The effects of ultrasonic nanocrystal surface modification (UNSM) on pack aluminizing for the fabrication of Pt-modified aluminide coatings at low temperatures |
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| Affiliation: | 1. Laboratoire des Sciences de l''Ingénieur pour l''Environnement LaSIE UMR-CNRS 7356, Université de La Rochelle, Avenue Michel Crépeau, 17042 La Rochelle Cedex 1, France;2. Cranfield University SENTi, Cranfield, Bedfordshire MK43 0AL, UK;1. Laboratoire des Sciences de l''Ingénieur pour l''Environnement (LaSIE, UMR-CNRS 7356), Université de La Rochelle, Avenue Michel Crépeau, 17042 La Rochelle Cedex 1, France;2. ENCOMAT–Group, University of Vigo, 36310 Vigo, Spain;1. Department of Mechanical Engineering, University of Akron, Akron, OH 44325, USA;2. Department of Polymer Science, University of Akron, Akron, OH 44325, USA;3. Department of Mechanical Engineering, University of California - Merced, Merced, CA 95343, USA;4. Department of Chemical and Biomolecular Engineering, University of Akron, Akron, OH, USA;5. Timken Engineered Surfaces Laboratories, University of Akron, Akron, OH 44325, USA;6. Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, OH 45221, USA;7. School of Polymer Science and Engineering, Qingdao University of Science and Engineering, Qingdao 266042, China;8. Department of Geosciences, University of Akron, Akron, OH 44325, USA;9. Integrated Bioscience Program, University of Akron, Akron, OH 44325, USA |
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| Abstract: | An 8–9 μm thick Pt layer was coated on a superalloy and transformed to a Ni–Pt alloy layer by the interdiffusion of Ni and Pt at 1050 °C for 3 h. The surface of the Ni–Pt alloy layer was pack aluminized to form a Pt-modified aluminide coating. Ultrasonic nanocrystal surface modification (UNSM) was applied to the alloy layer prior to pack aluminizing. The effects of UNSM on Pt-modified aluminide coatings fabricated at 750, 850, 950, and 1050 °C were studied. The treated Ni–Pt alloy layers had finer grain sizes than the untreated specimens. In addition, UNSM made the grain size of the Ni–Pt alloy finer and reduced the surface roughness. During pack aluminizing, the Pt-modified aluminide coatings fabricated following UNSM uptook more Al and were thicker than the untreated Pt-modified aluminide coatings at the various temperatures (750, 850, 950, and 1050 °C). The untreated Pt-modified aluminide coatings with pack aluminizing performed at 750 and 850 °C were composed of only a two-phase (NiAl + PtAl2) layer, due to insufficient diffusion of Pt at the lower temperatures. However, two-phase and one-phase (NiAl) layers were obtained in the treated Pt-modified aluminide coatings which were pack-aluminized at 750, 850, 950, and 1050 °C, due to the diffusion of Pt through the greater amount of grain boundaries and increased volume generated by UNSM before the pack aluminizing. Additionally, the treated coatings had smoother surfaces even after the pack aluminizing. During cyclic oxidation at 1150 °C for 1000 h, the treated Pt-modified aluminide coatings aluminized at relatively low temperatures (750 and 850 °C) showed better cyclic oxidation resistance than the untreated Pt-modified aluminide coating aluminized at 1050 °C. |
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| Keywords: | A Aluminides miscellaneous B Oxidation C Surface finishing G Aero-engine components |
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