Studies On Composition Optimizing Of Bond Coat In Thermal Barrier Coatings

Thermal barrier coatings(TBC) are the most significant materials on modern high-performance aero-turbine engines. They are widely used on important components of turbines working at high temperature, greatly improving the working temperature and lifetime of engines. However, after long time service under isothermal or thermal cycle circumstances, TBCs would become failure and spall off from substrates, incapable of protecting blades from high-temperature and oxidation environment, resulting in severe accidents and economic loss. Previous researches find that the high-temperature oxidation resistance of bond coat determines lifetime of TBC, in which the bond coat compositions is the main reason influencing the high-temperature oxidation resistance of bond coat.In this study, the effect of composition in bond coat on TBC failure was investigated. Typically, bond coat of TBC is composed of nickel aluminide dissolved with other metals such as Pt, Cr, Co, Y, etc., which is also called reactive elements(REs). The composition of Al and REs are determinations of high-temperature oxidation resistance of bond coat, especially the REs. In this research, we use bulks of nicel aluminides to investigate the roughness of interface between thermal grown oxide(TGO) and substrate, the TGO residual stress and the TGO growth rate, etc. The objective of this study is to obtain the optimal composition of NiAl bond coat.In this study, residual stress is measured by Cr3+ photostimutated luminescence spectroscopy(PLPS). The TGO/substrate interface roughness is measured by scanning electron microscopy(SEM) and image software. The roughness TGO surface is obtained by 3D optical profilerometer.It is found that the TGO/substrate interfacial roughness increases with an increase of the Al content in the substrate, improving the oxidation resistance of substrate. The substrate with 0.1at.% Hf has the longest thermal cycling lifetime, while the substrate with 0.3at.% Zr has the longest thermal cycling lifetime.