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Rhodium and Hafnium Influence on the Microstructure, Phase Composition, and Oxidation Resistance of Aluminide Coatings

Department of Materials Science, Rzeszow University of Technology, W. Pola 2 str., 35-959 Rzeszow, Poland
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Metals 2017, 7(12), 548; https://doi.org/10.3390/met7120548
Received: 12 October 2017 / Revised: 28 November 2017 / Accepted: 29 November 2017 / Published: 7 December 2017
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Abstract

A 0.5 μm thick layer of rhodium was deposited on the CMSX 4 superalloy by the electroplating method. The rhodium-coated superalloy was hafnized and aluminized or only aluminized using the Chemical vapour deposition method. A comparison was made of the microstructure, phase composition, and oxidation resistance of three aluminide coatings: nonmodified (a), rhodium-modified (b), and rhodium- and hafnium-modified (c). All three coatings consisted of two layers: the additive layer and the interdiffusion layer. Rhodium-doped (rhodium- and hafnium-doped) β-NiAl phase was found in the additive layer of the rhodium-modified (rhodium- and hafnium-modified) aluminide coating. Topologically Closed-Pack (μ and σ) phases precipitated in the matrix of the interdiffusion layer. Rhodium also dissolved in the β-NiAl phase between the additive and interdiffusion layers, whereas Hf-rich particles precipitated in the (Ni,Rh)Al phase at the additive/interdiffusion layer interface in the rhodium- and hafnium-modified coating (c). The rhodium-modified aluminide coating (b) has better oxidation resistance than the nonmodified one (a), whereas the rhodium- and hafnium-modified aluminide coating (c) has better oxidation resistance than the rhodium-modified (b) and nonmodified (a) ones. View Full-Text
Keywords: rhodium; hafnium; aluminide coating; CMSX 4 superalloy; oxidation rhodium; hafnium; aluminide coating; CMSX 4 superalloy; oxidation
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Zagula-Yavorska, M.; Wierzbińska, M.; Sieniawski, J. Rhodium and Hafnium Influence on the Microstructure, Phase Composition, and Oxidation Resistance of Aluminide Coatings. Metals 2017, 7, 548.

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