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Journal of Mi nerals & Materials Characterization & Engineering, Vol. 10, No.5, pp.419-425, 2011
jmmce.org Printed in t h e USA. All rights reserved
Dry Sliding Wear Behaviour of SiC Particles Reinforced Zinc-Aluminium
(ZA43) Alloy Metal Matrix Composites
Rajaneesh N. Marigoudar1*, Kanakuppi Sadashivappa2
1Lecturer, Mechanical Engineering Department,
GM Institute of Technology, Davangere 577006, Karnataka, India
2Professor, Department of IPE, Bapuji Institute of Engineering & Technology,
Davangere 577004, Karnataka, India
*Corresponding Author: email@example.com
The present paper reveals th e wear behaviour of Zinc - Alu minium alloy reinforced with SiC
particulate metal matrix composite. The composite is prepared using liquid metallurgy
technique. The unlubricated pin-on disc wear test is conducted to find the wear beha viour of
the ZA43 alloy based composite. The sliding wear test is conducted for different load, speed
and time. The result reveals that wear rates of composite is reduced as reinforcement
increases. For the same working conditions wear rate increases with increasing load and
with increasing speed. The tested samples are examined by taking micro structure photos and
analyzed for the type of wear. Dominating wear types observed are delamination and
Keywords: SiC/ ZA43 composite, particulate metal matrix composite, Zinc-Aluminium alloy,
abrasive wear, delamination.
The metal matrix composites (MMCs) reinforced with ceramic dispersoids, are showing
properties like light weight and high strength. Because of the properties, MMCs captured
large area of applic ations. The MMCs posses exc ellent mechanical and tribological properties
and are considered as potenti al engineering materials for various tribological applications [1-
5]. Several researchers have worked on sliding wear mechanism of MMCs reinforced with
ceramic particulates like SiCp, Al2O3 and even short fibers etc, and have observed
improvement in wear and abrasion resistance . Further, the increased percentage of these
reinforcements contributed in increased hardness and density of the composites [11 ]. Wear is
420 Rajaneesh N. Marigoudar, Kanakuppi S adashivappa Vol.10, No.5
a common mechanism which is observed in machine tools and its components, which is a
slow process. However, if the rate of w ear on particular machine component is high, so that it
requires frequent repair and replacement, then it may constitute a wear problem. ZA based
alloy reinforced with ceramic particles exhibit good wear resistant properties . The MMC
is tested under various conditions by varying parameters like speed and load. In particular ZA
based MMC shows higher abrasion and wear resistant under variable conditions . In the
present study the composite is prepared by stir casting technique. The specimen is subjected
to dry sliding condition using pin on disc wear testing machine . The worn-out specimen is
analyzed for nature of wear.
2. MATERIALS AND EXPERIMENTATION
The chemical composition of ZA43 base alloy is shown in Table 1. Aluminium which is in
higher percentage responsible for increase in hardness of base alloy , further increase in
hardness is due to reinforcement in MMC.
Table 1 : Composition of ZA43 alloy (wt. %)
SiC particles are introduced in to the matrix by liquid metallurgy technique shown in Fig. 1.
The percentage of SiC (30µ) is varied between 1%- 5% in steps of 1% by weight. The matrix
material is heated above its melting temperature i.e. 7500 C. The molten matrix is stirred
using stirring mechanism; meanwhile pre heated SiC particles are introduced into the molten
matrix. Pre heating of SiC improves the wettab ility with molten metal and magnesium in the
small percentage also improves the wettability . Stirring of the mixture is continued till
whirl is formed and uniform distribution of particles takes place. This molten mixture is
poured into cast iron die. Mixture is allowed in the die to attain the room temperature. The
solidified specimen is remo ved from the die and tested. S tirring blades are coated wit h zircon
which reduces the diffusion of steel in to the molten metal.
Wear testing specimen is casted according to ASTM G99. A pin on disc wear testing
configuration is used to check wear properties of composite specimen. The specimen is
rubbed against rotating hard steel disc without any lubricant. Dry sliding method is followed .
Variable parameters such as speed, which is varied between 1.2 m/s to 5.1 m/s and load is
varied between 10 N to 40 N. Common track diameter of 120mm is used to test the specimen.
After testing, the specimen is removed from the machine and weighed. Difference in initial
and final weight gives the loss of material in turn wear rate of the material. The specimen is
Vol.10, No.5 Dry Sliding Wear Behaviour 421
weighed using electronic balance. Tests are conducted at normal room temperature. The
principal objective of inves tigation was to s tudy the effect of variation of normal load, sliding
velocity and percentage SiC on wear rate.
Figure 1. Stir casting setup for MMC fabrication
3. RESUL TS AND DI SCUS SION
Abrasive wear has been defined as the displacement of material caused by hard particles or
hard proturberances where these hard particles are forced against and moving along a solid
surface. By incorporating the SiC particles in to the matrix, the sliding wear properties are
enhanced [1, 2]. The har dness of the specimen increases and fluidity decreases. The effect of
variable load and speed on specimen wear is checked against variable reinforcement
The effect of applied normal load on the MMC with different SiC reinforcement percentage
is shown in Figure 2. In this test, for constant speed of 3.7 m/s, load is increased in steps of
10N. The test is conducted for normal loads of 10, 20, 30 and 40N. It is observed that wear of
the composite specimen decreases with increase in SiC percentage [9,10]. This happens
because of SiC, which is hard material which improves the hardness. For specimen with 1%
reinforcement with 10N load, almost wear is negligible. As load is increased, increase in
wear is observed. Decreasing trend is observed with increase in reinforcement. For 5%
reinforcement load is increase, less weight loss is observed.
422 Rajaneesh N. Marigoudar, Kanakuppi S adashivappa Vol.10, No.5
10 20 30 40
Loa d, N
Weight loss, g
Figure 2. Variation of weight loss with applied load
For a load of 40 N microstructure photographs of the specimen with 2% and 5%
reinforcement subjected to different loading condition is taken. It is observed form the Figure
3(a) and 3(b) that at grooves are formed in the direction of rotation of disc. Due to friction,
increase in temperature is observed, hence softening of the specimen is observed.
Delamination of the specimen is observed and deep grooves are formed on the surface.
Sometime particle pull-out is observed. Wear debris are also observed.
Figure 3. Microstructure photograph of worn surface when subjected to varying load (a)
2% SiC and load of 40 N and (b) 5% SiC with load of 40 N.
The effect of varying speed on MMC with varying SiC is shown in Figure 4. Load is kept
constant at 40N and speed is varied 1.2, 2.5, 3.7 and 5.1 m/s. From the graph, it is observed
that higher wear of MMC w ith in creas e in speed. For 1% reinf o rcement, as speed is incre as e d
higher material loss is observed. For same conditions, when reinforcement is increased to 5%,
less material loss is observed. Again this is due to increase in hardness of MMC. Hard
reinforcement is responsible for increase in hardness.
Vol.10, No.5 Dry Sliding Wear Behaviour 423
1.2 2.53.7 5.1
Weight loss, g
Figure 4. Variation of weight loss with increasing speed
Microstructure photographs of the specimen with 2% and 5% SiC are tak en. The Figure 5(a)
for 1.2m/s speed and 5(b) for 5.1m/s, reveals that material removal and worn-out surface of
composite with 2% and 5% . As speed is gradually increased, initially small scratches are
formed on the surface and gradually they get converted in to grooves. Even small craters are
also formed because of the delamination. Scissoring action is observed on the surface. The
grooves formed on the surface are in the direction of sliding.
Figure 5. Microstructure photograph of worn surface with 2% and 5% SiC subjected to
varying speed (a) Speed 1.2 m/s and load of 40 N (b) Speed 5.1 m/s and load of 40N.
It is observed from the microstructure image, loss of material is due to high friction between
MMC and rotating disc. In both the conditions that, predominant wear occur due to
delamination and abrasion. It is also observed that material adhere to the disc due to high
temperature and even undergo plastic deformation some time material become soft and it
may melt .
424 Rajaneesh N. Marigoudar, Kanakuppi S adashivappa Vol.10, No.5
This paper reports the wear properties of ZA43 alloy reinforced with SiC particulate MMC.
Zinc based MMC shows lower co-efficient of friction under dry sliding condition. Th e MMC
is prepared using liquid metallurgy technique. The standard specimen prepared is subjected to
dry sliding wear test.
It is observed that the composite with 1% reinforcement at low load of 10 N, shows less
wear and as load is increased to 40 N, material exhibit higher wear. For the same testing
conditions, as reinforcement is increased to 5%, decrease in wear is observed.
For constant load of 40 N and at speed of 1.2 m/s, composite with 1% reinforcement shows
lower wear and as speed is increased wear of the specimen increases. As the speed is
increased to 5.1 m/s, wear increases. For the same testing conditions, as reinforcement is
increased to 5%, wear decreases.
The presence of reinforcement restricts the growth of micro cracks and delamination.
Combination of delamination and abrasive wear is observed during the test. Sometimes
adhesion and melting of the specimen are also observed.
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