Effect of Zr Content on Oxide-scale Spallation of Aluminide Coating

In the present study, zirconium modi􀀓ed aluminide coating on the nickel-base superalloy IN-738LC was 􀀓rst created by high activity high temperature aluminizing based on the out-of-pack cementation method. Then, Zr coatings were applied to simple aluminide coatings by sputtering and heat treatment in order to study the effect of Zr on the coating microstructure and oxide spallation. Microstructural studies were conducted by using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and X-ray diffraction (XRD) microanalysis. The results indicated that zirconium modi􀀓ed aluminide coating, like aluminide coating, has a two-layer structure including a uniform outer layer of NiAl and an interdiffusion layer in which zirconium is in a form of solid solution in the coating. Furthermore, the 300 nm Zr-coated NiAl demonstrated an excellent scale adhesion, a slow oxidation rate and lower amounts of other elements such as Ti and Cr in its oxide layer lead to a pure aluminide oxide layer.