Preparation of Al2O3–YSZ composite coating by EB-PVD

An Al2O3–YSZ thermal barrier coating was prepared by co-deposition of Al2O3 and YSZ (8 wt.% Yttria Stabilized Zirconia) onto NiCoCrAlY bond coat by means of electron beam physical vapor deposition (EB-PVD). Analysis of SEM/EDXS showed that the structure and composition distribution across the thickness of the coating changed continuously. Simultaneously, a gradient micro-porous microstructure formed in the coating, which resulted in micro-hardness of the coating increasing gradually towards its surface. Additionally, the Al2O3–YSZ coating exhibited a lower thermal conductivity than traditional YSZ coating, which was caused by the micro-porous microstructure in the coating and the vacancies appearing in the ZrO2 lattice.