Journal of Cleaner Production 80 (2014) 271e281
Contents lists available at ScienceDirect
Journal of Cleaner Production
journal homepage: www.elsevier.com/locate/jclepro
Experimental investigation on removing cutting fluid from turning of
Inconel 725 with coated carbide tools
Ahmadreza Hosseini Tazehkandi*, Farid Pilehvarian, Behnam Davoodi
Department of Manufacturing Engineering, Faculty of Mechanical Engineering, University of Tabriz, Tabriz, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 November 2013
Received in revised form
12 May 2014
Accepted 31 May 2014
Available online 11 June 2014
The aim of this study is to investigate the feasibility of removing cutting fluids from turning process of
Inconel 725. For this purpose, the effects of machining parameters such as cutting speed, feed rate and
depth of cut on machining forces were investigated. These forces include feed force, thrust force and
cutting force. In addition, surface roughness was examined in both conditions of dry machining with
coated tool and wet machining with uncoated tool. Results showed that in contrast with conventional
machining processes, cutting speed and coating of tool are the most important parameters in removing
cutting fluids. The data obtained from the tests indicated that in machining with coated tool with special
ranges of parameters, cutting fluid could be completely removed from machining process. Furthermore,
for both of dry and wet machining, the optimum ranges of parameters were presented in order to reach a
green manufacturing process.
© 2014 Elsevier Ltd. All rights reserved.
Keywords:
Dry machining
Biodegradable vegetable oil
Coated and uncoated tool
Cutting forces
Surface roughness
Response surface methodology
1. Introduction
The main aim of all machining operations is to reach to lower
machining costs as well as improved quality and productivity. This
can be achieved by machining at the highest cutting speed without
affecting tool life, reducing the scrap parts and minimize downtime. During machining process, lots of parameters could affect the
cutting condition. Although machining operations can be carried
out “dry”, cutting fluids have been used extensively and play a
significant role in machining areas. Cutting fluids affect the productivity of machining operations, tool life and quality of workpiece. Also, they prevent the cutting tool and machine from
overheating. The proper application of cutting fluids provides
higher cutting speeds and higher feed rates. In general, a successful
cutting fluid must not only improve the machining process performance, but also fulfill a number of requirements which are nontoxic, non-harmful to health of operators, not a fire hazard, not
smoke or fog in use and costless. One of the drawbacks of using
cutting fluids is the waste disposal after being used (Kuram et al.,
2013).
* Corresponding author. Tel.: þ98 914 391 19 31; fax: þ98 914 148 72 63.
E-mail
addresses:
[email protected],
ahmadreza_
[email protected] (A. Hosseini Tazehkandi),
[email protected].
ac.ir (F. Pilehvarian),
[email protected] (B. Davoodi).
http://dx.doi.org/10.1016/j.jclepro.2014.05.098
0959-6526/© 2014 Elsevier Ltd. All rights reserved.
The use of cutting fluids repeatedly over time induces their
chemical changes. These changes are due to environmental effects,
contamination from metal chips and tramp oil. The growth of
bacteria and yeast becomes environmental hazard and also
adversely affects the cutting fluids. Cutting fluids gradually degrade
in quality and as they lose their quality the disposal of them is
mandatory. Waste disposal of cutting fluids is expensive and has
negative effects on the environment. The focus on lubricants has
shifted from biodegradability to renewability over the years as a
result of the changes in human beings' environmental thinking
(Davim, 2013). Biodegradability is the most important aspect with
regard to the environment and human health. Considering biodegradability, esters and vegetable oils are more appropriate to
formulate cutting fluids, because they are readily biodegradable in
contrast to the mineral, synthetic and semi-synthetic cutting fluids
(Lawal et al., 2013).
Nickel based superalloys such as Inconel 725 are widely
employed in the aerospace industry, in particular in the hot sections of gas turbine engines; this is due to their high temperature
strength and high corrosion resistance. They are known as one of
the most difficult-to-cut materials. In machining difficult-to-cut
materials, the coolant acquisition, use, disposal and the cleaning
of the machined components lead to significant costs, four times as
many as cutting operations of other materials. The machining
manufacturers aim is to take the advantages of dry cutting by
eliminating or minimizing the amount of cutting fluids and to
272
A. Hosseini Tazehkandi et al. / Journal of Cleaner Production 80 (2014) 271e281
improve material removal rate with high speed machining
(Devillez et al., 2011). Furthermore, costs relating to using cutting
fluids through machining of nickel based superalloys are 7e17
percent of total machining cost (Weinert et al., 2004). So, it clearly
reveals how dry machining can reduce the costs and increase the
productivity.
The costs associated with the use of cutting fluids is estimated
to be several billion dollar per a year. Consequently, elimination
on the use of cutting fluids, if possible, can be a significant
economic incentive. Considering the high cost associated with
the use of cutting fluids and projected escalating costs when the
stricter environmental laws are enforced, the choice seems
obvious. A moratorium on the use of cutting fluids and chemicals
harmful to the personnel and costly to remediate and by practicing dry machining. This would prepare industry for
manufacturing in the year 2000 and beyond, namely, green
manufacturing or environmentally friendly manufacturing
(Davim, 2013).
Dry machining means that no cutting fluid is used during process. For economic and environmental reasons machining process
is carried out without any cutting fluid but dry machining has some
disadvantages. Certain grades of carbides and coated carbide cutting tools are developed for the use in dry machining (Groover,
2007). Dry machining is preferable to operate at lower cutting
speeds and produce a low production rate in order to prolong tool
life. During dry machining process, temperature of the cutting tool
is very high and this induces excessive tool wear, thus decreasing
tool life. Also, the chips generated at machining cannot be washed
away and these chips cause deterioration on the machined surface.
The problems of cutting fluid contamination and disposal are not
seen in dry machining. Dry machining does not lead to the pollution of atmosphere or water resources. Contrary to dry machining,
in wet machining (machining with cutting fluids by any means
flooding and Minimum Quantity of Lubrication) environment,
water source and soil become polluted during disposal of the cutting fluid (Kuram et al., 2013).
Turning processes comprise a very big portion of metal cutting
process in industry (Nalbant et al., 2007). For successful implementation of turning, selection of workpiece material, machine tool
and suitable cutting parameters are necessary factors. Study of
cutting forces is critically important in turning operations because
cutting forces strongly correlate with cutting performance such as
surface roughness, cutting temperature, tool wear, tool breakage
and forced vibration. Therefore, choosing appropriate range of
cutting speed, feed rate and depth of cut which it is not required to
use cutting fluid plays an important role in the machining process
of the nickel base alloys, such as Inconel 725 (Lalwani et al., 2008).
Davoodi and Hosseini Tazehkandi investigated the feasibility of
removing cutting fluids in turning of Al5083 in order to lower the
production costs and reduce environmental impacts. They found
that when machining process carried out with higher cutting
speeds and lower values of undeformed chip thickness; cutting
forces and cutting tool temperature in dry machining are lower
than those in wet machining, so cutting fluids can be omitted from
machining process (Davoodi and Tazehkandi, 2014).
Sarikaya and Gullu focused on Taguchi method, response surface
methodology and desirability function in order to investigate influences of the cutting parameters and cooling conditions on the
surface roughness in turning of AISI1050 steel. In their study
machining parameters were cutting speed, feed rate and depth of
cut and investigated cooling conditions were dry cutting, conventional wet cooling and MQL. They concluded that feed rate and
cooling condition are the most effective parameters on surface
finish (Sarıkaya and Güllü, 2014).
Kuram et al. used design of experiment method to study optimization of parameters of AISI304 machining with various cutting
fluids. They drew a conclusion that utilizing vegetable-based fluids
can lower machining costs, improve machining performance, increase tool life, reduce surface roughness and also adapt to environmental problems and finally meet the demands of cleaner
production (Kuram et al., 2012).
Zhang et al. studied variations of tool-life and cutting force in
operating with minimal cutting fluid and dry machining on
Inconel 718. Their purpose was to reduce or completely omit the
cutting fluids in order to reduce environmental impacts and costs.
The results show that in some cases it is not possible to remove
the cutting fluid completely; because there was not sufficient
capacity of air for cooling. Although, it was reported that minimum quantity cooling lubrication (MQCL) with biodegradable
vegetable oil can significantly improve the machinability, such as
extension of tool life and reduction of cutting forces (Zhang et al.,
2012).
Deviilez et al. investigated surface roughness and especially
residual stresses during machining of Inconel 718 superalloy.
They were focused on the effect of dry machining on surface
integrity. Wet and dry turning tests were performed at various
cutting speeds and semi-finishing conditions using a coated
carbide tool. They reported that dry machining with a coated
carbide tool leads to potentially acceptable surface quality with
residual stresses and microhardness values in the machining
affected zone of the same order as those obtained in wet conditions when using the optimized cutting speed value (Devillez
et al., 2011).
Fratila and Caizar investigated the selection of optimum
machining parameters and cutting fluids using Taguchi method and
they concluded that in wet machining, feed rate is the most effective parameter on surface roughness. Also, they found that a
reduction in using cutting fluids results in less environmental
problems (Fratila and Caizar, 2011).
From published works, it is clear that there is not any study in
the machining of Inconel 725. Therefore, in this research, main
attention has been given to reduce or completely remove the
cutting fluids, and meet the demands of environment-friendly
cutting processes. In this research, tool coating, cutting speed,
feed rate and depth of cut were considered as input parameters
and it was attempted to completely omit the cutting fluids with
coating the carbide tool. First stage of experiments was carried
out using uncoated tool and biodegradable vegetable oil and
second stage was done in dry machining condition using coated
tool. Machining forces (cutting, feed and thrust forces) and surface roughness were measured as output parameters of each stage
of experiments. Analyze of variance (ANOVA) and response surface methodology (RSM) were used in order to analysis and
compare the results and investigate the feasibility of removing
cutting fluid. The RSM, as employed in the present investigation,
is a collection of mathematical and statistical techniques, which is
useful for the modeling and analysis of problems, in which a
response of interest is influenced by several variables and the
objective is to optimize the response (Lalwani et al., 2008). The
ANOVA is used for checking the validity of developed model and
studying the effect of machining parameters on responses
(Ezilarasan and Velayudham, 2013). In order to obtain good surface quality and lowest cutting forces, optimized cutting conditions have to be employed which needs a suitable modeling
technique for achieving better results. From the above, it is seen
that optimization is one of the important activities for the economy of manufactures, to predict the performance characteristics
of machining (Mandal et al., 2011).
A. Hosseini Tazehkandi et al. / Journal of Cleaner Production 80 (2014) 271e281
Table 1
Chemical analysis of the Inconel 725.
273
Table 3
Heat treatment of Inconel 725.
Composition
Cr
Fe
Al
Si
Mo
Mn
Nb
Ti
Ni
Material
1) Solution treatment
2) Intermediate age
3) Final age
Wt%
20
5
0.33
0.19
9.2
0.34
3.8
1.6
58
Inconel 725
1040 C, 2 h, air cool
730 C, 8 h, furnace
cool at 56 C/h
620 C, 8 h,
air cool
2. Experimental work
2.1. Workpiece material
The Inconel 725 material of 20 mm diameter and 250 mm
length was used for all experiments. The chemical analysis and
physical and mechanical properties of Inconel 725 at 500 C are
given in Table 1 and Table 2, respectively. Heat treatment of Inconel
725 was performed according to Table 3.
2.2. Machine and tools
Coated carbide inserts of ISO designation CNMG 120404-MF
with 1105 grade and chip breaker geometry and uncoated carbide
inserts of ISO designation CNMG 120404-MF with H13A grade by
Sandvik Company were used for the experiments. The cutting inserts were clamped on to a left hand tool holder having ISO
designation PCBNL 2020 M12 by SECO Company. A CNC lathe
(EMCOTURN 242 TC, Austria) was used for machining of the
workpieces. The machine has a maximum spindle speed of
4500 RPM and maximum power of 13 kW. In order to meet demands of the environment-friendly cutting processes, biodegradable vegetable oil (BioCut 3600) was selected as cutting fluid.
BioCut 3600 properties are given in Table 4.
2.3. Cutting forces and surface roughness measurement
Three components of the cutting forces; feed force (Fa), thrust
force (Fr) and cutting force (Fc) were recorded using a standard
quartz dynamometer (Kistler 9257B) which provides measurement
ranges from 5 to 5 kN. Instantaneous roughness criteria measurement (arithmetic mean roughness, Ra), for each cutting condition, were carried out by means of Mitutoyo Surftest 201
roughness meter. The examined length was 2.8 mm with a basic
span of 3. The measurements were repeated three times at three
reference lines equally positioned at 120 , and the reported result is
the average of these values. In order to analyze the machined surfaces, MV2300 Scanning Electron Microscopy (SEM) was used.
2.4. Design of experiments
The aim of the experiments was to analyze the effects of cutting
parameters on cutting forces and surface roughness during turning
of Inconel 725 in order to remove cutting fluid. The experiments
were carried out using full factorial method, and results were
analyzed with RSM. The RSM procedure is capable of determining a
relationship between independent input process parameters and
output data. This procedure includes 6 steps. These are, (1) defining
the independent input variables and the desired output responses,
(2) adopting an experimental design plan, (3) performing
regression analysis with the quadratic model of RSM, (4) calculating
the ANOVA for the independent input variables in order to find
parameters which significantly affect the response, (5) determining
the situation of the quadric model of RSM and finally, (6) optimizing, conducting confirmation experiment and verifying the
predicted performance characteristics (Aouici et al., 2012). The
selected cutting parameters were cutting speed, feed rate and
depth of cut. Various levels of cutting parameters are given in
Table 5. The results obtained from experiments with and without
cutting fluid are presented in Table 6.
3. Results and discussion
3.1. Test series plot
Diagrams of Fig. 1 and Fig. 2, which obtained from Table 6, show
the comparative variations in machining forces and surface
roughness in both dry machining with coated tool and wet
machining with uncoated tool. It is worthy of note that the other
two force components, namely thrust and cutting forces, have the
same behavior as Feed force represented in Fig. 1.
It is obvious that in experiment numbers 10 to 18, which is
related to cutting speed of 80 m/min, the whole of machining forces
(feed, thrust and cutting forces) in dry machining have lower values
than those in wet machining. Since the surface roughness values of
dry machining in experiment numbers 10 to 18 are lower than
those of wet machining, it can be inferred that at cutting speed of
80 m/min, cutting fluid can be removed from turning process of
Inconel 725 using coated tool. This could reduce the manufacturing
costs by getting rid of excessive cost of biodegradable vegetable oil
as well as environmental impacts.
3.2. Controllable parameters
3.2.1. Cutting speed
Diagrams of Fig. 3 demonstrate that at cutting speeds lower than
80 m/min, in both wet and dry machining, there is a general trend
of decreasing cutting forces (Fa, Fr and Fc) as cutting speed increases.
But at cutting speeds higher than 80 m/min, cutting forces rise with
increase of cutting speed. The same holds good in respect of surface
roughness, as it can be observed in Fig. 4. Since Inconel 725 is one of
the difficult-to-cut materials, in dry machining using coated tool,
friction is increased and as a result, produced heat on cutting surface is increased too. As Inconel 725 has a low value of heat transfer
coefficient, the produced heat is going to stay at the surface of
workpiece. This results in a condition that workpiece reaches to
elastic deformation and material flow zones. There is no doubt that
elastic deformation and material flow lead to an easier metal
removal operation. Therefore, dry machining induces lower cutting
Table 2
Physical and mechanical properties of Inconel 725 at 500 C.
Workpiece
material
Thermal conductivity
W/m.K
Density kg/m3
Young's
modulus GPa
Specific heat J/kg ºC
Tensile strength
MPa
Yield strength
(0.2% offset) MPa
Melting temperature ºC
Inconel 725
18.152
8310
177
519
1065
572
1325
274
A. Hosseini Tazehkandi et al. / Journal of Cleaner Production 80 (2014) 271e281
Table 4
Properties of biodegradable vegetable oil (BioCut 3600).
Cutting fluid
ISO grade
Specific gravity
Viscosity index
Pour point
Flash point
Copper corrosion
Biodegradability
BioCut 3600
36
0.913
150
18 C
260 C
Pass
>95%
Table 5
Various levels of machining parameters.
Symbol
Machining parameters
Unit
Level 1
Level 2
Level 3
A
B
C
Cutting Speed
Feed rate
Depth of cut
m/min
mm/rev
mm
60
0.1
0.40
80
0.15
0.80
100
0.20
1.20
forces as well as better surface finish. It is worth noting that a
coated tool was used in order to decline friction on cutting area and
prevent the surface of workpiece from reaching to plastic deformation zone. In contrast to dry machining, in machining using
cutting fluids, when cutting speed is increased, part of produced
heat on workpiece surface go away and the softening effect of heat
Table 6
The results of the turning tests on Inconel 725 with and without cutting fluid.
Tests
Cutting speed
(m/min)
Feed rate
(mm/rev)
Depth of cut
(mm)
Fa (N) wet
uncoated
Fa (N) dry
coated
Fr (N) wet
uncoated
Fr (N) dry
coated
Fc (N) wet
uncoated
Fc (N) dry
coated
Ra (mm) wet
uncoated
Ra(mm) dry
coated
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
60
60
60
60
60
60
60
60
60
80
80
80
80
80
80
80
80
80
100
100
100
100
100
100
100
100
100
0.10
0.10
0.10
0.15
0.15
0.15
0.20
0.20
0.20
0.10
0.10
0.10
0.15
0.15
0.15
0.20
0.20
0.20
0.10
0.10
0.10
0.15
0.15
0.15
0.20
0.20
0.20
0.4
0.8
1.2
0.4
0.8
1.2
0.4
0.8
1.2
0.4
0.8
1.2
0.4
0.8
1.2
0.4
0.8
1.2
0.4
0.8
1.2
0.4
0.8
1.2
0.4
0.8
1.2
199
261
331
202
250
357
223
298
391
155
227
336
161
235
344
185
267
383
174
238
321
172
248
327
191
287
378
227
291
361
232
280
387
253
328
421
154
225
331
159
230
338
180
256
375
204
268
351
202
278
357
221
317
408
314
397
476
325
410
510
369
447
617
254
355
495
255
364
509
292
416
604
265
361
470
259
363
465
306
473
621
372
455
535
383
468
568
427
505
675
252
354
495
253
359
491
282
400
592
323
419
528
317
421
530
364
531
679
521
654
811
607
672
833
564
722
913
389
582
706
464
573
729
474
593
859
502
564
744
459
571
752
511
640
848
612
744
901
697
762
922
654
812
1003
389
580
704
460
568
710
459
581
839
592
654
834
549
661
842
601
730
938
0.74
0.74
0.72
0.98
1.00
1.01
1.13
1.11
1.09
0.56
0.56
0.53
0.72
0.75
0.78
0.83
0.85
0.84
0.60
0.61
0.62
0.78
0.82
0.80
0.91
0.92
0.92
0.86
0.87
0.89
1.10
1.12
1.13
1.25
1.28
1.27
0.52
0.56
0.53
0.70
0.73
0.75
0.80
0.82
0.81
0.72
0.73
0.74
0.90
0.94
0.92
1.03
1.04
1.05
Fig. 1. Test series plot diagram of Feed force in machining with and without cutting
fluid.
Fig. 2. Test series plot diagram of Surface roughness in machining with and without
cutting fluid.
A. Hosseini Tazehkandi et al. / Journal of Cleaner Production 80 (2014) 271e281
275
Fig. 3. Effect of cutting speed variations on cutting forces in dry and wet machining.
on workpiece is limited. It can prevent the surface of workpiece
from reaching to elastic deformation zone and as a result, decrease
the cutting forces. This reduction in forces of wet machining, which
is due to softening effect, is not as many as those of dry machining
(Ulutan and Ozel, 2011). Therefore, it can be inferred that, an increase of cutting speed from 60 to 80 m/min, could result in a
complete removing of cutting fluids from machining process of
Inconel 725. Fig. 5 and Fig. 6 shows the SEM image of machined
surface in machining with cutting fluid and dry machining,
respectively. They clearly reveal how dry machining produces a
high quality surface rather than wet machining; hence, removing
cutting fluid not only causes a reduction in forces but also improves
the surface finish. At cutting speeds higher than 80 m/min, cutting
forces and surface roughness are increased once again. In this
processing condition, upward trend of cutting force and surface
roughness in dry machining is higher than that of wet machining.
Fig. 4. Effect of cutting speed variations on surface roughness in both dry and wet
machining.
Excessive growth of speed in dry machining using coated tool can
lead to significant damages to coating of tool. This phenomenon, in
combination with increase of produced heat and friction, can put
workpiece in plastic deformation zone and result in a growth in
cutting forces and finally a decline in surface finish (Zou et al.,
2009). So it can be concluded that in order to reach to the aim of
successfully removing cutting fluids from machining, cutting speed
should not exceed 80 m/min.
3.2.2. Feed rate
Fig. 7 show the effects of feed rate on machining forces in wet
and dry machining, respectively. From this figure it is clear that
there is a general trend of increasing cutting forces (Fa, Fr and Fc) as
feed rate increases. The same holds good in respect of surface
roughness, as it can be seen in Fig. 8. This can be attributed to the
Fig. 5. SEM image of Inconel 725 surface machined using uncoated tool and biodegradable vegetable oil in cutting speed of 80 m/min, feed rate of 0.1 mm/rev, depth of
cut of 0.4 mm.
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A. Hosseini Tazehkandi et al. / Journal of Cleaner Production 80 (2014) 271e281
Fig. 6. SEM image of Inconel 725 surface machined in dry condition using coated tool
in cutting speed of 80 m/min, feed rate of 0.1 mm/rev, depth of cut of 0.4 mm.
Fig. 8. Effect of feed rate on surface roughness in both dry and wet machining.
fact that an increase in feed rate results in formation of built e up e
edge by virtue of cold weld that take place between some pieces of
produced chips and cutting edge of tool. Formation of built e up e
edge makes grooves on workpiece surface and this in turn, not only
damages the surface of workpiece but also extremely increases the
cutting forces. In dry machining with coated tool, the coating of tool
can postpone formation of built e up e edge up to a point. It can
abate the increasing trend of cutting forces and surface roughness.
However, in machining with uncoated tool, high probability of
formation of built e up e edge induces higher cutting forces and
surface roughness (Settineri et al., 2008). Considering the results
that are presented in Table 6, it can be observed that in machining
with cutting speed of 80 m/min, even an increase in feed rate would
result in lower values of cutting forces and surface roughness
compare with those achieved in wet machining. Therefore, at cutting speed of 80 m/min, it is possible to remove the cutting fluid
from turning process with any feed rate. Fig. 9 and Fig. 10 show SEM
images of workpiece surface in processing with cutting speed of
80 m/min, feed rate of 0.2 mm and depth of cut of 0.4 mm/rev in
wet and dry machining, respectively. By comparison with Fig. 9,
which is related to wet machining, image of workpiece surface in
dry machining (Fig. 10) has less grooves and, hence, has better
surface finish. It is known that dry machining using excessive feed
rates causes significant damages to coating of tool and on the other
hand, since there is not any cutting fluid in dry machining, the
produced chips are willing to remain at surface of workpiece.
Because of these two reasons, built e up e edge was formed and
would be hardened during the turning process and, therefore, induces deep grooves on workpiece surface with plastic deformations
on the edges of these grooves. This can noticeably affect the mechanical properties of workpiece. In some cases, hardened built e
up e edge may break some parts of workpiece material and induces
various type of wear mechanisms, so it is impossible to remove the
Fig. 7. Effect of feed rate on cutting forces in dry and wet machining.
A. Hosseini Tazehkandi et al. / Journal of Cleaner Production 80 (2014) 271e281
Fig. 9. SEM image of workpiece surface in processing with cutting speed of 80 m/min,
feed rate of 0.2 mm and depth of cut of 0.4 mm/rev in wet machining with uncoated tool.
277
Fig. 12. Effect of depth of cut variations on surface roughness in both dry and wet
machining.
cutting fluid. On the other hand, selecting very low levels of cutting
speeds is not productive because of increase in special cutting energy, consumption power of machine, and machining time. In other
words, with the increase in consumption power of machine and
machining time, the utilization of cutting fluid and machining costs
considerably grow, and tool and workpiece are exposed to higher
temperatures for a long period.
Taking all above-mentioned discussion into consideration, it can
be concluded that in selection of feed rate for purpose of removing
cutting fluid, it is very important to choose the appropriate ranges
of this parameter.
Fig. 10. SEM image of workpiece surface in processing with cutting speed of 80 m/min,
feed rate of 0.2 mm and depth of cut of 0.4 mm/rev in dry machining with coated tool.
3.2.3. Depth of cut
According to Fig. 11 in both wet and dry machining an increase
in depth of cut results in increased cutting forces and Fig. 12 clearly
reveals that as cutting forces increase, so does the surface roughness of workpiece surface. When the cutting speed of machining is
80 m/min, increasing depth of cut induces higher material
removing rate. Also, tool coating plays an important role in
Fig. 11. Effect of depth of cut variations on cutting forces in dry and wet machining.
278
A. Hosseini Tazehkandi et al. / Journal of Cleaner Production 80 (2014) 271e281
reducing friction between tool cutting edge and produced chips
which can retard the extreme growth of produced heat. So, higher
amount of depth of cut results in higher cutting forces. However, in
wet machining using uncoated tool, as depth of cut increases,
produced heat on surface of workpiece increases too. It is known
that Inconel 725 has lower amount of heat transfer coefficient and,
on the other hand, cutting fluid can only transfer a small part of
produced heat. Therefore, excessive heat on cutting surface in
combination with higher material removing rate would raise cutting forces and deteriorate surface finish. Finally, increasing trend
of cutting forces in wet machining would be much more noticeable
than that of dry machining. It can be concluded that in machining
with cutting speed of 80 m/min, even in higher amount of depth of
cut, it is possible to remove cutting fluid from the process. One
interesting point is that in dry machining with coated tool, depth of
cut should not take values lower than radius of tool corner
(0.4 mm); otherwise, cutting operation will be carried out through
tool corner instead of cutting edge. In this condition, ploughing
phenomenon can cause severe growth in cutting forces and deterioration in surface finish (Ulutan and Ozel, 2011). Fig. 13 clearly
reveals how ploughing phenomenon can completely damage the
surface finish of workpiece.
3.3. Analysis of variance (ANOVA)
The ANOVA method measures the effect of input variables on
response variables through the relationship between these three
sets of variables. The purpose of ANOVA is to determine which
machining parameters highly affect the cutting forces and surface
roughness (Camposeco-Negrete, 2013). The statistical significance
of the fitted quadratic models was evaluated by the P-values of the
ANOVA. These values are given in Table 7 (for feed force-Dry),
Table 8 (for thrust force-Dry), Table 9 (for cutting force-Dry),
Table 10 (for surface roughness-Dry), Table 11 (for feed forceWet), Table 12 (for thrust force-Wet), Table 13 (for cutting forceWet) and Table 14 (for surface roughness-Wet). When P-values
are less than 0.05 (or 95% confidence), the obtained models are
considered to be statistically significant. It demonstrates that the
chosen parameters in model have significant effect on the responses. The F-value is an index used to check the adequacy of the
Table 7
Analysis of variance for feed force (N) e in dry machining with coated tool.
Term
DOF
Seq SS
Adj SS
Adj MS
F
P
Regression
linear
A
B
C
A2
B2
C2
A*B
A*C
B*C
Error
Total
R-Sq
9
3
1
1
1
1
1
1
1
1
1
17
26
96.32
149,704
131,269
1682
6689
122,897
16,098
475
736
0
421
705
2071
151,775
%
149,704
16,313
16,127
219
17
16,481
337
821
0
421
705
2071
16,633.8
5437.6
16,127
218.7
16.8
481.4
337.1
821.1
0
421.3
705.3
121.8
136.52
44.63
132.36
1.80
0.14
135.27
2.77
6.74
0.00
3.46
5.79
0.000
0.000
0.000
0.198
0.715
0.000
0.115
0.019
1.000
0.040
0.028
DOF ¼ Degree Of Freedom SS ¼ Sum of Squares MS or MSD ¼ Mean Square F ¼ Fvalue P ¼ P-value.
Dry ¼ dry machining with coated tool.
Wet ¼ machining with cutting fluid and uncoated tool.
model (Bouacha et al., 2010). In both dry and wet machining of
Inconel 725, cutting speed has remarkable effect on feed force and
cutting force. However, cutting speed and cutting force are in order
of the most effective parameters on thrust force. In the case of
Table 8
Analysis of variance for thrust force (N) e in dry machining with coated tool.
Term
DOF
Seq SS
Adj SS
Adj MS
F
P
Regression
linear
A
B
C
A2
B2
C2
A*B
A*C
B*C
Error
Total
R-Sq
9
3
1
1
1
1
1
1
1
1
1
17
26
95.70
344,329
281,721
4232
28,960
248,529
47,661
4397
1148
290
3391
5720
5432
349,760
%
344,329
53,015
51,343
3780
1136
48,797
3628
1471
290
3391
5720
5432
38,258.7
17,671.6
51,342.7
3779.6
1136.2
48,797.3
3627.9
1470.7
290.1
3390.9
5720.3
319.5
119.74
55.31
160.69
11.83
3.56
152.73
11.35
4.60
0.91
10.61
17.90
0.000
0.000
0.000
0.003
0.077
0.000
0.004
0.047
0.354
0.005
0.001
DOF ¼ Degree Of Freedom SS ¼ Sum of Squares MS or MSD ¼ Mean Square F ¼ Fvalue P ¼ P-value.
Dry ¼ dry machining with coated tool.
Wet ¼ machining with cutting fluid and uncoated tool.
Table 9
Analysis of variance for cutting force (N) e in dry machining with coated tool.
Fig. 13. SEM image surface of Inconel 725 in dry machining with cutting speed of
80 m/min, feed rate of 0.2 mm and depth of cut of 0.1 mm for showing ploughing
phenomenon.
Term
DOF
Seq SS
Adj SS
Adj MS
F
P
Regression
linear
A
B
C
A2
B2
C2
A*B
A*C
B*C
Error
Total
R-Sq
9
3
1
1
1
1
1
1
1
1
1
17
26
93.52
63,145
436,807
27,691
20,469
388,647
167,056
329
4349
44
526
4033
17,548
630,693
%
613,145
163,532
161,302
68
321
169,420
127
4563
44
526
4033
17,548
68,127
54,511
161,302
68
321
57,389
127
4563
44
526
4033
1032
66.00
52.81
156.27
0.07
0.31
164.13
0.12
4.42
0.04
0.51
3.91
0.000
0.000
0.000
0.800
0.584
0.000
0.730
0.051
0.839
0.485
0.065
DOF ¼ Degree Of Freedom SS ¼ Sum of Squares MS or MSD ¼ Mean Square F ¼ Fvalue P ¼ P-value.
Dry ¼ dry machining with coated tool.
Wet ¼ machining with cutting fluid and uncoated tool.
A. Hosseini Tazehkandi et al. / Journal of Cleaner Production 80 (2014) 271e281
Table 10
Analysis of Variance for Surface roughness (mm) ein dry machining with coated tool.
279
Table 13
Analysis of variance for cutting force (N) e in wet machining with uncoated tool.
Term
DOF
Seq SS
Adj SS
Adj MS
F
P
Term
DOF
Seq SS
Adj SS
Adj MS
F
P
Regression
linear
A
B
C
A2
B2
C2
A*B
A*C
B*C
Error
Total
R-Sq
9
3
1
1
1
1
1
1
1
1
1
17
26
98.32
1.19808
0.63877
0.16056
0.47694
0.00128
0.54101
0.01251
0.00056
0.00521
0.00002
0.00001
0.00819
1.20627
%
1.16808
0.57267
0.49409
0.03425
0.00066
0.53815
0.01190
0.00057
0.00521
0.00002
0.00001
0.00819
0.133120
0.190890
0.494090
0.034255
0.000657
0.538149
0.011905
0.000566
0.005208
0.000015
0.000008
0.000482
276.33
396.25
1025.64
71.11
1.36
1117.1
24.71
1.18
10.81
0.03
0.02
0.000
0.000
0.000
0.000
0.259
0.000
0.000
0.293
0.004
0.0861
0.897
Regression
linear
A
B
C
A2
B2
C2
A*B
A*C
B*C
Error
Total
R-Sq
9
3
1
1
1
1
1
1
1
1
1
17
26
91.73
489,771
452,132
28,691
23,545
400,897
27,855
284
4817
48
529
4107
17,638
507,409
%
489,771
30,067
29,954
36
401
28,876
95
5040
4684
48
529
4107
17,638
54,419
10,022.3
29,953.8
36.1
400.7
28,976.3
94.5
5040.2
1561.2
48.0
528.5
4107.0
1037.5
52.45
9.66
28.87
0.03
0.39
27.93
0.09
4.86
0.05
0.51
3.96
0.000
0.001
0.000
0.854
0.543
0.000
0.766
0.042
0.832
0.485
0.063
DOF ¼ Degree Of Freedom SS ¼ Sum of Squares MS or MSD ¼ Mean Square F ¼ Fvalue P ¼ P-value.
Dry ¼ dry machining with coated tool.
Wet ¼ machining with cutting fluid and uncoated tool.
DOF ¼ Degree Of Freedom SS ¼ Sum of Squares MS or MSD ¼ Mean Square F ¼ Fvalue P ¼ P-value.
Dry ¼ dry machining with coated tool.
Wet ¼ machining with cutting fluid and uncoated tool.
3.4. Regression equations
Table 11
Analysis of variance for feed force (N) e in wet machining with uncoated tool.
Term
DOF
Seq SS
Adj SS
Adj MS
F
P
Regression
linear
A
B
C
A2
B2
C2
A*B
A*C
B*C
Error
Total
R-Sq
9
3
1
1
1
1
1
1
1
1
1
17
26
95.73
138,468
134,374
1721
7240
125,413
1719
520
687
0
447
721
2167
140,635
%
138,468
2302
2163
248
14
1853
377
772
0
447
721
2167
15,385
767.3
2163
247.9
13.5
1853
377
772
0.3
446.6
720.7
127.5
120.69
6.02
16.97
1.94
0.11
7.87
2.96
6.06
0.00
3.50
5.65
0.000
0.005
0.001
0.181
0.749
0.001
0.104
0.025
0.960
0.079
0.029
DOF ¼ Degree Of Freedom SS ¼ Sum of Squares MS or MSD ¼ Mean Square F ¼ Fvalue P ¼ P-value.
Dry ¼ dry machining with coated tool.
Wet ¼ machining with cutting fluid and uncoated tool.
surface finish, these parameters are cutting and feed force. The
effectiveness of the models for feed force, thrust force, cutting force
and surface roughness can be further analyzed with help of the RSq values. A higher value of R-Sq is always desirable.
Table 12
Analysis of variance for thrust force (N) e in wet machining with uncoated tool.
The relationship between the factors and performance measurements were modeled by quartic regression. Using these
equations it is possible to achieve the values of machining force
components and surface roughness in both wet and dry conditions.
It should be noted that the amount of input parameters needs to be
within the selected ranges. As it is presented in ANOVA
Tables 7e14, the parameters with P values less than 0.05 have less
impact on results of experiments. However, in order to achieve the
maximum precision and minimum possible error in regression
models 1 to 8, even effect of the less effective machining parameters and counter-effect of them have been taken into account. The
cutting parameters of cutting speed, feed rate, and depth of cut are
represented by symbols of A, B, and C, respectively. The obtained
regression equations were as follows.
The feed force in dry machining model (Fa) is given below in Eq. (1).
Fa ¼ 1084:621:9Aþ0:1A2 þ73:7C2 þ0:7ACþ383:3BC
(1)
The thrust force in dry machining model (Fr) is given by Eq. (2).
Fr ¼ 2099 39:1A 3431B þ 0:2A2 þ 9889:3B2 þ 98:7C2
þ 2:2AC þ 1091:6BC
(2)
The cutting force model in dry machining (Fc) is given by Eq. (3).
Table 14
Analysis of variance for surface roughness (mm) e in wet machining with uncoated
tool.
Term
DOF
Seq SS
Adj SS
Adj MS
F
P
Term
DOF
Seq SS
Adj SS
Adj MS
F
P
Regression
linear
A
B
C
A2
B2
C2
A*B
A*C
B*C
Error
Total
R-Sq
9
3
1
1
1
1
1
1
1
1
1
17
26
95.98
308,682
290,198
4418
31,920
253,860
3278
4458
1212
280
3314
5941
4448
313,131
%
308,682
9127
5515
3758
1174
3608
3677
1539
280
3314
5941
4448
34,298
3042.2
5515.2
3757.7
1173.8
3607.8
3677.2
1539.1
280.3
3314.2
5940.7
261.7
131.07
11.63
21.08
14.36
4.49
13.79
14.05
5.88
1.07
12.67
22.70
0.000
0.000
0.000
0.001
0.049
0.002
0.002
0.027
0.315
0.002
0.000
Regression
linear
A
B
C
A2
B2
C2
A*B
A*C
B*C
Error
Total
R-Sq
9
3
1
1
1
1
1
1
1
1
1
17
26
98.25
0.759871
0.605476
0.131756
0.473689
0.000031
0.131131
0.018641
0.000291
0.003675
0.000649
0.0000080
0.008136
0.768007
%
0.759871
0.185149
0.126925
0.040946
0.000004
0.130791
0.018406
0.000225
0.003675
0.000649
0.000008
0.008136
0.084430
0.061716
0.126925
0.040946
0.000004
0.130791
0.018406
0.000225
0.003675
0.000649
0.000008
0.000479
176.41
128.95
265.21
85.55
0.01
273.28
38.46
0.47
7.68
1.36
0.02
0.000
0.000
0.000
0.000
0.930
0.000
0.000
0.502
0.013
0.260
0.897
DOF ¼ Degree Of Freedom SS ¼ Sum of Squares MS or MSD ¼ Mean Square F ¼ Fvalue P ¼ P-value.
Dry ¼ dry machining with coated tool.
Wet ¼ machining with cutting fluid and uncoated tool.
DOF ¼ Degree Of Freedom SS ¼ Sum of Squares MS or MSD ¼ Mean Square F ¼ Fvalue P ¼ P-value.
Dry ¼ dry machining with coated tool.
Wet ¼ machining with cutting fluid and uncoated tool.
280
A. Hosseini Tazehkandi et al. / Journal of Cleaner Production 80 (2014) 271e281
Table 15
The improved values for dry machining of Inconel 725.
Predicted values
Experimental values
Cutting speed
(m/min)
Feed rate
(mm/rev)
Depth of
cut (mm)
Feed force (N)
Thrust force (N)
Cutting force (N)
Surface roughness
(mm)
Error
82.2
82.2
0.1
0.1
0.4
0.4
158.34
164.13
257.27
269.22
428.01
441.79
0.492
0.51
5%
e
Table 16
The improved values for wet machining of Inconel 725.
Predicted values
Experimental values
Cutting speed
(m/min)
Feed rate
(mm/rev)
Depth of
cut (mm)
Feed force (N)
Thrust force (N)
Cutting force (N)
Surface roughness
(mm)
Error
89.6
89.6
0.1
0.1
0.4
0.4
160.4
167.29
256.7
266.9
430.45
452.40
0.51
0.54
5%
e
Fc ¼ 3280:8 69:4A þ 0:4A2 þ 173:8C2
(3)
The surface roughness model in dry machining (Ra) is given by
Eq. (4).
Ra ¼ 4:7 0:1A þ 10:3B þ 0:0007A2 17:9B2 0:02AB
(4)
The feed force in wet machining model (Fa) is given below in Eq.
(5).
Fa ¼ 534:9 8:1A þ 0:04A2 þ 71:5C2 þ 387:5BC
(5)
The thrust force in wet machining model (Fr) is given by Eq. (6).
Fr ¼ 1050:8 12:8A 34:2B 195C þ 0:06A2 þ 9956B2
þ 101C2 þ 2:2AC þ 1112:5BC
(6)
The cutting force model in wet machining (Fc) is given by Eq. (7).
Fc ¼ 1699 30A þ 0:2A2 þ 182:6C2
(7)
The surface roughness model in wet machining (Ra) is given by
Eq. (8).
Ra ¼ 2:3 0:06A þ 11:3B þ 0:0004A2 22B2 0:02AB
(8)
3.5. Optimization of cutting conditions
It was assumed that the optimal manufacturing conditions for
turning of Inconel 725 without cutting fluid are those with minimum values of cutting forces (Fa, Fr and Fc) and surface roughness
(Ra) during the turning process. It is worth noting that, although
main aim of this research is removing cutting fluid from machining
process, some operating condition make it mandatory to utilize
cutting fluid. So, additional study has been presented to optimizing
consumption of cutting fluid during wet machining of Inconel 725.
The objective of optimizing the turning process of Inconel 725
with and without cutting fluid is to achieve the minimum possible
level of machining force components and maximum level of surface
finish. Therefore, the optimization has been carried out with taking
the attainment of minimum cutting, feed, and thrust forces and
maximum surface finish into account. The experiments are also
conducted practically using the provided numbers for the parameters A (cutting speed), B (feed rate) and C (depth of cut) in both dry
and wet machining conditions by Minitab software in order to
demonstrate the differences between the values of predicted responses and the experimental values. The results of RSM procedure
have been validated using the output of experiments and it was
confirmed that value of error in RSM method in dry and wet conditions is less than 5 percent. Table 15 and Table 16 show the RSM
optimization results for cutting forces and surface roughness in dry
and wet machining.
4. Conclusion
In this study effects of process parameters (which include
cutting speed, feed rate and depth of cut) and tool coating on
machining forces and surface roughness were investigated in both
dry and wet machining of nickel-based superalloy Inconel 725 in
order to remove the cutting fluid and meet environmental demands. Considering environmental problems, Biodegradable
vegetable oil was utilized as cutting fluid in wet machining. All
experiments were carried out in full factorial method and they
were analyzed using RSM and ANOVA methods. Finally, optimized
parameters were achieved for both dry and wet machining. The
foremost conclusions which can be drawn are as follows:
Removal of cutting fluid in the above-mentioned conditions
result in reduced production costs and fluid production expenses. This in turn reduces costs of removing it from the machine and the parts and eliminates destructive effect of these
fluids on the environment and human health.
The role of tool coating in reduction of cutting forces and
improving surface finish is much more effective than using
cutting fluid. Since Inconel 725 is one of the difficult-to-cut
materials, excessive heat was produced during turning and
remained on workpiece surface due to low heat transfer capacity of cutting fluid. However, coating of tool reduced friction
and as a result, made it possible to remove the cutting fluid.
When Inconel 725 was machined with cutting speed of 80 m/
min, regardless of the values of feed rate and depth of cut, it was
quite feasible to eliminated cutting fluid from turning process.
In order to reach to the aim of successfully removing cutting
fluids from wet and dry machining, cutting speed should not
exceed 80 m/min, because it induced higher cutting forces and
deteriorated surface finish.
Excessive increase of cutting speed could damage tool coating
and make it practically impossible to remove cutting fluid.
There was a general trend of increasing cutting forces and surface roughness as feed rate and depth of cut increase.
References
Aouici, H., Yallese, M.A., Chaoui, K., Mabrouki, T., Rigal, J.-F., 2012. Analysis of surface roughness and cutting force components in hard turning with CBN tool:
prediction model and cutting conditions optimization. Measurement 45,
344e353.
Bouacha, K., Yallese, M.A., Mabrouki, T., Rigal, J.-F., 2010. Statistical analysis of surface roughness and cutting forces using response surface methodology in hard
turning of AISI 52100 bearing steel with CBN tool. Int. J. Refract. Metals Hard
Mater. 28, 349e361.
Camposeco-Negrete, C., 2013. Optimization of cutting parameters for minimizing
energy consumption in turning of AISI 6061 T6 using Taguchi methodology and
ANOVA. J. Clean. Prod. 53, 195e203.
Davim, J.P., 2013. Green Manufacturing Processes and Systems. Springer, London,
UK.
A. Hosseini Tazehkandi et al. / Journal of Cleaner Production 80 (2014) 271e281
Davoodi, B., Tazehkandi, A.H., 2014. Experimental investigation and optimization of
cutting parameters in dry and wet machining of aluminum alloy 5083 in order
to remove cutting fluid. J. Clean. Prod. 68, 234e242. http://dx.doi.org/10.1016/
j.jclepro.2013.12.056.
Devillez, A., Le Coz, G., Dominiak, S., Dudzinski, D., 2011. Dry machining of Inconel
718, workpiece surface integrity. J. Mater. Process. Technol. 211, 1590e1598.
Ezilarasan, C., Velayudham, A., January 2013. An experimental analysis and
measurement of process performances in machining of nimonic C-263
super alloy. Measurement 46 (1), 185e199. http://dx.doi.org/10.1016/
j.measurement.2012.06.006.
Fratila, D., Caizar, C., 2011. Application of Taguchi method to selection of optimal
lubrication and cutting conditions in face milling of AlMg 3. J. Clean. Prod. 19,
640e645.
Groover, M.P., 2007. Fundamentals of Modern Manufacturing: Materials Processes,
and Systems. Wiley. com, United States of America.
Kuram, E., Ozcelik, B., Bayramoglu, M., Demirbas, E., Simsek, B.T., 2012. Optimization
of cutting fluids and cutting parameters during end milling by using D-optimal
design of experiments. J. Clean. Prod..
Kuram, E., Ozcelik, B., Demirbas, E., 2013. Environmentally Friendly Machining:
Vegetable Based Cutting Fluids, Green Manufacturing Processes and Systems.
Springer, pp. 23e47.
Lalwani, D., Mehta, N., Jain, P., 2008. Experimental investigations of cutting parameters influence on cutting forces and surface roughness in finish hard
turning of MDN250 steel. J. Mater. Process. Technol. 206, 167e179.
281
Lawal, S.A., Choudhury, I.A., Nukman, Y., 2013. A critical assessment of lubrication
techniques in machining processes: a case for minimum quantity lubrication
using vegetable oil-based lubricant. J. Clean. Prod. 41, 210e221.
Mandal, N., Doloi, B., Mondal, B., Das, R., 2011. Optimization of flank wear using
Zirconia Toughened Alumina (ZTA) cutting tool: Taguchi method and Regression analysis. Measurement 44, 2149e2155.
€kkaya, H., 2007. The effect of cutting speed and cutting tool
Nalbant, M., Altın, A., Go
geometry on machinability properties of nickel-base Inconel 718 super alloys.
Mater. Des. 28, 1334e1338.
Sarıkaya, M., Güllü, A., 2014. Taguchi design and response surface methodology
based analysis of machining parameters in CNC turning under MQL. J. Clean.
Prod. 65, 604e616.
Settineri, L., Faga, M.G., Lerga, B., 2008. Properties and performances of innovative
coated tools for turning inconel. Int. J. Mach. Tools Manuf. 48, 815e823.
Ulutan, D., Ozel, T., 2011. Machining induced surface integrity in titanium and nickel
alloys: a review. Int. J. Mach. Tools Manuf. 51, 250e280.
Weinert, K., Inasaki, I., Sutherland, J., Wakabayashi, T., 2004. Dry machining and
minimum quantity lubrication. CIRP Ann. Manuf. Techn. 53, 511e537.
Zhang, S., Li, J., Wang, Y., 2012. Tool life and cutting forces in end milling Inconel 718
under dry and minimum quantity cooling lubrication cutting conditions.
J. Clean. Prod. 32, 81e87.
Zou, B., Chen, M., Huang, C., An, Q., 2009. Study on surface damages caused by turning
NiCr20TiAl nickel-based alloy. J. Mater. Process. Technol. 209, 5802e5809.