RF9
Physics of Failure
Sliding contact phenomena
Material related failure
RF9 Program Day 2
9:00-9:15
Introduction
9:15-9:30
Friction related failures
9:30-10:00
Demo load capacity of sliding contacts
10:00-10:15
Break
10:30-11:30
11:30-11:45
PoF Friction
Application of gained results
11:45-12:30
PoF Wear
12:30-13:30
Lunch
13:30-14:00
Demo Dry Sliding and EP additives
14:00-15:00
PoF Material selection 
15:00-15:15
Break
15:15-16:15
PoF Lubrication
16:15-16:45
Application of gained results
16:45-17:00
Summary of the day
2013
RF9 - Physics of Failure
slide 2
Material & Coating Selection
2013
Adv Eng Design Page 222
RF9 - Physics of Failure – Material Selection
slide 3
Case study Storm surge Barrier
A movable storm surge barrier is constructed
making dikes along the river unnecessary.
2013
Adv Eng Design Page 222
RF9 - Physics of Failure – Material Selection
slide 4
Case study Storm surge Barrier
F=35.000 Metric Tonnes Load
m=15.000 Metric Tonnes Load
p<150 MPa
µ<0.1
Material selection ?
2013
Adv Eng Design Page 222
RF9 - Physics of Failure – Material Selection
slide 5
Material & Coating Selection
7.1 Materials in relative sliding
Metals, polymers, technical ceramics
7.2 Coatings and surface treatments
Surface treatments and classification
7.3 Material selection
Case study: storm surge barrier
2013
Adv Eng Design Page 222
RF9 - Physics of Failure – Material Selection
slide 6
Material Selection: Metals
steel, bronze, cast iron…
2013
Adv Eng Design Page 249
PF9 - Physics of Failure – Material Selection
slide 7
Material Selection: Metals
Why metal-metal combinations are always lubricated.
Without lubrication:
Without lubrication
Severe adhesive friction / adhesive wear
Metals of relative high hardness:
+ Relative good wear resistance
(class 4)
- High friction, scatter
(µ=0.3...0.6)
2013
Adv Eng Design Page 249
Metals of relative low hardness:
+ Relative low friction
(µ=0.08...0.14)
- High wear rate
(class 6)
RF9 - Physics of Failure – Material Selection
slide 8
Case 1
2013
Seminar - Physics of Failure
slide 9
Material Selection: Metals
How to reduce friction and wear due to adhesion
 Combinations of a non-metal against a metal
 Carburizing or nitriding
 High hardness of both surfaces
 Difference in hardness of a factor between 3 to 5
 High roughness
 Strong oxide film
 Lubricant, liquid or solid
 Thin layer with low shear strength.
2013
Adv Eng Design Page 169
RF9 - Physics of Failure – Material Selection
slide 10
Material Selection: Metals
How to reduce friction and wear due to adhesion
 Combinations of a non-metal against a metal
 Carburizing or nitriding
 High hardness of both surfaces
 Difference in hardness of a factor between 3 to 5
 High roughness
 Strong oxide film
 Lubricant, liquid or solid
 Thin layer with low shear strength.
2013
Adv Eng Design Page 169
RF9 - Physics of Failure – Material Selection
slide 11
Material Selection: Polymers
q  Ff v   F v
q / A   pv,
A  Ld
Tc  T0  q R
pv 
Tc .m ax  T0
 RA
µ(p,v)
2013
Adv Eng Design Page 209
Dependent on
heat conduction
RF9 - Physics of Failure – Material Selection
slide 12
Material Selection: Polymers
Polymers
• Thermoplastics
two types of thermoplastics
- crystalline
- amorphous
• Thermosets
cannot be reshaped by heating
are stiff and strong in relation to thermoplastics
are often reinforced with glass or carbon fibers
• Elastomers
rubbery polymers, can stretch easily and instantly
return to its original shape when released.
2013
Adv Eng Design Page 309
RF9 - Physics of Failure – Material Selection
slide 13
Material Selection: Polymers
Thermoplastics
+ Do not need to be lubricated
+ Low weight
+ Injection molding
- Low stiffness and strength
- Mechanical properties strongly depend on temp
- Poor heat conduction, large thermal expansion
- Large machining tolerances
2013
Adv Eng Design Page 309
RF9 - Physics of Failure – Material Selection
slide 14
Material Selection: Polymers
2013
Adv Eng Design Page 253
RF9 - Physics of Failure – Material Selection
slide 15
Material Selection: Polymers
Amorphous plastics
+ Less mold shrinkage
- Susceptible to chemical attack
- Lower wear resistance
Crystalline plastics
+ Higher strength and rigidity
+ Higher wear resistance
+ Good chemical resistance to oils and grease
(silicone based oils, water, soap…)
2013
Adv Eng Design Page 253
RF9 - Physics of Failure – Material Selection
slide 16
Material Selection: Polymers
price
2013
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RF9 - Physics of Failure – Material Selection
slide 17
Material Selection: Polymers
2013
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RF9 - Physics of Failure – Material Selection
slide 18
Material Selection: Polymers
Self lubricating plastics are compounded with
- PTFE, MoS2, Graphite, Silicone oil, Aramid fibres
Fiber reinforced plastics are reinforced with
- Glass fibers, Carbon fibers
Steel counter surface
- HRc>50, Ra=0.3-0.4 μm
Aramid fibers
- Improves resistance to abrasion especially against
counter surfaces of lower hardness such as
aluminum and plastics.
2013
Adv Eng Design Page 260
RF9 - Physics of Failure – Material Selection
slide 19
Material Selection: Polymers
2013
Adv Eng Design Page 258, 261
RF9 - Physics of Failure – Material Selection
slide 20
Case 2
Bronze
St.50
(1.0050)
Pmax=10…20 MPa
Pmax=5…10 MPa
Failure mode:
2013
Adv Eng Design Page 222
RF9 - Physics of Failure – Material Selection
slide 21
Material Selection: Metals
How to reduce friction and wear due to adhesion
 Combinations of non-metals or a non-metal against a metal
 Carburizing or nitriding
 High hardness of both surfaces
 Difference in hardness of a factor between 3 to 5
 High roughness
 Strong oxide film
 Lubricant, liquid or solid
 Thin layer with low shear strength.
2013
Adv Eng Design Page 169
RF9 - Physics of Failure – Material Selection
slide 22
Material Selection: Metals
How to reduce friction and wear due to adhesion
 Combinations of non-metals or a non-metal against a metal
 Carburizing or nitriding
 High hardness of both surfaces
 Difference in hardness of a factor between 3 to 5
 High roughness
 Strong oxide film
 Lubricant, liquid or solid
 Thin layer with low shear strength.
2013
Adv Eng Design Page 169
RF9 - Physics of Failure – Material Selection
slide 23
Material Selection: Metals
Difference in hardness of a factor between 3 to 5
 Less tendency to adhesion (Pb, Sn)
 Good embed ability for abrasive particles
 Leveling out of stress concentrations
2013
Adv Eng Design Page 250
RF9 - Physics of Failure – Material Selection
slide 24
Material Selection: Metals
Main bearing
Marine bearing
2013
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RF9 - Physics of Failure – Material Selection
slide 25
Material Selection: Metals
Elastic support
Porous bearing
Oil circulation within the pores
2013
Adv Eng Design Page 210
RF9 - Physics of Failure – Material Selection
slide 26
Material Selection: Metals
Porous iron
2013
Adv Eng Design Page 222
RF9 - Physics of Failure – Material Selection
Hardened
shaft
slide 27
Material Selection: Metals
Porous bronze (PbSn)
bearings
μ=0.06-0.10, k=0.3-0.9 10-15 m2/N, PV=1.75 106 Pa·m/s
2013
Adv Eng Design Page 222
RF9 - Physics of Failure – Material Selection
slide 28
Case 3
2013
Adv Eng Design Page 306, 35, 221
RF9 - Physics of Failure – Material Selection
slide 29
Material Selection: Metals
How to reduce friction and wear due to adhesion
 Combinations of non-metals or a non-metal against a metal
 Carburizing or nitriding
 High hardness of both surfaces
 Difference in hardness of a factor between 3 to 5
 High roughness
 Strong oxide film
 Lubricant, liquid or solid
 Thin layer with low shear strength.
2013
Adv Eng Design Page 169
RF9 - Physics of Failure – Material Selection
slide 30
Material Selection: Metals
How to reduce friction and wear due to adhesion1) :
 Combinations of a non-metal against a metal
 Carburizing or nitriding
Layered molecular
 High hardness of both surfaces
structure of graphite
 Difference in hardness of a factor between 3 to 5
 High roughness
 Strong oxide film
Stainless
 Lubricant, liquid or solid 
steel
 Thin layer with low shear strength
Thin oxide layer
Stainless steel bolts require special purpose lubricants
2013
Adv Eng Design Page 169
RF9 - Physics of Failure – Material Selection
slide 31
AF-Coating
(MoS2, graphite)
Case 3
Layered molecular
structure of graphite
Successful application in
clearance fits to prevent
fretting corrosion (left) or
galling (right)
2013
Adv Eng Design Page 306, 35, 221
RF9 - Physics of Failure – Material Selection
slide 32
Material Selection: Metals
AF-Coating, P>100MPa, µ<0.1
Particle orientation after initial sliding
Layered molecular
structure of graphite
AF-Coating
(MoS2, graphite)
Successful application in
screw joints
2013
Adv Eng Design Page 306
RF9 - Physics of Failure – Material Selection
slide 33
Material Selection: Metals
Layered molecular
structure of graphite
2013
Adv Eng Design Page 309
RF9 - Physics of Failure – Material Selection
slide 34
Material Selection: Metals
How to reduce friction and wear due to adhesion1) :
 Combinations of non-metals or a non-metal against a metal
 Carburizing or nitriding
 High hardness of both surfaces
 Difference in hardness of a factor between 3 to 5
 High roughness
Galvanized
 Strong oxide film
 Lubricant, liquid or solid
 Thin layer with low shear strength 
High corrosion
resistance
2013
Adv Eng Design Page 169
RF9 - Physics of Failure – Material Selection
slide 35
Material Selection: Metals
How to reduce friction and wear due to adhesion
 Combinations of a non-metal against a metal
 Carburizing or nitriding
 High hardness of both surfaces
 Difference in hardness of a factor between 3 to 5
 High roughness
 Strong oxide film
 Lubricant, liquid or solid
 Thin layer with low shear strength.
2013
Adv Eng Design Page 169
RF9 - Physics of Failure – Material Selection
Case 4
slide 36
Material Selection: Tech. Ceramics
Al2O3
SiC
Si3N4
ZrO2
ZTA
= Alumina
= Silicon Carbide
= Silicon Nitride
= Zirconia
= Zirconia Toughened Alumina
+ High hardness and wear resistance
+ Low specific weight
+ Excellent high temperature properties
+ Resistance to corrosive environment
- Low toughness (brittle)
2013
Adv Eng Design Page 267
RF9 - Physics of Failure – Material Selection
slide 37
Material Selection: Tech. Ceramics
2013
Adv Eng Design Page 151
RF9 - Physics of Failure – Material Selection
slide 38
Material Selection: Tech. Ceramics
+ High resistance to abrasive wear (elastic deformation)
+ High resistance to adhesive wear (small γ/H ratio)
High surface energy but small ratio of
surface energy and hardness
2013
Adv Eng Design Page 151
 ~H
1/3
RF9 - Physics of Failure – Material Selection
slide 39
Material Selection: Tech. Ceramics
Hydrodynamic bearing operating
in abrasive environment (Pavg= 6 MPa)
2013
Adv Eng Design Page 266
RF9 - Physics of Failure – Material Selection
slide 40
Material Selection: Tech. Ceramics
Jewel bearings
Industrial jewels
Diamond pivots
2013
Adv Eng Design Page 504, 523
RF9 - Physics of Failure – Material Selection
slide 41
Case 5
2013
Adv Eng Design Page 169
RF9 - Physics of Failure – Material Selection
slide 42
Material Selection: Metals
How to reduce friction and wear due to adhesion
 Combinations of non-metals or a non-metal against a metal
 Carburizing or nitriding
 High hardness of both surfaces
 Difference in hardness of a factor between 3 to 5
 High roughness
 Strong oxide film
Case 5
 Lubricant, liquid or solid
 Thin layer with low shear strength.
2013
Adv Eng Design Page 169
RF9 - Physics of Failure – Material Selection
slide 43
Material Selection: Coatings & surface treatments
Bonding strength
2013
Adv Eng Design Page 269
RF9 - Physics of Failure – Material Selection
slide 44
Material Selection: Coatings & surface treatments
2013
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RF9 - Physics of Failure – Material Selection
slide 45
Material Selection: Coatings & surface treatments
Advantage of dissimilar materials
(Metallurgical incompatible materials).
2013
Adv Eng Design Page 268
RF9 - Physics of Failure – Material Selection
slide 46
Material Selection
Introducing residual compressive stresses
up to half the yield strength in order to
improve the fatigue strength.
Laser peening imparts a layer of compressive
stress that is four times deeper than that
attainable from conventional shot peening
2013
Adv Eng Design Page 273
RF9 - Physics of Failure – Material Selection
slide 47
Material Selection: Coatings & surface treatments
2013
Adv Eng Design Page 268
Nickel and
chromium plating
PF9 - Physics of Failure – Material Selection
slide 48
Material Selection: Coatings & surface treatments
Laser cladding
Laser cladding is an effective way to refurbish and
improve worn or damaged industrial components
2013
Adv Eng Design Page 268
RF9 - Physics of Failure – Material Selection
slide 49
Material Selection: Coatings & surface treatments
Pre-machining: removal of
worn and with lubricant
diffused material
Substrate low alloyed
C-steel, Clad material
Stellite 21
Post-machining to
required
dimensions
2013
Adv Eng Design Page 273
RF9 - Physics of Failure – Material Selection
slide 50
Material Selection: Coatings & surface treatments
HVOF Spraying
Al2O3
TiO2
WC
2013
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RF9 - Physics of Failure – Material Selection
slide 51
Material Selection: Coatings & surface treatments
CVD -TiN
2013
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RF9 - Physics of Failure – Material Selection
slide 52
Material Selection: Coatings & surface treatments
2013
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RF9 - Physics of Failure – Material Selection
slide 53
Material Selection: Coatings & surface treatments
Adhesive wear
(Galling)
DLC coatings in sheet
metal forming, µ<0.1
2013
Adv Eng Design Page 268
RF9 - Physics of Failure – Material Selection
slide 54
Material Selection: Coatings & surface treatments
2013
Adv Eng Design Page 275, 276
RF9 - Physics of Failure – Material Selection
slide 55
Material Selection: Coatings & surface treatments
Summary
• The wear resistance of a machine part
+ hard surface
is determined by the wear resistance
+ tough core
of it’s surface.
• This means that for the surface other demands
can be made than for the bulk material
• There are plenty of options to improve the surface quality
• Treatments in the surface / on the surface
2013
Adv Eng Design Page 275, 276
RF9 - Physics of Failure – Material Selection
slide 56
Half of the Netherlands is below
Case study Storm surge Barrier
sea level. To prevent flooding
dikes along the coast line are
raised to delta level.
Raising the dikes along the river
are unwanted and would be very
expensive. A dam isn’t possible
while the seaport of Rotterdam
must remain accessible.
Adv Eng Design Page 275, 276
Adv Eng Design Page 275, 276
Adv Eng Design Page 275, 276
Adv Eng Design Page 275, 276
Adv Eng Design Page 275, 276
Adv Eng Design Page 275, 276
Adv Eng Design Page 275, 276
Adv Eng Design Page 275, 276
Adv Eng Design Page 275, 276
Adv Eng Design Page 275, 276
Adv Eng Design Page 275, 276
Case study Storm surge Barrier
F=35.000 tonnes
m=15.000 tonnes
p<150 MPa
µ<0.1
Material selection ?
2013
RF9 - Physics of Failure – Material Selection
slide 68
Case study Storm surge Barrier
The allowable pressure in sliding contacts between metals
is limited by seizure
 Steel – cast iron 5…10 MPa, μ=0.12…0.18
 Steel - CuSn or CuAl alloys 10…20 MPa, μ=0.12…0.18
In screw joints contact pressures up to
100 MPa are common, but the sliding
motion is limited to one single move and
μ=0.12…0.18
2013
Zinc plated to prevent
corrosion and seizure.
RF9 - Physics of Failure – Material Selection
slide 69
Solid lubricants
AF-Coating, P>100MPa, µ<0.1
Particle orientation after initial sliding
Layered molecular
structure of graphite
AF-Coating
(MoS2, graphite)
Successful application in
screw joints
2013
Adv Eng Design Page 306
RF9 - Physics of Failure – Material Selection
slide 70
Case study Storm surge Barrier
Solid lubricants are used for conditions where
conventional lubricants are inadequate






Reciprocating motion, fretting
Improvement of running in conditions
Extreme contact pressures
Shock loading
High temperatures
Ceramics
2013
Adv Eng Design Page 309
RF9 - Physics of Failure – Material Selection
slide 71
Case study Storm surge Barrier
P<150MPa, µ<0.1
2013
Adv Eng Design Page 307
PF9 - Physics of Failure – Material Selection
slide 72
Case study Storm surge Barrier
What to do?
High maintenance costs
Adhesive wear
between casting
steel parts
How to prevent
failure µ>0.1?
2013
RF9 - Physics of Failure – Material Selection
slide 73
Case study Storm surge Barrier
The problem:
High maintenance costs (wear by seizure)
The challenge:
Find a tribo system (material combination)
that sustains high contact pressures in sliding motion and
show minimal friction and minimal wear.
The solution: ?
2013
RF9 - Physics of Failure – Material Selection
slide 74
Case study Storm surge Barrier
The solution: ?
Only limited possibilities to modify the realized construction.




2013
Alternative lubricant or coating system?
Boundary Lubricated metal - metal contacts p<20MPa, µ>0.1
Thermoset – metal contacts p<150 MPa, µ>0.1
Polymer – metal contacts p<10 MPa, µ<0.1
RF9 - Physics of Failure – Material Selection
slide 75
Case study Storm surge Barrier
Coulombs law:
If the load is doubled the friction is doubled.
Not for polymers!
Polymer – metal contacts only for limited contact pressure?
2013
RF9 - Physics of Failure – Material Selection
slide 76
Case study Storm surge Barrier
Cast steel with epoxy coating
UHMWPE
Cast steel
Carbon fiber
PE against epoxy resin, p>150 MPa, µ=0.02…0.06
F > 7000 kN (700 tonnes).
2013
RF9 - Physics of Failure – Material Selection
slide 77
Case study Storm surge Barrier
2013
PF9 - Physics
of Failure cutter
– Material Selection
Testing
of a special engineered
turning
slide 78
2013
RF9 - Physics of Failure – Material Selection
slide 79
500 holes in each ball joint
2013
RF9 - Physics of Failure – Material Selection
slide 80
2013
PF9 - Physics of Failure – Material Selection
slide 81
Case study Storm surge Barrier
Summary
The problem:
High maintenance costs (wear by seizure)
The solution: Polymer discs, expansion blocked by
carbon fiber rings, sliding against epoxy coated steel surface.
Performance: Contact pressures up to 150 MPa,
coefficient of friction μ < 0.05, lifetime > 5 km sliding distance,
maintenance limited to overhauling of the epoxy coating
after a large number of moves.
2013
RF9 - Physics of Failure – Material Selection
slide 82
Material Selection
Summary
• Several different material combinations have been
discussed with respect to their applications.
• Metals, metal alloys, thermoplastics, thermosets,
ceramics and many coatings or surface treatments.
• There is not an ideal material combination for
sliding contacts in general.
• In machine design metal-metal combinations are
common and it is demonstrated that these combinations
need to be lubricated.
2013
RF9 - Physics of Failure – Material Selection
slide 83
RF9 Program Day 2
9:00-9:15
Introduction
9:15-9:30
Friction related failures
9:30-10:00
Demo load capacity of sliding contacts
10:00-10:15
Break
10:30-11:30
11:30-11:45
PoF Friction
Application of gained results
11:45-12:30
PoF Wear
12:30-13:30
Lunch
13:30-14:00
Demo Dry Sliding and EP additives
14:00-15:00
PoF Material selection
15:00-15:15
Break
15:15-16:15
PoF Lubrication
16:15-16:45
Application of gained results
16:45-17:00
Summary of the day
2013
RF9 - Physics of Failure
slide 84