A Highly Strain and Damage Tolerant Thermal Barrier Coating Fabricated by Electro-sprayed Zirconia Hollow Spheres

An approach to make air plasma sprayed (APS) thermal barrier coatings (TBCs) with the enhanced strain and damage tolerance was reported, using a novel hollow spheres produced by electro-spraying (ESP) technique. Compared with agglomerated & sintered (A&S) and hollow spherical (HOSP) yttria-stabilized zirconia (YSZ) powders, the ESP powder showed a unique network microstructure and the TBCs exhibited a 2-3 times longer thermal cycling lifetime. The splat morphology and the top coats microstructure were investigated. Some semi-melted ESP particles were observed in the as-sprayed top coat. The indentation coupled with the Raman mapping technique was employed to evaluate the strain and damage tolerance of the TBCs. The coatings deposited by the ESP powder show a lower in-plane stiffness determined by three-point bending tests. It is proposed that the superior performance is attributed to the lower amount of the short microcracks (0.5-4 μm) with low angle (< 45°) and the semi-melted ESP particles remained in the YSZ top coat.