presentation by awais

8/8/2019 Presentation by Awais

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Characterization of Multi layer coatingson Ferrous substrates including High

Energy Permanent Magnets

By:

Muhammad Awais

2005- MS -Met - 09

Project Supervisor:Prof. Dr. Akhlaq Ahmad Malik


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IntroductionIntroduction Two main functions of deposited coatings:

Protection Against Corrosion and Abrasive Wear

Multiple-Layer Coating

A new emerging technology to produce the desired

engineering properties (i.e. particular corrosionprotection).

Different layers of different coatings materials on themetallic substrate either using same coating techniqueor different coating technique.

Binary Multiple-layer Coatings Systems:

Ni/Cu, Ag/Pd, Ni/TiN

Ternary Multiple-layer Coatings Systems:

Ni/Cu/Ni


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STEEL

Nickel

Cathodic Coating

Steel is anodic w.r.t Ni.

Small crack in cathodic

layer will allow more

corrosion of steel due tosmall exposed area of Steel,

anodic current density will

be high.

The electrons produced

by steel will be consumed

by larger cathodic area.


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Steel is cathodic w.r.t

Zn.

Small hole in anodic

layer will allow very slowcorrosion of steel because

the electrons produced by

Zn will not be consumed

by cathodic steel surface

in a way they are

produced because of

small exposed surface.

Zn Zn

Anodic Coatings

Steel


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MultiMulti--layer Coatingslayer Coatings Cu is cathodic w.r.t Ni.

A c

rack in the top Ni layerwill find under lying Cu

that is cathodic to Ni and

the small exposed area of

cathodic Cu is lessdetrimental to large

surface area of anodic Ni.

Ni below the Cu deposit is

actually the strike layernecessary for electrplating

of Cu on Fe-based high

energy permanent magnet

alloys.

Fe-Substrate

NiCuNi


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Objectives

1. To produce multilayer Ni-Cu-Ni coatings by usingelectroplating technique and Ni-Cu-Ni/P coating

on Fe-based high energy permanent magnet

substrates by using electroplating and electroless

plating technique.

2. To characterize the multi-layer coatings by Optical

Microscope ,EDX and XRD.

3. To study the Corrosion Resistance of multilayeredcoated and uncoated samples.

4. To measure the magnetic properties by using

HyMPulse Magnetometer.


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Flow diagram ofFlow diagram ofExperimental workExperimental work


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Preparation of SubstrateSamples

Ni electroplating onFerrous Substrate

Cu electroplatingon Ni-plated samplesElectroless Nicoating on Ni-Cu

electroplatedsamples

Ni-Electroplating

on Ni-Cuelectroplated

samples

Characterization byMicroscope,EDX & XRD

Corrosion test byusing

Corrosion Studies Kit

Heat Treatment ofSamples afterelectroless Ni

coating

MagneticProperties

Measurement


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Preparation of SubstratePreparation of Substrate

The Substrates used for the experimental work

were made ofFe-based High Energy Permanent

Magnet.

Taken from the old Computer Hard Discs

Heated up to 350C0 in a furnace and soaked for

15 minutes to demagnetize.

These samples were cut into the desireddimensions.


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Composition of Substrate as analyzed by By

EDX Analysis ignoring B Content

Spectrum Label Fe Nd Total

Spectrum 1 76.25 23.75 100.00

Spectrum 2 76.82 23.18 100.00Spectrum 3 76.72 23.28 100.00Spectrum 4 77.39 22.61 100.00

Max. 77.39 23.75

Min. 76.25 22.61

All results in Weight Percent


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Nickel Electroplating onNickel Electroplating on NdNd--FeFe--BBSubstrateSubstrate

Compound Composition

NiSO4

300 g/l

NiCl2

60 g/l

Boric acid 37.5 g/l

For obtaining Ni

strike layer upon the

substrate,W

attsSolution was used

whose composition

is given as:


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Heating of Watts solutionHeating of Watts solution

PH:4-5 (pH meter)Temp: 70 - 75 C

Watt`s Solution

Heating


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Setup for Ni electroplatingSetup for Ni electroplating

Cathode

Wattssolution

Anode


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SetSet--Up for Cu ElectroplatingUp for Cu Electroplating

The substrate with

Ni strike layer was

dipped into the

bath as shown in

fig:


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Electroless Ni Coating On NiElectroless Ni Coating On Ni--Cu PlatedCu PlatedSamplesSamples

Nickel Sulphate 14g/l

Sodium

Hypophosphite20g/l

Tri-Sodium Citrate 73.5g/lAmmonium

Sulphate65g/l

The hypophosphitebased bath was used

for Electroless Ni-

coating.

Electrolytic Ni strikefor 30-40 seconds was

used to make the

samples catalytically

active because copperis classified as non-

catalytic metal for

electroless deposition.

pH (NH4OH) 9

Temperature (rC) 902Deposition Rate

(Qm/hr)15


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Heat Treatment Of Samples After

Electroless Ni Coating

After electroless Ni coating on Ni-Cu

electroplated samples, the samples wereannealed at different temperatures i.e.

300C0, 500C0 and 700C0.


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CharacterizationCharacterization Optical Microscopy

Olympus Microscope equipped with digital camera.

XRDSiemens D-500 X-ray diffractometer was used for phase

analysis using Ni filtered Cu-ka radiations and Origin-5

graphic software.

EDXJEOL 6300 SEM equipped with energy dispersive x-ray

analyzer (EDX) was employed to determine the chemical

compositions of the deposits.


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Corrosion Studies KitCorrosion Studies Kit

Corrosion tests for the multilayered coated

samples were made by using Corrosion Studies Kit.

Samples were tested in NaCl solutions.


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Magnetic Properties Measurement

Magnetic properties of un-coated and coated ferrous

based high energy permanent magnet samples were

measured by HyMPulse Magnetometer.


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Resu

ltsA

ndD

iscu

ssionR

esu

ltsA

ndD

iscu

ssion


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The Effect Of Plating Parameters OfThe Effect Of Plating Parameters Of

Electroless Ni Coating OnD

epositionR

ateElectroless Ni Coating OnD

epositionR

ate

The plating parameters i.e. pH and

Temp.

strongly affect the deposition rateand chemical composition of thedeposits.


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The Effect of pH on Deposition RateThe Effect of pH on Deposition Rate

It is clear from the fig. that the deposition rate is increased with an

increase in the pH of solution up to pH:8.5 and then it drops


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The Effect of the Temperature onThe Effect of the Temperature onDeposition RateDeposition Rate

The deposition rate is increased with an increase in thebath temperature of solution. Max. deposdtion rate is attemp:90C0


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EDX analysis of the top electroless Ni depositsEDX analysis of the top electroless Ni depositsplated at varying bath pH valuesplated at varying bath pH values

Deposits Ni-P

pH

Elements (atomic %)

Ni P

7.0 82.0 18.0

7.5 81.7 18.3

8.0 82.3 17.7

8.5 85.7 14.3

9.0 93.5 6.5

P content decreased withincreasing pH of the bath.

This is probably related to thefollowing reaction, which under

equilibrium conditionsindicates a decrease inelemental P with the increasein OH- ions.

H2PO2- + Hads H2O + OH

- + P

In Ni-P deposits, Ni content is

increased with the increase ofPH.


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Microstructure Of NiOf Ni--CuCu--Ni/P Plated OnNi/P Plated OnFeFe--Based MagnetBased Magnet

18.81m10.68m13.22m

Coatings Thicknessesmeasured by MicronScale


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Microstructure for ElectroplatedNi-Cu-Ni layers

13.96 m 26.38 m10.34 m

Coatings Thicknessesmeasured by MicronScale


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XX--ray Diffraction Analyses For Multilayerray Diffraction Analyses For MultilayerNiNi--CuCu--Ni Plated SamplesNi Plated Samples

The calculations and phase identification by Henawalt method show thatthere are only two phase present i.e.Ni and Cuand no intermetalliccompound is formed in electroplating.


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AS PLATEDShows one broad humpat 60-80o with a largeamorphous band. This

pattern is of amorphousmaterial. 300CSharp Peaks of F.C.C Ni,Cu, tetragonal Ni3P andhexagonal Ni5P2. 500C

Metallic Ni, Cu andNi5P2.The Quite SharpPeaks with less broadbases indicating graingrowth and increase incrystallinity of the

deposits.

700CThe heat treatment athigher temp(>500C)does not produce anyfurther visible changein the structure.


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Corrosion Testing KitCorrosion Testing Kit


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Composition SampleInitial Wt.

(gm)

1 week

(gm)

2 weeks

(gm)

3 weeks

(gm)

4 weeks

(gm)

Corrosion rate

mpy=534W/DAT

5% NaCl SolutionBare

Sample2.274 2.2138 2.154 2.093 2.032 9.01

5% NaCl SolutionNi-Cu-Ni coated

Sample2.312 2.302 2.293 2.283 2.273 1.22

5% NaCl SolutionNi-Cu-Ni/P

(without annealing)2.351 2.343 2.336 2.329 2.321 0.99


( annealing at 300C)2.423 2.415 2.406 2.398 2.390 1.10


(annealing at 500C)2.342 2.333 2.324 2.316 2.307 1.17


(annealing at 700C)2.320 2.311 2.302 2.293 2.284 1.19

Comparison of corrosion rate for bare sample and multilayer coated SamComparison of corrosion rate for bare sample and multilayer coated Samples


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Magnetic PropertiesMagnetic Properties


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Un-Coated Nd-Fe-B Magnet

Ni-Cu-Ni coated Nd-Fe-B Magnet

Ni-Cu-NiP coated Nd-Fe-B MagnetPost-Annealed Ni-Cu-NiP coated Nd-Fe-B


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Samples Br(T)

Hc(KA/m)

BH(max)(TKA/m)

Un-CoatedMagnet

1.20 782.600 688.405

Ni-Cu-Ni

electroplatedMagnet

1.17 775.362 682.890

Ni-Cu-NiP CoatedMagnet

1.00 695.652 458.330

Post-AnnealedNi-Cu-NiP CoatedM

agnet

1.05 768.116 538.043

Magnetic Properties of Coated and Un-coatedSamples


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3. The results of XRD show no intermetallic compoundwas produced in Ni-Cu-Ni electroplated multilayer

system.4. The corrosion test results clearly indicate that the

corrosion protection properties of electroplated Ni-Cu-Ni Fe-based magnet are less than the corrosionprotection properties of the top electro-less Ni coatedon Ni-Cu electroplated Fe-based magnet.

5. The corrosion resistance of the top electro-less Nicoated on Ni-Cu electroplated Fe-based magnet isdependent on the annealing treatment after coating.I

t is better in as deposit condition than post-annealing conditions


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6. There are no change in magnetic properties of magnets after electroplating Ni-Cu-Ni multi-layercoating system on magnets.

7. The magnetic properties of Ni-Cu-Ni/P plated magnetsare slightly decreased in as-deposit condition due to

amorphous structure.8. After post-annealing magnetic properties are increased

due to recystallization of electroless deposit.


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THANKSTHANKS

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