Abstract
In general, 8 mass%Y2O3-ZrO2(8YSZ) coating materials are used as the top layer of thermal barrier coatings(TBCs). The development of hafnium oxide TBC was started in order to realize the high reliability and durability in comparison with 8YSZ, and the 7.5 mass%Y2O3-HfO2(7.5YSH) was selected for top coating layer. By the investigation of Electron Beam-Physical Vapor Deposition (EB-PVD) process, 7.5YSH top coating with about 200 μm thickness was formed. The 7.5YSH coating layer formed at substrate temperature of 956°C was composed of large solid columns aligned in the <200> and <311> direction of tetragonal crystallite. The thermal conductivity of 7.5YSH coating was lower than that of 8YSZ coating at temperature range of 1000°C~1300°C. From the result of sintering behavior obtained by heating test for 7.5YSH coating, it was recognized that the thermal durability for sintering behavior of 7.5YSH coating was improved up to about 100°C in comparison with 8YSZ coating.
