Tribology & wear out of Mechanisms. Presentation on Innovation Day 07 by Verhaert Space

1. © VERHAERT SPACE
Tribology & wear-out of mechanisms
VERHAERTINNOVATIONDAY – OCTOBER 12th, 2007
www.mastersininnovation.com
Tribology and wear-out of
mechanisms
Luc Bierque
Luc.bierque@verhaertspace.com
www.verhaertspace.com
Commercially confidence – This presentation contains ideas and information which are proprietary of VERHAERT SPACE, it is given in confidence. You are authorized to open and view the
electronic copy of this document and to print a single copy. Otherwise, the material may not in whole or in part be copied, stored electronically or communicated to third parties without prior
agreement of VERHAERT SPACE.
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2. © VERHAERT SPACE
Tribology & wear-out of mechanisms
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Introduction
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Tribology & wear-out of mechanisms
Introduction (1/3): Purpose
It’s important to keep wear out under control, think at:
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• Downtime of production.
• People involved in repair and maintenance
• Loss of mission (space application)
However, beating wear is much more than the introduction of high-tech
solutions, it is very important to apply the correct
methodology/approach.
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Tribology & wear-out of mechanisms
Introduction (2/3): What affects wear?
• Contact load/stress
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• Hardness
• Existence of oxidation films
• Temperature
• Ambient/working pressure (e.g. adhesive wear in vacuum)
• Working conditions: corrosion, speed, vibrations
• The surface microstructure and surface condition
• The choice of material pairs
• …
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Tribology & wear-out of mechanisms
Introduction (3/3): What is Tribology?
“ Science and technology of interactive surfaces in relative motion
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w.r.t. each other and related subjects/practices”.
It covers the subject of friction, wear and lubrication.
It’s all around us…
12.10.2007 Slide 5
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6. © VERHAERT SPACE
Tribology & wear-out of mechanisms
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Methodology followed by
Verhaert Space
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7. © VERHAERT SPACE
Tribology & wear-out of mechanisms
Methodology:
1. Select between wet and dry lubrication
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(this sets the initial working conditions).
2. Avoid a poor design, operation/functioning of your
mechanism.
3. Analyze/ assess contact loads/stresses, bending
stresses, …
4. Assess/analyze the wear aspects/phenomenon.
5. Make final decision on tribological selection.
6. Perform functional, friction/wear and life test.
12.10.2007 Slide 7
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8. © VERHAERT SPACE
Tribology & wear-out of mechanisms
1. Select between wet and dry lubrication
(this sets the initial working conditions).
www.mastersininnovation.com
2. Avoid a poor design, operation/functioning of your
mechanism.
3. Analyze/ assess contact loads/stresses, bending
stresses, …
4. Assess/analyze the wear aspects/phenomenon.
5. Make final decision on tribological selection.
6. Perform functional, friction/wear and life test.
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Tribology & wear-out of mechanisms
1-Select between wet and dry lubrication (1/3):
Overview
Wet/liquid lubrication: Solid/dry lubrication:
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• Oil. • Lamellar solids (MoS2, graphite).
• Grease. • Self lubricating materials (polymers,
bronzes…).
• Surface treatments/coatings.
• Ceramic materials.
• Nanomaterials/composites
•…
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10. © VERHAERT SPACE
Tribology & wear-out of mechanisms
1-Select between wet and dry lubrication (2/3):
Wet lubrication: Pro & cons
+ -
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• Allows high duty & high speed • Vapor pressure: evaporation loss
operation (oil)
• Limited temperature range
• Possibility of hydrodynamic
(-70 to + 250 deg. C)
lubrication (oil)
• Viscosity is temperature & pressure
• Thermal conduction superior to
dependant
most solid lubricants
• Surface migration & leaks: requires
• Do not generate wear debris
seals
• Relatively cheap and easily applied
• Lubrication regime is speed
• Minimum torque noise
dependant (does not support
• In most cases offers additional
accelerated life test)
corrosion protection
• Removal (oil filter) & means for • Degradation of oil over time
detection of wear particles • Not allowed for some application
(magnetic)
(medical, food…)
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Tribology & wear-out of mechanisms
1-Select between wet and dry lubrication (3/3):
Dry lubrication: Pro and con’s
+ -
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• Negligible vapor pressure (OK in • Generation of wear debris
vacuum and low pressures)
• Friction/wear can be sensitive to
• No surface migration/creep (avoids
moisture/water (e.g. MoS2).
the use of seals)
• Life limited by lubricant wear.
• Wide operational temperature range
• Wear rate is often independent of • Adherence of coatings can be
speed (supports accelerated life cumbersome.
test)
• Electrically conductive
• Avoids start up wear (e.g. wet on
dry)
• Applications where oil/grease is not
allowed (food/medical).
• …
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12. © VERHAERT SPACE
Tribology & wear-out of mechanisms
1. Select between wet and dry lubrication (working
conditions).
www.mastersininnovation.com
2. Avoid a poor design, operation/functioning of your
mechanism.
3. Analyze/ assess contact loads/stresses, bending
stresses, …
4. Assess/analyze the wear aspects/phenomenon.
5. Make final decision on
lubrication/technology/materials.
6. When possible/required: perform functional,
friction/wear and life test.
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13. © VERHAERT SPACE
Tribology & wear-out of mechanisms
2-Avoid a poor design (1/3):
Mechanism design drivers
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• Implementation of wet/dry lubrication.
• Available space/volume and mass.
• Loading/forces/torque.
• Speed, precision, stiffness, allowable misalignments.
• Loads.
• Required lifetime
• Environmental conditions (temperature, pressure, vibration/shock…).
• Vibration/noise levels (quiet running).
• Friction.
• Allowable/required materials.
•…
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14. © VERHAERT SPACE
Tribology & wear-out of mechanisms
2-Avoid a poor design (2/3):
Design & operation aspects
• Implement preloading: to avoid fretting wear, slippage of bearing balls…
Soft preloading:
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Insensitive to different thermal expansion (CTE).
Hard/rigid preloading:
Higher rigidity.
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2-Avoid a poor design (3/3):
Design & operation aspects
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Design for the correct stiffness <> contact load:
• “Back to back” bearing configuration.
• “Face to Face” bearing configuration.
• Selection of contact angle.
Back-to-back arrangement Face-to-face arrangement Tandem arrangement
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16. © VERHAERT SPACE
Tribology & wear-out of mechanisms
1. Select between wet and dry lubrication (working
conditions).
www.mastersininnovation.com
2. Avoid a poor design, operation/functioning of your
mechanism.
3. Analyses aspects to be covered
4. Assess/analyze the wear aspects/phenomenon.
5. Make final decision on
lubrication/technology/materials.
6. When possible/required: perform functional,
friction/wear and life test.
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Tribology & wear-out of mechanisms
3- Analysis aspects to be covered (1/1)
Aspect Space Industrial
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applications applications
Stress/strength/ stifness of mechanical parts Yes Yes
Fatigue/fracture Yes Yes
Preload/tolerance analysis Yes Yes
Thermo elastic deformation Yes Yes
Hertzian contact stresses Yes Yes
Shock/vibration generation & susceptability Yes In most cases
Life prediction Always test Prediction
Required forces/ drive torques etc. Test + Prediction or
analysis test
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18. © VERHAERT SPACE
Tribology & wear-out of mechanisms
1. Select between wet and dry lubrication (working
conditions).
www.mastersininnovation.com
2. Avoid a poor design, operation/functioning of your
mechanism.
3. Analyze/ assess contact loads/stresses, bending
stresses, …
4. Assess/analyze the wear aspects
5. Make final decision on lubrication/ technology/
materials.
6. When possible/required: perform functional,
friction/wear and life test.
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Tribology & wear-out of mechanisms
4-Assess/analyse the wear aspects (1/6)
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This requires understanding of the basic wear theory/ tribology.
Existing myths (see further: some examples given).
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Tribology & wear-out of mechanisms
4-Assess/analyse the wear aspects (2/6)
Myth 1: “Engineering surfaces are flat, smooth and clean”.
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Surfaces are never smooth/flat, the degree of roughness depends on the level
of examining the surface.
Surfaces are always contaminated: this can help against adhesion but can be a
burden w.r.t. adhering a lubricant coating etc.
Surface machined by conventional process
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Tribology & wear-out of mechanisms
4-Assess/analyse the wear aspects (3/6)
Myth 2: “The larger the area in contact, the larger the friction”.
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Zero friction does not exist.
The friction force is proportional to the applied load: Fw = N * f or f= Fw/N,
tg(fi)=Fw/N (f = friction coefficient, which is unit less)
fi
N
Fw F
F
G
G
Fw
N
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Tribology & wear-out of mechanisms
4-Assess/analyse the wear aspects (4/6)
Myth 3: “When in contact, bodies touch of their entire surface
area”.
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F
P=?
Area (A)
Conventional mechanics: Pressure (P) = Force (F) / Area (A).
In reality, when two surfaces are pressed together, interaction
only takes place at the tips of the surface asperities. The area
of contact between 2 elastically deformed bodies can be
calculated using the Hertz theory.
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Tribology & wear-out of mechanisms
4-Assess/analyse the wear aspects (5/6)
Myth 4: “Friction and wear are related”.
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High friction does not always mean that you get a higher wear (see plot)
Specific wear rate (k)
Friction coefficient
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Tribology & wear-out of mechanisms
4-Assess/analyse the wear aspects (6/6)
Myth 5: “ You always need large quantities of oil/grease to get
good lubrication”
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> No, small quantities are generally sufficient.
> A certain amount of lubricant is usually in place for another reason:
Removal of heat (e.g. car engine)
Reserve for lubricant losses (e.g. leakage, evaporation,
creep,…)
Feel confident
> On the other hand: too much lubricant can produce excessive heat &
torque or power losses or even damage.
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25. © VERHAERT SPACE
Tribology & wear-out of mechanisms
1. Select between wet and dry lubrication (working
conditions).
www.mastersininnovation.com
2. Avoid a poor design, operation/functioning of your
mechanism.
3. Analyze/ assess contact loads/stresses, bending
stresses, …
4. Assess/analyze the wear aspects/phenomenon.
5. Make final decision on tribological selection.
6. When possible/required: perform functional,
friction/wear and life test.
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26. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5-Make final decision on tribological selection
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Based upon the above:
→ Confirm initial selection
wet <> dry lubrication
→ Detailed implementation & final selection
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27. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5-Make final decision on tribological solution
5.1- Liquid/ wet lubricant examples
Type Tradename Vapour Pour Max. Viscosity Application
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pressure point temp index
° °
(mbar at ASTM
(°C) (°C)
° D2270
20°C)
Perfluorinated Fomblin Z25 1.6E-13 -75 +250 358 Space mechanisms
oils (Ausimont Italy)
Perfluorinated Krytox 143AC 1E-6 -35 +285 134 Space mechanisms
oils (Dupont US)
MAC oil Pennzane SHFX2000 -48 +150 137 Space mechanisms
Synthetic oil BP135 (BP UK) 1E-8 -57 +200 137 Space mechanisms
↑
Synthetic Rotella SAE 5W-40 -40 +220 176 Heavy duty diesel &
gasoline engine
↑
Synthetic Aeroshell turbine -55 +250 105 Jet, helicopter and
500 industrial turbines
↑
Paraffinic + Shell S68 -37 +230 115 Rotary screw compressors
additives + ammonia refrigeration
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28. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5-Make final decision on tribological solution
5.2- Solid/dry lubrication technology
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5.2.1 Self lubricating materials (polymers, bronzes…).
5.2.2 Surface treatments/coatings.
5.2.3 Ceramic materials.
5.2.4 Nano composite materials.
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Tribology & wear-out of mechanisms
5.2.1 Self lubricating materials (polymers).
Polymer Density Tensile Wear Hardness Max. temp. TC CTE
°
(kg/m³) strength particle (Shore D) (°
C) (W/mK) (ppm/°C)
(MPa) generation
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PTFE, Teflon ® 1400 9 Good 50-65 280 0.23 90
Polyacetal 1400 5 Good 65 90 0.23 90
30% PTFE filled 1400 45 Good 60 100 - -
acetal
Polyamide, Vespel 1450 86 (SP1) Excellent 85 310 0.54 -
® 1600 59 (SP3) 80
Phenolic ® - 62 Poor 75 170 - 18-450
Torlon ® 1420 105 Excellent 50 to 90 270 0.26 31
Peek ™ 1500 97 Good 85 250 0.25 40
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Tribology & wear-out of mechanisms
5.2.1 Self lubricating materials (polymers).
Phenolic material: application example.
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We have successfully applied cotton-phenolic bearing cages in high-speed,
lightly lubricated bearings (momentum wheel and motor applications).
Phenolic also finds its way in industrial applications (e.g. SKF bearings, Barden
US…). The lubricant we applied was Pennzane X2000, also the cage was oil
impregnated.
Advantages:
• Low coefficient of friction
• Ability to absorb lubricant
• Dimensional stability in presence of
lubricants/moisture
• Good strength-to-weight ratio
• Easily machined
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Tribology & wear-out of mechanisms
5.2.1 Self lubricating materials (bronzes).
Cast bronzes are widely used because of combination of moderate to high strength,
corrosion resistance, wear resistance and tribological behavior.
Examples:
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UNS number Name Composition Tensile Applications
strength
(MPa)
C93700 (SAE 64) High lead tin 80% Cu, 10% 270 Bearings for high speed and heavy
bronze (1) Sn, 10% Pb pressures, pump parts, pressure
tight castings
C90700 (SAE 65) Phosphor gear 90% Cu, 10% 305 Heavy duty gears, high load
bronze Sn bearings, bushings and worm
wheels
C86300 (SAE430B) High strength 63% Cu, 820 Heavy duty high strength alloy for
manganese 25%Zn, 3% Fe, gears, cams, slow speed heavy load
bronze 6% Alu, 3%Mn bearings, screw down nuts
C95400 (TQ00 Aluminium 85% Cu, 4%Fe, 620-700 High strength bearings, bushings,
temper) bronze 11% Alu gears, worms, wear plates, valve
seats and guides
(1): Widely used for space applications (BB cage material + ion lead plated coating)
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32. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5-Make final decision on tribological solution
5.2- Solid/dry lubrication technology
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5.2.1 Self lubricating materials (polymers, bronzes…).
5.2.2 Surface treatments/coatings.
5.2.3 Ceramic materials.
5.2.4 Nano composite materials.
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33. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings (overview)
Technology level
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Physical Vapor Chemical Vapor
Deposited (PVD) Deposited (CVD)
Pulsed Plasma nitriding
Laser cladding Dispersion coating
Carburizing Nitriding Anodizing
Induction/flame hardening
Resin bonded coatings
Process complexity
Burnished films
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Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings (thickness)
Surface treatment depth Coating/treatment thickness
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Nitriding/ carburizing
Anodizing
Ion implant
Plasma spraying
CVD
PVD
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Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
Burnished films
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Application Application of lubricant film onto the surface (by hand e.g. brush or cloth)
Layer Crude and difficult to achieve a good and constant layer thickness
Life Short life (low duty).
Lubricant Mostly MoS2/graphite based lubricants
Applications - Low duty hinges and axes of various equipments
- Corrosion & wear protection of low duty items
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Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
Resin bonded coatings (1/2) “ lubricating paints”
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Application Application of lubricant films, which are painted or sprayed onto the
surface.
They mostly require curing following application (can also be air cured).
Layer About 1 micron. Not always easy to achieve a constant layer thickness.
Life Moderate
Lubricant MoS2, Teflon ® based, Silicon oils, Nickel
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Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
Carburizing
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Process Steel hardening.
Involves the diffusion of carbon into the surface layers of a low carbon steel at high
temperatures. Controlled cooling after carburising (water, oil or polymer quenching)
produces hard martensitic layers at the surface.
Purpose Increase hardness (wear resistance) and fatigue strength of generally low carbon steels
Layer Materials can be hardened to about 650Hv whilst leaving the body relatively tough and
fatigue resistant.
Applications General low carbon steel hardening.
Create hard and good adhesive layer for PVD/CVD coatings.
Practically used on all automotive gearwheels.
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Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
Nitriding
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Process Steel hardening.
Involves the diffusion of nitrogen into the surface layers at temperatures between 500 –
and 570 °C
Purpose Increase hardness (wear resistance) and fatigue strength of including cast iron, mild
steel, tools, high speed and stainless steels.
Layer Hardness <> layer thickness (see next slide)
Applications General steel hardening and fatigue strength improvement
Create hard and good adhesive layer for PVD/CVD coatings
General machine parts, gears, extrusion worms, diesel injector bodies, crankshafts,…
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39. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
Pulsed plasma nitriding
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Similar to traditional nitriding technology but with the following
advantages:
• Less risk to change the core properties of your material
• Shorter process times (compared to traditional nitriding)
• Better uniformity
• Possible on complex geometries/surfaces
• Eliminates costly cleaning or grinding to remove the brittle white layer
associated with traditional nitriding.
• Higher hardness than conventional nitriding (up to 1300 HV).
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40. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
Anodizing
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Process Hard anodisation of aluminium alloys
Purpose Increase surface hardness and/or abrasion resistance.
Layer The thicknesses are usually between 25 and 250 µm (pending on the
anodising time).
Advantages Wear resistant - Low coefficient of friction –
Anti-adhesion - High corrosion resistance –
High chemical resistance - FDA compliance
Applications Items and machine elements used in food industry (no extra lubricants).
Extended hard anodize: TUFRAM ®
> Aviation & non-magnetic bearings.
> Automotive items, folding devices,
pneumatics, medium load items.
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41. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
Ion implantation
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Process Relatively low temperature PVD process
Purpose Increase wear resistance, friction, fatigue life,
corrosion and oxidation resistance.
Typical implants C, Ni, O, Boron
Layer thickness Typical 0.1 micron
Advantages The process can be applied to virtually any
material, including most metals, ceramics and
polymers
Niche application:
Precision-tempered steel bearings:
Advantage w.r.t. traditional coatings (even very thin layers) which can
result in unacceptable dimensions and surface finish changes.
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Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
Laser cladding
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Process Similar to surface melting, but promotes alloying by injecting
another material into the melt pool, using a laser.
Purpose Achieve high-temperature performance, wear resistance, improved
corrosion resistance, better mechanical properties…
Typical implants Powder material, ceramics
Layer thickness Strong metallurgical bond.
Thickness from several hundred microns to several millimeters
Post treatment Grinding and polishing generally required after coating
Limitations • Unable to coat areas that are out of the line of sight.
.
• If the density is too high, cracking and delamination can occur
as is the case with aluminum and some steels.
Applications Machine parts, crank shafts, heavy industry parts
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43. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
Physical Vapor Chemical Vapor
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Deposited (PVD) Deposited (CVD)
PVD covers processes, such as: CVD covers processes, such as:
• Sputtering • Atmospheric Pressure Chemical Vapour
• Magnetron sputtering Deposition (APCVD)
• Evaporation • Low Pressure Chemical Vapour
• Ion plating Deposition (LPCVD)
• Catodic arc deposition • Metal-Organic Chemical Vapour
• Arc vaporisation Deposition (MOCVD)
• Vapor ionisation (plasma) • Plasma Assisted Chemical Vapour
Deposition (PACVD)
• Plasma Enhanced Chemical Vapour
Deposition (PECVD)
• Laser Chemical Vapour Deposition (LCVD)
·
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44. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
Physical Vapor Chemical Vapor
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Deposited (PVD) Deposited (CVD)
Pro’s: Pro’s:
• Metallic & non-metallic • Metallic & non metallic (but less than PVD)
• Can penetrate porous bodies, blind holes • Coatings are conformal & near net shape
• High purity (99,99%) • Relatively low temperature
• Material formations below melting point > No post re-hardening to be applied
• Coatings are conformal & near net shape • Good for sharp edges (cutting tools)
• Many parts can be coated simultanuously
Con’s:
Con’s: • Only coat area’s exposed to ion source:
• Substrate to be heated (can loose hardening) not for deep holes
> required post re-hardening • Most processes not for aluminium
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45. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
Physical Vapor Chemical Vapor
Typical coatings
Deposited (PVD) Deposited (CVD)
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Material Hardness Typical application
Titanium carbonitride TiCN 4000 High duty coating for polymer bearings (over 2 to
3 times tool life of TiC)
Titanium carbide TiC Coating of 440C balls
Titanium aluminium nitride TiAlN 2600 High temp drilling & tapping tools
Titanium nitride TiN 2900 One of the oldest coatings in automotive,
machine tools
Chromium nitride CrN 1700-2500 Dies, heavy duty forming applications
Zirconium nitride ZrN 2800-4600 Punches & cutting tools, blades
Diamond like coating 1000-5000
(DLC)
Tungsten carbide WC (W2C) 2400 Cutting tools, extreme high temperature use,
dies, punches
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Tribology & wear-out of mechanisms
5.2.2 Surface treatments/coatings
(PVD) Example: ion plated gearbox (Verhaert Space):
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Main features/requirements (prime):
• Planetary gear
• Storage without maintenance: 1 year
• In orbit standstill: 1 year
• Input speed: 1662 rpm
• Output speed: 3 (red. Ratio 554)
• Output torque: 427Nm
• Gear material: MP35N (Ftu=1800MPa; 545HV)
• Bearing contact load: 2700MPa 80mm
• Life requirement: 15 years in orbit
• Weight: < 1.5kg
133mm
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47. © VERHAERT SPACE
Tribology & wear-out of mechanisms
5-Make final decision on tribological solution
5.2- Solid/dry lubrication technology
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5.2.1 Self lubricating materials (polymers, bronzes…).
5.2.2 Surface treatments/coatings.
5.2.3 Ceramic materials.
5.2.4 Nano composite materials.
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Tribology & wear-out of mechanisms
5.2.3 Ceramic materials
Pro’s:
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• High hardness (limited wear)
• High youngs modulus (increase mechanism stiffness)
• Chemically inert
• Relative low density
• High temperature allowed
• Non magnetic
Con’s:
[Toyota full ceramic diesel engine
• Thermal mismatch with steel turbo charger]
• Low (limited) tensile strength > cracking
• Soft preloading to be applied in case of thermal mismatch (CTE)
• Boundary lubrication can be required (pump bearings)
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5.2.3 Ceramic materials (properties <> steel)
Aspects/property Bearing Ceramics Remark
steel (Si3N4)
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Density (kg/m³) 7800 3200 Lowers centrifugal force: allows high spindle
speeds in machines up to 35000 RPM
° 180 800 Maintains stability @ high temperature
Allowable temp.(°C)
CTE (ppm/ °C) 12.5 2.9- 3,2 Minimum deformation but thermal mismatch
with steel > cracks possible in hard preloaded
systems
Hardness (HV) 700 to 1400 to Reduced ball/race contact in ball bearings; less
800 1700 wear
Young's mod (GPa) 190-210 310 Less embedding & contact
Magnetic Ferromag Non Reduced torque in magnetic fields
netic magnetic
Corrosion Poor- OK Excellent Less wear; allows harsh environment; longer
resistance (pending life
on steel)
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5.2.3 Ceramic materials (typical application examples)
Milling machines [1]:
Ceramic bearings allow speeds up to 30000 RPM (25% ↑
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w.r.t. steel bearings) with a life increase of also 25%.
These use full cermaic bearings of SiN4 (better than ZrO2),
where the cage is PTFE, PEEK or phenolic.
Helicopters [2]:
Use through hardened stainless steel bearings with ceramic
coating of the races; the ball separator is made from
PTFE/glass composite (10X improved life w.r.t. full steel
bearings using a liquid lubricant.
[1]: Example: IBAG North America
[2]: Reported by Ampep, SKF aero-space
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5.2.3 Ceramic materials (bearing technology)
Ceramic hybrid bearings:
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These use ceramic balls (SiN, Al2O3 or Zr) on steel races.
Advantages w.r.t. full steel bearings:
• 40 % lighter than steel
• Three times stronger (load capability)
• Can run up to 4 times longer (SKF)
• Better corrosion resistance
• Less microwelding (vacuum applications)
• Less friction > bearings will run cooler
• Higher stiffness, more accuracy > smoother running & less vibrations
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5-Make final decision on tribological solution
5.2- Solid/dry lubrication technology
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5.2.1 Self lubricating materials (polymers, bronzes…).
5.2.2 Surface treatments/coatings.
5.2.3 Ceramic materials.
5.2.4 Nano composite materials.
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Tribology & wear-out of mechanisms
5.2.4 Nano composite materials
What are nanocomposites?
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• Material particles (of various constituent materials) mixed at the nanometre
scale (in matrix form).
How to create:
• PVD & CVD like processes > relatively expensive.
• Electro deposition (electrolysis) > nowadays cheapest
• Still in it’s infancy
Nanomaterials to support many applictions:
> http://www.qinetiq.com/home_nano/products.html
QinetiQ Nanomaterials Ltd (QNL) is Europe's leading manufacturer and
supplier of nanopowders and related technical services, providing a wide
range of nanometric products to an international client base.
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1. Select between wet and dry lubrication (working
conditions).
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2. Avoid a poor design, operation/functioning of your
mechanism.
3. Analyze/ assess contact loads/stresses, bending
stresses, …
4. Assess/analyze the wear aspects/phenomenon.
5. Make final decision on lubrication/ technology/
materials.
6. Performance of functional, friction/wear and life test.
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6-Functional/friction/wear and life test (1/4)
Overview of test/inspection
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We perform the following test/inspection (space applications):
→ Dedicated friction/wear test
→ Functional performance test in the applicable environment, like:
→ operating regime
→ temperature & pressure
→ loading
→ running-in test
→ Life test
→ Strip down and microscopic inspection
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Tribology & wear-out of mechanisms
6-Functional/friction/wear and life test (2/4)
Running in of a mechanism
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Typical friction profile in time as the basis to perform running-in.
Selection of running-in cycles and load: based on experience and above
plot.
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6-Functional/friction/wear and life test (3/4)
Example: running in of a gearbox
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0.05
0.04
0.03
0.02
0.01
0
0 20 40 60 80 100
Typical friction profile per cycle
Friction profile in time
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6-Functional/friction/wear and life test (4/4)
Friction and wear test
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Tribometer: pin on disc method is used to characterise friction & wear.
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Tribology & wear-out of mechanisms
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Verhaert New Products & Services nv
Hogenakkerhoekstraat 21
9150 Kruibeke
Belgium
Tel +32 (0)3 250 19 00
Fax +32 (0)3 254 10 08
www.verhaert.com
info@verhaert.com
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