Engineering, 2010, 2, 453-460
doi:10.4236/eng.2010.26059 Published Online June 2010 (http://www.SciRP.org/journal/eng)
Influence of Cutting Speed, Feed Rate and Bulk Texture on
the Surface Finish of Nitrogen Alloyed Duplex Stainless
Steels during Dry Turning
D. Philip Selvaraj1, Palanisamy Chandramohan2
1Faculty of School of Mechanical Sciences, Karunya University, Coimbatore, India
2Faculty of Mechanical Engineering, Coimbatore institute of Engineering and Technology, Coimbatore, India
Received February 1, 2010; revised March 19, 2010; accepted March 25, 2010
Abstract
This paper presents the results of experimental work carried out in dry turning of cast duplex stainless steels
(ASTM A 995 Grade4A and ASTM A 995 Grade5A) using TiC and TiCN coated cemented carbide cutting
tools. The turning tests were conducted at five different cutting speeds (80, 100, 120, 140 and 160 m/min)
and three different feed rates (0.04, 0.08 and 0.12 mm/rev) with a constant depth of cut (0.5 mm). The influ-
ence of cutting speed and feed rate on the machined surface roughness was investigated. Texture analysis
(Bulk) was also carried out to study the impact of preferred orientation on the resulting surface roughness.
The result reveals that the increasing cutting speed decreases the surface roughness till a particular point and
then increases whereas; the surface roughness value decreases with the decreasing feed rate. Presence of al-
pha fiber (Bulk texture analysis) in the austenite phase of 4A work piece material leads to better surface fin-
ish. Among both the grades, surface finish of grade 4A is better than grade 5A work piece material.
Keywords: Surface Roughness, Duplex Stainless Steel, Dry Turning, Coated Carbide Tool
1. Introduction
Over the past two decades, the applications of stainless
steel materials have increased enormously in various
fields. The attractive combination of excellent corrosion
resistance, a wide range of strength levels including str-
ength retention at cryogenic and elevated temperatures,
good formability, and an aesthetically pleasing appear-
ance have made stainless steel materials the preferred
choice for a diverse range of applications, from critical
piping components in boiling water nuclear reactors to
the ubiquitous kitchen sink [1].
Machinability is a measure of ease with which a work
material can be satisfactorily machined. The machinabil-
ity aspect is of considerable importance for production
engineers to know in advance about the machinability of
a work material so that the processing can be planned in
an efficient manner [2]. Ferritic stainless steels (FSS) are
known for their corrosion resistance and Austenitic
stainless steels (ASS) for better mechanical properties
like strength and deep drawability. But their machinabil-
ity is more difficult than other alloy steels due to the
reasons like low heat conductivity, high built up edge
tendency, high deformation hardening etc. Duplex stainless
steel (DSS) is a material that combines the benefits of
both FSS and ASS by proper balancing of ferrite and
austenite. It is apparent that a balance of ferrite and aus-
tenite phase in a microstructure made it realistic for ap-
plications, which demand better corrosion resistance and
improved mechanical properties [1].
Ibrahim Ciftci investigated the Machining characteris-
tics of austenitic stainless steels (AISI 304 and AISI 316)
using CVD multi layer coated carbide tools. The influ-
ence of work piece grade, cutting tool coating top layer
and cutting speed were investigated on cutting forces and
machined surface roughness. With increasing cutting
speed the surface finish values decrease until a minimum
value and beyond which they increase [3]. Ihsan Korkut
et al. carried turning tests to determine optimum ma-
chining parameters for machining of austenitic stainless
steel. Surface roughness values were found to decrease
with increasing cutting speeds [4]. The active wear and
failure mechanism of TiN coated cemented carbide tools
with internal coolant supply when drilling of HIP ed P/M
Duplok 27 and conventionally produced stainless steel
ASTM A81901A was investigated by Jukka Paro et al.

D. P. SELVARAJ ET AL. 454
In P/M produced duplex stainless steel there are more
hard oxide particles causing machining difficulties from
the wear point of view. High strength and work harden-
ing rate also cause difficulties from the machining-point
of view [5]. Effects of free cutting additives such as S,
Ca, Cu and Bi on the machinability of work materials
SUS303, SUS303Cu, SUS304 and SUS316 were studied
by Akasawa et al. The resulfurization deteriorated the
surface texture at lower cutting speeds in dry cutting.
Calcium treated steels with inclusions of an anorthite
composition exhibited a better surface than those of plain
austenitic steels [6].
Machining of cast austenitic Stainless steels with car-
bide tools were studied by Agrawal et al. The relative
performance of coated and uncoated carbide tools in the
machining of cast austenitic Stainless steels were as-
sessed with reference to cutting force requirement (both
horizontal force –Px and vertical force –Pz), tool rake-
face wear and chip characteristics. It was reported that
the composition of stainless steel work piece influences
machinability [7]. Machinability of austenitic Stainless
steel SS303 was investigated by O’Sullivan and Cotterell.
An on-line detection technique (Acoustic Emission tech-
nique) was developed to detect the work hardenability of
austenitic Stainless steels SS303 during machining [8].
Active tool wear and failure mechanisms of TiN coated
cemented carbide tools while machining X5CrMnN18
austenitic stainless steel, was investigated by Jukka Paro
et al. By nitrogen alloying, austenite gets stabilized and
the strength of austenitic stainless steel is increased,
thereby work hardening is promoted. Higher N content
decreases machinability [9].
Noordin et al. investigated the usability of coated
TiCN based cermet and coated carbide cutting tools to
turn tempered martensitic stainless tool steel with hard-
ness in the range of 43-45 HRC under dry cutting condi-
tions [10]. Thamizhmanii and Hasan investigated surface
roughness and flank wear on hard AISI 440 C material
with different operating parameters using CBN and PCBN
tools [11]. Anthony Xavior and Adithan investigated the
influence of cutting fluids on tool wear and surface
roughness during turning of AISI 304 with carbide tool.
An attempt has been made to identify the influence of
coconut oil in reducing the tool wear and surface rough-
ness during turning process [12].
Texturing influences the properties of the work mate-
rial to a remarkable extent. The extent of texture devel-
opment in various steels, aluminium alloys and Zr-Nb
alloys has been studied by several researchers [13]. The
major BCC and FCC texture components are listed by
name, Euler angle and Miller indices {h k l} <u v w> in
the Table 1. The first indices {h k l} describe the crys-
tallographic plane parallel to the sheet surface whereas
the second indices <u v w> indicate the direction parallel
to the rolling direction [14].
From the literature stated above, it becomes clear that
Table 1. Major BCC and FCC texture components.
CRYSTAL
LATTICE NAME φ1 Φ φ2
{hkl}
<uvw>
BCC
Rotated
Cube 0° 0
° 45°
{001}
<110>
0° 15° 45°
{115}
<110>
Inverse
Brass 0° 35° 45°
{112}
<110>
0° 55° 45°
{111}
<110>
Inverse
Copper 30° 55° 45°
{112}
<110>
FCC Cube 0° 0
° 0 °
{001}
<100>
Goss 0° 45° 0
°
{011}
<100>
Brass 35° 45° 0
°
{011}
<211>
Rotated
Goss 90° 45° 0
°
{011}
<011>
S 59° 37° 63°
{123}
<634>
C (Cop-
per) 90° 35° 45°
{112}
<111>
R-Com-
ponent
{123}
<412>
machinability studies have been carried out by various
researchers in the cast and mechanically formed stainless
steels. Still there remains some difficulty in the day to
day machining activities of stainless steels; particularly
in nitrogen alloyed duplex stainless steels. This reveals
the fact that still more investigation needs to be carried
out through a different procedure to find a reasonable
solution.
Surface quality of the machined work piece is de-
pendent on the grain orientation (Texture) of the base
material and the cutting conditions used during machin-
ing process. Surface roughness is an important index to
evaluate cutting performance in turning operation. It
plays vital role in functioning and fatigue life of the
component.
Therefore in this work, studies on machinability are
carried out to understand the influence of the cutting
speed, feed rate and work piece material (Bulk texture)
on the surface finish of ASTM A 995 GRADE 4A and
ASTM A 995 GRADE 5A cast duplex stainless steels
during dry turning using TiC and TiCN coated cemented
carbide tools.
2. Experimental Procedure
The work piece materials used were ASTM A 995
GRADE 4A and ASTM A 995 GRADE 5A cast duplex
steel specimen in cylindrical form. The dimensions of the
specimens were 300 mm length and 80 mm diameter.
The chemical compositions and mechanical properties of
the work piece materials are given in Tables 2 and 3
respectively.

D. P. SELVARAJ ET AL.455
Table 2. Composition of ASTM A 995 GRADE-4A and 5A.
Material C Si Mn S P Cr Ni Mo Cu N
4A 0.028 0.650 0.710 0.006 0.027 22.160 5.660 3.330 0.140 0.240
5A 0.028 0.670 0.870 0.005 0.028 25.100 6.630 4.160 - 0.170
Table 3. Mechanical properties of ASTM A 995 GRADE-4A and 5A.
Material Tensile Strength
(MPa)
Yield Strength
(MPa)
Elongation
%
Hardness
(BHN)
4A 732 595 30.2 212
5A 741 546 32.2 223
Table 4. Experimental results for surface roughness.
Surface roughness
(μm)
Exp
No
Cutting speed
(m/min)
Feed rate
(mm/rev)
Depth of cut
(mm) 4A GRADE 5A GRADE
1 80 0.04 0.5 0.60 1.20
2 100 0.04 0.5 0.53 1.05
3 120 0.04 0.5 0.58 1.16
4 140 0.04 0.5 0.72 1.27
5 160 0.04 0.5 0.85 1.35
6 80 0.08 0.5 0.68 1.25
7 100 0.08 0.5 0.57 1.17
8 120 0.08 0.5 0.60 1.24
9 140 0.08 0.5 0.76 1.30
10 160 0.08 0.5 0.93 1.42
11 80 0.12 0.5 0.85 1.32
12 100 0.12 0.5 0.64 1.25
13 120 0.12 0.5 0.76 1.30
14 140 0.12 0.5 0.89 1.42
15 160 0.12 0.5 0.97 1.48
The machining tests were performed by single point
continuous turning on a Kirloskar Turn master-35 me-
dium duty lathe, with a variable speed of up to 1500 rpm
and a power rating of 3 HP. The tests were conducted
without the application of cutting fluid (dry turning). The
cutting tools used were TiC and TiCN coated carbide
inserts produced by Tagutec and had SNMG 120408 MT
TT5100 Tagutec designation. These inserts were clamped
mechanically on a pin and hole type rigid tool holder
with a general specification of PSBNR 2525M12. Cut-
ting speeds used ranges from 80 to 160 m/min. The cut-
ting speed was increased in steps of 20 m/min. Feed rates
used ranges from 0.04 to 0.12 mm/rev. The feed rate was
increased in steps of 0.04 mm/rev. The depth of cut was
kept as constant i.e., 0.5 mm. Surface roughness meas-
urement was carried out on the machined surfaces using
a TIME surface roughness tester (TR100). The Piezo-
electric stylus was used for taking the surface roughness
measurements. Three measurements were made on the
machined surface at three different locations and the av-
erage value was taken.
A part of the base work piece material (before ma-
chining) was subjected to measurements of bulk crystal-
lographic texture. The measurements were obtained at
the mid thickness sections of the rolling plane (contain-
ing rolling directions (RD) and transverse directions
(TD)). All samples were electro polished using the stan-
dard technique [15]. For the bulk texture measurement, a
PANalytical materials research diffraction (PANalytical,
Almelo, The Netherlands) system was used. The orienta-
tion distribution functions (ODFs) were obtained through
the inversion of four incomplete X-ray pole figures and
the software MTM-FHM [16]. The software uses the
standard series-expansion technique [17].
3. Results and Discussions
The machining tests were conducted with different cut-
ting parameters and the surface roughness was measured.
Experimental results for the surface roughness are given
in Table 4.

D. P. SELVARAJ ET AL. 456
3.1. Effect of Cutting Speed on Surface
Roughness
The influence of cutting speed on surface roughness du-
ring dry turning of ASTM A 995 GRADE 4A and 5A are
shown in Figures 1 and 2 respectively for three different
feed rates (0.04, 0.08 and 0.12 mm/rev).
It is observed in both the figures that the surface finish
decreases with cutting speed of up to 100 m/min. With
increasing the cutting speed further, the surface rough-
ness of the machined work pieces seams to increase for
both the grades. This is due to the increased friction be-
tween work piece and tool interface, which eventually
increases the temperature in the cutting zone. Hence the
shear strength of the material reduces and the material
behaves in a ductile fashion. Moreover the duplex stain-
less steel is sticky in nature which makes the chips to
detach from the work piece with utmost difficulty, there-
by increasing the surface roughness.
The decrease in surface roughness with increasing cut-
ting speed up to 100 m/min is due to the decreasing built
up edge (BUE) formation tendency with increasing cut-
ting speed. However, further increase in cutting speed
causes an increase in surface roughness. This can be at-
tributed to the increasing cutting tool nose wear at higher
cutting speeds of 120, 140 and 180 m/min. It can also be
observed that the minimum Ra of machined surfaces is
obtained when cutting speed is at 100 m/min.
Cutting speed vs surface roughness - 4A
0
0.5
1
1.5
6080100 120 140160 180
Cutting speed, V mm/min
Surface roughness,Ra
(Microns)
f - 0.04 mm/rev
f - 0.08 mm/rev
f - 0.12 mm/rev
Figure 1. Cutting speed vs. Surface finish-4A.
Cutting speed vs surface roughness -5A
0
0. 5
1
1. 5
6080100120140 160 180
Cutting speed, V mm/min
Surface roughness, Ra
(Microns)
f - 0.04 mm/rev
f- 0.08 mm/rev
f - 0.12 mm/rev
Figure 2. Cutting speed vs. Surface finish-5A.
3.2. Effect of Feed Rate on Surface Roughness
Figure 3 shows the influence of feed rate on surface
roughness during dry turning of ASTM A 995 GRADE
4A with five different cutting speeds (80, 100, 120, 140
and 160 m/min). Figure 4 shows the influence of feed
rate on surface roughness during dry turning of ASTM A
995 GRADE 5A with five different cutting speeds (80,
100, 120, 140 and 160 m/min). It is observed that the sur-
face roughness increases with the increase in feed rate.
It can also be observed that the minimum Ra of ma-
chined surfaces is obtained at the feed rate of 0.04 mm/rev
for both the grades. As the feed rate increased from
0.04 mm/rev to 0.12 mm/rev, the surface roughness val-
ues increase linearly in all the selected cutting speeds.
This is due to the widening in the area of contact and
changes in the force per unit length, resulting in great
distortion of sticky chip.
3.3. Effect of Work Piece Material (Bulk Texture)
on Surface Roughness
The influence of work piece grade on surface roughness
during dry turning of ASTM A 995 GRADE 4A and
ASTM A 995 GRADE 5A with five different cutting
speeds (80, 100, 120, 140 and 160 m/min) and feed rate
of 0.04, 0.08 and 0.12 mm/rev are shown in Figures 5-7
respectively.
It is observed that the surface finish of the machined
Feed rate vs surface roughness - 4A
0
0. 2
0. 4
0. 6
0. 8
1
00.04 0.080.12 0.16
Feed rate, f mm/rev
Surface
rou gh n ess,Ra(Micro n s)
V-80 m/min
V-100 m/min
V-120 m/min
V-140 m/min
V-160 m/min
Figure 3. Feed vs. Surface finish-4A.
Feed rate vs surface roughness - 5A
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
00.04 0.080.12 0.16
Feed rate, f mm/rev
Surface roughness, Ra
(Micro n s)
V - 80 m/min
V - 100 m/min
V - 120 m/min
V - 140 m/min
V - 160 m/min
Figure 4. Feed vs. Surface finish-5A.

D. P. SELVARAJ ET AL. 457
Cutting speed vs surface roughness 4A and 5A
0
0.5
1
1.5
6080100 120 140160 180
Cutting speed
Surface roughness,Ra
(microns)
4A GRADE
5A GRADE
Cutting speed vs surface roughness 4A and 5A
0
0. 5
1
1. 5
6080100 120140 160180
Cutting speed, V m/min
Surface roughness,Ra
(microns)
4A GRADE
5A GRADE
Figure 5. Cutting speed vs. Surface finish for feed rate
0.04 mm/rev. Figure 7. Cutting speed vs. Surface finish for feed rate
0.12 mm/rev.
work pieces seams to be better with 4A grade material
than 5A grade material in all the cutting speeds and feed
rates. Generally stainless steels are regarded as more
difficult to machine than carbon and low alloy steels due
to their high strength and ductility, high work hardening
tendency and poor thermal conductivity. In addition,
variations in the chemical compositions of different
grades of duplex stainless steels lead to the difference in
the formation of micro grains. These grain structure and
orientation (Texture) determine the mechanical proper-
ties of the base work piece material. The bulk texture
formation in austenite and ferrite phase of grade 4A and
5A are shown in Figures 8 and 9 respectively.
Cutting speed vs surface roughness 4A and 5A
0
0. 5
1
1. 5
6080100 120 140160180
Cutting speed,V m/min
Surface roughness,Ra
(mi cr ons)
4A GRADE
5A GRADE
Figure 6. Cutting speed vs. Surface finish for feed rate
0.08 mm/rev.

D. P. SELVARAJ ET AL. 458
Standard
Figure 8. ODFs of austenite phase.

D. P. SELVARAJ ET AL. 459
Standard
Figure 9. ODFs of ferrite phase.
Alpha fiber and beta fiber can be noticed in both the
standard ODFs of austenite and ferrite. This fiber texture
is considered to be the contributing factor for the forma-
tion of preferred orientation that lead to better mechani-
cal properties, particularly deep drawability with higher
hardness [18]. The alpha ferrite and gamma austenite are
supposed to have <100> and <110> fiber textures re-
spectively but only partial fibers are visible in both the
ODF’s of 4A and 5A alloys. The formation of fiber tex-
ture that connects Goss and Brass orientations in the
ODF of austenite phase is relatively better in 4A when
compared to that in ODF of austenite phase of 5A alloy.
Therefore this fiber texture would have contributed to
better surface finish of machined 4A alloy than that of
machined 5A alloy.
4. Conclusions
Dry turning tests were performed on ASTM A 995
GRADE 5A and ASTM A 995 GRADE 4A duplex
stainless steels using TiC and TiCN coated carbide cut-
ting tools. The influence of cutting speed, feed rate and
bulk texture on surface roughness was investigated.
Based on the results obtained; the following conclusions
can be drawn.
Cutting speed is found to have a significant effect on
the roughness of the machined surface. With increasing
cutting speed, surface roughness values decreases until a
minimum value and then increases. Higher surface rough-
ness values at lower cutting speeds are attributed to the
BUE formation tendency. Wear of cutting edge nose
radius is responsible for the high surface roughness val-
ues at higher cutting speeds. Feed rate is found to have a
significant effect on the roughness of the machined sur-
face. Better surface finish is noticed at lower feed rate
than in higher feed rate. Grade 4A yields better surface
finish at all cutting speeds and feed rates employed than
in Grade 5A which is attributed to the presence of partial
fiber texture in the austenite phase of 4A work piece ma-
terial.
5. Acknowledgements
This work is supported by National Facility of Texture
and Orientation Imaging Microscopy―Dept of Science
and Technology, India at IIT-Bombay and Karunya Uni-
versity―Coimbatore, India (Karunya Short Term research
Grant). The authors are grateful to Dr. S. Darius Gnana-
raj, Dr. A. S. Varadarajan and Mr. Jones Robin, Karunya
University for their technical support. The authors are
also grateful to Prof K. Smiles Mascarenhas, CIET-
Coimbatore for his help in improving the write-up (Eng-
lish language) of this article.
6
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