1. Effects of Wire-Electro Discharge Machining Process on Surface Integrity of WC-10Co Alloy
Nilüfer Orhon*, Erdem Şireli
2nd Surface Treatment Symposium
June 25-27, 2014, Istanbul-Turkey

2. Outline Cemented Carbides Forming Methods
Wire-Electro Discharge Machining (W-EDM)
Pros and cons of W-EDM
Chemical Vapor Deposition
Experimental
Surface Characterization
Mechanical Tests
Conclusions

3. Cemented Carbides WC-Co Other Carbides; TiC, TaC, NbC, VC, Cr3C2
HARDNESS
&
TOUGHNESS WC Co Co
Other Carbides WC
WC-Co
Other Carbides;
TiC, TaC, NbC, VC, Cr3C2
HEAT RESISTANCE
Wear ResistanCE

4. Conventional Forming Methods
GRINDING
Low removal rate*
High Costs*
Waste Management
TURNING
MILLING
Talaş kaldırma temeline dayanan yöntemler
* M.P. Jahan et al. / International Journal of Machine Tools & Manufacture 51 (2011) 837–858

5. W-EDM Process
W-EDM is a non-traditional manufacturing process based on removing material from a part by means of a series of repeated electrical discharges between a tool (wire) and the part being machined in the presence of a dielectric fluid.
Temas yok. Dielektrik; arkı kanalize, kopan parçaları uzaklaştır, soğuma sağlar. CuZn Transferinden bahset.

6. Irrespective of Mech. Prop.
Pros and cons of W-EDM
Pros
Cons
Complex Shapes
Conductivity
Cost Effective
Surface Integrity
Irrespective of Mech. Prop.
Decarburization
Cracks*
Re-cast Layer
DISADVANTAGES
Corrosion*
ETA-PHASE
Decarburisation
Voids
*K. Bonny et al./Tribology International 43(2010)40–54 43

7. W-EDM Surfaces Roughness Number of Cuts Lower Discharge Current
Rough Cut
(1 Cut)
Lower Discharge Current
Lower Discharge Power
Higher Wire Speed
Roughness
Medium Cut
(2~4 Cut)
Finish Cut
(>5 Cut)
Number of Cuts

8. Improving W-EDM surface integrity
Finish Cut
Blasting
PVD Coating*
* B. Casas et al. / Thin Solid Films 447 –448 (2004) 258–263

9. Chemical Vapor Deposition
Chemical reactions of gaseous reactants on heated substrates through exact pressure and temperatures
Non-line of sight method
High temperature process ( °C)
Various materials can be deposited;
Semiconductors
Metallic Films
Refractory Ceramic Materials
Coating Temperatures; 900°C 1015°C
Working Temperatures: 900°C,1015°C

10. The aim of the study
Effects of EDM caused damaged zone on surface integrity of WC-10Co alloy
Effects of dry blasting process on EDM’ed surfaces
Morphology of TiN coatings applied on as EDM’ed and as EDM’ed+dry blasted surfaces
Mechanical properties such as adhesion and wear of TiN coatings deposited on different surface conditions (as EDM’ed/as EDM’ed+dry blasted)

11. Experimental Plan
Application of W-EDM process with different number of cuts
Surface roughness measurements and SEM observation before dry blasting
Dry Blasting application
Surface roughness measurements and SEM observation after dry blasting
TiN coating through MT-CVD technique
Phase analysis with thin film X ray diffraction (XRD)
Surface roughness measurements after TiN coating application
Morphological analysis of the coatings via Scanning Electron Microscopy (SEM)
Adhesion tests (HRC)
Wear tests (ball on disk)

12. Surface Roughness - Before Dry Blasting
2060 nm
EDM (1 Cut)
518 nm
EDM (4 Cuts)
211 nm
EDM (5 Cuts)
142 nm
EDM (7 Cuts)
203 nm
Ground

13. SEM Images – Before Dry Blasting
EDM (1 Cut)
EDM (4 Cuts)
EDM (5 Cuts)
EDM (7 Cuts)
Top
EDM (1 Cut)
EDM (4 Cust)
EDM (5 Cuts)
EDM (7 Cuts)
Cross Section

14. Surface Roughness - After Dry Blasting
858 nm
*DB (1 Cut)
303 nm
DB (4 Cuts)
287 nm
DB (5 Cuts)
282 nm
DB (7 Cuts)
*DB: Dry Blasted
Dry blasting parameters:
10 seconds
5 bar pressure
320 mesh Al2O3-SiC mix powder

15. Surface Roughness - After Coating
1710 nm
EDM (1 Cut)+TiN
493 nm
EDM (4 Cuts)+TiN
225 nm
EDM (5 Cuts)+TiN
177 nm
EDM (7 Cuts)+TiN
936 nm
DB (1 Cut)+ TiN
342 nm
DB (4 Cuts)+TiN
273 nm
DB (5 Cuts)+TiN
221 nm
DB (7 Cuts)+TiN
159 nm
Ground+TiN

16. XRD Patterns Co6W6C WC CuZn WC – Etafaz - CuZn 25.06.2014 Ground + TiN
EDM (1 Cut) + TiN
DB (4 Cuts) + TiN
DB (1 Cut) + TiN
EDM (4 Cuts) + TiN
Co6W6C WC
WC – Etafaz - CuZn
CuZn

17. Surface Morphology of the Coatings @ 900°C
EDM (1 Cut) + TiN EDM (4 Cuts)+TiN EDM (5 Cuts) + TiN
Blasted morphology -> Nodular + Star + Lenticular
Ground + TiN
*H.-E. Cheng, Y.-W. Wen / Surface and Coatings Technology 179 (2004) 103–109
DB (1 Cut) + TiN DB (4 Cut) + TiN DB (5 Cut) + TiN

18. Cross-sectional SEM Images of the Coatings @ 900°C
EDM (1 Cut) + TiN - SEI
EDM (1 Cut) + TiN - BSI
DB (1 Cut) + TiN
Ground + TiN

19. Surface Morphology of the Coatings @ 1015°C
EDM (1 Cut) + TiN
EDM (4 Cut) + TiN
EDM (5 Cut) + TiN
Ground + TiN
DB (1 Cut) + TiN
DB (4 Cut) + TiN
DB (5 Cut) + TiN
(1)
(2)
J. Wagner et al. / International Journal of Refractory Metals & Hard Materials 26 (2008) 120–126
H.-E. Cheng, Y.-W. Wen / Surface and Coatings Technology 179 (2004) 103–109

20. Hardness Rockwell-C adhesion test
Adhesion 900°C
EDM (1 Cut) + TiN
DB (1 Cut) + TiN
Standard VDI 3198
Hardness Rockwell-C adhesion test
Ground + TiN
EDM (4 Cuts) + TiN
DB (4 Cuts) + TiN

21. Ball on Disc Test Apparatus
Wear Tests
Ball on Disc Test Apparatus
WEAR TEST PARAMETERS
Load
10 N
Distance
150 m
Wear Track Radius
2.5 mm
Linear Speed
10 cm/s
Ball
Alumina
Ball Diameter
5 mm
LOAD
ALUMINA BALL

22. Wear Tests As EDM’ed (1 cut) and coated tribolayer μmean = 0.72

23. Wear Tests
As EDM’ed (1 cut) and coated – Ball wear scar

24. Wear Tests
As dry blasted (1 cut) and coated
μmean = 0.66 X

25. Wear Tests As dry blasted (1 cut) and coated – Ball wear scar

26. Hill/valley structure due to direct impingement in dry blasting
Wear Tests
As dry blasted (1 cut) and coated - Material transfer from alumina ball
858 nm
Hill/valley structure due to direct impingement in dry blasting
Higher deformation resistance of mixed (nodular, star shaped and lenticular) morphology *
Substrate
Undeformed TiN
Al rich tribolayer
Polished TiN
* H.-E. Cheng, Y.-W. Wen / Surface and Coatings Technology 179 (2004) 103–109
Wear track

27. The Results of Wear Tests
As EDM’ed (1 cut)
As dry blasted (1 cut)

28. Conclusions
Better surface integrity through dry blasting after w-EDM process
TiN morphology changes from coarse nodular (as EDM’ed) to the mixed structures of fine nodular/star shaped/lenticular (as dry blasted) crystals at 900 °C, depending on the surface condition
The adhesion strength of TiN layer was improved by applying dry blasting on EDM’ed surfaces
The friction and wear properties of TiN coating are relatively better on dry blasted samples

29. Dr. Güldem KARTAL ŞİRELİ
Acknowledgements
Prof. Dr. Mustafa ÜRGEN
Doç. Dr. Kürşat KAZMANLI
Dr. Güldem KARTAL ŞİRELİ

30. THANK YOU