Friction of Ceramics

8/4/2019 Friction of Ceramics

http://slidepdf.com/reader/full/friction-of-ceramics 1/37

Click to edit Master subtitle style

4/18/12

FRICTION BEHAVIOUR OF

CERAMICS

AMIT YADAVARUN SIVARAJGAURAV BISHTMOHIT DAHARAN

SHAIBY TOMAR

Presentedby-



4/18/12

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



4/18/12

MANUFACTURING OFCERAMICS



4/18/12 44

Properties of ceramics

• Hard and brittle

• High compressive strength

•

Good electric and thermal insulators• High melting temperature

• Good aesthetic appearance



4/18/12

Classification of Ceramics



4/18/12

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.



4/18/12

Whitewares

• Crockery

• Floor and wall

tiles• Sanitary-ware

• Electrical

porcelain• Decorative

ceramics



4/18/12

Refractories

• Firebricks forfurnaces andovens.

• Have high Siliconor Aluminiumoxide content.



4/18/12

Abrasive Ceramics

• Used to cut away, grindmaterial

•

High Hardness• High wear resistance

• High degree of toughness

Example: silicon carbide,tungsten carbide, aluminumoxide, etc.



4/18/12

Ceramic Crystal structures

Rock Salt Structure Cesium Chloride

Structure

t t t



4/18/12

eram c rysta structurescontd..

Zinc Blende

Structure

Barium titanateStructure

t t t



4/18/12 1212

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



4/18/12

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



4/18/12

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



4/18/12

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



4/18/12

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



4/18/12

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



4/18/12

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



4/18/12

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



4/18/12

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



4/18/12

• 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:



4/18/12



4/18/12

Physical properties of typical engineeringceramics.

e r o og ca c arac er s cs o ceram cs



4/18/12

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



4/18/12

Tribological characteristics of selected ceramics inunlubricated self-mated contacts



4/18/12

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



4/18/12

Variation of coefficient of friction with Temperature

F i ti f C i i th P f



4/18/12

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



4/18/12

r c on o eram cs ga ns e a c



4/18/12

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-



4/18/12

surface and the formation of a metallic transferlayer.

M h i f t l dh i t



4/18/12

Mechanism of metal adhesion to aceramic surface and the formation of ametallic transfer layer.

Friction behavior of Alumina ceramics in



4/18/12

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 :



4/18/12

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



4/18/12

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.



4/18/12

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



4/18/12

THANK YOU

Documents

Friction of Ceramics