cost effective testing of coatings - institute of … testing.pdf3100 3120 3140 3160 3180 3200 3220...

Cost Effective Testing of Coatings

Mark Gee

National Physical Laboratory

9th March 2010

Monday, 15 March 2010

2

NPL Today

•World leading National Measurement Institute•600+ specialists in Measurement Science•State-of-the-art standards facilities

•The heart of the UK’s National Measurement System to support business and society

•Experts in Knowledge Transfer

To deliver the highest economic and social impact as a world-leading National Measurement Institute through excellent, responsive science and knowledge services


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The growing demand for better measurements

You and I

Regulators

Doctors

Science

Industry

Communications

Environment

Healthcare

Food

Health & safety

Transport

Metrology influences, drives and underpins much of what we do and experience in our everyday lives, though often unseen. Industry, trade, regulation, legislation, quality of life, science and innovation all rely on metrology

It is estimated that in Europe today we

measure and weigh at a cost equivalent to

2-7% of GDP


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What do we do Develop & disseminate UK’s measurement standards, ensure they are internationally accepted

Multidisciplinary R&D and technical services for public and private sector

Knowledge transfer, and advice between industry government and academia


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Our Technical BreadthOur Technical Breadth Multidisciplinary R&D and technical services for public and private sector

• Photometry/Colour • Pressure• RF/Microwaves• Radiation Dosimetry• Radioactivity• Radiometry• Scientific Software• Sensory metrology• Statistics• Surface analysis• Thermal measurements• Time & Frequency• Electrical Standards

• Acoustics• Advanced Materials• Air Quality • Biometrics• Biotechnology• Corrosion• Dimensional metrology• Environmental measurement• Lasers• Mass and force• Micro/Nanometrology• Neutron measurements • Photonics


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NPL Materials team

• 100 scientists, engineers and technicians

• Expertise and facilities in materials measurements

• Develop new measurement techniques

• Adapt existing techniques to new materials

• Close to industry– 118 companies on Industrial Advisory

Groups


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Materials Team

Thermal & ElectrochemistryThermal Performance of Materials & StructuresThermal Properties of Structures, Dynamic Thermal EvaluationElectrochemistryEnvironment Induced Cracking (EIC), Fuel cells, Photovoltaics, Nanoscale EC

Bio, Polymeric & Composite MaterialsPolymeric MaterialsMicro-processing and reduced length scale propertiesCompositesSHM, Nanocomposites, Complex geometries & multiaxial propertiesBiomaterialsCellular interactions with materials and fluid flow through complex porous structures

Nano- & Multifunctional MaterialsNanomaterialsmaterial characterisation, micro-fluidic studies, modelling Multifunctional MaterialsMultiphysics coupling in Multiferroic/functional materials (includes magnetic and organic electronics)

Advanced Engineered MaterialsInnovative Metals EngineeringLiquid Metal Processing, Residual Stress and Strain, High Temperature DegradationPerformance of Engineered SurfacesNano Mechanics, Tribology, Powder Route Materials (PRM), Microscopy

Electronics & ModellingMaterials ModellingThermodynamics (MTDATA), Structural Health Monitoring, FE, FD & Genetic ModellingElectronics Interconnectcircuit cleanness (SIR, SEC), solder reliability, component mounting


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Measurement – Why do we do it?Reasons• Provide information for materials development (can we make it)• Provide information on likely performance (will it work)• Provide information for input into modelling (can we predict if it

will work)

Other factors• Cost of testing versus field trials• Need for simple and quick QC tests• Need for high quality data for modelling• Need for the right information for production• As close to shop floor as possible• Increasing range of coatings• Increasing possibility of combining different functionality through

nanostructuring (layered, particulate etc)


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Coatings Measurement• Wide range of measurement methods available

– Adhesion, thickness, composition, hardness, mechanical properties, residual stress, wear, friction

• Aim is to make measurements simpler, more relevant, cheaper, more robust

• Guidance available– NPL Good Practice Guide No 83, An Introduction to the

Mechanical Testing of Coatings, M G Gee and N M Jennett• Measurement standards in many ASTM, CEN and

ISO committees– Metallic and other inorganic coatings, BS STI/33, CEN 262,

ISO TC 107– Ceramic coatings, BS RPI/13, CEN 184 WG5, ISO TC 206– Thermal sprayed coatings, BS STI/40, CEN 240


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Video

Acoustic emission

Strain gauge

Load cell

Rollers

Motor drive

Displacement Sensor

Bend Testing for Coating Integrity TestingContext• Need to provide

information on integrity of coatings under mechanical loading

Science• Use instrumented bend

testing • Acoustic emission• Video to detect crackingFuture Vision• Is being taken forward

into work to provide simple test for near shop floor environment

• Proposal 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 tube• Compare performance

of oxidised and unoxidised tube

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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Coupon Bending for Residual Stress Measurement

• Residual stress from thermal expansion mismatch and processing effects

• For thin coatings Stoney formula; thick coatings more complex formula

• Methods for measurement– Profilometry

• Flexus– Optical microscope– LVDT


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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

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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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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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 material

– Thermo-elastic expansion generates wide bandwidth SAW packets

– SAWs detected by piezo-wedge– Velocity 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

Context• Need for simple measurement

of coating modulus• Modulus can be measure of

quality and integrity of coatingScience• Use impact excitation where

transducer measures the resonant frequency f.

• Modulus E is function of geometry and resonant frequency

Future Vision• Develop into portable easy to

use apparatus for shop floor use


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Modulus against Frequency for TiN coated steelExtrapolation 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 Measurement• Similar to confocal

microscopy• Height data combined

with image data• Dataset correlation• Real volume

measurement


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Gas Borne Particle Erosion – Stepwise Analysis

Supply tubeMixing

chamber

Gassupply

Abrasivereser voir

Nozzle tube

Specimen

Workingdistance

Gas blast erosion test

Nozzlelength

Schematic diagram of gas blast 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 processes

• Setting up four different approaches– Electrostatic probe– Electromagnetic probe– Chromatic aberration probe

• Reflectivity• Distance

– Real time video of moving surface through linescan camera system

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


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Chromatic Aberration Probe• Uses optics giving enhanced

chromatic aberration• Different wavelengths are focussed

at different depths• Measuring colour of reflected light

gives measure of distance– Non-contact– Fast

-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 CPx films from Linköping University


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To Sum Up

• Wide range of measurement methods available

• Range of accessibity• Need to think about relevance of

measurements to applications• NPL is available to help

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