Thermal cycling behavior of EB-PVD TBCs with Pt modified aluminide bond coat

Abstract

The（Ni, Pt）Al bond coats were prepared on the surface of nickel base single crystal superalloy by chemical vapor deposition（CVD）, and then YSZ ceramic coats were directly deposited on the surface of bond coats by electron beam physical vapor deposition（EB-PVD）.The influence of phase constituent of bond coat on the cyclic oxidation behavior of （Ni, Pt）Al/YSZ thermal barrier coatings was investigated in detail. The phase structure, morphology and chemical composition of the coatings were analyzed. The experimental results show that the bond coat is mainly composed of β-（Ni,Pt）Al and PtAl2 phases and the contents of the as-deposited bond coat are primarily including Ni, Al, Pt, Co and Cr elements. The spallation location of the TBCs probably occurs at the interface of TGO layer and bond coat, inside of TGO layer and within the bond coat. After thermal cycling test, it is found that the spallation may occur in the interior and interface of TGO and adhesive layer. With the extension of thermal exposure time, the residual stress located at the TGO layer decreases gradually in total. Therefore, controlling the precursor activity, Pt/Al element content, inhibiting the formation of brittle PtAl2 phase, improving the interfacial toughness of TGO layer/bonding layer, and reducing the stress-strain level of TGO layer are important ways to extend the thermal cycling life of（Ni, Pt）Al/YSZ thermal barrier coatings.

Keywords

• thermal barrier coatings
• thermal cycling
• phase structure
• interface
• failure