1) The document investigates using water vapor as an environmentally friendly coolant and lubricant for machining the titanium alloy Ti-6Al-4V. 2) Experiments show that using water vapor decreases cutting forces by 30-35% and cutting temperature by 15-10% compared to dry and wet cutting. It also improves surface finish. 3) Water vapor is an effective coolant and lubricant for titanium machining due to the polarity, small diameter, and high speed of water molecules which allows them to rapidly penetrate the cutting zone.

1. Advanced Materials Research Vols. 139-141 (2010) pp 681-684
Online available since 2010/Oct/19 at www.scientific.net
© (2010) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMR.139-141.681
Machining Process of Titanium Alloy Based on Green Cooling and
Lubricating Technology
ZHANG Yue1,a, HAN Li1, LI Qidong2, SUN Taili2, ZHANG Xichuan2
1
School of Mechanical Engineering, Shenyang University of Technology, China
2
Schoolof Material Science and Engineering, Shenyang University of Technology, China
a
zhangyue80@yeah.net
Keywords: Green machining, Water steam, Coolant, Lubricant, Turning, Titanium alloy.
Abstract. The machining process of titanium alloys always need special control by using coolant and
lubricant as it is one of the difficult-to-cut materials. To achieve green cutting of titanium alloy
Ti-6Al-4V with water vapor cooling and lubricating, a minitype generator is developed. Compared to
dry and wet cutting, the using of water vapor decreases the cutting force and the cutting temperature
respectively; enhances the machined surface appearance. Water vapor application also improves
Ti-6Al-4V machinability. The excellent cooling and lubricating action of water vapor could be
summarized that water molecule has polarity, small diameter and high speed, can be easily and
rapidly to proceed adsorption in the cutting zone. The results indicate that the using of water vapor has
the potential to attain the green cutting of titanium alloy instead of cutting floods.
Introduction
Titanium alloys are widely used in the aerospace, nuclear, chemical, biomedical industries and so on,
due to their excellent combination of low density, high strength to weight ratio, excellent corrosion
resistance and biocompatibility. At same times, titanium alloys are recognized as a difficult-to-cut
material [1-6]. The cutting characteristics include that: The tool–chip contact length is short. The
cutting temperature is very high. A poor tool life results from the high cutting temperatures. Titanium
has a strong chemical reactivity with most tool materials. Titanium alloy has a small cutting
deformation coefficient. Therefore cutting fluids and additives, such as water-based emulsion, are
usually applied in cutting of titanium alloy. However, some of them, especially extreme pressure
additives, contain Cl, S or P compounds which endanger to environment and people health. In the 21st
century, it is a global tendency to developing green cutting technology[4-8], for titanium alloy cutting,
such as liquid nitrogen jet, cryogenic nitrogen gas, high pressure water jet, and so on[7-10]. Water
vapor was used as environment-friendly coolant and lubricant in metal cutting [3]. The water vapor
(WV) application can reduce the cutting forces and prolong the carbide tool life in cutting of medium
carbon and stainless steel, compared to dry and wet cutting [4]. And in the cutting of difficult-to-cut
materials, water vapor can also act as coolant and lubricant [1]. There are many methods to deal with
the machining problem of titanium alloys [4]. And the aim of this paper is to investigate the control of
machining process in turning of Ti-6Al-4V by uncoated WC/Co inserts, based on green cooling and
lubricating technology by using water vapor.
Experiments
Water Vapor Generator. A special generating system for turning is developed to produce water
vapor with a primary resistance heater powered by 0.6kw and a secondary heater by 0.2kw, as shown
in Figure1. The secondary heater is controlled by a PID controller, and the temperature of water vapor
can be kept in the range of 125°C±5°C. There are two water level sensors in the generator to detect the
water line. When the water line is low, the water pump has been infusing water from tank into the
generator, until the water line up to the high sensor. An electromagnetic valve is droved by a
pushbutton for water vapor spurting out.
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,
www.ttp.net. (ID: 161.139.147.200-27/06/12,07:27:52)

2. 682 Manufacturing Engineering and Automation I
Experiment Equipments and Materials. As shown in Fig.1, cutting experiments were carried
out using a center lathe CA6140, powered by a 7.5kw electric motor giving a speed range of
10~1400 rev/min and a feed range of 0.014~3.16 mm/rev. The cutting tools applied were YG6
(WC +6%Co, K10 in ISO) uncoated tools and new tool was used for each experiment. A number of
angles for tool geometry were γo=14º, αo=αo'=6º, κr=75º, κr'=15º, λs=-6º. The workpiece used was
φ100×500 titanium alloy Ti-6Al-4V (TC4) as given in Table 1. The cutting experiments of YT15
cutting C45 steel were employed as the
comparison of machinability. Waterline
Workpiece
Cutting forces were obtained by 9257A Pipeline Tank
Kistler piezocrystal force sensor and 5007 charge
amplifier. Cutting temperature was measured by
thermoelectric method with X-Y function
recorder. Chip thickness was measured by using
a tool microscope. The machined surface Indicator lights
Buttons
roughness was taken by a TR200 roughness Pressure gauge PID controller
tester made by TIME Company, and the error is
0.001µm. Water steam generator
Cutting Experiments. The cutting forces Kistler force sensor
and temperature, deformation coefficient,
Fig. 1 Water vapor generator and experimental system
machined surface finish and chip appearance
investigated. The used cutting speed was 100m/min and the feed was 0.15mm/rev with the applied
depths of cutting were 1, 1.5, 2, 2.5 and 3mm; and the depth of cutting was 2mm with the feed were
0.1, 0.15, 0.2 and 0.3 mm/rev.
Cooling and Lubricating Conditions. All the
cutting experiments were completed at the Table1. Workpiece materials and characters
conditions of dry cutting, water-based emulsion Materials Ti-6Al-4V
and water vapor. The cooling distance was 20mm Chemical Al V O Fe C N
for the cutting fluid and water vapor. For the composition 6.1 4.1 0.15 0.06 0.01 0.01
water-based emulsion, the concentration was 5%, Mechanical σb [MPa] δ5 [%] ψ [%]
characters 980 14 40
the temperature was 19°C, the flux was 1L/min,
the pressure was 0.12MPa and the diameter of pipe was 5mm,. For the water team, the diameter of
nozzle was 2mm, the temperature was 125°C, the flux was 45L/min, and the pressure was 0.25MPa.
Results and Discussion
Cutting Forces. The main cutting forces of dry and wet cutting and water vapor application were
illustrated in Fig.2. and Fig.3. The results of radial cutting forces were presented in Fig.4. and Fig.5.
Among the machining characters of titanium alloys, a special one is that the main cutting force is
lower but the radial cutting force is higher than those in cutting of C45 steel.
1200 1400
C45 Dry C45 Dry
1000 Dry 1200 Dry
Wet 1000 Wet
800 WV WV
Fc (N)
800
Fc (N)
600
600
400
400
vc =100m/min
200 f =0.15mm/r 200 vc =100m/min
ap=2mm
0 0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0.0 0.1 0.2 0.3
ap (mm) f (mm/r)
Fig. 2 The Fc-ap curve in cutting experiments Fig. 3 The Fc- f curve in cutting experiments

3. Advanced Materials Research Vols. 139-141 683
Compared with dry and wet cutting, the main cutting force reduced about 30% and 15%, and the
radial cutting forces reduced about 35% and 20%, as water vapor cooling and lubricating. All the
emulsion and water vapor present the action of cooling and lubricating in cutting of Ti-6Al-4V. In the
experiments, water vapor produced the lowest cutting force. There are several reasons for the
favorable cooling and lubricating performance of water vapor [8]. The molecule or molecule group in
water vapor has a smaller radius than that in cutting fluids. And the velocity of water vapor jet flow is
much higher than that of cutting fluids. As a result, water vapor penetrates the tool-chip interface
easily and rapidly.
500
400 C45 Dry C45 Dry
350 Dry Dry
400
Wet Wet
300 WV
Fp (N)
WV 300
250
Fp (N)
200
200
150
100 100 vc =100m/min
vc =100m/min ap=2mm
50
f =0.15mm/r 0
0 0.0 0.1 0.2 0.3
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 f (mm/r)
ap (mm)
Fig. 4 The Fp -ap curve in cutting experiments Fig. 5 The Fp - f curve in cutting experiments
Cutting Temperature. The experiment results of cutting temperatures were shown in Fig.6. The
cutting temperature of titanium alloys is much higher
than that of C45 steel, which is another machining 900
character of titanium alloys. Water vapor application 800
decreased the cutting temperature about 15% and 10%, 700
compared to dry and wet cutting. Water vapor gives a 600
θ (°C)
better cooling action than the emulsion. In cutting, the 500
adhesive of titanium alloy chip on the tool face leads to 400 C45 Dry
an acutely friction and generates a great lot of heat. The 300 Dry
200 Wet ap=2mm
cutting heat centralizes in a small region because of the WV f =0.15mm/r
100
short tool–chip contact length [9]. After water vapor
0
enters into the tool-chip interface, lubricating film 120 130 140 150 160 170 180 190
forms immediately under the adsorption function. The vc(m/min)
Fig. 6 The θ-υc curve in cutting experiments
lubricating action of water vapor reduced the tool-chip
friction and the heat generation. In addition, water vapor has the capability of decalescence and heat
transformation, though the water vapor temperature is up to 100°C. Contrarily, emulsion is not easily
to penetrate the tool-chip interface and their cooling action only occurs at the outside of cutting zone.
Consequently, the water vapor cooling action is better than the emulsion in cutting of Ti-6Al-4V.
Cutting Deformation Coefficient. The deformation coefficient Λh can be calculated by Λh=hch/hD,
where the average chip thickness hch was measured by using the tool microscope, and the uncut chip
thickness hD =f·sinκr. In cutting, the deformation coefficients of titanium alloy are usually close to 1
and less than that of C45 steel. As shown in Fig.7, similarly, Λh decreased with rising feed under all
the lubricating conditions, and it is noted that the coolant and lubricant produced a tiny impact on
deformation coefficient. Accordingly, the force and heat from chip deformation were hardly
influenced. With the water vapor using, the decreases of cutting force and temperature resulted from
the decreases of friction force and heat generation on the tool-chip interface at s large extent. And this
also helps to slower the tool wear and prolong the tool life.
Machined Surface Finish. The surface finish roughness values were presented in Fig.8. As the
feed increasing, the value Ra increased. The application of water vapor gave the lowest surface finish
roughness value among the three cooling and lubricating conditions. These shown that the coolants
and lubricants can act not only on the rake face but also on the flank one. The high cutting temperature

4. 684 Manufacturing Engineering and Automation I
leads to rapid wearing of cutting tool and then impact to surface finish. The action of cooling and
lubricating reduce the cutting temperature and lower the tool wear speed. As a result, machined
surface finish can be easier controlled in the ideal range.
2.4
2.1 6
Dry
1.8 5 Wet
WV
1.5 4
Ra (µm)
Λh
1.2
3
0.9 C45 Dry
Dry 2
0.6 Wet vc =100m/min vc=100m/min
0.3 WV ap=2mm 1 ap=2mm
0.0 0
0.0 0.1 0.2 0.3 0.0 0.1 0.2 0.3
f (mm/r) f (mm/r)
Fig.7 The Λh – f curve in cutting experiments Fig. 8 The Ra-f curve in cutting experiments
Conclusions
Ti-6Al-4V is one of the difficult-to-cut materials, and the cutting experiments as water vapor cooling
and lubricating were carried out. Compared to dry cutting and emulsion applied, when water vapor
used, the main cutting force is lower about 30%-35% and 15%-20%, the cutting temperature reduces
bout 15%and 10%, while the deformation coefficient does not variety obviously. Water vapor
enhances the machined surface appearance to some extent. Water vapor application improves
Ti-6Al-4V machinability compared to dry and wet cutting. The excellent lubricating action of water
vapor in cutting could be summarized that water molecule has polarity, small diameter and high speed,
can be faster and easier to proceed adsorption in the cutting zone. The machining process of titanium
alloy receives available controlling. Otherwise, Water vapor has the advantages of cheap, clean for
environment, harmless for health and unneeded disposal or recycling, which are the potential for
green machining. Taking cooling and lubricating performance into account, water vapor may be a
better choice for green machining to titanium alloy.
Acknowledgements
This research reported in the paper is financially supported by National Natural Science Foundation of
China (NSFC) (50675053), Research and Development Plan of the Education Apartment of Liaoning
Province (05L301). These supports are greatly acknowledged.
References
[1] R.D. Han, Y. Zhang, Y.Wang: Key Engineering Materials, Vol.375-376 (2008), pp.172- 176.
[2] C.H. Zhang: Journal of Shenyang University of Technology, Vol.30 (2008) No.5, pp.525-529.
[3] S. Zhang:Journal of Shenyang University of Technology, Vol.30 (2008) No.4, pp.424-428.
[4] Y. Zhang, R.D. Han, T.L. Sun:Advanced Materials Research Vols. 97-101(2010), pp.2365-2368.
[5] C.H. Zhang: Journal of Shenyang University of Technology, Vol.30 (2008) No.6, pp.653-657.
[6] Y. Su, N. He, L. Li: China Mechanical Engineering (in Chinese), Vol.17(2006), pp.1183- 1187.
[7] P. Zheng: Journal of Shenyang University of Technology, Vol.31 (2009) No.5, pp.548-552
[8] J.A. Williams, D. Tabor: Wear, (1977) No.3, pp.275-292.
[9] V. A Godlevski, A.V Volkov: Lubrication Science, (1997) No.9, pp.127-140.
[10] M. Cotterell, G. Byrne:CIRP Annals - Manufacturing Technology, v57(2008), pp.93-96.

5. Manufacturing Engineering and Automation I
10.4028/www.scientific.net/AMR.139-141
Machining Process of Titanium Alloy Based on Green Cooling and Lubricating
Technology
10.4028/www.scientific.net/AMR.139-141.681
DOI References
[1] R.D. Han, Y. Zhang, Y.Wang: Key Engineering Materials, Vol.375-376 (2008), pp.172-
176.
doi:10.4028/www.scientific.net/KEM.375-376.172
[8] J.A. Williams, D. Tabor: Wear, (1977) No.3, pp.275-292.
doi:10.1016/0043-1648(77)90125-9
[9] V. A Godlevski, A.V Volkov: Lubrication Science, (1997) No.9, pp.127-140.
doi:10.1002/ls.3010090203