The document describes a study investigating the effect of chilling on the soundness, microhardness, and ultimate tensile strength of nickel alloy-fused silica metal matrix composites. Nickel alloy composites containing 3-12% fused silica particles were fabricated using an induction furnace. The composites were cast in molds containing different chill materials. Results showed that strength and soundness depended on chill thickness/material and dispersoid content. Composites cast with thicker chills and 9% silica exhibited the highest hardness and tensile strength. Microstructural analysis revealed uniformly distributed silica and a fine grain structure in chilled composites.

1. International Journal of Civil, Mechanical and Energy Science (IJCMES) [Vol-2, Issue-1, Jan-Feb, 2016]
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Effect of Chilling on Soundness, Micro Hardness
and Ultimate Tensile Strength of Nickel Alloy-
Fused Silica Metal Matrix Composite
G. Purushotham1
, Joel Hemanth2
1
Department of Aeronautical Engineering, Mangalore Institute of Technology & Engineering, Moodbidri, Karnataka, INDIA
2
Department of Mechanical Engineering, HMS Institute of Technology, Tumkur, Karnataka, INDIA
Abstract—An investigation has been carried out to
fabricate and evaluate the strength and soundness of chilled
composites consisting of nickel matrix and fused silica
particles (size 40–150 μm) in the matrix. The dispersoid
added ranged from 3 to 12 wt. % in steps of 3%. The
resulting composites cast in moulds containing metallic and
non metallic chill blocks (MS, SiC& Cu) were tested for
their microstructure, hardness and tensile strength
properties. The main objective of the present research is to
obtain fine grain Ni/SiO2 chilled sound composite having
very good properties. Results of the investigation reveal the
following: (1) Strength of the composite developed is highly
dependent on the location of the casting from where the test
specimens are taken and also on the dispersoid content of
the composite. (2) Chill thickness and chill material,
however, does significantly affect the strength and
soundness of the composite. (3) Soundness of the composite
developed is highly dependent on the chilling rate as well as
the dispersoid content.
Keywords—Chills, Fused silica, Metal matrix composite,
Hardness and Tensile strength,Nickel alloy.
I. INTRODUCTION
Nickel alloy based metal matrix composites are the class of
advanced materials that are well suited for pumps, valves
and automotive industries because of their strength,
corrosion resistance and for electric and electronic industry
because of their high thermal and electrical
conductivities[1-2]. The demand for such functional
material to provide high performance has resulted in
continuous attempts being made particularly in areas of
alloy design and the use of novel processing techniques to
develop composites or hybrid materials as serious
competitors to the traditional engineering alloys. In
particular, the particle-reinforced metal matrix composites
(MMCs) are attractive in that they exhibit near-isotropic
properties by comparison with the continuously-reinforced
matrices [3-6]. Others reported the advantages of this alloy
have to offer over the other material include a potential for
high hardness and abrasion resistance, improved fracture
crack propagation and good micro creep performance.
Furthermore, fabrication of the discontinuously-reinforced
nickel composites can be achieved by standard
metallurgical processing methods and these materials can be
machined by using conventional facilities. The combination
of properties offered by particle-reinforced nickel metal-
matrix composites makes these materials attractive for
applications in the aerospace, defense and plumbing
industries [7-10]. In the past years, only studies have been
conducted to understand and document the metallurgical
and mechanical properties of nickel and nickel alloys.
It is well known that Ni alloys that freeze over a wide range
of temperature are difficult to feed during solidification.
The dispersed porosity caused by the pasty mode of
solidification can be effectively reduced by the use of chills.
Chills extract heat at a faster rate and promote directional
solidification. Therefore, chills are widely used by foundry
engineers for the production of sound and quality castings
[11-14].With the increase in the demand for quality
composites, it has become essential to produce nickel alloy
composites that are free from solidification defects. Nickel
alloy castings widely used in automobiles and industries are
prone to unsoundness in the form of micro-shrinkage.
II. EXPERIMENT DETAILS
2.1 MATERIAL SELECTION:
The metal matrix material was selected available pure
nickel base alloy (Monel metal). The chemical composition
of the matrix is given in the table 1. The reinforcement was
pure SiO2 of particles size 40μm to 150μm. Induction
method was used for preparation of the composite.

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Table 1:Composition of Nickel alloy. (M
III. PREPARATION OF THE COMPOSITE
The nickel base alloy / fused SiO2 metal matrix composite
were fabricated by using induction furnace attached with a
stirrer by varying percentage of reinforcement particles
from 3 wt% to 12 wt% in steps of 3%. This method is the
most economical to fabricate composites materials. The
matrix was first superheated above its melting temperature
(1560 0
C) and preheated SiO2 (500 0
C) particulates added
into molten metal. The molten metal was stirred properly.
The melt at 1560°C was poured into the sand moulds where
chills are introduced. The moulds for the plate type of
castings 225*50*25 mm were prepared
with 5% bentonite as binder and 5% moisture and finally
they were dried in an air furnace at a temperature of 1560
0
C, which was cooled from one end by different metallic
and non metallic chill block set in the mould
furnace are as shown in fig 1 and 2 respectively.
Fig 1. Chills arrangement
1) SiCchill 2) Cu chill 3) MS chill 4) Without chill
Element Ni Cu Fe C Mn
Composi
tion in
wt%
Bala
nce
26.6
0.51
3
0.196 3.02
Element S Cr Co Al Ti
Composi
tion in
wt%
0.00
27
0.02
52
0.08
26
0.112 0.121
1 2
3 4
International Journal of Civil, Mechanical and Energy Science (IJCMES) [Vol
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Nickel alloy. (M-35-1)
PREPARATION OF THE COMPOSITE
metal matrix composite
were fabricated by using induction furnace attached with a
stirrer by varying percentage of reinforcement particles
from 3 wt% to 12 wt% in steps of 3%. This method is the
most economical to fabricate composites materials. The
x was first superheated above its melting temperature
C) particulates added
into molten metal. The molten metal was stirred properly.
The melt at 1560°C was poured into the sand moulds where
lds for the plate type of
castings 225*50*25 mm were preparedusing silica sand
with 5% bentonite as binder and 5% moisture and finally
they were dried in an air furnace at a temperature of 1560
C, which was cooled from one end by different metallic
n metallic chill block set in the mould and induction
furnace are as shown in fig 1 and 2 respectively.
Chills arrangement
4) Without chill
Fig 2. Induction furnace
IV. TESTING OF
4.1 TENSILE STRENGTH TEST:
Fig 3.UTM-40T and specimen
Specimens for tensile testing were selected to understand
the effect of ultimate tensile strength on the matrix
composites. The specimen dimensions were as
E8-M04 round standards as shown in Fig.3
were machined using CNC lathe machines. Tension tests
were performed to determine the ultimate tensile strength
(UTS) using Computerized UTM shown in Fig.3
Si P
3.02 0.8
0.023
2
Sn Pb
0.121
0.023
7
0.075
3
(IJCMES) [Vol-2, Issue-1, Jan-Feb, 2016]
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Induction furnace
TESTING OF COMPOSITES
TENSILE STRENGTH TEST:
40T and specimen for tensile test as per ASTM
Specimens for tensile testing were selected to understand
the effect of ultimate tensile strength on the matrix
composites. The specimen dimensions were as per ASTM
ound standards as shown in Fig.3.The specimens
CNC lathe machines. Tension tests
were performed to determine the ultimate tensile strength
Computerized UTM shown in Fig.3.

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Table 1:Composition of Nickel alloy. (M
III. PREPARATION OF THE COMPOSITE
The nickel base alloy / fused SiO2 metal matrix composite
were fabricated by using induction furnace attached with a
stirrer by varying percentage of reinforcement particles
from 3 wt% to 12 wt% in steps of 3%. This method is the
most economical to fabricate composites materials. The
matrix was first superheated above its melting temperature
(1560 0
C) and preheated SiO2 (500 0
C) particulates added
into molten metal. The molten metal was stirred properly.
The melt at 1560°C was poured into the sand moulds where
chills are introduced. The moulds for the plate type of
castings 225*50*25 mm were prepared
with 5% bentonite as binder and 5% moisture and finally
they were dried in an air furnace at a temperature of 1560
0
C, which was cooled from one end by different metallic
and non metallic chill block set in the mould
furnace are as shown in fig 1 and 2 respectively.
Fig 1. Chills arrangement
1) SiCchill 2) Cu chill 3) MS chill 4) Without chill
Element Ni Cu Fe C Mn
Composi
tion in
wt%
Bala
nce
26.6
0.51
3
0.196 3.02
Element S Cr Co Al Ti
Composi
tion in
wt%
0.00
27
0.02
52
0.08
26
0.112 0.121
1 2
3 4
International Journal of Civil, Mechanical and Energy Science (IJCMES) [Vol
Infogainpublication.com)
Nickel alloy. (M-35-1)
PREPARATION OF THE COMPOSITE
metal matrix composite
were fabricated by using induction furnace attached with a
stirrer by varying percentage of reinforcement particles
from 3 wt% to 12 wt% in steps of 3%. This method is the
most economical to fabricate composites materials. The
x was first superheated above its melting temperature
C) particulates added
into molten metal. The molten metal was stirred properly.
The melt at 1560°C was poured into the sand moulds where
lds for the plate type of
castings 225*50*25 mm were preparedusing silica sand
with 5% bentonite as binder and 5% moisture and finally
they were dried in an air furnace at a temperature of 1560
C, which was cooled from one end by different metallic
n metallic chill block set in the mould and induction
furnace are as shown in fig 1 and 2 respectively.
Chills arrangement
4) Without chill
Fig 2. Induction furnace
IV. TESTING OF
4.1 TENSILE STRENGTH TEST:
Fig 3.UTM-40T and specimen
Specimens for tensile testing were selected to understand
the effect of ultimate tensile strength on the matrix
composites. The specimen dimensions were as
E8-M04 round standards as shown in Fig.3
were machined using CNC lathe machines. Tension tests
were performed to determine the ultimate tensile strength
(UTS) using Computerized UTM shown in Fig.3
Si P
3.02 0.8
0.023
2
Sn Pb
0.121
0.023
7
0.075
3
(IJCMES) [Vol-2, Issue-1, Jan-Feb, 2016]
) ISSN : 2455-5304
Page | 30
Induction furnace
TESTING OF COMPOSITES
TENSILE STRENGTH TEST:
40T and specimen for tensile test as per ASTM
Specimens for tensile testing were selected to understand
the effect of ultimate tensile strength on the matrix
composites. The specimen dimensions were as per ASTM
ound standards as shown in Fig.3.The specimens
CNC lathe machines. Tension tests
were performed to determine the ultimate tensile strength
Computerized UTM shown in Fig.3.

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9% SiO2 plain
3% SiO2 SiC chill
6% SiO2 SiC chill
9% SiO2. SiC chill
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3% SiO
6% SiO
9% SiO
6% SiO
Fig 6. Microstructural studies of base metal, different
weight % of SiO2 and different chills.
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3% SiO2 MS Chill
6% SiO2 MS Chill
9% SiO2 MS Chill
6% SiO2 Cu Chill
Fig 6. Microstructural studies of base metal, different
weight % of SiO2 and different chills.

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Discussion:
It is observed from the microstructural studies that (fig
6),dispersoid is distributed uniformly and this is mainly
because of stirring and density difference. Bonding is
perfect between matrix and dispersoid due to preheating of
the dispersoid and no mismatch between them is observed.
Micro porosity is also not observed in the microstructure.
The microstructure reveals fine grain structure because of
chilling.
5.2 CHEMICAL COMPOSITION BY EDX TEST:
BASE METAL:
3% SiO2:
6% SiO2:
9% SiO2:
Fig 7. Photographs of chemical composition of base metal
and different wt. % of SiO2
Elem
ent
Weig
ht%
Si K 0.83
P K 0.73
S K 0.29
Mn
K
2.03
Fe K 2.04
Ni K 62.17
Cu K 30.79
Nb L 1.13
Total
s
100.0
0
Elem
ent
Weig
ht%
Si K 2.39
P K 0.20
S K 0.18
Mn
K
2.20
Fe K 1.78
Ni K 67.60
Cu K 25.66
Nb L -0.01
Total
s
100.0
0
Elem
ent
Weig
ht%
Si K 5.63
P K -0.02
S K 0.00
Mn
K
2.90
Fe K 2.14
Ni K 62.07
Cu K 26.32
Nb L -0.04
Total
s
100.0
0
Elem
ent
Weig
ht%
Si K 8.21
P K 0.20
S K 0.07
Mn K 3.40
Fe K 2.30
Ni K 60.17
Cu K 25.71
Nb L -0.06
Total
s
100.0
0

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5.3 MICRO HARDNESS TEST:
Fig.8. Vickers hardness values of Nickel based composites
with different SiO2 percentages cast under the influence of
different chills.
DISCUSSION:
Figure 8depicts, the hardness qualities demonstrate the
pattern that as the rate of expansion of SiO2 is increased
from 3 wt. % to 9 wt. % there is an increase in the
composite's hardness. Later there is a decrease in the
hardness when SiO2 substance is extended to 12 wt. %.
The hardness estimations of composites cast with
distinctive chills have increases with the expanded
extension of SiO2. The most extreme hardness was gotten
for composite cast with 9 wt. % SiO2. There has been
significant gain in hardness values when compared with
the framework mixture. There has been a significant
increase of 47% in hardness.
5.4 TENSILE STRENGTH (N/mm2
):
Fig.9. Tensile strength values of Nickel based composites
with different SiO2 percentages cast under the influence of
different chills.
DISCUSSION:
From the present results, it is cleared that the dispersoid
content is increases, tensile strength is also increases up to
9% addition of reinforcement, since fused SiO2 is a hard
ceramic embedded in nickel matrix. After addition of
further reinforcement the tensile strength gradually
decreases from 9% to 12% addition i.e. an increase 3% of
SiO2. Tensile strength also increases as VHC of the chill
increases from non metallic to metallic chill. This increase
in tensile strength property is mainly because of fine grain
structure obtained due to chilling.
VI. CONCLUSIONS
1. Nickel based metal matrix composite can be produced
successfully from a conventional electric induction furnace.
2. Different chill material and the dispersoid content
however do significantly affect the mechanical properties of
the composites.
3. Microstructure of the chilled composites is finer than that
of un-chilled matrix alloy with uniform distribution of SiO2
particles. Strong interfacial bond was observed with no
agglomeration between the matrix and the dispersoid.
4. Strength and hardness of the chilled MMC are superior to
those of the unchilled matrix alloy. It was found that these
properties increase with an increase in the dispersoid
content up to 9wt% and then gradually decreasing the
properties.
5. It is clearly indicated that the dispersoid is uniformly
distributed in the matrix alloy by EDX test.
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