Effects of the substrate temperature on microstructure and property of EB-PVD gradient thermal barrier coatings

Gradient thermal barrier coatings have been prepared by co-evaporation and deposition of the mixture sources of Al-Al₂O₃-YSZ onto superalloy substrate by means of electron beam physical vapor deposition (EB-PVD). It is found that the microstructures and properties were significantly determined by the temperature of substrate. The gradient coating deposited at 850°C, where a microstructure gradually transfers from metallic bond coat to ceramic topcoat, has a thermal cycling lifetime of more than 500 h (1000 cyc) at 1050°C. Due to shadow effect, a gradient porous microstructure was formed in the coating and led to the micro-hardness in the coating gradually increasing towards the surface of the coating. Simultaneously, the micro-porosity in the coating increased with the rise of the temperature of the substrate, and the micro-hardness of the coating decreased thereby.