ORIGINAL PAPER

Dry Sliding Wear Behavior of Zircon Sand Reinforced Al–Si Alloy

Kamalpreet Kaur • O. P. Pandey

Received: 20 January 2010 / Accepted: 3 May 2010 / Published online: 19 May 2010

� Springer Science+Business Media, LLC 2010

Abstract The emerging demand of light weight alloys and

composites for the engineering and structural applications

leads to explore the possibility to develop new techniques to

achieve materials of high performance. In the present study,

Al–Si/zircon sand reinforced composite has been developed

via spray forming technique. Dry sliding wear behavior of as

cast Al–Si base alloy and spray formed Al–Si/zircon sand

reinforced composite containing 8% Vf of zircon sand has

been analyzed. An isotropic wear property of spray formed

composite has been checked by selecting the spray formed

preform in both horizontal and vertical sections of deposit.

The wear tests which were carried out at loads of 14.7, 24.5,

34.3, 44.1, and 53.9 N have shown that spray formed

composite is more wear resistant in comparison to the cast

Al–Si alloy. Moreover, wear coefficient in case of com-

posite is also found to be lower than base alloy. Optical and

scanning electron microscopies have been carried out to

furnish a suitable explanation for observed wear behavior of

composite and alloy.

Keywords Adhesive wear � Wear mechanisms �SEM � Wear particle analysis

1 Introduction

In the last few decades, aluminum metal matrix com-

posites (AMCs) have drawn considerable attention as fuel

efficient advance materials for tribological applications.

The desirable mechanical properties can be achieved by

varying the reinforcing materials and their volume frac-

tion in the composite. Many processing techniques have

been developed successfully to manufacture metal matrix

composites (stir casting, die-casting, and powder metal-

lurgy) on the commercial scale. Among these spray

forming combines the benefits of microstructural refine-

ment and alloying flexibility. Spray forming is one of the

non-equilibrium processing techniques, in which micro-

structure is refined by rapid solidification effects. The

choice of processing technique for AMCs is very impor-

tant. The study of cast aluminum containing particles

Al2O3 and SiC showed settling of particulates in the sand

mold [1]. However, this can be eliminated in spray

forming process. It is a near net-shape processing tech-

nique combining atomization and deposition of liquid

melt in single step, whereas the other P/M and ingot

metallurgy routes contain large number of processing

steps. Hence, the spray forming reduces the number of

secondary processes and thus resulting in reduction in the

cost of the product [2].

Spray forming was initially proposed by Singer [3] at

University College Swansea, and nowadays it has got

industrial attraction for conventional alloys as well as

advanced high performance composites. The microstruc-

tural refinement and uniformity in distribution of rein-

forcement in the matrix depend upon melt superheat,

nozzle to substrate distance, metal to gas flow rate and high

heat removal rate at the droplet–gas interface [4, 5]. Further

microstructural refinement and reduction in porosity can be

achieved by using spray rolling [6], low pressure spray

forming [7], and secondary processes like hot rolling or

extrusion [2]. Tensile tests at the ambient and elevated

temperatures reveal that spray processed Al–Si alloys have

K. Kaur � O. P. Pandey (&)

School of Physics and Materials Science, Thapar University,

Patiala 147 004, Punjab, India

e-mail: oppandey@thapar.edu

K. Kaur

e-mail: kamalpreet.phd@thapar.edu

123

Tribol Lett (2010) 38:377–387

DOI 10.1007/s11249-010-9620-6

better strength and ductility than processed by conventional

ingot metallurgy route [8–10].

The nature of wear is highly influenced by the method of

processing, size, type, and amount of ceramic reinforce-

ment. Moreover, hard particulates in the soft metallic matrix

help to reduce wear loss in comparison to base soft metal. A

lot of literature is available on the reinforcement of various

particles (SiC, Al2O3, TiO2, TiB2, etc.) in spray deposited

composites, which give better physical and mechanical

properties as compare to their cast counterparts [11, 12].

Also the spray deposition process has the potential to pro-

duce large particulate-reinforced MMC ingot. The SiCp

reinforced AMC up to 15% volume fraction (Vf) showed the

uniform distribution of particles with good bonding between

particle–matrix interface in the high density matrix with low

segregation of SiCp [13]. Similarly, spray processed and hot

extruded AA7475 with 20% Vf of SiC billets showed Mg2Si

precipitation at the matrix–particle interface [14]. Pai et al.

[15] found that Mg improves wetting of dispersoid by

increasing its surface reactivity and decreasing the solid/

liquid interfacial energy at the dispersoid matrix interface.

Addition of SiC in 2014Al alloy gave rise to considerable

improvement in wear resistance [16]. The wear resistance of

spray processed Al–Si/SiCp composite can be further

enhanced by thermomechanical treatment and with

increasing Si content [17].

Recently, AMCs reinforced with zircon sand has been

found to be more economical and suitable AMC because of

higher fracture toughness of zircon than SiC. Zircon having

good hardness, modulus of elasticity, and excellent thermal

stability, is being studied for AMCs where contacting parts

operate in relative motions. Banerji et al. [18] in Al–11.8

Si–3 Mg system dispersed 25–30% zircon particles by

stirring and N2 degassing. The process of pressure die-

casting is required as the fluidity of melt decreases above

30%. Moreover, with dispersion of zircon particles in

Al–3% Mg alloy hardness, abrasive wear test, elastic

modulus, 0.2% proof stress, and tensile tests were

improved. Ejiofor et al. [19] made an attempt to manu-

facture low-cost double compaction P/M route in zircon

reinforced Al–13.5 Si–2.5 Mg alloy. Their structure anal-

ysis showed significant improvement in mechanical and

load bearing properties, which is attributed due to intrinsic

hardness of zircon as particulate-reinforced effect.

Similarly, Jangg et al. [20] produced lightweight and

higher wear resistant Al camshaft belt pulleys for engines

from standard Al powder mixtures with the addition of 10

mass% of ZrSiO4 by pressing, sintering at optimized

parameters and sizing. Both dimensional and wear prop-

erties were found to be comparable to those of conven-

tional iron pulleys. Abrasive wear of Al–4.5% Cu matrix

reinforced with Al2O3 and ZrSiO4 particulate showed that

wear resistance property of the composite increases with

the decrease in the particle size [21]. Furthermore, the

zircon reinforced composite showed high resistance to

wear in comparison to the alumina reinforced composite

[21].

The present work is focused on the spray deposition

processing of zircon sand reinforced near eutectic Al–Si

piston alloy and its tribological application. Earlier work

on stir cast zircon sand reinforced Al–Cu alloy composite

is available in literature [21]. The tribological applicability

has been explored with wear test of base alloy and com-

posite in light of microstructural features of worn pin

surfaces and debris.

2 Experimental Procedure

The Al–Si/zircon sand composite has been prepared by the

spray atomization and co-deposition process. The obtained

Al–Si alloy composition was analyzed by wet chemical

analysis and X-ray florescence technique as shown in

Table 1. The spray atomization apparatus consists of four

major units, i.e., melting furnace, atomization zone,

injector assembly, and deposition surface [22]. For spray

forming, the Al–Si alloy is melted in a graphite crucible in

a muffle furnace at 750 �C. After cooling the melt to

700 �C, it is poured in the convergent divergent nozzle

assembly. Before pouring high pressure nitrogen gas is

allowed to pass through the divergent section of the nozzle.

The aerodynamic forces exerted by high velocity nitrogen

gas jets atomize the molten metal stream into fine droplets.

The parameters used for spray atomization are shown in

Table 2. Injectors are used to incorporate zircon sand

particles in the spray cone. Several interactions do take

place in the atomization zone that includes the gas–liquid

interaction, formation of micron sized droplets, droplet–

droplet collisions, and droplet–particulate collisions. The

zircon sand particles are released in the atomizing zone

near the melt delivery tube. These injected particles pos-

sess sufficient kinetic energy and droplet–particle collision

Table 1 Composition of Al–Si alloy

Alloy Si Fe Cu Mn Mg Zn Ti Ni Pb Sn Al

XRF 11.166 0.332 1.247 0.598 0.849 0.250 0.026 0.868 0.001 0.002 Balance

Chemical analysis 11.800 0.365 1.230 0.411 0.940 0.210 0.0254 0.940 0.0289 0.005 Balance

378 Tribol Lett (2010) 38:377–387

123

occurs in the beginning of the atomizing zone which may

give rise to penetration of the particles inside the droplet.

The droplets get solidified and build up preform of diam-

eter 150 mm. For wear testing, the samples were cut from

different areas of the preform. The X-ray diffraction pat-

terns of the prepared sample was recorded on Panalytical

X’pert Pro MPD, Netherland using Cu Ka radiation

(k = 1.54 A). The collected data were matched with ref-

erence data for identification of different phases.

Dry sliding wear tests of the reinforced and unreinforced

alloys have been performed under the ambient tempera-

tures between 25–30 �C and relative humidity between 25–

42%, using a pin-on-disc wear and friction monitor (Model

TR-20, Ducom, Bangalore). The cylindrical shaped sam-

ples (25 9 9 mm) of base Al–Si alloy, spray formed Al–

Si/zircon sand composite sectioned vertically and hori-

zontally were tested against the hardened EN32 steel disc

having chemical composition (0.14% C, 0.52% Mn, 0.18%

Si, 0.13% Ni, 0.05% Cr, 0.06% Mo, 0.019% P, 0.015% S,

balance Fe) and hardness 65 HRC. Before testing, each

specimen is ultrasonically cleaned in acetone. Wear rate

has been calculated by measuring weight loss at different

time intervals. Archimedes’s principle is used to measure

the density of both reinforced and unreinforced material.

The wear tests of one specimen from each set have been

conducted up to 2,880 m run at a constant sliding velocity

of 1.6 m s-1 and under five different loads 14.7, 24.5, 34.3,

44.1, and 53.9 N for both reinforced and unreinforced

alloy. The scanning electron microscope and EDS (SEM

Quanta, 200 FEG, FEI Netherland) is used for micro-

structural examination of specimen, analyzing worn sur-

faces, and debris collected during the test.

3 Results and Discussion

3.1 XRD and Microstructure

The XRD pattern (Fig. 1) shows the presence of Al, Si, and

ZrSiO4 in the composite. During atomization 10% Vf of

zircon sand was injected. However, only 8% Vf of it could

be incorporated. SEM micrograph (Fig. 2) shows the

morphology and distribution of particles in the Al–Si/

zircon sand composite. The zircon particles are angular in

shape and particle distribution is nearly homogeneous.

3.2 Wear Characteristics

3.2.1 Effect of Sliding Distance on Wear Rate

The wear rate behavior against sliding distance has been

recorded at each load for both base Al–Si alloy and Al–Si/

zircon sand composite as shown in Fig. 3a–c. Figure 3a

shows the results of wear rate for Al–Si alloy at different

loads and constant sliding velocity of 1.6 m s-1. Under an

applied load two different type of wear behavior can be

predicted from the curves. Fluctuating, unstable and greater

wear at the initial stage corresponds to the run-in wear. On

the other hand, constant wear rate has been obtained at later

stage corresponding steady state wear. For both reinforced

Table 2 List of spray atomization parameters

Particulate size 106–125 lm

Weight of the charge 1.5 kg

Melt temperature 700 �C

Nozzle to substrate distance 300 mm

Inner diameter of melt delivery tube 8 mm

Nitrogen gas pressure 100 kg cm-2

Injector orifice diameter 1 mm

10 20 30 40 50 60 70 80 90 100

Δ

Δ

Δ

Δ

Δ

♦♦♦♦

⊗ ⊗

⊗

⊗

⊗

⊗

⊗

Inte

nsi

ty (

arb

itra

ry u

nit

s)

2θ (degrees)

Δ Al♦ Si⊗ ZrSiO

4

Fig. 1 XRD of Al–Si alloy, reinforcement and spray formed

composite

Fig. 2 SEM micrograph of spray formed preform

Tribol Lett (2010) 38:377–387 379

123

and unreinforced materials, a steady state is approachable

after 1 km sliding distance for all applied loads. These

results are analogous to dry sliding block-on-ring wear test

of squeeze cast A390 reinforced with 20% SiC at 45 N and

3.3 m s-1 observed by Ma et al. [23]. Wear rate was also

found to increase in ascending order with applied loads.

Similar findings have been also reported by Chaudhury et al.

in the Al–2Mg–TiO2 system for spray and stir cast com-

posites [24]. In the run-in wear regime, the wear rate has

been calculated after each 96 m sliding distance. The

splitting of the peaks occurring at some point in the run-in

wear regime can be seen in Fig. 3b, c which corresponds to

the debris build up phenomenon. The mechanical welding of

the plastically deformed material at the edges of the pin

leads to small wear rate during a short run. In the next short

run, this welded part got detached from the edges giving rise

to the second peak in wear plots. In both vertically and

horizontally sanctioned spray formed Al–Si/zircon sand

composite, mode of stabilization of wear got delayed for

53.9 N load. The schematic view of the droplets in spray

formed material and sliding direction in the wear tests for

both vertical and horizontal section is shown in Fig. 4. The

wear debris morphology can also be explained on the basis

of deposition mode of droplets. In horizontal section there is

larger number of nodes formed by the droplets as compare to

the vertical section. The mechanical welding of the droplets

is greater in horizontal section (Fig. 3c) which leads to

smaller run-in wear and thus achieving earlier steady state

wear rate (even at higher loads) as compare to Fig. 3a, b. On

comparing the wear rate at each load it has been found that

the wear resistance offered by spray processed composite is

higher than base Al–Si alloy with incorporation of harder

phase (zircon sand particles). This shows the good interfa-

cial bonding of zircon sand particle and matrix phase.

Moreover, stabilization of wear rates for both horizontally

and vertically cut samples are identical indicating isotropic

wear nature of the spray formed preform. Further, micro-

structural analysis of the wear surfaces and wear debris is

necessary to understand the wear mechanism completely.

3.2.2 Effect of Load on Wear Rate

Figure 5 depicts the wear behavior of Al–Si/zircon sand

composite and base Al–Si alloy at various applied loads and

constant sliding velocity of 1.6 m s-1. A linear increasing

order behavior of wear rate has been observed with

ascending applied loads following Archard’s law of adhe-

sive wear for metals [25]. The change of wear behavior is

predicted from the change in slope of the wear rate curve as

we progress from 34.3 to 44.1 N for Al–Si alloy. The wear

mechanism alters from mild to severe delaminating mode at

higher loads. However, both at lower and higher load the

curve followed the linear behavior. The horizontally and

vertically sectioned Al–Si/zircon sand composite showed

almost similar behavior under the applied loads. At every

load, the composite material offers greater resistance to

wear than base Al–Si alloy. The most significant difference

in wear rates of the cast alloy and spray formed composites

have been found at higher loads. This resistance to wear is

catered by harder zircon sand particle reinforced in the

softer Al–Si alloy matrix offering more obstacles for the

dislocations to propagate through the matrix.

Fig. 3 Variation of wear rate with sliding distance a Al–Si alloy,

b vertically sectioned, and c horizontally sectioned Al–Si/zircon sand

composite

380 Tribol Lett (2010) 38:377–387

123

One of the important parameters of adhesive wear for

engineering point of view is wear coefficient (K).

According to the adhesive theory, wear coefficient deter-

mines the relative strength of the junction interface to that

of strength of the asperities [26]. K has been calculated

using Archard’s wear law [25]

V ¼ KWS

3H;

where V is the volume loss in mm3, W is applied load in N,

S is sliding distance in m, H is the bulk hardness. The

zircon sand particulates increase the bulk hardness of the

base Al–Si alloy from 76.3 to 83.7 BHN. For both unstable

(run-in) and stable (steady state) wear rates of base alloy

and reinforced composite the value of K is shown in

Table 3. The run-in and steady state wear coefficient of

horizontally and vertically sectioned Al–Si/zircon sand

composite is almost similar. However, Al–Si alloy pos-

sesses much higher wear coefficient value than the com-

posite at every load. Moreover, for all the samples, wear

coefficient of run-in segment is greater than the steady state

Fig. 4 Showing different

cutting sections of spray formed

preform

10 20 30 40 50 60

2.0x10-3

4.0x10-3

6.0x10-3

8.0x10-3

1.0x10-2

1.2x10-2

1.4x10-2

1.6x10-2

1.8x10-2

Wea

r ra

te (

mm

3 /mm

)

Applied load (N)

c b a

Fig. 5 Variation of wear rate with applied load for a Al–Si alloy,

b vertically sectioned, and c horizontally sectioned Al–Si/zircon sand

composite

Table 3 K values of the samples under various loads

Sample Linear segment Wear coefficient (K 9 10-4) under loads Average K 9 10-4

14.7 N 24.5 N 34.3 N 44.1 N 53.9 N

Al–Si alloy Run-in state 0.956 0.667 0.625 0.776 0.888 0.782

Steady state 0.547 0.426 0.385 0.437 0.351 0.429

Vertically sectioned composite Run-in state 0.329 0.317 0.406 0.295 0.290 0.327

Steady state 0.239 0.251 0.246 0.265 0.285 0.257

Horizontally sectioned composite Run-in state 0.286 0.232 0.328 0.423 0.275 0.309

Steady state 0.266 0.209 0.253 0.237 0.251 0.243

10 20 30 40 50 60

0.12

0.16

0.20

0.24

0.28

0.32

0.36

0.40

Fri

ctio

n c

oef

fici

ent

Applied load (N)

a

b

c

Fig. 6 Variation of the friction coefficients with applied load for

a Al–Si alloy, b vertically sectioned, and c horizontally sectioned

Al–Si/zircon sand composite

Tribol Lett (2010) 38:377–387 381

123

wear coefficient. The lower value of K corresponds to the

higher strength of the asperities or greater cohesive

strength of junction in Al–Si/zircon sand composite

materials.

3.2.3 Effect of Load on the Friction Coefficient

The averaged friction coefficient over the entire range of

load is observed to decrease with applied load. The friction

coefficient value for Al–Si alloy and Al–Si/zircon sand

composite lies around 0.3 and 0.25, respectively, as shown

in Fig. 6. The higher value of the friction coefficient at

different loads can be correlated to the lower hardness and

constant asperities contact of the Al–Si alloy.

4 Worn Pin Surfaces and Wear Debris

The micrographs of the worn pin surface of base alloy and

composite at 24.5 and 53.9 N loads have been shown in

Figs. 7a–f, 8a–f, respectively. One of the common features

observed in both lower and higher load, is the formation of

Fig. 7 At 24.5 N load SEM

micrographs of worn pin

surfaces of Al–Si alloy (a, b) at

2509 and 1,0009, respectively;

vertically sectioned Al–Si/

zircon sand composite (c, d) at

1009 and 5009, respectively,

and horizontally sectioned Al–

Si/zircon sand composite (e, f)at 1009 and 1,0009,

respectively

382 Tribol Lett (2010) 38:377–387

123

grooves and ridges running parallel to the sliding direction

in both base alloy and composite. These wear scars are the

primarily characteristic of abrasive wear. On further ana-

lyzing, it has been found that grooves are fine on the worn

pin surface of Al–Si alloy subjected to 24.5 N load

(Fig. 7a) in comparison to 53.9 N load (Fig. 8a). The

amount of repetitive micro-ploughing and material removal

of the soft alloy by hard steel counterpart can be seen in

Fig. 8b, d. Similar observations are also reported earlier in

Al–4.5 Cu–5 Pb system due to cyclic loading [27]. The

depth of micro-ploughing is increased on increasing load to

53.9 N where contact asperities change the shape. Thus,

the size and depth of the grooves become greater at this

stage. Moreover, a high magnification micrograph at

24.5 N load (Fig. 7b) indicates debris formation from the

ridge as the crack propagates perpendicular to the sliding

direction in Al–Si alloy. Such type of microstructural

features gives rise to the formation of metallic wear debris.

The morphological features of spray processed Al–Si/

zircon sand composite shows completely different worn

surfaces than Al–Si alloy. Large elongated dimples can be

seen in the sliding direction on the surface of composite

Fig. 8 At 53.9 N load SEM

micrographs of worn pin

surfaces of Al–Si alloy (a, b) at

1009 and 5009, respectively;

vertically sectioned Al–Si/

zircon sand composite (c, d) at

1009 and 2509, respectively,

and horizontally sectioned Al–

Si/zircon sand composite (e, f)at 1009 and 5009, respectively

Tribol Lett (2010) 38:377–387 383

123

material shown in Figs. 7c, e, 8c, e, respectively. Similar

morphology is indicated by other researchers in ceramic

reinforced AMCs [28, 29]. Moreover, width of grooves and

elongation of dimples predominates as the load is increased

from 24.5 to 53.9 N in Al–Si/zircon sand composite. The

enlarged view of the dimple (Fig. 7d) indicates the for-

mation of non-uniform tribo-layer on the worn surface.

Also, the formed tribo-layer is heterogeneous in nature and

morphology of craters predicts the formation of oxide

debris. At 24.5 N load the smaller size of dimples and fine

grooves can be seen in vertically sectioned composite

(Fig. 7c) in comparison to horizontally sectioned Al–Si/

zircon sand composite (Fig. 7e). At higher load Fig. 8d

shows the four different morphological features; metal flow

lines, micro-ploughing, propagation of cracks at the

periphery of the crater, and detachment of debris. These

cracks exist due to the surface shearing forces and grow

along the periphery of the crater. Moreover, the mechani-

cally welded layer is also being observed on the worn

surfaces due to the transfer of counterpart steel disc

material as well as the compaction of the oxide debris on

the sliding pin which is clearly indicated in Figs. 7f, 8f.

The wear mechanism has been further correlated to the

microstructural analysis of loose debris of base alloy and

composite at 24.5 and 53.9 N load as shown in Figs. 9a–c,

10a–c, respectively.

Figure 9a clearly indicates the wear tracks on the base

alloy debris. The flake type of morphology depicts the

metallic wear in base alloy at 24.5 N load. However, at

similar load both metallic as well as oxide wear debris can

be found in vertically sectioned composite (Fig. 9b). A

large difference has been found in morphology of worn

debris in both vertically and horizontally sectioned com-

posite. Entirely different metallic ribbon type morphology

has been observed in horizontally sectioned composite as

shown in Fig. 9c. These long and ductile ribbons are sup-

posed to be formed due to the predominance of abrasive

wear. The elongated droplets of Al (Fig. 4) get themselves

dragged out from the spray when the welded asperity

comes out. These asperities pultrude the Al which appear

like ribbon.

Under the high load conditions, smaller sized wear

debris are observed in base Al–Si alloy (Fig. 10a) as

compare to vertical sectioned composite Fig. 10b. It can be

further related to the greater resistance to the seizure and

different wear mechanism offered by composite material as

compare to base Al–Si alloy. The material is removed in

the form of debris from rubbing surfaces during micro-

Fig. 9 SEM micrographs of

wear debris of a Al–Si alloy,

b vertically sectioned, and

c horizontally sectioned Al–Si/

zircon sand composite at 1009,

respectively, at 24.5 N load

384 Tribol Lett (2010) 38:377–387

123

ploughing. In vertically sectioned composite most of the

material gets displaced on the sides of grooves due to

plastic deformation. However, in horizontally sectioned

composite the material is removed by an abrasive wear

mechanism due to micro cutting or peel-off [26] of the

material resulting high aspect ratio of wear debris in the

form of ductile ribbons. Moreover, in horizontally sec-

tioned composite a lower load favors the generation of finer

ribbons (Fig. 9c) as in comparison to higher loads

(Fig. 10c). The reinforced composite illustrates coagulated

and round features of small oxide wear debris under both

lower and higher load conditions.

The wear scars of reinforced alloy in Figs. 7, 8 corre-

sponds to head and tail morphology of dimples along the

sliding direction. The various stages illustrating the

development of this type of morphology are shown in

Fig. 11a–f. Figure 11a shows the various forces acting on

the test pin surface, where W represents the applied load, N

is the normal force to applied load acting on the counter-

part, F is the traction force acting due to sliding, and F0 is

the frictional force developed against sliding. On initial

sliding aluminum matrix being softer has been removed

from the composite as illustrated in Fig. 11b. On further

sliding the stress has been carried out by the particle only

due to which the crack start propagating at the interface of

zircon sand particle and matrix. This situation leads to

development of the head of the dimple depicted in

Fig. 11c. The increase in the stress distribution promotes

crack initiation on the matrix as well as particle (Fig. 11-

d).The cracking of zircon sand particle abrades matrix

around the particle in the sliding direction creating tail of

the dimple as shown in Fig. 11e. The further sliding leads

to the formation of smaller zircon sand particles causing

lengthening tail in the matrix which is shown as a tail

growth in Fig. 11f.

The EDS analysis (Fig. 12) of loose zircon sand particle

from the vertically sectioned composite indicates the

presence of Fe on its surface indicating material transfer

from disc. The chemical composition of dimple morphol-

ogy on the worn surface of the reinforced composite shows

an oxidative wear mechanism indicated by the presence of

Al, O, Si, Zr, and Fe as given by EDS result in Fig. 13. On

analyzing microstructural features and EDS of worn sur-

faces and debris of Al–Si/zircon sand composite it has been

found that there is formation of wear protective oxide layer

on the load bearing surfaces. The oxide layer poses a

greater resistance to the sliding wear and friction as oxide

debris reduces the extent of direct metal to metal contact.

Fig. 10 SEM micrographs of

wear debris of a Al–Si alloy,

b vertically sectioned, and

c horizontally sectioned Al–Si/

zircon sand composite at 1009,

respectively, at 53.9 N load

Tribol Lett (2010) 38:377–387 385

123

The formation of chemically reacted oxide layer is resulted

from the oxidation of the exposed metal surface in the

relative motion. The rupture of the oxide layer during

transversal and reoxidation of exposed metal surface is

called oxidation–delamination–reoxidation [30]. Moreover,

the compaction and comminution of the debris between the

sliding surfaces favored the development of wear protec-

tive oxide layer [31].

5 Conclusions

The zircon sand reinforced Al–Si alloy is successfully

prepared with spray deposition technique. The wear char-

acteristics of both reinforced and unreinforced alloy have

led to the following conclusions:

1. The results confirmed that spray formed Al–Si/zircon

sand composite is clearly superior to base Al–Si alloy

in delaying the transition to severe wear at higher loads

as well as showing greater resistance to wear at lower

loads also.

2. The value of the friction coefficients for Al–Si/zircon

sand composite is lesser (0.25) than that of Al–Si (0.3)

at various applied loads.

3. The wear rate and volume loss showed the two stages

of wear for all the applied loads. At the initial stage

run-in wear occur up to 1 km sliding distance and in

later stage wear approaches a steady state.

4. The three different types of wear mechanisms have

acted in both reinforced and unreinforced alloy, i.e.,

adhesive, oxidative, and abrasive. The adhesive cum

oxidative wear mechanisms have been found in both

reinforced and unreinforced alloy. The basic wear

mechanism is the adhesive wear illustrated by the

presence of grooves and transfer of material from disc

to load bearing surfaces. The oxidative wear is more

predominant in reinforced composite, which is

revealed by morphology and EDS analysis of worn

surfaces and debris. The oxidative mechanism is the

most effective in reducing the wear rate and friction in

Al–Si/zircon sand composite. The other mechanism is

the abrasive wear which dominates in horizontally

sectioned Al–Si/zircon sand composite as depicted

from the ribbon morphology of debris.

Fig. 11 Schematic diagram

indicating wear mechanism at

various stages during the wear

test

Fig. 12 EDS of wear debris in vertically sectioned Al–Si/zircon sand

composite

Fig. 13 EDS of worn surface of the pin of Al–Si/zircon sand

composite

386 Tribol Lett (2010) 38:377–387

123

Acknowledgments The authors are thankful to Council of Scien-

tific and Industrial Research (CSIR), India funded scheme number

22(0403)/06/EMR-II for providing financial support for this study.

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