The formation, microstructure and hot corrosion behaviour of slurry aluminide coating modified by Ni/Ni-Co electrodeposited layer on Ni-base superalloy
In this research, microstructure and hot corrosion behaviour of a modified aluminide coating were studied. The coating was formed via a two-step process, Ni/Ni-Co electrodeposition on Ni-base superalloy, Hastelloy-X, followed by slurry aluminising. The obtained coatings with 140 ± 5 μm thickness wer...
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Published in | Surface & coatings technology Vol. 402; p. 126283 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
Lausanne
Elsevier B.V
25.11.2020
Elsevier BV |
Subjects | |
Online Access | Get full text |
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Summary: | In this research, microstructure and hot corrosion behaviour of a modified aluminide coating were studied. The coating was formed via a two-step process, Ni/Ni-Co electrodeposition on Ni-base superalloy, Hastelloy-X, followed by slurry aluminising. The obtained coatings with 140 ± 5 μm thickness were characterised by an X-ray diffractometer (XRD) and scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscope (EDS) and elemental mapping before and after the corrosion tests. The results showed the β-NiAl for simple and pure Ni pre-plated, and the β-(Ni,Co)Al for NiCo pre-plated aluminised samples were formed definitely as a predominant phase. The initial electrodeposited layer performed as a Ni reservoir to reinforce aluminide formation. Besides, it reduced outward diffusion of alloying elements such as Cr, Fe, and Mo from substrate alloy as a diffusion retardant. Accordingly, the chemical composition of substrate alloy in pre-plated samples remained almost constant rather than its simple aluminised counterpart during the diffusion coating process. After the hot corrosion test carried out in the salt mixture of Na2SO4/NaCl environment, the results indicated that the presence of Co was beneficial and improved corrosion resistance of the obtained coating even in the Cl-containing salt mixture.
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•The efficient technique of the electrodeposition was used as one of coating steps.•The deposited layer was performed as a diffusion retardant for alloying elements.•The corrosion resistance of coating was improved even in Cl-containing environment. |
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ISSN: | 0257-8972 1879-3347 |
DOI: | 10.1016/j.surfcoat.2020.126283 |