Preliminary Studies on the Development of Plasma Sprayed YSZ/Gd1.8Yb0.2Zr2O7 Thermal Barrier Coating from Powders Synthesized by Solution Combustion Method

Thermal barrier coatings (TBCs) play a vital role in enhancing the lifetime of gas turbine engine components. In recent years, research has been concentrated on the development of bilayer ceramic topcoats containing TBCs. Among the promising ceramic topcoats, rare earth zirconates and in particular Gd2Zr2O7 is a promising topcoat material because of its high-temperature stability, lower thermal conductivity and calcium magnesium alumino-silicate (CMAS) resistance. In the present study, a bilayer TBC system containing YSZ/ytterbia doped gadolinium zirconate (Gd1.8Yb0.2Zr2O7) is developed by atmospheric plasma spray (APS) process from flowable powders synthesized by solution combustion process by varying the plasma spray parameters. The solution combustion method yields flowable ceramic powders in a single step. The hot corrosion behavior of the best coating was tested by spreading a fused Na2SO4 + V2O5 mixture (~ 25 mg/cm2) on the surface of the coating and subjecting it to heat treatment at 910°C for 30 h. Post-hot corrosion tests, the phase, microstructure and elemental analysis of the coating were carried out using an X-ray Diffractometer (XRD), field emission scanning electron microscope and energy dispersive X-ray analyzer respectively. The details of the synthesis of Gd1.8Yb0.2Zr2O7 powder, plasma spraying of the bilayer coatings and characterization of the TBC are discussed in detail. The bilayer coating exhibited a thermal conductivity of 1.054 W/mK at 21°C compared to conventional YSZ coating.