Plasma-sprayed Yb3Al5O12 as a novel thermal barrier coating for gas turbine applications

In this study, the garnet-type Yb3Al5O12 coating was fabricated by atmospheric plasma spraying and its properties were systematically investigated. Results show the as-sprayed coating consists of crystalline Yb3Al5O12 with amorphous phase, recrystallization occurs at 918.5ºC accompanied by a 0.32% volume shrinkage. Yb3Al5O12 coating demonstrates low thermal conductivity (2.1 W/(m∙K) at 1000ºC) coupled with a moderate thermal expansion coefficient (8.87 ×10-6 K-1 from 200 ºC to 1400 ºC). Additionally, Yb3Al5O12 coating displays remarkable structure stability and sintering resistance at elevated temperatures. Its robust corrosion resistance can be demonstrated by rapidly generating dense anorthite layers during CMAS corrosion and the lack of a discernible corrosion layer in water vapor corrosion. Yb3Al5O12/YSZ TBC undertakes a thermal cycling lifetime of 970 cycles, superior to YSZ of 764 cycles. This improvement is primarily ascribed to lower oxygen permeability of garnet layer. These preliminary results indicate that Yb3Al5O12 coating might be suitable for advanced TBC applications.