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TRIBO-CORROSION BEHAVIOR OF TiC COATED AISI
4340 STEEL IN JATROPHA CURCAS BIODIESEL
BY
BELAL AHMED GHAZAL
A dissertation submitted in fulfilment of the requirement for
the degree of Master of Science in Manufacturing and
Material Engineering
Kulliyyah of Engineering
International Islamic University Malaysia
JANUARY 2014
ii
ABSTRACT
There is an increasing demand for hard coatings which possesses a combination of
different functional properties such as high wear and corrosion resistance. In this work
Fe-TiC composite coating was synthesized by preplacement of 1 mg/mm2 of TiC
particulate and melting it using a conventional TIG torch arc heat source. Four melt
tracks were glazed on the surface of the AISI 4340 steel at energy input varied
between 1176 J/mm to 1680 J/mm in argon gas environment. A hemispherical
composite layer with a thickness of 1 mm was successfully obtained. The melt tracks
at 1176 J/mm have microstructure that consists of semi-melted TiC particulate. While
melt tracks processed at higher energy inputs showed formation of TiC dendritic
structure. The composite coating processed at 1344 J/mm developed maximum
hardness of 1000 Hv. The coating hardness was found to be strongly dependent on the
density of TiC dendrites that segregates at the top of the melt pool. The tribological
behaviour of surface modified AISI 4340 steel was performed using CSM pin-on-disc
tribometer at room temperature under both dry sliding and jatropha curcas biodiesel
lubricated conditions. The electrochemical corrosion test of AISI 4340 steel was
conducted using a computer controlled Autolab potentiostat under jatropha curcas
biodiesel electrolyte. The room temperature tribological properties of the composite
coated AISI 4340 steel has a maximum wear volume of 0.165 mm3 while AISI 4340
steel has a maximum wear volume of 3.67 mm3. The composite coated steel exhibited
20 times lower volume loss compared to alloy steel due to complex geometry of the
solidified TiC dendrites that strongly bonded to the Fe-based alloy. The micrograph of
the worn surfaces of coated steel showed smoother wear scar while low alloy steel
substrate underwent sever plastic deformation and abrasive wear. Incorporation of TiC
adversely increases the friction coefficient of TiC composite coated steel compared to
alloy steel due to the formation of oxide layer. The composite coating exhibits
approximately twice lower wear volume of 0.035 mm3 in comparing to alloy steel
with wear volume of 0.062 mm3 at 10N load and 400 sliding speed. The composite
coated steel showed compatible friction coefficient compared to low alloy steel under
lubricated condition with an average coefficient of friction of 0.07 to 0.11. The
micrograph of the worn surface showed pitting and corrosive type of wear for steel
substrate while the composite coating showed smoother wear scars with mild
oxidation products located near to the TiC interface with the matrix. The
electrochemical behaviour in presence of jatropha biodiesel based on the polarization
curves showed that incorporation of TiC into the steel surface reduced the corrosion
current density because of the fair electrical conductivity of TiC to the electric current
in biodiesel electrolyte. Conclusively, Fe-TiC composite coating successfully
improved the Tribo-corrosion resistance of the AISI 4340 steel in the presence of
biodiesel.
iii
.
iv
APPROVAL PAGE
I certify that I have supervised and read this study and that in my opinion, it conforms
to acceptable standards of scholarly presentation and fully adequate, in scope and
quality, as a dissertation for the degree of Master of Science (Material Engineering).
……………………………………..
Md Abdul Maleque
Supervisor
I certify that I have read this study and that in my opinion, it conforms to acceptable
standards of scholarly presentation and is fully adequate, in scope and quality, as a
dissertation for the degree of Master of Science (Material Engineering).
……………………………………..
Suryanto
Examiner (Internal)
I certify that I have read this study and that in my opinion, it conforms to acceptable
standards of scholarly presentation and is fully adequate, in scope and quality, as a
dissertation for the degree of Master of Science (Material Engineering).
……………………………………..
Wan Mohd Norsani Wan Nik
Examiner (External)
This dissertation was submitted to the Department of Manufacturing and Material
Engineering and is accepted as a fulfilment of the requirement for the degree of
Master of Science (Material Engineering).
……………………………………..
Mohammad Yeakub Ali
Head of Department of
Manufacturing and Material
Engineering
This dissertation was submitted to the Kulliyyah of Engineering and is accepted as a
fulfilment of the requirement for the degree of Master of Science (Material
Engineering).
……………………………………..
Md Noor bin Salleh
Dean Kulliyyah of Engineering
v
DECLARATION
I hereby declare that this dissertation is the result of my own investigation, except
where otherwise stated. I also declare that it has not been previously or concurrently
submitted as a whole for any degrees at IIUM or other institutions.
Belal Ahmed Ghazal
Signature………………….. Date……………………
vi
INTERNATIONAL ISLAMIC UNIVERSITY MALAYSIA
DECLARATION OF COPYRIGHT AND AFFIRMATION
OF FAIR USE OF UNPUBLISHED RESEARCH
Copyright © 2014 by International Islamic University Malaysia. All rights reserved.
TRIBO-CORROSION BEHAVIOR OF TiC COATED AISI 4340
STEEL IN JATROPHA CURCAS BIODIESEL
No part of this unpublished research may be reproduced, stored in a retrieval system,
or transmitted, in any form or by means, electronic, mechanical, photocopying,
recording or otherwise without prior written permission of the copyright holder except
as provided below.
1. Any material contained in or derived from this unpublished research may only
be used by others in their writing with due acknowledgment.
2. IIUM or its library will have the right to make and transmit copies (print or
electronic) for institutional and academic purposes.
3. The IIUM library will have the right to make, store in a retrieval system and
supply copies of this unpublished research if requested by other universities
and research libraries.
Affirmed by Belal Ahmed Ghazal
………………………. …………………..
Signature Date
vii
To my Beloved Parents
viii
ACKNOWLEDGMENTS
My sincere gratitude goes to Allah (SWT), the Almighty, the Almighty for His
inspiration and guidance throughout my research work. May He accept our efforts as
act of worship.
My heartfelt appreciation goes to my supervisor Associate Professor Dr. MD
Abdul Maleque for his positive guidance, critical assessment and suggestions
throughout my research work. It is a special privilege to work and associate with him
because of his motivational inspiration that supports during my research. He has really
equipped me with a decent understanding in developing my research skills. I also
reserve my appreciation to my co-supervisor Professor Dr. Mohamed Yeakup Ali for
his attention, supports and guidance in completing my thesis work. I also would like to
express my gratitude to the center of ionic liquids (UMCiL) department of Chemical
Engineering of University of Malaya specifically for Dr. Maan Hayyan Al Razzouq,
Adeeb Hayyan Al-Razzouq and Dr. Mohammed Al-Saadi for their technical support
and field supervision.
My profound gratitude also goes to my jewel inestimable value, my parents
Ahmed Mohamed Ghazal and Hanan Hosni Ghazal who gave their never ending
support, encouragement, love and care required to make my research a reality.. Not to
forget to my sister Hannaa and her daughter Shahad and mahmood mazen ghazal who
always believe in me. My sincere gratitude also goes for my brothers Mohamed and
Anas for endless love and trust they gave me. May Allah (SWT) reward you all
abundantly
Special thanks also goes for thank the Ministry of Higher Education for the
financial support through project No: ERGS12-021-0021.
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TABLE OF CONTENTS
Abstract ................................................................................................................... ii
Arabic Abstract ....................................................................................................... iii
Approval Page ......................................................................................................... iv
Declaration .............................................................................................................. v
Copyright Page ........................................................................................................ vi
Dedication ............................................................................................................... vii
Acknowledgments ................................................................................................... viii
List of Tables .......................................................................................................... xi
List of Figures ......................................................................................................... xii
CHAPTER ONE: INTRODUCTION ................................................................. 1 1.1 Background ............................................................................................ 1
1.2 Problem Statement and Its Significance ................................................ 3 1.3 Research Objectives ............................................................................... 5 1.4 Research Scope ...................................................................................... 5 1.5 Research Methodology ........................................................................... 6
1.6 Thesis Organization ............................................................................... 8
CHAPTER TWO: LITERATURE REVIEW .................................................... 10 2.1 Introduction ............................................................................................ 10 2.2 Biodiesel ................................................................................................. 10
2.2.1 Sources of Biodiesel ..................................................................... 12
2.2.2 Characteristics of Biodiesel.......................................................... 13 2.3 Tribological Behaviour of Biodiesel ...................................................... 15 2.4 Aspects of Tribocorrosion ...................................................................... 17
2.5 Corrosion Behaviour of Biodiesel .......................................................... 18 2.6 Tribocorrosion Prevention ..................................................................... 23
2.7 Techniques of Producing Hard Coating ................................................. 24 2.7.1 Molten or Semi-Molten State Surface Coating Techniques ........ 25
2.7.1.1 Hardsurfacing Techniques ................................................. 26 2.7.1.2 Laser Surface Melting Technique ...................................... 28 2.7.1.3 Plasma Spraying ................................................................. 29 2.7.1.4 TIG Welding Surface Melting Technique ......................... 30
2.8 Research on Composite Coatings ........................................................... 31
2.9 Summary ................................................................................................ 41
CHAPTER THREE: EXPERIMENTAL DETAILS ........................................ 43 3.1 Introduction ............................................................................................ 43 3.2 Materials ................................................................................................. 43 3.3 Equipment .............................................................................................. 44 3.4 Synthesis of Jatropha Curcas Biodiesel ................................................. 45
3.4.1 Chemicals for Biodiesel production ............................................. 46 3.4.2 Biodiesel Preparation ................................................................... 46
3.5 Composite Coating Using TIG Torch Technique .................................. 48
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3.5.1 Electrode ...................................................................................... 49
3.5.2 Shielding Gas ............................................................................... 50 3.5.3 Polarity ......................................................................................... 50
3.6 Procedure ................................................................................................ 51 3.6.1 Surface Preparation ...................................................................... 51 3.6.2 Powder Preplacement ................................................................... 52 3.6.3 TIG Torch Surface Melting Process ............................................ 52
3.7 Material Characterization ....................................................................... 54
3.8 Mechanical and Tribological Testing ..................................................... 54 3.8.1 Microhardness .............................................................................. 54 3.8.2 Wear Testing ................................................................................ 55 3.8.3 Lubricated wear testing ................................................................ 56
3.9 Corrosion Test Procedure ....................................................................... 57
3.9.1 Corrosion Cell Set-Up .................................................................. 57
3.10 Summary .............................................................................................. 58
CHAPTER FOUR: RESULTS AND DISCUSSION ......................................... 60 4.1 Introduction ............................................................................................ 60 4.2 Formation of Fe-TiC Composite Coating .............................................. 60
4.2.1 Topography of Fe-TiC Composite Coating ................................. 60 4.2.2 Melt Pool Size .............................................................................. 61
4.2.3 Microstructure and Melt Pool Configuration ............................... 63 4.3 Hardness of Fe-TiC Composite Coating ................................................ 67 4.4 Tribological Behaviour of Fe-TiC Composite Coating ......................... 70
4.4.1 Dry Wear of Fe-TiC Composite Coating ..................................... 70 4.4.1.1 Effect of TiC Reinforcement on Wear Volume ................. 70
4.4.1.2 Effect of Variable Sliding Speed on Wear Volume ........... 71
4.4.1.3 Effect of Applied Load on Wear Volume .......................... 71
4.4.1.4 Effect of Dry Sliding Conditions on Friction Coefficient.. 75 4.4.2 Biodiesel Lubricated Wear Behaviour ......................................... 78
4.4.2.1 Influence of Applied Load on Wear Volume..................... 79
4.4.2.2 Effect of Applied Load on Coefficient of Friction ............ 81
4.5 Electrochemical Corrosion of Fe-TiC Coating ...................................... 85 4.5.1 Effect of Temperature on Corrosion Current Density.................. 88
4.6 Summary ................................................................................................ 91
CHAPTER FIVE: CONCLUSIONS AND RECOMMENDATION ............... 92 5.1 Conclusion .............................................................................................. 92 5.2 Recommendations .................................................................................. 93
BIBLIOGRAPHY
.................................................................................................................................. Error
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LIST OF TABLES
Table No. Page No.
2.1 Common fatty acids present in biodiesel (Hayyan et al., 2012) 11
2.2 Distribution of common fatty acids in common biodiesel
(Lin et al., 2011) 12
2.3 Biodiesel specifications -ASTM-D-6751-06 (Atadashi et al., 2010) 14
2.4 Physiochemical properties of common feed stocks of biodiesel
(Atadashi et al., 2010) 15
3.1 Sources of the Raw Materials 44
3.2 Chemical composition of the substrate steel (wt %) (Mridha et al., 2011) 44
3.3 Chemical compositions of the free fatty acids in JCO
(BIONAS Sdn Bhd) 45
3.4 Physiochemical properties of JCO vs. conventional diesel oil 46
3.5 Physical properties of argon shielding gas used in surface modification
of AISI 4340 steel (Kou, 2003) 50
3.6 Operating conditions and variables for TIG melting process 54
4.1 Melt track’s dimensions at different processing conditions 62
4.2 Ecorr and Icorr values of the studied alloys derived from the polarization
curves 87
4.3 Ecorr and Icorr values of the studied materials derived from the
polarization curves 90
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LIST OF FIGURES
Figure No. Page No.
1.1 Flow chart of the research process 7
2.1 Transesterification processesof converting triglycerides into biodiesel
(Lin et al., 2011) 11
2.2 General classification of surface coating methods (Holmberg &
Matthews, 1994) 25
2.3 Laser surface modification process 29
2.4 Schematic diagram of the plasma spraying process (Holmberg &
Matthews, 1994) 30
2.5 Schematic diagram of TIG torch surface melting technique (Buytoz &
Ulutan, 2006) 31
3.1 Block diagram of the biodiesel production process 48
3.2 Jatropha biodiesel after transesterification treatment of the oil 48
3.3 Schematic diagram of the tungsten inert gas (TIG) torch technique
(kuo, 2003) 49
3.4 Schematic diagram of the common polarities used in TIG torch surface
modification (Kou, 2003). 51
3.5 TIG welding torch used for surface modification of AISI 4340 steel 53
3.6 Schematic diagram of pin-on-disk tribometer 56
3.7 Design of the lubricated bath 56
3.8 Schematic diagram of Corrosion cell setup 58
4.1 Surface topography of the melt tracks produced at (a) 1176 J/mm, (b)
1344 J/mm, (c) 1512 J/mm, and (d) 1680 J/mm at 20x 61
4.2 Micrograph of the melt track produced at 1344 J/mm 62
4.3 Optical micrograph of the melt tracks processed at 1176 J/mm showing
(a) the hemispherical melt track at 20x and (b) semi-melted TiC
particultes in the resolidified melt pool at 200x magnification 64
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4.4 optical Micrograph of Hemispherical melt pool of the track processed at
1433J/mm showing (a) dendritic and (b) semi molten TiC precipitated
particulates at 200x 65
4.5 Common precipitated TiC morphology for tracks processed at energy
input (a) 1176 J/mm (b) 1344 J/mm (c) 1512 J/mm, and (d) 1680 J/mm 66
4.6 SEM Micrograph showing the Dendrite TiC at 1344 J/mm 67
4.7 EDX of the TiC solidified particulate at 1344 J/mm 67
4.8 Microhardness profile of the processed tracks across the depth of the
melt pool 68
4.9 Wear volume loss for different applied load: (a) 5 N, (b)7 N, and (c) 10
N at different sliding speeds 72
4.10 Micrograph of the wear worn surface for (a) AISI 4340 and (b) Fe-TiC
composite coating processed at 1344 J/mm heat input and subjected to
(10 N applied load and 400 RPM sliding speed) 73
4.11 Two dimensional tracks of the worn tracks for (a) AISI 4340 steel (b)
Fe-TiC composite coating subjected to (10 N applied load and 400
RPM sliding speed) 75
4.12 Effect of applied load on the friction coefficient: (a) 5N, (b) 7N, and (c)
10N at different sliding speed 77
4.13 Wear volume loss of AISI 4340 steel at biodiesel lubricated condition. 80
4.14 Wear volume loss of Fe-TiC composite coated steel under biodiesel
lubricated condition 80
4.15 Effect of applied load on the coefficient of friction of Fe-TiC composite
under lubricated condition 81
4.16 Effect of applied load on the coefficient of friction of AISI 4340 steel
under biodiesel lubricated condition 82
4.17 Micrograph and EDX analysis of the worn surfaces after exposure to
biodiesel at 10 N applied load and 400 RPM sliding speed for (a) AISI
4340 steel and (b) Fe-TiC composite coating produced at 1344 J/mm 84
4.18 Two dimensional tracks of the worn tracks for (a) AISI 4340 steel (b)
Fe-TiC composite coating subjected to (10 N applied load and 400
RPM sliding speed) under biodiesel lubricated condition 85
4.19 Tafel polarization curve of AISI 4340 steel substrate and Fe-TiC
composite coating produced at 1344 J/mm heat intensity. 86
4.20 Tafel plots of Fe-TiC composite and steel at (a) 40 ᵒC and (b) 60 ᵒC 89
1
CHAPTER ONE
INTRODUCTION
1.1 BACKGROUND
Low alloy steels are regularly used as engineering components in numerous
applications such as in automotive and aerospace industries. They possess
combinatorial superior mechanical properties and toughness and so are widely used as
structural materials and as machine parts (Lampman, 1990). However, these
monolithic metallic materials have poor surface hardness, wear and corrosion
resistance which make them susceptible to gradual failure due to a combination of
factors.
The purpose of conducting surface modification treatments, i.e. formation of a
hard coating layer on a surface of a substrate material, is to customize superior
corrosion and wear resistance properties in engineering components. The durability of
machine parts subjected to dynamic actions strongly depends on the tribological
properties of the surface of the material. Metallic materials fail in their intended
functions because of gradual wear. This is unlike the failure of ceramic materials
which fail permanently because of brittle fracture (Pradeep, Ramesh, & Durga Prasad,
2010).
Tribology or “surface engineering” is a multidisciplinary field of engineering
science which focuses on the interacting surfaces of materials involved in relative
motion with respect to each other (Stolarski, 1990). It studies the application of the
concepts of wear, friction, and lubrication, which are considered to be the dominant
factors that affect the performance of a system, part, or a material during its service.
2
Wear of metallic materials reduces their dimensional stability and functionality,
especially when a part made from such materials is subjected to dynamic loading
conditions. Most worn parts do not fail due to a single mode of wear, such as impact,
but rather from a combination of modes, such as abrasion and impact wear (Holmberg
& Matthews, 1994). For dynamic applications, particularly in automotive industries,
components are required to possess ductile property at the core for impact loading,
while their surfaces must be hard enough to possess enhanced load bearing capacity
and wear resistance. Such combination of hard surface and tough core increases the
material’s service life.
Metallic materials are susceptible to gradual failure caused by its chemical and
electrochemical reactions with its surrounding environment. What further complicates
the situation is the fact that the combined effects of wear and corrosion, which is also
called tribocorrosion, can result in total material loss in a short period of time and lead
to catastrophic failures. Wear debris and corrosion products which are formed during
tribocorrosion can significantly alter the quality of the part’s material by altering its
chemical and electrochemical properties. Corrosion accompanies wear in the gaseous
and liquid environments in which most metallic parts operate and can even occur
without the presence of wear. The interaction of impact, abrasion, and abrasion
exaggerated by corrosion (in gaseous or liquid environments) can result in mass loss
due to wear which can be between 7 and 10 times higher than that in the case of dry
abrading process (Holmberg & Matthews, 1994). This proves that the synergism
between corrosion and wear has the energy to accelerate the damages in machine parts
to a higher degree than wear or corrosive alone. Therefore, surface engineering is
employed to make the material more competitive and reliable in terms of price,
performance, and service applications. Extending the life and servicing performance
3
of parts and tools have been pursued by different industries specifically aerospace and
automotive (Mridha, 2005).
Increasing service performance and tooling life enables to reduce the
maintenance and production costs of materials. Other benefits include shortening the
lead time; meeting delivery schedules, due to reduced tooling down time or less
frequent repairing and replacement; maintaining product quality; and avoiding
rejection due to wear and hence better tolerance control over the manufactured
products etc. These benefits are realized in terms of increased savings through the
application of adequate surface modification and coating techniques.
Metal matrix composite coating widely known as cermets coating is a new
category of materials that posses superior wear and corrosion resistance. It involves
dispersing abrasive ceramics particulate into the substrate surface resulting in a hard
coating layer with superior tribological properties. Various cermets coating have been
deposited on different metal substrates. However, TiC particulates have been used
intensively to reinforce iron based materials due to their high hardness (Zhong, Xu,
Hojamberdiev, Wang, & Wang, 2011), strong mechanical bonding to Fe alloy, and
superior chemical and thermal stability (Das, Bandyopadhyay, & Das, 2002). The Fe-
TiC is now a new category of steel substrate that possesses 10 times better wear
resistance than steel. Thus, attention has been given to this category of material in this
research project.
1.2 PROBLEM STATEMENT AND ITS SIGNIFICANCE
Due to the depletion of the traditional petroleum reservoirs and its negative impact on
ecological systems, the demand for clean, green, reliable, and renewable source of
energy has been increasing. Biodiesel is the type of fuel that meets the above
4
characteristics of eco- friendly fuels (Fazal, Haseeb, & Masjuki, 2011). Biodiesel have
significant mechanical advantages over petroleum diesel such as better lubrication
behaviour, lower green house gases emission and high cetane value. However, its
biocompatibility issue to automotive system restricted its use a substitute fuel to petro-
diesel. Biodiesel is corrosive to common ferrous and nonferrous alloys that exist in
diesel engines such as alumina alloy, Fe-based alloy and Copper alloys (Haseeb,
Fazal, Jahirul, & Masjuki, 2011). Sliding components in the automotive engine system
are made from iron alloy such as plunger and barrel (Haseeb et al., 2011). These
components come in contact with the fuel, while the fuel itself provides the lubrication
for these components and make them susceptible to tribocorrosion attack, where wear
and corrosion are the dominant failure modes of these components.
In order to improve the durability of such systems, protective coating should be
used to mitigate the corrosiveness of biodiesel. Protective coating with superior
corrosion and wear resistance can be applied on the surface of metallic materials thus
prolonging the service life of the material. Among several of coating categories
Carbides, a type of ceramic, have been used extensively as a protective layer for
dynamic applications. They have superior wear resistance, and chemical and thermal
stability. Among these carbides, TiC is highly preferred because of its superior
tribological behaviour. Additionally, it has high strength to weight ratio (Wang, Zou,
& Qu, 2006). Thus, it can be used as a protective material for the dynamic systems
discussed.
Surface melting technique has been used extensively for the last few decades as
a modification technique. It has been proven that incorporating ceramic powders on
the surface of the metallic substrates improves the wear and hardness properties of the
substrates (Mridha, Ong, Poh, & Cheang, 2001). However, no reported wrok have
5
conducted on the tribocorrosin behavior of surface modified Fe-based alloys in
biodiesel environment where corrosion and wear (tribocorrosion) are the doment
failure modes (Haseeb, Sia, Fazal, & Masjuki, 2010) . Thus, it is hypothesized that by
using protective composite coating of TiC on AISI 4340 steel, wear and corrosion
properties of the alloy can be improved when it is subjected to biodiesel environment.
Therefore, this coating material (TiC) can be used for tribocorrosion resistance in
automotive engine applications.
1.3 RESEARCH OBJECTIVES
The main objective of this research is to study the tribological and corrosion
behaviour of Fe-TiC composite coating on 4340 steel produced by TIG torch surface
melting technique in jatropha curcas biodiesel environment. In achieving the main
objectives, the following specific objectives are embarked on:
i. To synthesize and characterise Fe-TiC composite coating by reinforcing
AISI 4340 steel with TiC particulates using powder preplacement and
TIG torch surface melting technique
ii. To investigate the wear behaviour of Fe-TiC composite coating at dry
sliding condition and jatropha curcas biodiesel lubricated condition.
iii. To assess the corrosion behaviour of the surface modified AISI 4340 steel
in jatropha based biodiesel.
1.4 RESEARCH SCOPE
In this research project, a comprehensive study on the tribological and corrosion
behaviour of Fe-TiC composite coating has been performed in order to enhance the
6
tribocorrosion behaviour of AISI 4340 steel upon exposure to jatropha curcas
biodiesel lubricant. The scope of the research project consists of:
i. Incorporating TiC into AISI 4340 steel substrate by preplacement of 1
mg/mm2 of TiC particulate on the surface and glazing it using tungsten
inert gas (TIG) heat source at different heat input. The heat input is varied
by varying the applied current between 70 and 100 A.
ii. Study the influence of the heat input on the composite’s quality using OM,
EDX and SEM.
iii. Micro-hardness and wear testing of the composite coated AISI 4340 steel.
iv. Wear testing of the composite coated steel under jatropha curcas biodiesel
lubricated condition using pin on disc technique.
v. Electrochemical corrosion testing of the composite coated AISI 4340 steel
using tafel tests at various temperatures (ambient, 40 °C, and 60 °C).
1.5 RESEARCH METHODOLOGY
A planed frame work has been set up in order to achieve the objectives of this research
and also shown in Figure 1.1. The main research methodologies are:
i. Acquiring state of the art knowledge on tribo-corrosion of Fe-TiC
composite coatings.
ii. Sample preparation of Fe-TiC composite coatings produced by TIG torch
surface melting.
iii. Metallographic characterization of the composite coating (Optical
Microscope, EDX, SEM).
iv. Mechanical testing of the composite coating (hardness and wear).
v. Biodiesel lubricated wear testing.
7
vi. Electrochemical corrosion testing using Tafel extrapolation method.
Figure 1.1 Flow chart of the research process
End
Surface modification
techniques
State of the art of the triblogical and corrosion behavior of TiC surface
modified AISI 4340 steel in Jatropha biodiesel
Corrosion behavior of
biodiesel
TiC preplacement on AISI 4340 steel surface
TIG torch surface melting at various heat inputs
Fe-TiC composite coating
Tribological behavior
of biodiesel
Literature Survey
Start
Metallographic testing SEM, EDX, OM and hardness
Data analysis
Lubricated wear
test
Dry wear test Corrosion test
(tafel test )
Thesis writing and submission
Optimum
hardness
Yes
No
8
1.6 THESIS ORGANIZATION
The current thesis has been organized into five chapters:
Chapter one: presents an introduction to the research work including the problem
statement and its significant. Objectives of the study and the relevant methodology
followed to conduct the research are also explained in this chapter.
Chapter Two: In chapter two comprehensive literature survey on the related topics
biodiesel, its sources, its characteristics, and the issues related to biodiesel utilization
such as its tribological and corrosive behaviour to common materials used in
automotive engine are discussed in detail. Furthermore, surface modification
techniques used to produce hard coating are also discussed, giving special emphasis
on semi-molten and molten technique used for producing hard coating.
Comprehensive literature survey on metal matrix composite coating (cermets)
produced by semi-molten and molten techniques used to surface modify various
metallic materials focusing on ferro-titanium carbide (Fe-TiC) composite coatings
produced by laser and TIG surface melting techniques.
Chapter three: detailed explanation of the experimental techniques and description of
producing Fe-TiC composite coating by using powder preplacement and TIG torch
surface melting technique were given. Equipment used to analyse the composite
coating and its tribological behaviour at dry and biodiesel lubricated wear condition.
The last part of the chapter provides an explanation of Tafel electrochemical
techniques used to assess the corrosion behaviour of the coated as well as the uncoated
samples in jatropha biodiesel electrolyte as well as the details on the corrosion cell and
the set up used to conduct the test.
Chapter four: presents the results and discussion of Fe-TiC composite coating
processed at different heat inputs. Metallographic, hardness together with dry wear
9
behaviour of the composite coating having the optimum hardness are compared to
AISI 4340 steel. Finally, the corrosion behaviours of the composite coated steel as
well as the AISI 4340 steel were explained using tafel method.
Chapter five: presents a general conclusion of the useful findings and
recommendations for further studies.
10
CHAPTER TWO
LITERATURE REVIEW
2.1 INTRODUCTION
This chapter presents a comprehensive literature review on the main research topics of
the present investigation. It discusses about biodiesels, characteristics of biodiesels,
common issues which arise from the use of biodiesels, and scenarios on the
biocompatibility of biodiesels with automotive materials, specifically the iron based
alloys and other alloys used in the automotive systems. It covers a wide range of
topics, including: modern hard surfacing techniques which are used to surface modify
many engineering materials. It puts special emphasis on cermets coatings produced by
surface melting techniques which enhance the tribological behaviour of engineering
materials.
2.2 BIODIESEL
Biodiesel widely known as fatty acid methyl ester (FAME) is a green and renewable
type of fuel that can be extracted from vegetable base oils and animal fats for diesel
engine applications. It is produced through transesterification or esterification process
of the vegetable oils or animal fats feed stocks converting the triglycerides into small
chain mixture of fatty acids (Gupta, Rehman, & Sarviya, 2010; Hayyan, Ali Hashim,
Mjalli, Hayyan, & AlNashef, 2013; L. Lin, Cunshan, Vittayapadung, Xiangqian, &
Mingdong, 2011). In the transesterification process triglycerides reacts with methanol
with presence of catalysts to form a low density layer of bio-diesel over the
11
precipitated glycerine. The transesterification process is explained by reaction shown
in Figure 2.1
CH2 –COOR1 R1COOR CH2 – OH
| + |
CH – COOR2 + 3ROH R2COOR + CH – OH
| + |
CH2 –COOR3 R3COOR CH2 – OH
Figure 2.1 Transesterification processesof converting triglycerides into biodiesel (Lin
et al., 2011)
The obtained biodiesel loses one third of its density reducing its molecular
weight by factor of 8 (Atadashi, Aroua, & Aziz, 2010). Thus, the biodiesel become
compatible to petroleum diesel. Varity of feed have been used to synthesize high
quality biodiesel. The physio-chemical properties of the biodiesel are strongly
dependent on the type of the fatty acids that generates from the transesterification
process. The common fatty acids exist in the biodiesel and its chemical structure is
explained in Table 2.1.
Table 2.1 Common fatty acids present in biodiesel (Hayyan et al., 2012)
Fatty acids Structure Type of fatty acids
Lauric acid C12:0 Saturated
Myristic acid C14:0 Saturated
Palmitic acid C16:0 Saturated
Palmitoleic C16:1 Unsaturated
Stearic acid C18:0 Saturated
Oleic acid C18:1 Unsaturated
Linolenic acid C18:2 Unsaturated
a-Linolenic acid C18:3 Unsaturated
Arachidic acid C20:0 Saturated
Catalyst