Microstructure and Mechanical Properties of Hydrogenated WC-C Nanocomposite

1
Microstructure and Mechanical Properties of
Hydrogenated WC-C Nanocomposite
S. J. Parka),b) K.-R. Leea), D.-H. Kob), J. H.
Hanc), K. Y. Eun a) a) Thin Film Research Center,
Korea Institute of Science and Technology b)
Department of Ceramic Engineering, Yonsei
University c) Korea Research Institute of
Standard and Science
2
Applications of DLC Film
3
Disadvantages of DLC Film

• Thermal instability
• degradation beyond 500C
• High residual compressive stress
• Max 10 GPa
• Poor adhesion
• Steel, Oxide, Sulfide, etc.

4
Trends of Hard Coatings
Single layer films Diamond, DLC, CNx, Nitride,
Carbide etc.
A.A.Voevodin et al., Tribology International 29
(1996) 559
S. Veprek et al., Surface Coat. Technol. 133-134
(2000) 152
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How to Overcome the Disadvantages of DLC Film

• Transition metal carbide DLC

• TiC and WC nanograins embeded in DLC matrix

• Nanocrystalline/DLC nanocomposite

The desirable combination of hardness,
toughness, low friction and wear in ambient
environment

• A. A. Voevodin et al. Thin Solid Films, 342
  (1999) 194

6
Purpose of the Present Work

• The synthesis of WC-C nanocomposite thin film
  using a hybrid DC magnetron sputtering with RF
  PACVD system
• Relationship between the mechanical properties
  and the microstructure

7
Experimental Conditions

• Hybrid DC magnetron sputtering
• CH4 Ar (CH4/(ArCH4 ) 0.33 0.58)
• Deposition pressure 1.33 Pa
• Cathode target current 300 mA
• Substrate bias -150 Vb RF biasing
• Substrate P-type (100) Si wafer
• 100 ? Si wafer
• for stress measurement

W Target
Substrate
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W Concentration in the Film
9
Residual Stress of the Film
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Hardness of the Film
11
XRD Spectrum of the Film
12
Diffraction Pattern of the Film
(200)
(220)
(111)
(311)
6. 9 at.
14.5 at.
26 at.
13
TEM Micrograph of the Film
W 6.9 at.
40 nm

• Diffraction Pattern

• Plan-View Image

14
Resistivity of the Film
15
G-Peak Position of the Film
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Structural Change with W Concentration
DLC Matrix
c-WC Crystalline
W Below 13 at.
W 13 - 15 at.
W Beyond 15 at.
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Relationship between Structure and Mechanical
Properties
18
Conclusions

• Nanocomposite of WC phase and DLC matrix was
  produced by the addition of W into DLC films. The
  content of WC phase was proportional to the W
  concentration in the film.
• The mechanical properties of WC-C nanocomposite
  were closely related to the physical contact of
  WC nanocrystals.
• Below 13 at. of W, mechanical properties of
  WC-C film were determined by DLC matrix because
  WC nanocrystals were isolated.
• Beyond 13 at. of W, WC nanocrystals began to
  contact. Hence, the mechanical properties of WC
  nanocrystals affected the mechanical properties
  of the nanocomposite film. Because the physical
  contact increased with increasing WC content, the
  hardness of the film increased.

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Friction Coefficient of the Film