Microstructure, thermal conductivity and thermal cycling behavior of thermal barrier coatings prepared by plasma spray physical vapor deposition

• YSZ coatings with three different microstructures were deposited by PS-PVD.
• The effect of microstructure on thermal conductivity of PS-PVD YSZ coatings was studied.
• The YSZ TBCs with optimized microstructure showed a good performance in thermal cycling tests.

Plasma spray physical vapor deposition (PS-PVD) was used to deposit yttria stabilized zirconia (YSZ) coatings with microstructures varying from dense lamellae to quasi-columns out of vapor, as well as hybrid microstructure resulting from liquid droplet and vapor co-deposition. Among the coatings investigated, the quasi-columnar coating exhibited the lowest thermal conductivity of around 1.1 W/mK at 1200 °C due to high porosity and defects. The quasi-columnar coating also had an average life of around 2000 cycles during flame shock testing with a coating surface temperature of ~ 1200 °C. The failure of the coating occurred through cracking at the interface between the thermally grown oxide (TGO) layer and YSZ top coat.