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| Abstract No.: |
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Scheduled at:
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Thursday, June 08, 2017, Hall 12 4:40 PM
Aviation & Power Generation Industry IV
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| Title: |
The influence of the coating deposition process on the interdiffusion behavior between nickel-based superalloys and MCrAlY bond coats
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| Authors: |
Moritz Elsass* / Technical University Darmstadt, Germany
Martin Frommherz / Chair and Institute for Materials Technology, Technical University Darmstadt, Germany
Alfred Scholz/ Chair and Institute for Materials Technology, Technical University Darmstadt, Germany
Matthias Oechsner/ Chair and Institute for Materials Technology, Technical University Darmstadt, Germany
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| Abstract: |
In this work, interdiffusion between different nickel-based superalloys and two MCrAlY bond coats, containing different chemical compositions, is investigated. To determine the influence of the coating deposition process, the MCrAlY bond coats were applied using two different spraying processes, high velocity oxygen fuel spraying (HVOF) and low-pressure plasma spraying (LPPS). Of primary interest is the evolution of Kirkendall porosity, which can form at the interface of substrate and bond coat and depends largely on the chemical compositions of the coating and substrate. Experimental evidence suggested also a dependence on the coating deposition process. Formation of porosity at the interface causes a degradation of the bonding strength between substrate and coating, with functional breakdown of the coating system as a worst result. After coating deposition, the samples were annealed at 1050 °C for varying test periods up to 2000 hours. Microstructural and compositional analyses were performed to determine and to evaluate the Kirkendall porosity. The results reveal a strong influence of both the spraying process and the chemical composition. The amount of Kirkendall porosity formed, as well as the location of appearance and the shape, is largely influenced by the coating deposition process. In general, samples with bond coats applied by means of HVOF show accelerated element diffusion. It is hypothesized that recrystallization of the substrate material, as a consequence of the surface treatment prior to coating deposition, is the main root cause for these observations.
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