Effect of a Delamination Initiation Strength between Thermal Barrier Coating and Base Metal on Thermal Aging
Masayuki Arai, Uichi Iwata, Toshio Sakuma and Masahiro Saitoh
Abstract:In this study, a delamination initiation strength evaluation method of thermal barrier coating using in a high-temperature component in a land based gas turbine was proposed, and the effect of the thermal aging on the TBC delamination initiation strength was investigated. As obtained results, (1) the delamination tests based on a four point bending were carried out by using a small specimen with a notch in TBC layer. It was found that the delamination occurred at a top coating layer beside the interface between the top coating and the bond coating layer. (2) the delamination initiation strength (decohesion), which was obtained from an average of a stress concentration along the interface around the notch root, was about 120MPa. By subjecting the specimen to the thermal aging for more than about 1000 hour, the delamination strength was reduced by about 20 Mpa. (3) In a cross section of a long term thermal-aged specimen, the thermally growth oxide (TGO) phase, a-Al2O3, was observed a the interface between the top coating and the bond coating by EDX analysis. It was found that the delamination initiation strength was inversely proportinal to the TGO layer thickness. Key Words:Gas turbine, Delamination strength, Four point bending test, Thermally growth oxide