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Effect of reducing agent and nano Al 2 O 3 particles on the properties of electroless Ni-P coating
B. Ramamoorthy
Published in Elsevier B.V.
2014
Volume: 307
   
Pages: 654 - 660
Abstract
This work is an experimental study on the formation, characteristics and properties of electroless nickel phosphorous (Ni-P) coatings and electroless nickel alumina (Ni-P-Al 2 O 3 ) coating with varying reducing agent concentration. The results obtained indicate that the deposition rate and surface roughness of both Ni-P coating and Ni-P-Al 2 O 3 coatings are highly influenced by reducing agent (sodium hypophosphite). With increase in sodium hypophosphite Ni forms amorphous phase and as a result the micro hardness of the coating gets reduced. Heat treatment was carried out at 400 °C for 1 h after the coating, resulted in the formation of an intermetallic nickel phosphide (Ni 3 P) phase which improved the hardness of the Ni-P coating from 400 ± 25 to 700 ± 25 HV. A composite coating is formed due to the incorporation of nano alumina in the Ni-P coating leading to an increase in the hardness. The chemical composition of nickel gets reduced from 85.3 to 77.8 wt.% due to the presence of alumina which resists the deposition of Ni. The uniform distribution of alumina particles are observed using a scanning electron micrograph and confirmed by X-ray diffraction techniques. The specific wear rate of Ni-P-Al 2 O 3 coated and post coating heat treated specimens was observed to be less when compared with that obtained in the case of conventional Ni-P coating. © 2014 Elsevier B.V. All rights reserved.
About the journal
JournalData powered by TypesetApplied Surface Science
PublisherData powered by TypesetElsevier B.V.
ISSN01694332
Open AccessNo
Concepts (20)
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    Alumina
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    Aluminum oxide
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    Composite coatings
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    Deposition rates
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    Microhardness
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    Nickel coatings
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    REDUCING AGENTS
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    Scanning electron microscopy
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    Sodium
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    Surface roughness
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    X ray diffraction
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    Chemical compositions
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    ELECTROLESS NI-P COATING
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    ELECTROLESS NICKEL-PHOSPHOROUS
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    Heat-treated specimens
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    NI-P COATING
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    Scanning electron micrographs
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    SODIUM HYPOPHOSPHITE
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    X-ray diffraction techniques
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    Nickel compounds