Low Thermal Conductivity YSZ Thermal Barrier Coatings Made by the Solution Precursor Plasma Spray Process

Abstract

The vast majority of thermal barrier coatings (TBCs) are made using 7 wt% yttria stabilized zirconia (7YSZ) due to its high thermal expansion coefficient, high fracture toughness, relatively low thermal conductivity and modest use of rare earth elements (Y). Lower thermal conductivity in TBCs is highly desirable because it would allow thinner coatings and/or improved thermal protection. By arranging the porosity in layers using the solution precursor plasma spray (SPPS) process it has been demonstrated that a 7YSZ coating with 15–23% porosity can be reproducibly fabricated having a thermal conductivity of about 0.6W/m·K, approximately half of the thermal conductivity of air plasma spray (APS) TBCs. Preliminary tests show that both cyclic furnace durability and erosion resistance are comparable to APS TBCs.