Tribology of Ceramics in Different Environments

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Tribology of Ceramics in Different Environments
Tribology of Ceramics in Different
Environments
Andreas Kailer, Iyas Khader, Alexander Renz, Christof Koplin
Fraunhofer Institute for Mechanics of Materials IWM
Wöhlerstraße 11
79108 Freiburg
[email protected]
+49 761 - 51 42 2 47
www.mikrotribologiecentrum.de
© Fraunhofer-Institut für Werkstoffmechanik IWM
AGENDA
 Short introduction
 Motivation: Application
 Wear analysis in rolling contacts
 Tribological behavior in ceramic cutting tools
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Examples of current research topics
 Ceramics in cold and hot metalforming processes: New materials for
improved lifetime and wear resistant components
 Ceramic cutting tools: Towards the understanding of tribological
mechanisms in cutting operations
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Ceramic rolling tools
 Ceramic tools and components for the
fabrication of sheets, foils, wires and
profiles
Stahl
Si3N4
 Assessment of wear resistance and
lifetime
 Optimization of surface loading
capability
Si3N4
 Simulations (sintering, adhesion)
 Validation in industrial rolling
processes
 Benchmarks lifetime prolongation
were overmatched by a factor ~ 10
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Stahl
Ceramic materials and components for rolling mills
energy, resources
wear resistance,
mechanical and thermal
properties
tool lifetime
product quality
cost efficiency
energy consumption
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Ceramic rolling tools
 Ceramic tools and components for the
fabrication of sheets, foils, wires, profiles
Stahl
Si3N4
 Assessment of wear resistance and
lifetime
 Optimization of surface loading
capability
 Simulations (sintering, adhesion)
Si3N4
 Validation in industrial rolling processes
 benchmarks for lifetime prolongation
were overmatched by factor < 10
Stahl
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Rolling of metal foils
(Sendzimir mill, MK Metallfolien, Hagen)
work rolls
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Consortium
 Ceramic Manufacturers
 Machining
 Research institutes
 Industry
…
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Tribological behaviour of new ceramic materials
Aim:
Improve wear resistance and high
temperature strength
• New material variations
• Influence of cooling lubricants
Ra: 0,08 μm, Rz: 0,15-0,2 μm
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Wire rolls
Hot Rolling of Copper
Hot rolling of steel and Ni-base
alloys
Wire temperature ~840C,
Velocity ~2 m/s, cooling lubricant
Wire temperature ca. 1050C,
velocity ~10 m/s, cooling lubricant
Si3N4
rolls
Medianriss
Bild: Böhler Edelstahl
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Ceramic guiding rolls
Surface smoothening
10 times higher lifetime
Steel rolls: 60 t wire
Ceramic rolls: > 600 t
new
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after service
Tribochemical wear: Copper wire rolling
(A. Hashibon, J.-M. Albina, FhG IWM)
System
Work of separation (Wsep)
[J/m²]
Cu (111) / -Fe (111)
4.00
Cu (111) / -Si3N4 (0001)
2.72
Cu (111) / -SiO2 (0001)
4.10
Cu (111) / [Cu ML , -Fe (111)]
3.30
Cu (111) / Cu (111)
3.08
ML: monolayer
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Cu / α-SiO2
Tribochemical wear: Copper wire rolling
Si3N4
High T, P + Sliding
SiO2
High adhesion affinity
SiO2
Cu
Tribological contact
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Delamination of
low shear-strength
oxide layers
Multiscale simulation to model degradation in
ceramic components
EU-Project (2011 – 2014): IWM, KIT, IPM, ISFK, SKF, Böhler Edelstahl, FCT
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Component testing: Wire rolling test rig
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Tribochemical wear and wire rolling
Ceramic rolls: Si3N4 - SL200 BG (oval-profile caliber)
Wire: Steel 1.4310
Rolling temperature: ~900°C
Reduction: 0.3
Lubrication: Cooling lubricant (5% emulsion in water)
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Tribochemical wear: Hot rolling of high strength steel
SL200 BG
Ra = 0,04 ± 0,01 µm
Ra = 0,12 ± 0,02 µm
Rz = 0,11 ± 0,05 µm
Rz = 0.90 ± 0,10 µm
Polished surface
After 3000m at 900°C
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Virgin state
Hot rolling of high strength steel
Surface shear stresses in wire rolling
Complex sliding contact conditions in the deformaiton zone
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Hot rolling of high strength steel
virgin
5000m
0
Contour depth (µm)
-100
-200
-300
-400
-500
y = 5.2 µm
-600
0
500
1000
1500
2000
2500
Traversal distance (µm)
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3000
3500
4000
Hot rolling of high strength steel
-1.16
2
Area (mm )
-1.17
-1.18
-1.19
-1.20
0
1000
2000
3000
4000
Amount of rolled wires (m)
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5000
Damage Characteristics  Reliability
microcrack formation an growth due to mechanical contact stresses
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Damage Models
Mechanical stresses
tensile stresses
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shear stress
Wear simulations
Experiments: Quantification of wear parameters
FE-Simulations: Stress state corresponding to modified contact conditions
Wear
parameters
FEM wear simulation
Local geometry
variations 
modified stress
state
Contact profile
Experiments
Simulations
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Wear measurement
500 μm
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Wear Simulation
t = 1800 s
t = 2700 s
t = 3600 s
t = 5400 s
t = 7200 s
t = 9000 s
t = 10800 s
0.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
-2.0
-4.0
Profile depth (µm)
-6.0
~3.0 GPa
-8.0
-10.0
~2.0 GPa
-12.0
-14.0
-16.0
-18.0
-20.0
~1.4 GPa
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Traversal distance (mm)
2.5
Ceramic Gears
Bornemann Pumps GmbH
reliability
lifetime
Contact pressure
Tensile stress
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Incremental slip
Ceramics at High Temperature: Wear Mechanisms and
Residual Stress Formation in Ceramic Cutting Tools
 Motivation: Understanding the wear mechanisms of ceramic cutting tools
 Examination of degradation mechanisms of ceramic cutting tools
 Chemical wear
 Mechanical wear
 Residual stress formation
 Model experiments
 High temperature wear analysis
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Ceramic Cutting Tools
 Ceramic cutting tools for
high-speed-machining of
high-temperature alloys
 Cutting speeds ≤ 1000 m/min
cause extreme temperatures
at cutting edges
 Temperature gradients and
cutting forces affect tool
wear significantly
 Improved wear resistance by
adjustment of material
composition and morphology
 Detailed analysis of structural
and chemical interface
transformations necessary
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Typical wear marks on used cutting tools
Materials:
-SiAlON
Al2O3/SiCw
Kennametal KY4300
Intact area
at flank
Kennametal KY1540
Built-up phase
at cutting edge
Al2O3/AlN
vc
500 μm
Fraunhofer IPK
vc
SiAlON
500 μm
Fraunhofer IPK
Selective wear of Si3N4:
Formation of amorphous Al2O3 and AlN layer
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Mechanical wear of Al2O3/SiC
Ni-based alloy
Metal filled
voids of
removed
SiC-whiskers
Growth of crack
network under
cyclic load
Flank
Cutting edge
Al2O3/SiC
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Analysis of built-up layer on SiAlON
N
O
Al
Si
Ni
Hf
2.9
53.8
30.0
0
0.2
13.1
Hf
39.1
9.0
6.1
42
0.5
3.3
45.5
4.0
8.4
41.1
0.9
0.2
(in at%)
Assumption:
Hafnia (HfO2) and Alumina (Al2O3) built up on the tool surface
by diffusion of alloying Hf and by flow of SiAlON glass phase
 Depletion of underlying microstructure
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Metal oxide
Static interaction couple: Sialon on Ni-base alloy (MAR
M247)
Al(O,N)
Co, Si, Ni
Cr, Co, Si, Ni
W, Ti, Hf, Si, Al
F
Fraunhofer IKTS
Chemical/diffusive surface reactions after 1 h at low contact pressure
(17.5 MPa) and high temperature (1300 °C, air)
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Specimens and experimental setup
 Simplification of specimen geometry and load situation
 Normal force:
FN = 50 N
 controlled Laser
heating, T = 800 °C
 Rotation speed:
vcut = 30 m/min
 Experiment
 Schematic of a worn sample:
New flank
Worn flank
Cutting edge
cracks
Rake face
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Summary
Bulk material
Degradation zone
Built-up phase
Nickel-base alloy
Embedding material
Surface fatigue and
chipping
Adhesive interaction of tool
and workpiece material
Tribo-chemical degradation
and transformation
 Temperature induced tribochemical wear was observed in both ceramics
 Reactivity of commercial SiAlON with Hf-containing alloys
 Degradation of SiC at high temperatures
 Subsurface layers show fatigue cracks and residual stresses
 Wear rate and coefficient of friction of ceramic tools decrease with rising
temperature
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