Transcript ADVANCED PARTICLE CHARACTERIZATION FOR IMPROVED UNDERSTANDING OF SPRAY COATING QUALITY E. Pirard Univ. Liège (Belgium) F.

ADVANCED PARTICLE
CHARACTERIZATION FOR
IMPROVED UNDERSTANDING OF
SPRAY COATING QUALITY
E. Pirard
Univ. Liège (Belgium)
F. Campana, J-P Janssen
Advanced Coating, Liège (Belgium)
Introduction
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The interaction between the gas and the individual
particle plays a key role
A better understanding of the way individual particles
are affected, will allow for developing more accurate
powder specifications
Existing norms provide only limited insight into
particle characteristics
Use innovative single particle digital imaging and
analysis to access pertinent information
ITSC Seattle 15-18 May 2006
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Metal Powders
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High velocity oxy-fuel (HVOF) spray coatings with four
(Cr3C2-NiCr 75/25) comparable powders :
Supplier
Size Range [µm]
Flowability 50g [sec.]
App. density [g/cm3]
Carbon (%)
Manuf. Process
A
B
Sulzer
Metco
[-45+15]
N.A.
N.A.
9,64
A/S
Sulzer
Metco
[-45+15]
18,26
3,67
9,48
A/S/P.D.
C
D
Sylvania
[-53+10]
26
3,6
9,11
A/S/P.D.
Deloro
Stellite
[-53+10]
23
3,62
9,45
A/S/P.D.
supplier data
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Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Standard Characterization
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ISO 3923/2: Determination of apparent density
Part 2: Scott volumeter method
Density
A
B
C
D
Test 1
2,77
3,82
3,79
3,84
Test 2
2,75
3,87
3,79
3,8
Test 3
2,76
3,82
3,78
3,78
m
ITSC Seattle 15-18 May 2006
2,76 3,84 3,79 3,81
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Standard Characterization
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ISO 4490 : Determination of flow time by means of a
calibrated funnel (Hall flowmeter)
Flow
A
B
C
D
Test 1
29,59
22,15
29,29
21,78
Test 2
29,73
22,23
29,37
21,18
Test 3
29,66
22,28
28,75
21,79
m
Suppl. data
ITSC Seattle 15-18 May 2006
29,66 22,22 29,14 21,58
N.A.
18,26
26
23
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Digital Image Analysis
of
Individual Particles
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Three essential steps requiring dedicated solutions :
Powder Dispersion
Particle Analysis
Particle Imaging
ITSC Seattle 15-18 May 2006
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Powder Dispersion
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Patented vacuum disperser
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Cylindrical chamber
Pinhole with plastic membrane
Settling onto circular glass slide
Advantages
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Occhio Instruments
VDD270
ITSC Seattle 15-18 May 2006
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Perfect dispersion (1:500)
No breakage / deformation of particles
Controlled (symmetrical) segregation
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Particle Imaging
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Automated Digital Microscopy
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Advantages
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Occhio Instruments
ALPAGA 500 nano
Diascopic illumination @ 439nm (LED)
Superzoom telecentric lens
Hi-resolution digital video
Fully motorized glass plate
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15 µm
Typ. 10.000 particles/min
Controlled particle position and velocity
Dynamic range : 0,5 µm – 200 µm
a 15 µm particle is typically 800 pixels
ITSC Seattle 15-18 May 2006
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Particle Analysis
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Accurate estimation of a “sieving diameter”
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ISO TC24SC4 : Sizing by methods other than sieving
Application oriented shape characterization
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Computation of a wear index :
W
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64,14
65,71
82,55
Computation of a satellity index :
RND 99.6 %
EL 0.78
ITSC Seattle 15-18 May 2006
46,18
97.2 %
18.64
66.7 %
5.65
61.6 %
17.51
50.9 %
12.67
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Results on
Cr3C2-NiCr 75/25 particles
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Size Distributions
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By Number of by Volume
Sub-sieve analysis capability
ITSC Seattle 15-18 May 2006
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Results
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Morphostatistics
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Quality control statistics
Discriminant statistics
DIN
[µm]
W [%]
Roundness
El [%]
Elongation
A
33,66
65,67
25,68
B
33,35
74,83
21,70
C
28,97
58,29
21,70
D
30,02
79,00
16,10
Mean values
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Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Results
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Coating Deposition Efficiency
A1
A2
D
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Fl
Th/r
Th/p/Fl
g/min
µm
µm/(g/min)
Mean
Q
g/(m²x
0.1mm)
1.184
39
11.8
0,3
Std Dev
70
5.4
1.8
0,03
Mean
1.252
38.1
11.4
0,3
Std Dev
244
2.1
1.6
0,05
Mean
Std Dev
1.381
142
45.5
7.3
12.2
1.3
0,27
0,05
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Results
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Coating Deposition Efficiency
Th
[µm]
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Porosity
Hardness
[HV0,3]
Mean Min. Max. Mean Min. Max.
A
183
2,6% 2,1% 3,8% 1041 845 1255
D
159
1,1% 0,4% 1,4% 971
856 1173
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Discussion & Conclusions
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Image analysis provides very accurate size distributions
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Perfect correlation with sieves
Number weighted distributions are unique
(e.g. A contains 90% <15µm)
Image analysis provides unique shape information that
correlates perfectly with flowability tests
A
B
C
D
[µm]
[%]
Roundness
Elongation
33,66
33,35
28,97
30,02
65,67
74,83
58,29
79,00
25,68
21,70
21,70
16,10
ITSC Seattle 15-18 May 2006
W
El
DIN
[%]
Scott
Hall
2,76
3,84
3,79
3,81
29,66
22,22
29,14
21,58
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )
Perspectives
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Image analysis offers a unique insight into metal powder
properties (direct measurement !).
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It opens the way to a better understanding of coating
qualities with respect to powder properties
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This new analytical technology allows to optimize powder
specifications.
ITSC Seattle 15-18 May 2006
Pirard (Univ. Liège), Campana & Janssen (Advanced Coating )