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Wear Resistance Comparison between Bearing Cages
with Peek Coating vs. Copper + Silver Coating
2007/09/28 ~ 2007/11/07
WHAT IS PEEK?
PolyEtherEtherKetone or PEEK is high temperature thermoplastic that is very resistant to chemical and fatigue environments and has very good thermal stability. PEEK is an excellent material for a large array of thermal plastic applications where combustion, thermal, and chemical performance is critical. Peek exhibits a high ability ability to retain flexural and tensile properties at very high temperatures 250°C (482°F) or more as well as high pressure environments.
PEEK's properties make it the ideal choice for extending the life of high-speed, high-load motorcycle engine bearings:
>>> Outstanding wear and abrasion resistance
>>> Low coefficient of friction
>>> Low smoke and toxic gas emissions.(Out gassing or emitting of smoke and gas during combustion are among the lowest of any thermoplastic material.)
>>> Similar chemical and water resistance as PPS (PolyPhenylene Sulfide), however has greater high temperature resistance
Materials specifications common PEEK materials: Density 1300 kg/m3
Young's modulus (E) 3700 MPa
Tensile strength (σt) 90 MPa
Elongation @ break 50%
notch test 55 kJ/m2
Glass temperature 130-150 °C and 260-290 ºC
melting point ~350 °C
Vicat B[citation needed] -
heat transfer coefficient (λ) 0.25 W/m.K
linear expansion coefficient (α) 1.7 10-5 /K
Specific heat (c) - kJ/kg.K
Water absorption (ASTM) - NA
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1. Test Bearings
(A): 30X38X15.8mm (cage coated with copper 12µm+silver 3µm)
(B): 30X38X15.8mm (cage coated with Peek polymer) 13~ 15 µm )
2. Bearing speed = 9500 rpm
3. Lubricant = SAE 15W40, 3µm filter
4. Test period = 200 hrs
5. PV value (cage/ outer race): 14 Mpa. m/sec (contact pressure 1.48 Mpa, rel. speed 9.45m /sec )
6. Outer race: SUJ2/ HRc 62 ~ 64
Test Result
As per the following table, the copper + silver coating on cage has worn out completely after 80hrs test. However, the Peek coated cage is only slightly worn after 180 hrs of testing. Test confirm that the wear resistance of Peek-coated cages far exceeds that of conventional silver/copper-plated cages.
Test #1 period (hrs ) |
Copper + silver coated cage
30X38X15.8mm (cage coated with copper 12µm+silver 3µm)
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Peek coated cage
30X38X15.8mm (cage coated with Peek polymer) 13~ 15 µm )
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| Before test |
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40 Hours |
Silver layer completely worn out
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Practically no wear
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60 Hours |
Partially worn out copper layer
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Slight scuffing of Peek
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80 Hours |
Completely worn out copper layer
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Moderate scuffing of Peek
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180 Hours |
All silver and copper plating worn away
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Visible scuffing but still going strong
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200 Hours |
Peek coating is still not worn through after 200 hours
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Test 2:
150 cc scooter engine big end test of Peek Coating vs. Copper + Silver Coating Pmax: 7500rpm
| Test #2 |
28x36x13.8mm bearing (cage coated with copper + silver, total coating thickness ~ 15 µm) |
28x36x13.8mm bearing (cage coated with Peek, total coating thickness ~ 15 µm) |
Bearings
before test |
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| Bearings after test |
Bearing failed after 70 hours: fatigue
occurred on rollers and cage
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After 160 hrs Pmax (7500rpm) test: (test stopped for small end failure)
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| Con-rods after test |
Con-rod has worn out - grooved
to a depth of 0.2mm
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Con-rod has no obvious wear
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Wayne Wright and Steve Rothwell
The Two-Stroke Shop/ Cairns Motorcycle Tours and Hire
9 Compass Close, Edge Hill
Cairns 4870
Tropical North Queensland, Australia
Tel. (In Australia): 0427 774 285
Tel. (Outside Australia): +61 427 774 285
Web: www.bikingaustralia.com
Email: offbeat@iinet.net.au
ABN 11 346 987 340
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