Microstructures and deposition mechanisms of quasi-columnar structured yttria-stabilized zirconia coatings by plasma spray physical vapor deposition

Quasi-columnar yttria stabilized zirconia (YSZ) ceramic coatings were prepared by plasma spray physical vapor deposition (PS-PVD). In order to study the formation of quasi-columnar microstructure, coating morphologies and phases were investigated for each set of deposition times and standoff distances. Co-deposited by solid particles, liquid droplets, and vapor phases, the quasi-columnar coating was featured with “wedge” structure where vapors nucleated on micron-sized particles and grew to columns. Compared to the quasi-columnar coating deposited at 1000 mm, an extended spray distance of 1900 mm had lower growth rates, and resulted in the coating with larger columns and more solidified YSZ particles. A three-dimensional deposition model for quasi-columnar coatings was established. Moreover, the quasi-columnar YSZ TBCs exhibited low thermal conductivity of around 1.1 W/m K at 1100 °C and had a lifetime of more than 1000 cycles during thermal cycling test.