Munda Wear

8182019 Munda Wear

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Authors personal copy

Friction and wear properties of steel backed Alndash10Snndash4Sindash1Cu metallic strips

prepared via spray atomizationndashdeposition-rolling route

Parikshit Munda RK Dube Bikramjit Basu SC Koria

Department of Materials and Metallurgical Engineering Indian Institute of Technology Kanpur 208016 India

a b s t r a c ta r t i c l e i n f o

Article history

Received 16 February 2009

Accepted in revised form 12 May 2009

Available online 21 May 2009

Keywords

Steel backed bearing strip

AlndashSnndashSindashCu bearing strip

Fretting

Friction

Wear

Spray deposition

Rolling

In various load bearing structural applications related to automotive industries steel backed aluminum alloy

strips are considered For such applications it is desired to design appropriate alloy composition for metallic

stripso thatgood tribological properties canbe achievedIn ourongoingeffortsto accomplish thisaim we have

recently fabricated a steel backed Alndash10Snndash4Sindash1Cu bearing strip which is prepared by spray depositing the

molten bearing alloy on a steel substrate followed by warm rolling of theresulting laminatedstripto different

thickness reductions up to 80 The tribological performance of the steel backed Alndash10Snndash4Sindash1Cu strips is

evaluated against the bearing steel Whilethe recorded steady statecoef 1047297cient of friction (COF) does notshow

any noticeable difference (varying in the range of 06ndash07) with respect to difference in warm rolling

conditions the fretting wear rate (10ndash26times10minus5 mm3 Nminus1mminus1) of the steel backed and warm rolled strips

exhibits a systematic decrease in wear rate with increase in amount of warm rolling SEM-EDS analyses reveal

the oxidative wear and the extensive cracking of alumina rich tribolayer as the dominant material removal

mechanisms The tribological properties of the spray deposited and 80 rolled steel backed Alndash10Snndash4Sindash1Cu

bearing strip is compared with those of a commercially available AlndashSn based sleeve bearing under identical

fretting conditions

copy 2009 Elsevier BV All rights reserved

1 Introduction

Bimetallic strips are generally used for making bearings for the

crankshaft of an internal combustion engine Such a bimetallic strip

consists of a bearing layer which is metallurgically bonded to a

supporting steel strip Two approaches are widely adopted for pre-

paring such bimetallic strips The 1047297rst and the original approach is

based on powdermetallurgy It consists of spreadinga powder mass of

the chosen bearing alloy over a steel strip surface which is sub-

sequently heated to a suitable temperature in protective atmosphere

to bring about sintering between powder mass and supporting steelstrip The sintered ldquocompositerdquo strip is subsequently rolled and heat

treated to produce a dense layer of the bearing alloy metallurgically

bonded with the supporting steel strip The second approach consists

of preparing a thin strip of the chosen bearing alloy by casting or

powder metallurgy and subsequently the strip is roll bonded to form

the bimetallic strip

There has been a development in the above mentioned 1047297rst

approach for preparing bimetallic strip wherein liquid or semi-liquid

droplets of bearing alloys are deposited on the specially prepared

surface of the supporting steel strip Subsequently the laminated

composite ie the deposited bearing alloy together with the steel

strip is rolled and heat treated to form the bimetallic strip A most

convenient way of preparing liquid or semi-liquid droplets of the

bearing alloy is by gas atomization of liquid metals In principle the

manufacturing route consists of gas atomization of the chosen liquid

bearing alloy in a closed chamber and allowing the atomized droplets

to deposit on a steel strip substrate kept at a suitable distance below

the geometric point (also known as gas impingement point) of the

atomizer in the atomization chamber On cooling a laminatedcomposite strip is obtained in which the spray deposit of the bearing

layer is adhered with the supporting steel strip

Prior to atomization the surface of the steel strip substrate should be

shot blastedfor betteradherence of thespraydeposit withthe steel strip

surface In a batch type operation the thickness of the spray deposited

bearing layer could be controlled by the amount of the initial metal

taken for melting whereas in a continuous type it is controlled by the

speedof the traversing steelstrip substrateSubsequently the laminated

composite strip is rolled at a suitable temperature to obtain nearly full

density in the deposit good metallurgical bonding between bearing

alloylayer and steelstrip substrate and improved mechanicalproperties

The above manufacturing route for making bimetallic strip can be

designatedas ldquospray atomizationndashdeposition-rollingrdquo routeIt shouldbe

noted that a similar manufacturing route developed by Singer [1] has

Surface amp Coatings Technology 203 (2009) 3541ndash3548

Corresponding author Fax +91 512 2597505

E-mail address bikramiitkacin (B Basu)

0257-8972$ ndash see front matter copy 2009 Elsevier BV All rights reserved

doi101016jsurfcoat200905021

Contents lists available at ScienceDirect

Surface amp Coatings Technology

j o u r n a l h o m e p a g e w w w e l s ev i e r c o m l o c a t e s u r f c o a t

8182019 Munda Wear



been investigated for preparing monolithic metal strip However not

enough research and development work has been carried out for

preparing steel backed bearing alloy strip by this route [2]

Aluminum alloys and copper alloys are two major materials used

for the bearing alloy layer The most common alloying element in

aluminum alloys is tin or lead which imparts the lubricating property

and compatibility However the environmental regulations restrictthe application of lead in bearing alloy layer In an earlier paper the

experimental results of the preparation of the steel backed AnndashSn

strip via spray atomizationndashdeposition-rolling route have been des-

cribed and discussed [3] The tribological behavior of such bimetallic

strip has also been reported therein [4]

Although AlndashSn alloys have good bearing qualities they are not

suitable forthe application in high speed and load engines Coppercan

be added to AlndashSn alloys to increase the strength of the aluminum

matrix It alsoenhancesthe fatigue property Copper is addedgenerally

in the range of 01ndash2 wt The wear resistance and the seizure resis-

tance of the bearing alloy layer can be improved by the addition of

silicon in the range of 3ndash4 wt [5] On the basis of all these con-

siderations a typical aluminum alloy composition for the bearing

application could be Almdash

10 wtSnmdash

4 wtSimdash

1 wt Cu (henceforthabbreviated as Alndash10Snndash4Sindash1Cu)

Friction and wear are of considerable importance in components

used for bearing applications It is important to understand the

tribological behavior of steel backed Alndash10Snndash4Sindash1Cu strip Fretting

as an important wear phenomenon refers to any situation in which

the contacts between materials are subjected to a low amplitude

oscillatory sliding motion [67] Fretting often takes place in hubs and

disks press 1047297tted to rotating shafts in riveted and bolted joints

between the strands of wire ropes and between the rolling elements

and their tracks in stationary ball and roller faces [6] The displace-

ment amplitude (5ndash300 microm) encountered in fretting are smaller than

those of reciprocating sliding [7] This means that contact is

maintained over most of the tribosurfaces during fretting As a result

much of the wear debris produced by fretting remains trapped at the

interface which can cause seizure in components such as 1047298exible

couplings [8] Another important aspect of fretting is the development

of fatigue cracks in the damaged region which reduces the fatigue

strength of the cyclically loaded components

In the present paper fretting wear behavior of the rolled and heat

treatedsteel backed Alndash10Snndash4Sindash1Cu viaspray atomizationndashdeposition-

rolling route against bearing steel has been investigated and discussed

An attemptis madeto identifythe dominantmechanisms responsiblefor

the wear during fretting The tribological behavior of the present bi-

metallic strip is also compared with that of the rolled and heat treated

steel backed Alndash10Sn alloy strips prepared via the same route [4] More

importantly a performance comparison is being made with commercial

AlndashSn bearing alloy used as sleeve bearings in a premier Indian

automotive company when tested under identical fretting conditions

2 Experimental

21 Materials

A schematic view of the experimental set-up used for depositing

bearing alloy layer on the steel strip substrate is shown in Fig 1(a) It

consists of a melting furnace a combined spray atomization and

deposition chamber A resistance heating furnace using SiC heating

elements was designed to melt the alloy

The required amounts of Alndash44Sindash12Cu master alloy and Sn

corresponding to Alndash10Snndash4Sindash1Cu were taken and were melted in a

cylindrical stainless steel crucible Tin pieces were added after the

master alloy has been melted Molten alloy was delivered in the spray

atomization chamber through a 137 mm long graphite tube of 4 mmdiameter A specially designed stopper was inserted in the hole of the

metal delivery tube to prevent the1047298ow of liquid metal duringmelting

For each spray atomization run the mass of melt was 250 gm The

molten Alndash10Snndash4Sindash1Cu alloy was atomized using air jets at a

plenum pressure of 18 kg cmminus2 in a free fall atomizer The steel strip

substrate of size 380 mmtimes80 mmtimes1 mm was kept at a distance of

450 mm below the bottom of the melting furnace Prior to deposition

the surface of the steel strip substrate was shot blasted with SiC

particles The centre of the substrate coincided with the central axis of the melt delivery tube The substrate was held 1047297rmly by placing heavy

weight at both the ends A sample of size 20 mmtimes75 mm was taken

from both ends of the spray deposited steel backed Alndash10Snndash4Sindash1Cu

strip for rolling This had a thickness of the deposit as 1plusmn 02 mm The

steel backed spray deposited Alndash10Snndash4Sindash1Cu strip samples were

rolled at 200 degC on a single strand non-reversing type two-high

rolling mill having 135 mm diameter rolls Such a rolling process has

been referred to warm rolling (WR) in the present paper Before

rolling samples were heated at 200 degC for 45 min in nitrogen

atmosphere The reheating furnace and warm rolling furnace were

interconnected in such a manner that the strips were in the nitrogen

atmosphere right up to the nip of the rolls The laminated composite

Alndash10Snndash4Sindash1Cu strips were rolled to 20 40 60 and 80 reduction

in total thickness and annealed at 200 degC for 45 min Prior to the weartest the microstructure of the steel backed spray deposited Alndash10Snndash

4Sindash1Cu bearing strip was investigated by X-ray diffraction (SEIFERT

ISO DEBYEFLIEX 2002 X-ray diffraction machine) using Cu Kα radi-

ation (λ=0154059 nm) and optical microscope (ZEISS Axioskop 2

MAT)

22 Wear test and characterization

The fretting experiments were performed using a computer con-

trolled fretting machine (DUCOM TR281-M Bangalore India) which

produces a linear relative oscillating motion with ball-on-1047298at con1047297g-

uration By a stepper motor the1047298at samplewas made to oscillate with

a relative linear displacement of constant stroke and frequency The

displacement of the 1047298at sample was monitored by an inductive dis-

placement transducer A piezoelectric transducer was used to measure

the friction force The variation in tangential force was recorded and

the corresponding coef 1047297cient of frictionwas calculated onlinewith the

help of a computer based data acquisition system

Warm rolled Alndash10Snndash4Sindash1Cu strip samples having dimensions

10times10 mm were used as 1047298ats samples for wear testing Bearing grade

steel balls were used as counterbodieswhich werekept stationarywhile

the1047298at samples were subjectedto reciprocatingmotion Forcomparison

fretting tests were also conducted on commercial steel backed AlndashSn

sleeve bearing alloy under identical conditions The commercial sample

was procured from a leading Indian automotive industry and this alloy

contains around 14SnThis bearing material is used widely in an Indian

car and the material has been designed as ldquoInd-Crdquo

Before the fretting tests both 1047298at and ball were ultrasonicallycleaned in acetone The fretting experiments were performed at 4 Hz

oscillating frequency with 100 microm linear strokes for 20000 cycles

duration under 1N load Also the combination of testing parameters

results in the gross slip fretting contacts All experiments were

conducted in air at room temperature (30plusmn2 degC) with relative

humidity (RH) of 45plusmn5 The schematic of the fretting wear test set-

up is shown in Fig 1(b)

After each test the worn surfaces of both the 1047298at and the ball were

observed using an optical microscope Further detailed characterization

of theworn surfaces wasobservedusinga scanning electron microscope

(FEI QUANTA 2000 HV SEM) equipped with energy dispersion spectro-

scopy (EDS) Thewear volume of both 1047298at and ball were calculated from

the measured wear scar diameters using the equation given by Klaffke

[9] The use of this equation is reported to be justi1047297ed for the presentfretting conditions (providing error of 5)when the wear scar diameter

is larger than twice theHerziancontact diameter as was the case in the

3542 P Munda et al Surface amp Coatings Technology 203 (2009) 3541ndash 3548

8182019 Munda Wear



present experiments From the estimated wear volume the speci1047297c

wear rates [(wear volume)(loadtimesdistance)] are calculated

3 Results and discussion

31 Porosity and phases present in the spray deposited and warm rolled

steel backed Alndash10Snndash4Sindash1Cu strip

The porosity in the bearing layer of the steel backed Alndash10Snndash4Sindash

1Cu strip after different amount of thickness reduction by warm

rolling is given in Table 1 It can be seen that the porosity in the bearing

layer is decreased with increased percentage of warm rolling The

porosity after 80 warm rolling is ~05 A representative optical

microscopy image of 80 rolled is provided in Fig 2(a)

In order to illustrate thephase assemblageof the thin bearing strip a

representative XRDplot of the80 rolledsampleis provided in Fig 2(b)

While thestrongpeaksof Al matrixand Sn precipitatesare recordedthe

minor peaks from thesecondphases eg Siand Al2O3 are also observedThe formation of any reaction phases is not observed within the

detectable limit of the XRD unit under the present condition

Fig 1 Schematic diagram of spray atomization and deposition set-up (a) and fretting wear test set-up (b)

3543P Munda et al Surface amp Coatings Technology 203 (2009) 3541ndash 3548

8182019 Munda Wear



32 Friction and wear properties

In order to assess the in1047298uence of the processing conditions on

the frictional properties the fretting wear tests were carried out on

Alndash10Snndash4Sindash1Cu strip warm rolled with variation in the thickness

reduction of 20ndash80 The continuously recorded coef 1047297cient of friction

is plotted in Fig 3 Duringthe initial 1000 cycles theCOF rises to a very

high value of 07ndash09 and thereafter it attains a steady state value The

steady state COF varies in the narrow window of 06ndash07 independent

of warm rolling thickness reduction Therefore it can be said that thewarm rolling conditions as used in the present work do not have any

signi1047297cant in1047298uence on frictional properties of steel backed Alndash10Snndash

4Sindash1Cu strip against bearing steel ball It can be pointed out here that

all the investigated strips after different amount of warm rolling

contain porosity in the range of 05ndash105

In an earlier work the steady state COF of steel backed Alndash10Sn

bearing strip after similar level of warm rolling exhibited steady state

COF between 075 and 12 against steel counterbody under identicalfretting conditionThose bearing strips however had different level of

porosity and were in the range of 9ndash31 [4]

The speci1047297c wear rate of the spray deposited and warm rolled steel

backed Alndash10Snndash4Sindash1Cu strips were calculated from measured wear

scar diameter of the worn surfaces of the respective samples after

fretting under investigated conditions The wear rate decreases in a

systematic linear manner with percent warm rolling which can be

seen in Fig 4(a) At the highest warm rolling conditions (80) the

wear loss of Alndash10Snndash4Sindash1Cu is the lowest In an effort to analyze the

in1047298uence of the porosity on wear resistance Fig 4(b) plots the wear

rate versus percent porosity It is clear that wear rate increases with

porosity and the strip with 05 porosity exhibited highest wear

resistance

33 Worn surface topography of the spray deposited warm rolled steel

backed Alndash10Snndash4Sindash1Cu strip

Detailed microstructural investigation using SEM-EDS was carried

out on the worn surfaces of warm rolled steel backed Alndash10Snndash4Sindash

1Cu spray deposit to understand the mechanism governing the

fretting wear Fig 5(a) displays the overall topographical features of

the worn scar formed on the surface of the 20 warm rolled Alndash10Snndash

4Sindash1Cu spray deposit strip after 20000 cycles under 1N load for

100 microm linear amplitude and 4 Hz frequency against bearing grade

steel ball It is clear from Fig 5(a) that the entire surface is covered

with the tribochemical layer with different topographical contrast

The details of such layer can be seenwithmore clarity in Fig 5(b) The

extensive cracking canbe seen both along thefrettingdirection as well

as perpendicular to the fretting direction Also the cracking has been

found to be more severe near the central region of the worn surface

No evidence of abrasion or plastic 1047298owcan be seen EDS compositional

analysis of multiple areas of the worn surface reveals that the

tribochemical layer is essentially alumina rich Also the intensityof the

Fe-peak appears to be very weak essentially indicating insigni1047297cant

Table 1

Percent porosity and speci1047297c wear rate of spray deposited Alndash10Snndash4Sindash1Cu strip as a

function of percent warm rolling (WR)

S no Sample Porosity COF Speci1047297c wear rate

(times10minus5 mm3 Nminus1 mminus1)

1 Alndash10Snndash4Sindash1Cu20WR 105 066 26




5 Ind-C (Alndash14Sn)as received ndash 075 18

Fig 2 Optical micrograph of steel backed and 80 warm rolled Alndash10Snndash4Sindash1Cu strip

(a) and XRD plot of steel backed and 80 warm rolled Alndash10Snndash4Sindash1Cu strip

Fig 3 Coef 1047297cient of friction of spray deposited(SD) steel backed80 thicknessreduction

and commercial sleeve bearing Ind-C as a function of number of cycles


8182019 Munda Wear



transfer of materials from mating counterbody (steel ball) One

representative EDS spectrum is provided in the inset of Fig 5(b)

When the same metallic strip after 40 warm rolling is fretted

under identical conditions we observed much extensive cracking of

the tribochemical layer throughout the worn surface Also a largeamount of wear debris particles (both 1047297ner in size as well as

agglomerated) are found around the periphery of the worn surface

The details of the wear debris particles in terms of size and shape can

be seenin the inset of Fig 6(a) Largely thewear debrisparticles areof

submicron size with few agglomerated irregular shaped debris

particles appearing in sizes of less than 10 microm Again EDS composi-

tional analysiscon1047297rms[inset of Fig6(b)] thepresence of alumina rich

tribochemical layer The fragmentation of the tribochemical layers can

be clearly seen in Fig 6(b) It is easy to realize that during continuous

fretting process a number of fragmented parts of tribochemical layer

with sizes in the range of 50ndash100 micromcan beeasilyspalled and thiswill

lead to the subsequent wear of the underlying material

In case of the same Alndash10Snndash4Sindash1Cu based metallic strip after 60

warm rolling similar topographical features are clearly observed [seeFig 7(a)] Thedetailed topographical observations as shown in Fig 7(b)

reveal the extensive occurrence of cracking A comparison of Fig 7(b)

with Fig 6(b) however con1047297rms that the severity of fretting induced

damage is noticeably reduced as the percent warm rolling increased

from 40 to 60

Fig 8(a) and (b) show typical SEM images showing overall

topography of worm surfaces of the metallic strip with the highest

percent warm rolling (80) The worn surface exhibits even much less

cracking induced damage mechanism [see brighter contrast area inFig 8(a)] The major part of the worn surface is however covered with

tribolayer Also signi1047297cant amount of 1047297ner and agglomerated debris

particles are observed in the regions adjacent to the edges of wear

scar Like in other cases the amount of Fe transfer to worn surface is

minimum

From the above observations it should be clear that oxidative

wear and cracking of the tribochemical layer are the major wear

Fig 4 Speci1047297c wear rate of Alndash10Snndash4Sindash1Cu as function of percent warm rolling (a)

and percent porosity (b)

Fig 5 Typical SEM images at different magni1047297

cations showing overall topography of worn surfaces of spray deposited and 20 warm rolled Alndash10Snndash4Sindash1Cu strip fretting

conditions-20000 cycles 4 Hz frequency100 microm stroke length counter body bearing

steel arrows indicate fretting direction


8182019 Munda Wear



mechanisms Duringthe initial stageAl is oxidizedto form Al2O3 layer

During repeated fretting stroke Al2O3 rich tribolayer cracks and a

number of cracked islands of wear fragments are formed The obser-

vation of large amount of wear debris particles around the wear scar

periphery indicates that such debris particles are formed due to re-

peated fracturing of suchwear fragmentsand subsequently ejected out

from the tribological interface

34 Comparison of the tribological behavior of the present material with

that of other materials

The tribological behavior of the spray deposited and warm rolled

steel backed Alndash10Snndash4Sindash1Cu strip was compared with that of sleeve

bearing material (designated as Ind-C) used widely in an Indian car

The EDS analysis of the bearing layer showed that it was basically

aluminum-based having approximately 14ndash15 wt tin as the major

alloying element Fig 3 also plots the continuously recorded

coef 1047297cient of friction of the Ind-C material During the initial

1000 cycles the COF rises to a high value of 08 and thereafter it

attains a steady state value The steady state COF varies in the narrow

range of 07ndash08 having an average value of 075 The speci1047297c wear

rate of the Ind-C material was found to be 18times10minus5 mm3 Nminus1mminus1 It

can be seen that the COF value and the speci1047297c wear rate of the Ind-C

material is greater than that of the spray deposited and 80 warm

rolled steel backed Alndash10Snndash4Sindash1Cu strip (containing 05 porosity)

used in the present study Thecorrespondingvalueof average COFand

speci1047297c wear ratewere 063 and 10times 10minus5 mm3 Nminus1mminus1 respectively

(Table 1)Fig9(a) shows representative SEM image of the overall topography

of the worn surface formed on the Ind-C material after 20000 cycles





Fig 7 Typical SEM images at different magni1047297cations showing overall topography of

worn surfaces of spray deposited and 60 warm rolled Alndash10Snndash4Sindash1Cu strip fretting




8182019 Munda Wear



under 1N load for 100 microm linearamplitude and 4 Hz frequency against

bearing grade steel ball It is clear that thecommercial bearing material

experiences extensive tribochemical wear More signi1047297cantly large

amount of coarsesheet like wear debrisparticles arefound to disperse

around wear scar edge Also 1047297ner wear debris particles are also

observed The details of the tribological layer formed on the surface can

be seen more clearly in Fig 9(b) Extensive cracking of the

tribochemical layer along with severe fragmentation of tribochemical

layer are evident EDS analysis con1047297rms that tribochemical layer is

essentially oxide rich The amount of steel transfer to 1047298at is negligible

The implication of the present work is important In our earlier

work we reported the tribological properties of Alndash10Sn metallic strip

under identical fretting conditions One of the important results was

that Alndash10Sn alloy when warm rolled 75thickness reductionexhibits high COF of 09This material was prepared using the same

approach as used for steel backed Alndash10Snndash4Sindash1Cu bearing strip [4]

The present work demonstrates that suitable alloy design ap-

proach can enable us to develop better metallic strip of Alndash10Snndash4Sindash

1Cu composition having a lower of COF of 063 From the aspect of real

applications any tribological material experiencing lower friction is

always preferred This is due to the fact that the dissipated energy will

be lower in case of material combinations with lower COF and as a

result lower energy needs to be supplied from external source tomaintain relative motion at the tribological interface On the basis of

the present study it should be clear that the WR-80 sample should be

preferred over commercial sleeve bearing alloy (Ind-C sample) for

given automotive applications This will ensure longer durability cou-

pled with energy savings as well as from economic aspect (less fre-

quent replacement)

Theadvantage forthe useof Alndash10Snndash4Sindash1Cualloyoverthe Alndash10Sn

alloy produced via the same processing route can also be mentioned



conditionsmdash20000 cycles 4 Hz frequency100 microm stroke length counter body bearing



cations showing overall topography of worn surfaces of AlndashSn commercial sleeve bearing (Ind-C) fretting conditionsmdash

20000 cycles 4 Hz frequency 100 microm stroke length counter body bearing steel

arrows indicate fretting direction


8182019 Munda Wear



fromthe processingaspect Fromthe manufacturing aspect the addition

of Si enhances the 1047298uidity of the melt and thereby ensures a moredense

spray deposit of the bearing layer on the steel substrate As a result steel

backed Alndash10Snndash4Sindash1Cu bearing alloy strip will require less amount of

warm rolling for achieving near full density in the bearing layer as

compared to steel backed Alndash10Sn bearing alloy strip produced under

identical condition of spray deposition and rolling

4 Conclusions

In the present work the steel backed and warm rolled Alndash10Snndash

4Sindash1Cu metallic strips were fretted against bearing steel Based on

our experimental observations the following conclusions are drawn

a No signi1047297cant difference in terms of the frictional behavior was

observed when the metallic strips warm rolled to varying thick-

ness reductions of up to 80 were subjected to fretting wear

against steel Independent of warm rolling conditions the steady

state COF varies in the narrow window of 06ndash07

b The speci1047297c wear rate decreases in a systematic linear manner

with percentage warm rolling of spray atomized layer The wear

rate of 80 warm rolled steel backed Alndash10Snndash4Sindash1Cu strip wasfound to be 10times10minus5 mm3Nminus1mminus1

c The tribooxidation is the dominant wear mechanism and the

formation of alumina rich tribolayer is observed irrespective of

warm rolling conditions The cracking of tribolayer and signi1047297cant

wear debris (both submicron and agglomerated) formation are

found to be additional mechanisms

d The COF of the spray deposited and 80 warm rolled steel backed

Alndash10Snndash4Sindash1Cu stripshas beenfound to belowerthan thatof the

spray deposited Alndash10Sn composition subjected to similar amount

of warm rolling

e The COF value and the speci1047297c wear rate of the present materialwarmrolled to80 has beenfoundto belowerthan thatof a typical

steel backed AlndashSn bearing alloy strip used in a commercially pro-

duced Indian passenger car

References

[1] ARE Singer Met Mater 4 (1970) 246[2] MR Tripathy Properties of steel backed AlndashSn strip prepared via spray atomizationndash

deposition-rolling route MTech dissertation Indian Institute of Technology KanpurIndia 2005

[3] MR Tripathy RK Dube SC Koria J Mater Process Technol 190 (2007) 342[4] MR Tripathy BV Manoj Kumar B Basu RK Dube SC Koria Mater Sci Technol

23 (2007) 15[5] T Desaki S Kamiya K Sato Y Okauchi and T Nukami Aluminum alloy for sliding

bearing and its production method US Patent no6 706126 B2 Mar 16 2004[6] IM Hutchings Tribology Friction and Wearof Engineering Materials Edward Arnold

London 1992[7] O Vingsbo S Stierberg Wear 126 (1988) 131[8] AD Sarkar Friction and Wear Academic Press London 1980[9] D Klaffke Tribol Int 22 (2) (1989) 89


8182019 Munda Wear



Friction and wear properties of steel backed Alndash10Snndash4Sindash1Cu metallic strips

prepared via spray atomizationndashdeposition-rolling route

Parikshit Munda RK Dube Bikramjit Basu SC Koria

Department of Materials and Metallurgical Engineering Indian Institute of Technology Kanpur 208016 India

a b s t r a c ta r t i c l e i n f o

Article history

Received 16 February 2009

Accepted in revised form 12 May 2009

Available online 21 May 2009

Keywords

Steel backed bearing strip

AlndashSnndashSindashCu bearing strip

Fretting

Friction

Wear

Spray deposition

Rolling

In various load bearing structural applications related to automotive industries steel backed aluminum alloy

strips are considered For such applications it is desired to design appropriate alloy composition for metallic

stripso thatgood tribological properties canbe achievedIn ourongoingeffortsto accomplish thisaim we have

recently fabricated a steel backed Alndash10Snndash4Sindash1Cu bearing strip which is prepared by spray depositing the

molten bearing alloy on a steel substrate followed by warm rolling of theresulting laminatedstripto different

thickness reductions up to 80 The tribological performance of the steel backed Alndash10Snndash4Sindash1Cu strips is

evaluated against the bearing steel Whilethe recorded steady statecoef 1047297cient of friction (COF) does notshow

any noticeable difference (varying in the range of 06ndash07) with respect to difference in warm rolling

conditions the fretting wear rate (10ndash26times10minus5 mm3 Nminus1mminus1) of the steel backed and warm rolled strips

exhibits a systematic decrease in wear rate with increase in amount of warm rolling SEM-EDS analyses reveal

the oxidative wear and the extensive cracking of alumina rich tribolayer as the dominant material removal

mechanisms The tribological properties of the spray deposited and 80 rolled steel backed Alndash10Snndash4Sindash1Cu

bearing strip is compared with those of a commercially available AlndashSn based sleeve bearing under identical

fretting conditions

copy 2009 Elsevier BV All rights reserved

1 Introduction

Bimetallic strips are generally used for making bearings for the

crankshaft of an internal combustion engine Such a bimetallic strip

consists of a bearing layer which is metallurgically bonded to a

supporting steel strip Two approaches are widely adopted for pre-

paring such bimetallic strips The 1047297rst and the original approach is

based on powdermetallurgy It consists of spreadinga powder mass of

the chosen bearing alloy over a steel strip surface which is sub-

sequently heated to a suitable temperature in protective atmosphere

to bring about sintering between powder mass and supporting steelstrip The sintered ldquocompositerdquo strip is subsequently rolled and heat

treated to produce a dense layer of the bearing alloy metallurgically

bonded with the supporting steel strip The second approach consists

of preparing a thin strip of the chosen bearing alloy by casting or

powder metallurgy and subsequently the strip is roll bonded to form

the bimetallic strip

There has been a development in the above mentioned 1047297rst

approach for preparing bimetallic strip wherein liquid or semi-liquid

droplets of bearing alloys are deposited on the specially prepared

surface of the supporting steel strip Subsequently the laminated

composite ie the deposited bearing alloy together with the steel

strip is rolled and heat treated to form the bimetallic strip A most

convenient way of preparing liquid or semi-liquid droplets of the

bearing alloy is by gas atomization of liquid metals In principle the

manufacturing route consists of gas atomization of the chosen liquid

bearing alloy in a closed chamber and allowing the atomized droplets

to deposit on a steel strip substrate kept at a suitable distance below

the geometric point (also known as gas impingement point) of the

atomizer in the atomization chamber On cooling a laminatedcomposite strip is obtained in which the spray deposit of the bearing

layer is adhered with the supporting steel strip

Prior to atomization the surface of the steel strip substrate should be

shot blastedfor betteradherence of thespraydeposit withthe steel strip

surface In a batch type operation the thickness of the spray deposited

bearing layer could be controlled by the amount of the initial metal

taken for melting whereas in a continuous type it is controlled by the

speedof the traversing steelstrip substrateSubsequently the laminated

composite strip is rolled at a suitable temperature to obtain nearly full

density in the deposit good metallurgical bonding between bearing

alloylayer and steelstrip substrate and improved mechanicalproperties

The above manufacturing route for making bimetallic strip can be

designatedas ldquospray atomizationndashdeposition-rollingrdquo routeIt shouldbe

noted that a similar manufacturing route developed by Singer [1] has

Surface amp Coatings Technology 203 (2009) 3541ndash3548

Corresponding author Fax +91 512 2597505

E-mail address bikramiitkacin (B Basu)

0257-8972$ ndash see front matter copy 2009 Elsevier BV All rights reserved

doi101016jsurfcoat200905021

Contents lists available at ScienceDirect

Surface amp Coatings Technology

j o u r n a l h o m e p a g e w w w e l s ev i e r c o m l o c a t e s u r f c o a t

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10 wtSnmdash

4 wtSimdash





























2 Experimental

21 Materials



































MAT)





































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resistance




















Table 1















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from 40 to 60








minimum










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8182019 Munda Wear





























quent replacement)












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4 Conclusions




















of warm rolling




References








8182019 Munda Wear























10 wtSnmdash

4 wtSimdash





























2 Experimental

21 Materials



































MAT)





































8182019 Munda Wear





















8182019 Munda Wear






























resistance




















Table 1















8182019 Munda Wear
























from 40 to 60








minimum










8182019 Munda Wear







































8182019 Munda Wear





























quent replacement)












8182019 Munda Wear










4 Conclusions




















of warm rolling




References








8182019 Munda Wear





















8182019 Munda Wear






























resistance




















Table 1















8182019 Munda Wear
























from 40 to 60








minimum










8182019 Munda Wear







































8182019 Munda Wear





























quent replacement)












8182019 Munda Wear










4 Conclusions




















of warm rolling




References








8182019 Munda Wear






























resistance




















Table 1















8182019 Munda Wear
























from 40 to 60








minimum










8182019 Munda Wear







































8182019 Munda Wear





























quent replacement)












8182019 Munda Wear










4 Conclusions




















of warm rolling




References








8182019 Munda Wear
























from 40 to 60








minimum










8182019 Munda Wear







































8182019 Munda Wear





























quent replacement)












8182019 Munda Wear










4 Conclusions




















of warm rolling




References








8182019 Munda Wear







































8182019 Munda Wear





























quent replacement)












8182019 Munda Wear










4 Conclusions




















of warm rolling




References








8182019 Munda Wear





























quent replacement)












8182019 Munda Wear










4 Conclusions




















of warm rolling




References








8182019 Munda Wear










4 Conclusions




















of warm rolling




References








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Munda Wear