Formation and Properties of Porous ZrO2-8wt%Y2O3 Coatings

The efficiency of a gas turbine engine is highly dependent upon the clearance between blades and engine case. To control the over-tip leakage, an abradable coating system is sprayed on the case surface. In the high temperature section, a ZrO2-8 wt%Y2O3 (YSZ) coating is usually applied. Pores in the coating enhance its abradability. In this study, poly-p-hydroxybenzoate (PHB) powder mixed in the YSZ powder was used as pore-forming material. To avoid burning loss of PHB during the spraying process, a sol-gel method was used to clad a TiO2 shell on the PHB powder surface. The porous YSZ coating was deposited by plasma spraying. The characteristics of the coatings were investigated in this work, such as morphology, porosity, hardness, corrosion resistance and abradability. The results show that the coated PHB increases the porosity of the YSZ coating, and then decreases the coating hardness. Finally, a rotated invading test indicates the incursion depth increases with the increase of coating porosity, suggesting the coating abradability is improved.