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TribologyinMechanicalEngineering
MAE493N/593T
Dr.Konstantinos
A.
Sierros
WestVirginiaUniversity
Mechanical&AerospaceEngineering
ESBAnnex
263
[email protected]
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Coursematerial
Youcanreadanddownloadcoursematerialfromthefollowingblog;
http://wvumechanicsonline.blogspot.com
ehandoutswillbealsouploadedintheblog
Pleaseprintresponsibly!
http://wvumechanicsonline.blogspot.com/http://wvumechanicsonline.blogspot.com/
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Arough
surface
has
the
profile
illustrated
in
the
above
figure.
Sketch
the
form oftheprobabilitydensityfunctionandevaluatetheRq
intermsofthe
dimension.Whatarethevaluesoftheskewness
andkurtosisofthis
surface?
Inclassactivity
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Physicalnatureofmetallicsurfaces
Metal
surfaces
exposed
to
air
absorb
O2
and
H2
O
vapour and
form
metal
oxide
(MO)
layers
Noblemetals(notveryreactive!):12atomsthickMOlayer
Morereactivemetals:Thickerlayers
Rateof
growth
of
MO
films
depend
on:
Crystallographicorientationofunderlyingmaterial
Temperature(veryimportant!);Hightemperatureincreasesgrowthrate
Hightemperature:Nucleiisformed;Thencrystalsareformed;Roughersurfaces
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Examples
Iron
surfaces
can
form
oxide
layer
which
is
a
mixture
of
various
oxides
of
Fe
Cu
Cu2
O
CuO
Coppersurface
2ormoredifferent
layers
Cuprousoxide
Cupricoxide
Alloysurfaceswhenexposedtoairformamixtureofdifferentoxidesina
singlelayer
Forstainlesssteelalloy,amixtureofFeandCroxideformon
thesurface
andtheCroxideprovidesthecorrosionprotection
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MObeneficial?
In
some
cases
they
are.
The
surface
becomes
passivated
(no
further
chemical
activity).
ExamplesincludeAlandTi
ButinsomeothercasestheMOlayerhasanopenmicrostructure
soO
2
diffusioncontinues Oxidesofironareaprimeexample
http://www.chem1.com/acad/webtext/elchem/ec7.html
http://www.chem1.com/acad/webtext/elchem/ec7.htmlhttp://www.chem1.com/acad/webtext/elchem/ec7.html
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Roleoftribologyinsurfaceengineering
Machinedormechanicallyabradedandpolishedsurfaces
Beilby
layer:Layerofparentmetalthatisheavilydeformedasaresultof
surfaceengineering
Beilby
layermayconsistofsmearedlayerofmetal,metaloxide,polishing
powderetc.
BeneaththeBeilby
layerliesaheavilyshearedregionwithdifferent
mechanicalproperties
from
the
bulk
(modified
grain
structure)
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Inservicebehaviourofsurfaces
Depends
on
many
different
parameters
Surfacepreparationmethods(eg.mechanicalorchemicalsurface
modification)
Surfaceoperationconditions(eg.contactbetweensurfaces,lubrication)
Surfacerelatedphenomena
Wear Fatigue Corrosion
SurfaceEngineering
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Surfaceengineering
Application of both traditional and innovative surface
technologies to
produce a composite material unattainable in either the base or
surface
materialsindividually
SurfaceEngineering
Surfacemodificationof
existingsurface
chemical
mechanical
thermal
Depositionofadditional
materialonsurface
(thinlayer)
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Surface
engineering
on
existing
surfaceColdworkingprocesses
Surfaceengineering
Shot
peening
Hammeringthesurfaceofamaterialwithsmall
spheresof
steel,
ceramic
or
glass
media
at
relatively
highvelocities.
Theseshotparticlescreateaseriesofoverlapping
dimplesonthematerial'ssurfacewhichputtheupper
layersinto
compression,
and
help
to
prevent
fatigue
failureinthematerial.
http://www.progressivesurface.com/shotpeening.php
Preventsfatiguefailure
andimproves
wear
resistance
http://www.progressivesurface.com/shotpeening.phphttp://www.progressivesurface.com/shotpeening.php
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Thermaltreatment(Hardening)
Thermochemicalprocess
DiffusionofCatomsinto
surface
Formationofhardouterlayer
IncreasedCcontent
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Surfaceengineering
Deposition
of
additional
material
(thin
layer)
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Ionimplantation
N,C,
Ti,
Al
ions
with
high
energies
hit
the
surface
and
penetrate
up
to
0.5
m
Energieslieintherangeof50200keV
Dosageratesaround1015
ions/mm2
Canbeappliedtoceramicandmetalsurfaces
Causeminimal
changes
to
surface
topography
http://www.matec.org/animations/matec/M061FL02.swf
Sputtering
http://www.matec.org/animations/matec/M061FL02.swfhttp://www.matec.org/animations/matec/M061FL02.swf
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Summary
Metallicsurfaces
and
MO
layer
formation
Roleoftribologyinsurfaceengineering
Surfaceengineering
Processingofexistingsurfaces
Addingnew
layer
materials
