13.tribological full

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International Journal of Mechanical and Production

Engineering Research and Development (IJMPERD)

ISSN 2249-6890Vol. 3, Issue 1, Mar 2013, 111-124

TJPRC Pvt. Ltd.

THE TRIBOLOGICAL BEHAVIOR OF HYPO-AND HYPER-EUTECTIC Al-Si ALLOYS

UNDER DRY SLIDING CONDITIONS

RIYADH A. AL-SAMARAI1, HAFTIRMAN1, KHAIREL RAFEZI AHMAD2, Y. AL-DOURI3

1School of Mechatronic Engineering, University Malaysia Perlis, Ulu Pau, Perlis, Malaysia

2School of Materials Engineering, University Malaysia Perlis, 02600 Arau, Perlis, Malaysia

3Institute of Nano Electronic Engineering, University Malaysia Perlis, 01000 Kangar, Perlis, Malaysia

ABSTRACT

The effect of surface roughness average of hypo-and hyper-Eutectic Al-Si alloys (with10 and 16-wt% Si) on the

friction and wear was investigated. Various surface roughness averages (Ra) of different degrees were verified as well as three

different loads 10, 20 and 30 N, speeds 200, 300 and 400 rpm and relative humidity 75%. Different surface preparation

techniques result in different Ra values from (0.2and 4) 0.05 m. The contacts were dried sliding. Surfaces were analyzed

through scanning electron microscopy and X-ray dispersive analyses. A pin on-disc apparatus was used for testing in dry sliding

wear. Signal to noise ratio and analysis of variance (ANOVA) were used to study the influence of wear parameters and the

relation between them established multiple linear regressions. It was noted that the weighted and volumetric wear rate

decreases the degree of roughness and the friction coefficient is a function of the stability state. Wear rate is decreased and the

transition from high to low wear increases with an increase in the average surface roughness. It was found that, after the sliding

velocity, there was an increase in wear of Al-Si with increasing load, using a scanning electron microscope to study the wear

mechanisms. At high speeds, the wear behavior of the contact surface of the dry sliding of aluminum, silicon, reduces the risk

of direct contact with metal, there was correlation between friction coefficient and hardness.

KEYWORDS: Hypoeutectic, Hypereutectic, Friction Coefficient, Casting Alloy, Surface Roughness, Hardness

INTRODUCTION

Global efforts to reduce harmful exhaust emissions, reduce costs and improve vehicle fuel to a common aluminum

alloys casting light to , lighter materials, such as the pistons, bearings wear as a simple but effective method to cast iron ,

and also cause instability for cylinder liners. As a result, significant improvements were obtained in wear resistance of

aluminum, silicon, high-current monolithic silicon high density to reduce the stiffness and the wear of the cylinder of the

engine with the Al-Si. This is a costly process engine range in the only car. Therefore, aluminum - silicon research and

development on the current system, and projection, as well as the method of surface preparation, are inexpensive. The

development of internal combustion engines today requires reducing fuel consumption by reducing friction between parts

of the engine to reduce the rate of wear. Piston is considered to be one part of the internal combustion engine which

transmits the energy resulting from the combustion of fuel mix to maintain this energy with minimum loss of looking

designers to improve the smoothness of the surfaces between piston and cylinder[1,2] , wear and friction caused by

complicated interactions between surfaces that are in mechanical contact and slide against each other., the topographical

and geometrical characteristics of the surfaces, and the overall each other, e.g., loading, temperature, type of contact,

atmosphere etc. All mechanical, chemical ,physical, and geometrical aspects of the surface contact.[3]

Menezes et al.[4] have studied the effects of roughness parameters on the friction of aluminum alloy under

conditions of lubrication. They concluded that the coefficient of friction and wear depend on the roughness. Kubiak


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112 Riyadh A. Al-Samarai, Haftirman, Khairel Rafezi Ahmad, Y. Al-Douri

et al.[5] reported the investigations on the surface finishing and termination of many applications in mechanical wheels and

found the necessity to control the termination surface well to reduce the effect of surface roughness and friction within

operations of sliding. It is important to know the quality of the surfaces roughness that requires a process of coating and

treatment to protect it against damage, Kadirgama, et al.[6]. studied the effect of roughness between two surfaces using an

algorithm to calculate the coefficient of friction between them, and determined that there is a flexible deformation and

shearing resistance that depends on external loads, mechanical properties and topography surfaces to give approximate

limits of influence. To increase the process of wear and damaged surfaces, we must take into consideration the mechanical

properties which affect the process. Takata R.[7] and Wieleba W. [8] had been studied roughness and stiffness of

composite materials against steel, which showed its effect on the friction and wear. two surfaces are loaded one on the

other to be in contact at the tops of protrusions and only possibly, the area of contact be really small, so the pressure on the

contact protrusions goes high which may cause the flow of born and as such lead to increasing the area of contact so that

the area of contact becomes real enough for the award of pregnancy, and these conditions[9][10].

All machined metal surfaces appear rough. The individual roughness's are called asperities, and are of varying

heights and depths. Thus, when two bearing surfaces are brought into intimate contact, they actually touch at anextremely small number of points,.[11]The weight loss increases with increasing sliding distance for all condition. The

wear rate increases continuously in normal specimens.[12]Influenced by the rate of temperature rise and speed of sliding

,the ambient temperature and the transition between moderate and severe wear is influenced by thickness of oxide layer.

Menezes et al. [13] have studied the effects of roughness parameters on the friction of aluminum alloy under conditions of

lubrication. They concluded that the coefficient of friction and wear depend on the roughness. Ku et al.[14] have observed

the surface finishing and termination of many applications in mechanical wheels and found the necessity to control the

termination surface well to reduce the effect of surface roughness and friction within operations of sliding. It is important

to know the quality of the surfaces roughness that requires a process of coating and treatment to protect it against damage

[15][16]. Xing et al. [17] have prepared the hypereutectic Al-17.5Si (wt pct) and Al-25Si (wt pct) alloys with various

contents of rare earth Er by conventional casting technique. They investigated the effect of Er on the microstructure and

properties of hypereutectic Al-Si alloys using optical microscopy, scanning electron microscopy (SEM) as well as friction

and wear tests and noticed an improvement of the anti-wear properties and the friction coefficient of the hypereutectic Al-

Si alloys. Gupt and Ling[18] have synthesized three aluminumsilicon alloys containing 7,10 and 19 wt % silicon using a

novel technique commonly known as disintegrated melt deposition technique.

Their results revealed that a yield of at least 80% can be achieved after defacing the shrinkage cavity from the as-

processed ingots and demonstrated an increase in matrix micro-hardness, while 0.2% yield stress decreases in ductility

with an increase in silicon content.

They investigated the effect of extrusion on Al19Si alloy and showed a correlation between micro-structuralcharacterization and mechanical properties of aluminumsilicon alloys and the amount of silicon and secondary

processing technique. Paulus et al., [19] had studied and Monitoring Tablet Surface Roughness During the Film Coating

Process clearly showed that the surface roughness of the tablets increased until the film coating covered the whole surface

area of the tablets. Mitjan and Said [20] had studied and showed that influence of roughness on wear transition in glass-

infiltrated alumina which can be considered an abrupt change in the coefficient of friction only for the tests with the high

roughness disks. Finally, Kubiak et al.[21] studied the Surface morphology in engineering applications: Influence of

roughness on sliding and wear in dry fretting and showed wear activation energy increases for smoother surfaces, while

Lower coefficient of friction and increase in wear rate was observed for rough surfaces.


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The Tribological Behavior of Hypo-and Hyper-Eutectic Al-Si Alloys under Dry Sliding Conditions 113

In this work, to best of our knowledge, investigation of roughness on the wear rate with sliding distance and

velocity of Al-Si casting alloy, on the volumetric wear rate and friction coefficient with normal load is not available in the

literature. It was attempted to bridge the gap between the damages resulting from the sliding surfaces and surface

roughness effect on the friction and wear to provide an approach for evaluating the surface finishing operations. All of

these are divided into the followings: Section 2 displays the experimental process, while results and discussion are given in

section 3, followed by conclusions.

EXPERIMENTAL PROCEDURE

The wear studies were performed for the measurements as shown in Fig.1. The load of the pin against the disk

was 10, 20, 30 N and the angular speed of the disk was 200, 300, 400 rpm which equals to 1.32, 1.88, 5.3 m/s. For hypo-

and hyper-EutecticAl-Si casting alloy;Ra = (0.2, 4) 0.05 m, on disc, made of AISI 1045 steel, and Ra = 0.15 0.05m,

Hv = 312 20 kg/mm2

were used for testing. The 0.2 mRa surfaces were obtained by superfinishing, while the 4mRa

surfaces were produced by a conventional grinding and abrasion with 60 grit Al 2O3 abrasive paper. Firstly, and before

testing, aluminum silicon disc was cleaned and dried using cotton and acetone as the weight of the samples were measured

using a digital balance and recording the values before and after the test for each test.

Chemical analysis was conducted for the aluminum-silicon casting alloy, also density, hardness and tensile

strength were studied due to its wide range of usages in industry, particularly in pistons as well as the cylinders. The

obtained chemical analysis is given in the Table 1. The testing of mechanical properties including hardness is given in

Table 2. The microscopic structure and the composition of microscopic samples are examined and shown in Fig. 2. It is

shown that Si particles are distributed uniformly, while the Si seems a bulk. The peaks in the X-ray of the hypo-and hyper-

Eutectic Al-Si casting alloy. Fig. 3 can be indexed as _Al, Si, C and the small relative areas of peaks are consistent with the

scanning electron microscopy (SEM) images give greater magnification and better depth. SEM is a specialized method

using a variable-pressure sample chamber. This technique allows direct evaluation of samples that are nonconductive or

vacuum sensitive.

Figure 1: Pin-on-Disc Wear Testing Machine

Table 1: Compositional Analysis of Hypo-and Hyper-Eutectic Al-Si Casting Alloy

Chemical Composition (Wt%)

TiZnPbSnMnNiFeCuMgSiAl

0.1571.6880.2920.3680.5470.2341.0011.480.30410.19Balance383 Al

-0.0120.0260.0120.0241.2241.1301.3041.17616.69Balance390 Al


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Table 2: Mechanical Properties of Hypo-and Hyper-Eutectic Al-Si Casting Alloy

Ultimate Tensile

Strength (MN m-2)

Tensile

StrengthMPa

Elongation

(%)

Hardness

(VHN)

Density

(kg m-3x 103)

Composition

(wt%)

185.480.05.881.02.74Al-10.19 %Si

189.02505.4112.652.72Al-16.69 %Si

Aluminum-silicon casting alloy was cleaned then starting an actual test of wear process and the hard substance

acetone with cotton and dry well was registered height and weight of samples accurately to provide a very precise and

digital recording of all data using a stopwatch to set a time slip and post-test. and continuously measuring the friction force.

At preselected times the pin wear was determined by measuring the wear-scar diameter. Friction force was recorded during

the wear tests. Specimens were ultrasonically cleaned in acetone for 5 min before and after wear tests.

The wear tracks were observed by SEM. Surface roughness was also measured by a stylus surface analyzer, with

the effective measure length 5 mm and the cutoff length, 5 mm. The work of hardening of contact surfaces due to the

friction shear was identified and determined by micro-Vickers indentation test.

Wear rate (WR) was estimated by measuring the mass loss (W) in the specimen after each test. Cares have been

taken after each test to avoid entrapment of wear debris in the specimen. It is calculated that Wto sliding distance (S.D)

using:

WR=W/S.D (1)

The volumetric wear rate (Wv) of the composite is related to density () and the abrading time (t), using:

Wv = W /t (2)

Specific wear rate (Ws) is employed. This is defined as the volume loss of the composite per unit sliding distance

and per unit applied normal load. Often the inverse of specific wear rate expresses in terms of the volumetric wear rate as:

Ws = Wv /S.D Fn (3)

The friction force was measured for each pass and then averaged over the total number of passes for each wear

test. The average value of friction coefficient () of composite was calculated from:

= Ff / Fn (4)

where Ff is the average friction force and Fn is the applied load with an assumption that the temperature isconstant at 33

oC.

Figure 2: The SEM Images of Microscopic Structures of (a) Hypo-and (b) Hyper-Eutectic Al-Si Casting Alloy


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Figure 3: X-Ray of the (a) Hypo-and (b) Hyper-Eutectic Al-Si Casting Alloy

RESULTS AND DISCUSSIONS

Materials Screening Tests

The experiments were performed with the object of studying the effect of sliding speed (S.S) is applied to the load

(L) and sliding distance (S.D) with dry friction and wear studies of the alloy. In the application of an orthogonal matrix

experiments, the dry friction wear performance of various combinations of parameters were obtained and are presented in

Table 3.

Table 3: Results of Dry Sliding Wear Tests of (a) Hypo-and (b) Hyper-Eutectic Al-Si Casting Alloy

Wear RateW.R X10-6

(N/m)

Volumetric Wear

Rate

W.VX10--12(m3/sec)

Specific Wear

Rate

Ws X10--13(m3/N-m)

FrictionCoefficient

RP

M

Load

(N)

Ra

m

0.11675.6204.2600.286200

10

4 0.05

(a)

0.10657.3333.8900.276300

0.098910.833.6110.355400

0.18048.6903.2900.273200

20 0.167811.543.0620.266300

0.152216.662.7770.261400

0.264512.703.2200.230200

30 0.215314.8122.6190.203300 0.198421.722.4140.268400

0.09684.6703.5400.270200

10

0.2

0.05(a)

0.08796.0513.2100.261300

0.08349.1323.0440.338400

0.14917.1802.7200.261200

20 0.13719.4332.5020.250300

0.121113.262.2110.273400

0.250012.003.0400.213200

30 0.203814.022.4790.196300

0.182119.942.2150.260400

0.10134.9183.7250.280200

10

4

0.05(b)

0.10046.9603.6920.270300

0.093010.273.4240.340400

0.16958.2293.1160.266200

20 0.159711.072.9370.260300 0.146616.182.6960.250400

0.251412.203.2910.226200

30 0.207414.372.5380.190300

0.191921.172.3520.260400

0.08544.1443.1390.266200

10

0.2

0.05(b)

0.08015.5592.9480.258300

0.08018.5582.8520.330400

0.14226.8192.5820.256200

20 0.12989.0032.3880.246300

0.114812.672.1110.260400

0.231711.072.7960.210200

30 0.192713.372.3640.190300

0.179120.092.2320.270400


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ANOVA results in variations in the overall impact of each variable for analysis. Table 4 presents the results of

the analysis should wear. The significance of this analysis is around 1% and 10%, 99% of confidence level for each of the

adjustments. The last column of the table shows the contribution of each variable. Percentage of total change (P)

determines that the effects are on the degree of contact pairs. If the "F test", F-value column (1%), the target variable, is

statistically significant, there is a reduction in the weight loss as compared to the higher values of applied load as

mentioned.

Table 4: ANOVA for Hypoeutectic 383 Al and Hypereutectic 390 Al alloys at Surface Roughness Average (Ra) = 0.2

0.05 m

Sum of

Squaresdf

Mean

SquareF Sig.

Wear rate W.R X10-

6 (N/m)

383 Al .021 2 .011 21.735 .002

390Al .021 2 .011 28.663 .001

Volumetric wear rate 383 Al 107.9 2 53.9 3.550 .096

390Al 109.2 2 54.6 3.606 .094

Specific wear rate 383 Al 2.22 2 1.111 9.592 .014390Al 1.308 2 .654 6.154 .035

Friction Coefficient 383 Al .008 2 .004 3.959 .080

390Al .008 2 .004 4.209 .072

Table 5: ANOVA for Hypoeutectic 383 Al and Hypereutectic 390 Al Alloys at Surface Roughness

Average (Ra) = 4 0.05 m

Sum of

Squaresdf

Mean

SquareF Sig.

Wear rate W.R X10-6

(N/m)

383 Al .023 2 .011 23.841 .001

390Al .022 2 .011 34.460 .001

Volumetric wear rate 383 Al 115.6 2 57.8 5.473 .044

390Al 116.8 2 58.4 4.899 .055Specific wear rate 383 Al 1.101 2 .550 5.389 .046

390Al .660 2 .330 6.024 .037

Friction Coefficient 383 Al .007 2 .003 3.354 .105

390Al .006 2 .003 2.532 .159

Since it has a highest contribution for the wear as mentioned in Table 5. But at higher applied load and sliding

speed, various types of aluminum Silicon alloys were tested under dry Sliding conditions. The wear and friction

characteristics of these alloys The wear and friction results obtained from aluminum Silicon alloys tests are given in

Tables 4/ and/5.

Effect of the Surface Roughness on the Friction and Wear

Both 383 Al and 390 Al alloys were tested with different surface roughness. The various types of aluminum

alloys were tested under dry sliding conditions and the effect of surface roughness on the friction and wear characteristics

were evaluated as compared to similar conditions and the results of friction and wear .The wear rate of 383 Al alloys dry

sliding has been studied and compared with 390 Al alloys ,based on the obtained results, it is plotted for different surface

roughness average (Ra) = (0.2,4) 0.05 m,. as shown in Fig. 4. It is noted for 10 N, at Ra= 4 m percentage of wear rate

equals 0.116703 X 10-6

(N/m) while for Ra= 0.2 m given 0.096882X 10-6

(N/m) In both cases, with the increase in load

the weight loss also increases which is equal to the first hour of testing then goes down slightly. The sliding occurs in very

small areas at the peaks, rupture or break these summits becomes more sliding accompanied by a rise in temperature ,


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while increasing the load causes increase in the friction rate, which in turn increases the destruction, surface wear reduces

the contact area and breaking the oxide layer causes an adhesion. The greatest amount of material transfer was found

under dry sliding conditions, thus giving rise to the wear depth and higher coefficient of friction. Material transfer between

the counter surfaces, based on the observation of wear debris being generated, occurred during dry sliding The wear of 383

Al alloys in dry sliding, as compared with the wear of 390 Al alloys, has some interesting features. While obtaining the

lowest wear with 390 Al alloys, which has the highest hardness and on the whole, the amount of wear decreases with

increasing silicon content, as well as the presence of copper, which gives the best resistance to corrosion. The alloys

progressed from a high-wear-rate region to a low-wear- rate region. The wear rate increases as load increases .The highest

roughness average means the highest wear rate and the correlation between wear rate and sliding distance is inversely. This

is the force required to cut the interdependence between the bumps. Little wear rate is a quality of the lower load, thus

reducing both the friction coefficient and wear depth.

Increase of load at 10 N shows that the results of the surface atRa=4m has the amount of specific wear equal to

Ws= 6.34 X 10-13

(m3/N-m), .These amounts depend on the surface roughness as well as increasing the wear rate. The main

reason for lacking wear resistance at the beginning of the test is attributed to the thin layer of material eroded between

bumps of the disk surface, while the sliding leads to hardness, low rate of wear and surface roughness. While the variation

of volumetric wear rate with normal load is direct , the relationship at 200 rpm is positively correlated linear and the

volumetric wear at the beginning of the test carries 10 N and it increases with the increase of load to 20 and 30 N. This is

because at higher load, the friction increases, which results in increased deboning and fracture under the conditions of the

tests conducted and results obtained indicate that there is significant effect of surface roughness on the wear rate

volumetric and weighed for both alloys. A similar effect of load on volumetric wear has been observed by M.Gupta .S.

Ling [18] Increasing the roughness can be noticed with increasing W.V of different rpm values due to same reason of

specific wear rate of lacking wear resistance of material with thin layer eroded between bumps of the disk surface. While

WV decreases as Ra decreases for the same rpm as cleared .As many parameters e.g. load, sliding distance and slidingvelocity are responsible for wear rate and were expressed in the earlier figures, it is more appropriate to express the sliding

wear results in terms of the wear constant as extracted from Archards law. For known, softer material, values of V (wear

volume), S (sliding distance), L (normal load), and the wear coefficient (K) can be determined from the following

equations:

V = K L S / H (5)

We note that an increase of load to 30 N leads to decrease of specific wear rate. Due to the period of rubbing, To

investigate the influence of sliding speed,

5 1 0 1 5 2 0 2 5 3 0 3 5

0 . 0 0

0 . 0 2

0 . 0 4

0 . 0 6

0 . 0 8

0 . 1 0

0 . 1 2

0 . 1 4

0 . 1 6

0 . 1 8 Y = 0 . 1 4 4 5 4 - 0 . 0 0 4 5 X + 8 . 8 9 1 3 3 E - 5 X2

l o a d = 1 0 NR P M = 2 0 0T e s t d u ra t i o n =6 h rs

WearRateX10-6N

/m

S l i d in g D i s ta n c e X 1 03

(me te r )

( A l - 1 0 S i ) , ( R a ) = ( 4 ) 0 . 0 5 m

( A l - 1 6 S i ) , ( R a ) = ( 4 ) 0 . 0 5 m( A l - 1 0 S i ) , ( R a ) = ( 0 . 2 ) 0 . 0 5 m( A l - 1 6 S i ) , ( R a ) = ( 0 . 2 ) 0 . 0 5 m

M e a n 4 C u v

A v e r a g e M e

p = 4 . 9 1 3 1 7 E - 4

Figure 4: Variation of Surface RoughnessRa = (0.2 and 4) 0.05 m and Wear Rate with Sliding

Distance of 200rpm at (a) 10 N


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Friction Coefficient and Wear Behavior

The friction coefficients for the aluminumsilicon alloys were measured and shown in The friction coefficients

for the aluminumsilicon alloys were measured and shown in Fig. 5. There is a direct relation between friction and surface

roughness ratio for the two alloys. As the ratio reduces, a reduction in friction occurs too.

The friction and wear characteristics which were measured for aluminumsilicon alloys, shows the variation of

coefficient of friction with normal load.

This shows that the friction coefficient in all cases decreases with the increase of load. This decrease in value

occurs as a result of the surface which makes the contacting area of the specimen smaller.

Higher friction but lower wear was observed for these alloys 390 Al compared with 383 Al . It is believed that

the increased friction was caused by sliding which is the result of plastic deformation between the sample and disk, which

resulted in strong adhesion and transmission of the sample metal to the disk.

10 15 20 25 30 35

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

0.45Y =0.25425+0.00376 X-1.6375E-4 X2load=10,20,30 N

RPM=200Test duration= 6 hrs

CoefficientofFriction,

Normal Load (N)

(Al-10Si), ( Ra) = (4) 0.05 m(Al-16Si), ( Ra) = (4) 0.05 m(Al-10Si), ( Ra) = (0.2) 0.05 m(Al-16Si), ( Ra) = (0.2) 0.05 mAverage of Graph16 Layer 1Polynomial Fit of Average1_Mean4Cuv

p=


9/14

The Tribological Behavior of Hypo-and Hyper-Eu

Surface Analysis of Worn Surfaces

Sample surface of the test, to che

curves were also to identify a profile curv

to be tested. However, further changes hav

graph, the disk surface, and the worn surfa

This wear and tear of previous o

and testing on a specific part of the obser

From these micrographs and the profile of

up to 50 m. From 50 to 200 meters, slowly

The worn surfaces of specimen of all the

Si alloy tested for 6 h corresponding to a sl

This shows damage smearing o

showed continuous deep scratches, groovechanges in the subsurface regions of the

the 383 Al alloy sample taken parallel t

highest hardness was obtained from the re

PhotogrRPM

0

200

300

400

Figure 6: (a) Surface Micrographs an

Wear Surface of 200,300 ,40

(a)Slidin

dir

ection

0.2

m

tectic Al-Si Alloys under Dry Sliding Conditions

k every time, it was the optical microscope. With the tes

s .Changes in surface topography and roughness of bot

e been observed on the sliding surface of the pin check.

e profile curves were used for analysis.

ne report the more pronounced features of the sliding c

ed sample. Photomicrographs and surface profile curves

the wear process, which is a sliding soft smoothing can

sliding wear process, which can be seen with the deepe

l-Si alloys were found to be similar to each other, and a

iding distance is given in Fig.6(a).

ver the worn surface. The worn surface of the 383 Al

s and gouging, was more comparable with the 390 Al sorn alloy samples. Fig. 6(b) shows a cross-section thro

the sliding direction which increased again to an alm

ion a, while the region b showed the lowest hardness,

Profile

CurvesPhotographs

Profile

Curvesphs

d Profile Curves of Specimen for Hypoeutectic 383 Al

0 rpm and Load 20 N (a)Ra = 0.2 0.05 m,(b) Ra =

20

m

4

m

Sliding

direction

(b)

17m

0.2m

4

m

119

t sample surface profile

the disk and the pin is

hus, the optical micro-

ntact between the data

are shown in Figure 4.

e seen from the curves

ing of the profile curve

micrograph for the Al-

sample which instead

ample . Microstructuregh the wear surface of

ost constant level. The

Casting Alloy after

0.05 m


10/14

120

PhotogrRPM

0

200

300

400

Figure 6: (b) Surface Micrographs an

Wear Surface of 200, 300, 4

Surface Morphology and Wear Mechani

The surface morphology of samp

Figures 7(a)-(b). Each AFM image was

average surface roughness (Ra)increases

hence it can support the adhesion improv

surface roughness on the reel, respective

single pass of rolling. However, the prop

reason is attributed to the presence of larg

383 Al and 390 Al alloys tested. In the Fi

383 Al, compared with 390 Al , the wear

be examined Chemical effects such as ox

that the scatter in the data was less.

In general the alloys of aluminu

study, in some cases we observe mass tr

difference between them in the hardness.

(a)

Sliding

direction

0.2

m

Riyadh A. Al-Samarai, Haftirman, Khairel

Profile

CurvesPhotographs

Profile

Curvesphs

Profile Curves of Specimen for Hypereutectic 390 A

0 rpm and load 20 N (a)Ra = 0.2 0.05 m (b) Ra = 4

sms

es was measured by AFM in contact mode on a 5 5

analyzed in terms of surface average roughness (Ra).

ith treatment time. The roughness of the surfaces increa

ement under dry sliding conditions . The tests were car

umbers can be from 4.4 to 4.5 to see that the surface c

ortion affected by the surface of the alloy is compared

r proportion of silicon in the alloy, which increases the

.7 we note a comparison between alloys the effect of we

ate on the surface is increased as load increases influenc

idative wear or interactions may. composition (chemica

are notorious in terms of contact with the steel unde

nsfer from the surface of specimen to the surface of di

15m

18m

4m

Slidin

gdirection

(b)

0.2m

4m

afezi Ahmad, Y. Al-Douri

Casting Alloy after

0.05 m

2area and is shown in

he data show that the

es with treatment time,

ried out. The values of

hanges after a few laps

with the alloy and the

surface hardness for the

ar larger surface during

wear behavior and can

property) in the sense

r the conditions of this

sk because of the great


11/14


Figure 7: Surface Comparisons under Different Loads (a) 10 N and (b) 30 N at Dry Sliding

Fig. 8, clearly shows that the tensile tribo-layer formed during the microscope, as described wear of the surface

an array of fracture Various sizes, micro-slot parallel circular particle slip and mainly in the micropores, Al, Si, C, O and

Ca.

Figure 8: (a) SEM Micrograph Illustrating the Texture of the Worn Surface with Small Particles Scattered

throughout, Smooth Exposed Si Particles for Hypereutectic 390 Al Alloy

(b) for Hypoeutectic 383 Al Alloy after Wear Surface

The relationship between them is a little complicated, but note the severity of the damage on the surface of

specimen especially in the high loads and when speed goesdown with the alloy. The same images of micrographs wear

surface show an increase as load increases as in Fig.9.

Plastic deformation and abrasion .Thus, as a result of wear and coefficient of friction and sliding distance to

steady-state conditions show very large deviations. tribological properties of all samples tested for dry for different speeds .

Si Si

(a)(b)


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To facilitate comparison, the comparison of samples from left to right, depending on the degree of wear and

coefficient of friction, Ra parameter is shows a low wear and coefficient of friction in390 (Al-16.69% Si) alloys than 383

(Al-10.19%Si) alloy for all sliding speeds, although they have the same average roughness.

However, the difference decreases with increasing sliding speed, decreases surface topography. In dry contact,

initial topography was changed due to abrasive wear, so the correlation between roughness parameters and tribological

behaviour is strong.

Roughness ProfilesSurfaces after TestRa m

4 0.05

0.2 0.05

4 0.05

0.2 0.05

Figure 9: 3D. Micro-Topographyof the Surfaces and Roughness Profiles of the Wear Tracks after Test

(a) Ra= 0.2 0.05 m (b) Ra= 4 0.05 m, of the 383 (Al-10.19% Si) Alloy (c) Ra= 0.2 0.05 m

(d) Ra= 4 0.05 m of the 390 (Al-16.69% Si) Alloy after 60 min , Test at Speed 3 mm/s

(c)Wear

Profile(m)

(a)Crack

Profile(m)

(b)

Wear

Profile(m)

(d)

Wear

Profile(m)


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CONCLUSIONS

In summary, using the investigated results, the following conclusion can be obtained:

For dry contact, the 383 Al and 390 Al alloys have approximately two orders of magnitude: higher wear rate with

increase as the surface roughness increases. The lowest wear rate is obtained with the 390 Al alloy compared with

383 Al.

The wear rate depths on 383 Al alloy were consistently smaller than those on 383 Al alloy.

The roughness parameter of Al-Si casting alloy attributes to the shape of asperities ofRaand has the strongest

influence on the wear rate.

The wear rate increases as load and roughness average increase, while it correlates inversely with sliding

distance.

In general, the amount of wear rate decreases as the amount of silicon content increases. This trend, however, is

complicated by the presence of other alloying elements.

The specific wear rate decreases as load increases, it correlates inversely with sliding velocity. The smoothness of

surface as well as sliding distance reduce the volumetric wear rate due to lacking wear resistance

The higher value of friction is attributed to the higher value ofRa and increases as the surface roughness increases,

it correlates inversely with load.

Coefficient of friction is lower when roughness is low.

With higher sliding speed, friction gets reduced under dry sliding conditions.

Increase in parameterRa, leads to decrease in friction and increase in friction for dry tests.

Dry contact sliding, distance to steady-state friction conditions, tends to get longer with increase in roughness.

ACKNOWLEDGEMENTS

The authors would like to express their thanks to Dr. Khairel Rafezi Ahmad, Dean of Engineering Materials for

their help, support and assistance.

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