33 CHAPTER 2 LITERATURE SURVEY 2.1 INTRODUCTION The investigation on the machining characteristics such as cutting force, temperature generation, surface roughness, tool wear and surface integrity etc., during turning of nickel based super alloys was carried out by many researchers. The investigation on these machining characteristics are important as these nickel based super alloys are difficulty to machine material due to high shear strength, rapid work hardening rate during machining and low thermal conductivity etc., The machining of these materials are needed to achieve near-net shape. Many researchers also investigated the machinability of nickel based super alloys using different cutting tool inserts viz., residual stress, micro surface hardness, and surface roughness that are generated on the machined surface, while machining the nickel based super alloys. In order to predict the machining characteristics during machining, many researchers modelled the machining parameters using Response Surface Methodology (RSM) and Artificial Neutal Network (ANN) etc., A lot of research works in machining nickel based super alloys are also performed using Finite Element Method (FEA) based simulation using software packages in the recent years.
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CHAPTER 2
LITERATURE SURVEY
2.1 INTRODUCTION
The investigation on the machining characteristics such as cutting
force, temperature generation, surface roughness, tool wear and surface
integrity etc., during turning of nickel based super alloys was carried out by
many researchers. The investigation on these machining characteristics are
important as these nickel based super alloys are difficulty to machine material
due to high shear strength, rapid work hardening rate during machining and
low thermal conductivity etc., The machining of these materials are needed to
achieve near-net shape. Many researchers also investigated the machinability
of nickel based super alloys using different cutting tool inserts viz., residual
stress, micro surface hardness, and surface roughness that are generated on
the machined surface, while machining the nickel based super alloys.
In order to predict the machining characteristics during machining,
many researchers modelled the machining parameters using Response Surface
Methodology (RSM) and Artificial Neutal Network (ANN) etc., A lot of
research works in machining nickel based super alloys are also performed
using Finite Element Method (FEA) based simulation using software
packages in the recent years.
34
Of the nickel based super alloys, nimonic C-263 is currently being
applied in the combustion chamber of aircraft engine, due to its unique
resistance to thermal fatigue and creep characteristics. In order to understand
and access the current status of research in the turning of nimonic C-263
alloy, an extensive literature survey relevant to the present investigation is
given below:
2.2 MACHINING OF NICKEL-BASED SUPER ALLOYS
Many researchers carried out experimental investigation during
turning of nickel based super alloys like Inconel 718, Inconel 625, nimonic
75, hastelloy, nimonic C-263 etc., for their machining characteristics. These
materials nowadays used for aerspace applications due to their superior
mechanical properties that are maintained at elevated temperatures.
Choudhury and El-Baradie (1998) presented a general review for
nickel based super alloys on their machinability during turning using different
cutting tool materials. They stated that nickel based super alloys are hard to
machine, because of their rapid work hardening during machining, chip
segmentation resulting in severe tool wear, and their strong tendency to form
a built-up edge by welding to the tool material at high cutting temperatures.
They pointed out that, the notch wear is generated by the adhesion of the
work material to the tool in turning Inconel with ceramic inserts and the flank
wear of the whisker –reinforced alumina and sialon tools are considered as a
diffusion type wear. Fritz Klocke et al (2012) also stated that the nickel based
super alloys generate high cutting forces and temperatures during machining
due to their stability under high mechanical and thermal loads which
adversely affect tool life.
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Konig and Gerschwiler (1999) stated that nickel based alloys
frequently employed materials for components subjected to high dynamic
stresses at working temperatures of up to 1100°C. These materials are used to
make blades, disks and housing components for hot sections of gas turbines
and jet engines.
Ezugwu et al (2003) discussed about the machinability of aeroengine
alloys during turning operations. They stated that the machining of aero
engine alloys provide a serious challenge for cutting tool materials during
machining due to their unique properties such as high temperature strength,
hardness and chemical wear resistance. The poor thermal conductivity of
these alloys result in concentration of high temperatures at the tool-workpiece
interface. The cutting tool materials such as cemented carbides, ceramics and
cubic boron nitride (CBN) are the frequently used for machining aeroengine
alloys. Further, they reported that the machining of aeroengine alloys at high
speed conditions can be achieved by selecting appropriate tool material and
cooling technology like high pressure coolant, cryogenic cooling and MQL
systems.
Manonukul et al (2002) stated that aero-engine components
operating under in-service conditions are often subjected to a range of
complex cyclic mechanical and thermal loading, leading to combined creep
and cyclic plasticity. They developed physically-based constitute equations
for creep deformations of nickel based C-263 alloy which is a commercial
alloy used for stationary components in aero-engines such as combustion
chambers, casings, liners, exhaust ducting and bearing housings.
Ezugwu and Okeke (2002) investigated the behavior of coated
carbide tools in high speed machining of a nickel based nimonic C-263 super
36
alloy in terms of tool life, surface finish and component forces generated.
They identified that triple layer, TiN/TiCN/TiN, coated carbide inserts gave
longer tool life when machining at higher speed and depth of cut conditions,
whereas the single layer, TiAlN, coated inserts produced better results.
Ankamma et al (2011) described about the nimonic C-263 alloy
that the higher percentage of chromium and molybdenum strengthens the
grain boundaries with the formation of complex metallic carbides, such as
M6C and M23C6, and the high cobalt content (19-21%) strengthens the
material by solution hardenings, which impede the movement of dislocation,
thus inducing higher plastic deformation. Further, the nimonic C-263 alloy
contains a large volume of uniformly distributed ' (Ni3 (Al, Ti)) precipitates,
which causes the main strengthening phase in the solution treated condition of
the material.
Ezugwu (2005) presented an overview on the machining of
difficult-to-cut aerospace superalloys. He pointed out that, to resolve the
machining difficulty and to ensure the functional characteristics with desired
quality, suitable machining conditions and cutting tools are to be established.
2.2.1 Investigation on the machining characteristics in the machining
of Nickel based alloys
Ezugwu and okeke, (2000) found out that machining under lower
feed rate conditions reduces the tool wear rate due to a drop in the component
forces and a reduction in the chip-tool contact time, leading to a reduction in
the temperature and stresses acting on the tool. They have also investigated
the characteristic features of a Nickel based super alloy in the generation of
high component forces during machining. Further, they observed that the
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component forces are affected by machining parameters (Cutting speed
m/min, feed mm/rev, depth of cut mm), properties of the work material
(Hardness, stress, etc), tool geometry as well as lubrication properties and
their concentration.
Wang et al (2003) introduced a new approach for machining of
nickel based super alloy Inconel 718, in which they combined the traditional
turning with cryogenically enhanced machining and plasma enhanced
machining. Further, they reported that, by joining these two non-traditional
techniques, they found that the surface roughness was reduced by 250%; the
cutting force was decreased by 30-50%; and the tool life was extended up to
170% over conventional machining.
Thakur et al (2008) stated that the nickel based superalloy Inconel
718 has many applications in the engineering industries, due to it unique
proprties such as high oxidation resistance, corrosion resistance even at very
high temperatures. They carried out an experimental investigation in the
turning of Inconel 718 using tungsten carbide (K20) to study the
machinability of this alloy in terms of the cutting forces, cutting temperature
and tool wear. They reported that the machining parameters are to be selected
carefully to achieve lower cutting forces and cutting temperature due to the
typical machining characteristics of the Inconel 718. The cutting force was
observed to decrease with increasing cutting speed due to the high
temperatures generated at the cutting zone.
Fnides et al (2011) conducted an experimental study in hard turning
of AISI H11 hot work steel (50HRC) to determine the statistical models of
cutting forces using Response surface Methodology (RSM). They carried out
the experiments based on L27 orthogonal array. Further, they reported that the
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depth of cut was the dominant factor affecting cutting force components. The
feed rate influences tangential cutting force more than radial and axial forces.
The cutting speed affects radial force more than tangential and axial forces.
Thakur et al (2009 A) investigated the machinability of super alloy,
Inconel 718 during high speed turning using tungsten carbide insert (K20)
tool. They studied the effect of machining parameters on the responses such
as the cutting force, specific cutting pressure, cutting temperature, tool wear
and surface finish. They identified that, the cutting force magnitude is found
to be higher than the feed force, change in the specific cutting pressure is
attributed to the loss of form stability of the cutting edge. The optimum
surface finish was found in the cutting range of 45-55m/min cutting speed,
0.08mm/rev feed rate and 0.50mm depth of cut and also they observed that
the main type of wear is abrasion, microchipping and plastic deformation.
Ezugwu and okeke (2000) investigated the performance of PVD
coated carbide inserts during machining of nimonic C-263 alloy at high speed
conditions in terms of cutting force, tool wear, surface finish.They reported
that, the TiN/TiCN/TiN coated carbide inserts with positive, honed and
chamfered edge was found to be suitable for machining nimonic C-263 alloy
and also they identified the failure modes in machining nimonic C-263 alloy
with the coated carbide inserts include flank wear, notching, burr formation,
excessive chipping and catastrophic failure and also they reported that the
feed rate was identified as significant factor in affecting the surface finish,
tool wear and the generation of cutting force.
Pawade et al (2007) presented an experimental investigation into
the effect of various process and tool-dependent parameters on cutting force,
39
an indirect measure of machined surface integrity besides a microstructural
analysis of the machined surface damage, in high speed machining of super
alloy Inconel 718 using PCBN inserts. They reported that, the magnitude of
cutting force was two to three times higher than that of other force
components. The generation of larger cutting forces produce poor surface
finish as well as extensive surface damage.
Arunachalam et al (2004 B) stated that the considerable attention
has been given to use of ceramic cutting tools for improving productivity in
the machining of heat resistant super alloys (HRSA). However, because of
their negative influence on the surface integrity, ceramic tools are generally
avoided particularly for finishing applications. They dealt with the residual
stresses and surface finish components of surface integrity when machining
(facing) age hardened Inconel 718 using two grades of coated carbide cutting
tools specifically developed for machining HRSAs. Finally, they suggested
that coated carbide cutting tool inserts of round shape, chamfered cutting edge
preparation, negative type and small nose radius (0.8 mm) and coolant will
generate primarily compressive residual stresses.
The effects the effects of cutting tool coating material and cutting
speed on cutting forces and surface roughness were investigated by Muammer
Nalbant (2007) on machining nickel based super alloy Inconel 718 in dry
environments. They reported that there was an increment-decrement
relationship between cutting speed and cutting force. The minimum cutting
force was obtained with SCMT 120412 type multicoated Al2O3 carbide tools
while maximum cutting force with RCMT 120400 type single coated TiN
carbide tools. Also, they observed that an increasing relation between cutting
speed and arithmetic average surface roughness as well as between coating
number and average surface roughness. Minimum average surface roughness
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was determined with single layer (TiN) coated cemented carbide tools while
maximum average surface roughness was observed with multicoated
Al2O3tools.
Du Jin Zhanquiang Liu (2012) Investigated the surface integrity of
nickel based super alloy FGH95 in terms of surface roughness, microhardness
and white layer during milling operations. The influence of the cutting speed
on chip morphology was also investigated. He reported that the surface
integrity and chip morphology are very sensitive to the cutting speed. The
surface roughness has very little variations at below 2,400 m/min and the
value of surface roughness is high for the range of 2,800-3,600 m/min cutting
speed. The degree of chip segmentation increases with the increases of cutting
speed.
Bin Zou et al (2011) used Al2O3/TiN-coated tungsten carbide tools
for finish turning of NiCr20TiAl nickel-based alloy under various cutting
conditions. They investigated the cutting forces, Surface integrity, tool wear
and inter-diffusing, transferring of elements between Al2O3/TiN-coated
tungsten carbide tool and NiCr20TiAl nickel-based alloy during machining.
They reported that the flaking of coating matrix of tools and the heavier
plucking, cavities of the machined surface were induced by the higher cutting
forces at higher cutting parameters. The recommended the cutting speed of 60
m/min, feed rate of 0.15 mm/rev and 0.40 mm depth of cut in view of surface
quality and tool wear.
Altin et al (2007) investigated the influence of the cutting speed on
tool wear and tool life in turning Inconel 718 nickel based super alloy using
silicon nitride based and whisker reinforced ceramic tools.They stated that the
crater and flank wears are usually dominant wear types in ceramic square type
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(SNGN) inserts while flank and notch wear are dominant in round type
(RNGN) inserts. Further, they reported that square type inserts showed good
performance compared to round type inserts at low cutting speed and they
recommended the tool inserts for the machining of Inconel 718 are square
type KYON 4300 insert at low cutting speeds whilst round type KYON 4300
at high cutting speeds.
Ezugwu et al (2002) analyzed the effect of machining parameters
on flank wear during turning of nimonic C-263 alloy and they have reported
that increasing the cutting speed and depth of cut results in accelerated flank
wear.
Li et al (2002) studied the influence of the machining parameters
on tool wear and tool life during turning of Inconel using coated carbide and
ceramic inserts. They reported that at lower speed (120m/min), the inserts are
prone to depth-of-cut notching, and a transition was observed at about 240
m/min. At increasing the speed to 300 m/min leads to a reduction in depth-of-
cut notching and an increase in nose and flank wear. Further, they reported
that PVD coated carbides KC7310 are more suitable for cutting Inconel 718
than CVD coated carbides and ceramic inserts of KY2000.
Ezugwu Okeke (2002) investigated the behavior of coated carbide
tools in high speed machining of a nickel based super alloy C-263. They
reported that the machining of C-263 alloy with PVD coated carbide offers
greater advantage due to its higher resistance to characteristic wear
mechanisms encountered.
Abhay Bhatt et (2010) experimentally investigated the wear
mechanisms of uncoated and coated carbide tools in turning the nickel based
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super alloy Inconel 718, in which they have reported that abrasive and
adhesive wear were the most influenced wear mechanisms. The triple layer
CVD coated tools exhibited the highest wear resistance at high cutting speeds
and low feed rates and the uncoated tools outperformed the single and multi
layer coated tools in the low range of cutting speeds and intermediated feed
rates.
Devillez et (2007) investigated the influence of different coated
tools and cutting conditions on the machinability of Inconel 718 during
turning, in which they observed that the cutting force magnitude is higher at
low cutting speed and high feed rate. They have also observed the dominant
wear modes such as welding and adhesion of workpiece material onto the
cutting tool faces. The work material adheres to the cutting edge to form a
built-up-edge (BUE), and a built-up-layer (BUL) on tool faces. They have
reported finally that the AlTiN seems to be best coatings.
Gatto and Iuliano (1994) performed high speed turning on a heat
resistant alloy Inconel 718, using SiC (20%) whiskers reinforced ceramic
tools. They analyzed and modelled analytically the tool wear mechanisms,
chip formation process. Further, they observed that the variable wear
mechanisms along the tool-chip contact length that were attributed to
variations in plastic deformation energy.
Ezugwu and Tang (1995) carried out experimental investigation on
G-17 cast iron and a nickel base Inconel 718 alloy during turning operations
using round and rhomboid-shaped pure oxide (Al2O3 + ZrO2) and mixed oxide
Al2O3+ TiC) ceramic tools. They reported that the shape and geometry of
cutting tools play an important role in determining the nature of machined
surfaces. The round inserts produced a better surface finish than rhomboid
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inserts. Prolonged machining with these two ceramic inserts resulted in an
increase in the hardness values of the work materials. This increase was more
pronounced with Inconel 718 due to its high rate of work hardening, increased
compressive stresses and plastic deformation.
Kadirgama et al (2011) described the wear mechanism and tool life
when machining nickel based superalloy Hastelloy C-22HS with coated
carbide. They conducted experiment using four different cutting tool materials
under wet condition – namely, Physical Vapor Deposition (PVD) coated with
TiAlN; TiN/TiCN/TiN; Chemical Vapor Deposition (CVD) coated with
TiN/TiCN/Al2O3; and TiN/TiCN/TiN – to study the tool behavior, in terms of
wear and tool life. They observed tool failure modes and wear mechanism
like Flank wear, chipping, notching, plastic lowering at cutting edge,
catastrophic and wear at nose to be the predominant tool failure for the four
types of cutting tools, especially with CVD tools. Attrition/adhesion,
oxidation and built-up edge (BUE) were the wear mechanisms observed in all
cutting tools. Finally, they suggested that the PVD cutting tools performed
better than CVD cutting tools, in terms of tool life.
Senthilkumar et al (2006) conducted machining studies on
hardened martensitic steel (HRC 60) to analyse the effect of tool wear on tool
life of alumina ceramic cutting tools. The tool wear such as flank wear, crater
wear and notch wear were noted under different cutting conditions.They
developed wear model for the prediction of flank wear, crater wear and notch
wear using multi regression analysis and the tool life of the alumina-based
ceramic cutting tools were evaluated from these tool wear models. Furthe they
stated that, the tool wear affects dimensions and surface quality of the
workpiece and is one of the important criteria in determining the tool life.
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Vigneau and Boulanger (1982) stated that the machining of nickel
base alloys can be made by ceramic tools with metal removal rate four times
greater than carbide tools. However, among twenty ceramic grades tested,
only two have a sufficient strength to be used in industrial conditions, the first
is alumina base containing 30 % titanium carbide, the second is a sialon
material. Further they stated that the tool life increased four times with a
special edge preparation depending on the wear mechanism. The machining
of the nickel base alloy with ceramic has not any effect on the fatigue strength
of the parts.
Bushlys et al (2012) stated that the nickel based super alloy Inconel
718, is currently machined with cemented carbide tools at low speed (60
m/min) due to its unfavourable mechanical and thermal properties. They
attempted to study the machinability of Inconel 718 in terms of tool life, tool
wear and surface integrity using uncoated and coated PCBN tools aiming on
increased speed and efficiency. They found out that the protective function of
coating, increasing tool life up to 20 %, is limited to low cutting speed and the
EDX and AFM analyses suggested dominance of chemical and abrasive wear
mechanisms. The residual stress analysis shown advantageous compressive
surface stresses.
Costes et (2007) stated that the demand for increasing productivity
when machining heat resistant alloys has resulted in the use of new tool
materials such as cubic boron nitride (CBN) or ceramics. The grade of these
tools was not optimized for superalloys. They made investigation to show
which grade is optimal and what the wear mechanisms are during finishing
operations of Inconel 718. The result shown that a low CBN content with a
ceramic binder and small grains gives the best results. The dominant wear
45
mechanisms such as adhesion and diffusion due to chemical affinity between
elements from workpiece and insert were observed.
Thakur et al (2012) studied the relationship of degree of work
hardening and tool life as a function of cutting parameters like cutting speed,
feed rate, depth of cut, untreared tungsten carbide and postcryogenic-treared
tool. They reported that a significant performance in tool life was observed
due to cryogenic treatment given to tungsten carbide tool and also they said
that the optimized machining parameters minimize work hardening
characteristics and improve the tool life in high-speed machining of Inconel
718.
Field et al (1989) stated that the characteristics of machined surface
such as surface roughness and surface damage have significant influence on
fatigue life, creep, corrosion, and dimensional accuracy of a machined
component.
Outeiro et al (2008) investigated the generation of the residual
stresses during turning of Inconel 718 and AISI 316L using coated and
uncoated cemented carbide tools. They reported that higher residual stresses
are generated when machining with the uncoated tool than the coated tool.
Also, higher residual stress values were observed on the transient surface than
on the machined surface.
Guo et al (2009) reviewed the surface integrity characterization,
especially the characteristics of residual stresses produced in machining of
hardened steels, titanium and nickel based superalloys. They also discussed
the interrelationship among residual stresses, microstructures and tool-wear.
They stated that the residual stresses are classified into two kinds: they are
46
termed as macro residual stress (which existed in the order of hundred
microns in the subsurface) and micro residual stress (which formed at a
distance of few grains) and the residual stress is identified as the main factor
among the surface integrity parameters which influences the product
performance such as fatigue life, creep, corrosion, and dimensional accuracy
of a machined component.
Kitagawa et al (1997) investigated the performance of ceramic
tools in high speed machining of super alloy Inconel 718. The study indicated
that the tool wear developed more due to abrasive process than to a thermally
activated mechanism.
Chakraborty et al (2000) used commercially available tungsten
carbide (WC)-based tools and oxide-based ceramic cutting tools such as
alumina (A12O3) and zirconia toughened alumina (ZTA) during machining
hardened steel. They reported that the ceramic tools exhibited superior
performance as compared to the WC tools, especially at higher machining
speeds, both in terms of tool life and surface finish of the work-piece. They
observed severe crater wear in the WC tools, whereas, only a small amount of
edge chipping and nose wear occurred in the ceramic tools during high speed
machining.
Li (2009) investigated the residual stress distributions introduced in
a new generation nickel-based super alloy RR1000 by surface finish turning
using round and rhombic, coated and uncoated inserts, new and worn tools
and chipped tool. The concluded that compared with the rhombic insert, the
round insert generated a slightly higher tensile stress up to 1500 MPa and
turning of this alloy using chipped tool introduced a large compressive radial
47
stress field with the maximum value reaching -1000 MPa and the penetration
depth 400µm.
Aucote (1986) used range of sialon compositions to machine the
nickel-based alloy incoloy 901 to observe the flank wear and tool life. They
reported that the tool life and flank wear resistance increase with -sialon than
-sialon. Also, they stated that at high cutting speed one of the tool wear was
rake face flaking and the resistance to this mechanism was found to increase
with tool material grain size and at lower cutting speeds depth-of-cut notch
wear was of major importance and resistance to this wear was found to
decrease with increasing grain size.
Arunachalam et al (2004 A) investigated the residual stresses in the
machining of age-hardened Inconel 718 material using cubic boron nitride
(CBN) and ceramic cutting tools. The results showed that mixed ceramic
cutting tools induce residual tensile stresses of a much higher magnitude than
CBN cutting tools. The residual stresses and surface roughness generated by
the CBN cutting tools are more sensitive to cutting speeds than the depth of
cut.
Berruti et al (2009) investigated the residual stresses generated into
longitudinal and tangential directions during turning of the nickel based
superalloy Inconel 718 using carbide inserts. They observed that the residual
stresses are tensile on the surface and compressive below the surface. Further,
they stated that at higher cutting speed and feed rates produce higher tensile
stresses and the surface stresses in longitudinal direction are more sensitive to
the variation of the machining parameters than the stresses in the tangential
direction.
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Durul Ulutan and Tugrul Ozel (2011) reviewed the machining
induced surface integrity in Titanium and Nickel based superalloys. The
review identified that the residual stresses, white layer and work hardening
layers, as well as microstructural alterations, as being important surface
integrity problems, to improve the surface qualities of the end products. They
reported that the main surface defects during machining of nickel based
superalloys are surface drag, material pull-out/cracking,feed marks, adhered
material particles, tearing surface,chip layer formation, debris of microchips,
wear, and properties of work material are among the most important ones that
are worth investigating.
Therefore this work aims on the following:
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To design a predictive model for cutting force components,
surface roughness, flank wear and the generation of
temperature at the tool tip in machining this alloy using
different cutting tool materials under different levels of
machining parameters.
To perform a detailed investigations on the surface integrity of
the nimonic 263 alloy for evaluating the effect of the cutting
parameters on the surface integrity during turning, using PVD
coated carbide insert and whisker reinforced ceramic cutting
tool inserts, in terms of the formation of the surface and
subsurface residual stresses, micro hardness variation at
different depths beneath the machined surface, and the surface
finish generated.
To perform online tool wear monitoring using Acoustic
emission technique.
To model 3D finite element modelling in machining nimonic
C-263 alloy using DEFORM 3D software.
2.10 NEED FOR THE PRESENT STUDY
The nickel based super alloy of nimonic C-263 used in aerospace
components continually suffer from extremes of temperature, pressure and
velocity, and are in service for many decades now. It is also critical that the
most stringent quality controls are need, when the parts are machined.
Reliability is an important criterion in the manufacture of aerospace
components, and therefore, these component manufacturers need to maintain
high-quality on a consistent basis. The exacting standards of aerospace
73
machining make it mandatory that each part be machined with absoluteprecision, no matter how challenging the task is.
However, the machining of nimonic C-263 alloy is difficult due to
poor thermal conductivity, high work hardening rate, high shear strength, high
temperature oxidation at elevated temperatures environment, resistance to tool
penetration during machining. Since this alloy possesses high temperature
characteristics, and it places the cutting tools under tremendous heat, pressure
and abrasion etc during turning. It creates rapid flank wear, crater wear and
tool notching at the tool nose etc. Furtheer, it causes highly difficult to
machine the alloy, which in turn affects the dimensional accuracy and surface
integrity during machining. It is also important to know the mechanical and
thermal load acting on the cutting insert while changing the cutting
parameters during the machining of this alloy.
This research work focuses on modelling the machining parameters
using Response Surface Methodology, Artificial Neural Network (ANN) and
Finite Element Method (FEM). The optimization of machining parameters on
turning nimonic C-263 alloy using Response Surface Methodology (RSM)
based desirability approach was also carried out. Apart from modelling and
optimization of machining parameters, the investigation on the surface integrity
and on line tool wear monitoring using acoustic emission technique in machining
nimonic C-263 under different cutting tool inserts were also done.
The effects of machining parameters (cutting speed, feed rate and
depth of cut) on different responses such as cutting force components, surface
roughness, temperature at the tool end and tool wear (flank wear) were
studied. The modelling of machining parameters is carried out using response
surface methodology. The effectiveness of the response surface model was
evaluated with design of experiments. The optimizations of machining
74
parameters with respect to the responses were carried out using response
surface methodology based desirability approach. The machined surface and
worn out inserts were assessed by using scanning electron microscopy (SEM)
analysis and micro structural analysis.
2.11 SCOPE OF THE PRESENT STUDY
Great advances are taking place in the development and application
of newer materials, more specifically in aero engines, to enhance the thrust-
to-weight ratio and to meet the requirement of sustaining the corresponding
increase in temperature in the combustion area. To meet this demand, the
nimonic C-263 super alloy is currently being applied in the combustion area
of gas turbines, due to its unique resistance to thermal fatigue and creep
characteristics, by the presence of higher cobalt content. From the available
literature, the systematic and comprehensive analysis has not been carried out
in the turning of nickel based Nimonic C-263 alloy and hence, there is a need
for carrying out systematic turning studies on nimonic C-263 alloy with
different cutting tools and machining parameters.
Turning experiments were carried out on nimonic C-263 alloy to
investigate the interaction effect of machining parameters (cutting speed, feed
rate, and depth of cut) on the responses like cutting force components, surface
roughness, cutting temperature, tool wear and surface integrity. It is necessary
to model and optimize the machining parameters in order to improve the
surface quality, reduce cutting force components, reduce tool wear and cutting
temperature in turning nimonic C-263 alloy. The literature available in
modelling and optimization of machining parameters in turning nimonic C-
263 alloy is limited. For modelling the machining parameters, the response
surface methodology (RSM) is used.
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The multi performance optimizations are carried out using response
surface method based desirability approach. In order to understand the turning
process in turning of nimonic C-263 alloy, analysis of process parameters is
carried out using Analysis of variance (ANOVA).
2.12 OBJECTIVES OF THE STUDY
The important objectives of this research work are listed below:
To machine the nimonic C-263 alloy under different levels ofmachining parameters on turning operation and evaluate themachining attributes such as cutting force, temperature at tooltip, surface roughness and flank wear using three differentinserts such as PVD coated carbide , whisker reinforcedceramic and cubic boron nitride inserts.
To develop an empirical relation for the prediction of cuttingforce, temperature at tool tip, surface roughness and flankwear in turning nimonic C-263 alloy using Response SurfaceMethodology (RSM) with the three different inserts.
To develop an Artificial Neural Network (ANN) model for theprediction of cutting force, temperature at tool tip, surfaceroughness and flank wear in turning nimonic C-263 alloy withthe three inserts.
To compare the effectiveness of Response Surface Model(RSM) and Artificial Neural Network (ANN) model with theexperimental results of responses such as cutting force,temperature at tool tip, surface roughness and flank wear inturning nimonic C-263 alloy using three different inserts.
To optimise the multi responses such as cutting force,temperature at tool tip, surface roughness and flank wear
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using response surface method based on desirability approachin machining nimonic C-263 alloy using the three inserts.
To evaluate on-line tool wear monitoring using AcousticEmission (AE) technique during the turning of nimonic C-263alloy using PVD coated carbide and whisker reinforcedceramic inserts.
To develop Finite Element Model for the prediction of cuttingforce, temperature at tool tip, effective stress and effectivestrain using PVD coated carbide insert and to validate theexperimental results of cutting force, and temperature at tooltip with predicted values of Finite Element Analysis.
To investigate experimentally the influence of machiningparameters on the surface integrity in terms of microhardness,residual stresses in machining nimonic C-263 alloy usingPVD coated carbide and whisker reinforced ceramic inserts.
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2.13 METHODOLOGY
The methodology used in this research work is shown in the Figure 2.1.
Experimental Investigation on thefollowing machining attributes
with different tool inserts
1. Cutting force2. Temperature at tool tip3. Effective Stress and Strain