Microstructure and High Temperature Wear of the Thermal Barrier Coatings on TiAl Alloys

Al-diffusion/YSZ thermal barrier coatings (TBCs) were deposited on the TiAl alloy by electronic beam-physical vapor deposition (EB-PVD). The microstructure, chemical composition and phase constituent of the TBCs were analyzed by SEM, EDX and XRD. The microhardness and high temperature friction and wear behavior of the TBCs were measured. The results showed that the top YSZ coatings were composed of non-equilibrium tetragonal ZrO₂, which had a dense columnar microstructure. The phase constituent of the cross-sectioned TBCs was YSZ/Al₂O₃/TiAl₃/TiAl₂/TiAl from top to inner. The microhardness and high temperature wear resistance of TBCs were much higher than that of the substrate. The wear mechanisms of the Al-diffusion/YSZ are mild ploughing and severe adhesion at elevated temperature. The wear rate of TBCs was about 1/10 of the bare TiAl alloys.