Phase transformation behavior of nanocrystalline Ni–W–P alloys containing various W and P contents

Balaraju, JN and Kalavati, -- and Manikandanath, N T and William Grips, VK (2012) Phase transformation behavior of nanocrystalline Ni–W–P alloys containing various W and P contents. Surface & Coatings Technology, 206 . pp. 2682-2689. ISSN 0257-8972

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    Abstract

    In the present investigation, electroless (EL) ternary Ni–W–P coatings were prepared using hypophosphite based alkaline bath by varying sodium tungstate as tungsten source (5–80 g/L). Maximum amount of W incorporation (8.2±1 wt.%) was obtained when the bath contained about 20 g/L of tungsten source. At very high concentrations of W source in the bath the deposit contained about 4 wt.% W and 2 wt.% P. All the as deposited ternary coatings exhibited nodular surface morphology. X-ray diffractograms (XRD) obtained for as-deposited EL NiWP alloys indicated that crystallinity of the coatings increased with decrease in phosphorus content. Calculated grain size for the deposits varied from 1.2 to 12.7 nm when the tungsten source varied from 5 to 80 g/L in the bath. Higher crystallization temperatures were obtained due to codeposition in NiP matrix. Presence of metastable phases such as Ni5P2 and NiP apart from stable Ni and Ni3P was identified for the heat treated deposits (400 °C/1 h) containing lower amount ofWand higher amount of P. Whereas other ternary deposits after the heat treatment predominantly revealed face centered cubic (f.c.c.) Ni (111) peak. Activation energy for the crystallization of all the alloys has been carried out by modified Kissinger method. Microhardness measurements were carried out on all the deposits isothermally heat treated at 600 °C for 1 h

    Item Type: Journal Article
    Uncontrolled Keywords: Electroless, Ternary Ni–W–P,XRD DSC,Phase transformation
    Subjects: CHEMISTRY AND MATERIALS > Chemistry and Materials (General)
    Division/Department: Surface Engineering Division, Materials Science Division, Surface Engineering Division, Surface Engineering Division
    Depositing User: Ms Indrani V
    Date Deposited: 01 Oct 2012 15:42
    Last Modified: 01 Oct 2012 15:42
    URI: http://nal-ir.nal.res.in/id/eprint/11051

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