to Monoclinic ZrO2 then to tetragonal ZrO2. With the increase of H/C ratio, the phase zone of C+ monoclinic ZrO2 expands. XRD and Raman spectrum were employed to measure phase structure of ZrO2 coating at different temperature. At 1300 degrees C, the coating contains a small amount tetragonal ZrO2 phase besides monoclinic phase; at 1100 degrees C, the coating is composed of monoclinic ZrO2 phase and a little C. The surface SEM images show the small grains evolve to polycrystals which have clear crystal form when raising temperature. The cross-section images show that dense ZrO2 column crystals arrange normal to the substrate.