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19.04.2012
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Nova W
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NOVA WERKE AG
Dr. Mousab Hadad
Applied Tribology
Empa Akademie, Dübendorf, 17. April 2012
The Tribological Responses Of Coatings
Subjected To Severe Conditions
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Content
1. Company profile 2012
2. Laboratory @ Nova Swiss and facilities
3. The tribological responses of coatings subjected to severe conditions
3.1 Theoretical introduction
3.2 objective 3.3 Theoretical introduction3.4 Results & analysis
4. Conclusion
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1. Company Profile 2012
Personnel: approx. 140 EmployeesProduction Area: ca. 10‘000m2
Management System: ISO/TS 16949 / ISO 9001/14001/18001ERP / CAD: iFAS V4 / Pro-E „Wildfire“
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1. Company Profile
Engine Components & High Pressure Technology
Surface Technology & Valve Service
1.1. Core of activities
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Coating Systems Available:
• Flame – Spraying (FS)
• Wire-Arc – Spraying (WAS)
• Plasma - Spraying in Atmosphere (APS)
• High Velocity Oxy/Fuel Flame-Spraying (HVOF)
Coating Materials (mainly):
• Metals, Ceramics, and Hardmetals
Typical Applications:
• Wear resistance (Abrasion, Erosion, Cavitation,
Fretting, etc.)
• Thermal and Electrical Barrier Coatings (TBCs,
Alumina), etc.
1.2. Surface and Coating Technology
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• Laboratory of Tribology (wear and friction testing)
• Laboratory Metallography
• Mechanical and adhesion testing of coatings
• Consultancy
I. Development of thermal spray coating applications
II. Tribology (wear and friction)
III. Metallographic characterizations
IV. Mechanical and adhesion testing of coatings
2. Laboratory @ Nova Swiss and facilities
http://www.novaswiss.ch/news-n13-sE.html
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2.1. Facilities
90°
HT up to 700°C
•Heater
2000 N
Up to 300°C
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2.1. Facilities
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2.1. Facilities
1. Shear testing device according EN 15340
2. Stereo microscope
3. Light microscope
4. Profile and roughness measurements (mechanical contact by stylus)
5. Different Hardness measurements (Vickers and Rockwell)
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• to investigate the composite coating (ductile matrix with
brittle hard particles) behavior when it is subjected to
different solid particle erosion tests varying the loading
modes and impingement angles.
• to establish a proper evaluation process of wear rates
3. The tribological responses of coatings subjected to severe conditions
3.1 Objectives
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3.2.1. Erosion wear by plastic deformation
mer : mass of erodent particle
Wv : the volume loss due to wear
U : Particle velocity
H: Material hardness
K : dimensionless wear coefficient
ρ : mass density wear material
* Hutchings 1992
*2
.2
.
H
Umw er
v =
==
2
..
striking particles erosive of mass
removed material of mass 2U
H
KE
ρ
Engineering Tribology (3rd Edition). Gwidon W. Stachowiak and Andrew W. Batchelor. Butterworth-Heinemann, Boston, 2001-Chapter 11
)(... 2
1 αρ
fH
UKE =
3. The tribological responses of coatings subjected to severe conditions
3.2. Theoretical introduction to the fundamental models of wear process
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3.2.2. Erosion wear by brittle fracture (semi-empirical)
r : radius of particle
U : Particle velocity
σ : density of erosive particle in time unite
H: Material hardness
Kc : the fracture toughness of material
ρ : mass density of particle
E: erosion rate (dimensionless)
* Hutchings 1992
*
3.1
1.06.0
4.20.7.
. . r cK
HU
E σ
ρ∝
* As for abrasion, a correlation with function of H and KIC.(this hold only for erodent particles which hard enough to cause a lateral fracture)
3.2. Theoretical introduction to the fundamental models of wear process
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• Parameters selected in erosion wear models (Meng 1995)
H.C. Meng, K.C. Ludema, Wear models and predictive equations: their form and content, Wear 181-183 (1995) 443-457
Engineering Tribology (2nd Edition). Gwidon W. Stachowiak and Andrew W. Batchelor. Butterworth-Heinemann, Boston, 2001-740pp
G.L. Sheldon and I. Finnie, On the ductile behaviour of nominally brittle materials during erosive cutting, transition ASME, Vol 88B, 1966, pp 387-392
G. L. SHELDON and ASHOK KANHERE, AN INVESTIGATION OF IMPINGEMENT EROSION USING SINGLE PARTICLES, Wear, Lausanne 1972- pp. 195-209
3.2. Theoretical introduction to the fundamental models of wear process
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3.2. Theoretical introduction to the fundamental models of wear process
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3.3. Materials and experimental procedure
WC-Co thermally sprayed coating on a steel substrate
5 µµµµm
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3.3. Materials and experimental procedure
TestErodent Erodent size
Flow rate (water)
Flow rate (erodent)
VelocityStand off distance
Nozzle diameter
PressureExposure
time
material µm l/min g/min m/s mm mm bar min
Slurry erosion Al2O3 45-75 13.6 9.52 147 100 1.4 250 38
Dry erosion Al2O3 500-1000 378 12 70 7.5 3.5 25
Slurry erosion
Nozzle
Sand
Liquid jet
CoatingDegree pivot30°, 60°and 90°
90°
30°
Mask
Coating
Dry erosion
Hadad_Wear 2007
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30°impingement angle
90°impingement angle
Sa
mp
le
3.3. Materials and experimental procedure
90°
30°
The average particle size 750 µm
Mask
Coating
Mask shadow
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3.4. Results of solid particle erosion tests
0
2
4
Mass l
oss [
g]
Coating combinations
Dry erosion results at 30°and 90°
Impact angle at 30° Impact angle at 90°
Coating 1 Coating 2
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3.4. Results of solid particle erosion tests
Removal volume fraction= volume of single particle / volume of removed materials: 5-15Assumption:
Average particle diameter is 750 um, volume assumed 0.22 mm3 (spherical shape)
0
2
4
6
VL
os
s/ p
art
icle
im
pact
[mm
3/im
pact]
x 1
0-2
Coating combinations
Dry erosion results at 30°and 90°
Impact angle at 30° Impact angle at 90°
Coating 1 Coating 1
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3.4. Results of solid particle erosion tests
Removal volume fraction= volume of single particle / volume of removed materials: 5-15Assumption:
Average particle diameter is 750 um, volume assumed 0.22 mm3 (spherical shape)
0
2
4
6
VL
os
s/ p
art
icle
im
pact
[mm
3/im
pact]
x 1
0-2
Coating combinations
Dry erosion results at 30°and 90°
Impact angle at 30° Impact angle at 90° Wear at 30° considering the same particle numbers at 90°
Coating 1 Coating 2
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3.4. Results of solid particle erosion tests
Removal volume fraction= volume of single particle / volume of removed materials: 5-15Assumption:
Average particle diameter is 750 um, volume assumed 0.22 mm3 (spherical shape)
0
2
4
6
VL
os
s/ p
art
icle
im
pact
[mm
3/im
pact]
x 1
0-2
Coating combinations
Dry erosion results at 30°and 90°
Impact angle at 90°
Wear at 30° considering the same particle numbers at 90°
Predicted (P size = 500 um)
Predicted (P size = 750 um)
Predicted (P size = 1000 um)
Coating 1 Coating 2
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3.4. Results of solid particle erosion tests
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0
5
10
15
20
25
VL
os
s/ p
art
icle
im
pact
[ µµ µµm
3/im
pact]
Coating combinations
Liquid with solid particle impingement erosion results at 30°and 90°
Impact angle at 90° Impact angle at 30°
Coating 1 Coating 2
3.4. Results of liquid with solid particle erosion
Assumption:
Average particle diameter is 60 um, volume assumed 113’000 µµµµm3 (spherical shape)
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3.4. Results of liquid with solid particle erosion
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Nozzle
Sand
Liquid jet
CoatingDegree pivot
30°, 60°and 90°
90°
30°
Mask
Coating
3.5. Results Analysis
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Nozzle
Sand
Liquid jet
Coating Degree pivot
30°, 60°and 90°
90°
30°
Mask
Coating
3.5. Results Analysis: wear mechanisms
25 µm25 µm
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4. Conclusion
1. The difference in coating behaviors (ductile/ brittle) subjected to erosion was
mainly due to tribo-system and wear mechanism as a major factor. The
mechanical properties of materials showed a minor influence.
2. The difference in wear mechanisms between dry and slurry erosion was
mainly attributed to particle speed and size.
3. In the slurry erosion, the repetitive particle with water impacts results in
eroding the metallic matrix (Co) leading to pull off the WC hard grains.
4. In dry erosion, the cross-sections of coating (WC–Co) showed cracks
propagating parallel to the interface between the coating and the substrate
and they generally tend to propagate through the splats and subsequent
spallation of flakes by crack fatigue.
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Coating behaviours subjected to abrasion at 700 °C
Hard face coatings A and B
Ring: 100 Cr 6
Speed: 1 m/s
Herzian pressure: 150 MPa
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Thank you for your attention!www.novaswiss.ch
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