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Diffusion-controlled growth and microstructural evolution between Pt and Pd containing B2-NiAl bondcoats and Ni-based single crystal superalloy

Esakkiraja, N and Vishwakarma, A and Makineni, SK and Jayaram, V and Hickel, T and Divinski, SV and Paul, A (2024) Diffusion-controlled growth and microstructural evolution between Pt and Pd containing B2-NiAl bondcoats and Ni-based single crystal superalloy. In: Acta Materialia, 266 .

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Official URL: https://doi.org/10.1016/j.actamat.2024.119687


Pt-modified NiAl bond coats are used to extend the lifetime of blades in gas turbine engine applications. However, they suffer from the growth of deleterious precipitates within the interdiffusion zone. Partial substitution of Pt by Pd is advantageous in reducing the interdiffusion zone thickness between the bond coat and the superalloy, providing comparable oxidation properties, and critically reducing the propensity to form brittle (Pt,Ni)Al2 precipitates. In this study, we utilize the pseudo-binary diffusion couple method to estimate the interdiffusion coefficients of Ni and Al in Pd, Pd-Pt and Pt-modified nickel aluminides. Additionally, the main and cross-interdiffusion coefficients are estimated in the ternary diffusion couples. The estimated diffusion coefficients in the β-NiAl phase reflect on the thickness of the β phase in the superalloy bond coat interdiffusion zone. Pd reduces the pseudo-binary interdiffusion coefficients of Ni�Al and also decreases the main and cross-ternary interdiffusion coefficients. This correlates with the reduction of the interdiffusion zone thickness by Pd. The diffusion process is strongly assisted by point defects in this phase. Ab initio-informed defect calculations are done to explain diffusion retardation in the presence of Pd (compared to Pt) with decreased defect concentrations. Furthermore, through in-depth microstructure characterization performed by electron probe micro analyser, transmission electron microscopy, and atom probe tomography, the presence of �, R and μ phases as TCP precipitates in the interdiffusion zone are identified. The results give insights into the coatings� diffusional properties that influence the service life of the product. © 2024 The Authors

Item Type: Journal Article
Publication: Acta Materialia
Publisher: Acta Materialia Inc
Additional Information: The copyright for this article belongs to author.
Keywords: Aluminum alloys; Binary alloys; Diffusion; High resolution transmission electron microscopy; Microstructural evolution; Nickel alloys; Platinum; Point defects; Probes; Single crystals; Transmission control protocol, APT; Bond coats; Diffusion controlled growth; Diffusion couple; Interdiffusion; Interdiffusion coefficients; Ni-based single crystal superalloy; Pseudo-binaries; TCP phase; TEM, Superalloys
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 04 Mar 2024 06:30
Last Modified: 04 Mar 2024 06:30
URI: https://eprints.iisc.ac.in/id/eprint/84147

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