acoustic emission monitoring of thermal spray

8/7/2019 Acoustic Emission Monitoring of Thermal Spray

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Application of acoustic emission for monitoringApplication of acoustic emission for monitoring

the HVOF thermal spraying processthe HVOF thermal spraying process

N. H. Faisal, J. A. Steel, R. Ahmed, R. L. Reuben, G. Heaton-. ,

Edinburgh, UKEmail: [email protected]

B. AllcockMonitor Coatings Ltd.

Tyne & Wear, UK

EWGAE, 21st September 2006, Cardiff, UK



Presentation StructurePresentation Structure

•• IntroductionIntroduction–– What is HVOF Thermal Spray Coatings / Applications?What is HVOF Thermal Spray Coatings / Applications?

–– Why AE Monitoring during Thermal Spraying?Why AE Monitoring during Thermal Spraying?

–– Quality Control issues in Thermal Spray CoatingsQuality Control issues in Thermal Spray Coatings

•• Experimental Systems and TechniquesExperimental Systems and Techniques

•• ResultsResults–– AE Signal CharacteristicsAE Signal Characteristics

Bio-medical/Knee, Hip, Elbow joints

Aerospace/Turbine

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Bio-medical/Knee, Hip, Elbow

–– eve opment o nemat c o e o art c e mpacteve opment o nemat c o e o art c e mpact

––Influence of Continuous MultiInfluence of Continuous Multi--layer Thermal Sprayinglayer Thermal Spraying

•• Summary, Conclusions and Future WorkSummary, Conclusions and Future WorkElectronics/Heat sink

Thermal Spray: Industries / ApplicationsThermal Spray: Industries / Applications

www.t wi .c o.uk

k a e

r t .c om

HVOF Spray gun Plasma Spray gunwww.moni t or c oa t i ngs .c o.uk

www.moni t or c oa t i ngs .c o.uk



HVOF Thermal Spray (TS) CoatingsHVOF Thermal Spray (TS) Coatings

What is HVOF (High Velocity Oxygen-Fuel) Thermal Spraying process

Coating

substrateHVOF Thermal

Spraying system

Splat cooling rate:

100-600K/ µs

Powders velocity:

600-800m/s

Flame tempe:

3000-5000˚C

Gas velocity:

1500-2000m/sParticle Temp:

1500-2000˚CTAFA JP-5000

Monitor Coatings Ltd. UK

HVOF Coating chamber

Spray spot

~ 9-12mm

HVOF nozzle/gun

AE monitoring system

Single WC-10Co-4Cr particle splat

WC-10Co-4Cr Powders

After spraying/Partially melted

Noise level in coating chamber ~

123dB ~ Jet-Engine take-off noise

•• Particle impactParticle impact

(Kinetic energy / Strain energy released)(Kinetic energy / Strain energy released)

•• Thermal mismatch, Cracks in layersThermal mismatch, Cracks in layers

•• Coating chamber reverberation (noise)Coating chamber reverberation (noise)

Why AE monitoring during TS?Why AE monitoring during TS?

•• It addresses core technological issues:It addresses core technological issues:Quantifies the partially melted powder particleQuantifies the partially melted powder particlelanding behaviour & phase changes duringlanding behaviour & phase changes duringspraying & cooling processspraying & cooling process –– Fundamental toFundamental tocoatings strength determinationcoatings strength determination

•• MonitorsMonitors quality during the coating formationquality during the coating formation

•• AddedAdded advantageadvantage over existing quality controlover existing quality control

techniquestechniques



Existing Off Existing Off--line Techniquesline Techniques ((postpost--spraying processspraying process))

e.g., Mechanical Testing procedures: It Requires

‘TEST COUPONS’ (e.g. for Bending, Indentation, Tensile,

Adhesion, Fatigue, Wear, Thermal Cycling tests)

Existing OnExisting On--line Techniques (line Techniques (postpost--spraying processspraying process))

Quality Control issues in TS CoatingsQuality Control issues in TS Coatings

Bending test

There is no ‘on-line’ coatings quality monitoring (i.e., DURINGSPRAYING) available which can quantify the splat landing

behaviour and which can measure the cohesive & adhesive

strengths on ACTUAL COMPONENTS

e.g., on- es ruc ve es ng proce ures: trason c,

Radiographic, Electromagnetic, Liquid penetrant, Magnetic

particle, 4-point bending test + AE, Indentation test + AE



Thermal Spraying / AE measurementThermal Spraying / AE measurement

Pre-amplifier: PAC-1220A

Pre-amp at 40/60 dB,

Gain at SCU = 0 dB

PAC, Micro-80D: Broadband PZT

sensor (0.1-1.0 MHz), Rf = 332kHz

12 bit NI, PCI-6115 DAQ, and AE

4-channel system; Sampling rate

2.5MHz/2 sec

CPU, Computer & AE system

HVOF

System

TAFA

JP-5000

Slit/mask

HVOFnozzle/gun

(A)

Using

slit

(B)

Coating chamber

SubstrateHolder

HVOF System,Coating chamberCoating substrateMasking-sheet (slits)

Masking-sheet/Substrate

set-up

Masking-sheet-substrate-

sample holder set-up

Withoutslit



Experimental matrix & MaskingExperimental matrix & Masking--sheet (slit)sheet (slit)

HVOF

Thermal

Spray

Parameters

Pressure level-P1 Pressure level-P2

O/F ratio = 1.16 (P1); Oxygen flow rate, 1950

scfh; Powder feed gas, Nitrogen (21 scfh); Fuel

flow rate, 6 gallon/min (kerosene); Powder feed

rate, 80 g/min

O/F ratio = 1.21 (P2); Oxygen flow rate, 1950

scfh; Powder feed gas, Nitrogen (21 scfh);

Fuel flow rate, 4.5 gallon/min (kerosene);

Powder feed rate, 80 g/min

Slit no. and

width

A

(3mm)

B

(2mm)

C

(1mm)

D

(0.5mm)

A

(3mm)

B

(2mm)

C

(1mm)

D

(0.5mm)

Gun

scanning

speed

(mm/sec.)

A: 3 mm

27 mm

Gun motion Coating Substrate (Mild-Steel)

Masking-sheet (Mild-Steel)

500 1 1 1 1 1 1 1 1

750 1 1 1 1 1 1 1 1

1000 1 -- -- -- 1 -- -- --

10mm



AE Signal Characteristics (Background noise)

I. AE signal during flame spraying only beside slit-substrate without powder

II. AE signal during flame and powder spraying beside slit-substrate

Masking-sheet (slits)

Coating substrate

Coating substrate

0 0.5 1 1.5 2-0.2

-0.1

0

0.1

0.2

Time (s)

mp

ure

nopowder

beside

sample010000.bin

0.2

powderbeside

sample010000.bin

0 5 10 15

x 105

0

2

4

6

8x 10

-8 Frequency domain:no powder beside sample010000.bin

Frequency (Hz)

Power spectral density

4x 10

-8 Frequency domain:powder beside sample010000.bin

Coating chamber

Noise level

5, 50, 100, 140kHz

III. AE signal during flame spraying only on substrate without powder

Coating substrate

Masking-sheet (slits)0 0.5 1 1.5 2

-0.2

-0.1

0

0.1

Time (s)

Ampliture (V)

0 0.5 1 1.5 2-0.2

-0.1

0

0.1

0.2

Time (s)

mp

ure

flamepass010000.bin

0 5 10 15

x 105

0

1

2

3

Frequency (Hz)


0 5 10 15

x 105

0

1

2

3

4x 10

-8 Frequency domain:flame pass010000.bin

Frequency (Hz)


5, 50, 100, 140kHz

5, 50, 100, 140kHz

Coating chamber

Noise level

Coating chamber

Noise level



IV. AE signal during full spraying (both flame and powder) at standard spraying pressure P-1

AE Signal Characteristics

Masking-sheet (slit A),

3mm width, 10mm height

Substrate:

Coatings through slit-A

Gun speed: 500mm/sec

500mm

No. of Slits: 14

1.5x 10

-7 Frequency domain: hvof12010000.bin

SNR ~ 3 to 4

0 5 10 15

x 105

0

0.5

1

Frequency (Hz)

Powe

r spectral density

5-100kHz (BNG)

100-200kHz300-400kHz

550-650kHz

750-850kHz

BGN



Development of Kinematic ModelDevelopment of Kinematic Model (particle impact)(particle impact)

Phase difference & Area distribution

(3mm slit, 250mm/sec)

10

20

30

40

50

60

70

Area [mm2̂

]

area(theta)

area(delta)

effective area

Effective Spraying Area = (1/2) . [R2 {2 (θ

-δ

) - (Sin 2θ

-Sin 2δ

)}] = Curve3Gun Speed, Vg

D’D

Slit width, y

D’D

Curve2 (Edge-2)

Curve1 (Edge-1)

Curve3 = [Curve1-Curve2]

Slit centre

x1x1 x2x2

EdgeEdge--11 EdgeEdge--22

0

0 0.01 0.02 0.03 0.04 0.05 0.06

Time [sec]

Area distribution (3mm slit, 250mm/sec gun

speed)

0

10

20

30

40

50

0 0.01 0.02 0.03 0.04 0.05 0.06

time [sec]

Area

area

x1x1 x2x2

x1x1 x2x2

Curve3 = effectivespraying area



Kinematic Model of Particle ImpactKinematic Model of Particle Impact

(a) (b) (c)

Time length = 0.052sec

-

0

0.5

1

Ampliture (V)

hvof11010000.bin

K.E of powder particles making impact through effective area is, E = [(1/2).M.V.V];

E = (1/2) . [N. mp].(R.R/2). [2 (θ-δ) – (Sin 2θ-Sin 2δ)] .V.Vwhere V is the velocity of sprayed particle

SNR ~ 3 to 4

100

150

200

250

300

350

400

450

nergy [kg.m^2/s^2] per

slit

Slit-A: 3mm

Slit-B: 2mm

Slit-C: 1mm

Slit-D: 0.5mm

2000

3000

4000

5000

6000

tal AE energy [V.s] per slit

Slit-A: 3mm

Slit-B: 2mm

Slit-C: 1mm

Slit-D: 0.5mm

Experimental Area Theoretical Area

0.00 0.01 0.02 0.03 0.04 0.05 0.060

5000

10000

15000

20000

Theoretical

Kinetic Energy distribution [Kg.m

2.s

-2]

Time of spray gun transversing the slit [seconds]

KE (Slit width: 3mm; Gun Speed: 250mm/sec )

0.05 0.1 0.15

-0.4

-0.2

0

0.2

0.4

0.6

Time (s)

Ampliture (V)

0 0.5 1 1.5 2-1

.

Time (s)

3mm slit width, 250mm/sec gun speed0 250 500 750 10000

50

Theoretical

HVOF gun transverse speed [mm/sec]

0 250 500 750 10000

Experimen

HVOF gun transverse speed [mm/sec]

Experimental Theoretical

Smoothed signal



AE Monitoring During Multilayer ThermalAE Monitoring During Multilayer Thermal

Spraying (without masking slit)Spraying (without masking slit) Coating builds-up

(cross-section)

Centre-line

Theoreticalspray-spot

~ 9-12mm

Actual

Transverse Gun Speed

AE system

www.t h e r ma l s pr a y.ws

spray-spot

~ 18mm

Actual spray-spot is greater

than theoretical spray-spotdue to fanning of spray



Influence of Continuous MultilayerInfluence of Continuous Multilayer

Thermal SprayingThermal Spraying

0.00004

0.00006

0.00008

0.00010

0.00012

0.00014

0.00016

energy (a.u.) pe

r unit time

AE energy (a.u.)

Gun Speed

200mm/sec

AE sensor location (centre-backside)

AE sensor location

0 50 100 150 200 250 3000.00000

0.00002A

No. of data files

[time for 1 data file = 0.004 sec]

0 1 2 3

x 106

0

1

2

3

4

5x 10

-7 Frequency domain: A1010000.sgl

Frequency (Hz )

Power spectra

l density

0 1 2 3 4

x 10-3

-1

-0.5

0

0.5

1

Time (s)

Ampliture

(V)

A1010000.sgl

Chamber Noise ~ 0.15V

0 1 2 3 4

x 10-3

-1

-0.5

0

0.5

1

Time (s)

Ampliture (V)

A1010025.sgl

0 1 2 3

x 106

0

2

4

6x 10

-7 Frequency domain: A1010025.sgl

Frequency (Hz)

Power spectral densitySNR ~ 4 Frequency

340, 590 & 800kHz



Summary

SprAE Monitoring Block DiagramSprAE Monitoring Block Diagram(Open loop system)(Open loop system)

Thermal Spray particle impact

Multilayer Spraying Spraying through slits

AE SignalAE SignalThermal Spraying system

AE Energy

distribution

Thermal SprayProcess Parameter

Monitoring

Amplitude, Frequency,

Event (N), Energy (E),Event duration (T)

Event rate (N/T),

Energy rate (E/T)

SprAE monitoring system



ConclusionsConclusions

•• AE monitoring system developed; HighAE monitoring system developed; High SignalSignal--toto--Noise Ratio (3Noise Ratio (3--4)4) hashasbeen measured during HVOFbeen measured during HVOF

•• As gun speed increases values of As gun speed increases values of AE parameters fallAE parameters fall through slitsthrough slits

•• AE energy increasesAE energy increases as the number of layers increaseas the number of layers increase

•• Kinematic model has been developedKinematic model has been developed

•• Other techniques:Other techniques: PlasmaPlasma,, DetonationDetonation andand Cold spray coating / AECold spray coating / AE

•• Future experimentationFuture experimentation (DOE / Taguchi’s technique) / (DOE / Taguchi’s technique) / AEAE

•• Development of post spraying AE testsDevelopment of post spraying AE tests / Identifying coating/ Identifying coatingstrengthsstrengths

•• Development of Control processDevelopment of Control process during Thermal Spraying / during Thermal Spraying / AEAE

•• Computational fluid dynamics (CFD)Computational fluid dynamics (CFD) analysis / AE signalanalysis / AE signaldistributiondistribution

•• Thermal Spray NThermal Spray Nozzle wear rate monitoringozzle wear rate monitoring using AEusing AE

Future workFuture work

Thermal Spraying system

SprAE monitoringsystem

SprAE control system

Close loop system

?



Thanks!Thanks!Tyne & Wear Castle Edinburgh Castle

Any Questions Please?Any Questions Please?

Cardiff Castle

acoustic emission monitoring of thermal spray

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