Revised_Paridhi_Thesis_Fullmerged.pdf

INVESTIGATION FOR THE IMPROVEMENT OF
PERFORMANCE BY EDM PROCESS USING
MULTI HOLED ELECRODE AND POWDER MIXED
DIELECTRIC
Thesis Submitted for the Award of the Degree of
DOCTOR OF PHILOSOPHY
in
Mechanical Engineering
By
PARIDHI MALHOTRA
(Registration no.: A2366616001)
Under the Supervision of
Dr. R.K Tyagi
Professor, Department of Mechanical Engineering,
A.S.E.T., Amity University Uttar Pradesh, Noida
and
Co-Supervision of
Dr. Basant Singh Sikarwar
Professor, Department of Mechanical
Engineering,
A.S.E.T., Amity University Uttar
Pradesh, Noida
Dr. Andriya Narasimhulu
Assistant Professor, Manufacturing
Processes and Automation
Engineering Department, Netaji
Subhas University of Technology, New
Delhi
Amity University Uttar Pradesh, Noida
(INDIA) 2021

Dedicated to my beloved parents, dear husband
& little son

iii
UNDERTAKING FROM THE PhD SCHOLAR
I hereby declare that I, PARIDHI MALHOTRA, have completed the
Ph. D. thesis work on the title “INVESTIGATION FOR THE
IMPROVEMENT OF PERFORMANCE BY EDM PROCESS USING
MULTI HOLED ELECRODE AND POWDER MIXED DIELECTRIC”
under the supervision of Dr. R.K Tyagi, Dr. Basant Singh
Sikarwar and Dr. Andriya Narasimhulu for the degree of Doctor
of Philosophy, Amity University Uttar Pradesh.
This is my own work and I have not submitted it earlier elsewhere.
Date: , August, 2021 PARIDHI MALHOTRA
Place: Noida A2366616001

iv
DECLARATION CERTIFICATE
I, PARIDHI MALHOTRA, D/o Mr. SUNIL MALHOTRA and Mrs.
ANITA MALHOTRA certify that the work embodied in this Ph.D.
thesis is my own bonafide work carried out by me under the
supervision of Dr. R.K Tyagi, Dr. Basant Singh Sikarwar and
Dr. Andriya Narasimhulu for a period of January 2016 to August
2021 at Amity University Uttar Pradesh. The work embodied in this
Ph.D. thesis has not been submitted for the award of any other
degree/ diploma except where due acknowledgement has been made
in the text.
I, hereby declare that I have faithfully acknowledged, given credit to
and refereed to the research workers wherever their works have
been cited in the text and the body of thesis. I further certify that I
have not willfully lifted up some other’s work, para, text, data, results,
etc. reported in the journals, books, magazines, reports,
dissertations, thesis, etc. or available at websites and included them
in this Ph.D. thesis and cited as my own work.

v
AMITY UNIVERSITY UTTAR PRADESH
AMITY SCHOOL OF ENGINEERING AND TECHNOLOGY
Dr. R.K Tyagi
B.Tech.; M.Tech. [HBTI, Kanpur] and
Ph.D. [BIT, Mesra, Ranchi]
Professor
Department of Mechanical Engineering
Amity School of Engineering and Technology
Amity University Uttar Pradesh
Noida-201313 (INDIA)
CERTIFICATE FROM THE GUIDE
Date: , August, 2021
This is to certify that research work embodied in this thesis entitled
“INVESTIGATION FOR THE IMPROVEMENT OF PERFORMANCE
BY EDM PROCESS USING MULTI HOLED ELECRODE AND
POWDER MIXED DIELECTRIC” submitted to Amity University Uttar
Pradesh, for the award of the degree of Doctor of Philosophy
(MAE) has been carried out by Paridhi Malhotra under my
supervision at ASET, Noida, AUUP from January 2016 to August
2021.
To the best of my knowledge and belief, this work is original and has
not been submitted so far in part or in full for the award of any
degree or diploma of any University/Institute.
(Dr. R.K Tyagi)
Amity University Campus, Sector-125, Noida-201313, Gautam Buddha Nagar, U. P. (INDIA)
Tel.: +91-8860490258
E-mail id: rktyagi@amity.edu; Website: http://amity.edu/aset/departments-mae.asp

vi
CERTIFICATE FROM THE CO-GUIDE
Netaji Subhas University of Technology
Formerly Netaji Subhas Institute of technology
Govt. of NCT of Delhi
Date: , August, 2021
This is to certify that research work embodied in this thesis entitled
“INVESTIGATION FOR THE IMPROVEMENT OF PERFORMANCE
BY EDM PROCESS USING MULTI HOLED ELECTRODE AND
POWDER MIXED DIELECTRIC” submitted to Amity University Uttar
Pradesh, for the award of the degree of Doctor of Philosophy
(Mechanical Engineering) has been carried out by Ms. Paridhi
Malhotra under my co-supervision at <ASET> AUUP, from January
2016 to August 2021.
To the best of my knowledge and belief, this work is original and has
not been submitted so far in part or in full for the award of any
degree or diploma of any University/Institute.
Dr. Andriya Narasimhulu
Assistant Professor
Manufacturing Process and Engineering Department
Netaji Subhas University of Technology, New Delhi (INDIA)

vii
COURSE WORK AND COMPREHENSIVE EXAMINATION
COMPLETION CERTIFICATE
This is to certify that Paridhi Malhotra, Enrolment No A2366616001,
a bonafide Ph. D. Scholar of A.S.E.T., Noida has successfully
completed the course work and comprehensive examination, which
is part of her Ph.D. programme.
Date: , August, 2021 Date: , August, 2021
Prof. (Dr.) M.K. Pandey Prof. (Dr.) Abhay Bansal
Joint Head, A.S.E.T. Joint Head, A.S.E.T.
Amity University Uttar Pradesh, Amity University Uttar Pradesh,
Noida Noida

viii
PRE-SUBMISSION SEMINAR COMPLETION
CERTIFICATE
This is to certify that Ms. Paridhi Malhotra, Enrolment No.
A2366616001, Ph. D. Scholar of A.S.E.T., Noida has successfully
completed the pre-submission seminar (held on 02.12.2019)
requirement, which is part of his/her Ph. D programme on his/her
thesis entitled, “INVESTIGATION FOR THE IMPROVEMENT OF
PERFORMANCE BY EDM PROCESS USING MULTI HOLED
ELECTRODE AND POWDER MIXED DIELECTRIC”.
Date: , August, 2021 Date: , August, 2021
Prof. (Dr.) M.K. Pandey Prof. (Dr.) Abhay Bansal
Joint Head, A.S.E.T. Joint Head, A.S.E.T.
Amity University Uttar Pradesh, Amity University Uttar Pradesh,
Noida Noida

ix
COPYRIGHT TRANSFER CERTIFICATE
Title of the Thesis: INVESTIGATION FOR THE IMPROVEMENT OF
PERFORMANCE BY EDM PROCESS USING MULTI HOLED
ELECTRODE AND POWDER MIXED DIELECTRIC
Ph.D. Scholar’s Name: PARIDHI MALHOTRA
Enrollment No.: A2366616001
COPYRIGHT TRANSFER
The undersigned hereby assign to the Amity University Uttar
Pradesh copyright that may exist in and for my thesis submitted for
the award of the Ph. D degree.

x
ACKNOWLEDGEMENTS
I would like to extend thanks and gratitude to the many people, who so generously
contributed to the work presented in this thesis. I honestly feel short of words to
acknowledge all those who helped me directly and indirectly during this research work.
With due regards and great delight, I convey my heartfelt gratitude and indebtedness to
my supervisor Dr. R.K Tyagi, Professor and Dy. HOD, Department of Mechanical
Engineering, A.S.E.T., Amity University Uttar Pradesh, Noida for skillful guidance,
persistent encouragement, proficient evaluation and conscientious supervision
throughout this academic endeavor. He was always available to help me with utmost
care, kind attention and prudent suggestions during odd hours of the job. His hard-
working nature and methodical suggestions were a constant source of encouragement to
me. It is owing to his guidance, expertise, inquisitive attitude and tireless efforts apart
from his working hours that I find my vision even more broadened. I earnestly thank
him from the core of my heart for being a consistent source of inspiration right through
the beginning till the end.
I am extremely thankful to Dr. Basant Singh Sikarwar, Professor and Head,
Department of Mechanical Engineering, A.S.E.T., Amity University Uttar Pradesh,
Noida, for his immovable help, support, and exhortation during my time as a Ph.D.
student with him. I was very lucky to have a supervisor who genuinely cared about my
work and rushed to react to my inquiries and concerns.
I am extremely thankful to Dr. Andriya Narasimhulu, Assistant Professor,
Manufacturing Processes Engineering Department, Netaji Subhas University of
Technology, New Delhi for the continuous guidance, encouragement and advice he has
provided throughout my time as his Ph.D. student. I have been extremely fortunate to
have a supervisor who cared so much about my work, and who responded to my
questions and queries so promptly. It is my sincere regard to thank him as at many
stages in the course of this research work as well as dissertation. His positive outlook
and confidence in my research inspired me and gave me confidence. With his all-time
positive and encouraging attitude towards my research work, I whole heartedly thank
him for being my steady and reliable source of motivation.
I am very much thankful to all the members of my doctoral committee including Dr.

xi
Pallav Gupta, Assistant Professor (Grade III), Department of Mechanical Engineering,
Amity University Uttar Pradesh, for spending his valuable time in reviewing and
critically examining the work. In addition, I would thank all the members for their
comments on my work resulting in enhancing the quality of the thesis.
My heartfelt gratitude is due to Dr. P.M Tiwari, Associate Professor amd Head
(Research and Publication) for the support, encouragement and providing the necessary
facilities to carry out and complete this work on steady course.
I also wish to express my deep sense of gratitude to all the faculty and staff members,
particularly Dr. Nishant Singh, Associate Professor, Hindustan College of Science and
Technology, Farah, Mathura, for the much-needed support throughout my work. I was
highly benefited from his advice, particularly in exploring new ideas, understanding
concepts and performing experimental work. Dr. Puneet Mangla, Head of Department,
Mechanical Engineering Department, Hindustan College of Science and Technology,
Farah, Mathura, and to Dr. Jimmy Mehta, Assistant Professor, Manav Rachna
International institute of research and studies for their tremendous support. Mr. Ramji,
Lab Technician, Department of Mechanical Engineering, Amity University Uttar
Pradesh and all the people who with their encouraging and caring words, constructive
criticism and suggestions have contributed directly or indirectly in a significant way
towards completion of this research work. My deepest appreciations are due to the
research scholars under the supervision of Dr. R.K Tyagi and Dr. Pallav Gupta. They
have always stood by me in all difficult times and reinforced my confidence. Their
never-ending support is a constant source of motivation and always keeps me going.
I bow with gratitude for my parents and my brother Mr. Nakul Malhotra, who are the
most precious people in my life and without their efforts I would have never achieved
this milestone. I feel honored in recognizing the love and affection of my husband Mr.
Charul Piplani and my adorable son Rudra Piplani.
I express my gratitude to all those, with whom I have worked, interacted and whose
thoughts have helped me in furthering my grasps and understanding of the work.
Last but not the least, I bow in reverence to ALMIGHTY GOD who has always
showered blessings on me at each and every step to complete this thesis.
PARIDHI MALHOTRA

xii
TABLE OF CONTENT
UNDERTAKING FROM THE PhD SCHOLAR iii
DECLARATION CERTIFICATE iv
CERTIFICATE FROM THE GUIDE v
CERTIFICATE FROM THE CO-GUIDE vi
COURSE WORK AND COMPREHENSIVE EXAMINATION
COMPLETION CERTIFICATE
vii
PRE-SUBMISSION SEMINAR COMPLETION CERTIFICATE viii
COPYRIGHT TRANSFER CERTIFICATE ix
ACKNOWLEDGEMENTS x
TABLE OF CONTENT xii
LIST OF FIGURES xv
LIST OF TABLES xix
ABBREVIATIONS xx
ABSTRACT xxii
CHAPTER 1 INTRODUCTION 1 – 27
1.1.Background and Motivation 2
1.2.Classification of the Un-Conventional Machining Processes 3
1.3.Electrical discharge machining (EDM) 4
1.4.Background of EDM 6
1.5.Various Types of EDM Techniques 7
1.6.Various Research areas of EDM 13
1.7.Parts of EDM 13
1.8.Principle of EDM 15
1.9.EDM process parameters 16
1.10. Benefits of EDM 19
1.11. Disadvantages of EDM 19
1.12. Utilizations of EDM 20
1.13. Composite materials 20

xiii
1.14. Classification of Composites 20
1.15. Advantages of composite materials 22
1.16. Disadvantages of composites materials 23
1.17. Aluminum metal matrix composites 23
1.18. Objectives 26
1.19. Summary of this chapter 27
CHAPTER 2 LITERATURE REVIEW 28 – 58
2.1.EDM Process 29
2.2.Composites 43
2.3.Summary of the Reviewed Literature 58
CHAPTER 3 MATERIALS AND METHOD 59 – 69
3.1.Workpiece 60
3.2.Tool electrode 63
3.3.Dielectric 64
3.4.Methodology 65
3.5.Equipment’s and Facilities 65
3.6.Process of EDM 67
CHAPTER 4 RESULTS AND DISCUSSION 70 – 96
4.1.Comparative analysis of Micro Structural and mechanical
properties of Al-SiC-Mg and Al-B4C-Mg Particulate Metal
Matrix Composite
72
4.2.Comparative investigation of traditional EDM and rotary EDM
of hybrid composite (Al7075/SiC/Mg)
78
4.3.Comparative prediction of the influence of process parameters
during CAEDM and REDM of hybrid metal matrix composite
82
4.4.Comparative analysis of REDM, Gas Assisted-EDM, and Gas
Assisted Powder Mixed-EDM of the hybrid MMC
87
4.5.Comparison of machining efficiency of gas assisted powder
mixed EDM of hybrid MMC based on different material of tool
electrode
94
CHAPTER 5 CONCLUSION 97 – 100

xiv
5.1.First stage Conclusions
5.2.Second stage Conclusions
CHAPTER 6 FUTURE SCOPE 101- 103
6.1.Key Points 102
REFERENCES 104
LIST OF PUBLICATIONS 115
PERSONAL PROFILE 143

xv
LIST OF FIGURES
Figure Number Caption Page Number
1.1 Non-Conventional Machining Process 3
1.2 Electrochemical machining system 4
1.3 Conceptualization of EDM process 5
1.4 Working of EDM 7
1.5 Process of Wire EDM 8
1.6 Die sinking EDM 9
1.7 Micro EDM processes 10
1.8 Powder mixed EDM 11
1.9 Dry EDM 13
1.10 Research areas in EDM 14
1.11 Various components of EDM process 15
1.12 Principle of EDM 15
1.13 Classification of composite on the basis of matrix material 21
1.14 Different types of reinforcement in composites 21
1.15
Classification of composite on the basis of the
reinforcement materials
21
1.16
Classification of the composite materials within the group
of materials
22
2.1 Process of EDM 30
2.2 Working principle of EDM 31
2.3 Design of copper ring tool shaped B-EDM 32
2.4 Experimental setup 32
2.5
Solid models of workpiece and interference between
work and tool
33
2.6
Effect of current and powders on machined surface
characteristics
33
2.7
Micro slit made with (a) kerosene (b) Al + kerosene
medium
34
2.8 Influence of micro-Cr powder addition on recast layer
formation
35

xvi
2.9 Effect of Nano powder addition on the recast layer
formation
35
2.10 The principle of dry EDM 36
2.11
Comparison of the section view of the craters obtained
using different dielectrics and polarities
36
2.12 Simulation Results 37
2.13
Variation of volume of material removed per discharge
as the operation progresses
38
2.14 Principle of the powder mixed EDM process 39
2.15
Graph showing variation of MRR with respect to powder
size
40
2.16
Mechanism of electromagnetic field application in
DEDM
41
2.17 Surface morphology comparison of with and without
cryogenically cooled work pieces
41
2.18
Schematic diagram of the experimental apparatus for
producing the MMCs
44
2.19 Machining of Metal Matrix 45
2.20 Composite Material 46
2.21 AA6061 without reinforcement 47
2.22 Die-sinker EDM with external circulation system 48
2.23
Distribution of ceramic Al2O3 particulates in stir cast
AA2014composites
49
2.24 Effect of hardness 49
2.25
Equivalent von Mises Stress Distribution during μUSM
Process
50
2.26 Microstructure of W1 after EDM 50
2.27
Roughness value corresponding to each experimental
condition
51
2.28 Crater topography of machined PRMMC specimen 52
2.29 Microstructure of 15 vol% SiCp/A356 Al (500×) 53
2.30
SEM micrograph of recast layer across machined surface
with powder mixed dielectric EDM
54
2.31
SEM micrographs of EDM machined surface (EDM-
machining conditions: pulse current 15A, pulse duration 10
μs, gap voltage 60V)
55
2.32 Macrograph of FSP zone of surface hybrid composite 56

xvii
2.33 Cross-sectional micrograph of surface hybrid composite 56
2.34
SEM photograph of electric discharge machined surface
of Al 6061 composites reinforced with SiC and graphite
particles at a voltage 50V and a flushing pressure 3psi
57
2.35 Micrograph of as-cast hybrid composite 58
2.36 Micrograph of 1700C ageing heat treated hybrid
composite
58
3.1 Different steps during the process of stir casting 61
3.2 Fabricated aluminum MMC 62
3.3 Stir casting setup 62
3.4 Schematic diagram of copper tool electrode 63
3.5 Different types of Tool utilized in the present research 63
3.6 Classification of the dielectric oil 64
3.7 EDM machine 66
3.8 Weighing balance 66
3.9 Surf – test SJ-210 surface roughness tester 67
3.10 Scanning electron microscopy 67
3.11 Gas assisted powder mixed EDM set up 69
4.1 Outcome of Vickers hardness test of Al(7075) alloy 73
4.2 Tensile specimen for the present research 74
4.3 Tensile specimen as per ASTM standard 74
4.4 Results of the tensile strength 74
4.5 Results for hybrid composites 76
4.6
Comparison of electrical conductivity of both the Al-SiC
and Al-B4C nanocomposites
77
4.7 Effect of pulse duration on MRR 78
4.8 Effect of peak current on MRR 78
4.9 Effect of duty cycle on MRR 79
4.10 Effects of peak current on EWR 80
4.11 Effects of pulse duration on EWR 80
4.12 Effects of duty cycle on EWR 81
4.13 Impact of duty cycle on the MRR 82
4.14 Impact of tool rpm on MRR 82
4.15 Impact of pulse on time on MRR 83
4.16 Impact of peak current on MRR 83

xviii
4.17 Impact of peak current on EWR 85
4.18 Impact of pulse duration on EWR 85
4.19 Impact of tool rotation on EWR 85
4.20 Impact of duty cycle on EWR 86
4.21 Effects of peak current on MRR 88
4.22 Effects of pulse duration on MRR 88
4.23 Effects of tool rotation on MRR 89
4.24 Effects of duty cycle on MRR 89
4.25 Effect of peak current on EWR 90
4.26 Effect of pulse duration on EWR 90
4.27 Effect of tool rotation on EWR 91
4.28 Effect of duty cycle on EWR 91
4.29 Microscopic view of SEM image 92
4.30 Microscopic view of SEM images 93
4.31 MRR Versus Pulse duration 94
4.32 MRR Versus Peak current 94
4.33 MRR Vs duty cycle 95
4.34 EWR Versus Pulse duration 95
4.35 EWR Versus Peak current 96
4.36 EWR Vs Duty cycle 96

xix
LIST OF TABLES
Table Number Title Page Number
1.1 Physical properties powders in powder-mixed EDM
(PMEDM)
12
1.2 Industry specific applications of composite materials 24
1.3 Different aluminium matrix composites for various
components used in automobile industries
25
1.4 Comparison of stir casting with other methods 25
2.1 Advanced aluminum alloy composite combinations and
its applications
45
2.2 Mechanical properties of LM6 47
3.1 Properties of the reinforcement 61
3.2 Parameters selected for stirring 62
4.1 Results of the hardness test Results of hardness test of
Al7075-SiC-Mg & Al7075-B4C-Mg
73
4.2 Results of tensile strength 74
4.3 Results of the experimental and theoretical density of the
nanocomposites. Results of theoretical and experimental
density Al7075-SiC-Mg and Al7075-B4C-Mg
75

xx
ABBREVIATIONS
EDM Electrical discharge machining
REDM Rotary electrical discharge machining
GAEDM Gas assisted electrical discharge machining
GAPMEDM Gas assisted powder mixed electrical discharge machining
MRR Metal removal rate
EWR Electrode wear rate
TWR Tool wear rate
SR Surface roughness
TEMP Temporary
AJM Abrasive jet machining
USM Ultrasonic machining
WJM Water jet machining
AWJM Abrasive water jet machining
AFM Abrasive flow machining
MAF Magnetic abrasive finishing
CHM Chemical machining
ECM Electro chemical machining
PCM Photo chemical machining
PBM Plasma beam machining
LBM Laser beam machining
EBM Electron beam machining
IBM Ion beam machining
CNC Computer numerically controlled
WEDM Wire electrical discharge machining
PMEDM Powder mixed Electrical discharge machining
PMC Polymer matrix composite
MMC Metal matrix composite
CMC Ceramic matrix composite
AMMC Aluminum metal matrix composite
IRSR Improvement ratio of surface roughness

xxi
RSM Response surface methodology
WLT White layer thickness
DEDM Dry electrical discharge machining
MADEDM Magnetic field assisted dry electrical discharge machining
CNT Carbon nano tubes
MWCNT Multi walled carbon nano tubes
DOE Design of experiments
S/N Signal to noise ratio
UTS Universal testing machine
SEM Scanning electron Microscope
NMMC Nano metal matrix composite
CAEDM Compressed air assisted electrical discharge machining process
ANOVA Analysis of variance
RCL Re-cast layer
PAMC Particulate aluminium matrix composite
CFRP Carbon fibre reinforced polymer
RHA Rice husk ash
GRG Glass reinforced gypsum
PRMMC Particle reinforced metal matrix composite

xxii
ABSTRACT
As the need for light weight structural materials increases, in aerospace and automotive
applications, magnesium metal matrix composites are becoming increasingly important.
The recent study has a novel goal of creating an Al7075 hybrid composite and
evaluating its mechanical characteristics and surface morphography. Boron carbide as
well as silicon carbide (both available in powder form) were added to the alloy in
various amounts to test their TEMP effects in combination with magnesium powder.
Boron carbide (also referred as black diamond) was preferred because it is exceptionally
durable and has well liked neutron shielding qualities, as it is capable of absorbing them.
After diamond and cubic boron nitride it is the third hardest non-material in respect of
ionising radiation stability. Silicon carbide was chosen owing to its great strength, in
addition its hardness, and wear resistance. Magnesium was chosen because it is the
lightest of all metals and has excellent heat dissipation and dampening properties.
TEMP has paramount applications in the automotive sector, aerospace sector, and
defence applications since it is lightweight. The utilisation of a hybrid metal matrix
composite permit for admirable micro-part dimensional precision machining of micro-
parts, revealing new possibilities for Al-SiC-Mg and Al-B4C-Mg micro-components.
For the machining of complicated cavities, EDM is sort of the most common modern
unconventional machining technologies. EDM has been increasingly popular in recent
years. The melting and vaporisation caused by the electrical discharge formed amid the
workpiece and the tool electrode, which is segregated by the dielectric fluid, separates
the material. On account of friable and nonconductive nature of the reinforcing
ceramics, poor surface polish, limited material removal, and significant tool wear are
utmost pressing issues in the EDM process. The EDM process has seen significant
advances in recent years, making it more efficient.
When it advances to process reactions like MRR and EWR, an effort has now been
made to equate rotary EDM (REDM), gas-assisted EDM (GAEDM), and gas-assisted
powder mixed EDM (GAPMEDM) processes with hybrid ceramic composites. MRR,
EWR, and surface topography have all been studied colossally concerning input
parameters. The rotation of the electrode improves the

xxiii
flow of dielectric and the effective expulsion of remains from the void amid the
workpiece and the machining tool, as claimed by the findings of the experiments. When
rotary EDM is used instead of traditional EDM, the outcome reveals a higher MRR and
lower EWR. Due to the brittle and non-conductive character of the reinforcing ceramics,
low material removal and significant electrode wear are few key challenges in EDM
processing of hybrid metal matrix composites. For this aim, methods such as rotary
electrical discharge machining (REDM), gas-assisted electrical discharge machining
(GAEDM), and gas-assisted powder mixed electrical discharge machining
(GAPMEDM) are compared under the pretext of the material removal rate along with
the electrode wear rate. The metal removal rate of the gas-assisted powder mixed
electrical discharge machining method is up to 75 percent higher than the REDM
process, and the electrode wear rate is at least 25% lower. The metal removal rate
attained by the gas-assisted powder mixed electrical discharge machining process is at
least 45 percent higher than the GAEDM process, and the rate of electrode wear is not
less than 15% lower. In comparison to GAEDM and the traditional REDM method,
experimental findings disclose that GAPMEDM has a higher MRR and descended
EWR.

2
CHAPTER 1
INTRODUCTION
1.1. Background and Motivation
Machining is a manufacturing phrase enclosing a wide range of techniques
and procedures. Machining can be delimited as the process involving removal of
material from the workpiece using various machines that are driven by power and
a variety of tools to produce a specific geometry with explicit accuracy and surface
quality. Nearly all the metal components need a few forms of machining in the course
of the manufacturing process. The machining processes can either be subtractive
manufacturing otherwise additive manufacturing. In various engineering applications,
numerous parts or components have to be interchangeable to function correctly as
well as reliably during the course of their service. Material removal processes
comprise of cutting, grinding, and drilling[1]. Machining operation comprises of the
workpiece, cutting tools, machine tools, fixtures and machining parameters. The
TEMPEffect of any process can be assessed in terms of machining rate, and surface
finish acquired. For the material evacuation process the source of energy can be either
mechanical or electrical[2]. Machining is of two types i.e., conventional machining
and non-conventional machining.
• Conventional machining
The machining process utilizes mechanical energy to remove the material
from the surface. Boring, turning, slitting, grinding are some of the conventional
machining processes. An increased amount of time, money and energy is utilized for
machining hard materials and alloy using conventional methods. Because of the
induced residual stresses during the manufacturing process, high accuracy and
precision are hard to achieve. In the conventional machining process, there exists a
direct link between the tool and the workpiece. Owing to the lesser lifetime of the tool
a huge amount of material is wasted in conventional machining.
• Non-conventional or Unconventional or Modern machining
It uses advanced or modern technology to machine the materials. In non-
conventional machining processes, there is no direct contact between the tool and the
workpiece. Using conventional methods high accuracy and better surface finish can

3
feasibly be attained. Non-conventional machining plays a significant role in the
automobile, mould making, aircraft industries. These methods are used to
manufacture geometrically complex and high-precision parts. Various micro
machined components and low rigidity structures with rigid tolerances and enhanced
surface qualities can be easily machined using advanced methods[3]. Through the
years greater TEMPthan 20 different unconventional processes have been evolved and
implemented in diversified manufacturing industries. Figure 1.1 depicts schematic
non-conventional machining process.
Figure 1.1. Non-Conventional Machining Process[4]
1.2. Classification of the Un-Conventional Machining Processes
Depending on the type of energy source, the further classification could be carried out
as –
• Mechanical machining process
The machining process whereabouts erosion of the workpiece material takes
place by a high-velocity stream of abrasives or water[5], different mechanical
machining processes are –Abrasive jet machining (AJM), Ultrasonic machining
(USM), Water jet machining (WJM), Abrasive water jet machining (AWJM),
Abrasive flow machining (AFM), and Magnetic abrasive finishing (MAF)[6].
• Chemical machining process
It uses a chemical or electrochemical dissolution effort to remove the
machining allowance using ion transfer. It is also referred as the electrolysis process.

4
Chemical machining (CHM), Electrochemical machining (ECM) as shown in Figure
1.2, Photochemical machining (PCM) are some of the types of chemical machining.
• Thermal Processes
In involves the removal of material by melting or vaporizing the workpiece.
Phenomenon such as micro-cracking, formation of heat-affected zones occurs during
the machining process.On the basis of the heat source, they are further classified as -
• Plasma Source-Electrical discharge machining (EDM), Plasma beam
machining (PBM)
• Photon source- Laser beam machining (LBM)
• Electron’s source- Electron beam machining (EBM)
• Ion source- Ion beam machining (IBM)
Figure 1.2.Electrochemical machining system[7]
1.3.Electrical discharge machining (EDM)
An electro thermal non-customary machining measure which uses electrical
energy to produce electrical flash and sparkle’s nuclear power is utilized to eliminate
the material from the workpiece. EDM is perhaps the crudest non-customary
machining measure. EDM measure depends on thermoelectric energy created between
the workpiece and a terminal[8].
It’s typically used to automate difficult calculations in small groups or even on
a task shop setting. In the instance of advancement of super-intense electrically
conductive materials like carbides, treated steels, hastelloy, nit alloys, wasp alloy,
mnemonics, and so forth, the interest for non-customary assembling measures

5
TEMPhas become more applicable. These very intense materials, which have broad
applications, like assembling of kicks the bucket, auto, and aviation segments, are
extremely hard to machine by regular techniques. To machine all the electrically
conductive materials regardless of their hardness and strength, EDM measures widely
utilize nuclear power[9]. In non-traditional machining measures EDM has colossal
potential by virtue of its flexibility and applications in present-day enterprises. The
EDM cycle can likewise deliver openings, outer shapes, profiles, cavities in an
electrically conductive workpiece through controlled use of high-recurrence electrical
releases by disintegrating or liquefying the workpiece material in a specific region.
The electrical releases are the consequences of controlled beats of direct flow and
happen between the apparatus terminal (cathode) and the workpiece (anode)[10].
Figure 1.3 Conceptualization of EDM process[11]
Figure 1.3 shows the detailed conceptualization of EDM process. Probably the
most popular application of the EDM cycle is in an instrument, and form making [12].
Material evacuation rate is characterized as the volume of material eliminated over a
unit period. It is ordinarily communicated by the unit (mm3
/min). A high worth of the
release voltage, top current, beat length, obligation cycle, and the low upsides of
heartbeat stretch will result in a higher MRR. Notwithstanding these previously
mentioned electrical boundaries, non-electrical boundaries and material properties
likewise have their own critical TEMPEffect on the MRR.
Instrument wear proportion can be characterized as the portion or volume of materials
eliminated from the device terminal to that of the work. It tends to be likewise called
terminal wear proportion. Instrument wear proportion relies upon anode extremity and
the properties of terminal materials. Surface unpleasantness is a vital boundary to

6
consider in kick the bucket sinking EDM. In most pass-on sinking activities, separate
completing and roughing tasks are done to finish the eventual outcome. It is addressed
by the normal SR and estimated in microns[13]–[15].
1.4. Background of EDM
In 1770 the English scientist Joseph Priestly found the erosive impact of
electrical releases or starts on metals. In 1940 two Russian researchers, Dr. B.R
Lazarenko and Dr. N.I Lazarenko harvested this thought and applied it in their
research. During the second universal conflict, they were relegated wif an undertaking
by the Soviet government to examine the shimmering between tungsten electrical
contacts, since wear was a major issue for the upkeep of car motors. Specialists
tracked down that the sparkles were more uniform in oil TEMPthan in air. In 1943
they made the first sparkle disintegration machine which was fit to dissolve hard
metals like tungsten or tungsten carbide.
The Lazarenko EDM framework utilizes an obstruction capacitance sort of
force supply and it was utilized in EDM machines till the 1950's and afterward went
about as the model for progressive advancement in EDM. Because of the low quality
of the electronic parts, the presentation of the machine was not great.
During the 1960s the progression of the semiconductor business prompts the
critical modernization of EDM machines. During this time, Die sinking EDM
machines became solid and created quality controlled surfaces wif precision however,
wire cutting machines were still at their earliest reference point. During the ensuing
many years, extraordinary enhancements were made in generator configuration,
measure automatization, servo control, and advanced mechanics. The utilization of
heartbeat and strong state generators tackled existing issues wif powerless anodes just
as the innovation of the circling frameworks. During the 1970s the quantity of anodes
is diminished to make depressions. In 1980 PC mathematically controlled (CNC)
EDM was created in the USA.
During the 1990s fuzzy logic control, neural networks, reaction surface
methodology, Taguchi optimization, and so forth are some new techniques that were
utilized to control the EDM cycle, which increments applied fundamental EDM[8],
[16].

7
1.5. Various Types of EDM Techniques
There are numerous sorts of EDM. This exploration arranged EDM measures
under three primary classifications, to be specific, Sinker EDM, Wire EDM, and
quick opening penetrating EDM. Flash machining functioning rule depends on the
disintegration of the material by continuous sparkles between the workpiece and the
gadget or device that is submerged in a dielectric medium. A hole isolates the
workpiece and the cathode to build up a beat sparkle through which the dielectric
liquid streams. Schematic portrayal of the essential working standard of EDM
measure has appeared in Figure 1.4.
Figure 1.4 Working of EDM[17]
1.5.1. Wire Electrical discharge machining process (WEDM)
A paramount emerging non-conventional manufacturing process is wire
electrical discharge machining. Roy, A.; Narendra, N.; Nedelcu, D. Experimental
investigation on a variation of output responses of as-cast TiNiCu shape memory
alloys using wire EDM [18], [19]. Widely this process is used to machine hard
materials and intricate shapes which are not possible with conventional machining
methods. It is more efficient and economical. In wire EDM, an electric spark is
created between an electrode and the workpiece [20], [21].
The spark is the visible evidence of the flow of electricity. This electric spark
creates intense heat of temperature moving from 8000 to 12,000 degrees Celsius,
which melts almost anything. The spark is carefully controlled and localized so that it
only affects the surface of the materials. The EDM process does not affect the heat
treat below the surface of the workpiece. In wire EDM, the spark always takes place

8
in the dielectric of de-ionized water. The conductivity of the water is carefully
controlled for making an excellent environment for the EDM process. Here, the water
acts as a coolant and flushes away the eroded metal particles. The working principle
of wire EDM is shown in [22], [23]. The electrode wire is mainly fabricated of either
brass or copper material. 0.5 to 0.25 mm is the diameter range of the wire. To strand
the wire, it is wound on a two-wire spool that is turned in the same direction. Wire
movement can reach 3 meters per minute. The material is removed by generating a
spark between the moving electrode wire and the work piece. Rather than drowning
the entire workpiece, the dielectric is confined. To process the machining operation, it
is using a CNC controlled machine setup.The basic process of WEDM is depicted in
Figure 1.5
Figure 1.5 Process of Wire EDM[17]
In light of the key qualities of WEDM, it is realized that the cycle factors pulse
on time, spark voltage, wire pressure, wire feed, pulse off-time, and flushing pressure
are the primary cycle factors of the WEDM[24].
1.5.2. Die Sinking EDM
It is additionally called depression type EDM or volume EDM. It comprises of
an anode and workpiece lowered in a protecting fluid, for example, more commonly,
oil, or, less as often as possible, other dielectric liquids. The cathode and workpiece
are associated wif a reasonable force supply. The force supply produces an electrical
voltage between the two sections. As the anode moves toward the workpiece, the
dielectric breakdown happens in the liquid, which frames a plasma channel and little
flash leaps. These bouncing sparkles as a rule strike on each in turn. The sinker EDM

9
measure utilizes an electrically charged anode that is designed to a particular math to
consume the cathode's calculation into a metal segment. This cycle is ordinarily
utilized in passes-on and device fabricating. A schematic graph of a sinker EDM has
appeared in Figure1.6 [25], [26].
Here, the fundamental parts are the force supply, dielectric framework,
terminal, and the extreme; the principal segments are power supply, dielectric
framework, anode, and the servo framework. In this way, this is the schematic that
clarifies the rule of starting. The workpiece is normally associated wif the positive
terminal of the force supply.
Figure1.6 Die sinking EDM [27]
Here, the state of the apparatus is unique, and a similar shape will be
reproduced also on the workpiece. The starting happens through the various zones or
the through various focuses which are nearer to the workpiece because of the reality
of this starting, the plasma arrangement zone will make air pockets and high pressing
factor which hence fall and dissolve the workpiece. At whatever point the starting
happens, the disintegration of the workpiece will likewise happen. Subsequently, we
have found on account of EDM, little disintegration will happen on the anode too.
Sinker EDM is one of the high-level techniques for machining electrically conductive
materials frameworks. Along these lines, this is the schematic that clarifies the head

10
of starting. The workpiece is generally associated wif the positive terminal of the
power supply. Here, the state of the device is unique, and the same shape will be
recreated too on the workpiece. The starting happens through the various zones or the
through various focuses which are nearer to the workpiece. Due to the actuality of this
starting, the plasma arrangement zone will make the air pockets and high pressing
factor which along these lines implode and disintegrate the workpiece. At whatever
point the starting happens, the disintegration of the workpiece will likewise happen.
Along these lines, we TEMPhas seen in the instance of EDM, little disintegration will
happen on the cathode also. Sinker EDM is one of the progressed strategies for
machining electrically conductive materials[28]–[32].
1.5.3. Micro EDM
It is utilized to machine miniature openings and miniature shafts. This
interaction is likewise competent to machine minuscule distances across up to 5
micrometers and complex 3-dimensional micro cavities.Micro EDM measure is
essentially of four kinds for which the process is given by Figure 1.7.
Figure1.7 Micro EDM processes[33]
• Micro-wire EDM-In miniature wire EDM, a wire is utilized to cut a workpiece
that TEMPhas a width as little as 0.02mm.
• Die sinking micro EDM-In die sinking micro EDM, an anode having
miniature highlights is utilized to cut its identical representation in the
workpiece.

11
• Micro EDM drilling- In micro EDM boring, microelectrodes having widths
however little as 5-10 micrometers may be utilized to bore micro holes in the
specimen.
• Micro EDM milling- In micro EDM milling, microelectrodes having a width
however little as 5-10 micrometers may be utilized to deliver 3D pits by
embracing comparable system as that in regular processing.
1.5.4. Powder Mixed EDM
This is another procedure that increases the material removal rate by adding
some reasonable material in the type of powder blended in with the dielectric liquid of
EDM. Powder blended EDM upgrade abilities of the electric release machining
measure. When the appropriate powder is blended in with the dielectric liquid then it
increases the conductivity of the dielectric liquid, which further reduces the protecting
strength of the dielectric liquid to increase the spark gap distance between the anode
and the workpiece. This amplified flash hole flushes out the trash consistently. This
increased spark gap makes the machining measure steadier, thereby improving the
material expulsion rate and surface quality. At the point when a reasonable voltage is
applied, the spark gap is loaded up with added substance particles and the gap
distance arrangement between the apparatus and the workpiece expanded from 25-50
to 50-150 mm. The powder particles get invigorated, get sped up under the electric
field, and begin moving in a crisscross style. These charged particles go about as
conductors. The powder particles organize themselves under the starting region and
accumulate in groups as shown in Figure 1.8.
Figure 1.8 Powder mixed EDM[16]

12
The chain development helps in crossing over the gap between both terminals,
which causes the early blast. Quicker starting inside release causes quicker
disintegration from the workpiece surface in this way expanding the MRR.The impact
of the powder in the PMEDM mostly relies upon the powder boundaries, that is,
powder material, particle size, and molecule fixation[16], [22].
• Different Powders Used in EDM
Powders blended wif dielectric liquid in EDM can be ordered into six unique
sorts be specific, aluminum, silicon, chromium, graphite, silicon carbide, and nickel
Nano powder. Every one of these kinds TEMPhas its own attributes which makes it
reasonable to be utilized for various machining conditions. To meet the required
conditions, these powders have numerous properties like MRR, SR, TWR, and so on.
Their actual properties appear in Table 1.1
Table 1.1Physical properties powders in powder-mixed EDM (PMEDM) [34]
Material Density
(g/cm3)
Electrical
Resistivity (μΩ-
cm)
Thermal
Conductivity (W/m-
K)
Aluminum (Al) 2.70 2.89 236
Graphite C 1.26 103 3000
Chromium (Cr) 7.16 2.6 95
Copper (Cu) 8.96 1.71 401
Silicon (Si) 2.33 2325 168
Nickel (Ni) 8.91 9.5 94
Silicon Carbide (SiC) 3.22 1013 300
Titanium (Ti) 4.72 47 22
Tungsten (W) 19.25 5.3 182
Alumina (Al2O3) 3.98 103 25.1
Boron Carbide (B4C) 2.52 5.5 × 105 27.9
Carbon nano tubes
(CNTs)
2.0 50 4000
Molybdenum
Disulfide (MoS2)
5.06 106 138
1.5.5. DRY EDM
Dry EDM is a green climate cordial Electric discharge machining Technique
in which the fluid dielectric is supplanted by a vaporous dielectric. Gas at a high
pressing factor is utilized as the dielectric medium. In dry EDM, a cathode is framed
to be a slender walled pipe. The progression of high-speed gas into the hole works wif

13
evacuation of trash and forestalls extreme warming of the tool and workpiece at the
release spots as shown in Figure 1.9. The tool turns during machining not just works
wif flushing yet, in addition, improves the interaction security by diminishing arcing
between the cathodes The strategy was created to decline the contamination brought
about by the utilization of fluid dielectric which prompts the creation of fume during
machining and the expense to deal wif the squander. Dry EDM technique wif the
most limited machining time contrast wif oil pass on sinking EDM, and most minimal
cathode wear proportion. Material evacuation rate likewise gets improved by dry
EDM[35].
Figure 1.9 Dry EDM[36]
1.6. Various Research areas of EDM
EDM research can be divided into various major areas. Figure 1.10 presents
the various fields and aspects of research in the area of EDM along with its future
scope and other details.
1.7. Parts of EDM
The different parts and components indulged in the working operation of
EDM as shown in figure 1.11 are briefly discussed below. These include work piece,
apparatus electrode, dielectric liquid, servo framework, power supply and the pulse
generator.
• Work-piece- All the conductive material can be worked by EDM
• Apparatus Electrode-The EDM electrode is the tool that decides the state of
the cavity to be produced.

14
• Dielectric liquid - The EDM arrangement comprises the tank in which the
dielectric liquid is filled. Anode and workpiece lowered into the dielectric
liquid.
• Servo framework - The servo framework is directed by signals from the gap
voltage sensor framework in the power supply and controls the feed of the
terminal and the workpiece to decisively coordinate wif the pace of material
evacuation.
• Power supply-The power supply is a significant piece of any EDM framework.
It changes the rotating current from the fundamental utility supply into the
pulse direct current (DC) required to create the spark release at the machining
gap.
• DC pulse generator – It is liable for providing pulse at a specific voltage and
current for a particular measure of time.
Figure 1.10 Research areas in EDM

15
Figure 1.11Various components of EDM process
1.8. Principle of EDM
The standard of EDM is to utilize the dissolving impact of controlled electric
flash releases on the terminals. It is subsequently a warm disintegration measure. The
flashes are made in a dielectric fluid, for the most part, water or oil, between the
workpiece, what's more, a cathode, which can be considered as the cutting device.
There is no mechanical contact between the anodes during the entire cycle. Since
disintegration is delivered by electrical releases, both anode and workpiece need to be
electrically conductive. Along these lines, the machining interaction comprises
progressively eliminating little volumes of workpiece material, liquid, or disintegrated
during a release.
Figure1.12 Principle of EDM [37]

16
Its functioning standard depends on electro thermal energy, where electrical
energy is utilized to create an electrical spark and nuclear power of the flash is
utilized for material removal.EDM measure utilizes electrical energy which further
produces a channel of plasma between the cathode and anode and transforms it into
thermal energy. The workpiece and the anode are isolated by an especially little gap
known as a flash gap. The pulse spark happens in this gap loaded up with a protecting
medium [37]. The complete system is presented by Figure 1.12.
The protecting impact of the dielectric medium helps in staying away from
electrolysis consequences during the machining interaction. The terminals move
towards the workpiece until the gap is little enough wif the goal that the applied
voltage is sufficiently high to ionize the dielectric liquid. The conductivity of the
apparatus and workpiece ought to be kept up for the cycle to be done. The dielectric
properties utilized in EDM are straightforwardly identified wif the flushing rate and
flash gap. The cavity development can be accomplished by setting the different
electrical boundaries according to the material expulsion rate needed for machining.
The state of the apparatus surface is duplicated on the workpiece surface during
machining. Tan again, the little material expulsion rate causes a lethargic machining
measure and furthermore influences the beat release at different areas on the anode.
The time-stretch changes wif the spark gap and starts pulse for smooth machining
surface age. The non-uniform part of disintegration in the workpiece brings about a
decrease in measure boundaries like material removal rate (MRR), tool wear rate
(TWR), and surface roughness (SR).
1.9. EDM process parameters
The parameters of EDM process are classified as input parameters and output
parameter.
1.9.1. Input parameters
The input parameters are classified in two types-:
• Electrical parameter
• Peak current – For a given pulse the maximum quantity of current flowing
through the tool and the workpiece is called the peak current.
• Open circuit voltage –It is the maximum potential difference across the tool
electrode and workpiece electrode before the flow of current.

17
• Ton – time span for which the current flows between the machining zone in
each cycle
• Toff- it is the duration between two simultaneous discharges.
• Electrode gap- In EDM the electrode gap is maintained by servo mechanism.
• Duty cycle –It is deliberated by dividing the Ton by the entire time taken in a
complete cycle (Ton/(Ton+Toff).
• Non-electrical parameter
• Dielectric fluid- It flows between the tool and workpiece through external jets
or sometimes through the holes made on the surface of the electrodes.
Dielectric fluid acts as an insulator and cools the tool along with the
workpiece by flushing the unwanted particles from the spark gap. Selection of
a good dielectric like kerosene oilis noteworthy as it affects the performance
of the process.
Various researches have been implemented for the up gradation of the
technology and mechanism of EDM process, but still there are many faces of the
process which still needs awareness for intensifying the process. Selection of suitable
dielectric is one such aspect of the process. Gaseous dielectric, powder mixed
dielectric is some of the techniques which are adopted by various researchers and
proved to inflate the efficiency of the process.
• Flushing
Flushing is preferably known as the proper transmission of the insulating fluid
between the electrodes. Improper flushing of the dielectric fluid may lead to the
formation of bridges consequently causing short circuit. Flushing techniques are
classified as follows-:
• Normal flow flushing
• Side flushing
• Reverse flow flushing
• Immersion flushing
• Electrode material
In the process of EDM it is mandatory for the electrode to be electrically
conductive. In EDM duplicate of the tool electrode is produced on the specimen. The
electrode material should be selected such that it should not erode much during the

18
machining as it will exert influence on the cost along with the efficiency of the
process.
• Rotation of the workpiece
In addition to the electrical process parameters in conventional EDM,
workpiece rotation is TEMPeffective in rotary EDM. In conventional EDM, debris
particles in the gap unavoidably enhanced discharge instability, according to
experimental results. The centrifugal force in rotary EDM, on the other hand,
enhanced gap cleansing and machining efficiency. Rotary EDM's MRR was up to
twice that of conventional EDM. With increasing rotation speed, the value of surface
roughness decreased. Micro voids and flaws on the machined surface can be reduced
by rotating the specimen[38]
• Rotation of the tool electrode
Due to the effect caused by centrifugal force on the workpiece, the rotational
movement of the electrode is used to boost Metal Removal Rate in EDM.
1.9.2. Output Variables
• Material removal rate (MRR)
Metal removal rate is commonly represented in cubic inches per hour (in3
/hr).
It takes more than just the appropriate machine settings to achieve an efficient MRR.
It also includes the direct energy lost during the EDM process.
• Electrode wear rate (EWR)
The EWR is the volume ratio of the material removed from the micro tool
electrode to the material removed from the workpiece. TWR is sometimes computed
by multiplying the weight difference between the micro tool before and after
machining by the machining duration.
• Surface Roughness (SR)
Surface finish is influenced by a number of variables, including on-time, peak
current, electrode material, and workpiece material. The electrode will make a reverse
image of whatever shape or form it has as the machining cycle advances.
Imperfections in the electrode surface will appear on the workpiece surface as well.
This includes material loss due to high temperatures or particle loss due to wear. The
electrode will show up on the workpiece if it is pitted. The ultimate surface finish will
be a mirror image of the surface of the electrodes. Short on-times and low peak

19
current settings yield the best results, as smaller craters in the work metal are
produced. There will be no progress until these prerequisites are met.
1.10. Benefits of EDM
• Any metal, regardless of hardness, brittleness, or toughness, can be machined.
• Harder materials, such as steel alloys or tungsten carbides, can be replicated
for molding and other non-traditional machining techniques, such as forging
and press tools.
• When dies are hardened, they can be machined.
• Complex shapes can be duplicated.
• Very fine holes can be drilled with extreme precision.
• The precision is excellent. It is possible to attain a tolerance of 0.005 mm.
• Micro-craters in EDM produced work pieces can efficiently hold lubricants,
allowing for the creation of a wear-resistant surface.
• There is no physical contact between the tool and the w/p. There is no cutting
force used other than blasting pressure. As a result, delicate projects and
cylinders can be machined without being damaged.
• When compared to traditional machining method, harder metals may be
processed faster.
1.11. Disadvantages of EDM
• In comparison to traditional machining, the power required for machining is
Electrical Discharge Machining (EDM) is substantially higher. (120J/mm2)
• When materials become brittle at normal temperature, there is a risk of surface
breaking.
• On steel work pieces, a thin layer containing 4% carbon, typically ranging
from 0.01 mm to 0.10 mm, can be placed.
• EDM makes it harder to replicate tight corners.
• Sometimes the microstructures are deformed, and etching occurs as a result.

20
1.12. Utilizations of EDM
By and large, EDM has enormously utilized for machining without burr
complex shapes just as restricted spaces and visually impaired depressions. The
sinking of bites the dust, plastic embellishment, kick the bucket projecting
compacting, cold heading, expulsion, press devices, wire drawings are a portion of the
instances of its application. Negative instrument calculation can likewise be created
on a w/p if the appropriate apparatus can be made. EDM is exceptionally helpful for
machining little openings. It is likewise used to cut spaces in diesel fuel infusion
spouts. It is additionally utilized in airplane motors and brake valves and so forth
1.13. Composite materials
They are formed with the amalgamation of two or more dissimilar materials
and its constituting materials having observable interfaces to present distinctive
aggregation of properties of the merging materials[39]. The two constituents of
composite materials are the matrix (weaker constituent) and the reinforcement
(stronger constituent). The strength and the rigidity to support the structural loads are
provided by the reinforcement. The position and orientation of the reinforcement is
maintained by the matrix. The solitary characteristics and the composition of the
constituents control the overall physical and chemical characteristics of the
composites.
1.14. Classification of Composites
On the basis of constituents, the composite is categorized in two categories.
Figure 1.13 shows the classification of the composite material based on the type of
matrix material.
• Ceramic matrix composite constitutes matrix made up of ceramic materials
like oxides, carbides and nitrides of aluminum, silicon, zirconium and titanium. They
withstand very high temperature.
• Metal matrix composite is a class of materials comprised of matrix made up
of metals such as aluminum, iron, copper, magnesium. Properties of metal matrix
composite include high strength, high heat resistance, low thermal expansion
coefficient, and increased resistance to wear and tear.

21
• Polymer matrix composite constitutes matrix made up of polymer materials
such as epoxy, nylon, polyester, polyvinylchloride etc. Properties of PMC include
very high specific stiffness and specific strength. In addition, they also process high
manufacturing feasibility and are relatively cheaper.
Figure 1.13: Classification of composite on the basis of matrix material
Aside from this classification of composites on the basis of matrix material,
they are also classified on the basis of reinforcement material. Figure 1.14 and Figure
1.15 shows the classification of composite material on the basis of reinforcement
materials and composites. Besides, Figure 1.16 represents the classificationfor various
types of composites.
Fig. 1.14. Different types of reinforcement in composites –(a) particulate (b) short
fiber (c) continuous fiber (d) structural composites [40]
Figure 1.15 Classification of composite on the basis of the reinforcement materials

22
• Particulate composites comprised of particles suspended in matrix. Particles
may be of different shapes, size and configuration. Properties of particulate matrix
include improved strength, oxidation resistance and increased operating temperature.
• Fiber reinforced matrix composed of fibers or whiskers. They are of two
types’ short fiber reinforced and long fiber reinforced composite. They find
application in various fields such as automotive, aerospace, civil infrastructure and
many more.
• Structural composites are further classified as laminated composites and
sandwich panel composites. They are comprised of plastic, glass, wood and carbon
fiber materials. The properties of the structural composites depend upon the
constituents and geometrical design.
Fig. 1.16 Classification of the composite materials within the group of materials[41]
1.15. Advantages of composite materials
The idiosyncratic material comes into being by comprising the matrix and the
reinforcing material with worthier properties in comparison with their individual
properties. With time these materials have gained several advantages and wider
applications over traditional materials. Light weight, high directional strength,

23
controlled expansion and high resistance to fatigue makes the composites superior
than the metals. Other key advantages of composites include-
• High design flexibility
• Corrosion resistance
• Abrasion resistance
• Durability
• High manufacturing flexibility
• High thermal and electrical resistance
• Cost effectiveness
1.16. Disadvantages of composites materials
` Even though there are considerably huge numbers of advantages
accompanying the application of composites over the traditional materials, there are
handfuls of disadvantages too.
Some of the disadvantages of composites are listed below-
• High fabrication and assembly cost for job and batch production
• Low ductility
• Cannot be repaired easily as the structure loses integrity
• For sealing purposes, it requires appropriate finishing.
1.17. Aluminum metal matrix composites
These are very hard and light in weight material and have high resistance
against corrosion[42] .With numerous applications in industrial area Aluminum metal
matrix composite continue to exist as the most potentially viable candidate to be
researched[43].
In Aluminum metal matrix composites the reinforcement can be in the form of
continuous or discontinuous fibers, whiskers or particulates ranging in various volume
fractions. According to the different demands of the industrial applications, the
properties of AMMC can be tailored by suitable combinations of reinforcement,
matrix and the route followed to process the composites[44][45]. Aluminum
compounds, due to their low thickness and amazing strength, sturdiness, also,
protection from erosion, discover significant applications in the aviation field. Of
uncommon notice in such manner are the Al–Cu–Mg and Al–Zn–Mg–Cu

24
amalgams, vital precipitation-hard enable compounds. Aluminum-lithium
amalgams structure perhaps the main precipitation-hard enable aluminum
amalgams. Lithium, when added to aluminum as an essential alloying component,
TEMPhas the remarkable normal for expanding the versatile modulus and
diminishing the thickness of the amalgam. Naturally, the airplane business
TEMPhas had been the significant objective of this advancement. Al–Li
combinations are precipitation hard enable, similar as the Al–Cu–Mg also, Al–Zn–
Mg–Cu amalgams. The precipitation solidifying grouping in Al–Li amalgams is,
in any case, substantially more intricate TEMPthan that saw in regular
precipitation-hard enable aluminum amalgams. Various industrial applications of
aluminum composites are represented in Table 1.2.
Table 1.2 Industry specific applications of composite materials[46].
Industry Application
Electrical
and
Electronic
s
Insulation
for
electrical
construction
Cable
tracks
Support for
circuit breakers
Support for
printed
circuits
Antenna
s
Wind
turbine
Tops of
television
tower
Road
transport
Wheels,
shields and
radiator
grills
Transmissi
on shafts
Suspension
springs
Chassis
Suspens
ion
arms
Cabins,
seats
Body
component
Rail
transport
Fronts of
locomotives
Wagons Doors
Ventilation
housings
Structur
al parts
Seats
Interior
panels
Maritime
transport
Hovercrafts
Rescue
crafts
Patrol crafts
Antimine
ships
Racing
sailboat
s
Canoes Trawlers
Cable
transport
Aerial
tramways
Gondola
lifts
- - - - -
Air
transport
Gliders
Light
aircraft
and drones
Vertical/horizont
al tail plane
Wing boxes
Fuselag
e
Aircraft
brakes
and disks
Helicopter
component
Space
transport
Bodies Tanks Nozzles Heat shields - - -
Sports
and
leisure
Tennis and
squash
rackets
Skis
Windsurf and
skate boards
Bows and
arrows
Javelins
Protect -
ion
helmets
Bicycles

25
There are two methods for the fabrication of the Aluminum metal matrix
composite, one is the solid-state processing and the other one is liquid state
processing. Various reinforcements can be extensively used to amend the properties
of the composite material according to the demand and application of the process.
Table 1.3 represents application of different Al MMC. The major drawback
accustomed during the processing of Aluminum metal matrix composites is the
feebleness with molten state of the matrix[47].
Table. 1.3 Different aluminium matrix composites for various components used in
automobile industries[48]
Manufacturer Component Composite
Dura clan, Martin Marietta, Lanxide Pistons Al/SiCp
Nissan Connecting rod Al/SiCw
Toyota Piston rings Al/Al2O3 and AI/Boria
Honda Engine blocks Al/Al2O3
Zollner Pistons Al/fiberfrax
GKN, Duraclan Propeller shaft Al/SiCp
Dupont, Chrysler Connecting rods Al/Al2O3
Lotus, Elise, Volkswagen, Chrysler, Duraclan,
Lanxide
Brake rotors Al/SiCp
Table .1.4 Comparison of stir casting with other methods [49][50]
Process
Range of
shape
Range of
size
Metal yield
Damage to
reinforcement
Cost
Stir casting Wide Larger size
Very high,
>90%
No damage Least expensive
Squeeze
casting
Limited
Restricted
size
Low Severe damage
Moderately
expensive
Powder
metallurgy
Wide
Restricted
size
High
Reinforcement
fracture
Expensive
Spray casting Limited Large size Medium - Expensive
Lanxide
processing
Limited
Restricted
size
- - Expensive
• Liquid state processing
The discontinuous reinforcement phase is incorporated into the continuous
metal matrix phase in the liquid state in liquid phase processing methods, and the
molten metal is cast into desired shapes by conventional casting. Stir casting, compo
casting, squeeze casting, ultrasonic-assisted casting, infiltration, thermal spray, laser

26
melt-particle injection method, and other liquid state processing methods are
examples.
Table 1.4 depicts the comparison of stir casting with other fabrication
processes. The metal matrix is heated above melting temperature and reinforcement
materials are incorporated into a molten matrix using a mechanical stirrer in the stir
casting process. Mechanical stirring in the furnace is a critical component of the
process. In the mass production of MMCs, it is a very simple, flexible, and cost-
effective process. The non-homogeneity of the constituents, as well as the poor
wetability of the matrix and reinforcement, is the main drawback of this method due
to the cooling rate change from the surface to the centre.
• Solid state processing
Powder metallurgy, high-energy ball milling, spark plasma sintering, cold
spraying, diffusion bonding, and friction stir processing are examples of solid-state
processes[51].
1.18. Objectives
The current work is an investigation into the hybrid EDM process with the
goal of improving performance metrics. As a result, the current research focuses on
the fabrication of an aluminum metal matrix composite with two different types of
reinforcement. The study's main goal is to investigate the various properties of the Al
MMC that has been manufactured experimentally, as well as the results of the EDM
process with various assistances.
The focus of this research is on the fabrication of aluminum metal matrix
composites. The current work's reinforcement is silicon carbide, and the alloying
element is magnesium, both of which are discussed in detail in Chapter 3. The
primary goal of this study is to investigate various mechanical characteristics of Al
MMC manufactured in the lab. The investigation focuses on determining various
EDM process performance measures with the help of the Al MMC.The following are
the main objectives of the current investigation:
• To enhance the life of tool electrode which is one of the major constrictions in
achieving economic advantage
• To fabricate and characterize the specimens by studying microstructure
• To enhance the metal removal rate by incorporating gas assistance and powder

27
mixed dielectric
• To compare different process under the chosen conditions and suggest the
most suitable process
1.19. Summary of this chapter
This chapter provided a succinct overview of the background and
motivation for the current project. It described the current work's problem as it
examined the hybrid EDM process in the current scenario, when the machining of
hard materials is increasing rapidly, and the various consequences that come with it.
Various types of hybrid EDM processes were also discussed in this chapter.It also
include a brief introduction to composite materials, as well as a detailed discussion of
the current research main objectives.

29
CHAPTER 2
LITERATURE REVIEW
The year-by-year literature review is discussed in this chapter. The primary
goal of the literature review is to provide and emphasize the information and concerns
that are crucial to the current project. The following main categorizations were used to
conduct the literature review:
• EDM Process
• Composite material
2.1. EDM Process
Electrical discharge machining (EDM) is a machining technique that uses
thermo-electric spark discharge to erode electrically conductive materials by initiating
an abrupt spark discharge between the workpiece and the tool electrode. The distance
between the two electrodes is regulated between 0.01-0.50 mm during this machining
process. Pulses of direct current between the workpiece and tool electrode control the
arc discharge. Under the pulsed application of direct current, the dielectric fluid in the
electrode gap ionizes[1].
Electric discharge machining (EDM) is a non-conventional machining
technology that uses electro-thermal energy to machine a variety of materials with
complicated geometrical patterns and exact dimensional cuts. The EDM process is
notably well-known for producing difficult-to-machine materials. EDM technology
finds uses not just in the aerospace and automotive industries, but also in the surgical
and medical implant industries, by overcoming technical challenges connected with
traditional machining. EDM technology finds uses not just in the aerospace and
automotive industries, but also in the surgical and medical implant industries, by
overcoming technical challenges connected with traditional machining[2], [3].
Electrode wear ratio (EWR) and material removal rate (MRR) are important
performance indicators in EDM operations as shown in Figure 2.1, and eroded
particle flushing from the electrode gap is also important. Debris accumulation in the
machining zone, causes arcing and short circuit. Many techniques, such as EDM with
rotating tool electrode [4]–[6]. Vibro-rotary EDM [7], cryogenically cooled electrode

30
EDM [8], cryogenically cooled ultrasonic assisted electrode EDM [9], Magnetic field
assisted EDM with rotary tool [10] have been introduced by researchers to prevent the
occurrence of such problems and improve the flushing efficiency of the process.
[4]investigated the rotary EDM of Al2O3/6064Al composite with ball burnishing
electrode in the recent past. The results revealed that using an EDM with a ball
burnishing electrode resulted in a faster machining rate and a better surface finish.
Figure 2.1 Process of EDM[11]
The surface polish improved from 55 to 92 percent for a different set of
experimental factors. Surface polish may be compromised, however, due to the tool
electrode's high rpm or the presence of more Al2O3 reinforced particles. [5]looked
into the EDM of Al-SiC composites and looked at the impact of electrode revolution
and SiC reinforcement. They also looked at how polarity, discharge current, electrode
material, pulse duration, and electrode rotation affected responses such as MRR,
TWR, and surface finish. MRR rose with an increase in pulse current, regardless of
electrode materials, polarity, or SiC volume percentage, according to the findings.
Furthermore, MRR decreased when the pulse duration increased for a certain current.
Kuneida et al[12], [13]explored dry EDM method. They demonstrated that molten
workpiece material purged from the cutting gap without adhering to the electrode
surface. They claimed that oxidation of the electrode material increased the MRR
because oxygen in the air triggered an exothermic reaction, which increased the heat
input per spark and resulted in the creation of larger sized carter. Figure 2.2 depicts
the in detailed process of EDM.

31
Figure 2.2 Working principle of EDM
Yan et al [14] investigated how machining parameters affect the material
removal rate (MRR), surface roughness, and improvement ratio of surface roughness
(IRSR) on Al–Zn–Mg alloy, EDM and EBM are merged into a single process. A
micro hardness inspection and a corrosion resistance test are also carried out to assess
the impacts of the combined treatment on surface modification. Thus, a combination
procedure that achieves fine-finishing surface integrity while also having reinforced
effects on surface modification can minimize surface roughness without lowering
MRR. They decided to use a dependable CNC electric discharge machine with a
rotating spindle for milling. A pump cycled the dielectric, and some of the dielectric
and debris removed from the workpiece were sucked and released through the tool
electrode's central hole at 55 KPa.
The Taguchi approach was used by Yan et al[4] and explored the feasibility
and optimization of a rotary EDM with ball burnishing for examining the
machinability of Al2O3/6061Al composite. Following EDM, three ZrO2 balls placed
as extra components behind the electrode tool provide quick burnishing. To verify the
optimization of the machining procedure, three observable data are used: machining
rate, surface roughness, and improvement of surface roughness. The tool electrode is
designed as a Copper ring shaped B-EDM, as seen in Figure 2.3 This B-EDM method
aims for a higher machining rate as well as a finer surface roughness. Furthermore,
the B-EDM technique can obtain a machining rate that is nearly constant.
Saha et al [15] examined the dry EDM process with a tubular copper tool
electrode and a mild steel workpiece. The influence of gap voltage discharges current,

32
pulse-on duration, duty factor, air pressure, and spindle speed on MRR, surface
roughness (Ra), and TWR has been studied using air. Then, using a constructed
experiment based on the central composite design of experiments, empirical models
for MRR, Ra, and TWR were developed. The created models were used to conduct a
response surface analysis.
Figure 2.3 Design of copper ring tool shaped B-EDM [62]
The important parameters were identified using ANOVA testing. The
experimental result of the dry EDM connection is shown in Fig 2.4, and the flow
characteristic of air in the inter-electrode gap impacts the MRR and surface roughness
(Ra). There is an optimal number of airflow holes (in the tool) for which the MRR
and Ra are the highest.
Figure 2.4 experimental setup [62]
Although both methods are defined in geometry by the same concept of
intersection between the rotating tool and the Workpiece, Ding et al[16] worked on
CNC EDM machining of free-form surfaces that requires tool paths that are different
from those used in mechanical milling. Special tool path requirements for CNC EDM
rough milling with a cylindrical electrode are investigated, and a two-phase tool path
generation method for 4-axis CNC EDM rough milling with a cylindrical electrode is
devised. Figure 2.5 shows a solid model of the workpiece and the electrode interface.

33
In addition, compensation for discharge gap, electrode deterioration, and a variety of
other issues must be considered in the generation process of the tool path.
Figure 2.5 Solid models of workpiece and interference between work and tool [63]
The authors conducted research on the SKD-11 employing powders of Al, Cr,
Cu, and SiC suspended in a dielectric fluid. The effect of powder addition on the
creation of recast layers on the machined surface is shown in Figure 2.6. The
thickness of the recast layer formed on the material is reduced when powders are
present. Furthermore, when Al powder was added to the fluid for machining micro
size slits on Ti alloy, the depth of material removal increased. On the other hand, as
demonstrated in Fig. 2.6, it results in higher overcut on machined surfaces.
Figure 2.6 Effect of current and powders on machined surface characteristics recast
layer formed at without powder (b) recast layer formed at AL powder [63]
Chow et al [64] by reducing the discharging current and introducing a new
driven mechanism with a horizontal rotating electrode, a modified EDM was
developed. Titanium alloy is machined using micro-slit as shown in Figure 2.7 EDM
with various dielectric fluids using a thin copper diskette electrode. Kerosene,
kerosene with aluminum powder, and kerosene with SiC powder are the dielectric
fluids used in this study. The various fluids used during the machining process have a
variety of effects. The material removal depth, the electrode wear rate, the slit
expansion, the surface roughness, and the waveform of the discharging condition can
all be examined more closely to account for such effects.

34
Hosni et al [17] investigated the machinability of AISI D2 steel using a Cr
powder mixed EDM technique with the goal of improving the surface topography The
findings of the study look at the formation of a better-machined surface using the
PMEDM technique, as well as a 50 percent reduction in the recast layer thickness
when Cr powder is present Figure 2.8 depicts the effect of micro-scale Cr powder
mixed with the dielectric medium on the recast layer formation, whereas Figure 2.9
depicts the effect of micro-scale Cr powder mixed with the dielectric medium on the
recast layer formation. The effect of Nano powder is seen. The smaller the particle
size of Cr powder, the less recast layer forms on the machined surface.
Figure 2.7 Micro slit made with (a) kerosene (b) Al + kerosene medium[18]

35
Figure 2.8. Influence of micro-Cr powder addition on recast layer formation [34]
Figure 2.9 Effect of Nano powder addition on the recast layer formation [34]
In 1995[19], Armani and Cassidenti, NASA presented a short technical paper
on the use of gas based EDM.As dielectric for boiling a pit through tubular copper
electrodes, Argon or helium gas as shown in Figure 2.10[13].Nevertheless, proposed

36
in 1997 a known new machining process gas like EDM. They proposed reducing
pollution through the use of dielectric gas instead of kerosene. It was subsequently
studied as an advancement method by Kuneida et al [12] .
New method for energy distribution and plasma diameter determination is
proposed by Zhang et al. The authors compared the boundary of the melted material
in a crater obtained through the metallographic method and that obtained from the
thermal-physical surface. The boundary of the melted material has been calculated
using the finite element method using the thermal/physical model. This method has
been used to measure power and plasma diameter distributions in different dielectrics
with different polarities in experimentally molded steel 8407.
Figure 2.10 The principle of dry EDM [65]
The section view of the craters that are obtained by means of various dielectrics and
polarities is shown in Figure 2.11[20]
Figure 2. 11. Comparison of the section view of the craters obtained using different
dielectrics and polarities [66]

37
Multiple modeling and simulation techniques for the optimal environment of
the EDM process were presented. Wang et al[21] proposed a 3D flow field model for
the machining gap in EDM, including liquid, natural gas and solid phases. In
consecutive pulse discharges, the model analyzed mechanisms of debris and bubble
mobility in the machining gap. The results of the testing and simulation model
showed that it was feasible to use the proposed model. The main path through which
the waste is excluded from the machining gap is a lot of waste moving outside the
machining gap following the excluded bubbles. With increased discharge current and
pulse-on-time the bubble expansion strengthened. Figure 2.12 illustrates bubble and
debris movement simulation and observation experimental results.
Figure 2.12. (a) Simulation Results (b) Experimental results of the bubble and debris
movement [67]
The simulation and model of the EDM process was also introduced by
Izquierdo et al[22]. In the workpiece, the temperature fields generated by the
superimposition of multiple discharges were calculated by means of a finite difference
scheme. The discharge characteristics for a particular operation, i.e., energy
transferred to the workpiece, discharge channel diameter and material removal
efficiently, were assessed using the results of the numerical model to be reversed
identified. As Figure 2.13 illustrates, the authors reported a change in the volume of
material removed by release.
In order to study the effects on the machining parameters such as peak current
and pulse-on life, SR, average white layer and surface crack density of M2 die
machining steel machined with the EDM process, Bhattacharyya et al[23]developed a
comprehensive mathematical model based on RSM. The author reported that the
minimum SR has been achieved for low peak current and pulse-on duration, i.e., for 2
A and 20 us. By keeping the maximum current as low as possible (preferably 2-5 A)
and maintaining pulse-on durations within a range of 163-510 μs, the average white

38
layer thickness can be minimized. The medium value and the minimum pulse-on time
of the peak current were also found to minimize the surface crack density. Finally, the
optimal combinations for minimum ruggedness of the surface, white layer thickness
and surface have been found the crack density was 2 A/20 μs, 2 A/20 μs and 9 A/20
μs.
Figure 2.13. Variation of volume of material removed per discharge as the operation
progresses [68]
With the abiding evolution of the material processing technologies and
enrichment in the requirement of the complex geometry and inflated properties of the
top layer, conventional EDM process is deficient to encounter the pre requisites of the
existing machining industries. To ameliorate the process, it has been incorporated
with various types of assistance. Strategies followed by numerous researchers to boost
the performance of EDM process
• Machining with different tool materials, different dielectric with mixed additives.
• Ultrasonic vibration assisted EDM
• Magnetic field assisted EDM
• Gas assisted EDM
• Powder mixed EDM
Singh et al [24] investigated the influence of passing compressed air through
the perforated electrode on the workability of EDM process. He analyzed the effect of
process variables on the MRR and TWR. The compressed air is disbursed through the
perforated copper electrode. The exothermic reaction between the liquefied metal and
the concentration of oxygen in the air results in an additional amount of heat.
Formation of the recast layer and an increased size of the crater pans out in an

39
increased metal removal rate in comparison to the material removal rate observed for
rotary EDM process.
Li et al [25] enquires about the effect of M2 grade high speed steel
W6Mo5Cr4V2 with the utilization of cold nitrogen-air mixed gas during machining.
He observed that above -80˚C the metal removal rate remains unaltered and below -
80˚C the inclination of electrode wear rate tends to become flat and at 80˚C lots of
cracks were seen. Singh et al[26]studied the effect of compressed air and argon gas
passing through the tool electrode on the performance of the EDM process. As an
after affect MRR was increased more for air assisted EDM, SR and EWR was
reduced for argon assisted EDM.
Lin et al [27]analyzed the hybrid process of electrical discharge machining in
gas merged with ultrasonic vibrations and abrasive jet machining. He obtained
enhanced MRR and oxidation was prevented during the process because of the argon
gas selected as the inert gas and as a consequence reduced EWR and superior SR was
observed. Beravala et al [28]concentrates to modify the EDM process by assimilating
the assistance of magnetic field in addition to liquid plus gaseous dielectric together
and founds an enhancement by 21-41% of MRR, 7-14% of the EWR of the air
assisted EDM and an enhancement by 10-18% of MRR and tripping by 7-16% of
EWR of magnetic field-argon gas assisted EDM. The presence of magnetic field helps
in diminishing of the unwanted particles and the liquid gaseous dielectric assisted in
trouncing the cracks formation.
Figure 2.14: Principle of the powder mixed EDM process [72]

40
Yadav et al [29]focuses to intensify the execution of the rotary tool near dry
electrical discharge machining process by including oxygen gas along with the
dielectric medium. He observed an increment in MRR for both dry and wet conditions
with addition of oxygen. With the increase in the oxygen amount the HOC also
increases. Syed et al [30] observed the effects of aluminum powder in distilled water
as a dielectric fluid. W300 die steel and electrolytic copper was used for the work and
tool electrodes, respectively. The process parameters are pulse peak current, pulse on-
time, and Al powder concentration as shown in Figure 2.15. The white layer thickness
is taken into account as the output response (WLT). Face centered central composite
design procedure is used to plan the experiments. To study the effect of process
parameters, an empirical model is developed for WLT using response surface
methodology (RSM). Optical microscopy results show that a low white-layer
thickness of 17.14 m is obtained at a high powder concentration of 4 g/l and a low
peak current of the value of 6 Ampere.
Figure 2.14: Graph showing variation of MRR with respect to powder size
Joshi etal.[31]Introduced a process to improve the machinability of
conventional DEDM magnet-assisted dry EDM (MADEDM) process Figure 2.15
illustrates the mechanism of the MADEDM process. In this work, the magnetic field
was redundantly connected to the electrical field to increase the electric development
and ionization phase of the plasma. In order to improve MRR in the DEDM process,
the utilization of the magnetic field has been found to affect a greater transfer of
thermal energy into the work pieces. Results show that MRR increases by 130 percent
by the use of magnetic field, and around zero TWR are achieved without the influence
of magnetic field compared to DEDM. Microscopy of the scanning electron (SEM)
was associated to surface finishing upgrades

41
Figure 2.15. Mechanism of electromagnetic field application in DEDM[31]
Liquing et al. [32] proposed new DEDM systems, which were designed to
expand MRR and the surface integrity with oxygen blended DEDM and DEDM with
cryogenically refreshed work pieces. The results showed that both the oxygen mixed
EDM and cryogenically cooled process of the workpiece were improved by MRR.
The surface finish was found to be better when a cryogenic cooled piece occurred, the
process can be seen in Figure 2.17.Air-mixed oxygen has a high MRR in any case.
The MRR was also observed as the oxygen content in the mixture increases.
(a) (b)
Figure 2.17. Surface morphology comparison of with and without cryogenically
cooled work pieces. (a) Without cryogenically cooled workpiece. (b) With the
cryogenically cooled workpiece [76]
Palanikumar et al[33]performed machining of Al/ Sic composites by varying
the factors like cutting speed, depth of cut, etc.., The machining experiments were
conducted using the experimental method of analysis. ANOVA technique was
followed on this investigation and the results plotted on the different graphs shows
that Al/SiC has good properties to withstand high strength and toughness than the
unreinforced one.

42
Hung et al [34]revealed in their investigation the usefulness of applying EDM
operation for silicon carbide particles reinforced cast aluminum metal matrix
composite. Analytical models of the process were also developed to forecast the effect
of process parameters on process responses such as metal removal rate, re-cast layer,
and surface finish. In their research, it was seen that the presence of SiC particles
reduces the MRR. The reason behind it's that silicon carbide (SiC) particles act as a
shielding medium for the aluminum matrix. The unmelted SiC particles withdraw
together with the surrounding molten aluminum droplets from the composite material.
While some aluminum droplets are flushed through the dielectric fluid and others trap
the loosened SiC particles which re-solidify onto the surface of composite material
then produce a re-cast layer (RCL). The input power and current mainly controlled the
MRR and thickness of the recast layer and responsible for the surface finish of the
workpiece
Ramulu et al [35] has been done their investigation for machinability of 15
vol.% and 25 vol. % SiC whisker/2124 aluminum matrix (SiCw/Al) composites. They
cut the material samples at coarse, medium, and conditions by using copper and brass
tools. The experiment revealed that the material removal rate increases proportionally
by increasing the power of the electrode and MRR for 15 vol. % SiCw/2124 Al
composites are more than the 25 vol. % SiCw/2124 Al composites. The copper
electrode gives a 5 to 10% more material removal rate in comparison to the brass
electrode. Machining time is seen to be higher in 25 vol. % SiCw/Al than 15%
SiCw/Al composite. It was also seen that higher cutting speed produces micro-
damage in the surface and sub-surface area.
Mohan et al[36]investigated the machining of Al-SiC composite by using
electro-discharge machining. The main aim of this research was to evaluate the effect
of process parameters, the volume percentage of SiC particles, and electrode material
on the machining performances. The process parameter which is considered in their
experiment is electrode polarity, pulse duration (pulse on time, pulse off time)
discharge current, and electrode rotation. Al- 20% SIC and Al- 25 % SiC composites
are taken as a workpiece sample and copper and brass are selected as a tool material
for the experiment. The finding of the study revealed that the material removal rate
(MRR) is more with positive polarity and increases with an increase in current. The
MRR was found to be more with the brass electrode (tool) as compared to the copper
electrode (tool). Increasing either the volume % of SiC particles in aluminum metal

43
matrix composite (AMMC) or pulse duration decreases the material removal rate and
the material removal rate increases with the increase of rotational speed of the
electrode. When the volume % of SiC particles in the AMMC is less, then the tool
wear rate will be less, and the tool wear rate becomes more when the pulse current is
more. On the decrease in the pulse current, the surface roughness value becomes less
and it becomes high with the increase of volume % of SiC particles in the aluminum
metal matrix composite (AMMC). The research optimized the process parameter for
different electrodes and volume % of SiC particles in the AMMC for achieving a
maximum material removal rate.
Uriarte et al[37]gathered information and analyzed micro fabrication
technologies for different tool-insert materials and features. It is realized that the non-
contact machining technique with split tenth accuracy has been continuously evolving
from a mere tool-room machine to a micro-scale application machining alternative. It
is no wonder that it attracts a significant amount of research interests. Many
researchers have evolved different designs of tools, different types of dielectric fluids
(ranging from water, kerosene, special property oils, air, gases, the mist of fluids,
etc.), various process parameters, a variety of mutual movements of tool-workpiece,
mixing of some conductive and non-conductive powders and so on. Most of them
were evolved for catering special materials, increasing MRR, decreasing percentage
Tool Wear Rate (TWR), achieving better surface properties and accuracy, considering
environmental safety, etc.
2.2. Composites
Mechanical stir casting was used by Hanizam et al [38]to make MWCNT-
CNT, which was then thixoformed and thermally treated with T6 (MT6). As a result,
using a robust design of experiment (DOE), namely the Taguchi technique, with two
factorial levels, the optimization and effect of variables such as the amount of CNT,
amount of wetability agent of Mg, and mechanical stirring duration were explored.
The response variables were the signal-to-noise (S/N) ratio (‘larger is better),
hardness, and ultimate tensile strength (UTS). The nanocomposites exposed to DOE
run 4 and containing 0.5 wt. percent MWCNT, 0.5 wt. percent Mg and 10 minutes of
mechanical stirring yielded the best hardness and UTS values of 106.4 HV and 277.0
MPa, respectively. When compared to the as-cast A356 alloy, the hardness (76.3%)
and UTS (108.4%) both improved. The alteration of the as-cast microstructures and

44
porosity after thixoforming and MT6 treatment was also studied. The optimized
mechanical stir casting parameters for MWCNTA356 production, as well as the
improved mechanical properties acquired by thixoforming and heat treatment, were
demonstrated in this study.
Kok et al [39] introduced vortex technique and subsequent applied pressure
were used to create 2024 aluminum alloy metal matrix composites (MMCs)
reinforced with three various sizes and weight fractions of Al2O3 particles up to 30 wt.
percent as shown in Figure 2.18. The effects of Al2O3 particle content and particle size
on composite mechanical parameters like hardness and tensile strength were
examined. The samples had low porosity, according to the density measurements, and
the quantity of porosity in the composites rose as the weight percentage and particle
size decreased. SEM microscopy of the microstructures revealed that the dispersion of
coarser particle sizes was more uniform, whereas finer particles resulted in
agglomeration of the particles and porosity. The hardness and tensile strength of the
composites rose with decreasing particle size and rising weight proportion of
particles, according to the findings.
Figure. 2.18. Schematic diagram of the experimental apparatus for producing the
MMCs [83]

45
The advanced combinations of aluminum alloy composites currently being
used for by Joel et al [40]various applications are summarized in Table 2.1.
Composites of this kind of metal matrix (MMC) are similar to conventional metal
processing, and their phenomenon is shown in the Figure 2.19 Massive wear of the
cutting tool will occur during processing of MMCs (both in coated and uncoated). The
principal wear is because of the abrasion, by sliding motion of the particles in relation
to the clearance face of the enhancement material on the cutting edge of the matrix.
The tool wear, namely micromachining, micro cutting, micro-ploughing at the cutting
edge of BC and fracture at the plane DC is responsible for multiple wear mechanisms.
Figure. 2.19 Machining of Metal Matrix [84]
Table 2.1 Advanced aluminum alloy composite combinations and its applications [84]
Composition Properties Application Reference
Al A356 + 4 wt% nano Al2O3
(stir casting)
Compressive strength
(630.5 MPa)
Automotive, aerospace
and electrical industries
[32]
Al A356 + 10 % wtSiC + 1%
wt graphite (compocasting)
Yield strength (170Mpa),
Modulus of elasticity (GPa
81.2)
Spacecraft [33]
AI – Cu (4.5 wt% Cu), Al –
Cu/SiCp (squeeze casting)
Hardness (139BHN) UTS
(239 MPa)
Engine piston and heat
sink
[34]
Al A356 + 0 5 vol% micro
TiB2(stir casting)
UTS – (308MPa)
Drum brake material [35]
Al 6061 + 10wt% Si3N4 (stir
casting)
87.048 VHN, UTS-201
MPa
Magneto Parts,
appliance fittings
[36]
2009 Al + (1wt% CNT + 3wt%
CNT) (1-pass FSP) (Friction
stir processing)
UTS – (477MPa)
Automotive and
aerospace applications
[37]
AI 2021 + (5wt% Gr + 20wt%
SiC) (Powder metallurgy)
Density (2.94 g/cm3
),
Hardness (63BHN)
Spacecraft and antenna
dish
[38]
Al 7075, Ai 7075 + 7wt% SiC
+ 3wt% Gr (Stir casting)
Density (2.81 g/cm3
, 2.784
g/cm3
), Hardness (175 Hv,
219 Hv)
Electrical signal
transmission
[39]
Al 6061 + (20wt% Ainp) (Stir
Casting)
UTS – (241 MPa)
Microhardness (91 VHN)
Microelectronic devices [40]
Al 6082 + (24 wt5 TiC) Microhardness (149 VHN), High temperature [41]

46
(Friction Stir Processing) UTS – (382 MPa) applications
Al 6061 – T6 + (8vol % SiC +
4vol% Gr) (900 rpm) (Friction
Stir Processing)
UTS – (219 MPa), Yield
Strength (185MPa)
Automobile
components
[42]
Al 7009 + (25wt% SiCp) (as
cast)
Hardness (198 Hv) Land-based systems in
military
[43]
Li and Lee et al [41] [42] investigated that for the reinforced composites
represented in Figure 2.20, the intensity of strain hardening is higher than its
monolithic intensity.Furthermore, volume fractions of the added particles are
dependent on the form of the particles.
Fig2.20 Composite Material [85]
And studied the composite operating parameter to determine its properties.
The second objective is to create PAMC with a variety of compositions of graphite
strengthening particles, Al2O3 and SiC using the stir casting method. The second
objective is to produce PAMC with a stir casting technique. They concluded that
• The angle of the blade should be 45° or 60° for the consistent dispersion; the
blade should not be 4.
• We must continue to function for good weight ability Semi-solid stage
temperature, i.e., Al 630 (6061). At Condition of full liquid Uniform
distribution is hard to achieve of the molten metal strengthening.
• Mold preheating helps also to reduce porosity.
Bhandari and Ravi et al[43][44] evaluated mechanical properties for the
AA6061/B4C composites made by stir cast route with a different weight and
microstructure percentage. The following findings are derived from this study-
• The Stir Casting Technique could be used to manufacture the homogenous
AA6061/B4C composite.

47
• The optical metallographic study revealed a homogeneous dispersion of the
B4C particle in the composite.
• Increased the grain size of the matrix for adding B4C reinforcement part as
shown in Figure 2.21.
• Incremental compound weight percentage of B4C particles increased to 68HV
from 62 HV.
• B4C reinforcement improved the traction strength from 117 MPa to 145 MPa
of Aluminum Matrix Composites (AMCs).
Figure 2.21a) AA6061 without reinforcement b) AA6061 matrix with 5% B4C c)
AA6061 matrix with 10% B4C [87]
Suraya et al [45] studied to find the ability of EDM process on machining
responses of aluminum alloys LM6 (Al-Sil2) and Table 2.2 depicts the mechanical
properties of Al alloy. And the mechanical properties as analyzed during the research
is shown in the Table below.
Table 2.2 Mechanical properties of LM6 [2]
Quantity Value Unit
Tensile strength, Ultimate 290 MPa
Tensile strength, Yield 131 MPa
Elongation 3.5 %
Poison’s ration 0.33 -
Fatigue strength 130 MPa
Machinability 30 -
Shear strength 170 MPa
The machining parameter relationships such as pulse-on-time, pulsation-off
time, peak current and voltage are determined on the machining characteristics of
MRR, EWR and Ra. The main factor that affected MRR, EWR and Ra were peak
current may be concluded. With the current increasing, the MRR and EWR are
increased and Ra is reduced. Other factors like voltage, pulse on time and pulse off

48
time have less influence on reactions. The percentage of the contribution value shows
that peak current has the greatest value among others. [46]evaluated effect of the
process variables on the machining characteristics of the 20 wt percent composite
Al2O3/AA2014 electrical discharge machinery was investigated by a different one-
parameter approach as illustrated in Figure 2.22. The composite was manufactured by
casting. Pulse current, discharge voltage, pulse on time and pulse off are considered
process variables time. Process features include removal of materials, wear rate of
tools and surface Ruggedness is examined. The uniform distribution of optical
microscopy test Al2O3aluminum alloy enhancement in the 2014 matrix phase. Results
show MRR, TWR and SR are increased with current and pulse increases on time.
Figure 2.22. Die-sinker EDM with external circulation system [90]
Khajuria et al [47] studied the impacts of weight variation of ceramic Al2O3
particles in stir cast stir composites AA2014 during electrical discharge machining
(EDM). To analyses effects of weight variation percentage of the stir cast AA2014
composites of ceramic Al2O3 particulates in the process of electro deal machining.
Observed that at the expense of TWR, MRR and SR have decreased with an increase
in the ceramic particle weight percentage. The result is an enhanced micro hardiness
of composites with reinforced stir cast. However, micro hardiness of EDMed samples
reduced by 58,34, 52,25 and 46,85 ppm for stir cast AA 2014, by 10 percent
Al2O3/AA 2014, and by 20 percent Al2O3/AA 2014, with a fixed machining parameter
value, that is 9 amp current, 60 V voltage, 90 ms pulse off time and 90 ms pulse on
time. The ceramic Al2O3 particulate thermal scale of 20Wt. percent Al2O3/AA2014
composite as illustrated in Figure 2.23 has been found to have been analyzed by SEM
and quantitative energy dispersive spectroscopy (EDS).

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