Title: Tribology of Carbide Derived Carbon Coatings Grown on Tungsten Carbide
1Tribology of Carbide Derived Carbon Coatings
Grown on Tungsten Carbide
- M. Tlustochowicz1, M. McNallan1, A. Erdemir2, S.
Sudarshan3, and R. Radhakrishnan3 - University of Illinois, Chicago, IL
- Argonne National Laboratory, Argonne, IL
- Materials Modification, Inc., Fairfax, VA
2Etching in Halogens
Schematic showing how our CDC process differs
from other coating techniques, such as chemical
vapor deposition (CVD) and physical vapor
deposition (PVD), that are currently used to
produce carbon coatings.
3Properties of Carbide Derived Carbon
- Structure resembling
- partially graphite and
- partially diamond
- Diamond structures
- are found only close
- to the interface graphite and carbon onions
are more common further away - Nanoporous structure
- Residual chlorine present
4Challenges Posed by Conventional Microcrystalline
Tungsten Carbide (WC) Cermets
- Most commercial WC products are cermets
containing typically 6 Co or Ni as binder - Chlorination causes selective attack of the metal
binding phase before carbide is etched - Samples may experience significant weight loss or
complete disintegration
5Nanocrystalline WC a Novel Material
- When the nc-WC is densified with minimal or no
binder, appropriate selection of CDC processing
conditions can produce coatings with tribological
characteristics comparable to those of CDC on
SiC. - Nanoindentation results
Modulus GPa Hardness GPa
CDC on nano-WC (900 C for 3 hrs) 15.32.8 1.050.25
CDC on SiC (1000 C for 1 hr) 15.33.7 1.000.37
6Typical Microcrystalline Cermet-WC Tribological
Results
7Nanocrystalline WC Tribological Results
After Treatment at 900 C
Friction coefficient versus time in pin-on-disk
test on nanocrystalline WC before and after
chlorination treatment at 900 C.
8Silicon Carbide Tribological Results
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10Conclusions
- Carbide derived carbon (CDC) can be produced on
nanocrystalline tungsten carbide by selective
reaction of tungsten with chlorine - When created in appropriate processing
conditions, CDC significantly lowers the friction
coefficient of WC - CDC synthesized from nanocrystalline WC has
similar tribological properties to these of CDC
grown on SiC