Abstract
Effect of MCrAlY bond coat alloy systems on thermal fatigue failure of thermal barrier coatings (TBCs) was investigated, where the TBC specimen consists of Ni-based superalloy IN738 substrate, bond coat, and 8 wt.% Y_2O_3-stabilized ZrO_2 (YSZ) topcoat. The top coat was fabricated by EB-PVD method with 250 μm in thickness. Three kinds of MCrAlY alloys were studied as the bond coat material. Employing the originally developed test equipment, the thermal fatigue tests were carried out, by applying thermal cycles between 400 and 950℃ in air. Special attention was paid not only to the failure lives themselves, but the underling failure mechanisms. The experimental results clearly demonstrated that the effect of MCrAlY bond coat alloys on the thermal fatigue life was very significant. Some mechanical and material backgrounds of these experimental results were discussed, based on the measurements of the mechanical and metallurgical properties of the bond coat: i.e., elastic stiffness, thermal expansion coefficient and high temperature oxidation resistance.
