Journal of Minerals & Materials Characterization & Engineering, Vol. 8, No.10, pp.813-819, 2009
jmmce.org Printed in the USA. All rights reserved
813
Study of Wear Properties of Al-SiC Composites
Manoj Singla1, Lakhvir Singh2, Vikas Chawla3
1 Department of Mechanical Engineering, R.I.E.I.T., Railmajra, Distt. Nawanshahr (Pb.)-
144533, INDIA
2 Department of Mechanical Engineering, BBSBEC, Fatehgarh Sahib (Pb.), INDIA
3 Department of Materials & Metallurgical Engineering, I.I.T. Roorkee (Uttaranchal) , INDIA
Contact: , [e-mail]2, [e-mail]3
ABSTRACT
Al–SiC composites containing four different weight percentages 5%, 10%, 20% and 25% of SiC
have been fabricated by liquid metallurgy method. Friction and wear characteristics of Al–SiC
composites have been investigated under dry sliding conditions and compared with those
observed in pure aluminium. Dry sliding wear tests have been carried out using pin-on-disk
wear test rate normal loads of 5, 7, 9 and 11 Kgf and at constant sliding velocity of 1.0m/s.
Weight loss of samples was measured and the variation of cumulative wear loss with sliding
distance has been found to be linear for both pure aluminium and the composites. It was also
observed that the wear rate varies linearly with normal load but lower in composites as
compared to that in base material. The wear mechanism appears to be oxidative for both pure
aluminium and composites under the given conditions of load and sliding velocity as indicated
by scanning electron microscope (SEM) of the worn surfaces. Further, it was found from the
experimentation that the wear rate decreases linearly with increasing weight fraction of silicon
carbide and average coefficient of friction decreases linearly with increasing normal load and
weight fraction of SiC. The best results have been obtained at 20% weight fraction of 320 grit
size SiC particles for minimum wear.
Key Words: Metal Matrix Composites MMC’s, Silicon Carbide SiC

814 Manoj Singla, Lakhvir Singh, Vikas Chawla Vol.8, No.10
1. INTRODUCTION
A composite material is a ‘material system’ composed of a combination of two or more micro or
macro constituents that differ in form, chemical composition and which are essentially insoluble
in each other.
The motto to design MMCs is to combine the metals & ceramics i.e. addition of high strength,
high modulus refract o r y p ar t ic l es to ductile metal matrix to get tailor made properties.
In the present work, an effort has been made to study wear properties with varying weight
fraction of SiC in particle reinforced MMCs developed with the help of two - step mixing
method of stir casting technique.
2. EXPERIMENTAL PROCEDURE
The standard samples Fig. 2 (pins – cylindrical shape) have been prepared (Ø8mm X 25 mm )
out of castings (Fig. 1) having different wt. % of SiC.
Figure 1. Pictorial view casting of sample Figure 2. Standard samples for wear test
containing different % SiC by weight
2.1 Wear Test
Dry sliding wear tests for the aluminium & composites have been conducted using pin-on-disc
machine model TR – 20 supplied by M/S Ducom , Bangalore (India). The tests have been
conducted in air. Wear tests have been conducted using cylindrical samples (Ø8mm X 25 mm)
that had flat surfaces in contact region and the rounded corner. The pin is held stationary against

Vol.8, No.10 Study of Wear Properties of Al-SiC Composites 815
the counter face of a 100mm diameter rotating disc made of En-32 steel having a hardness of
HRC65 as provided on pin-on-disc machine. The wear tests have been conducted under the four
normal loads 50, 70, 90, 110 N and at fixed sliding speed of 1.0m/s. Each wear test has been
carried out for a total sliding distance of 1.8 km. Tangential force has been monitored
continuously. Pin weight loss has been measured at intervals of 5 minutes to determine wear
loss. Weight loss data has been converted to volume loss data using the density of pure
aluminium 2680kg/m3 and density of 2688 kg/m3, 2698kg/m3, 2718kg/m3 & 2726 kg/m3,
respectively, for the composites having 5%, 10%, 20% & 25% SiC contents, respectively. The
pin is removed from the holder after each run, properly cleaned using acetone. The weight loss
has been taken in a digital balance having least count of 1mg. The pin weight is measured after
every 5 min of sliding and six data points have been taken in a total duration of 30 min. Disk has
been cleaned with acetone after each run to remove debris.
The friction coefficients have been determined from the friction force and normal loads.
2.2 SEM Study of Composite Samples
SEM analysis of the post mechanical tests was carried out to study the worn out surfaces under
different applied loads.
SEM analysis was done on JOEL make SEM at Sophisticated Analytical Instrumentation
Facility, Central Instrumentation Laboratory, Panjab University, Chandigarh.
3. RESULTS AND DISCUSSION
3.1 Results
Fig. 3 (a –e) shows the variation of cumulative wear volume with sliding distance under different
loads and at fixed sliding velocity of 1.0m/s for pure aluminium (S1) and composites S2, S3, S4,
S5, respectively. It is observed that the volume loss increases linearly with increasing sliding
distance. However the cumulative volume loss of composites is lower than that observed in pure
Al and decreases with increasing volume fraction of SiC up to 20% as is evident from Fig. 3 (b-
d) and there after for 25% SiC wear loss again increases slightly & thus reverses the trend of
decreasing wear volume loss with increase in SiC weight %. This trend is due to clustering of
SiC particles and then due to increase in weight settling down at the bottom & non – uniform
mixing in Al matrix.
Fig. 4 shows the variation of cumulative wear volume with normal applied loads & volume loss
is increasing with increasing normal loads. Wear volume loss is maximum for pure aluminium &
then decreases as the % SiC increases upto 20% again this trend changes for 25% SiC content
because of non-uniform mixing.

816 Manoj Singla, Lakhvir Singh, Vikas Chawla Vol.8, No.10
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Fig. 3. Variation of cumulative volume loss with sliding distance
30
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012345678910111213
Pure Al
5% SiC
10% SiC
20% SiC
25% SiC
Fig. 4 Variation of cumulative volume loss with normal load
Sliding Distance (m)
Cumu. Wear Vol. (mm3 X 10 -1)
Cumu. Wear Vol. (mm3
X 10 -1)
Cumu. Wear Vol. (mm3 X 10 -1)
Cumu. Wear Vol. (mm3 X 10 -1)
Cumu. Wear Vol. (mm3 X 10 -1)
Sliding Distance (m) Sliding Distance (m)
Sliding Distance (m)
Sliding Distance (m)
Normal Load (kgf)
Cumu. Wear Vol. (mm3 X 10 -1)

Vol.8, No.10 Study of Wear Properties of Al-SiC Composites 817
Fig. 5 (a-e) shows the variation of coefficient of friction with sliding distance, friction
coefficients fluctuates around the mean level and decreases as the sliding progresses. This trend
is similar in all the materials. The fluctuations in the coefficient of friction may be due to
variation in contact between sample and disk. Composites have shown lower coefficient of
friction in comparison to pure aluminum.
Fig. 6 shows the variation of average coefficient of friction with increasing load. It is observed
that average coefficient of friction decreases linearly with increasing load. Average value of
coefficient of friction for pure Al is 0.6 & for composites decreases as the % SiC increases.
Coefficient of friction for 25% SiC composite fluctuates between coefficient of friction for 5%
(S1) & 10% (S2) SiC .
0
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Fig. 5 Variation of Coefficient of Friction with sliding distance
Coefficient of friction
Sliding Distance (m)
Coefficient of friction
Coefficient of friction Coefficient of friction
Coefficient of friction
Sliding Distance (m) Sliding Distance (m)
Sliding Distance (m)
Sliding Distance (m)

818 Manoj Singla, Lakhvir Singh, Vikas Chawla Vol.8, No.10
0
0.2
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Pure Al
5%SiC
10%SiC
20%SiC
25%SiC
Fig. 6 Average Coefficient of Friction Vs Load
3.2 Discussions
3.2.1 Wear of worn surfaces
Fig. 7 (a-d) shows the scanning electron micrograph of worn surfaces of pure aluminium under
different applied loads.
Fig. 8 (a-d) shows the scanning electron micrograph of worn surfaces of Al – 20% SiC
composite. A transfer layer of compacted wear debris along with the wear tracks can be observed
over the sliding surface. This layer reaches a critical thickness before being detached resulting
eventually in generation of wear debris. The extent of cover provided by this transfer layer is
determined by the load, sliding speed and it increases with increasing load because of the
increased frictional heating and hence better compaction. The other reason for lower wear rate in
composites is their high hardness as compared to pure aluminum resulting in lower real area of
contact and therefore lower wear rate.
Normal Load (N)
Coefficient of friction

Vol.8, No.10 Study of Wear Properties of Al-SiC Composites 819
(a) 50 N (b) 70 N
(c) 90 N (d) 110 N
Fig. 7. Scanning Electron Micrographs of worn surfaces of Pure Al.

820 Manoj Singla, Lakhvir Singh, Vikas Chawla Vol.8, No.10
(a) 50 N (b) 70 N
(c) 90 N (d) 110 N
Fig. 8. Scanning Electron Micrographs of worn surfaces of Al- 20% SiC.
4. CONCLUSIONS
The experimental s t u d y reveals following conclusions:
1. For a given load, the cumulative wear volumes of composites and pure aluminium pins
increase linearly with sliding distance under dry sliding.
2. The wear rate increases linearly with the increase in normal load. However, the
composites have shown a lower rate of wear (up to 20% SiC) as compared to that
observed in pure aluminium.
3. The average coefficient of friction decreases with increasing load in both pure aluminium
and composites. However, the composites show a lower coefficient of friction than that
observed in pure aluminium.

Vol.8, No.10 Study of Wear Properties of Al-SiC Composites 821
ACKNOWLEDGEMENT
The author acknowledges with thanks the support provided by Department of Mechanical
Engineering, RIEIT, Railmajra, Distt. Nawanshahr & BBSBEC, Fatehgarh Sahib for carrying out
the experimentation work.
REFERENCES
1. Naher, S., Brabazon, D. and Looney, L. (2003), “Simulation of the stir casting process”,
Journal of Materials Processing Technology, Vol. 143-144, pp. 567-571.
2. Balasivanandha, S., Kaarunamoorthy, L., Kaithiresan, S. and Mohan, B. (2006), “Influence
of stirring speed and stirring time on distribution of particles in cast metal matrix composite”,
Journal of Material Processing Technology, Vol. 171, pp. 268-273.
3. Chen. M.Y. (2002), “Friction behaviour of co- continuous alumina/aluminium composites
with & without SiC reinforcement”, Wear, Vol. 249, pp. 868-876.
4. Dasgupta Rupa, (2005) “SiC particulate dispersed composites of an Al–Zn–Mg–Cu
alloy:Property comparison with parent alloy”, Material Characterization, Vol. 54, pp. 438-
445.
5. Hashim. J. (19990, “Metal matrix composites: production by stir casting method”, Journal of
Material Processing Technology, Vol. 92-93, pp. 1-7.
6. Lim. S.C., Gupta M., Ren. L., Kwok. J.K.M., “ The tribological properties of Al-Cu/SiCp
metal-matrix composites fabricated using the rheocasting technique”, Journal of Materials
Processing Technolo g y , V ol. (89-90), pp. 591-596..
7. Mares, M. (2001), “ Some issues on tailoring possibilities for mechanical properties of
particulate reinforced metal matrix composites” Journal of Optoelectronics and Advanced
Materials, Vol. 3 (1), pp. 119 – 124.
8. Min Zhao, Gaohui Wu, Longtao Jiang, Zuoyong Dou,(2005) “ Friction and wear properties
of TiB2P /Al Composite”, Composites Part: applied science and manufacturing,
9. Naher, S., Brabazon, D. and Looney, L. (2004), “Development and assessment of a new
quick quench stir caster design for the production of metal matrix composites”, Journal of
Material Processing Technology, Vol. 166, pp. 430-439.
10. Rajnesh, T. (2005), “Synthesis and tribological characterization of in-situ cast Al-TiC
composites”, Journal of Wear, 259, pp. 569-576.
11. Rohatgi, P.K., Sobezak, J., Asthana, R. and Kim, J.K.(1998), “Inhomogeneities in silicon
carbide distribution in stirred liquids-water model study for synthesis of composites”,
Materials Science and Engineering , Vol.252 (1), pp. 98-99.