Thursday, 02 June 2011

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Facilitating Sustainability through Surface Engineering by Measurement and StandardsM G GeeNational Physical Laboratory

14th June 2011IMF Fair

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Sustainability and Surface Engineering

Surface engineering can help with the sustainable use of materials and resources by e.g.:

Enabling the use of lightweight materials in transport applications leading to fuel efficiencyDevelopment of low friction in power plant and transmissions giving improved fuel efficiencyImproved durability of components and systems Improved manufacturing efficiencyLower materials use

To design effective surface engineering solutions we require good data for design

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Sustainability and MeasurementThree approaches to measurementAssess operating conditions in application, extract key conditions, model and then measure important parameters to achieve prediction of performanceIssues: reliability of extracting key parameters, difficulty in modelling, choice of important parameters, extrapolation is difficult, but can be much cheaperReproduce operating conditions exactly so that good reliable simulation performance can be achievedIssues: can we reproduce operating conditions well enough, can be very expensiveTry it and see (field testing)Issues: Often doesn’t work, so repeated iterations are expensive, in many cases you cannot do this for safety etc reasons

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Coatings MeasurementMeasurements needed in areas such as:

ThicknessChemistryStrength and adhesionHardness and elastic propertiesMeasuring wear and frictionDurabilityResidual stress

Aim is to make measurements simpler, more relevant, cheaper, more robustStandardisation can give improved framework for measurements

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Video

Acoustic emission

Strain gauge

Load cell

Rollers

Motor drive

Displacement Sensor

Measuring Coating Integrity by Bend Testing

ContextNeed to provide information on integrity of coatings under mechanical loading

ScienceUse instrumented bend testing Acoustic emissionVideo to detect cracking

Future VisionIs being taken forward into work to provide simple test for near shop floor environmentProposal for standardisation in CEN

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Bend Testing

Force displacement curves Acoustic emission

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Bend Testing - Comparison of Samples

Hydroxyapatite

Chromium Carbide: Fine Ground

Chromium Carbide: Coarse Ground

Tungsten Carbide: Fine Ground

Tungsten Carbide: Coarse Ground

Hard Chrome

Codeposited Electroplate

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Bend Testing - Case Study

Coated tubeCompare performance of oxidised and unoxidisedtube

Force vs displacement summary(all pipes)

0

100

200

300

400

500

600

700

800

900

-2 0 2 4 6 8

Displacement (mm)

Forc

e (N

)

Coated 1

Coated 2

Coated 3

Ox 1000 1

Ox 1000 2

Ox 1000 3

Ox 1100 1

Ox 1100 1b

Uncoated 1

Uncoated 2

Uncoated 3

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Rockwell adhesion test

Radius of delamination , r

Load

Radius of indenter, a

Rockwell C indent made into coated specimen

Fracture and delamination around indent indicates adhesion properties

Rockwell Indentation Adhesion Test: Drory and Hutchinson Analysis

MCrAlY Coating on Mar M002 Substrate

ΓC=1470 J m-2ΓC= 680 J m-2

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Scratch Testing

acousticemission

tangentialforce

load

opticalinspection

of failure modes

acousticemission

tangentialforce

load

opticalinspection

of failure modes

0 20 40 60 80 1000

10

20

30

40

Fric

tion

Forc

e, N

Load, N0 20 40 60 80 100

20

30

40

50

60

70

80

AE

Sig

nal,

dB

Applied load, N

Lc = 21.3 NLc = 21.3 N

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Scratch Testing - TranverseNormal Load(10 to 80 N)

Coating

Substrate

Rockwell Indenter

Direction of Travel

Substrate

Coating

Direction of Travel

10 N

80 N

Cra

ck le

ngth

, µm

Critical Load (Lc)

0

200

400

600

800

1000

0 20 40 60 80 100 120 140 160 180 200

Indenter Load, N

50 N

80 N

10 N

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Fracture Analysis in Scratch Testing

First principle stress

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Pulsed Thermography

Heat conduction

IR radiationFlash lamp

Thermal camera

to PC

Bond-coat delamination on power turbine vane

Type of failure prevented

Saving on power disruption, downtime, cost

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Coupon Bending for Residual Stress Measurement

Residual stress from thermal expansion mismatch and processing effectsFor thin coatings Stoneyformula; thick coatings more complex formulaMethods for measurement

Profilometry- Flexus

Optical microscopeLVDT

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-20 -10 0 10 20 30-250

-200

-150

-100

-50

0

Def

lect

ion,

μm

Distance, mm

Optical Flexus

-60 -50 -40 -30 -20 -10 0

0.0

0.5

1.0

1.5

2.0

Hei

ght,

mm

Distance,mm

Substrate Finish and Thickness Fine, 1.2 Fine, 2 Fine, 3 Coarse, 1.2 Coarse, 2 Coarse, 3

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 3.20

100

200

300

400

500

600

700

800

900

1000

1100

1200

Res

idua

l Stre

ss, M

Pa

Substrate Thickness, mm

Coarse Freund Fine Freund Coarse Stoney Fine Stoney

Coupon Bending for Residual Stress Measurement

Optical microscope measurements on thermally sprayed coatings

Profilometer measurements on Fecralloy Sample (574 MPa)

Comparison between optical and profilometer measurements

Comparison between Stoney and Freund analysis LVDT jig

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Coating Measurement Using SAWs

Movie from http://www.novelengineers.com/LaWave.ppt

Non-contact measurement method using high power laser

Short (400ps) laser pulse is adsorbed by materialThermo-elastic expansion generates wide

bandwidth SAW packetsSAWs detected by piezo-wedgeVelocity used to calculate Elastic

Modulus, Poisson’s ratio, Film thickness, Porosity & Density

3060

3080

3100

3120

3140

3160

3180

3200

3220

0 20 40 60Frequency, f (MHz)

Pha

se V

eloc

ity, c

(m/s

)

Steel

3µm TiNon Steel

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Impact Excitation Apparatus

Resonant Frequencies

ContextNeed for simple measurement of coating modulusModulus can be measure of quality and integrity of coating

ScienceUse impact excitation where transducer measures the resonant frequency f.Modulus E is function of geometry and resonant frequency

Future VisionDevelop into portable easy to use apparatus for shop floor use

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Modulus against Frequency for TiN coated steel

Extrapolation back to Zero kHz gives a value for the modulus of the coating.

Intercept B = 427 GPaIntercept A = 425 GPa

Intercept C = 440 GPa

0

200

400

600

800

1000

1200

0 5 10 15 20 25 30 35 40Frequency (kHz)

Mod

ulus

E (G

Pa)

Specimen A (0.87mm substrate, 950nm coating)Specimen B (0.87mm substrate, 2280nm coating)Specimen C (0.87mm substrate, 2660nm coating)

Results from Euler- Bernoulli analysis of frequency shiftAccurate film thickness is crucial (fourth power)

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Before Wear

After Wear

Before Wear

After Wear

After Wear

Correlated and Subtracted Images

Profile from above

3D Optical Microscopy for Wear MeasurementSimilar to confocalmicroscopyHeight data combined with image dataDataset correlationReal volume measurement

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Gas Borne Particle Erosion – Stepwise Analysis

Supply tubeMixing

cha mberGas

supply

Abra sivereservoir

Nozzle tube

Spec imen

Workingdista nce

Ga s bla st erosion test

Nozzlelength

Schematic diagram of gas bla st erosion test system, ASTM G 76 (11)

75 ms-1

200 μm sandNormal incidence20 mm stand-off5 mm nozzleIncrements from 0.1 gm to 4 or 15 gm (later stages)

0 50 100 150 200 250 3000.000

0.005

0.010

0.015

0.020

Mas

s Lo

ss, g

Mass of Erodant, g

M4 M6

Erosion Damage

Area Examined

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Stepwise Erosion Large Grain WC/Co Hardmetal

8 μm

27.5 g27.5 g 33.5 g33.5 g

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Monitoring Degradation of Surfaces Due to Wear

Develop sensors that give signature that can be related to wear processesSetting up four different approaches

Electrostatic probeElectromagnetic probeChromatic aberration probe

- Reflectivity- Distance

Real time video of moving surface through linescancamera system

Booth et al, Tribology International 39 (2006) 1564–1575

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Chromatic Aberration ProbeUses optics giving enhanced chromatic aberrationDifferent wavelengths are focussed at different depthsMeasuring colour of reflected light gives measure of distance

Non-contactFast

-10

-5

0

5

10

15

0 500 1000 1500 2000 2500 3000 3500 4000Time (s)

Arm

Dis

plac

emen

t(mic

rom

etre

s)

7.86

7.87

7.88

7.89

7.9

7.91

7.92

7.93

7.94

7.95

7.96

Opt

ical

Pro

be O

utpu

t (V)

Displacement-sdOpto Probe

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New In-situ Micro-tribology Test System

A new micro-tribology test system has been designed and fabricated (within the SEM) to perform tests on a range of low friction coatings. The test system is being applied to three initial areas:1. A study of the abrasion resistance of tool materials such as WC/Co2. Examination of the tribological performance of low friction carbon based coatings3. Tribological assessment of Inorganic Fullerene Like coatings: EU project

Friction with time for micro-tribology experiment on CPxfilms from LinköpingUniversity

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Overall Friction Trend, 2010 Results – Moist Air

0 5 10 15 20 25

0.02

0.04

0.06

0.08

0.10

0.12

Fric

tion

Coe

ffici

ent

Cycles

Most Graphitic Balinit C* Balinit A Balinit DLC Alchrona TiAlN

Friction behaviour is very similar with diamond probes for all coatings testedCompare with macro tests where

TiN is ~0.6DLC is ~0.1

Why?Friction controlled by diamond probes not samplesWater present at interfaceContact size effect

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Different Material Probes – Macro vs Micro

0 5 10 15 20 250.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Balinit C* Balinit DLC* Teer Graphitic Teer MOST TecVac TiAlN

Y Ax

is T

itle

X Axis Title0 5 10 15 20 250.00

0.05

0.10

0.15

0.20

0.25

0.30

Balinit C* Balinit DLC* Teer Graphitic Teer MOST TecVac TiAlN

Fric

tion

Coe

ffici

ent

Pass Number

0 5 10 15 20 250.00

0.05

0.10

0.15

0.20

0.25

0.30

Balinit C* Balinit DLC* Teer Graphitic Teer MOST TecVac TiAlN

Fric

tion

Coe

ffici

ent

Pass Number

0 5 10 15 20 250.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0 Balinit C* Balinit DLC* Teer MOST TecVac TiAlN

Fric

tion

Coe

ffici

ent

Pass Number

0 2000 4000 6000 8000 100000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Fric

tion

Coe

ffici

ent

Time, s

Balinit C* Balinit DLC* Graphitic MOST TiAlN

0 2000 4000 6000 8000 100000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Balinit C* Balinit DLC* Graphitic MOST TiAlN

Fric

tion

Coe

ffici

ent

Time, s

Moist Air

Dry N2

200 μm diamond probe, 100 mN 2 mm steel probe, 100 mN 10 mm steel probe, 10 N,pin-on-disc

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AFM Images – TiAlN, air

TiAlN sampleGood resolutionNote polishing scratches crossing main scratch (arrowed)

Shows major mechanism is deformation

10 μm indenter 1 pass 50 mN load

10 μm indenter 1 pass 50 mN load

1 μm indenter 20 pass 100 mN load

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TiAlN Scratch Profiles (AFM)

Used SPIP to obtain average profiles from scratches (average of 50)Shows uplift at edge of scratch (particularly for 1 μm)Width of scratch is same for 1 μm and 10 μm

-10000 -5000 0 5000 10000-200

-150

-100

-50

0

50

Hei

ght,

nm

Distance, nm

1 pass 2 pass 10 pass 20 pass 50 pass

-10000 -5000 0 5000 10000-45

-40

-35

-30

-25

-20

-15

-10

-5

0

5

10

15

20

Hei

ght,

nm

Distance, nm

2 pass 10 pass 20 pass 50 pass

-10000 -5000 0 5000 10000

-150

-100

-50

0

50

Hei

ght,

nm

Distance, nm

1 μm 10 μm

50 mN 1 μm indenter 50 mN 10 μm indenter

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Help Available?

IOM3 Technology Hub on IOM3 Surface Engineering Division Board web site being developed to give guidance and access to literatureAcademic centres across UKNPL Good Practice Guide No 83, An Introduction to the MechanicalTesting of Coatings, M G Gee and N M JennettMeasurement standards in many ASTM, CEN and ISO committees

Metallic and other inorganic coatings, BS STI/33, CEN 262, ISO TC 107Ceramic coatings, BS RPI/13, CEN 184 WG5, ISO TC 206Thermal sprayed coatings, BS STI/40, CEN 240

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To Sum UpWide range of measurement methods availableRange of accessibityNeed to think about relevance of measurements to applicationsNPL is available to help