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FRICTION BEHAVIOUR OF
CERAMICS
AMIT YADAVARUN SIVARAJGAURAV BISHTMOHIT DAHARAN
SHAIBY TOMAR
Presentedby-
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Ceramics
• The term ceramic comes from theGreek word
keramikos,which means burnt stuff
• Usually compound between metallicand non-metallic elements
•
Always composed of more than oneelement
• Bonds are partially or totally ionic,
and can have combination of ionic
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MANUFACTURING OFCERAMICS
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Properties of ceramics
• Hard and brittle
• High compressive strength
•
Good electric and thermal insulators• High melting temperature
• Good aesthetic appearance
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Classification of Ceramics
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Glasses
• Fine grained polycrystallinematerial
• Main ingredient is Silica (SiO2)
•
If cooled very slowly will formcrystalline structure.
• If cooled more quickly willform amorphous structureconsisting of disordered and
linked chains of Silicon andOxygen atoms.
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Whitewares
• Crockery
• Floor and wall
tiles• Sanitary-ware
• Electrical
porcelain• Decorative
ceramics
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Refractories
• Firebricks forfurnaces andovens.
• Have high Siliconor Aluminiumoxide content.
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Abrasive Ceramics
• Used to cut away, grindmaterial
•
High Hardness• High wear resistance
• High degree of toughness
Example: silicon carbide,tungsten carbide, aluminumoxide, etc.
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Ceramic Crystal structures
Rock Salt Structure Cesium Chloride
Structure
t t t
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eram c rysta structurescontd..
Zinc Blende
Structure
Barium titanateStructure
t t t
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ta ty o ceram cs epen on twofactors:
– Coordination number: maximum numberof ions adjacent to another ion withoutoverlap in electron orbitals
– Electronegativity: how willing atoms areto accept electrons
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Application:
Ø Tooling
Ø Biomedical
Ø ceramic brake discsØ High voltage insulators and spark
plugs
Ø Ceramic parts for gas turbineengines
Ø Wear plates and thermal barriers
Ø
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FRICTIONAL BEHAVIOUR OFCERAMICS
Ø Combine low density with excellent mechanical properties
Ø Ceramic pairs are commonly used in extremeenvironmental conditions
Ø Shows limited plastic flow at room temperature
Ø Mainly adhesive forces present
Ø Low real area of contact leads to low friction
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VARIATION OF COEFFICIENT OFFRICTION WITH VARIOUS PARAMETERS
Ø Coefficient of friction with slidingspeed
Ø Coefficient of friction with fracturetoughness
Ø Coefficient of friction with normal
load
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1 2 3 4
.2
.4
.6
00
Coeffici
entof friction ,µ
Sliding speed ,(Ms-1)
Coefficient of friction withsliding speed
AL2O3
For Al2O3,ZrO2,SiC and Si3N4
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1
.8
0
.2
.4
.6
2 4 6 8
C o e f f i c
i e n t o f
f r i c t i o n
, µ
Fracturetoughness(Mpa m1/2)
Coefficient of friction with Fracturetoughness
Coefficient of friction as a function of fracture toughness for
a sharp diamond pin on disks made of SiC,Si3N4,Al2O3,ZrO2produced under various hot pressing processes
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0
.2
2 4 6 8 10
.4
.6
.8
Co
ef ficientof
friction,
µ
Normalload (N)
0
Coefficient of friction withNormal load
For Al2O3,Sic,Si3N4 and ZrO2
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200
400
600
800
1000
.2
.4
.6
.8
Coeffici
entof friction,µ
Temperature(0C)
Coefficient of friction with temperature
For Al2O3 and ZrO2
U l b i t d F i ti f C i
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Unlubricated Friction of Ceramic-Ceramic Contacts
• strongly influenced by sliding conditions,
• temperature and
• the presence of moisture
The deformation processes taking place in a dryceramic contact can be classified as :-
•
Ductile and• Brittle
D til d f ti
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• In ductile deformation, observed usually under moderate slidingconditions, an asperity contact causes plastic flow and
displacement of material rather than its removal.
Brittle deformation:
• In contrast, brittle deformation is characterized by extensive
fracture along the grain boundaries during an asperity contact. This type of deformation dominates at high contact stressesand/or in systems where one counterface is much harder thanthe other. Entire grains of a ceramic can be detached by brittlefracture and debris is formed by the subsequent fragmentationof these grains. Severe wear usually accompanied by high
friction is observed.
Ductile deformation:
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Physical properties of typical engineeringceramics.
e r o og ca c arac er s cs o ceram cs
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e r o og ca c arac er s cs o ceram csare complex and depend on the followingfactors:
• material composition and properties
•
sliding conditions (speed, load andtemperature)
•
surrounding environment
• the type of counterface
T ib l i l h t i ti f l t d i i
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Tribological characteristics of selected ceramics inunlubricated self-mated contacts
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Dry Friction of Ceramics at Elevated Temperatures
Ø The coefficient of friction of ceramics areusually increased at elevated temperatures
Ø Although in certain temperature rangesreduction has been recorded for siliconbased , alumina ceramics
Ø Alumina ceramics suffer increased value of coefficient of friction at high temperatures
in air which is usually due to abrasion
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Variation of coefficient of friction with Temperature
F i ti f C i i th P f
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Friction of Ceramics in the Presence of Water or Humid Air
Ø Water and/or atmospheric moisture can affect theceramics in both positive and negative ways
Ø
The most beneficial effect of moisture is the formationof a thin soft hydrated layer on the ceramic surfacewhich acts as a lubricant
Ø The lubricating layer can be formed on both aluminaand silicon-based ceramics
Ø
However, if the depth of the hydrated layer becomesexcessivel lar e then a form of corrosion occurs in the
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r c on o eram cs ga ns e a c
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r c on o eram cs ga ns e a cMaterials
Ø Metallic alloys, in particular steel and cast iron ,have been widely studied as sliding counterfacesto ceramics.
Ø The coefficient of friction in dry ceramic-metalcontacts depends on the type of metalliccounterface and the load/speed conditions
Ø Broad ranges of coefficients of friction for variousmetallic counterfaces have been reported: 0.2 -0.8 for steels and cast irons , 0.2 - 0.5 forsofter materials such as brass, bronze,aluminium and copper and 0.3 - 0.4 for cobalt-
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surface and the formation of a metallic transferlayer.
M h i f t l dh i t
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Mechanism of metal adhesion to aceramic surface and the formation of ametallic transfer layer.
Friction behavior of Alumina ceramics in
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Friction behavior of Alumina ceramics inaqueous solutions with different pH
• Friction behavior of ceramics can be significantlyimproved by using them in water or humid air rather
than in a dry atmosphere
• We have investigated the friction behavior of aluminaceramics in different water-lubricated conditions with arange of pH values from 0.85 to 13.
• Based on the results of reciprocating sliding tests, we
found that the the coefficient of friction vary from 0.2 to0.6
INTRODUCTION :
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EXPERIMENT:
•Materials used - alumina plate (300mm length )and cylindrical pins (dia. 16.6m
•
The experiments were performed in a reciprocating sliding device with a 7mmstroke
• The frequency of oscillation was 1 Hz
•Use distilled water and HCl (with different pH value) as lubricant
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RESULT:
•
The low values (about 0.22) of the coefficient of frictionwere obtained in the acidic and alkaline conditions at pH0.85 and 13
•
Higher friction (about 0.55) was measured for all the other
Fig: coefficient of friction as a function of pH.
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CONCLUSION:
• The coefficient of friction varied from about 0.2 toabout 0.6 depending on the pH
•
If the pH was very low (acid: pH 0.85) or very
high (alkaline: pH 13), the coefficient of frictionwas low
• These findings suggest an increased potential forachieving the desired friction behavior if theproper water-lubrication conditions are applied
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THANK YOU