Ni-W alloys with 16–28 at% tungsten (W) content were electrodeposited from citrate bath utilizing various pulse parameters. The influence of pulse parameters on microstructure, composition and mechanical properties was systematically studied. The corrosion behavior was analyzed in 1 M H2SO4 using potentiodynamic polarization and electrochemical impedance spectroscopy. Nanocrystalline Ni-W coatings were found to have superior corrosion resistance compared to their duplex nanocrystalline-amorphous counterpart. The corrosion behavior was rationalized based on semiconducting properties of oxide film using Mott–Schottky analysis and depth wise composition analysis utilizing X-ray Photoelectron Spectroscopy. An attempt is made to correlate corrosion current with intercrystalline defects. © 2019 Elsevier Ltd

Sundararajan G

Department of Metallurgical and Materials Engineering

Binary alloys

corrosion

Corrosion resistance

CORROSION RESISTANT COATINGS

Corrosive effects

Electrochemical impedance spectroscopy

Electrodeposition

Electrodes

Mechanical properties

Nanocrystals

Nickel alloys

Oxide films

Tungsten alloys

X ray photoelectron spectroscopy

COMPOSITION ANALYSIS

Corrosion behavior

ELECTROCHEMICAL CORROSION BEHAVIOR

INTERCRYSTALLINE DEFECTS

NANOCRYSTALLINE NI

NICKEL-TUNGSTEN

Schottky

Semi-conducting property

Electrochemical corrosion

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Corrosion Science

The present study deals with corrosion behaviour of compositionally modulated nanocrystalline Ni–W alloy coatings and conventional hard chrome coatings. Compositionally modulated Ni–W alloy coatings of known composition were systematically deposited using pulse current deposition. The corrosion behaviour was analysed using potentiodynamic polarization and impedance spectroscopy in 2N H2SO4. Compositionally modulated Ni–W alloy coatings depicted substantial improvement in corrosion resistance over its single-layer counterpart and hard chrome coatings. The corrosion behaviour was rationalized based on porosity and surface residual stresses present in these coatings. © 2019, © 2019 Institute of Materials, Minerals and Mining Published by Taylor &amp; Francis on behalf of the Institute.

Surface Engineering

Corrosion behaviour of compositionally modulated nanocrystalline Ni–W coatings

In the present work, the influence of molybdenum (Mo) content on the grain size, hardness, corrosion and wear behavior of Ni-Mo alloy coatings electrodeposited from citrate electrolyte has been studied. Crack free Ni-Mo alloy with different Mo content (3, 5, 6, 9 and 12 at.%) was obtained using direct current and pulsed current electrodeposition. It was observed that the grain size of Ni-Mo alloy decreased with increase in Mo content. Hardness of the coatings increased with Mo content and decreased subsequently above 9 at.% Mo as per inverse Hall-Petch effect. Potentiodynamic polarization tests carried out in 2 N H2SO4 suggested increase in both corrosion current and passive current density with increase in Mo content. In addition, both friction coefficient and dry sliding wear rate of Ni-Mo coatings decreased with increase in Mo content. The results are rationalized based on grain size and Mo content in the coatings. Finally, Ni-Mo and Ni-W coatings were compared with hard chrome with respect to mechanical properties, wear and corrosion resistance. Results indicated that, Ni-Mo coatings exhibit least friction coefficient (0.2–0.3) amongst Ni-W and hard chrome coatings. © 2019

Surface and Coatings Technology

Influence of molybdenum on the mechanical properties, electrochemical corrosion and wear behavior of electrodeposited Ni-Mo alloy

The primary objective of the present study is to investigate the influence of nanocrystalline grain size on the solid particle erosion behavior of nickel. For the above purpose, 450-μm-thick nanocrystalline Ni coatings having the average grain sizes of 21, 42, 70, and 195 nm were obtained using pulsed electrodeposition (PED). All these samples along with bulk annealed Ni samples (43&nbsp;μm grain size) were subjected to solid particle erosion using SiO2 particles as an erodent at a constant impact velocity of 45 m/s and two impact angles (30 and 90 deg). Erosion results indicate that bulk Ni and PED Ni coatings of grain sizes 195 and 70 nm exhibit the same erosion rate, while PED Ni coatings of 42 and 21 nm grain size exhibit marginally higher erosion rates with a clear trend of increasing erosion rate with decreasing grain size. It was also observed that the higher erosion rates exhibited by 21- and 42-nm-grain size PED Ni samples were associated with the formation of adiabatic shear bands (ASBs) originating from the eroded surface and propagating into the eroded sample. The experimental observations have been understood on the basis of a transition from a localization model for erosion for coarse-grained Ni (&gt;&nbsp;70&nbsp;nm) to an ASB-induced erosion model for grain sizes less than 70 nm. © 2017, The Minerals, Metals &amp; Materials Society and ASM International.

Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science

Solid Particle Erosion of Nanocrystalline Nickel Coatings: Influence of Grain Size and Adiabatic Shear Bands

In the present study the sliding wear behavior of pulse electrodeposited nanocrystalline Ni coatings as a function of grain size including bulk annealed Ni has been systematically studied using pin-on-disc configuration against the WC-Co counter body. The sliding wear has been analyzed with respect to wear rate, coefficient of friction, subsurface deformation and composition of wear debris. The result indicates that the sliding wear rate and coefficient of friction of Ni decreases with decreasing grain size. The subsurface beneath the worn pin surface is composed of a near surface shear region and beneath it a region of bulk plastic deformation. The ratio of the depth of the shear region to the depth of bulk deformed region decreases with decreasing grain size indicating a greater localization of near surface deformation with decreasing grain size. © 2012 Elsevier B.V.

Wear

Sliding wear behavior of nanocrystalline nickel coatings: Influence of grain size

The present work deals with evaluation of corrosion behaviour of electrodeposited nanocrystalline Ni-W and Ni-Fe-W alloys. Corrosion behaviour of the coatings deposited on steel substrates was studied using polarization and electrochemical impedance spectroscopy techniques in 3.5% NaCl solution while their passivation behaviour was studied in 1N sulphuric acid solution. The corrosion resistance of Ni-W alloys increased with tungsten content up to 7.54 at.% and then decreased. In case of Ni-Fe-W alloys it increased with tungsten content up to 9.20 at.% and then decreased. The ternary alloy coatings exhibited poor corrosion resistance compared to binary alloy coatings due to preferential dissolution of iron from the matrix. Regardless of composition all the alloys exhibited passivation behaviour over a wide range of potentials due to the formation of tungsten rich film on the surface. © 2007 Elsevier B.V. All rights reserved.

Materials Science and Engineering A

Corrosion behaviour of electrodeposited nanocrystalline Ni-W and Ni-Fe-W alloys

Influence of pulse parameters on the mechanical properties and electrochemical corrosion behavior of electrodeposited Ni-W alloy coatings with high tungsten content

Journal	Data powered by TypesetCorrosion Science
Publisher	Data powered by TypesetElsevier Ltd
ISSN	0010938X
Open Access	No