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

Abstract

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 1.1W/mK at 1200°C due to high porosity and defects. The quasi-columnar coating also had an average life of around 2000cycles 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.