Fast synthesis of novel micron porous particles of Gd, Yb and Y-stabilized zirconia to prepare TBCs with low thermal conductivity

Abstract

The conventional agglomerated and sintered (A&S) zirconia granules for making plasma-spraying thermal barrier coatings (TBCs) was dense and nonporous. A novel porous A&S zirconia granule was reported in this work. Firstly, some novel porous spherical particles (about 1 μm) of zirconia partially stabilized by Gd, Yb and Y (Gd-Yb-YSZ) were synthesized by a new method using the carbon spheres as the templates. This made the subsequent liquid-solid separation by filtration much faster than the conventional sol-gel method. Then these micron porous Gd-Yb-YSZ particles were transformed to some big porous granules (30–90 μm) by a A&S method. Finally, these porous Gd-Yb-YSZ granules were used to make a novel porous TBC of Gd-Yb-YSZ on superalloy by air plasma spray, together with the nonporous granules of both Gd-Yb-YSZ and YSZ. The measured insulation temperatures of TBCs made from the nonporous YSZ granules, the nonporous Gd-Yb-YSZ granules and the porous Gd-Yb-YSZ granules were 45 °C, 59 °C and 94 °C, respectively, at a heat source temperature of 1050 °C. It indicated that the thermal conductivity of TBC decreased in the following order: nonporous YSZ granule specimen > nonporous Gd-Yb-YSZ granule specimen > porous Gd-Yb-YSZ granule specimen. The possible reasons for this result were investigated.