UNIVERSITI TEKNIKAL MALAYSIA MELAKA

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

SURFACE INTEGRITY OF ALUMINUM ALLOY LM6 WHEN

MACHINE WITH COATED IDGH SPEED STEEL AND

COATED CARBIDE CUTTING TOOL

This report submitted in accordance with requirement of the Universiti Teknikal

Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering

(Process) (Hons.)

By

NUR NABILAH F ARHANA BINTI SULAIMAN

8050910127

900522105314

FACULTY OF MANUFACTURING ENGINEERING

2013

© Universiti Teknikal Malaysia Melaka

i

ABSTRAK

Dalam setiap operasi pemesinan, prestasi dan kualiti alat memotong dianggap

penting dalam usaha untuk meningkatkan produktiviti dan kecekapan apabila

memotong bahan. Sebagai permintaan meningkat produktiviti dalam industri

pemesinan, keperluan kelajuan pemotongan yang tinggi, kedalaman pemotongan dan

kadar suapan untuk pembuangan bahan adalah wajib. Dalam kajian ini, bahan yang

akan digunakan adalah aloi Aluminium LM6. Kebanyakan penyelidikan sebelumnya

pada aluminium LM6 memberi tumpuan kepada proses tuangan dan pelarik sahaja

yang bermaksud terdapat had ujian mengenai proses pengisaran. Oleh kerana proses

kisar adalah antara yang paling serba boleh dan berguna dan mampu untuk

menghasilkan profil dan pelbagai permukaan melengkung, kajian pengilangan

aluminium adalah penting untuk menentukan alat yang betul memotong, parameter dan

parameter pemotongan. Oleh itu, kajian ini akan memberi tumpuan kepada di mesin

Aluminum Aloi LM6 dari segi pengoptimuman alat memotong, kehidupan alat, dan

memotong parameter dan mekanisme kehausan. Fokus utama kajian ini adalah untuk

menyiasat integriti permukaan aloi Aluminium LM6 menggunakan dua jenis

memotong alat, keluli bersalut kelajuan tinggi dan karbida bersalut. Parameter

pemotongan terbaik yang diperolehi dari eksperimen ini gelendong kelajuan 3000 rpm,

kadar suapan 60 mm / min dan kedalaman dalam pemotongan 0.07 mm menggunakan

bersalut kelajuan tinggi memotong alat keluli. Masa pemesinan adalah berkadar

songsang dengan kedalaman dalam pemotongan. Masa pemesinan yang lebih tinggi

telah diambil sebagai kedalaman jejarian penurunan dipotong. Ia menyimpulkan

bahawa bersalut keluli kelajuan tinggi dipilih sebagai alat terbaik untuk memotong

aluminium pemesinan LM6 kerana harga adalah lebih murah dan kemasan permukaan

adalah lebih baik berbanding dengan karbida bersalut.

ii

ABSTRACT

In every machining operation, performance and quality of cutting tools are

considered essential in order to increase productivity and efficiency when cutting

materials. As the increasing demand of productivity in machining industry, the need of

high cutting speed, depth of cut and feed rate for material removal are compulsory. As

the use of high cutting temperature will eventually causes reduces in tool life as well as

impairs the product quality, developments of coated cutting tool are made to improve

the weakness of uncoated cutting tool. However, the material itself also contributed to

tool wear and wear mechanism of the cutting tool. In this study, material that will be

use is Aluminum LM6 alloy. However, most of the previous researches on aluminium

LM6 are focusing on turning and casting only which means there are limitation trials

regarding milling process. Since millings are among the most versatile and useful tools

and also capable to produce various profiles and curved surfaces, the study of

aluminum milling is important to determine the right cutting tool, parameter and

cutting parameter. Therefore, this study will focus on machinability of LM6 in terms of

optimization of cutting tool, tool life, and cutting parameter and surface integrity. The

main focus on this study is to investigate the surface integrity when machining

Aluminum alloy LM6 using two different types of cutting tool which are coated high

speed steel and coated carbide. The outcome is surface finish for coated high speed

steel is better compared to coated carbide. The best cutting parameters obtained from

the experiment are spindle speed 3000 rpm, feed rate 60 mm/min and radial depth of

cut 0.07 mm using coated high speed steel cutting tool. Machining time is inversely

proportional to radial depth of cut. Higher machining time was taken as the radial depth

of cut decrease. It is concluded that coated high-speed steel is selected as the best

cutting tool for machining aluminium LM6 because the price are less expensive and the

surface finish is better as compared to coated carbide.

iii

DEDICATION

To my beloved parents and siblings.

iv

ACKNOWLEDGEMENT

I would like to express my greatest gratitude to Allah SWT for giving me chances to

explore and gain new knowledge throughout the period of completing my Final Year

Project. I would also like to thank my family especially my beloved parents for their

never ending support and courage in terms of financial and emotion as well as their

prayers in order to provide me with better education for a better and brighter future.

Not to forget, millions of thanks I wish to my supervisor Dr. Hadzley bin Abu Bakar

for his continuous guidance and support throughout my learning process and

completing this study. I would also like to thanks each and everyone in Faculty of

Manufacturing Engineering; the lecturers, staffs and technicians for the cooperation in

sharing their experiences and knowledge as well as their time and energy.

I would also like to express my deepest appreciation to all my friends for their efforts

and willingness in sharing every knowledge and information without any difficulties.

Last but not least, I am also thankful to all those people who have directly or indirectly

helped me throughout this period.

v

TABLE OF CONTENT

Abstrak i

Abstract ii

Dedication iii

Acknowledgement iv

Table of Content v

List of Tables viii

List of Figures ix

List Abbreviations, Symbols and Nomenclatures xi

CHAPTER 1: INTRODUCTION 1

1.1 Introduction 1

1.2 Problem Statement 2

1.3 Objective 3

1.4 Scope of Project 3

CHAPTER 2: LITERATURE REVIEW 4

2.1 Aluminum 5

2.1.1 Aluminum Alloy 6

2.1.2 Metal Matrix Composites 6

2.2 LM6 (AISI 413) - Aluminum Alloy 6

2.2.1 Properties 7

2.2.1.1 Chemical properties 7

2.2.1.2 Machinability 8

2.2.1.3 Corrosion Resistance 9

2.2.1.4 Physical Properties 9

2.2.1.5 Mechanical Properties 9

2.2.2 Applications 9

2.3 Machining 10

2.3.1 Elements of Machining 11

vi

2.3.2 Classical Metal Machining Process 12

2.4 Milling machines 13

2.4.1 Peripheral Milling 14

2.4.2 Face milling 15

2.4.3 End milling 16

2.4.4 Cutting Parameter 17

2.4.4.1 Cutting Speed 17

2.4.4.2 Feed Rate 18

2.4.4.3 Depth of Cut 19

2.5 CNC Milling Machine 20

2.6 Cutting Tool 22

2.6.1 Coated High-Speed Steel cutting tool 23

2.6.2 Coated Carbide cutting tool 24

2.7 Surface Integrity 25

2.7.1 Surface Roughness 26

2.7.2 Material Side Flow 28

2.7.3 Build-Up Edge 29

2.7.4 Subsurface Microstructure Alteration 30

2.7.5 Changes in Microhardness

CHAPTER 3: METHODOLOGY 32

3.1 Project Planning 33

3.2 Experimental Equipment 34

3.3 Work Material 35

3.3.1 Aluminum LM6 Alloy 35

3.4 Cutting Tool 36

3.5 Cutting Condition 39

3.6 Machining 40

3.6.1 Bandsaw Machine 40

3.6.2 CNC Milling 3 Axis 41

3.7 Testing 42

3.7.1 Surface Roughness Measurement 42

3.8 Specimen Preparation 43

vii

3.8.1 Cutting Tool 43

3.8.2 Workpiece after Machining 44

3.8.3 Subsurface Microhardness Measurements 46

CHAPTER 4: RESULT & DISCUSSION 47

4.1 Introduction 47

4.2 Microstructure of Aluminum LM6 Alloy before machining 48

4.3 Parameter Selection 50

4.4 Surface Profile 54

4.5 Surface Roughness 58

4.6 Microstructure 61

4.7 Microhardness 63

CHAPTER 5: CONCLUSION AND RECOMMENDATIONS 65

5.1 Conclusion 65

5.2 Recommendations 67

REFERENCES 68

APPENDIX 71

viii

LIST OF TABLES

2.1 Chemical Properties of Aluminum LM6 7

2.2 Physical Properties of Aluminum LM6 8

2.3 Mechanical Properties of Aluminum LM6 9

3.1 Chemical composition of Al LM6 alloy 35

3.2 Mechanical properties of Al LM6 alloy produced by chill cast 36

3.3 Physical properties of Al LM6 alloy 37

3.4 Cutting parameters 39

4.1 Cutting parameter selection using uncoated high speed steel 51

4.2 Result for surface roughness (Ra) 58

4.3 Hardness data for surface machined by coated high speed steel 63

4.4 Hardness data for surface machined by coated carbide 65

ix

LIST OF FIGURES

2.1 Aluminum Alloy LM6 in ingot shape 6

2.2 Deformation of material in machining 11

2.3 (a) Orthogonal cutting 12

(b) Oblique cutting 12

2.4 (a) Peripheral milling 14

(b) Face milling. 14

(c) End milling. 14

(d) Ball-end mill 14

(e) Milling, using a five axis numerical control machine 14

2.5 (a) Schematic illustrations of conventional milling and climb 15

(b) Slab milling 15

(c) Schematic illustration of cutter travel distance 15

(d) Dimensions in face milling 15

2.7 (a) small corner radius 15

(b) Corner flat on inserts 15

(c) Wiper. 15

(d) Feed marks due to various insert shape 15

2.8 CNC milling machine 20

2.9 Coated High-Speed Steel (TiAlN) cutting tool 23

2.10 Coated Carbide cutting tool (TiAlN) 24

2.11 Schematic illustration to determine arithmetic average surface

roughness, Ra of surface texture

27

2.12 Example of material side flow 28

2.13 (a) Shearing of the workpiece materials during machining 30

2.13 (b) Microstructure alterations beneath the machined surface 30

2.14 The microhardness value measured beneath the machined surface 31

x

3.1 Flow Chart 33

3.2 Aluminum LM6 Alloy 35

3.3 Coated High-Speed Steel (TiAlN) cutting tool 38

3.4 Coated Carbide cutting tool (TiAlN) 38

3.5 Bandsaw Machine 40

3.6 Haas’ 3 axis CNC vertical milling machine 41

3.7 Surface roughness tester Mitutoyo SJ-301 42

3.8 CARL ZEISS evo 50 scanning electron microscope (SEM) 43

3.9 Buehler Simplimet 3000 Automatic Mounting Press Machine 44

3.10 Buehlers Beta Twin Variable Grinder-Polisher 45

3.11 Sample preparation items for polishing 45

3.12 Mitutoyo Hardness Testing Machine MicroWizhard HR-500 46

4.1 Microstructure of aluminium LM6 48

4.2 Surface profile using coated high speed steel (a) Using 29X

magnification.

52

4.2 (b) Using 150 X magnifications

52

4.3 Surface profile using coated carbide (a) Using 17X magnification 54

4.3 (b)Using 150X magnification

54

4.4 Average Value of surface roughness VS radial depth of cut 57

4.5 Graph for time VS radial depth of cut

59

4.6 (a) Subsurface microstructure when machining aluminium LM6 using

coated high speed steel

60

4.6 (b) Subsurface microstructure when machining aluminium LM6 using

coated carbide

60

4.7 Hardness value when using coated high speed steel 62

4.8 Hardness value when using coated carbide 64

xi

LIST OF ABBREVIATIONS, SYMBOLS AND

NOMENCLATURE

Al - Aluminium

CNC - Computer Numerical Control

Cu - Copper

d - Diameter

f - Feed rate

ft - Feed per Tooth

HSS - High-Speed Steel

Mg - Magnesium

Mm - millimeter

MMC - Metal matrix composites

Mn - Manganese

n - Cutter speed in revolution per minute

Ø - Angle of shear

Rpm - revolution per minute

RSM - Response Surface Methodology

SEM - Scanning Electron Microscopic

Si - Silicon

TiN - Titanium Nitride

TiAlN - Titanium Aluminium Nitride

V - Cutting speed

WC - tungsten carbide

) - Feed per Revolution

- Feed per Unit of Time

1

1.0 Introduction

Nowadays, machining of material are getting more advance as there are many

developments of new alloys and engineered material which eventually causes these

materials to have high strength and toughness as well as other material properties. In

manufacturing operations, it is important to view machining operations as a system,

consist of workpiece, cutting tool, machine tool and also production personnel.

Machining cannot be carried out efficiently or economically and also meet stringent

part specifications without a thorough knowledge of the interactions among these

four elements [Kapalkjian and Schmid (2006)].

One of the materials that are used in industry is aluminium alloy. The important

factors in selecting aluminum (AL) and its alloy are their high strength to weight

ratio, resistance to corrosion by many chemicals, high thermal and electrical

conductivity, nontoxicity, reflectivity, appearance, and ease of formability and of

machinability: they are also nonmagnetic [Kapalkjian and Schmid (2006)]. One of

the examples of aluminum alloy in industry is aluminum LM6. LM6 is a high purity

alloy, which is used in castings where thinner more intricate sections are required

particularly in a complex casting with large surface areas. This alloy has of medium

strength with excellent ductility but suffers a rapid loss of properties at elevated

service temperatures. Application of LM6 in industry includes electrical, marine,

intricate shaped castings, and buildings cladding panels.

INTRODUCTION

CHAPTER 1

2

In milling process, their efficiency depends on characteristics such as surface finish,

dimensional tolerances, production rate, and cost considerations. Many types of

milling machines are used, ranging from relatively simple and versatile machines

that are used for general purpose machining in job shops and tool and die work to

highly specialized machines for mass production. Some important factor in milling

are selection of cutting tools, cutting parameters such as cutting speed, feed rate and

depth of cut. These factors influence the efficiency of the machine in terms of time

usage, cost and operation technique. Machining of Aluminum LM6 is also influenced

by these processing items.

However, most of the previous researches on aluminium LM6 are focusing on

turning and casting only which means there are limitation trials regarding milling

process. Since millings are among the most versatile and useful tools and also

capable to produce various profiles and curved surfaces, the study of aluminum

milling is important to determine the right cutting tool, parameter and cutting

parameter and surface integrity. Therefore, this study will focus on machinability of

LM6 in terms of surface integrity such as surface roughness, surface microhardness,

subsurface micro structure, and surface profile using two different types of cutting

tool which are coated high speed steel and coated carbide. Machining will be held in

CNC milling and the data will be based on its surface integrity and tabulated. The

expected outcome is to have database, guidance, fine property to machine Aluminum

LM6 efficiently and also good machinability cost.

3

1.1 Problem Statement

In present, machining of Aluminum Alloy LM6 in industry are widely used only in

casting and turning. There is lacking of research on milling Aluminum Alloy LM6

thus this project will initiate the machining trials of Aluminum LM6 in milling

process. The evaluation will be based on the surface roughness, surface

microhardness, subsurface micro structure, and surface profile. By undergoing this

project, it will benefited and contribute to the industry in terms of the optimization of

cutting tool, cutting parameter and surface integrity in milling of Aluminum Alloy

LM6.

1.2 Objectives

There are three main objectives by doing this project:

a) To identify the suitable cutting tool for milling machine.

b) To identify the appropriate cutting parameters for producing good surface.

c) To investigate whether the type of cutting tool and cutting parameters

affecting surface integrity of Aluminum LM6.

1.3 Scope of Project

This project will be focus on investigating the surface integrity of Aluminum LM6

using two different cutting tools which are coated carbide and coated high speed

steel. When all the data have been obtained and recorded, it will then is tabulated and

analyze. In analyzing the data, graph for results will be shown in results and

discussion section.

4

2.1 Aluminum

Pure aluminium is a weak, very ductile material. Its physical properties are shiny,

silvery white colored metal that is light in weight and strong. The density of

aluminum is 2.7 g/mL, which means the metal will sink in water, but is still

relatively light. The mechanical properties depend not only on the purity of the

aluminium but also upon the amount of work to which it has been subject. A range of

tempers is thus produced by different amounts of work hardening. It has an electrical

conductivity about two-thirds that of copper but weight for weight is a better

conductor. As for its chemical properties, the surface of aluminum metal is covered

with a thin layer of oxide that helps protect the metal from attack by air. So,

normally, aluminum metal does not react with air. If the oxide layer is damaged, the

aluminum metal is exposed to attack. As it has a great affinity for oxygen and any

fresh metal in air rapidly oxidizes to give a thin layer of the oxide on the metal

surface. This layer is not penetrated by oxygen and so protects the metal from further

attack [W.Bolton (2000)].

LITERATURE REVIEW

CHAPTER 2

5

2.1.1 Aluminium Alloy

Aluminium alloy can be divided into two groups which are, wrought alloys and cast

alloys. Each of these can be divided into two further groups: those alloys which are

not heat treatable and those which can be heat treated. The non-heat treatable alloys

have their properties controlled by the extent of the working to which they are

subject. A range of tempers is thus produced. The heat-treatable alloys have their

properties controlled by heat treatment. Like aluminium, the alloys have a low

density, good electrical and thermal conductivity and a high corrosion resistance. The

corrosion resistance properties of sheet alloy are improved by cladding it with layers

of unalloyed aluminium. [W.Bolton (2000)]. Aluminum LM6 are categorised in cast

alloys and it contains composition of Silicon (Si), Copper (Cu), Manganese (Mn) and

Magnesium (Mg).

2.1.2 Metal Matrix Composites

Metal matrix composites are engineered materials combining two or more materials,

one of which is a metal, where the properties can be attained by systematic

combination of different constituent. A variety of methods available for producing

these advanced materials include the conventional casting process which is

considered as the easiest processing technique. Preparation of these composite

materials by foundry technology has the unique benefit of near-net shape fabrication

in a simple and cost-effective manner. Besides, casting processes lend themselves to

manufacture large number of complex shaped components of composites at a faster

rate required by the automotive, transportation, sports and other consumer oriented

industries. Metal matrix composites (MMC) are composed of an elemental or alloy

matrix in which a second phase is embedded and distributed to achieve some

property improvement. As for Aluminum LM6 that are used in this study, it often use

as matrix in producing alloy matrix composites to enhance their properties. In

previous research conducted by [ Hamouda et al (2007)] , Aluminum LM6 alloy act

as matrix while different percentages of silicon dioxide based on the variation in

6

volume fraction act as particulates to produces reinforced LM6 alloy matrix

composites.

2.2 LM6 (AISI 413)- Aluminum Alloy

LM6 is a high purity alloy, which is normally used in castings where thinner more

complex sections are required particularly in a complex casting with large surface

areas. The alloy is of medium strength with excellent ductility but suffers a rapid loss

of properties at elevated service temperatures. However, it is also depending on its

particulates in which contributes and varies in terms of its mechanical properties

such as tensile strength, elongation, fatigue strength, machinability and also shear

strength.

LM 6 is a high Silicon Aluminium alloy which can be rather difficult to machine.

Alloys of this type tend to drag when machined, causing rapid tool wear and

therefore carbide tools with large rake angles should be employed with adequate

cutting fluids.

Figure 2.1: Aluminum Alloy LM6 in ingot shape.

7

2.2.1 Properties

2.2.1.1 Chemical Properties

Table 2.1: Chemical Properties [http://www.nortal.co.uk/LM6/]

Percentage (%) EN 1706 AC-44100

Copper 0.1 max 0.15(0.10)

Magnesium 0.10 max 0.10

Silicon 1-.0-13.0 10.5-13.5

Iron 0.6 max 0.65(0.55)

Manganese 0.5 max 0.55

Nickel 0.1 max 0.20

Zinc 0.1 max 0.25

Lead 0.1 max 0.20

Tin 0.05 max -

Titanium 0.2 max 0.20(0.15)

Aluminium remainder -

8

2.2.1.2 Machinability

An enduring problem with this material is that they are rather difficult to machine.

This is due to the high hardness of the reinforcement materials which in many cases

are significantly harder than the commonly used high speed steel tools and carbide

tools. [Joardar et al. (2011)]. As for those issues, many previous and present

researches are conducted to find and focused on optimizing some machining

parameters so that roughness of the machined surfaces and tool wear can be

minimized.

2.2.1.3 Corrosion Resistance

LM6 exhibits excellent resistance to corrosion under both ordinary atmospheric and

marine conditions. For the severest conditions, this property can be further enhanced

by anodic treatment. [Hadleighcastings (2012)]

2.2.1.4 Physical Properties

Table 2.2: Chemical Properties [http://www.nortal.co.uk/LM6/]

Coefficient of Thermal Expansion (per°C at 20-100°C) 0.000020

Thermal Conductivity (cal/cm 2 /cm/°C at 25°C) 0.34

Electrical Conductivity (% copper standard at 20°C) 37

Density (g/cm 3 ) 2.65

Freezing Range (°C) approx 575-565

9

2.3.1.5 Mechanical Properties

Table 2.3: Mechanical Properties [http://www.nortal.co.uk/LM6/]

SAND CAST CHILL CAST

0.2% Proof Stress

(N/mm2)*

60-70 70-80

Tensile Stress (N/mm2)* 160-190 190-230

Elongation (%)* 5-10 7-15

Impact Resistance. Izod

(Nm)

6.0 9.0

Brinell Hardness Number 50-55 55-60

Endurance Limit (5 X 107

cycles; + N/mm2)

51 68

Modulus Of Elasticity (X

103 N/mm2)

71 71

Shear Strength (N/mm2) 120

2.2.2 Applications

LM6 has a high resistance to corrosion and excellent cast ability. It is often uses in

numerous places due to these properties such as marine, manifolds, motor casings,

cast doors, pumping applications. It is also especially suitable where castings need to

be welded together. The ductility of LM6 castings means they can be easily rectified

and modified into shape. It also has excellent resistance to corrosion in marine

environments, possesses excellent ductility, but is of medium strength and is not heat

treated. Its strength falls off rapidly at high temperatures. Its elastic limit is low and it

is fairly difficult to machine. [Hadleighcastings (2012)]