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THESIS

c—J

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r)“.“_‘

(003é93zi/5

This is to certify that the
thesis entitled

TOPOGRAPHIC IMAGING OF TOOL WEAR IN MULTILAYER
COATED INSERTS

presented by
JORGE A. OLORTEGUl-YUME

has been accepted towards fulfillment
of the requirements for the

Master of Science degree in Mechanical Enfleering

W %A
Major Professor’s Signature

5745/94

Date

 

 

 

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DATE DUE DATE DUE DATE DUE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6/01 cJCIRC/DateDuepes-pts

 

TOPOGRAPHIC IMAGING or: TOOL WEAR IN MULTILAYER COATED
INSERTS
By

Jorge A. Olortegui-Yume

A THESIS
Submitted to
Michigan State University
In partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE

Department of Mechanical Engineering

2004

ABSTRACT

TOPOGRAPHIC IMAGING or: TOOL WEAR IN MULTILAYER COATED
INSERTS
By

Jorge A. Olortegui-Yume

The present study deals with the confocal imaging of tool wear in multi-layer
coated inserts using Confocal Laser Scanning Microscopy (CLSM) as a means to
obtain the tool wear evolution in a local level.

Steady-state turning experiments were carried out on 1045 steel bars with multi-
layer coated inserts consisting of TiN /Al203 /TiCN deposited on a carbide
Substrate. Topographical images of the crater wear as well as orthogonal
sections of the flank and crater wears as functions of machining time were
obtained. After the Scanning electron microscope (SEM) image analysis a
humped island of TiN coating material next to growing a crater of AI203 and steel
traces were found. The maximum crater depth location was observed to move
across the rake face with machining time. These unexpected features of crater
wear seem to have their origin in the competition of the abrasive and dissolution
mechanisms. Validations of the confocal results were performed using the SEM

and the Atomic force microscope (AFM).

DEDICATION

To

The One who is and who was and who is to come

ACKNOWLEDGEMENTS

It is a pleasure to acknowledge Dr. Patrick Kwon, my academic advisor, for his
guidance and instruction during the duration of this research work. His patience

and mentorship contributed greatly to the completion of this thesis.

I wish to extend my gratitude to my dissertation committee members: Dr. Shirley
Owens and Dr. Brian Feeny for their invaluable contribution to this dissertation

through their advice and suggestions.

I would also like to point out the professionalism and friendship of Dr. Stanley
Flegler, Dr. Joanne Whallon, Carol Fleger, and Ewa Danielewicz at the Center

for Advanced Microscopy of Michigan State University.

My gratitude and love to Lucy, my wife, for her encouragement, love and hard
work. I am more than thankful to my mother for all the sacrifice, support and

godly love given to me during my whole life.

My thanks to my friends and co-workers Chee-Kuang Kok, Tim Wong and Yi-
Chong Zeng for their kindness, help and understanding despite their hectic

agenda.

TABLE OF CONTENTS

 

 

 

 

LIST OF TABLES ............................................................................................. VII
LIST OF FIGURES .......................................................................................... VIII
KEY To SYMBOLS OR ABBREVIATIONS ...................................................... XI
OVERVIEW .......................................................................................................... 1
Chapter 1 : INTRODUCTION To WEAR IN CUTTING TOOLS ....................... 3
1.1 MACHINING TECHNOLOGY TERMS AND DEFINITIONS ....................... 4
1.2 PRINCIPAL FORMS OF TOOL WEAR ...................................................... 7
1.3 TOOL WEAR BEHAVIOR ........................................................................ 11
1.4 TOOL-LIFE CRITERION AND TOOL LIFE .............................................. 12
1.5 TOOL WEAR MECHANISMS ................................................................... 14
1.6 COATED CUTTING TOOLS .................................................................... 19
Chapter 2 : INTRODUCTION To ADVANCED MICROSCOPY .............. -21
2.1 MICROSCOPY BASIC DEFINITIONS ...................................................... 22
2.2 CONFOCAL LASER SCANNING MICROSCOPY (CLSM) ...................... 27
2.3 THE SCANNING ELECTRON MICROSCOPE (SEM) ............................. 37
2.4 THE ATOMIC FORCE MICROSCOPE (AFM) .......................................... 38
Chapter 3: STATEMENT OF THE PROBLEM ................ __ ..... 40
3.1 LITERATURE REVIEW ON SURFACE TOPOGRAPHY ......................... 4o
3.2LITERA TURE REVIEW ON CLSM APPLICATIONS ................................ 41
3.3 RESEARCH FOCUS ................................................................................ 42
Chapter 4 : EXPERIMENTAL WORK ............................................................. 44
4.1 MACHINING EXPERIMENTS .................................................................. 44
4.2 CONFOCAL MICROSCOPY DA TA ACQUISITION ................................. 50
4.3 ELECTRON MICROSCOPY DATA ADQUISITION .................................. 61
4.4 ATOMIC FORCE MICROSCOPY DATA ADOUISITION .......................... 64
Chapter 5 : RESULTS AND DISCUSSIONS- _ __ ________ _ 67
5.1 VALIDATION OF THE CRA TER SHAPE ................................................. 67
5.2 CRA TER WEAR EVOLUTION AND MEASUREMENTS .......................... 68
5.3 ATOMIC FORCE MICROSCOPE RESULTS ........................................... 86
5.4 FLANK WEAR EVOLUTION AND MEASUREMENTS ............................. 86
Chapter 6 : SUMMARY AND CONCLUSIONS ............................................... 96

APPENDICES .................................................................................................... 98

APPENDIX A : SEM MERGED IMAGE OF CRATER WEAR ........................... 99
APPENDIX B: EDS SPECTRAL ANALYSIS AND X-RAY DOT MAPS .......... 100
APPENDIX C : BSE IMAGES OF CRATER WEAR ........................................ 103
APPENDIX D : X-RAY LINESCANS OF CRATER WEAR ............................. 107
APPENDIX E : 5X AND 50X OBJECTIVE DATA COMPARISON .................. 1 11
APPENDIX F: ATOMIC FORCE MICROSCOPE IMAGES ............................. 115
APPENDIX G: BSE IMAGES OF THE FLANK FACE .................................... 122
BIBLIOGRAPHY .............................................................................................. 124

Vi

LIST OF TABLES

Table 4-1 Inserts and comers used in the experiments ...................................... 46
Table 4-2 Geometrical dimensions of the SNMA 643 insert [35] ......................... 48
Table 5-1 Crater areas measurements for all machining times ........................... 75
Table 5-2 Maximum crater depth location for all machining times ....................... 80

Table 5-3 Time evolution of slope values at the flank face for reference 300s....90
Table 5-4 Time evolution of Slope values at the flank face for reference 4803....91

Table 5-5 Time evolution of slope values at the flank face for reference 7203....92

vii

LIST OF FIGURES

Figure 1.1 Orthogonal View of the machining process [1] ..................................... 4
Figure 1.2 Feed and depth of cut [2] ..................................................................... 5
Figure 1.3 Nomenclature for the geometry of single-point cutting tools [2] ........... 6

Figure 1.4 Progressive wear observed in the most common cutting tools [4] ....... 7

Figure 1.5 Schematic illustrations of catastrophic tool failures [4] ......................... 8
Figure 1.6 Regions of tool wear in metal cutting [3] .............................................. 9
Figure 1.7 Sketch of a worn tool during cutting [5] .............................................. 10
ngre 1.8 Flank wear development with time(carbide tool at 1 m/s) [3] ............. 12
Figure 1.9 Effect of cutting speed on tool flank wear [1] ...................................... 13
Figure 1.10 Some features of a Single-point tool wear in turning [3] ................... 14
Figure 1.11 Adhesive wear representation .......................................................... 15
Figure 1.12 Two body and three body abrasion .................................................. 16
Figure 1.13 Model of diffusion wear after Nahemtein and Trent [8] .................... 18

Figure 2.1 Depth resolution using a BOX/0.90 Objective in air at 1:633 nrn [211.23

Figure 2.2 Simplified schematic of a conventional light microscope [21] ............. 26
Figure 2.3 Illustration of the objective lens and the focal plane ........................... 27
Figure 2.4 The confocal principle ........................................................................ 29
Figure 2.5 A typical Laser Scanning Confocal system [25] ................................. 30
Figure 2.6 Z-stack computer rendering of a simplified sample ............................ 34
Figure 2.7 Simplified schematic of a phi-z section .............................................. 35
Figure 2.8 Intensity profiles and its relation to surface position ........................... 35

viii

Figure 2.9 Intensity profiles shapes ..................................................................... 36

Figure 2.10 Simplified rendering of a SD reconstruction ..................................... 36
Figure 2.11 Simplified schematic of a SEM [21] .................................................. 38
Figure 2.12 Schematic of the AFM principle of operation [21] ............................. 39
Figure 4.1 Clausing/Colchester variable speed lathe( Model 8033) .................... 44
Figure 4.2 Insert and toolholder arrangement ..................................................... 47
Figure 4.3 Geometry of a the SNMA 643 insert [35] ........................................... 48

Figure 4.4 Reflection confocal image of the multi-Iayer insert cross section ....... 49

Figure 4.5 Zeiss LSM 210 confocal microscope .................................................. 50
I-"rgure 4.6 References for alignment in the LSM 210 pictures ............................ 52
Figure 4.7 (a), (b) Five sections method (Isolines View) ...................................... 56
Figure 4.8 Reference locations for crater wear evolution .................................... 59
Figure 4.9 Evolution of the crater obtained overlaying the B-B sections ............. 59
Figure 4.10 JSM-6400 Scanning Electron Microscope ....................................... 61
Figure 4.11 Nanosc0pe Ill scanning probe microscope ...................................... 66
Figure 5.1 (a), (b) Confocal views of the Vynil poxysiloxane replica .................. 67

Figures 5.2 (a),(b) Features of the crater wear for the multi-layer coated insert .69
Figure 5.3 2D confocal images showing the evolution in time of the crater wear70
FIgure 5.4 Topographical Views of the worn comers for all machining times ...... 71
Figure 5.5 BSE image of a worn corner with the chemical elements observed...73
Figure 5.6 Plot of the crater areas evolution in machining time ........................... 76
Figure 5.7 Plot of the length and width evolution for the exposed Alumina area.76

Figure 5.8 Variation of the width limits position of the crater in time .................... 77

Figure 5.9 Orthogonal sections obtained at the maximum crater depth location.79
Figure 5.10 Plot of the maximum crater depth location versus machining time ..81
Figure 5.11 Plot of the maximum crater depth versus machining time ................ 81
Figure 5.12 Time evolution of crater wear at the 300 6 reference (5X objective) 83
Figure 5.13 Time evolution of crater wear at the 300 S reference (5X objective) 84

Figure 5.14 Time evolution of crater wear at the 720 S reference (5X objective) 85

Figure 5.15 Flank wear evolution at the 300 s reference (50X objective ) ........... 88
Figure 5.16 Flank wear evolution at the 480s reference ( 50 X objective ) .......... 88
Figure 5.17 Flank wear evolution at the 720 S reference ( 50X objective ) .......... 89
Figure 5.18 Plot of slopes 1 and 2 versus machining time (300 s ref.) ................ 93
Figure 5.19 Plot of slopes 3, 4, and 5 versus machining time (300 S ref.) ........... 93
Figure 5.20 Plot of slopes 1 and 2 versus machining time (480 s ref.) ................ 94

Figure 5.21 Plot of the slopes 3, 4, and 5 versus machining time (480 s ref.) ..... 94
Figure 5.22 Plot of slopes 1 and 2 versus machining time (720 s ref.) ................ 95

Figure 5.23 Plot of slopes 3, 4, and 5 versus machining time (720s ref.) ............ 95

CLSM

SEM
BSE
EDS

AFM
SPM
N.A.
FOV
LSM
HSS
BUE
TEM
TiN
Alea
TiCN
WC

MCDL

Sfpm

dz

20W)

KEY TO SYMBOLS OR ABBREVIATIONS

Confocal Laser Scanning Microscopy
Scanning Electron Microscopy
Backscattered electrons

Energy dispersive spectroscopy
Average Atomic Number
Atomic Force Microscopy
Scanning Probe Microscopy
Numerical aperture

Field of View

Laser Scanning Microscope
High Speed Steel

Built-up edge

Transmission Electron Microscopy
Titanium nitride

Aluminum oxide

Titanium carbonitride

Tungsten carbide

Maximum crater depth location
Surface feet per minute

Depth resolution (pm)

Light source wavelength (pm)

2 matrix

xi

|(X.Y)
Zm

W1

W2

W3

Zmax
Xr

Yr

Intensity matrix

Maximum intensity position (pm)

Magnification

Focal distance (mm)

Darkest crater area (pmz)

Crater area defined by the inland ad edge side limits (umz)
Length of A1 measured parallel to the trailing edge (pm)

Width of A1 measured parallel to the trailing edge (um)

Position of the edge Side limit of the crater respect to the trailing
edge (um)

Position of the inland side limit of the crater respect to W1 (pm)
Position of the inland side limit of the crater respect to the trailing
edge (um)

Maximum crater depth location (pm)

Reference respect to the minor cutting edge (pm)

Reference respect to the main cutting edge or trailing edge (urn)
Maximum crater depth location respect to the minor cutting edge
(um)

Maximum crater depth location respect to the main cutting edge or

trailing edge (um) matrix

xii

OVERVIEW

The automation of machining processes in different industrial applications is a
growing trend that requires an advanced scientific methodology to predict tool
wear. This methodology should include the development of a new wear model
must be capable of predicting tool life with better accuracy than the conventional
methods. The shift to the usage of this new methodology would mean a drastic
reduction of the huge amount of experimental research and related costs. Two
main issues are attached to the development of this new methodology: an
improved understanding of the wear phenomenon and a meaningful way to
measure it. So far, most of the published work is based on the measurement of
average properties of wear (traditional method) rather than in a localized analysis
of the phenomenon.

This study intends to enhance, if not start, a new trend in tool wear measurement
by means of providing a local level approach. The present approach will include
the analysis of crater wear topography, time evolution of orthogonal wear profiles
in specific locations, specially in the maximum depth locations, and the elapsed-
time flank wear profiles for the same locations.

A Confocal Laser Scanning Microscope (Zeiss LSM 210) was used in reflective
mode to get the topographical imaging of craters in multi-layer coated inserts
along with the cross sections in defined locations. The sectioning feature of this
microscope allowed the gathering of the orthogonal sections in the trailing edge
for the analysis of flank wear. All the measurements where obtained using the

built in software that comes with the microscope. The use of a Scanning Electron

1

Microscope (SEM) was necessary in order to establish the limits of each layer in
connection with the growing worn areas of the insert. Validation of the
information obtained with a Confocal Microscope was done with an Atomic Force

Microscope (AFM).

Chapter 1 : INTRODUCTION TO WEAR IN CUTTING TOOLS

Although many great efforts have been made to understand the nature of tool
wear, it continues to have unsolved problems. The relevance of better solutions
to these problems lies on the great economical impact such solutions bring to
industry. In the meanwhile, companies have to continue dealing with the four
main economical effects of tool wear: Lower workpiece quality due to the
deterioration in finish and dimensional accuracy, the damage on expensive work
pieces if the cutting edge fails catastrophically, the cost of changing cutting
edges and tools, and the increased power consumption due to excessive
plasticity. Assuming that a complete understanding of the wear phenomenon was
at hand, tool life could be more clearly defined and predicted, therefore, the
economical effects could be minimized.

All the ongoing work in tool wear is oriented to three fundamental goals: (1)
reliable prediction of tool wear, (2) in situ wear detection from measurements,
and (3) wear prevention by the development of a new tool. The focus of the
present study is to provide a micro-level approach for a better understanding of
wear topography and wear measurement, which eventually will lead to the
accomplishment of the first goal while giving a better understanding with the

second.

1.1 MACHINING TECHNOLOGY TERMS AND DEFINITIONS

Machining is a manufacturing process in which a cutting tool is used to remove
excess material from a workpart so that the remaining material is the desired part
shape. The predominant cutting action involves shear deformation of the work
material to form a chip; as the chip is removed, a new surface is generated. The

machining process is most Simply illustrated orthogonally (figure 1.1).

Rake angle (a)

  
  
  
 
   

Motion of chlp Motion of tool
(relative to work)
onginal surface Relief angle

New surface

Shear defamation
to form chip

Cutting edge of tool

Figure 1.1 Orthogonal view of the machining process [1]

To perform the machining operation by removal of the chip, a relative motion is
required between the tool and the work. In orthogonal machining operations, this
motion is achieved by means of a primary motion, called the Speed, and a
secondary, motion called the feed. The shape of the tool combined with its
penetration into the workpiece, combined with these motions, produced the

desired shape of the resulting work surface [1].

1.1.1 CUTTING CONDITIONS

In general, an actual machining operation is much more complex, requiring the
combination of cutting speed (v), feed (f) and depth of cut (d), which are called
the cutting conditions, to control the process (figure 1.2). The speed at which
primary motion is accomplished is known as cutting speed (v) and is expressed
in feet lmin (Sfpm) or anin. The feed, (1) is the lateral movement across the
work to provide the secondary motion and comes expressed in inch/rev or
mm/rev. The depth of cut (d) is the penetration of the cutting tool below the
original surface of the workpiece. This is expressed in inches or mm. Additional
descriptions needed to depict the geometry of a tool include the Side cutting
edge (or Approach) angle, the End cutting edge angle and, the comer or nose

radius.

 

 

 
 
    

Primary motion

WORKPIECE (Cutting speed)

Corner
radiu

 

 

 

  
  

 

 

Secondary

motion (feed) /,

End (minor)

Side (major) cuttlng edge
cuttlng edge angle
angle

 

 

Figure 1.2 Feed and depth of cut [2]
5

1.1.2 GEOMETRY OF A SINGLE POINT CUTTING TOOL

A single-point cutting tool must accommodate not only for the primary motion but
also allow for feeding and Chip disposal. Therefore, the cutting edge is generally
inclined and the Chip is wound into a helix rather than a spiral. The tool iS relieved
both in the direction of feed and on the surface that touches the newly generated
surface, which originates major and minor flank surfaces respectively.
Intersections of these with the rake face constitute the major and minor cutting
edges. The nose is rounded with adequate radius. The rake angle Should be
really measured in a plane perpendicular to the major cutting edge. However, for

convenience, all angles are measured with respect to the major axes of the tool

 

 

 

(figure 1.3).
lLEdge cutting-edge angle
Minor cutting edge T
(/ Rake face SHANK
Nose radius ‘~~\\ I
"3]“ cutting edge \Side cutting-edge angle
Side rake angle (Trailing edge) . .

   

Rake face

_L__
( Flank
Back rake angle

.,,, -12

Side relief angle End relief
(clearance) angle

 

 

 

 

 

FIgure 1.3 Nomenclature for the geometry of single-point cutting tools [2]

1.2 PRINCIPAL FORMS OF TOOL WEAR

Several ways in which the tool life can be brought to an end are possible. They
may be classified into two main groups: the gradual and progressive wear at
certain regions such as the rake face and flank face of a cutting tool, and

catastrophic failures bringing the life of the tool to a premature end [3].

1.2.1 Typical wear of a single-point cutting tool

In figure 1.4, the progressive wear of the three most common cutting tools is
shown. Note the particular behavior of crater and flank wear of different type of
inserts [4]. In the same fashion, catastrophic failure is typical of the particular tool
material (figure 1.5).

Thermal cracks in

interrupted
Chamfer cutting

   

 

 

 

Carbide High-speed steel Ceramic

1. Flank wear (wear land) 4. Secondary groove (oxidation wear)
2. Crater wear 5. Outer metal chip notch
3. Primary groove or depth-of-cut 6. Inner chip notch

Figure 1.4 Progressive wear observed in the most common cutting tools [4]

Chamfer

 

 

High speed steel Ceramic
Thermal softening and plastic flow Chipping and fracture
1. Flank wear 4. Primary groove or depth-of-cut line
2. Crater wear 5. Outer metal Chip notch
3. Failure face 6. Plastic flow around failure face

Figure 1.5 Schematic illustrations of catastrophic tool failures [4]

1.2.2 Types of progressive wear in metal cutting

The progressive wear of a tool takes place in two distinct locations: wear on the
rake face characterized by the formation of a crater (thus called crater wear) and
resulting from the action of the chip flowing along the face, and wear on the flank
face (thus called flank wear) where a wear land is formed from the rubbing action
of the newly generated workpiece surface [3]. Figure 1.6 gives a typical diagram

for tool wear analysis.

 
 
   

Crater
wear

 

Workpiece

 

4.4-

Flank wear

Figure 1.6 Regions of tool wear in metal cutting [3]

Also, figure 1.7 sketches clearly the connection between the 30 view of the worn

tool and an auxiliary 20section (A-A) following the direction of the chip flow.

1 .2.3 Crater wear

The crater formed on the tool face conforms to the shape of the chip underside
and is restricted to the chip-tool contact area (figure. 1.6). In addition the region
adjacent to the cutting edge where sticking friction or a built-up edge (BUE)
occurs is protected, resulting in relatively slight wear. In experimental work the
maximum depth of the crater is used to measure the extent of crater wear and
can be determined by a surface-measuring instrument such as a profilometer [3].
At very-high-speed cutting conditions, crater wear is often the factor that
determines the tool life: cratering can become so serious that the tool edge

weakens and eventually fractures.

. Chlp flow direction
Chips in

edge of tool A

I Depth of cut -
Nose radius ‘1 ,"I’ / Crater

Wear on lhahulu wear in

 

 

 

 

 

 

 

 

flank I rake face
A
Cutting Groove at outer
edge edge of cut
Undeforrned Chip Ch'p
+1 thickness, t
I
Work : Crater depth
v i1 _______ __
Flank wear
“ma. Contact length
Tool
Cross section AA

Figure 1.7 Sketch of a worn tool during cutting [5]

10

1.2.4 Flank wear

The rubbing of the tool flank face with the freshly machined surface causes the
flank wear of a tool. Due to the rigidity of the workpiece, the worn area (flank
wear land) must be parallel to the resulting cutting direction. The width of the
wear land, which is accepted to measure the extent of flank wear, can be
detected with a toolmaker's microscope. When tools are used under normal
cutting conditions (economical conditions), the flank wear of a tool is usually the

controlling factor for tool life [3].

1.3 TOOL WEAR BEHAVIOR

The general relationship of tool wear versus cutting time is shown in figure 1.8.
Even though the relation is depicted for flank wear, a similar relationship occurs
for crater wear [7]. The curve can be divided into three regions: the region AB
where the Sharp cutting edge is quickly broken down and a finite wear is
established. This break-in period occurs within the first few minutes of cutting [1]
.The region BC progresses at steady-state rate, thus depicted with a straight line,
even though some deviations occur in actual machining. In the failure region CD,
wear occurs at a gradually increasing rate. In this region the wear begins to
accelerate and the general efficiency of the machining process is reduced. If the
machining process is allowed to continue, the tool finally fails by temperature
failure (plastic deformation and loss of the sharpen edge). Region CD is thought
to indicate the region where the wear of the cutting tool has become sensitive to

the increased tool temperatures caused by the presence of a wear land of large

11

proportions. Clearly, in practice it would be advisable to regrind the tool or to

replace the insert before the wear enters the failure region [3].

0.8

0.7
0.0

0.5

0.4
0.3

0.2

'ldth of flank wear land (VB), mm

I' Catastrophic

      

 

 

 

 

 

 

 

 

.. VB'T'J L." - / failure
' D
5 Initial U"'f°"“
breakdown wear
./ / rate
Rapid
.‘ I breakdown
jhu—u—r—l
0 50 100 150 200 4 250

Cutting time, sec.

Figure 1.8 Flank wear development with time(carbide tool at 1 m/s) [3]

1.4 TOOL-LIFE CRITERION AND TOOL LIFE

A tool-life criterion can be defined as the predetermined threshold value of a tool

wear measure or the occurrence of a catastrophic phenomenon. In the former,

which is a more convenient definition, a predetermined level of tool wear is

chosen so that when this level is reached the tool Should be replaced or

resharpened [3]. In the latter, the tool is operated until its failure occurs (final

points of the curves in fig 1.9). This criterion has the economical disadvantages

12

associated with resharpening the tool that failed or the workpiece finishing
quality.

Tool life is the cutting time required to reach a tool life criterion. In figure 1.9, a
value of 0.020 inches in flank is established as a tool life criterion and three

different tool lives are obtained for three different cutting Speeds

 

 

 

A Tool life criterion given
as flank wear level '
(”L (2) (3)
0.020 In
A = '

m v 400 I I
a l l '
3 l l '
3 I ' v= 200 I
.2 j V= 300 I
c l '
a ' '
- I I '
8 . '
.— . I
l l ‘ '

1T=5 I jT= 12 j j 1 I1T=41 y

10 20 30 4° 1

Time of cutting (min)

Figure 1.9 Effect of cutting speed on tool flank wear [1]

In practical machining operations flank and crater wear are not uniform along the
active cutting edge. Therefore, it is necessary to specify the locations and degree
of the wear when deciding on the extent of wear allowable before regrinding the
tool, that is the tool-life criterion. Figure 1.10 shows the typical measurements

recommended by ISO 5m Draft proposal [6].

13

  
 
 
  

A

Tool Face crater

!
!
I A

 

 

Section A-A

KB Crater width .
KT Maximum
crater depth
KM Position of
the maximum
crater depth VC
VB Average flank
wear land
VB max Maximum
Flank wear
Land

re. Corner radius View on major flank

 

 

 

 

Figure 1.10 Some features of a Single-point tool wear in turning [3]

1.5 TOOL WEAR MECHANISMS

Tool wear mechanisms may be Classified into two categories: mechanical and
chemical wear. Adhesive wear, abrasive wear, delamination wear and erosive
wear are examples of mechanical wear, while diffusion, dissolution and corrosive
wear are examples of chemical wear. In practical Situations, however, tool wear
may not be the result of one of these mechanisms acting independently, but a

combination of two or more of them.

14

1.5.1 Adhesive Wear

In adhesive wear the chip and the tool come close enough together to form
strong bonds. A particle transfer between the surfaces may take place if the
bonds are Stronger than the local strength. When this has happened several
times a wear particle may leave the system after loosened from the tool [7].
These small fragments can be carried away on the underside of the chip or in the
freshly generated surface (figure 1.11).

Adhesion wear is reduced at low cutting temperatures due to the lower adhesion.
At high temperatures the thermal softening behavior will diminish adhesion:
failure at high temperatures changes from within the tool to the interface or to
within the tool or chip. Adhesion wear may be most active at intermediate

temperatures [8].

Work material if 7 Work material

 

Figure 1.11 Adhesive wear representation

1.5.2 Abrasive wear

Abrasive wear occurs when hard particles on the underside of the chip slide
against the tool face and remove tool particles mechanically. The hard particles
on the chip may be formed by Strain-hardening processes), chemical reaction of
the wear debris, or may be hard constituents in the work material. Abrasive wear
depends on the relative hardness between the tool and the abrasive particles
and the distance cut. The harder the tool with respect to the abrasive particles
the lower the abrasive wear [3]. The extent of abrasive wear also depends on the
distance cut and can be described by Archard’s wear law [8]. This law States that
after some running-in period wear increases in proportion to cut distance.
Typically, abrasion occurs in two forms known as 2-body abrasion and 3-body
abrasion. In the former, hard inclusions in the chip penetrate and scratch the tool
surface; in the latter, the confined hard, inclusions roll and Slide on rake face of
the tool scraping out tool material. In figure 1.12 the two types of abrasive wear

are represented.

2-Body abrasion 3-Body abrasion

 

Figure 1.12 Two body and three body abrasion

16

1.5.3 Diffusion wear

The diffusion mechanism in solid state is the transportation of atoms from regions
of high atomic concentration to regions of lower concentration within a crystal
lattice. The local temperature controls the diffusion process and the diffusion rate
increases exponentially with temperature [3]. Furthermore, the diffusional
transport depends on the chemistry and stmcture of the materials, temperature,
time, and the concentration gradient of the diffusing Species [7]. In metal cutting,
atoms move from the tool face to the chip. The continuous diffusion of atoms
from the tool into the chip will weaken the surface structure of the tool in a very
narrow reaction zone. [7] Chemical decomposition of a component of one of the
sliding surfaces usually accompanies diffusion wear. This may increase the wear
rate if the new component has strong affinity with the Chip. In figure 1.13 a model
of diffusion wear proposed by Naerheim and Trent [9] is shown. This model
proposed that the wear rates of both WC-(T i, Ta,W)C-Co(P-grade) cemented
carbides are controlled by the rate of diffusion on Tungsten (and TI and Ta) and
carbon atoms together into steel.

The existence of the diffusion mechanism has been questioned but no
categorical findings have been reported. However, if the mechanism exists at all,
it contributes significantly at very high cutting speeds (beyond the normal cutting

conditions) [10].

17

  
  
 

   

-. “.‘..Fe+.C.M

. .

      

      
 

 
    

. - _- Chi flow .
-"-.-.-L=~.':.-':§' Fe W030i}; iCHIPE :‘-.W.T|,Ta.C WITLTHIC F 55 '
E ' ' cIIlIcJ ”I" ' 1 3-‘531‘J'3-‘i--'!'-'-"'-'-'.':.:::-7-"'":"-II':’ H
o I '
,_

WC-(I'I,Ta,W)C-Co cemented

WC-Co cemented carbides
carbide tools

Figure 1.13 Model of diffusion wear after Naherrnein and Trent [8]

1.5.4 Dissolution wear

This tool wear mechanism has been accepted in the last decade to influence
crater wear, especially at high speeds [11]. Thermodynamical instability at high
temperatures during machining causes the tool material to dissolve into the chip.
Kramer and Suh [12] showed an outstanding correlation between wear predicted
theoretically and those obtained in experiments. They consider crater wear as an

equilibrium process of dissolution. A thermodynamical potential was considered

for the solution of the tool material in the work material. This approach was

completely opposite to that of thermal diffusion, known to be a non-equilibrium

process and at that time was widely accepted as the main cause of crater wear.

18

Kramer and Suh [12], also proved that diffusion kinetics were relatively slow at

normal cutting Speeds.

1.6 COATED CUTTING TOOLS

At present, various estimates indicate that approximately 80 % of the cutting
tools have a certain type of surface coating, and with a continuing growth trend
[8]. The popularity of coated tools resides in the enhanced tool life that a surface
coating can provide

This ability to resist wear comes from the concurrence of wear-resistant
properties of both, the coating and the substrate. In general, coated cutting tools
have a ceramic coating layer that provides excellent tribological properties and
the cemented carbide or high-Speed steel substrate that provides toughness.
Moreover, coated tools must meet another requirement, compatibility between
coating and substrate [10]. It follows then, that coatings and substrate must
posses some desirable properties. In order to accomplish a good performance,
coating layers must have: high hardnesseS at high as well as low temperatures,
good chemical stability, a porosity-free surface, posses a low coefficient of
friction with respect to the materials machined, a good adhesion to the substrate,
high productivity [13]. On the other hand, a substrate must posses: a good
toughness, high hardness, compatible chemical composition respect to the
coating, good thermal characteristics to withstand high temperature deposition, a
coefficient of dilatation comparable to that of the coating, and good thermal

conductivity.

19

The principal effect of the coatings is to serve as a diffusion barrier of tungsten in
carbide tools. This will reduce the cutting temperatures by decreasing the friction
coefficient and thereby reducing the cutting forces on the face of the tool. [14].
Coatings are made to be extremely hard and resistant to abrasion, hence they
are not easily removed. Tool life is Significantly increased by the lower
temperature operations [15-17]. Cutting conditions and substrate properties play
a main role in the increased tool life of coated carbides [14]. Early disintegration
of coatings, as a result of thermal softening and plastic flow, are common at high
speeds and especially with High Speed Steels (HSS) substrates. Nevertheless, it
has been reported that “under less severe conditions of lower feed rate, the
ceramic coating can give a cutting life often times that of the uncoated tool [18]”.
For cemented carbide substrates, the tool wear is decreased as the hardness of
substrate increases, because deformation of the cutting edge is smaller in a hard

substrate [1 9].

20

Chapter 2 : INTRODUCTION TO ADVANCED MICROSCOPY

In the second half of the twentieth century, the convergence and integration of
developments in optics, computer science, electronics, materials science, and
molecular biology contributed greatly to huge improvements in microscopy. Non-
destructive, non-invasive, and high-resolution imaging are some of the most
important virtues of the new advanced microscopy. The most common
technologies used in advanced microscopy include: Confocal Laser Scanning
Microscopy (CLSM), Scanning Electron Microscopy (SEM), Transmission
Electron Microscopy (T EM), Atomic Force Microscopy (AFM), and Scanning
Tunneling Microscopy (STM).

In particular, CLSM possesses three remarkable characteristics. First, most
confocal systems are capable of both confocal and conventional imaging.
Second, the CLSM lateral resolution obtainable is approximately 170 nm, which
is somewhere in between the resolution of a conventional light microscope (at
200nm) and an electron microscope (at 3-6nm) [20]; besides that, the depth
resolution (3dB depth response) of a CLSM is approximately three times better
than that of an SEM [21]. . Third, the CLSM is inexpensive when compared to the

scanning electron microscope or other microscopes with similar technology.

21

2.1 MICROSCOPY BASIC DEFINITIONS

Many of the design principles of the confocal microscope are based upon the
conventional light microscope [21], which is relatively simple when compared to
the other systems used in advanced microscopy. Thus, a natural way to get
acquainted with microscopy terminology is to begin with conventional microscopy

terms.

2.1.1 Field of View

The field of View (FOV) is the diameter of the Circle of light that can be seen

when looking into a microscope. AS magnification grows the FOV decreases [22].

2.1.2 Resolution

Generally speaking resolution is the ability of a system, or of a component, to
distinguish fine detail. Two different types of resolution are commonly needed:
transversal and depth resolution. Transversal resolution is usually defined as the
smallest distance between two points in a plane parallel to the focal plane, which
can be regarded as two different entities [20,23]. Whereas, depth resolution (dz)
iS defined as the distance in the optical axis between half-power points (3-dB
points) of the intensity response (figure 2.1) and is given by the approximate

formula:

0.89/1
(N.A.)2 ...(2.1)

 

dz(3dB) z

22

Where, it is the wavelength of the light source and NA. is the numerical aperture

of the objective

 

Intensity

 

 

 

 

 

-3 -2. 31 o 1 5 3
Defocus position (nicrons)

Figure 2.1 Depth resolution using a BOX/0.90 objective in air at A=633 nm [21]

In confocal microscopy, the definition of resolution largely depends on the type
of sample and which measurements are important to the observer. When
imaging integrated Circuits, for example, height differences of planar surfaces
and the profiles of structures are the features of interest, then, depth
discrimination and edge response are relevant to define resolution. In biological
science, a depth-resolution definition based on point reflectors is more adequate
to characterize the scattering from individual cells. Also, for biological samples is
better to define transverse resolution with the idea of two close points being

distinguished.

23

2.1.3 Magnification

Magnification represents how many times the primary image of the object is
enlarged to become the final image. The magnification defines the size of the
image at the detector. The total magnification in a microscope is a compound
quantity. Each lens in the light path will increase or decrease the image. In the
schematic shown in figure 2.2, the objective lens and the eyepiece will give their
independent magnification to modify the final value of magnification. The

magnification in the transverse direction for a Simple lens (objective lens) is given

_ — d5
MT _ A ...(2.2)

Where d, is the tube length (the distance of the intermediate image plane from

by:

the back focal plane of the objective), do the distance of the sample object from
the front focal plane of the objective. The negative Sign accounts for the image
inversion produced by a simple lens. Also, the longitudinal magnification comes

as the square of the transverse magnification:

2
ML " —MT ................................... (2.3)

. The eyepiece magnification is defined as the ratio of the size of the retinal

image as seen through the instrument to the Size of the retinal image as seen by

24

the unaided eye at a normal Viewing distance 01250 mm [24]. The formula used

to determine the eyepiece magnification is:

ME = 250m% ...(2.4)

Where f stands for the focal length of the eyepiece lens. Finally, the total

magnification of the system, MR, will be given by:

MR = MTME ...(2.5)

2.1.4 Numerical Aperture (N.A.)

The numerical aperture (NA) determines the resolution and light-gathering ability

of the objective lens. Mathematically, the NA is expressed by the relationship:

_ :1: °
N .A. — n s1n I90 ...(2.6)
Where It, is the refractive index of the medium between the lens and the sample,

and 9 0 represents half the angle subtended by the lens at its focus (figure 2.2).

25

 

illumination

,/ "‘"":l Incoherent

 

 

57/7, ' ././/3 Sample 4 3

. : \ ‘7
I II
Virtual Image I

 

 

 

 

Figure 2.2 Simplified schematic of a conventional light microscope [21]

2.1.5 Objective Lens, focal plane, and depth of field

The objective lens is the most fundamental component for a light microscope. A
basic understanding of it can be of capital importance to comprehend the way a

CLSM works. In figure 2.3 a scheme of the front of an objective lens and the

26

entities it defines. First, we have the focal plane, defined as the region in which
the parts of the sample appear Sharp and distinct, “on focus” [23]. This region
can be imagined as a finite Slab perpendicular to the axis of the objective.
Second, we can differentiate the focal distance as the distance between the
objective front lens and the top of the focal plane. Finally, the thickness of the
focal plane is defined as the depth of field.

OBJECTIVE

   

SYMMETRY AXIS

    
    

OBJECTIV
- ‘ SAMPLE

 

FOCAL PLANE

I

\
FOCAL

    

DEPTH OF

 

w DISTANCE
FIELD

Figure 2.3 Illustration of the objective lens and the focal plane

2.2 CONFOCAL LASER SCANNING MICROSCOPY (CLSM)

The major advantage of the CLSM over a conventional light microscope is that,
only light coming from the focal plane is detected, whereas light coming from the
focal plane (out-of-focus light) is blocked. This is the origin of What iS called an
optical slice, which brings considerable improvement in the resolution respect to
the conventional microscope. The improvement comes as a result of blocking the

out-of-focus light, which causes the image blurring in conventional microscopy. In
27

the research field, confocal microscopy is known to be a valuable tool for
obtaining high-resolution images and 3—D reconstructions of a variety of
biological as well as material science Specimens [25]. The Laser Scanning
Confocal Microscope (CLSM) uses a laser beam as an illuminating source. This
laser beam scans across the specimen by means of an x-y mechanism. With the
confocal principle an image of a specific plane of the sample can be produced.
This is the fundamental difference between a conventional light microscope and

a confocal one.

2.2.1 The confocal principle

The power of the CLSM resides in its ability to get an image only from the light in
the focal plane. This means that all the out-of-focus light is blocked from the final
image allowing a Sharper image compared to the conventional light microscope.
This feature is achieved by positioning a detector pinhole in light path. Light that
is exclusively coming from the focal plane is focused at a point right in the
position of the pinhole (figure 2.4). Thus, the pinhole only allows the light coming
from the focal plane to go through directly to a detector on the other side of the
pinhole. Light rays originally coming from out-of-focus regions have a focal point
either in front or behind the pinhole, therefore, few of these rays make their way
through the pinhole. As a consequence, the image is formed mostly by rays
coming from the region of the sample located in the focal plane. This process
provided the birth to the concept of optical section. An optical section can be
better understood as a slice of the sample coinciding with the focal plane level.

The advantage is that an actual sectioning was not necessary to perform, the

28

sample remains intact and repetition of the process can be done. Once light of
the region not in focus has been discarded in the final image, resolution and
contrast are drastically improved respect to the conventional light microscopes.

Figure 2.4 shows the confocal principle while figure .25 shows a typical CLSM

 

 

 

 

 

 

system.
LIGHT
SOURCE
(LASER)
f MIRROR DICHROIC
(Beam splitter)
IT| PHOTODETECTOR
COLLECTING (PHOTWUIJIPUER)
LENS ‘

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

 

 

     

 

 

OBJECT'VE LENS DETECTOR PINHOLE To

(Confocal aperture) DISPLAY
SCREEN

.-.-....-.-._ .t._ .-.-.-<.::_.—.. .

 

FOCAL PLANE or OPTICAL
ECTION (In focus region)

 

4 IN-FOCUS LIGHT RAYS
. .. . . .. F°°"s OUT-OF-FOCUS LIGHT
. m. m‘...".~.u.......‘._.._... 'fr'; 1 ---------- RAYS

 

 

 

Out-of —focus region

 

Figure 2.4 The confocal principle

29

A

 

CONFOCAL
UNIT

CONV. LIGHT
HOROSCOPE

I l

 

 

PHOTOMULTIPLIER

 

1

 

/.

REJECTION

 

 

I FILTER

, DETECTION
PINHOLE

ILLUMINATION
PINHOLE

   
 

 

EXCITATION
FILTER

 

 

 

   
    

 

Specimen

 

OBJECTIVE

FOCUS
MOTOR

 

    

4—>
STAGE

 

  

 
 

FRAME
BUFFER
CONTROL
ELECTRONIC ,

 

STORAGE
(e.g.,Hard
Disk, Optical
Disk. MPG)

 

 

 

OUTPUT

 

 

 

 

(e.g.,Laser
printer, Dye
subprlnter,

 

 

WORKSTATION
3D

ECONSTRUCTION

Figure 2.5 A typical Laser Scanning Confocal system [25]

30

2.2.2 Operations in the CLSM

Most operations in the CLSM can be achieved due to the motorized stage and
the x-y movement of the laser beam. The motorized stage is usually able to
move axially (z) with its position controlled by the microscope software. Some
models also allow the stage to move in the transverse direction (x-y), this feature

could be use to artificially increase the FOV and consequently the sampling area.

2.2.2. 1 Z-series

The optical sections collected through a specimen conform a series of 20
grayscale images that are the usual data a CLSM can provide. This optical
sections series are referred as Z-stack (figure 2.6). The optical slices in this 2-
taCk could be electronically overlaid to produce an extended focus image, or the
signal intensity information can be manipulated to produce a 3D display
(IOPOQraPhYI-

When overlaying the optical slices, the user must decide beforehand the Size of
the image to be obtained, the number of optical sections and the vertical distance
between two consecutive optical sections (Z-Step Size). The relevance of these
three factors in the 3D size of the z-stack not only is related to storage space and
availability, but also has subtle effects over the processing, display and control of
this data [25]. Z-Step Size selection is a critical issue that includes the thickness
of the sample to be imaged, the focusing movement and the resolving power of
the objective lens. Here, the fineness of the stage movement is of capital

importance, as this will dictate the lower limit for the z-step.

31

2.2.2.2 Phi -Z Sectioning

A phi-z section is an optical section taken in the vertical plane (parallel to the
optical axis) rather than in the usual horizontal plane. To accomplish this in a
CLSM, the beam is scanned repeatedly across a single line defined by the
operator. Each scan will take place at a level deeper than the previous one until
the total depth is reached. The total depth of the phi-z section depends on the
on-screen magnification, whereas its thickness depends on the Size of the laser

spot (figure 2.7), which iS in turn controlled by the NA of the objective.

2.2.2.3 3D reconstruction (Topography)

3D-reconstruction is most complex among the LSM’S special features, which
allows to obtain the surface topography for materials science samples and signal
intensity variations in the case biological-fluorescent images.

The results of a z-series are the intensity as a function of pixel position (x,y) and
slice depth (2), i.e. l(x,y,z). For each pixel position (x,y), intensity is also a functi
The intensity normally peaks at the surface. In figure 2.8 the intensity profile is
represented over 2 at three points (x1, x2, x3, on a step-shaped surface. The
positions of maximum intensity (Zm) of these curves, corresponds to the 2 value
of the surface at this pixel location. AS the intensity curve can vary with geometry
and material of the specimen, the software usually offers three methods of
determining the 2 value for the surface. By determining the coordinate of:

02..., the gravitational center of the curve l(xo,yo, z )

ii)zmam the maximum of the curve l(xo,yo, z)

iii)z1,m the first maximum of the curve l(xo,yo, z )

32

Mostly, the values obtained with the three methods will be very close, as in figure
2.9(a), where zSp =2...am =szax, . Sometimes the results can differ greatly as it is
the case in figure 2.9(b). The functions contained in the topography software
allow to obtain a 2 surface coordinate for each pixel (x,y), which is in most cases
a good representation of the specimen surface. This is stored in a matrix called
the z-matrix (z(x,y)). Additionally, the intensity maxima at each (x,y) pixel iS
calculated and stored in the intensity matrix l(x,y).

Different types of rendering are available in addition to the topographic View
itself. Z-maps, contour lines (isolines), relief images, volume determinations,
statistical parameters (height and gradient histograms), and roughness
parameters such as transition profile (tp), maximum peak to valley height (Ra),
and average height (Zm) are possible with the confocal software [23]. Figure 2.10
shows a Simple schematic showing the way in which topography is rendered. 3D
reconstructions are obtained using the information stored during the gathering of

the Z-stack.

 

Computer rendering of
optical section 1

 

 

flOptical

// section 1

1 Optical
section 2

 

  
  
 
   

Optical
section 3

.22... 3 2.. ...

 

Computer rendering of
optical section 2

Optical section 1
E]?1 A .
OptiCal section 2 Z-stack

SAMPLE
(2D View)

  

Computer rendering of
optical section 3

 

.. focus zones
|:| Out-of-focus zones

Figure 2.6 Z-stack computer rendering of a Simplified sample

Phi-Z section
thickness [-

 

   
   

 

 

Computer rendering of , , . . . - .7 g,
the Phi-Z section SAMPLE (3D View)

Figure 2.7 Simplified schematic of a phi-z section

 

 

 

 

 

 

 

 

 

 

.fl.
X1 X2
zm
Zm
Zm
I (x1iz) I (X242) I (x3,z)

Figure 2.8 Intensity profiles and its relation to surface position

35

' (memz)

\ fl\:

I (meotz)

 

I

21 .mx zsp 2m 2

Figure 2.9 Intensity profiles shapes

1“

3D reconstruction SAMPLE
(Topography)

 

Figure 2.10 Simplified rendering of a 3D reconstruction
36

2.3 THE SCANNING ELECTRON MICROSCOPE (SEM)

In this apparatus an object is scanned in high vacuum by'a concentrated electron
beam. The image is obtained out of the collection of secondary or backscattered
electrons form the sample in the spot where the electron beam strikes. Because
the number of collected electrons is dependent on the nature of the material and
its geometry, images with excellent geometrical detail are acquired.

The SEM has a better transversal resolution than a CLSM for the diffraction
wavelength of an electron beam is as small as 0.04 nm. In practice, however, the
resolution of an SEM is diminished by aberrations caused by electron scattering
and other artifacts. Practical SEM resolutions usually range from 3 to 6 nm [20].
Another advantage of the SEM is the possibility of attaching an energy dispersive
x-ray spectroscopy system (EDS system). This powerful tool allocates for the
chemical element identification and quantification.

Although SEM electron beams have extremely short wavelengths, the NA
aperture is particularly small. This results in SEM images remaining in focus for a
large range of working distances and permanent 3D appearance, which doesn’t
allow for depth information to be extracted. Furthermore, The vacuum needed for
SEM operation makes this microscope extremely expensive. In figure 2.11 a

schematic representation of a typical SEM is rendered.

37

 

 

 

 

 

 

 

 

 

 

§ Scan nerator
Deflecting coils\ § l ”MM/I l___

\
i111§ (I'I'I Probe forming lens

 

 

 

Sample Collector WW”
Secondary electrons

Figure 2.11 Simplified schematic of a SEM [21]

2.4 THE ATOMIC FORCE MICROSCOPE (AFM)

The principle of Operation of an Atomic Force Microscope (AFM) consists of a
fine ceramic or semiconductor tip scanning the surface of the sample, resembling
the scanning of a needle in a phonograph (figure 2.12). The tip is located at the
end of a cantilever beam, which deflects according to the force of interaction with
the surface. This force is measured by the deflection of a light beam that is
reflected from the upper side of the cantilever beam and impinging on a detector,
which determines the position of the cantilever. There are two modes in which an

AFM can operate depending on the way the tip interacts with the surface. If the

38

tip touches the surface during the whole scanning, the contact mode is being
used, while in tapping mode tip only taps across the surface being tested.

A major advantage of the AFM is its usefulness when profiling a surface. The fact
that the tip is actually “touching” the surface makes the AFM a very reliable and
accurate tool for estimating the surface topography [21]. Typical transverse
resolution for AFM falls Within 0.1 nm and 1 pm, and depth resolution has an
average value of 0.5 nm. Despite its high resolution the AFM has been proved to
have some drawbacks due to the relatively Slow scan, very small space of probe

to sample, difficulty to use in deep holes, and easiness for a tip to be damaged.

     
    
   

Laser

beam Controller

Cantilever and point probe
Sample

30 piezoelectric
positioner

  

- Scan generator

' Video display

Figure 2.12 Schematic of the AFM principle of operation [21]

39

Chapter 3 : STATEMENT OF THE PROBLEM

3.1 LITERATURE REVIEW ON SURFACE TOPOGRAPHY

Surface evaluation, in particular surface topography, plays a prominent role in the
analysis of wear because it supplies information about the local mechanisms that
have been operating, their magnitude and their contribution to the overall wear
rate [26]. In order to perform a micro level analysis of the wear in cutting inserts,
an accurate 2D and 3D images as well as measurements are needed. These
images and measurements should be able to Show how the wear evolves to
delineate local information on wear.

So far, the traditional methods used to quantify tool wear have included reflected
light interference microscopy [27], scanning electron microscopy, and stereo
microscopy. But due to the limitation on the depth of field, the difficulty while
obtaining and interpreting images, and the high cost involved, [28] these methods
have proven to be burdensome and time-consuming [26]. Also, conventional
methods of surface measurement have involved stylus profilometers. However,
this method has a number of disadvantages such as the limitations on the detail
they can resolve, the slow scanning rate, and the potential damage to the surface
investigated. Additionally, when using stylus profilometers. severe difficulties
arise for the gathering of 3D data sets from surfaces [28].

Confocal laser scanning microscopy (CLSM) and its variants arise as an exciting
new development in the field of microscopy with the potential to revolutionize
surface analysis. Among the capabilities of CLSM are the fast and convenient

recording of surface features and the determination and analysis of the true

40

surface topography. These capabilities provide the unique characteristics of the
CLSM such as increased depth of field, minimal sample preparation, and
adequate image quality for engineering purposes, and savings in costs relative to
SEM technology. Further, CLSM measurement technology facilitates the use of

new surface parameters that add to the traditional ones [28].

3.2 LITERATURE REVIEW ON CLSM APPLICATIONS

Since the commercial introduction of the CLSM in the early 80’s, this microscope
has been established as a powerful tool in biological and medical sciences.
However, its use in tribological and metallurgical fields has been exceedingly
limited [29]. Reflection CLSM, as stated by Wessel et al [30] is an
underestimated quantitative, topographic imaging tool and a real alternative
compared to SEM and AFM

During the past few years some comparative studies on the perionnance of
traditional methods versus CLSM have been carried out in wear measurement,
tribology, fractography, and biomedical sciences.

Anamalay et al, [28] compared surface parameters of three surfaces with
different machining finish using CLSM techniques and conventional profilometer
methods. They concluded that the use of a CLSM helps to avoid the
profilometer‘s limitations of accuracy that originate from the size of the Stylus.
Such limitations are not found in a CLSM as long as objective lenses with

suitable NA’S are used.

41

In their tribological research of rolling-sliding wear surfaces of cast iron, Hanlon
et al. [29] found a very good agreement between the results obtained by a CLSM
and by an AFM, when profiling the worn surfaces. This implies that the CLSM
technology provides an accurate reproduction of the surface geometry. The
correction for tilting and the elimination of signal noise were the core part of the
data post processing in this study.

Gee and McCormick [26] used a Confocal Scanning Microscope (COM) for the
examination of worn alumina (Al203) surfaces. In this study, a previous
comparison between profiles made by a diamond stylus profile and a COM on a
glass was performed. The COM profiles presented a better response than the
profile measurements system. Besides that, the COM proved to give better
contrast than conventional optical microscopes for the alumina specimen, and to
be particularly useful for the measurement of the topography of the alumina wear
surfaces.

Wessel et al, [30] made a comparative work on the imaging of human hair and
concluded that the precision of a reflection CLSM profile measurement of small
structures depends much on the geometry and the optical properties of the
investigated object. In addition, they suggested that for a good validation of

height resolution the use of an AFM was essential.

3.3 RESEARCH FOCUS

Most of the work published regarding 3D tool wear characterization is related to

the traditional methods of white light interferometry [27,31] or contact profilometry

42

[32]. Publications on tool wear (crater and flank wear) being analyzed with CLSM
are rarely found. This is especially true when it comes to single and multi-layer
coated carbides.

The difference in optical properties between coatings and substrate and the lack
of previous CLSM-based works, make the CLSM wear imaging very challenging.
On the other hand, the desirable capabilities of CLSM for profiling, height
discrimination, and 3D-topographical reconstruction represent a real possibility
for accurate tool wear characterization.

The focus of this study is to obtain a confocal 3D (topographical representation of
the wear evolution of multi-layer cutting inserts, as well as the confocal profiles in

specific locations .The measure of wear descriptors is also considered.

Chapter 4 : EXPERIMENTAL WORK

4.1 MACHINING EXPERIMENTS

The experimental work was performed at the Physics Shop facility of the
Biomedical Physical Sciences Building at Michigan State University. The
machine used was 8033 Clausing /Colchester lathe (figure. 4.1). This lathe
allows for cutting speed to be set and programmable feed and depth of cut. This
lathe was well suited for the experiments since the revolutions per minute (RPM)

could be controlled in order to maintain the cutting Speed constant.

 

Figure 4.1 Clausing/Colchester variable speed lathe( Model 8033)

44

4.1.1 Machining conditions

The experiments were run in dry at the constant feed of 0.3175 mm/ rev (0.0125
inch/rev), depth of cut of 1.905 mm (0.075 inch), cutting Speed of 250 m/min (820
Sfpm). This cutting speed was specifically chosen following three criteria: The
range of optimal speeds provided by the insert manufacturer’s, the need for
obtaining as much measurable wear as possible in the shortest time, and the
torque limits of the lathe. Similarly, the feed and depth were selected following
manufacturer’s suggestions. In addition other aspects of the experiment were
also considered, which are minimal chattering, good surface finishing and optimal
area size for imaging. After few trial mns the approach angle was set to 5
degrees and the tool-holder Shank was machined to provide a back rake angle of
2°. These angles set a compromise between minimal chattering and proximity to
orthogonal cutting conditions. Machining times were interrupted at: 60 s, 120 s,
180 s, 240 s, 300 s, 480 s and 720 S. in order to obtain a cutting edge at each of
these times. Thus, allowing for the wear evolution to be observed as a function of
time. Table employed 4.1 Shows the comers and inserts in relation with the
machining time. The alternation in the comers was designed in order to avoid the
temperature influence over the results when machining comers of the same
insert consecutively. The comers with machining times of 10 S and 30 S were
discarded because the wear on them was not measurable with the confocal

microscope.

45

4.1.2 Work material

Steel rounded bars of AlSl 1045 steel were purchased from ALRO Steel, Inc.,
Lansing, MI, and used as work material. The size of the bar stocks were of 6”

diameter and 18” length.

Table 4-1 Inserts and corners used in the experiments

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

m I D‘ m l 0‘ , E ! 1
G ‘ OJ C ‘ PJ L ‘ VJ
INSERT 1 INSERT 2 INSERT 3
INSERT NUMBER CORNER MACHINING TIME

1 A 480 S (failed)

2 M 300 s

1 B 240 s

2 N 180 s

1 C 120 s

2 P 60 s

1 D 30 S (discarded)

2 Q 10 s (discarded)

3 Z 480 s

3 V 720 s

 

 

 

 

 

4.1.3 Inserts and toolholder used in the experiments

The inserts for the experiments were provided by Kennametal, lnc., Latrobe, PA,
and had a SNMA 190612 ISO designation (ANSI Catalog # SNMA643). The
toolholder was purchased from Production Tool Supply, Lansing, MI; and had the
designation MSRNRi 6-60. Figure 4.2 displays the mounting of the insert,
toolholder and chipbreaker. Figure 4.3 shows the insert geometry as provided by

Kennametal.

CHIPBREAKER

N\
TOOLHOLDER . ,

 

Figure 4.2 Insert and toolholder arrangement

47

 

 

 

 

Figure 4.3 Geometry of a the SNMA 643 insert [35]

Table 4-2 Geometrical dimensions of the SNMA 643 insert [35]

 

4.1.4 Coating materials and substrate

The multi-layer insert was provided by Kennametal as a KCQ315 grade insert.
The top layer was made of Titanium Nitride (TiN), followed by the layer of
Aluminum oxide (Al203), which in turn was above the Titanium carbonitride
(T iCN) layer. As technical information on thickness of layers was not provided, a
section of the insert was obtained using an Electrical Discharge Machine (EDS)
and the thickness of each layer was obtained using a Zeiss LSM 210 confocal
microscope in reflective mode (figure 4.4). TiN thickness was found to be 2.5 pm,

Al203 7.1 pm, and TiCN 7.8 pm. The substrate was C6 grade cemented carbide.

2::ii‘igO
O

    

i if. _ I a~v- 9 I.

_ - ,_ ~ ' l‘ ' 2'.- ”a e' '
.91 4:2,...) ‘ pa “
’2‘... :. ..ubstraie) {a}; i; . ,1»? ”‘i A? "
1"‘i‘l.g't.e.. 0‘ I “A" ‘ J: .. . '4'.

' ..;“‘!I“ 9 .ie..’."; q 3“. ..- .'.'.|";::-’:\‘.“ ~
"g. T ' . . '. a t ‘ ‘i I Ir r"§‘ ‘ if. .. ' I I‘fi'.’ T 1
£1.33.“ et"::_-" 2:3 :43 41.1,", 91-.
31 ‘H . i .7 ‘i'T‘T1"-:" ‘Ihr‘ 'J‘ . a '.i'.
5"." “OJ ‘ ’ _ . '0 “

     
 

‘1" a.

Figure 4.4 Reflection confocal image of the multi-layer insert cross section

49

4.2 CONFOCAL MICROSCOPY DATA ACQUISITION
Confocal microscopy data acquisition was done on a Zeiss LSM 210 (figure 4.5)

at the Center for Advanced Microscopy at Michigan State University

 

Figure 4.5 Zeiss LSM 210 confocal microscope

The following are the procedures and methodologies used for the confocal
images. As a general rule, before starting the final gathering in each mode, many
attempts were performed to optimize the acquisition parameters for the insert

materials.

50

4.2.1 Crater 2D images

2D images were obtained in reflective mode using the Zeiss LSM 210 confocal

microscope. The laser line used was the Argon-488 laser (L488 in micrographs

legend bar) at 100% power. A 5X objective and a default screen zoom of 20 were

selected, for convenience in capturing the whole area of the crater. Provided that

each session was started in the light conventional mode with focusing the

oculars, the steps followed during the gathering of the images were as follows:

Perform a coarse alignment by positioning of the insert on the stage using
the left inferior comer of the glass slide as a reference.

Focus on the unwom zone of the specimen using the conventional
reflective mode of the microscope.

Move the center of the ocular so that the whole worn zone can be
captured in the field of view (FOV).

Change to confocal reflective mode and optimize the contrast and
brightness with the color range indicator. During the optimization of
parameters, it was found that keeping the brightness fixed at 400 (B=400),
the contrast for optimal image ranged within 0:40 to 0:62.

Proceed with the fine alignment. The distance function of the measure
menu in the microscope software was used to define horizontal and
vertical references for the edges of the insert. Figure 4.6 shows the

position and values of theses references.

51

"’i"

Xr = 383.7um
r = 202.3pm

. 5"
. _ _,.,.

a,» _

'_ ran _ - ar'Jfl
.' I. JI
‘2 II 3:-

. l
. 2i“: .. 32:5
.’~' 53.,

 

Figure 4.6 References for alignment in the LSM 210 pictures

Store the image in the LSM 210 hard disk in PIC format.

0 Transfer of files to a LSM 310 software for file format conversion (PIC to
TIFF format) of the pictures files. PIC files cannot be read by most of the
image processing software, while TIFF files can be easily recognized by

most imaging software.

4.2.2 Topographical 3D images of crater wear

Crater wear topographical images of all the comers were obtained by means of
the advanced three-dimensional reconstruction feature provided in the LSM210
software. The optimization of parameters for this part involved multiple trials with
the four different lasers (He-Ne A =633nm, Argon 2. = 488-514 nm, Argon 1:488,

52

and Argon A = 514 ) proofs with the digital filters (lowpass and highpass filters),
z—step values , and number of sections involved. Optimal parameters for the
topographical images were set as follows: 5X objective, L488 (Argon) laser line
at 100% of the power (F0), contrast of 150, brightness of 405, z-step value of
49700nm, and 2 optical sections. Due to the difference in optical properties of
the tool materials, the gravitational center of the intensity curve was chosen as
the method for determining the 2 surface coordinates. Then, the LSM 210
software produced a 2 surface coordinate for x,y each pixel, that is , the z- (x,y)
matrix.

The sequence of steps for the gathering was identical to that used for the 20
images in section 4.2.1 until reaching the fine alignment step. After that, the
topography reconstruction required its own steps:

. Change contrast and brightness to 150 and 405

. Follow the sequence of buttons needed for surface reconstruction.

. Store the z-matrix in the hard disk (TOP format file)

0 Transfer of the z-matrix to the LSM 310 software for post-processing and
conversion of the TOP files to TIFF format.

. First post-processing to obtain: two SD views (left and front orientation)
and isolines view. For this post processing the optimal parameters were
found to be: Height: 62, Lowpass filter (Kemel=1), and D/p.m=60-80
(isolines function).

0 Store the SD views and isolines in a TIFF format

53

. Editing and 2nd post-processing in Adobe Photoshop 7.0 to obtain the

final 30 topographical views.

The shape of the crater wear was verified in the early stages of the research
using a replica of a worn corner. This comer was previously used to machine a
1045 steel at 660 sfpm, 0.356 mm/rev feed and 1.905 mm depth of cut. Vynil
Poxysiloxane, an impression material used in dental care, was used to make the
replica. Before doing the imaging in the LSM 210, the replica was coated with

gold to assure uniform optical properties in the worn area.

4.2.3 Maximum crater depth values and locations

The determination of the maximum depth location in each comer was a crucial
task. For one thing, the time evolution series for crater and flank wear were done
in the maximum depth locations. Due to this relevance and the limitations of the
microscope software to provide for an automated method, the search for the

maximum depth in each comer was done using three different methods.

Visual Inspection method

The visual inspection method consists of finding the darkest point in the crater
through visual inspection of the 20 confocal image of the corner and defining its
location respect to the edges of the insert. This method is fast to perform and is
based on the common optical idea that deeper points correspond to darker
points. However, this method has consistency problems as human error is

definitely introduced.

54

Method of Inspection using the Matlab imaging tool

The semi-automatic method made possible to obtain a grayscale-value map of all
the pixels in the image. The imaging tool of a Matlab 6.5 version was used to
perform this task. The grayscale value (0255) of any pixel in the image could be
obtained just by positioning the cursor in a location. Once the pixel with the
lowest gray scale value (maximum depth location) was found by inspection, the
position of the pixel was defined respect to the edges of the tool. This method
can diminish human error due to visual inspection because a numerical value

(grayscale value) is used to find the darkest point.

Five-sections method

In the aim of automating and improving consistency, a search technique was
outlined. This technique consisted in obtaining five equally spaced orthogonal
sections out of the area that contained the maximum depth location. Then, the
section that possessed the maximum crater depth was selected as the possible
maximum-depth section. This method was used for the left-view and front view

orientations. Figures 4.7a and 4.7b illustrate the method.

55

o , 0 ,
if 2,322.

a“!
‘33:? .

h: "
98’ rug“

0 0
315:“?

0.?

Area containing the maximum
crater depth location

 

Sect. 2(Left) '

--

-"—_"¢-I-LI.

. -.
,-. «4.5-M '

a: _ , -,
" j Sect. 5(Left) :2
" ' . . a 'r u .

—-—-qu-/. Sect. 1(Lefl)

 

HI
.5
I

Sect. 2(Front)
Sect. 3(Front)
Sect. 4(Front)

Sect. 5(Front)

Figure 4.7 (a), (b) Five sections method (Isolines view)

56

The position of the orthogonal sections having a left view orientation (Figure 4.5),

respect to the right side of the image was calculated using:

(m-n)
X-= ——————1 12X-
J "+ 50 [+ z] ...(4.1)

Where:

m and n, are the maximum and minimum lateral limits of the area (um), (m-n)/50
is the space between the last and first section and their correspondent lateral
limits (pm), j is the section number in the image]: 1,...,5, X, is the position of
the section measured in microns (um) respect to the right side of the picture, and
X. is the auxiliar variable to add the distance between each section in the current
area, i =0,...4. The section number to pick from the associated topography file

was determined by:

Xi

11.453

 

SL = (4.2)

where SL is the section number in the left-oriented topography reconstruction and
11.453 pm is the distance between each section in the SD topography software.
In the same fashion the front-oriented orthogonal sections positions respect to
the top edge of the image (Y1), as well as the front section number in the SD

reconstruction (Sp), were found with:

 

_ (p-q)
Yj —q+——56-[1+12Yi] (4.3)
s — Yj
F - 11.453 0.. (4'4)

57

The references in this method were taken respect to edges of the image to match
the way the LSM 310 software counts the sections in topography mode.
However, the position of these sections can be readily converted to the

references fixed in the edges of the tool (See 4.2.1).

Once the location of maximum depth was found in each method, the left view
and front view sections associated with this location were extracted out the z(x,y)
matrix. Then, the measure function of the software was used to obtain the value
of the maximum depth. Finally, an Excel data sheet was used to compare and
obtain the maximum depth and its location out the several possibilities provided
by the three methods for each machining time. From this point on, these
locations and their correspondent depth values were regarded as the maximum-

depth locations and maximum depth values.

4.2.3. 1 Crater wear time evolution

The maximum crater depth locations (MCDL) of the comers with machining time
of 300$, 480s and 720s (A-A, B-B, and C-C sections in figure 4.8) were chosen
as references locations for time evolution analysis. All the sections passing
through these three reference locations were obtained for all machine times.
Then, these sections were overlaid using Adobe Photoshop 7.0 to finally give the
crater evolution in time (Figure 4.9). Images in this thesis are gresented In

color.

58

 

 

 

300$

 

 

 

 

 

 

 

 

 

  

 

 

 

 

 

B C
Max. depth 4808 i Max. depth 720$ .EMaX-PGPth
location for | location for , :location for
3008 7208
A

 

 

 

3003 reference

 

 

 

 

 

 

 

 

 

  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  
 

using 300s reference

_ _ B-B sections
using 4803 reference

....... C-C sections
using 7208 reference

 

 

Figure 4.8 Reference locations for crater wear evolution

 

 

Overlay In the 480s reference location (B-B Sections)

 

------- “1:;

W 2
\ifixflifiv“. ‘ \

“E \s.

 

 

LEFT VIEW

\
|
|

I

 

 

 

 

Figure 4.9 Evolution of the crater obtained overlaying the B—B sections

59

4.2.4 Crater wear Phi-Z sectioning

As three of the 22 optical sections of the z-stack were highly saturated (*)’ a

validation of the values obtained with the 5X objective was needed. This was
done using the phi-z function and a 50X objective, which has better transversal
and depth resolution than the 5X objective. Using the phi-z function, right-view
profiles showing the crater wear evolution at the MCDL’s for 300$, 4803, and
7203 were obtained. Optimization of the microscope parameters was also
necessary resulting in the following settings: 50x objective, zoom screen of 20,
488 nm (Argon) laser line with 100% power, contrast: in the range of 53 to 75,
brightness ranging from 400 to 414, z : xy ratio of 300% (ratio between the height
and length of the display), 350 scan lines, and position: 50.

Measurements of maximum wear depth were carried out after the image
processing. Images were overlaid and merged to increase the FOV of the 50 X
objective and the relation between the pixel size and the distances was
determined. These measures were done using the 50X objective resolution, and
the pixel ratio changes when transferring the files from the LSM 210 computer to

the computer that contains the LSM 310 software.

4.2.5 Phi-Z sections for flank wear

Phi-z sections of the flank face for all machining times were obtained for each

comer. Again, the MDL’s for 300$, 4808, and 7203 (figure 4.9) were used as

 

( )A saturated image contains a great amount of saturated pixels .A pixel is saturated when its
grayscale value is 255..

60

references. These phi-z sections had a right-view orientation and were used to
show the flank-wear evolution in time. In this part, images were gathered with the
same parameters mentioned in 4.2.4,except for, this time the z : xy ratio was
100%.The slope of the land wear was measure after the imaging post-processing
for the different machining times. No 2D images or SD reconstructions were

acquired due to the limitations in the maximum displacement of the stage.

4.3 ELECTRON MICROSCOPY DATA ADQUISITION

Electron microscopy data acquisition was carried out in the premises of the
Center for Advanced Microscopy (CAM) at Michigan State University. The SEM
used was a JEOL JSM-6400 Scanning microscope (figure 4.9). The image
acquisition for the SEM pictures was achieved with the SIS 3.0 (Soft Imaging

System) software.

 

Figure 4.10 JSM-6400 Scanning Electron Microscope

61

4.3.1 Backscattered electrons (BSE) images

Crater wear

During the optimization of parameters for the data gathering in the confocal
microscope, confirmation of the shape for the crater was needed. In the first
stage of the optimization, confocal results showed that the crater had gone
through the three layers and reached the WC substrate. Using the JEOL JSM-
6400 Scanning microscope in backscattered electron (BSE) mode images of all
comers were obtained. Backscattered electrons can be easily related to the
Average atomic number of the material, and therefore used to build an “atomic
number” image. In these images, zones containing chemical species of high
atomic number will be seen brighter than those areas with chemical species of
low atomic number. BSE images showed that during the cutting experiments only
the first layer (T iN) had been worn out and that the AI203 layer was being
exposed (Appendix G). Then, parameters were reviewed and adjusted to obtain
the optimal settings for the confocal microscope data gathering. The acquisition

parameters for this part were set as follows:

Accelerating voltage 25 KV,

condenser lens 9 (coarse) and 0 (fine)
working distance 15 mm

magnification 43X

62

Flank wear

Flank wear images were taken in BSE mode due to the difficulties that arose in
the imaging with the LSM 210 (see 4.2.4). The information extracted out of these
images made possible to differentiate the limits between the first two layers, and
also helped to roughly interpret the phi-z profiles obtained with the CLSM

microscope (Appendix G). The SEM parameters for flank wear images were set

to:

Accelerating voltage 25 KV,

condenser lens 9 (coarse) and 90 (fine)
working distance 15 mm

magnification 40X and 250x

4.3.2 Energy Dispersive X-ray Spectroscopy and Dot maps

A spectral analysis of the chemical composition and distribution over the rake
face was run using a Noran x-ray detector unit and EDS software (Vantage
spectral 1.5.1). The specimen used for this purpose was the comer with the
machining time of 300 s and the results can be seen in Appendix B. In addition,
X-ray dot maps showing the presence of Ti, N, Al, O, and Fe in the tools were
acquired for all machining times. The sequence obtained was to keep track of the
growing crater area and the limits between the first and second layer. Also, line
scans perpendicular to the trailing edge and parallel to the scoring marks were
obtained while in the X-ray mode (Appendix D). The values for accelerating
voltage and working distance remained unchanged respect to the values used for

63

BSE images, but the magnification was changed to 38X in order to allow for the
EDS display to capture the area of interest. Also, the contrast and brightness had
to be adjusted for a good image. The condenser lens was adjusted to 11(coarse)
and 40 (fine) to give an appropriate dead time during x-ray data acquisition.
During the spectral analysis for the 3003 comer the dead time fluctuated between
20 and 30 %, whereas during the dot maps acquisition it ranged from 30 to 40 %.

The EDS time limit and dwell limit were set at 30 s and 25 ms respectively.

4.4 ATOMIC FORCE MICROSCOPY DATA ADOUISITION

The equipment used in this part of the research was the Nanoscope Ill Scanning
Probe Microscope manufactured by Digital Instruments Inc., located in the
Center for Advanced Microscopy at Michigan State University. The images were
processed using the Nanoscope Ill version 4.23 rev. 6 software provided with the
microscope (figure 4.11). The information obtained with this microscope
constitutes the main validation of the data obtained with the: Zeiss LSM 210
Confocal Microscope. This validation was suggested in reference [30].

Because of the displacement limitations of the stage to obtain one profile of the
insert, fourteen consecutive areas were scanned and their images merged using
Adobe photoshop 7.0. These scans were performed in the corner with 3003 of
machining time, following a direction parallel to the trailing edge and passing
through the maximum depth location. All the images were obtained using the J

scanner tube, the nanoprobe NP silicone nitride tip, and with the DVM values set

64

to 7.89 volts and 2.72 volts, for the upper and lower position of the switch

respectively. The acquisition parameters were set as follows:

Scan Controls

Scan size

X offset

Y offset

Scan angle

Scan rate

: 77.5 um
: 0.00 nm
: 0.00 nm
: 0.00 deg

: 4.07 HZ

Number of samples : 512

Slow scan axis

Z limit

Feedback controls
Integral gain
Proportional gain

Look ahead

Set point
Analog 1
Analog 2

: Enabled
: 440 V

: 3.00

: 3.00

: 0.00

: 0.00 V

: 0.00 mV
: 0.00 mV

65

Channel 1
Data type

Z range

Line directions

Scan Line

Real time Plane fit
Offline plane fit
High pass filter

Lowpass filter

Other controls
Units

Color table

Min. engage gain
2 modulation

Tip serial number

: Height

: 2.50 pm
: Trace

: Main
(Disabled)
: Line

: Full

: Off

: Off

: Metric

: 6.00

: Enable

3 (n/spec)

 

 

 

Figure 4.11 Nanoscope lll scanning probe microscope

66

Chapter 5 : RESULTS AND DISCUSSIONS

5.1 VALIDATION OF THE CRATER SHAPE

The images obtained with the Vynil Poxysiloxane replica and the SEM confirmed
that the crater wear shapes obtained with the LSM 210 software were showing
the real topography of the crater. Figures 5.1(a) and (b) show the 20 and SD
confocal views of a worn corner with a humped formation next to the trailing edge

and, also the crater starting to develop on the other side of the formation.

 

1954 iii“ X 293mm

(b) Topographical view of the Vynil poxysiloxane replica of a worn comer

Figure 5.1 (a), (b) Confocal views of the Vynil poxysiloxane replica

67

This validation weakened the idea about the difference in optical properties of the
coatings playing a role on distorting the actual surface geometry. Similar
information can be seen in appendix A the a comer machined for 300 seconds,

which was imaged using the SEM microscope in secondary electron mode

5.2 CRATER WEAR EVOLUTION AND MEASUREMENTS

5.2.1 TIME SERIES OF CONFOCAL IMAGES

The 20 and SD (topographical) confocal images exhibited particular features of
the surface morphology. First, an unexpected hump that started approximately at
190 pm from the major cutting edge for all machining times except for the 720
seconds comer, in which the hump started at about 300 microns from the edge.
Second, a thin depression preceding the hump of approximately 20 um width,
was observed at all machining times except for the 720 seconds corner. This was
observed to act as boundary for the crater zone (edge side limit, figures 5.2(a)
and (b)). Third, a crater zone that started at about 700 um and grew with
machining time towards the trailing edge was also found. Fourth, in the comer
with 7203 machining time a new humped island was observed next to the inland
limit of the crater. The ZD shape and dimensions of the crater were observed to
be approximately constant and delimited by the depression on the trailing edge

side and the inland limit of the crater (Figures. 5.2 (a) and (b)).

68

‘2.

20 VIEW . ' Inland side limit
'. ' of the crater

45":

A.

' ' n". . “\""'.‘Il.‘!

Edge side limit
of the crater ,3

Inland side

Edge side
limit of the
crater

Trailing edge

500 llmL

3D TOPOGRAPHICAL IMAGE 250 Ilm
(Left view orientation)

 

Figures 5.2 (a),(b) Features of the crater wear for the multi-layer coated insert

Figure 5.3 shows the 2D evolution of crater wear using a slice on the brightest
position and figure 5.4 renders the topographical (3D) evolution for all machining
times. Both image sequences were obtained with the Zeiss LSM 210 confocal

microscope.

69

 

the crater wear

ime of

Int

lOn

howing the evolut

images 3

3 ZD confocal

5

igure

F

70

500 pm

250 pm

500 ,rm 1

250 pm (d)

500 ("TI

250nm ‘ (h)

\i

..l

l\‘ ‘
I.

i

500 pm

250 llm

250 pm

500 ,um i

250 Ilm

500nm

" Ollm

 

Figure 5.4 Topographical views of the worn corners for all machining times

71

5.2. 1. 1 BSE images and x-ray spectroscopy analysis of crater wear

BSE images revealed several details about the chemical composition of the
different zones in the crater. For example, it was found that the crater zone,
limited by the inland side and edge side boundaries, was composed of two main
regions: a humped island made of TiN and a growing crater zone of A120). Also,
the thin depression observed in the topographical images turned out to include a
very narrow zone of Al203.Furhter, traces of steel were found attached to the TiN
coating specially in the limits of the crater zone (figure 5.5). In appendix B, the
spectral chemical analysis and the x-ray dot map for the comer with 3008
seconds machining time is shown. Appendix C shows the BSE images of the
comers for all cutting times. Another interesting finding in the x-ray analysis was
obtained with the linescan feature. The chemical analysis results showed that the
linescan parallel to the chip flow (scoring marks) exhibited the Ala 03 at the
beginning of the TiN hump, whereas in the linescan perpendicular to the trailing
edge Al203 was not detected. This trend was consistent throughout all the
machining times and confirmed with the confocal microscope. Appendix D
presents the linescans for a 3003 machining times in both directions.

In the absence of a reliable and automated method for determining the limits
between layers, the backscattered images were used to measure distances and

areas of interest in crater wear. BSE images were able to provide different

72

brightness intensities for the areas of steel (AAN"’=25.8), TiN (AAN=14.5) and

Al203 (AAN=10), thus, giving a means of differentiation between layers.

Steel attached
to the TIN
coating

 

Figure 5.5 BSE image of a worn comer with the chemical elements observed

Two important areas were measured for all machining times. A1 was measured
so that the darkest area (Al203) was enclosed and no TiN material included. A2
was defined as the crater area and its boundaries were delimited by the inland
side and edge side limits (Table 5.3). The length (L) and the width (W) of area A1
were regarded as relevant as these values could provide information of the crater
wear trend. A2 remained almost constant at around 84 000 um2 except for the
value at 7205 (75 000 um2 approximately). A1 exhibited a growing trend for all

machining times (figure 5.6), with its width (W) and length (L) values also

 

( ) AAN=Average Atomic Number

73

increasing. However, the rate of increase was less pronounced for W than for L
(figure 5.7), meaning that the crater in the Alumna zone (2nd layer) expands
faster in length than in width Three distances were also found to be of interest:
the distance between the trailing edge and the beginning of the Tin hump (W1),
the distance between the beginning of the hump and the inland side limit (W2),
and the distance between the trailing edge and the inland side limit (W1+W2).
The time-elapsed trends of W1, W2, and W3 (figure 5.8), suggested W1, W2,
and W1 +W2 remained constant at about 190, 500, and 700 pm respectively
between 60 and 4803. The comer with 720s machining time presented a
significant drop in W2 while increasing its W1 value. However, the value of

W1+W2 was increased respect to the values observed between 60 and 480 s.

74

Table 5-1 Crater areas measurements for all machining times

 

 

 

 

 

 

 

 

 

 

 

Machining L W W1 W2 A1 A2
Time (um) (um) (um) (llm) (umz) (umz)
($90)

60 371 17 174 498 6768 818048

120 844 74 188 472 40148 822385

180 1083 1 18 179 493 83760 831308

240 1 141 188 202 519 157583 830021

300 1 158 183 193 498 138980 845469

480 1858 306 179 516 439333 900182

720 1705 432.8 319 472 548853 749735

 

 

 

 

 

 

 

75

 

 

Crater areas as functions of time

.3;
:I
o-
a
g 0A1
g IA2
E
E
<

 

O

200 400 600 800
Machining time (sec)

 

 

 

Figure 5.6 Plot of the crater areas evolution in machining time

 

Length and width evolution in time of the
exposed alumina area

0 Length
I Width

(mic-rpm).
.. 9 6 e" E

 

O

200 400 600 800
Machining time (sec)

 

 

 

Figure 5.7 Plot of the length and width evolution for the exposed Alumina area

 

Variations of the crater limits 8 as a function of
time

0W1
IW2
3W3

 

0 200 400 600 800
Machining time (sec)

 

 

 

Figure 5.8 Variation of the width limits position of the crater in time

5.2. 1.2 Maxlmum crater depth measurement

Maximum crater depth is accepted to give a clear idea about crater wear extent
[3]; thus, any crater wear quantitative description should include it. The maximum
crater depths and its locations (figure 5.9) obtained are enlisted in Table 5-1. The
location of maximum crater depth was found to change with machining time. The
position respect to the major cutting edge (Y) showed a consistent value that
fluctuated between 500.1 and 683.4 microns, while the position with respect to
the minor cutting edge (X) exhibited a wider range of variation (836.0 to 1248
microns). This implies that the peak interface temperature, which occurs in the
vicinity of maximum crater depth [8], is changing its location as machining time

increases. Additionally, the X value showed non-stable behavior between 60s

77

and 1806, then an approximately constant value between 240 and 4805, and
finally a considerable rise at 720s (figure 5.10). These were interesting findings
considering that traditional methods for crater wear measurement do not allocate
for this type of behavior [6]. The maximum depth values evolved with a two-
stepped shape (figure 5.11). it seems that 180 s is a transition point for the
maximum depth value and that there is a constant behavior 0f the depth between
300 and 4805. In the latter, the closeness between the maximum depth value for
300 and 4805 (2.3 microns) and the thickness of the first layer (TiN, 2.5 microns)
could indicate the Alumina layer (second layer) was resisting the crater wear in
such a way that stopped the crater depth growth. It is speculated also that
because of this “barrier” effect, the crater wear is more evident in the TiN layer
(top layer) during this period of time. The TiN humped area was decreased as
the A1203 area (A1) expanded (figure 5.6). These findings seemed to be
supported by the facts that the Alumina (A1203) possesses higher hot hardness
and is also more chemical inert than TiN when machining medium-carbon steels
[8], which means that Al203 is more likely to resist abrasion wear as well as
diffusion and dissolution wear.

The validation of these depth values was done with a 50X objective for three
machining times (300s, 480s, and 7205) and the results can be seen in Appendix
E. A good agreement was found for the maximum depths corresponding to 3005
and 4808, considering the increase and resolution when changing from 5X to
50X objective. However, there was a considerable difference when comparing

the depth for the 720s machining time.

78

 

cm _. coaoom

comm owom. 0.8.2 83 .oom. 2.2.1.0 39:29.2.

 

 

 

 

 

$2 8.68 . .
.sm...> +.zo.2..2.....

«Ewa mag mom—w
2°.—£00.. 15mm Effigy

 

E

m
m
n
o

52. o n m m 5 26.58
Ill .52.; km...

. : cane

 

.. com

ocor

oomr

 

Figure 5.9 Orthogonal sections obtained at the maximum crater depth location

79

Table 5-2 Maximum crater depth location for all machining times

MAXIMUM DEPTH LOCATION
FOR CRATER WEAR

., a
I'.’

Time (sec) Depth, Zmax (um)

 

80

 

Maximum depth location as a function of
machining time

Posltlen(relspect t)o edges
oeeseééé

 

0 200 400 600 800
Machining time (sec)

 

 

 

Figure 5.10 Plot of the maximum crater depth location versus machining time

 

Maximum crater depth as a function of
machining time

 

E 2.5

2,. 2

file

°8 +DEP11-l
E'g 1

av

-E- 0.5

i o

0 200 400 600 800
Machlringtlnnhec)

 

 

 

Figure 5.11 Plot of the maximum crater depth versus machining time

5.2. 1.3 Time-evolution profiles for crater wear (Overlays)

The evolution in time using the 300$, 480s and 7208 references is rendered in
figures 5.12, 5.13, and 5.14. These overlaid profiles revealed an interesting
possibility in the time evolution of the crater. It was observed that the second
hump, which showed up at 7206 machining time, could be naturally included in
the crater evolution of the tools and not be considered as a random occurrence
(as it was first though). This particular finding can be observed at 600-800

microns from the trailing edge in three overlaid figures.

82

.23
c. obscene... 2a £85 25 c. momeE.

—

com

.000.

 

.0022

 

Figure 5.12 Time evolution of crater wear at the 300 5 reference (5X objective)

83

..o_oo
:. “22:30.... 0.5 235 25 c. none—E

a

com

.200.

.022.

 

Figure 5.13 Time evolution of crater wear at the 300 5 reference (5X objective)

84

6.00
E pounced... So 235 25 :. oomeE.

-

com

.0002

.0002

 

Figure 5.14 Time evolution of crater wear at the 720 3 reference (5X objective)

85

5.3 ATOMIC FORCE MICROSCOPE RESULTS

The data obtained with the AFM, which was done for the 3005 comer only,
showed a good correspondence with the maximum depth value obtained with the
50x objective (2.6 microns). This was inferred from the fact that all AFM depth
values observed where always within the 2 range of 2.5 um, with the exception of
the images gathered next to the inland side limit of the crater. In the latter, some
zones were considered out of the z-range by the Nanoscope ll software meaning
that in these particular areas the depth was bigger than 2.5 urn. The AFM SD
images showed the presence of two mountain-shape formations in both limits of
the crater zones. Also, the presence of the depression next to formation in the
edge side of crater zone was detected. Based on the x-ray analysis, the AFM
findings, and the position of these formations it is speculated that they are steel
particles attached to the TiN coating. Appendix F contains the more relevant

information regarding AFM data.

5.4 FLANK WEAR EVOLUTION AND MEASUREMENTS

The flank BSE images of the new comer and the comer with 4808 machining
time helped to define approximately some important reference points in the flank
(Appendix G). These BSE images showed that Al203 was already exposed on
the tip of the new insert. The Al203 distance, measure on the flank face with the
SIS 3.0 software, was 34 microns and was probably the result of the finishing
process (honing) for the insert edge. The Al203 flank distance increases to 36.53

microns at 4808 machining time and exhibits scoring marks as well as some steel

86

particles attached. The TiN flank layer in the 4805 corner appeared to be worn
slightly in a distance of 25.85 microns and also exhibited scoring marks plus steel
particles attached.

As mentioned in 4.2.4 ZD and 3D confocal images were not gathered and phi-z
sections (x-z) were obtained instead. In the aim of extracting a time evolution of
the flank wear the flank profiles were rendered in a time sequence (Figures 5.15
trough 5.17) and the slope values measured (Tables 5-3, 5—4, and 5-5). However,
it is suspected that the scoring marks, the presence of steel particles attached,
and the fact these measurements were done in different inserts an evolution
trend was not clearly detected. In other words, although the flank wear evolution
could be observed as machining time elapses, the slope measurements did not
show a behavior that could be clearly related to the wear mechanisms and the
coating wear-resistant properties. The slope values are plotted against machining

time from figure 5.18 to 5.23.

87

Images In this thesis are presented in color 0 20 40 60
0 IHIIHIIIHII.

20
40
60

80

100

 

Figure 5.15 Flank wear evolution at the 300 5 reference (50X objective )

Images In this thesis are presented In color

0
20
40
60

80

100

 

Figure 5.16 Flank wear evolution at the 4803 reference ( 50 X objective )

88

images in this thesis are presented In color

0

20

4O

60

80

100

 

Figure 5.17 Flank wear evolution at the 720 s reference ( 50X objective )

89

Table 5-3 Time evolution of slope values at the flank face for reference 3008

 

0 gr: 20 4O 60

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

0
Slope 1
20
Slope 2 f.-
40 "
Slope S -"
60 m
Slope 4
so "
Slope 5 Slope =mln
1 00
Machining
Time Slope 1 Slope 2 Slope 3 Slope 4 Slope 5
0 0.429 1.429 2.125 12.500 22.143
60 0.350 1 .273 3.069 9.800 7.750
120 0.280 1.273 5.933 15.500 22.143
180 0.388 1.077 2.225 9.800 10.333
300 0.368 1 .273 2.225 9.800 10.333
240 0.411 1.120 2.225 19.600 15.500
480 0.417 1.167 3.179 6.533 10.333
720 0.400 1 .129 3.56 9.800 6.200

 

 

 

 

 

 

90

 

Table 5-4 Time evolution of slope values at the flank face for reference 4808

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

O
Slope 1
20
Slope 2
4O
Slope S
60 Slope 4
80
Slope 5
1 00
Machining
Time Slope 1 Slope 2 Slope S Slope 4 Slope 5
0 0.389 1 .421 3.600 1 1 .333 19.000
60 0.412 1 .350 3.600 10.200 5.900
120 0.483 1.216 3.103 10.2 10.2
180 0.530 1 .227 2.250 14.571 31 .667
240 0.510 1 .286 1 .758 10.2 12.667
300 0.560 1 .174 3.103 12.750 7.917
480 0.483 1.174 3.913 8.5 38.000
720 0.448 1 .174 3.000 20.5 19.000

 

 

 

 

 

 

91

 

Table 5-5 Time evolution of slope values at the flank face for reference 720s

 

0 gr: 20 40 60

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

O
Slope 1

20

40 Slope 2

.. :23: ..

80 Slope 5 n

1 00 L Slope =mln
Machining
Time Slope 1 Slope 2 Slope 3 Slope 4 Slope 5

0 0.630 1 .564 6.364 14.75 24.429
60 0.485 1 .531 2.692 14.75 1 1 .4
120 0.427 1 .838 8.750 14.75 6.840
180 0.465 1.515 3.5 1 1.8 17.1
240 0.475 1 .47 5.000 14.75 10.688
300 0.518 1 .361 5.384 14.75 21 .375
480 0.435 1 .838 3.5 14.75 8.5
720 0.430 2.1 3.5 29.5 15.545

 

 

 

 

 

 

92

 

 

Slope variation in time at the tip of the tool for
the 300s reference

..a
O,

1.4

...a
-sio

 

oSiopel
IS|op92

 

 

.° .
a:

0.4

Slope (micron/micron)
O
m

9
lo

 

O

0 200 400 600 800
Machining time (sec)

 

 

 

Figure 5.18 Plot of slopes 1 and 2 versus machining time (300 s ref.)

 

Slope variation in time at the flank for the 300s

 

 

 

 

reference
25
’5‘
2 20
g 15 e Slope 3
o I Slope 4
E 10 A Slope 5
g 5
in
0
0 200 400 600 800
Machining time

 

 

 

Figure 5.19 Plot of slopes 3, 4, and 5 versus machining time (300 s ref.)

 

Slope variation in time at the tip of the tool for the
4803 reference

 

5‘
I:
E
E e Slope 1
:2 - Slope 2
a
2
en
0 200 400 600 800
Machining time (sec)

 

 

 

Figure 5.20 Plot of slopes 1 and 2 versus machining time (480 s ref.)

 

Slope variation in time at the tool flank for the
480s reference

 

 

 

40

€35

gao
§§ 25 eSlopeS
r7120 20 ISlope4
.215 .SlopeS

V10

5

0

 

200 400 600 800
Machining time (sec)

0

 

 

 

Figure 5.21 Plot of the slopes 3, 4, and 5 versus machining time (480 s ref.)

94

 

Slope variation in time at the tip of the tool for the
7205 reference

’8
2
2
E
E ' eSlope1
5’ ISlop92
é
a
2
in

 

0 200 400 600 800
Machining time (sec)

 

 

 

Figure 5.22 Plot of slopes 1 and 2 versus machining time (720 6 ref.)

 

Slope variation in time at the tool flank for the
720s reference

88

M
(It

 

e Slope 3
I Slope 4
e Slope 5

518

 

 

Slope (micron/micron)
8

0|

 

O

0

200 400 600 800
Machining time (sec)

 

 

 

Figure 5.23 Plot of slopes S, 4, and 5 versus machining time (720s ref.)

Chapter 6 : SUMMARY AND CONCLUSIONS

The present work studied the use of a Confocal Laser Scanning Microscope
(CLSM) to characterize the crater and flank wear in multi-layer coated carbide
tools. Crater wear was successfully characterized by its surface topography and
maximum crater depths values for all machining time. Whereas, flank wear was
partially characterized by means of time-elapsed flank profiles.

The major conclusions of this study can be divided into two categories: The
microscopy aspect and the tool wear aspect. However, in most of the
conclusions they are closely related. In the microscopy aspect the usefulness of
confocal microscopy to obtain reliable surface profiles and topography was
confirmed [29,30]. The need of validation methods [30] was also corroborated as
SEM and AFM microscopes were used to determine the layers’ limits and
validate the depth values. Also, the optical properties of the materials were found
to have an influence in the results of the topography rendering. This was
especially true for the particles of steel attached to the TIN layer, which seemed
to distort the topography surface wherever a considerable accumulation of steel
was found. Regarding the tool wear aspect, the particular behavior of the wear in
coated tools [33,34] was verify by the presence of a humped island of TIN and
growing crater of Al203 with a maximum depth location changing with machining
time. More representative crater wear profiles could be obtained if they are
obtained parallel to the chip flow direction instead of the direction perpendicular
to the trailing edge. The use of different comers to analyze the tool wear

evolution seems to had a bigger impact in flank wear than in crater wear, and this

96

was reflected in the difficulties to find a flank wear trend. The need for automated
methods to get quantitative information of the worn zones from the images
provided by the CLSM and SEM was also noted. This was especially evident

when trying to discriminate the limits between the first and second layers.

97

APPENDICES

98

APPENDIX A : SEM merged image of crater wear

 

 

Figure A.1 SEM merged images of crater wear for the comer with 3005
machining time

99

APPENDIX B: EDS spectral analysis and x-ray clot maps

  

Sample ID : M-BSEQOOs
Area ID : Crater
Label : Spectra Analysis
Datemme :2004105I14

Note :

Each area has its own spectral analysis Identified by
point 1, 2, 3, 4, and 5 In the graphs Counts versus
Energy

 

 

 

 

 

 

 

 

 

 

'60001 TI
5000_
4000.
3000_
2000’
1000, Ti
Fe
0 A l A Fe .
12 3 4 5 6 7 8 91511121314151617181920

POINT 1 ENERGY (keV)

I
5000‘ TI

I
4000'

I
3000‘

I
2000’

' V
1000‘ Al TI

1 Fe
0 2 _ IL J A Fe

1 2 3 4 5 6 7 s s 1'01112131415151718192'0

POINT 2 ENERGY (keV)

 

 

 

AI

1000.: TI Fe

 

 

 

1 TI Fe
0.4-«er~:-.A¢<A-1‘*--,A....-.-..,
12 3 4 5 6 7 8 91011121314151617181920
POINT 3 ENERGY (kBV)

 

 

 

TI

1000*: AI 11
F9
12345678910fi1213T4151617181920
POINT 4 _ ENERGY (keV)

 

 

 

 

 

 

TI

1000‘: A' TI Fe

TI Fe
02% . . - . . . . - . - . .
7 8 9 10 111213 1415 1617 1819 20

[POINT 5 ENERGY (keV)

 

 

 

 

 

Figure 8.1 EDS chemical spectral analysis for the corner with 3006
machining time

101

 

Sample ID :M-BSE-3005 ' ‘
Area lD :Crater

Label :Dot map
Date/Time : 2004/05/14

 

 

Figure 3.2 X-ray dot maps of elements found for the corner with machining
time of 300s

102

APPENDIX C : BSE images of crater wear

 

  

-2 ‘-

Figure C.2 BSE image of crater wear for 60 s machining time

103

1.]

 

Figure C.4 BSE image of crater wear for 180 s machining time

104

 

Figure C.6 BSE image of crater wear for 300 s machining time

105

 

Figure C.8 BSE image of crater wear for 720 s machining time

106

 

APPENDIX D : X-ray linescans of crater wear

Sample ID : M-BSE-SOOs
Area ID : Crater
Label : Linescan
Dateri'Ime : 2004/05/14

Each chemical element is identified with its
symbol in the graphs Counts versus
Distance (microns)

.2 600 um

 

 

 

 

 

 

 

 

400'

300

200

100.

0 n , . . . . . -
100 200 300 400 500 600 700 800 900 1000 1100

Ti Microns

120

80

6O

40

o ,r‘1 , FAIR-Iran, , WJ] Him
100 200 300 400 500 600 700 800 900 1000 1100

Fe Microns

 

107

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8
4
0" v v I v r fir I r
100 200 H500 600 700 800 900 1000 1100
N Microns
30
20
10 films
0 12111an mMnnnmfllblh.
100 400 700 1000 1100
O Microns
300.
200.
100-
0 IJL'lanrl—LJ-lnrm—IL- mlnmnfknn
100 200 300 400 500 600 700 800 90010001100
N Microns

 

 

Figure D.1 Linescan chemical analysis of crater wear parallel to the chip flow
(300s machining time)

108

Sample lD : M-BSE-3003

Area ID : Crater
Label : Linescan ll
Daterl'ime : 2004105114

Each chemical element is identified with its
symbol in the graphs Counts versus
Distance (microns)

 

C '5" ifrl" 54'
,fiQlum

 

 

 

100 200 300 400 500' 600 700 800 9001000

 

 

 

 

:' , , nflMfih

100 200 300 406 506 600 700 800 9001000
Fe Microns

 

 

 

 

 

109

 

 

 

H

100 200' 300 400' 500' 600 700 800 900‘ 1000
Microns

 

 

 

 

 

I Nahum WWMMFHM “Mimi:

100 200 300 400 500 700 1000
Mi6crons

 

 

 

 

   

 

0' WM

106 206

 

         

300 400 500 600

Microns

700 800 900 100

 

Figure 0.2 Linescan chemical analysis of crater wear perpendicular to the trailing
edge ( 300s machining time)

110

APPENDIX E : 5X and 50X objective data comparison

 

Comparison between maximum crater depth
values obtained with 5X and 50X objectives

0 5 x Objective ‘
- 50x Objective ‘

Maximum crater depth (microns)

 

o 200 400 600 800
Machining time(sec)

 

 

 

Figure E.1 Plot of the maximum crater wear depth comparison
between the 5X and 50X objectives

111

 

Figure E.2 Phi-z section of crater wear for 3003 machining time at the maximum
depth location

112

 

Figure E.3 Phi-z section of crater wear for 480 s machining time at the maximum
Depth location

113

 

Figure E.3 Phi-z section of crater wear for 7203 machining time at the maximum
depth location

114

APPENDIX F: Atomic Force Microscope Images

 

Figure F.1 AFM merged images in the maximum crater wear zone at 3003
machining time

115

NanoScope Contact RFH
Scan size

Setpoint

Scan rate

Number of samples

 

Figure F2 AFM 20 view of zone B for 300s machining time

116

NanoScope Contact nFH
Scan size ??.47 um
0

Setpoint U
Scan rate 4.069 H2
Number of samples 512

X 20.000 uM/diu
2 2.500 uM/diu

 

Figure F3 AFM 3D view of the zone B for 3003 machining time

117

NanoScope Contact RFN
Scan size 77.47 pm
Setpoint 0 U
Scan rate 4.069 H2
Number of samples 512

 

Figure F.4 AFM 2D view of the zone K for 300s machining time

118

NanoScope Contact AFN
Scan size 77.47 um
Setpoint 0 U
Scan rate 4.089 H2
Number of samples 512

X 20.000 um/diu
2 2.500 um/diu

 

Figure F.5 AFM 3D view of the zone K for 3005 machining time

119

NanoScope Contact RFN
Scan size 77.47 um
Setpoint 0 U
Scan rate 4.089 H2
Number of samples 512

 

Figure F.6 AFM 2D view of the zone M for 3003 machining time

120

NanoScope Contact RFH
Scan size 77.47 ”m
Setpoint 0 U
Scan rate 4.089 H2
Number of samples 512

X 20.000 um/div
2 2.500 um/div

 

Figure F7 AFM 30 view of the zone M for 3003 machining time

121

BSE images of the flank face

APPENDIX G

<-

L:

L.

.
e.

: ...4._

in}

4.,

54.,

5‘

6......

..

 

1

Figure 6.1 BSE image of the flank face for an unwom insert

122

r.’

--‘~-~.
"' 1......
‘4':
-;.

.v-q
'4

“\M
ru-
\

w u... '. W.
»., ..‘2, .

..._
N...
::n::_‘.’f"
we, ; v-
.... .

51" -:

 

Figure 6.1 BSE image of the flank face after 480s machining time

123

[1]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[10]

[11]

[12]

[13]

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