Ultrananocrystalline diamond film as a wear resistant and protective coating for mechanical seal applications.
Mechanical shaft seals used in pumps are critically important to the safe operation of the paper, pulp, and chemical process industry, as well as petroleum and nuclear power plants. Specifically, these seals prevent the leakage of toxic gases and hazardous chemicals to the environment and final products from the rotating equipment used in manufacturing processes. Diamond coatings have the potential to provide negligible wear, ultralow friction, and high corrosion resistance for the sliding surfaces of mechanical seals, because diamond exhibits outstanding tribological, physical, and chemical properties. However, diamond coatings produced by conventional chemical vapor deposition (CVD) exhibit high surface roughness (R{sub a} {>=} 1 {mu}m), which results in high wear of the seal counterface, leading to premature seal failure. To avoid this problem, we have developed an ultrananocrystalline diamond (UNCD) film formed by a unique CH{sub 4}/Ar microwave plasma CVD method. This method yields extremely smooth diamond coatings with surface roughness R{sub a} = 20-30 nm and an average grain size of 2-5 nm. We report the results of a systematic test program involving uncoated and UNCD-coated SiC shaft seals. Results confirmed that the UNCD-coated seals exhibited neither measurable wear nor any leakage during long-duration tests that took 21 days to complete. In addition, the UNCD coatings reduced the frictional torque for seal rotation by five to six times compared with the uncoated seals. This work promises to lead to rotating shaft seals with much improved service life, reduced maintenance cost, reduced leakage of environmentally hazardous materials, and increased energy savings. This technology may also have many other tribological applications involving rolling or sliding contacts.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 961331
- Report Number(s):
- ANL/ET/JA-46700
- Journal Information:
- Tribology Trans., Journal Name: Tribology Trans. Journal Issue: 2005 Vol. 48
- Country of Publication:
- United States
- Language:
- ENGLISH
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Related Subjects
21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
36 MATERIALS SCIENCE
CHEMICAL PROPERTIES
CHEMICAL VAPOR DEPOSITION
COATINGS
CORROSION RESISTANCE
COST
DIAMONDS
ENVIRONMENT
EQUIPMENT
FILMS
FRICTION
GASES
GRAIN SIZE
HAZARDOUS MATERIALS
INDUSTRY
LEAKS
MAINTENANCE
MANUFACTURING
MECHANICAL SHAFTS
NUCLEAR POWER PLANTS
OPERATION
PETROLEUM
PROTECTIVE COATINGS
PUMPS
ROUGHNESS
SEALS
SERVICE LIFE
SURFACES
WEAR