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.

ix

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

x

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

! Bookmark not defined.

xi

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

xii

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

xiii

‎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

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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