handbook of carbon, graphite, diamond and fullerenes

4.5 Mechanical Applications
Molded Graphite 117
Fine-grain, high-density, and low-porosity molded graphite is extensively
used for bearings and seals, particularly in high-temperature applications
(up to 600°C) where conventional liquid lubricants degrade rapidly. It
has excellent lubricating and frictional properties (reviewed in Sec. 2.5
above), it is chemically resistant, its high thermal conductivity helps
dissipate the heat generated by rubbing action and, at high temperature
(>500°C), its compressive strength is superior to that of most other
engineering materials.
However molded graphite cannot be used to seal materials that would
attack it chemically, such as aqua regia, perchloric acid, and oleum (fuming
sutfuric acid) (see Ch. 3, Sec. 7.0). Sealing failure may also occur with
abrasive materials such as chromic acid, chromic oxide, chrome plating
compounds, potassium dichromate, sodium chromate, and sodium dichro-
The following is a partial list of current commercial applications of
bearings and seals:
• Seal rings for gas-turbine engines to protect compressorshaft
bearing and engine oil system for 600°C gases, at
rubbing speed of 150 m/s and 10,000 hours service.
• Seal rings in chemical pumps for corrosive-fluid transfer with
a rubbing speed of 15 m/s, operating up to 100°C for 10,000
hours.
• Seal rings for water pumps of industrial and truck diesel
engine, operating at 120°C and 0.18 N/mm 2 (25 psi) for20,000
hours.
• Seals rings for automobile freon air compressor for air
conditioning, operating up to 1.75 N/mm 2 (250 psi) and 93°C.
• Seal rings for home washing machine and dishwasher water
pumps, operating at 0.28 N/mm 2 and to 66°C for 10 years
• O-rings for cylinder heads of race-car engines
Other mechanical applications of molded graphite include glass-lehr
roll bearings, roller bearings for jet-engine exhaust nozzles, metering seats
for gasoline pumps, vane pumps for air compressors, rupture disks, and
many others.