Effects of microstructure design and feedstock species in the bond coat on thermal stability of thermal barrier coatings

The effects of the microstructure design and feedstock species in a bond coat on the thermal stability of thermal barrier coatings (TBCs) were investigated through thermal shock (TS) tests. Three kinds of feedstock (AMDRY 9951: cobalt (Co)-based feedstock, AMDRY 997 : nickel (Ni)-based feedstock, and AMDRY 9624 : Ni-based feedstock) were employed for the single layer bond coat and the first layer in the double layer bond coat, which were prepared by high velocity oxy-fuel process. The second layer in the bond coat and the top coat was formed by air plasma spray process using Ni-based metallic powder (AMDRY 962) and 8YSZ (METCO 204 C-NS), respectively. The TS tests were performed till more than 50% of the region spalled in the TBC. The TBC system with the Co-based bond coat showed a better thermal durability than those with the Ni-based bond coats. The TBC systems with the double layer in the bond coat showed a better lifetime performance than those with the single layer, independent of the feedstock species.