A comaprative study for selection of effective electrolyte solution for electrochemical discharge machining

1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 6, Issue 1, January (2015), pp. 98-103© IAEME
98
A COMPARATIVE STUDY FOR SELECTION OF
EFFECTIVE ELECTROLYTE SOLUTION FOR
ELECTROCHEMICAL DISCHARGE MACHINING
M.L.Harugade1
, N.V.Hargude2
, A P Shrotri3
, S.P.Shinde4
1
Assistant Prof. Dept. of Mechanical Engg, PVPIT, Budhgaon 416304, M.S.India
2
Associate Prof. Dept. of Mechanical Engg, PVPIT, Budhgaon 416304, M.S.India
3
Associate Prof. Dept. of Mechanical Engg, PVPIT, Budhgaon 416304, M.S.India
4
Assistant Prof. Dept. of Mechanical Engg, PVPIT, Budhgaon 416304, M.S.India
ABSTRACT
Electrochemical discharge machining ECDM is an advanced hybrid machining process
which can be successfully used for machining electrically non-conductive materials such as glass
ceramics and composites materials which are now a day’s used extensively for engineering
applications. It is combination of ECM and EDM. The performance of the process is highly non-
linear and complex depends upon number of parameters associated with physical and chemical
partners of the process. However the performance largely depends on type and concentration of
electrolyte solution used. The electrolyte also governs the wear of electrode and MRR of the process.
This paper highlights on such facts associated with the electrolyte used and its impact on the process
of ECDM.
Keywords: ECDM, Electrolyte Solution, Sparking, Spark Colour
1. INTRODUCTION
The electrochemical discharge machining (ECDM) process is a thermal–chemical machining
system; ECDM is advanced hybrid machining process combination of electrochemical machining
(ECM) and electro discharge machining (EDM).It can be successfully used for machining
electrically non-conductive advanced engineering materials such as glass, composite and ceramics
materials. The performance of ECDM, in terms of material removal rate, tool wear rate and radial
over cut, is affected by many factors such as electrolyte solution, electrolyte concentration and inter-
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2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 6, Issue 1, January (2015), pp. 98-103© IAEME
99
electrode gap. Relationships between these factors and machining performance are highly non-linear
and complex in nature. But by many research works it has been found that electrolyte
2. PRINCIPLE OF ECDM
Fig 2.1: Principle of ECDM process
The electrochemical discharge phenomenon is clearly demonstrated by the above simple
figure. Two electrodes are dipped inside an aqueous electrolyte. The cathode is chosen with a much
smaller surface than the anode. When the D.C. voltage is applied electrolysis happens and Hydrogen
gas bubbles are formed at the tool-electrode (cathode) and oxygen bubbles at the counter electrode
(anode). When the voltage is increased, the current density increases too and more and more bubbles
grow forming a bubble layer around the electrodes. When the voltage is increased above the critical
voltage, bubbles coalesce into a gas film around the tool-electrode. Sparking phenomena is observed
in the film where electrical discharges happen between the tool-electrode and the surrounding
electrolyte. Similar behavior can be obtained by inverting the polarity of the electrodes and by
changing the electrolytes. Fig 2.1 explains the ECDM phenomenon [5] [8][9].

3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976
ISSN 0976 – 6359(Online), Volume 6, Issue 1, January (2015), pp.
3. COMPARATIVE STUDY BETWEEN
MACHINING PARAMETERS
Table 3.1: Comparative study between electrolyte solutions and machining parameters
Sr. No. Existing machining parameters
1.
1. W/p. material -
2.Electrolyte solution
2.
1.W/p. material –Zirconium oxide
2. Electrolyte solution
3.
1. W/p. material – Silicate nitrate
ceramic(Si3N4)
2. Electrolyte solution
4.
1. W/p. material - G
2. Electrolyte solution
3.1Classification of electrolyte [13
Many researchers show that KOH and NaOH are suitable for constant sparking, KOH and
NaOH has strong base. Also some researchers used H
acid. NaCl and NaNO3 are salts of strong acid strong
For ECDM, electrolyte solution may acid, salt or base but it should be strong. Because for
maximum sparking and bubble formation electrolyte should be
in the case of strong solutions.
Acid
Strong
Ex. H2SO4
Weak Strong
Ex. NaOH
KOH
ournal of Mechanical Engineering and Technology (IJMET), ISSN 0976
6359(Online), Volume 6, Issue 1, January (2015), pp. 98-103© IAEME
100
COMPARATIVE STUDY BETWEEN VARIOUS ELECTROLYTE SOLUTIONS AND
MACHINING PARAMETERS
Comparative study between electrolyte solutions and machining parameters
[12]
machining parameters for various electrolyte solution
Soda lime glass
2.Electrolyte solution – H2SO4
Voltage- 60V
Conc.- 30%
Inter-electrode gap
Zirconium oxide
2. Electrolyte solution - KOH
Voltage - 50V
Conc.- 25%
Inter-electrode gap
Silicate nitrate
Electrolyte solution - NaOH
Voltage - 70V
Conc.- 18%
Inter-electrode gap
Glass-epoxy composites
Electrolyte solution - NaCl
Voltage- 75V
Conc.- 20%
Inter-electrode gap
[13]
that KOH and NaOH are suitable for constant sparking, KOH and
NaOH has strong base. Also some researchers used H2SO4, NaCl, NaNO3, in this
are salts of strong acid strong base.
For ECDM, electrolyte solution may acid, salt or base but it should be strong. Because for
maximum sparking and bubble formation electrolyte should be a good electric conductor
Electrolyte
Base
Strong
Ex. NaOH
KOH
Weak
Salt
Strong
Acid &
Strong
Base
Ex. NaCl
NaNO3
Strong
Acid &
Weak
Base
ournal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
© IAEME
ELECTROLYTE SOLUTIONS AND
Comparative study between electrolyte solutions and machining parameters [4] [10] [11]
for various electrolyte solution
- 10mm
- 20mm
- 27mm
- 50mm
that KOH and NaOH are suitable for constant sparking, KOH and
, in this H2SO4 is strong
For ECDM, electrolyte solution may acid, salt or base but it should be strong. Because for
good electric conductor, which is as
Weak
Acid &
Strong
Base
Weak
Acid &
Weak
Base

4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 6, Issue 1, January (2015), pp. 98-103© IAEME
101
3.2 Properties of electrolyte
Table 3.2: Properties of electrolyte [13]
4. EFFECT OF ELECTROLYTE SOLUTION ON WORK-PIECE MATERIAL
4.1 Effect of electrolyte concentration on material removal rate
Previous authors have proposed effect of electrolyte concentration over material removal rate
by finite element method. It was observed that with increase in electrolyte concentration from 10%
to 30%, material removal rate increased significantly especially in soda lime glass and thereafter the
concentration does not play any role to enhance the MRR. This can be explained from the fact that as
the concentration is increased, the critical voltage and critical current increases. An increase in
electrolyte current would mean the accelerated electrolysis process. It would result in greater rate of
hydrogen bubbles at the cathode tool. The increased rate of hydrogen bubbles at the cathode implies
an enhanced rate of sparking and hence higher MRR. [1] [4] [5]
The surface texture obtained is dependent on the concentration of the electrolyte used, i.e., its
viscosity. For high electrolyte concentrations, however, cracks may form on the machining surface.
[2]
4.2 Effect of electrolyte temperature on material removal rate
When electrolyte temperature increases electrolyte conductivity increases too, thus increasing
the amount of current which accelerates the electrolysis process, resulting in a greater rate of
evolution of hydrogen gas bubbles at the cathode. The increased rate of formation of gas bubbles at
the cathode leads to an enhanced rate of sparking, hence higher material removal. So it can be said
that material removal increases with the increased conductivity. [6] [7]
5. RELATIONSHIP BETWEEN COLOUR OF THE SPARK AND ELECTROLYTE
SOLUTION
In this research it is seen that electrolyte solution has effect on colour of the spark. Colour of
the spark changes with electrolyte solution it can be seen from photos below that colour of spark
can change according to electrolyte solution used.
Molecular
formula
Molar
mass
g/mol
Appearance
Odour Density
g/cm
Melting
point
O
C
Boiling
point
O
C
Solubility
KOH
56.1056
g/mol White solid Odourless
2.044
g/cm 406 °C 1327 °C
121 g/100
ml
(at 25 °C)
NaOH
39.9971
g mol-1
Opaque
crystals, White Odourless
2.13
g/cm3
318 °C 1388 °C
111 g/100
ml
(at 20 °C)
NaCl
58.44
g mol−1
Colorless
crystals
Odourless
2.165
g cm−3 801 °C 1413 °C 359 g l−1
NaNO3
84.9947
g/mol
Colorless
crystals Sweet
2.257
g/cm3
,
solid
308 °C 380 °C
91.2 g/100
ml
(at 25 °C)
H2SO4
98.079
g/mol
Clear,
colorless
Odourless
1.84
g/cm3
,
liquid
10 °C 337 °C miscible

5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976
ISSN 0976 – 6359(Online), Volume 6, Issue 1, January (2015), pp.
Electrolyte Solution KOH
First photo bright yellow spark stable and constant, in this process KOH is used as electrolyte
solution. In second photo NaCl is used as electrolyte in which melting of auxiliary electrode can be
seen, in this process tool electrode wear rate is more.
Third photo H2SO4 electrolyte solution is used in which it shows that the colour of spark is
blue. In this process sparking fluctuate continuously which increases chances of glass break by 30%.
6. CONCLUSION
Electrochemical discharge machining ECDM
which can be successfully used for machining electrically non
performance of the process is highly non
associated with physical and chemical partners of the process. It is by and large governed by the
electrolyte solution used and its concentration. The comparative study
indicate the fact that the nature and colour of spark
electrolyte used and it also shows variation in the process output. The acidic electrolyte solution
shows intermittent and disturbed spark which result in excessive erosion of electrode and damage to
the work-piece. The salty electrolyte solution shows remarkable wear of tool however no damage to
work-piece is recorded. The basic electrolyte solution shows negligible
better surface finish of work-piece.
With these observation it can concluded
performance of ECDM process.
7. REFERENCES
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ournal of Mechanical Engineering and Technology (IJMET), ISSN 0976
6359(Online), Volume 6, Issue 1, January (2015), pp. 98-103© IAEME
102
Electrolyte Solution NaCl Electrolyte Solution H
First photo bright yellow spark stable and constant, in this process KOH is used as electrolyte
solution. In second photo NaCl is used as electrolyte in which melting of auxiliary electrode can be
lectrode wear rate is more.
electrolyte solution is used in which it shows that the colour of spark is
this process sparking fluctuate continuously which increases chances of glass break by 30%.
Electrochemical discharge machining ECDM is an advanced hybrid machining process
which can be successfully used for machining electrically non-conductive materials
performance of the process is highly non-linear and complex depends upon number of para
associated with physical and chemical partners of the process. It is by and large governed by the
electrolyte solution used and its concentration. The comparative study highlighted in this paper
indicate the fact that the nature and colour of spark largely depends on type and concentration of
electrolyte used and it also shows variation in the process output. The acidic electrolyte solution
shows intermittent and disturbed spark which result in excessive erosion of electrode and damage to
ece. The salty electrolyte solution shows remarkable wear of tool however no damage to
piece is recorded. The basic electrolyte solution shows negligible wear,
piece.
With these observation it can concluded that use of basic electrolyte solution. Leads to
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International Journal of Machine Tools & Manufacture,vol.50 (2010), pp 689
ournal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
© IAEME
Electrolyte Solution H2SO4
First photo bright yellow spark stable and constant, in this process KOH is used as electrolyte
solution. In second photo NaCl is used as electrolyte in which melting of auxiliary electrode can be
electrolyte solution is used in which it shows that the colour of spark is
this process sparking fluctuate continuously which increases chances of glass break by 30%.
advanced hybrid machining process
conductive materials. The
linear and complex depends upon number of parameters
associated with physical and chemical partners of the process. It is by and large governed by the
highlighted in this paper
largely depends on type and concentration of
electrolyte used and it also shows variation in the process output. The acidic electrolyte solution
shows intermittent and disturbed spark which result in excessive erosion of electrode and damage to
ece. The salty electrolyte solution shows remarkable wear of tool however no damage to
wear, constant spark and
use of basic electrolyte solution. Leads to better
“Finite element prediction of material removal
International Journal of Machine Tools &
texturing channel surfaces
al Journal of Machine Tools &
KuangYang c, Yu-Shan
“Study of gas film quality in electrochemical discharge machining”
International Journal of Machine Tools & Manufacture,vol.50 (2010), pp 689–697.

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ISSN 0976 – 6359(Online), Volume 6, Issue 1, January (2015), pp. 98-103© IAEME
103
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