The oxidation resistance of the diffusion aluminide bond coat (BC) is compromised largely by interdiffusion (ID) effects on coated turbine blades of aeroengines. The present study is designed to understand the influence of ID on βNiAl coatings or BC. In this regard, nickel substrate and CMSX-4 superalloy are deposited. In total, four sets of BCs are developed, i.e. pure βNiAl (on Ni substrate), simple βNiAl (on CMSX-4 substrate), Zr-βNiAl (on CMSX-4 substrate) and Pt-βNiAl (on CMSX-4 substrate). The main aim of this study is to understand the interdiffusion of Al, Zr and Pt during preparation and oxidation. In addition, the beneficial effects of both Zr and platinum are assessed. Pure βNiAl and simple βNiAl show Ni-outdiffusion, whereas for platinum inward diffusion to the substrate is noticed under vacuum treatment. Interestingly, Zr-βNiAl shows the least ID in all BCs and exhibit stability under both vacuum and oxidation treatments. However, its spallation resistance is slightly lower than that of Pt-βNiAl BC. All BCs show similar oxide growth trends, except for Zr-βNiAl, which exhibits two-stage oxidations, i.e. transient and steady-state. Moreover, it is suggested that the localized spallation in all BCs is caused by βNiAl - γ’-Ni3Al transformation.

1. Introduction
1. Introduction
2. Materials and Methods
3. Results
    3.1. Coatings Cross-sections
    3.2. The chemical composition of BCs
    3.3. Oxide Morphologies
    3.4. Mass Gain Trends and EDS Mapping
4. Discussion
    4.1. Pure and simple βNiAl
    4.2. Zr-βNiAl
    4.3. Pt-βNiAl
5. Conclusions
References

• Ali Dad Chandio(Department of Metallurgical Engineering, NED University of Engineering and Technology) Corresponding author
• Nafisul Haque(Department of Metallurgical Engineering, NED University of Engineering and Technology)
• Asif Ahmed Shaikh(Department of Metallurgical Engineering, NED University of Engineering and Technology)