Friction of Ceramics

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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