1. Toughness of HVOF – Sprayed Cermet Coatings
M. Schulze, F. Gärtner, Th. Klassen
Helmut Schmidt University, Hamburg, Germany
ITSC 2007, Beijing 14. – 1

2. Purposes
Developing a single pendulum to scratch thermal spray coatings
Exploration of Key Parameters to Evaluate Coating Performance
Practical Application to Thermally Sprayed Coatings 2

3. Investigated HVOF – Systems
Fuel
JP-5000
Kerosene
DJ 2700
Propane, Propylene,
Ethylene
Combustion Pressure
6 –10 bar
Particle Vilocity
m/s 3

4. HVOF Spraying of WC-Co 83-17
DJ 2700 / ethylene
JP-5000 /
kerosene
hardness (HV 0.3):
abrasive wear
ASTM G65 (mg / 2000 revs.)
1430 40
1281 31 4

5. HVOF Spraying of Cr3C2-NiCr
DJ 2700 / ethylene
JP-5000 /
kerosene
hardness (HV 0.3):
abrasive wear
ASTM G65 (mg / 2000 revs.):
1005
36,2
1022
41,9 5

6. Description of the Method
adjustable sample holder
goniometer with maximum indicator
pendulum
tool 6

7. Single Pendulum
longer pendulum length required to ensure larger amounts of affected volume and measurable energies
h = depth of the track, 100 µm
L1 = length of pendulum, 677 mm
L2 = length of pendulum, 250 mm
s1 = length of the track
s2 = length of the track
basic condition:
small depth ! h L1 L2 s2 s1 7

8. Tool longer durability of the tool
alternating compressive and tensile stress
longer durability of the tool 8

9. Measurable Effects Existence of cracks Appearance of crack network
Energy 9

10. Application for Cermets
materials
WC-Co
WC-Co
WC-Co-Cr
Cr3C2-NiCr
spray systems
DJ 2700
JP 5000 10

11. Criterions for assessing scratch morphologies
A/B = lateral cracks / track gage A B
crack propagation, crack network
delamination
s = crack free zone s 11

12. Scratch Depth and Velocity
WC-Co 83-17
DJ 2700
vR = 3,8 m/s
Depth = 150 µm
vR = 2,9 m/s
Depth = 100 µm
no influence on crack formation 12

13. Effect of HVOF Spray Conditions on WC - Co 83-17 CoatingsB
DJ 2700 s A B
JP 5000 13

14. Evaluation of Cermet Coatings
track assessment of different coatings
Material
System
Entry Length to Crack Formation
[µm]
Ratio of Lateral Cracks
[%]
Chunking
Delamination
WC-Co 83-17
DJ 2700
300 76 X
JP 5000
1000 50
WC-Co-Cr
700 57 21
Cr3C2-NiCr
75-25
520 66
610 69 14

15. Running-in Length 15

16. Ratio of Lateral Cracks16

17. Determination of Specific Deformation Energy
(50 J)
slopes of deformation energy for different scratch depths 17

18. Deformation Energy of Cermets
influence of spray conditions on plastic deformation:
variation within 20 % 18

19. Coating Toughness and Wear
more plastic deformation, less brittle behavior
better wear resistance 19

20. Conclusion
material parameters for single pendulum scratch tests have been defined
the specific deformation energy is used for evaluation of
thermal spray coatings
criteria for microscopical evaluation have been developed
specific deformation energies can be used for coating assessment
coating toughness can be correlated with wear resistance 20

21. Additional slides 21

22. Deformation energy versus depth22

23. HVOF Spraying of WC-Co 83-17
DJ 2700 / ethylene
JP-5000 /
kerosene
hardness (HV 0.3):
abrasive wear
ASTM G65 (mg / 2000 revs.)
1430 40
1281 31 23

24. HVOF Spraying of Cr3C2-NiCr
DJ 2700 / ethylene
JP-5000 /
kerosene
hardness (HV 0.3):
abrasive wear
ASTM G65 (mg / 2000 revs.):
1005
36,2
1022
41,9 24