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Characterization and microhardness of Co−W coatings electrodeposited at different pH using gluconate bath: A comparative study

Authors

  • Parthasarathi Bera,

    Corresponding author
    1. Surface Engineering Division, CSIR−National Aerospace Laboratories, Bangalore, India
    Current affiliation:
    1. Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
    • Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
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  • H. Seenivasan,

    1. Surface Engineering Division, CSIR−National Aerospace Laboratories, Bangalore, India
    2. Department of Chemical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
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  • K. S. Rajam,

    1. Surface Engineering Division, CSIR−National Aerospace Laboratories, Bangalore, India
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  • C. Shivakumara,

    1. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India
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  • Sanjit Kumar Parida

    1. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore, India
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Correspondence to: Parthasarathi Bera, Surface Engineering Division, CSIR-National Aerospace Laboratories, Bangalore 560017, India.

E-mail: partho@nal.res.in

Abstract

Electrodeposition of Co–W alloy coatings has been carried out with DC and PC using gluconate bath at different pH. These coatings are characterized for their structure, morphology and chemical composition by X-ray diffraction, field emission scanning electron microscopy, differential scanning calorimetry and X-ray photoelectron spectroscopy (XPS). Alloy coatings plated at pH8 are crystalline, whereas coatings electrodeposited at pH5 are nanocrystalline in nature. XPS studies have demonstrated that as-deposited alloy plated at pH8 with DC contain only Co2+ and W6+ species, whereas that alloy plated at pH5 has significant amount of Co0 and W0 along with Co2+ and W6+ species. Again, Co2+ and W6+ are main species in all as-deposited PC plated alloys in both pH. Co0 concentration increases upon successive sputtering of all alloy coatings. In contrast, mainly W6+ species is detected in the following layers of all alloys plated with PC. Alloys plated at pH5 show higher microhardness compared to their pH8 counterparts. Copyright © 2013 John Wiley & Sons, Ltd.

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