Lesson 2
2014
Lesson 2
2014
 Our goal is, that after this lesson, students
are able to recognize the importance of
affecting wear and corrosion phenomena for
material selection.
Note!
 To ensure proper material selection it is
important to recognize the affecting
wear phenomenon/ phenomena!
ADHESIVE
WEAR
TRIBOCHEMICAL
WEAR
WEAR
PHENOMENA
ABRASIVE WEAR
FATIGUE
WEAR
Note!
 Different wear phenomena can affect
simultaneously
 Different wear phenomena can affect
consecutively (they can form “chains” of
wear phenomena)
 Numerical values of wear resistance are
required to compare the wear resistance of
optional materials objectively!
- Lubricated
- Non-lubricated
- Self lubricated
- Oil
- Crease
MATERIAL
PAIR
- HD
- EHD LUBRICATION
- Border CONDITIONS
- Mixed
- Slow speed
- High speed
- Continuous
- Cyclic
SURFACE
ROUGHNESS
MEDIA
TYPE OF
MOTION
WEAR
Main
aspects in
material
selection
- Adhesive
WEAR
- Abrasive
PHENOMENA - Fatigue wear
- Tribochemical
wear
ENVIRONMENTAL
CONDITIONS
ADHESIVE WEAR
Surface 1
MOTION
A surface peak
cold welds with
the surface peak
on the opposite
surface.
Surface 2
ABRASIVE WEAR
MOTION
Surface 1
Harder
A harder abrasive
particle wears the
softer surface.
Surface 2
Sowter
TRIBOCHEMICAL WEAR
FATIGUE WEAR
Carburized steel 20NiCrMo 5
Polymer PA6.6
FRICTION
COEFFICIENT
µ
FRICTION
COEFFICIENT
µ
PA 6.6
1
1
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
50
PA 6.6 + 15% PTFE
0
150
250
T [ºC]
TEMPERATURE
50
150
250
T [ºC]
TEMPERATURE
Centrifugal cast bronze
GZ-CuZn12
Carburized steel
16MnCr5
Heavy loads
Wear
resistance
increases
Small loads
Heavy loads
Thermal
coatings
WC/Co
Wear
restistance
increases
Thick
CrC
Thermal coatings
ceramic CrN
WC/Co
coatings
Plasma coating
Borium steels
Oxidation:Cr, Al
Nitritized steels
CrC, CrN
Thin ceramic coatings
Carburized
steels
Nitridized steels
Carburized steels
Austenic
stainless
steels
Small loads
Wear
resistance
steels are
utilized e. g. in
crane rails.
Bearing steel
100Cr6
STRENGTH OF ADHESIVE REACTION
Cr
Ni
Fe
Ti
Cu
Al
Zn
Mg
Sn
Pb
In
In
Pb
Sn
Mg
Zn
Al
Cu
Ti
Fe
Highly intensive adhesive reaction
Ni
Fairly intensive adhesive reaction
Cr
No adhesive reaction
 Archard’s equation : V =ki×F × s
V
= material loss due to wear
 ki = material pair coefficient
 F = affecting perpendicular force against the
surface
 s = motion distance
 The criterion for wear resistance comparison is
the material pair coefficient ki
 Advanced equations: V =Ki×SC2 × RC3
 V
 S
 R
 Ki , C2,C3
= material loss due to wear
= contact stress of the components
= number of loading cycles
= coefficient describing the material pair, surface roughness
and loading case
 Advanced equation takes care of the effect of
surface profile s and cyclic loading on wear
 Remember that sometimes the friction
coefficient between the materials gives a
measureable value for possible wear rate!
Note!
 To ensure proper material selection it is important
to recognize the affecting corrosion phenomenon!
 It is also necessary to take care of other
simultaneous loading conditions with corrosion,
such as tensile stress, temperature or wear!
 Numerical values are needed to evaluate and
compare objectively the corrosion resistance of
each optional material. See e.g. standards ISO 9223
and ISO 9224 for the corrosion speed of steels.
C
O
R
R
O
S
I
O
N
P
H
E
N
O
M
E
N
A
Surface
corrosion
Uniform corrosion
Pitting corrosion
Localized corrosion
Crevice corrosion
High-temperature
corrosion
Galvanic corrosion
Contact
corrosion
Mechanical surface
loading
Erosion
Cavitation
Fretting
Corrosion
under stress
loading
Selective
corrosion
Stress corrosion
Corrosion fatigue
Intergranular corrosion
Bronzes
Selective leaching
Cast irons
UNDER THE
GASKET THERE IS
THE RISK BOTH
OF WEAR AND
CORROSION
EXAMPLE OF CRACK AND GALVANIC CORROSION
ALUMINIUM BODY
MW-FILTER
FITTING
BASED ON
CLEARANCE
RESONATOR PINS
GOLD
COATED
CENTRE
PIN
SMACONNECTOR
FRETTING CORROSION
Clearance
in fitting
H6/m6
H6
Bearing
assembly
m6
STRESS
σ
FATIGUE WITHOUT CORROSION
ENDURANCE LIMIT
N
NUMBER OF
LOAD
CYCLES
MATERIAL
PAIR
CORROSION
PHENOMENON
TEMPERATURE
STRESS
CONDITIONS
CHEMICAL
ENVIRONMENTAL
CORROSION
Aspects to
affect material
selection
- Uniform corrosion
- Localized corrosion
- Galvanic corrosion
- Erosion and cavitation
- Fretting
- Intergranular corrosion
- Selective leaching
- Stress corrosion
- Corrosion fatigue
- Coating
MANUFACTURING - Casting
TECHNOLOGY
- Painting
Steel pipes in energy transportation
CABLE JOINT
STEEL/STAINLESS STEEL
COATED POLYMERS
ALUMINIUM ALLOYS
COPPER ALLOYS
SURFACE CORROSION OF THE HUB IN A CABLE JOINT
Note!
 It is not enough to ”select” stainless steel to avoid
corrosive damages! There are four different types of
stainless steels and they have totally different
application areas:
 Austenitic stainless steels
 Martensitic stainless steels
 Ferritic stainless steels
 Duplex steels
CORROSION VELOCITY 10x µm/YEAR
CONDITIONS
x
COUNTRY SIDE
SEASIDE
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
A
B
C
D
A
B
C
D
A = AUSTENITIC STAINLESS STEEL
B = FERRITIC STAINLESS STEEL
C = ZINC COATED STEEL
D = CARBON STEEL