Tribo-corrosion maps for engineering materials:some new perspectives

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Tribo-corrosion maps for engineering
materialssome new perspectives

• M.M. Stack
• Department of Mechanical Engineering
• University of Strathclyde
• Glasgow G1 1XJ, UK

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Looking for directions
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• Need a map..

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Information which a map may provide

• Landscape..
• Most convenient route between two locations
• Metrics

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Aims of presenation

• Can maps be used to guide materials engineers in
  materials processes involving tribological and
  aqueous corrosion processes.
• If so, how can we construct such maps.
• How may they be modified based on the nature of
  tribological contact and corrosive enviroment..

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Tribo-corrosion

• Wear due to the combination of tribological and
  corrosion parameters

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• Tribological-velocity, load, temperature,
  particle size, impact angle, yield strength.

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• Corrosion-pH, electrochemical potential, Cl-

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Wear map of steels for dry sliding
Lim and Ashby, 1987
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Wear map for Nimonic 80A vs. Stellite 6
Inman, Rose and Datta, Wear, 2006.
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Erosion-oxidation map for steels at elevated
temperatures
Sundararajan, 1990
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Corrosion map for Fe in H2O assuming passivation
by formation of Fe2O3
O
2
Passivation
Corrosion
H
2
E, volts (SHE)
Immunity
Corrosion
pH
Pourbaix, 1966
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Development of tribo-corrosion map in aqueous
conditions
Sliding wear map
Erosion-oxidation map
Tribo-corrosion map in aqueous conditions
Aqueous - corrosion map
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Format

• Why use a wear or a corrosion map?
• Some useful applications
• Development of tribo-corrosion maps-from erosion
  to micro-abrasioncorrosion

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Erosion-corrosion in aqueous conditions
Jana and Stack, 2004
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Example of surface failed by erosion-corrosion
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Polarization curve for Fe in aqueous media
p
o
t
e
n
t
i
a
l
,
E
Transpassive region
Passive region
E
p
Active region
ipass
icrit
l
o
g
i
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Possible interactions

• Erosion can enhance corrosion i.e. removal of a
  passive film
• Corrosion can inhibit erosion through formation
  of an adherent ductile film
• Corrosion can enhance erosion through dissolution
  of phases within the material-i.e. as in the case
  of MMCs

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Erosion-corrosion interaction 
Kec Ke Kc 
Keo ? Ke Kco ?Kc   Ke
Keo ? Ke  Kc Kco
?Kc  Kec Erosion- corrosion rate
(measured) Keo Erosion in the absence
of corrosion Kco Corrosion in
absence of erosion ?Ke Change in
erosion due to corrosion (synergistic effect) ?Kc
Change in corrosion due to erosion
(additive effect) Kc Total
corrosion rate (estimated using Faradays law)
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Erosion-corrosion rate
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Active Region
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Passive Region
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Erosion-Corrosion Regimes

• Erosion KC/KE ? 0.1
• Erosion-Corrosion 0.1KC/KE ? 1
• Corrosion-Erosion 1 KC/KE ? 10
• Corrosion KC/KE 10

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• Mechanism of wastage (landscape)...

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Erosion-corrosion map for Fe
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Fe at pH 7
Pourbaix diagram for Fe (SHE)
Erosion-corrosion map for Fe (SCE)
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Ni at pH 7
Pourbaix Diagram for Ni (SHE)
Erosion-corrosion map for Ni (SCE)
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Cu at pH 7
Pourbaix diagram for Cu (SHE)
Erosion-corrosion map for Cu (SCE)
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Al at pH 7
Pourbaix diagram for Al (SHE)
Erosion-corrosion map for Al (SCE)
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Comparison between erosion-corrosion regime maps
at pH 5
Fe
Ni
Cu
Al
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• Wastage rate (metrics)...

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Comparison between erosion-corrosion wastage maps
at pH 5
Ni
Fe
Cu
Al
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• Materials selection (decision on most convenient
  route...

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Comparison between materials performance maps at
pH 5
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Comparison between materials performance maps at
pH 9
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Erosion-corrosion of MMC Based materials
Abd-El-Badia and Stack, 2006-2007
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Erosion-corrosion rig
Based on design of Li, Burstein and Hutchings,
1990
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Erosion-corrosion mechanisms of MMC based
materials
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Erosion-corrosion interaction 
Kec Ke Kc 
Keo ? Ke Kco ?Kc   Ke
Keo ? Ke  Kc Kco
?Kc  Kec Erosion- corrosion rate
(measured) Keo Erosion in the absence
of corrosion Kco Corrosion in
absence of erosion ?Ke Change in
erosion due to corrosion (synergistic effect) ?Kc
Change in corrosion due to erosion
(additive effect) Kc Total
corrosion rate (estimated using Faradays law)
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Erosion-Corrosion Regimes

• Erosion KC/KE ? 0.1
• Erosion-Corrosion 0.1KC/KE ? 1
• Corrosion-Erosion 1 KC/KE ? 10
• Corrosion KC/KE 10

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Erosion-Corrosion Regimes

• ? KC/ ? KE ? 0.1 Synergistic
• 0.1? ? KC/ ? KE 1 Additive- Synergistic
• ? KC/ ? KE gt 1 Additive

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Erosion-corrosion mechanism maps
WC/Co-Cr coating
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Erosion-corrosion wastage maps
WC/Co-Cr coating
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Erosion-corrosion additive/synergistic effect maps
WC/Co-Cr coating
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Erosion-corrosion Materials Performance maps
4 ms-1 impact velocity
2 ms-1 impact velocity
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• Erosion-corrosion of cermets

Stack, Antonov and Hussainova, 2006
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Erosion-corrosion maps for cermets
SEM micrograph of surface of Ni-CR3C2 cermet with
40 wt. Ni. Potential - 500mV. Duration of test
1 hour.
Stack, Antonov and Hussainova, 2006
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Erosion-corrosion map showing the transition
between different wastage regimes for a Cr3C2-Ni
cermet
6
8
10
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Erosion-corrosion map showing the transition
between different additive regimes for a Cr3C2-Ni
cermet
6
8
10
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• Erosion-corrosion of PVD coatings

Purandare and Stack, 2004
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Erosion-corrosion of PVD coatings
3 um
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Micrographs of eroded coatings
3 um
6a
6b
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Erosion-corrosion mechanisms maps for coated and
uncoated materials
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Micro-abrasion-corrosion
Mathew and Stack, 2005
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Micro-abrasion corrosion apparatus
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Micro-abrasion
Dental environments
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Micro-abrasion
Artificial hip joints
Micro-abrasion process
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Experimental Details

• Sample Material mild steel
• Ball Material polypropylene (25 mm
  diameter)
• Speed 100 RPM
• Load 1-5N
• Slurry silicon carbide
  (4 ?m)
• Solution carbonate/bicarbonate
  (pH 9.8)

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Polarization curves in carbonate/bicarbonate
solution-no particles
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Polarization curves in carbonate/ bicarbonate
slurry
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Variation of Kac, Ka and Kc with increasing load
At -0.60 V
At -0.40 V
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Variation of Kac, Kc and Ka with increasing load
At -0.20 V
At 0 V
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Variation of Kac, Kc and Ka with increasing load
At 0.20 V
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SEM images of wear scar on mild steel
At 1N and 0.2 V
At 4N and 0.2 V
At 5N and 0.2 V
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AFM of un-abraded steel surface


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AFM of wear scar on mild steel at 1N and at 0.2
V

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• Micro-abrasion mechanisms

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Schematic diagram of micro-abrasion mechanisms
(i)
Surfaces in contact
3-body rolling
(iv) a
2-body Wear
Rolling
Mixed regime
(ii)
(iv) b
Oxide Film
2-body wear
(iii)
2 body grooving

Particle entrainment
2 body ridging
3-2 body
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Transitions between regimes for the
micro-abrasion process
3-2 Body
3-2 Body
2 Body ridging
Results from current study
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Wear-mode map for the micro-abrasion process
(Adachi and Hutchings, 2003)
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Micro-abrasion-corrosion interaction 
Kac Ka Kc 
Kao ? Ka Kco ?Kc   Ka
Kao ? Ka  Kc Kco
?Kc  Kac Micro-abrasion- corrosion
rate (measured) Kao Micro-abrasion in
the absence of corrosion (measured at 960
mV) Kco Corrosion in absence of
micro-abrasion ?Ka Change in
micro-abrasion due to corrosion ?Kc
Change in corrosion due to micro-abrasion Kc
Total corrosion rate (estimated using
Faradays law)
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Micro-abrasion-corrosion regimes

• Corrosion Kc/Ka
  gt 10
• Corrosion-micro-abrasion 10gt Kc/Ka gt 1
• Micro-abrasion-corrosion 1gt Kc/Ka gt 0.1
• Micro-abrasion Kc/Ka lt 0.1
• Corrosion? Active or passive conditions from
  polarization behaviour and Pourbaix diagrams
• Micro-abrasion? 3 or 2 body behaviour
  identified using theoretical models

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Micro- abrasion-corrosion mechanism map for mild
steel/polypropylene couple
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Comparison between micro-abrasion-corrosion maps
and polarization data
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Micro-abrasion corrosion wastage map for mild
steel/polypropylene couple
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Comparison between micro-abrasion-corrosion maps
and polarization data
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Comparison between micro-abrasion-corrosion maps
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Discussion

• Tribo-corrosion maps are a powerful tool for
  identifying materials degradation mechanisms
• Much work needs to be carried out on the
  theoretical development of the maps
• These maps have the potential to be the future
  mainstream engineering tools for addressing
  materials issues in such environments

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Fretting-Corrosion maps

• T.S.N. Sankara Narayanan, Y W. Park and K. Y.
  Lee Wear, 262,228-233 2007.

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Conclusions

• Progress has been made in recent years on the
  development of tribo-corrosion maps
• Maps for particulate erosion, sliding wear and
  micro-abrasion have been proposed in corrosive
  environments
• Such techniques have potential applications to a
  wide range of materials issues exposed to
  tribological and corrosive environments.

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Acknowledgements

• PhD students T. Abd-El-Badia, M. Antonov, B.D.
  Jana, M. Mathew, Y Purandare
• Collaborators P Hovespean, W. Huang, J Jiaren, I
  Hussaionova