International Journal of Machine Tools & Manufacture 44 (2004) 439–456
www.elsevier.com/locate/ijmactool
A review of developments towards dry and high speed machining
of Inconel 718 alloy
D. Dudzinski a,∗, A. Devillez a, A. Moufki a, D. Larrouquère b, V. Zerrouki b, J. Vigneau b
a
Laboratoire de Physique et Mécanique des Matériaux, UMR CNRS 7554, ISGMP, Université de Metz, Ile du Saulcy, 57045 Metz Cedex 1,
France
b
SNECMA Moteurs, Route Nationale 7, BP 81, 91003 Evry Cedex, France
Received 21 March 2003; received in revised form 9 June 2003; accepted 10 June 2003
Abstract
The increasing attention to the environmental and health impacts of industry activities by governmental regulation and by the
growing awareness in society is forcing manufacturers to reduce the use of lubricants.
In the machining of aeronautical materials, classified as difficult-to-machine materials, the consumption of cooling lubricant
during the machining operations is very important. The associated costs of coolant acquisition, use, disposal and washing the
machined components are significant, up to four times the cost of consumable tooling used in the cutting operations. To reduce
the costs of production and to make the processes environmentally safe, the goal of the aeronautical manufacturers is to move
toward dry cutting by eliminating or minimising cutting fluids. This goal can be achieved by a clear understanding of the cutting
fluid function in machining operations, in particular in high speed cutting, and by the development and the use of new materials
for tools and coatings. High speed cutting is another important aspect of advanced manufacturing technology introduced to achieve
high productivity and to save machining cost. The combination of high speed cutting and dry cutting for difficult-to-cut aerospace
materials is the growing challenge to deal with the economic, environmental and health aspects of machining.
In this paper, attention is focussed on Inconel 718 and recent work and advances concerning machining of this material are
presented. In addition, some solutions to reduce the use of coolants are explored, and different coating techniques to enable a move
towards dry machining are examined.
 2003 Elsevier Ltd. All rights reserved.
Keywords: Inconel 718; High speed cutting; Dry cutting; Cemented tools; Ceramic tools; Coatings; Minimum lubrication application; Surface integrity
1. Introduction
The development of governmental pollution-preventing initiatives and increasing consumer focus on
environmentally conscious products has placed increased
pressure on industries to minimise their waste streams.
In this way, the ISO 14000 international environmental
management system standards have been developed to
help industries to manage better the impact of their
activities on the environment. Particularly concerned is
the metal-working sector which includes automotive and
aerospace industries. Attention is being directed to the
∗
Corresponding author.
E-mail address: dudzinski@lpmm.univmetz.fr (D. Dudzinski).
0890-6955/$ - see front matter  2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0890-6955(03)00159-7
role of cutting fluids in machining, machine tool energy
efficiency and the impact of process wastes on the
environment.
The ADEME, French Agency for Environment and
Energy Management, supports a project with the goal
of improving the machining processes of difficult-to-cut
materials for the aerospace industry, in order to move
towards dry cutting operations that are more friendly for
environment and health, and in the same way, to reduce
energy consumption.
The advantages of dry machining are:
앫 non-pollution of atmosphere or of water which
reduces the danger to health, in particular, skin and
respiratory damage,
앫 no residue of lubricant on machined components
440
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
which reduces or eliminates cleaning costs and associated energy consumption,
앫 no residue of lubricant on evacuated chips which
reduces disposal costs and the associated energy consumption.
At high cutting speeds, it is well known that the lubrication in the cutting zone is not evident and not really
effective. That is why high speed machining and dry
machining are often associated. High speed machining
leads to lower cutting forces, higher removal rates and
therefore to lower energy consumption. The project is
concerned with these two aspects of machining to realise
the ecological importance and high performance machining of hard-to-cut aerospace materials. In the first step,
the dry machining of the Inconel 718 alloy used by
Snecma-Moteurs will be studied.
Before introducing dry machining, it is important to
summarise the functions of cutting fluids and to search
how the effects of cutting fluids may be substituted. Generally, the use of cutting fluid leads to an increase of
tool life by the reduction of cutting forces (lubrication
effect) and temperatures in the tool (cooling effect).
However, these effects are not evident in high speed
machining, in particular, when ceramic inserts are
employed [1]. The energy consumed in performing a
machining operation is mainly converted into heat. Cutting fluids are employed to remove heat from the workpiece, the tool, the fixtures and the machine tool (cooling
effect). The heat generated is mainly dissipated in the
chip and in the workpiece, a rather small part of heat
flows to the tool. However, the highest temperature is
obtained at the tool–chip interface which leads to diffusion wear and cutting edge degradation. The other
important functions of the cutting fluids are to flush away
the chips from the cutting zone (flushing effect) and to
provide corrosive resistance to the machined component.
In addition, it is necessary to understand well the
mechanisms that contribute to tool wear and to workpiece surface integrity when working with Inconel 718.
Hence, this paper is a general review of the recent developments in the machining of this material and an exploration of the possible ways to dry cutting. In the first
part, the characteristics of Inconel 718 that are responsible for its poor machinability are reviewed and the
associated problems are listed. Then, the latest research
carried out on the use of uncoated and coated carbide
tools under wet and dry conditions is summarised. The
constant demand to increase productivity and quality has
led to the development of ceramic tools. They are used
for machining nickel-based alloys at higher cutting
speeds and some of their results are given. When surfaces are produced, they need to meet functional service
requirements, in particular for the aerospace components. As a consequence, attention is focussed on the
parameters influencing the surface quality during mach-
ining Inconel 718. Finally, to examine the move towards
dry cutting of Inconel 718, interesting alternatives to
conventional flooding coolant supply that are minimum
quantity lubrication technologies, are reported and recent
innovations of tool coatings for dry machining are discussed.
2. Machinability of Inconel 718
Nickel-based superalloys are widely employed in the
aerospace industry, in particular in the hot sections of
gas turbine engines, due to their high-temperature
strength and high corrosion resistance. They are known
to be among the most difficult-to-cut materials. Attention
is focussed on the Inconel 718 family in the following
paragraphs.
The properties responsible for the poor machinability
of the nickel-based superalloys, especially of Inconel
718, are [2–6]:
앫 a major part of their strength is maintained during
machining due to their high-temperature properties,
앫 they are very strain rate sensitive and readily work
harden, causing further tool wear,
앫 the highly abrasive carbide particles contained in the
microstructure cause abrasive wear,
앫 the poor thermal conductivity leads to high cutting
temperatures up to 1200 °C at the rake face [7],
앫 nickel-based superalloys have high chemical affinity
for many tool materials leading to diffusion wear,
앫 welding and adhesion of nickel alloys onto the cutting
tool frequently occur during machining causing severe notching as well as alteration of the tool rake face
due to the consequent pull-out of the tool materials,
앫 due to their high strength, the cutting forces attain
high values, excite the machine tool system and may
generate vibrations which compromise the surface
quality.
The difficulty of machining resolves itself into two
basic problems: short tool life and severe surface abuse
of machined workpiece [3,8]. The heat generation and
the plastic deformation induced during machining affect
the machined surface. The heat generated usually alters
the microstructure of the alloy and induces residual
stresses. Residual stresses are also produced by plastic
deformation without heat. Heat and deformation generate cracks and microstructural changes, as well as large
microhardness variations [9]. Residual stresses have
consequences on the mechanical behaviour, especially
on the fatigue life of the workpieces [10,11]. Residual
stresses are also responsible for the dimensional instability phenomenon of the parts which can lead to
important difficulties during assembly [12,13]. Extreme
care must be taken therefore to ensure the surface integ-
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
rity of the component during machining. Most of the
major parameters including the choice of tool and coating materials, tool geometry, machining method, cutting
speed, feed rate, depth of cut, lubrication, must be controlled in order to achieve adequate tool lives and surface
integrity of the machined surface [9,11].
3. Cutting tools for machining Inconel 718
The requirements for any cutting tool material used
for machining nickel-based alloys should include [3]:
앫
앫
앫
앫
앫
good wear resistance,
high hot hardness,
high strength and toughness,
good thermal shock properties,
adequate chemical stability at elevated temperature.
Turning, milling and drilling are common operations
carried out in the manufacture of jet engine mounts and
blades, while turning and drilling are the predominant
machining operations in the manufacture of disks for gas
turbines. Most published work on the machining of
nickel-based alloys deal with turning, then with milling,
while drilling has received little attention.
3.1. Machining Inconel 718 with carbide tools
Cemented carbide tools are still largely used for machining the nickel-based superalloys, especially Inconel
718. Over the years, the use of carbides for cutting tools
has been established. However, with the increasing
demand to achieve fast material removal and better surface quality, high speed machining was introduced and
the use of the cemented carbide tools has become more
problematic. For nickel-based alloys, the concept of high
speed machining refers to speeds over 50 m/min
approximately. In order to achieve higher cutting speeds,
coated cemented carbides have been developed. In the
following, the performance of coated and uncoated carbide tools in machining Inconel 718 is presented.
Liao and Shiue [14] analysed the wear mechanism of
two cemented carbide tools: K20 and P20 grades, in dry
turning of Inconel 718. The feed rate and the depth of
cut were 0.10 mm/rev and 1.5 mm, respectively. The
cutting speed was either 35 or 15 m/min.
On the wear surface of the K20 carbide, they observed
a sticking layer very close to the cutting edge. Built-upedge (BUE) was formed at a cutting speed of 35 m/min
with chipping of the cutting edge. When P20 carbide
was used, the sticking layer also could be found, but
comparatively, the wear was more irregular, the flank
wear length was larger and the groove was deeper.
Using the electron probe microanalyser (EPMA) to
analyse the concentrations of tool elements and work
441
elements beneath the rake face, they found for the cutting speed V = 35 m / min, that there were no change of
tool elements but Ni and Fe diffused into the cutting tool
for the two cemented carbide tools. This diffusion of the
work elements into the cutting tool may be explained by
the very high cutting temperature (about 1000 °C) during
the experiments.
Alaudin et al. [15] performed extensive research on
the end milling of Inconel 718. They carried out tests
under dry conditions with uncoated tungsten carbide
inserts (K20 grade). The tool life was investigated in the
full immersion and half immersion (both in up cut and
down cut). From the cutting tests, it was found that a
tool life range of 5–10 min can be obtained at cutting
speed of 19.32 m/min, feed of 0.09 mm/tooth and axial
depth of cut of 1.0 mm. In addition, they concluded that
full immersion increased tool life in comparison with
half immersion and down cut gave better performance
than the up cut end milling.
Derrien and Vigneau [16] tested uncoated and coated
carbide (K20 grade, CrN and TiN coatings) for milling
operations (contouring) at a high cutting speed of 200
m/min, a feed rate of 0.04 mm/tooth and a depth of cut
of 0.5 mm. They showed that TiN coated carbide has
the lowest wear. In addition, the machining performances with air assistance and micropulverisation were
compared with those of dry cutting. Dry cutting resulted
in the best tool performance.
Rahman et al. [4] presented a work which discusses
the machinability of Inconel 718 subjected to various
machining parameters including tool geometry, cutting
speed and feed rate. Flank wear of the inserts, workpiece
surface roughness and cutting force components have
been considered as the performance indicators for tool
life. Turning experiments were conducted under wet
conditions. Two types of inserts were used:
앫 K type substrate, TiN PVD coated cemented carbide, and
앫 multi Al2O3 CVD coated cemented carbide.
They studied the effect of the side cutting edge angle
(SCEA), Fig. 1, on the tool life for three feeds (0.2, 0.3
and 0.4 mm/rev) and three cutting speeds (30, 40 and
50 m/min), the depth of cut was fixed to 2 mm. For the
two inserts, tool life increases as the SCEA increases
from ⫺5 to 45°, see for example Fig. 2. For these
increasing values of the SCEA, the temperature of the
tool–chip interface related to the undeformed chip thickness t1 certainly decreases. Moreover, the heat generated
during the cutting process is distributed over a greater
length of the cutting edge lS. This improves heat removal
from the cutting edge, distributes the cutting forces over
a larger portion of the cutting edge, reduces tool notching and substantially improves tool life.
Throughout the experiments, the PVD–TiN coated
442
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
Fig. 1. SCEA or approach angle.t1 is the undeformed chip thickness,
f is the feed, w is the width of cut, lS is the length of the engaged
cutting edge.
Fig. 2. Effect of SCEA on tool life for a cutting speed of 30 m/min
and different feed rates using the Al2O3 CVD cemented coated tool.
From Rahman et al. [4].
carbide insert exhibited excellent resistance to depth of
cut notch wear at the approach angles of 15° and 45°.
The inserts performed satisfactorily even at the highest
speed of 50 m/min and at the highest feed rate of 0.4
mm/rev at 45° approach angle. This type of insert performed best at the speed of 30 m/min and the feed rate of
0.2 mm/rev with an approach angle of 45°.
The Al2O3 CVD coated cemented carbide exhibited
more severe notch wear at all three angles tested and
might not be suitable for cutting Inconel 718.
Itakura et al. [17] conducted dry turning experiments
to identify the tool wear mechanism clearly when a commonly used coated cemented carbide tool cuts Inconel
718. The tool was a square tip made of coated cemented
(P20, TiN/TiC multilayered coating). The temperature
was measured using the tool–workpiece thermocouple
method. With this method, only the average temperature
of the contact area can be measured. The cutting speeds
were 30, 100 and 150 m/min, the feed rate was 0.2
mm/rev and the depth of cut was 0.25 mm. Continuous
and interrupted experiments were conducted.
During continuous cutting at a speed of 30 m/min,
Inconel 718 adhered to the rake face of the major cutting
edge and the adhering material became a stable BUE
protecting the face. For this reason, there was almost no
rake wear but only flank wear. The hard particles contained in the Inconel 718 alloy were certainly responsible
for abrasive wear of the coating film on the flank face.
In addition, the work material adhered to the surface of
the worn area of the flank and tool material was repeatedly being removed. The cutting temperature at 30
m/min was 990 °K and at 100 m/min it was 1320 °K;
at this temperature, stable adhesion of the BUE is no
longer possible and wear advances on both rake and
flank faces. The coating film on the rake face wears off,
and later, when the wear reaches the cemented carbide
material, the rate of wear increases. In the same way,
the flank wear progresses faster at a cutting speed of
100 m/min. This is due to the high-temperature causing
diffusion and surface oxidation at high speeds.
During interrupted cutting, material adhering to the
rake face (BUE) is removed, causing the coating film to
flake. Wear advances as the number of repetitions
increases. It has been verified that gradually reducing the
undeformed chip thickness at the end of cutting will help
to reduce the separation of BUE and, as a result, will
reduce the separation of coating film from the rake face.
Jindal et al. [18] studied the relative merits of PVD–
TiN,TiCN and TiAlN coatings on cemented carbide substrate (WC—6 wt% Co alloy) in the turning of Inconel
718 with coolant. The tested cutting speeds were 46 and
76 m/min, the feed rate and the depth of cut were maintained constant and equal to 0.15 mm/rev and 1.5 mm,
respectively. At both speeds, TiAlN and TiCN coated
tools performed significantly better than tools with TiN
coatings. The end of life for all the three coated tools
was dictated by maximum flank wear or nose wear. At
the lower cutting speed of 46 m/min, an excellent performance of the TiAlN coated tools was noted, Fig. 3.
The maximum flank wear was about 0.15 mm after a
cutting time of 5 min. Furthermore, the TiAlN tools
exhibit lower nose and crater wear than the TiCN and
TiN coated tools.
Since the substrate material was the same for all the
coated tools, the observed differences in tool lives and
wear behaviour were attributed to the coatings. Coatings
increase wear resistance and may reduce cutting forces
and temperatures at the tool edge and thereby indirectly
affect the deformation and fracture behaviour of the tool.
TiAlN has a significantly higher hardness than TiCN or
TiN above 750 °C which will translate into improved
resistance to abrasive wear. Also, it exhibits good hightemperature chemical stability. This high-temperature
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
443
Fig. 4. Performance of TiAlN–monolayer and TiAlN–multilayer
coated carbide tools in turning Inconel 718, from Prengel et al. [19].
The two tested cutting conditions were: cutting speed = 61 m / min,
feed = 0.125 mm/ rev, depth of cut = 1.27 mm, cutting speed = 76.2
m / min, feed = 0.15 mm / rev, depth of cut = 1.52 mm.
Fig. 3. (a) Tool lives of PVD–TiN, TiCN and TiAlN coated inserts
in turning Inconel 718 (feed = 0.15 mm / rev, depth of cut = 1.5 mm,
cutting speed = 46 and 76 m / min); (b) maximum flank wear as a
function of time (cutting speed = 46 m /min), from Jindal et al. [18].
stability is a result of the tendency of TiAlN coating
to form a protective outermost layer of Al2O3 and an
intermediate layer comprising titanium, aluminium, oxygen and nitrogen during the machining operation, leading to higher oxidation resistance. Finally, TiAlN has
the lowest thermal conductivity among the three coatings
tested. This should result in lower tool tip temperatures
as much of the heat generated during machining would
be carried away by the chip. As a result, the TiAlN coating imparts excellent crater resistance.
Prengel et al. [19] confirmed the conclusion of the
previous work but with a multilayer coated tool. They
performed Inconel 718 turning tests with a coolant and
different PVD coated carbide cutting tools at 61 and 76
m/min, Fig. 4. The TiAlN-multilayer showed some
advantages
over
the
TiAlN-monolayer
and
TiN/TiCN/TiAlN-multilayer coating particularly at a
higher speed of 76 m/min. The main failure mode in
Inconel 718 machining was abrasive nose wear
accompanied by plastic deformation. Depth-of-cut
notching was also observed. The notching was heavily
influenced by burr formation on the uncut diameter.
Coated flaking was observed early in the cut at the depth
of cut region for all the coated tools tested.
Sharman et al. [2] detailed experimental work using
TiAlN and CrN coated tungsten carbide (K10 grade
carbide) end mills for dry machining up to 150 m/min
rectangular blocks of Inconel 718. A three factor, full
factorial cutting experiment design at two levels was outlined with the workpiece inclined at 45° and 60° from
the horizontal, Fig. 5. All the tests resulted in low tool
lives; however, the longest one occurred with TiAlN
coated tools at 90 m/min with a workpiece angle of 45°,
Fig. 6. One large notch located towards the high speed
position together with a smaller notch at the leading edge
position was generally evident.
Finally, TiAlN coated tools performed better than CrN
coated tools due to their higher hardness and oxidation
resistance. The extensive BUE and coating peeling seen
with CrN coated tools at a cutting of 90 m/min suggests
Fig. 5. Configuration of ball end milling tests performed by Sharman
et al. [2]. Axial and radial depths of cut: 0.5 and 1 mm, feed rate:
0.1 mm/tooth.
444
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
Fig. 6.
Dry ball end milling of Inconel 718 with coated carbide tools, results of the machining tests, from Sharman et al. [2].
that CrN has a higher chemical affinity to Inconel 718
than TiAlN.
The work of Jawaid et al. [5] is concentrated on the
wear behaviour of two different grades of single layer
PVD–TiN coated and uncoated tungsten carbide insert
when face milling Inconel 718 for various cutting conditions, Fig. 7. An emulsion with 6% concentration was
used as a coolant. The cutting speeds were 25, 50, 75
and 100 m/min for the coated tools and 25 and 50 m/min
for the uncoated tool. The depth of cut was 1 mm and
the feed rates were 0.08 and 0.14 mm per tooth.
The uncoated carbide (WC 90.1%, 9.5% Co, 0.4%
VC) tool performed better than the PVD–TiN layer
coated tools at the lowest cutting speed of 25 m/min and
for both feed rates in terms of tool life and of volume
of metal removed. Flank wear developed either on the
main cutting edge or on the nose, controlled the tool life
at all cutting conditions for all the three types of inserts.
Premature removal of the coating layers from the
tool–chip contact zone hindered the overall performance
of the PVD–TiN layer coated tools at a cutting speed of
25 m/min.
Ducros et al. [20] studied TiN/AlTiN and CrN/TiN
nanolayer coatings deposited on a K20 cemented carbide
and its machining performance was tested by turning
Inconel 718 alloy. Lubricated tests were carried out; cutting speed, feed and depth of cut were 40 m/min, 0.2
mm/rev and 1.5 mm, respectively. The performance of
the nanolayer coated tools was compared with that of
classical mono- and multilayer coated and uncoated
inserts, Table 1. Abrasive nose wear and chipping at the
cutting edge were the main failure modes observed. The
depth-of-cut notch is considered as a determinant for tool
life when machining Inconel 718. The notching is influenced by burr formation on the uncut diameter; this failure mode is mainly due to the hardening of the material
during machining. This phenomenon appeared for uncoated or CrN/TiN coated tool and was attenuated with
TiN/AlTiN nanolayer coated insert. According to the
authors, this was probably due to better chip sliding and
a reduced cutting temperature with this coating. Abrasive
wear is mainly due to carbide particles in Inconel 718.
The high hardness of the TiN/AlTiN nanolayer coating
(Hardness HV0.05 = 3900) provides better abrasion resistance than classical multilayer and monolayer structures.
In addition, TiN/AlTiN nanolayer coating presents a better resistance to welding. High-temperature resistance of
AlTiN included in this coating allows better resistance to
the BUE phenomenon than CrN/TiN nanolayer coating.
As summary, it appears from previous studies that
adhesion and abrasion are dominant when machining
Inconel 718. Work material adheres to the cutting edge
to form a BUE, depending on the cutting conditions. The
BUE is not always stable and is sometimes repeatedly
removed with tool material leading to important notching at the depth of cut and at the tool nose and coating
Fig. 7. Average flank wear when face milling Inconel 718, (a) at feed rate 0.08 mm per tooth, (b) at feed rate 0.14 mm per tooth. A and B were
two different grades of single layer PVD–TiN layer coated tools, C was an uncoated tungsten carbide insert (WC 90.1%, 9.5% Co, 0.4% VC).
From Jawaid et al. [5].
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
445
Table 1
Cutting tool failures of different coatings used for turning Inconel 718. Tool life was determined by an average flank wear of 0.5 mm, a depthof-cut notch width of 1 mm or a nose wear of 0.8 mm. Cutting conditions were: cutting speed V = 40 m / min; feed rate f = 0.2 mm / rev; depth
of cut d = 1.5 mm
Cutting tool and coating
Tool life
Depth-of-cut notching after Flank wear VB (µm) after BUE after 4 min
4 min machining (2 passes) 4 min machining (2 passes) machining (2 passes)
Uncoated
Commercial multilayer TIN/TiAlN (26
layers)
Multilayer CrN/TiN
Nanolayer CrN/TiN
Multilayer TiN/AlTiN
Nanolayer TiN/AlTiN
4 min
6 min
+++
+
500
300
+++
+
5
6
6
7
++
++
+
0
400
250
300
100
++
+
+
0
min
min 30 s
min
min 30 s
The wear was: +++ very important, ++ important, + beginning, 0 not significant. From Ducros et al. [20].
peeling. The hard particles contained in Inconel 718 produce severe flank wear. Flank wear and notching are the
main failure modes which limit the tool life. Due to the
high cutting temperatures, oxidation and diffusion also
occur [17].
The cutting speeds usually employed, under dry conditions, are in the range of 20–30 m/min and up to 50
m/min for coated tools, the feed rates are about 0.1–
0.2 mm/rev in turning. Some authors [2,16] tested with
success higher cutting speeds, up to 200 m/min with carbide tools.
The K20 grade (WC 93%, 7% Co) cemented carbide
seems to be the best for cutting Inconel 718. This is due
to its high hot hardness and high compressive strength;
in addition, its relative low cobalt content increases its
abrasion resistance. The high thermal conductivity and
low thermal expansion coefficient of the K20 grade also
improves performance by reducing the thermal shock
[8].
It has been shown also that the cutting geometry,
especially the SCEA, has a significant influence on the
tool life [4] and for interrupted cutting such as end milling, the down cut gives better results [15].
In comparison with the TiN and TiCN coatings, it has
been shown that the PVD (Ti,Al)N coating is most suitable in dry machining of difficult-to-cut materials such
as Inconel 718. Superior oxidation resistance, high-temperature chemical stability, high hot hardness and low
thermal conductivity are the principal reasons of its performance [18]. Recently, a TiN/AlTiN nanolayer coating
gave good results when machining Inconel 718 with low
BUE phenomenon and reduced abrasion wear [20].
3.2. Machining Inconel 718 with ceramic tools
The advantages of ceramic tools are [8]:
앫 high-temperature resistance enables them to be used
at high cutting speeds,
앫 abrasion and corrosion resistance,
앫 hot hardness and low chemical affinity resulting in
longer tool life in comparison with carbide tools.
However, the major disadvantages of ceramic tools
are their low resistance to mechanical shock or low fracture toughness and their low thermal conductivity. The
low toughness is the biggest problem when cutting
nickel-based alloys.
In the paper by Narutaki et al. [21], wear characteristics of three ceramics tools were examined:
앫 SiC whisker-reinforced alumina Al2O3 ceramic,
앫 silicon nitride Si3N4 ceramic, and
앫 TiC added alumina ceramic Al2O3–TiC
under high speed turning tests of Inconel 718 up to 500
m/min, in the presence of 10% water-based coolant and
the use of these ceramics tools was discussed. Another
interesting point of this work was the discussion on
tool geometry.
The SiC whisker ceramic showed the best performance in respect of notch wear VN at the side cutting edge
in the speed range of 100–300 m/min with a feed rate
of 0.19 mm/rev and a depth of cut of 0.5 mm, Fig. 8.
However, the notch wear VN and the flank wear VB with
the SiC whisker and the Si3N4 ceramics became very
large at higher speeds or higher feed rates. The Al2O3–
TiC ceramic showed very small flank wear VB under the
same testing cutting conditions but a maximal value for
VN around a cutting speed of 100 m/min. In addition,
the TiC added alumina ceramic tool showed very small
flank and notch wear at the cutting speed of 500 m/min.
Using a thermocouple method, the authors estimated
the rake and the flank temperatures during the tests. In
the cutting speed range of 400–500 m/min, the flank
temperature attained 1250–1300 °C, Fig. 9. The wear
of the SiC whisker and of the Si3N4 ceramics increases
drastically over the cutting temperature of 1300 °C (the
melting point of Inconel 718 is 1550 °C). In addition,
diffusion tests between the three chosen ceramics and
446
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
Fig. 8. Influence of cutting speed and of feed on notch wear VN and flank wear VB, when turning Inconel 718 with ceramic tools. From Narutaki
et al. [21].
Fig. 9. Cutting temperature when machining Inconel 718 with Si3N4
ceramic tool, from Narutaki et al. [21].
Inconel 718 were carried out. With the SiC whisker ceramic, the Ni diffused into the tool. With the Si3N4 ceramic, Si diffused into Inconel 718 and Cr in the alloy.
These tests showed that the Al2O3–TiC ceramic tool was
the most stable to Inconel 718. Therefore, the Al2O3–
TiC ceramic tool was the best cutting tool, as it has more
thermal wear resistance than the other tools in high speed
machining. The same conclusion was also obtained by
Kitagawa et al. [7].
The maximum notch wear observed for the Al2O3–
TiC ceramic tool around the cutting speed of 100 m/min
was a kind of transfer type wear generated by an
adhesion of work material to the tool, this mechanism
was temperature dependent. The flank wear is generally
considered as a kind of mechanical wear, such as an
abrasive wear. However, for the SiC whisker and the
Si3N4 ceramic tools flank abrasive wear was
accompanied by diffusion, which is a thermally activated process.
Kitagawa et al. [7] investigated tool wear and cutting
tool temperature by means of turning experiments up to
300 m/m, in the presence of 10% water-based coolant.
Performances of two types of ceramic, Si3N4 and Al2O3–
TiC, have been investigated. They confirmed that notch
wear VN (at the side cutting edge) and VN⬘ (at the end
cutting edge) were the major types of wear observed
when cutting Inconel 718. Flank wear VB remained
lower in the whole tested speed range, Fig. 10. They
postulated that temperature has an important role in tool
wear. They measured it in the rake face and in the flank
of the tool. All the temperatures rose monotonically, up
to about 1200 °C, with increasing cutting speed. However, taking into account the decreasing of notch wear
at higher cutting speed, they estimated that the wear
characteristics observed cannot be explained by temperature alone and that the wear is rather developed by an
abrasive process than a thermally activated adhesion
mechanism.
They observed also the chip morphology: with
increasing cutting speed, serrations in the chip became
obvious and the chip thickness decreased. In addition,
large plastic flow towards the side of the chip could be
depicted at a speed of 150 m/min. Plastic flow took place
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
Fig. 10. Dependence of flank wear VC = VB and notch wear VN and
VN⬘ on cutting speed at cut distance of 50 m with an Al2O3–TiC ceramic tool (depth of cut = 0.5 mm, feed rate = 0.19 mm / rev), from
Kitagawa et al. [7].
on the work surface and a burr was generated by the
side cutting with a maximum height at the same cutting
speed. They confirmed the superiority of the Al2O3–TiC
ceramic on the Si3N4 one over a cutting speed of 250
m/min.
To reduce the notch wear of the Al2O3–TiC at low
cutting speed, different tool geometry, Fig. 11, was
tested by Narutaki et al. [21] corresponding to increasing
value of the SCEA. A tool with a large cutting edge
radius (button type with nick) corresponding to a high
value of the SCEA showed better performance in terms
of tool wear.
The effect of tool geometry on cutting temperature
was also discussed by El-Wardany et al. [22] when turning hardened steel with an Al2O3–TiC ceramic cutting
tools. Different geometrical tool configurations (different
nose radii, angles of approach, widths of tool chamfer,
Fig. 11. Increasing the SCEA reduces the wear, from Narutaki et al.
[21].
447
and rake angles) were tested. In addition, they estimated
the cutting edge temperature during tests at cutting
speeds up to 500 m/min by measuring the rake face temperature with a thermocouple located very close to the
tool tip. The cutting edge temperature decreased with the
increasing tool nose radius. According to the authors,
this can be explained by the fact that for smaller nose
radius, the tool tip area available for heat conduction
decreases making the local temperature to rise.
Increasing the angle of approach (SCEA) reduced the
cutting edge temperature. Increasing the angle of
approach reduced the undeformed chip thickness t1 and
increases the width of cut w, see Fig. 1, leading to a
lower heat generation during cutting and, consequently,
the tool cutting edge temperature is reduced. In addition,
the authors showed that there exists an optimal negative
rake angle for which the temperature is minimum during cutting.
In the same paper, El-Wardany et al. [22] present
experimental results concerning turning Inconel 718
with an Al2O3–TiC ceramic cutting tool. An interesting
result emerged, initially with an increase of cutting speed
from 110 to 510 m/min, the cutting edge temperature
decreases, but with a further increase in the cutting speed
up to 720 m/min, the measured temperatures increase to
the range of 650–850 °C, Fig. 12. Although the rake
temperature was found to increase with the increase of
the cutting speed [21], the temperature at the tool tip
depends on the nature of the tool and workpiece
materials and on their thermal diffusivity. The thermal
diffusivity is a measure of transient heat flow and is
defined as the thermal conductivity divided by the product of specific heat times density. The thermal conductivity of the Inconel 718 increases linearly with temperature and its value at 1300 °C is 1.5 times higher than at
1000 °C. The variations with temperature of density and
Fig. 12. Turning Inconel 718 with an Al2O3–TiC ceramic cutting
tool, effect of cutting speed on tool edge temperature, from El-Wardany et al. [22].
448
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
specific heats for Inconel 718 are not thought to be
major; hence, the increase of thermal diffusivity with
temperature is due to thermal conductivity variations.
This high value of the workpiece’s thermal diffusivity
is accompanied by lower values of the tool’s thermal
diffusivity; therefore, the dissipation of heat at high cutting speed is higher through the workpiece than through
the tool and assures low values of tool tip temperature.
At the cutting speed of 720 m/min, the cutting edge
was covered with workpiece material caused by pressure
welding between the work and the tool. This pressure
welding appears when the rake temperature approaches
the melting temperature of Inconel 718. Therefore, the
thermal diffusivity of the tool is affected by the welded
layer. Hence, at 720 m/min, the tool tip temperature
attains a higher value, about 800 °C.
Elbestawi et al. [23] investigated the failure characteristics and the cutting performance of silicon carbide
(SiC) whisker-reinforced ceramic tools during milling of
Inconel 718. They performed cutting tests using round
and square inserts, at cutting speeds ranging from 200
to 700 m/min, and feeds from 0.05 to 0.15 mm/tooth.
Various immersion ratios were considered (from 0.25 to
1.00). They observed three main types of tool wear: flank
wear, depth of cut notch wear and trailing edge wear.
The depth of cut notch wear was the dominant failure
mode for tool at full immersion, and cutting speeds from
200 to 400 m/min, Fig. 13a. For higher cutting speeds
(400–700 m/min), lower immersion ratios and higher
feeds, trailing edge wear and/or flank wear were the
dominant modes, Fig. 13b. Round inserts improved the
cutting performance in comparison with square ones.
They provided a stronger cutting edge aiding notch wear
resistance. The optimum performance was obtained at
cutting speed of 700 m/min or higher, axial depths of
cut in the range from 1 to 2 mm, and feeds of 0.10 to
0.18 mm/tooth, increasing the immersion ratio improved
the tool life.
El-Wardany and Elbestawi [24] extended their end
milling experiments of Inconel 718 up to 2000 m/min
using flood coolant. Some tests were performed under
dry conditions, at cutting speeds of 1000 and 2000
m/min, and feed of 0.2 mm/tooth. As in the previous
work, they used round inserts of SiC whisker-reinforced
ceramic. The best combination of cutting conditions was
a speed of 1000 m/min, a feed of 0.2 mm/tooth and full
immersion (the depth of cut was 0.75 and 1.5 mm). For
these conditions, the mode of tool failure was flaking of
the rake face caused by the sticking of the workpiece on
it. The tool life in terms of volume of material removal
was three times that removed by cutting speeds higher
or lower that this optimal speed and a surface finish of
0.7 µm was produced. The cutting process was more
stable during dry cutting tests at high speeds; only crater
wear was developed on the tool accompanied by a small
Fig. 13. (a) End milling Inconel 718 with a SiC whisker-reinforced
ceramic tool. Modes of Failure at 1.25 mm depth of cut and full immersion. (b) End milling Inconel 718 with a SiC whisker-reinforced ceramic tool. Modes of Failure at 1.25 mm depth of cut and 0.5 and 0.25
immersion, from Elbestawi et al. [23].
amount of plastic deformation on the tool rake face, and
the surface finish was about 0.5 µm.
Gatto and Iuliano [25] coated 20% SiC whiskerreinforced Al2O3 tools with CrN and TiAlN using PVD
in order to minimise the temperature effect and to obtain
an increase in tool life. They performed machining tests
on a vertical boring mill under dry conditions. The cutting speeds were 300, 400 and 530 m/min, the feed rates
were 0.08, 0.12 and 0.22 mm/rev and the depth of cut
was 1.5 mm for all the tests. Flank wear VB and notch
wear VN were measured and statistical models were proposed. The coatings protected the ceramic tool as a thermal barrier and they increased the ceramic tool life.
Maximum productivity was obtained with the TiAlN
coated ceramic, Fig. 14.
Li et al. [6] used Sialon (Si3N4–Al2O3) ceramic tools
for turning tests of Inconel 718. Sialon ceramic tools are
prone to notch wear, with minimum damage to the tool
nose at lower speeds (120 m/min). A transition is
observed at 240 m/min. Further increasing the speed to
300 m/min leads to a reduction in notching and an
increase in nose and flank wear.
Tool life of ceramic tools is severely limited by
excessive notching in the depth of cut region, caused by
welding and pull-out, which may be due to the relatively
low mechanical toughness of ceramic tools. In addition,
ceramics are poor heat conductors which make them vul-
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
Fig. 14. Dry machining Inconel 718 with coated ceramic tools.
Maximum productivity values Q, the values refer to a machined volume of 40 cm3, from Gatto and Iuliano, [25]. Q = Vfd, where V is the
cutting speed, f the feed and d the depth of cut.
nerable to thermal cracks. However, ceramic tools have
large usage possibilities. They can withstand higher cutting speeds (above 200 m/min) than uncoated and coated
carbide tools. Dry conditions are generally recommended during machining with ceramic tools. Coatings may be used to improve the cutting performance of
ceramic tools.
3.3. Assisted machining for Inconel 718
One approach to enhance the machining performance
(in terms of material removal rate, tool life and surface
finish) in hard-to-cut materials is hot machining. Localised heat sources such as laser and plasma [26,27] were
used to assist the machining of such materials. At high
temperatures above 750 °C, Inconel 718 exhibits significantly reduced yield stress, Fig. 15; therefore, localised heating may soften the material and reduce the shear
strength and strain hardening associated with chip formation. During plasma enhanced machining (PEM),
Leshock et al. [27] showed that the cutting forces
decrease with increasing the surface temperature, Fig.
Fig. 15. Yield stress of Inconel 718 vs. temperature from Leshock et
al. [27].
449
Fig. 16. Resultant cutting force vs. surface temperature for various
cutting speeds (feed = 0.124 mm / rev), during PEM of Inconel 718
with ceramic inserts (aluminium oxide reinforced with silicon carbide
whiskers) from Leshock et al. [27].
16, and the surface roughness is also improved. However, beyond 530 °C, surface oxidation was observed;
this problem should be resolved by a more accurate control of the plasma arc. With PEM, the notching is eliminated and the tool life is increased, but the chip temperature is a little higher than in conventional machining,
leading to higher flank wear rates [27].
An alternative solution to enhancing the machining
performance of hard-to-cut materials is to reduce the cutting temperatures by the application of a high pressure
waterjet coolant [28]. Another possibility is to use liquid
nitrogen as coolant [29,30]. To minimise waste, cryogenic fluid is applied directly to the cutting edge where
the material is cut and heat is generated. The flow rate
of the cryogenic fluid is proportional to the heat generated in the cutting process, preventing the workpiece
from becoming distorted due to extreme heating or cooling, Fig. 17. The cooling effect obtained with this
Fig. 17. Assisted machining of Inconel 718. Application of liquid
nitrogen to the cutting zone. From Hong et al. [30].
450
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
method is stronger than with waterjet cooling and the
temperature dependent wear reduced significantly in the
tests of machining titanium and Inconel 718 alloys.
However, nitrogen is expensive and does not recycle.
Kim et al. [31] proposed a cooling system which uses
compressed air. The drier air exchanges heat in an aircooler system and its temperature decreases down to
about ⫺2 °C. The compressed chilly air is jetted through
the nozzle enabling adiabatic expansion and leading to
a temperature in the jet of about ⫺12 °C. This cooling
technique was tested in ball end milling at cutting speeds
of 90 and 210 m/min, feed rate of 0.1 mm/tooth, depth
of cut of 0.5 mm with coated TiAlN carbide tool. The
tool life was significantly improved at 90 m/min; however, at a speed of 210 m/min, the compressed air failed
to infiltrate into the tool–chip interface or tool–workpiece and the advantage of the proposed cooling system
was reduced.
4. Surface integrity when machining Inconel 718
For safety critical industries such as aerospace, surface
integrity is important for the components submitted to
high thermal and mechanical loads during their use,
Axinte and Dewes, [32]. Structures in aerospace applications are subjected to severe conditions of stress, temperature and hostile environments. Section size is continually reduced in order to minimise weight so that
surface condition has an ever-increasing influence on
its performances.
Service histories and failure analyses of dynamic
components show that fatigue failures almost always
nucleate on or near the surface of a component. By considering stress corrosion resistance, it is again recognised
that the surface of a component is a primary factor in
determining susceptibility to attack and subsequent failure. Hence, much attention should be paid to surface
characteristics of components [33].
Overheating/burning, surface irregularities, BUEs or
deposits of debris, macro- and microcracks, cavities,
microdefects such as laps and inclusions, metallurgical
alterations including microstructural distortion, phase
transformations, heat affected layers, tensile residual
stresses are the main problems identified. Such changes
occur due to thermal and mechanical loads during machining. Residual stresses are an effect from both heat generated and mechanical work going into the surface and
subsurface. Thermal effects tend to give tensile stresses,
while mechanical influences contribute to compressive
residual stresses, [32]. Jacobson et al. [34] have noted
that when increasing cutting speed during hard turning
of bainitic steels, one also increases the strain rate in the
process which gives more mechanical work leading to
compressive stress. In the same way, increasing the
strain rate in the cutting zone introduces more generated
heat, which has a tendency to produce tensile stress at
the machined surface.
Residual stress strongly affects the fatigue life of a
component. A tensile mean stress reduces the allowed
alternating stress in service. Conversely, the introduction
of a compressive mean stress will increase the allowed
alternating stress for a given fatigue life. High tensile
stresses generated by the machining of work hardening
alloys can be highly deleterious to fatigue performance.
The effect is most significant in the high cycle fatigue
regime where the applied stress magnitude is not sufficient to significantly relax the residual stresses produced during manufacturing. Brinksmeier et al. [35] give
a good overview of the subject of residual stresses, their
measurement and causes in machining processes.
Field and Khales [33] proposed a minimum surface
integrity data set, which involves surface finish
(roughness and waviness), macro- and microstructure
and hardness of the surface, microhardness variations,
structural changes in the machined surface layer. They
added residual stresses and a minimal fatigue testing to
give a ‘standard’ data set. In the following, we present
some results about surface finish during machining
Inconel 718 and the main parameters which affect the
surface integrity are identified.
Ezugwu and Tang [9] carried out turning tests on
Inconel 718 alloy using round- and rhomboid-shaped
pure oxide (Al2O3 + ZrO2) and mixed oxide (Al2O3 +
TiC) ceramic tools. Coolant was not used because of the
low thermal shock properties of ceramics. Inconel 718
alloy was machined at a speed of 152 m/min, a feed rate
of 0.125 mm/min and a constant depth of cut of 2.0 mm.
They have shown that the geometry of cutting tools
plays an important role in determining the nature of
machined surfaces. The round inserts produced better
surface finish than the rhomboid inserts. All the rhomboid-shaped ceramic tools failed after machining for 1
min due to severe notching at the depth of cut. Under
the chosen conditions, long continuous chips were produced due to the ductility of the work material. The hardness of the workpiece surface layer increased with prolonged machining due to plastic deformation and to the
high rate of work hardening of Inconel 718. Plastic
deformation was evident by the observation of the elongation of grains and orientation under the machined surface. Tearing of the surface layer of the Inconel 718 was
observed in all machining trials. Tearing on the
machined surface of a component reduces its fatigue
strength.
Bresseler et al. [36] and Kishawy and Elbestawi [37]
studied the phenomenon of material side flow which represents an important aspect of machined surfaces. They
conducted experiments in order to study the effect of
cutting edge preparation, nose radius, feed and tool wear
on surface material side flow quality during dry hard
boring and hard turning. The work material was not the
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
Inconel 718 alloy but a hardened steel. However, their
work is important to identify the generally parameters
influencing surface quality. They verified that cutting
edge preparation has a significant effect upon the
material side flow, especially during finishing operations. Although cutting with a small feed improves surface finish, it leads to more material side flow on the
machined surface, hence to a deterioration in surface
quality. In addition, an increase in the tool nose radius
leads to the ploughing of a large part of the chip and in
consequence to severe material side flow on the
machined surface.
Near surface residual stress distributions in Inconel
718 arising from a turning operation were studied by
Schlauer et al. [38]. The cutting conditions were very
similar to orthogonal cutting. The cutting tool used was
a SiC whisker-reinforced alumina Al2O3 ceramic. The
tool geometry was kept constant. Cutting speeds were
10, 410 and 810 m/min and for the feed were 0.01, 0.06
and 0.11 mm/rev. For the cutting speed of 10 m/min, low
residual stresses were found. At higher cutting speeds of
410 and 810 m/min, a thin layer exhibiting tensile
residual stresses was formed near the machined surface,
with a maximum tensile stress at the surface, Fig. 18.
Within 10 µm from the machined surface, the tensile
stress dropped to 0. It was followed by a layer with compressive stresses that is several times thicker than the
tensile layer. When the cutting speed was increased, the
tensile and the compressive stresses increased and the
depth of the layer affected by machining increased too.
Similar stress profiles were found by Derrien and Vigneau [16] and Guerville and Vigneau [11]. They carried
out high speed and dry milling tests (contouring and
point milling) with uncoated cemented carbide K20
mills. For contouring operations at V = 200 m / min (f
= 0.04 mm / tooth and depth of cut = 0.5 mm), residual
stresses are tensile, affecting a layer of 400 µm with an
extreme value of 1500 MPa. This maximum value was
three times the one obtained using a conventional speed
Fig. 18. Turning Inconel 718 with a SiC whisker-reinforced alumina
ceramic tool. Residual stress depth profiles for the feed 0.06 mm/rev
and the three tested cutting speeds (10, 410, 810 m/min). From
Schlauer et al. [38].
451
Fig. 19. Contouring Inconel 718 with a carbide K20 tool: comparison
of residual stresses profiles after high speed machining (200 m/min,
dry conditions) and conventional machining (16 m/min, emulsion 5%),
from Derrien and Vigneau [16], Guerville and Vigneau [11].
of 16 m/min and wet conditions, Fig. 19. On the other
hand, for the point milling tests, the level of the residual
stresses was lower with a maximum tensile stress value
of about 750 MPa near the machined surface, a
maximum compressive stress value of 500 MPa and a
100 µm affected layer, Fig. 20.
Comparable residual stress profiles were also obtained
after ball end milling by Ng et al. [39]. The tests were
performed at a cutting speed of 90 m/min, feed of 0.2
mm/tooth and an axial depth of cut of 0.5 mm in down
milling, the workpiece surface was inclined with an
angle of 45° from the horizontal. High tensile stress
Fig. 20. Point milling Inconel 718 with carbide K20: comparison of
residual stresses profiles after high speed machining (200 m/min, dry
conditions) and conventional machining (18 m/min, dry conditions),
from Derrien and Vigneau [16], Guerville and Vigneau [11].
452
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
values were measured parallel to the feed direction near
the machined surface, followed by highly compressive
stress at a shallow depth and the compressive layer was
maintained to 150 µm.
Gas turbine components are complex in their shape.
They are thin walled and call for very close dimensional
tolerances and good surface integrity. The Inconel 718
used for jet engine component is not only known to be
difficult to cut but also to reveal dimensional instability
after machining [12,13]. Dimensional instability is a
change of dimension with respect to time without any
further work being done on the component. Dimensional
instability of components induces problems during
assembly. The two probable causes of this phenomenon
are the residual stresses and microstructure changes
introduced by the machining process. Subhas et al.
[12,13] compared the dimensional instability of Inconel
718 with that of Ti–6Al–4V and mild steel. The specimens were machined at identical cutting conditions and
the dimensional changes were measured with respect to
time up to 220 h after machining. Inconel 718 is more
prone to dimensional instability than either titanium
alloy or mild steel, dimensional changes being lowest
for the latter material. It can be noted that this phenomenon is not observed in other nickel-based alloys. Microscopic observations showed that shear localised chips
were formed with the Inconel 718 alloy at various cutting speeds. These chips are very similar to those
obtained with the Ti–6Al–4V alloy, see also the study
of Komanduri and Shroeder [40]. According to Subhas
et al. [12,13], the dimensional instability of Inconel 718
may be attributed to the presence of g⬙ phase. They also
studied the influence of cutting conditions on the plastic
deformation mechanism and then on residual stresses. In
particular, they observed that negative rake angles
increase the residual stresses. They finally proposed a
process parameter optimisation technique to control the
dimensional changes within acceptable limits.
5. The way to dry machining
The use of coolants, in addition to being undesirable
to the environment and for the human health, entails high
costs in production and disposal. Depending on the
machined workpiece, cost savings up to 17% of the total
workpiece cost can be made by introducing dry machining. This is mainly due to the elimination of coolant supply, cleaning, maintenance and disposal costs [41,42].
Reducing costs in the cutting process together with
reduced environmental pollution by the use of dry machining is the main key for the industry to remain competitive and profitable in the future [42]. Today, wet cutting
is still largely used in manufacturing industry, but
research and development is being undertaken to minimise the use of coolant lubricants and new concepts of
minimum quantity cutting fluid application have been
developed, [42–47]. In the following, the concept of
minimum fluid application is developed and then the
results of some dry cutting experiments using hard coatings are presented.
5.1. Minimal quantity of cutting fluid application
The characteristic of the ‘minimal quantity’ application is to substitute all the effects of the coolant lubricant by using jet application to produce effects of equal
values. Only a small amount of lubricant is needed if it
is efficiently applied to the cutting zone. This lubricant
is completely used and results in almost dry chips. However, all the effects provided by the usual cutting fluid
flood-type lubricant are not possible with minimal quantity application or dry cutting alone. For example, the
flushing effect is not supplied and the cooling effect is
partially or not at all (with dry cutting) obtained. Then,
additional use of minimum cooling system of the workpiece and a specially adapted blow-out technology for
chip removal are required. Nevertheless, the results
obtained with minimum quantities of cutting fluid application in drilling are excellent compared to the usual
flood-type application, [45]. The ‘minimal quantity’
lubrication is a suitable alternative for economically and
environmentally compatible production. It combines the
functionality of cooling lubrication with an extremely
low consumption of lubricant and therefore it has the
potential to close the gap between overflow lubrication
and dry cutting [43].
Machado and Wallbank [44] conducted experiments
on turning medium carbon steel (AISI1040) using a Venturi to mix compressed air (the air pressure was of 2.3
bar) with small quantities of a liquid lubricant, water or
soluble oil (the mean flow rate was between 3 and 5
ml/min). The mixture was directed onto the rake face
of a carbide tool against the chip flow direction. The
application of a mixture of air + soluble oil was able to
reduce the consumption of cutting fluid, but it promoted
a mist in the environment with problems of odours, bacteria and fungi growth of the overhead flooding system.
For this reason, the mixture of air + water was preferred.
However, even if the obtained results were encouraging,
the system needed yet some development to achieve the
required effects in terms of cutting forces, temperatures,
tool life and surface finish.
In contrast, Varadarajan et al. [46] developed an alternative test equipment for injecting the fluid and used it
with success in hard turning for which a large supply of
cutting fluid is the normal practice. The test equipment
consisted of a fuel pump generally used for diesel fuel
injection in truck engines coupled to a variable electric
drive. A high speed electrical mixing chamber facilitated
thorough emulsification. The test equipment permitted
the independent variation of the injection pressure, the
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
frequency of injection and the rate of injection. The
investigations performed by the authors revealed that a
coolant-rich (60%) lubricant fluid with minimal additives was the ideal formulation. During hard turning of
an AISI 4340 hardened steel of 46HRC (460 HV), the
optimum levels for the fluid delivery parameters were:
a rate of 2 ml/min, a pressure of 20 MPa and a high
pulsing rate of 600 pulses/min. In comparison, for the
same cutting conditions, with dry cutting and wet cutting, the minimum quantity of cutting fluid method has
led to lower cutting forces, temperatures, better surface
finish, longer tool life. In addition, it was observed that
tightly coiled chips were formed during wet turning and
during minimal application, while long snarled chips
were prevalent during dry turning. It must be noted that
during minimal application, the rate of fluid was only
0.05% of that used during wet turning. The major part
of the fluid used during minimal quantity application was
evaporated, the remnant was carried out by work and
chips and was too low in volume to cause contamination
of the environment.
The paper of Klocke and Eisenblätter [47] deals with
drilling tests using minimum cooling lubrication systems
which are based on atomising the lubricant directly to
the cutting zone. Small quantities of lubricant, in order
of 10–50 ml/h, were mixed with compressed air for an
external feeding via a nozzle or for internal feeding via
spindle and tool. Internal feed systems with their ability
to deliver the mixture very close to the drill–workpiece
contact point may achieve very good results in terms of
surface finish and tool life.
Lahres et al. [42] presented dry machining of
synchronising cones for automotive application. The
work material was austenitic 22Mn6 steel. In the first
step of their study, dry machining was compared to
machining with coolant and with minimal lubricant system. The used minimal lubricant system worked with a
special oil which had food-grade quality. The air volume
flow was about 50 l/min and the air volume oil was about
20 ml/h; hence, the produced chips were dry after leaving the contact zone of the cutting process. At this oil
volume flow, a single chip can carry a maximum of 1
nl. Therefore, the chips could be declared as being
almost dry and passed for metallic recycling without
further treatment. The results exhibited an advantage for
the minimal lubricant technique and for the dry machining.
In the second step, they investigated new tool coatings
with a potential for dry machining:
TiAlNOx,
TiAlN + MoS2,
single layer (Ti,Al)N,
multilayer TiN + TiAlN.
A new series of experiments were performed under
453
minimal lubrication. The best performance was obtained
with the double layer TiAlN + MoS2 coating. Metallographical studies indicated that the solid lubricant MoS2
is worn after a few machined parts. However, a small
amount of solid lubricant exists further in the valleys of
the tool surface profile and initiates a low friction at the
tool–chip interface. Nevertheless, a small amount of
solid lubricant exists perhaps also on the machined surface; this pollution is a problem for the aerospace
components.
The TiAlNOx consists of two layers: the first layer
on top of the substrate surface is a thick TiAlN-coating
necessary to achieve good adhesion, the second is a thin
Al2O3-coating used to reduce oxidation and wear. The
performance of this coating was almost as good as the
one of TiAlN + MoS2 - coating.
5.2. Dry cutting
Elimination of coolants also involves the absence of
their positive effects on the metal cutting processes. For
dry cutting operations, sufficient heat removal and the
avoidance of heat build-up above a critical temperature
must be guaranteed. The removal of chips from the cutting zone is another important aspect. The process must
preserve the surface integrity of workpiece and produce
stable tool wear suitable for automatic manufacturing
systems. Tools with high hot hardness, high refractivity
and low coefficients of friction are required and the use
of tools with low-adhesion coatings can help greatly.
Tool coatings play a major part in tool development, in
particular for dry machining, Schulz et al. [48]. The tool
coatings can at least partially substitute the eliminated
functions of the cutting fluids.
Tönshoff and Mohfeld [49] and Tönshoff et al. [50]
presented an interesting paper on (Ti1⫺x, Alx)N coatings
for wear protection in dry drilling operations of tempered
steel. Due to the complex thermal and mechanical loads
in drilling, cutting materials for dry drilling require high
hot hardness and high toughness.
Coatings separate tools from the workpiece material
in cutting and offer a possibility of replacing coolants.
Demands placed on coatings for dry machining include
reduction of friction to decrease dissipated thermal
energy in tool–workpiece contact and protection of heat
and diffusion to guarantee high wear resistance at high
temperatures. Because of the poor conditions for heat
conduction from the drill, only thermally stable coating
layers are applied. (Ti,Al)N possesses the lowest coefficient of thermal conduction and a considerably
increased oxidation stability compared with other hard
coatings, particularly with TiN coating. Whereas TiN
oxidises at temperatures higher than 600 °C, (Ti,Al)N
has a high oxidation resistance up to 800 °C. The formation of a dense Al2O3 top layer increases diffusion and
oxidation resistance of the (Ti,Al)N film. Compared to
454
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
TiN, (Ti,Al)N has a high hardness even at elevated temperatures. For dry drilling operations, the ternary
(Ti,Al)N system has remarkable advantages; compared
to uncoated carbide and TiN coated tools, it has a
superior wear behaviour. The best wear behaviour in dry
drilling of tempered steel was obtained for an Al/Ti ratio
equal to 1.
A further improvement in dry machining was achieved by adding oxygen to a (Ti,Al)N coating to form
TiAlON [51]. Though the microhardness of TiAlON was
lower than (Ti,Al)N, TiAlON offered a higher abrasion
resistance during dry drilling due to the formation of
Al2O3. Alumina provides oxidation resistance and is
thermally stable. In addition, a graded multilayer structure of TiAlON with Al2O3 was developed by providing
a stable oxide layer on layer on top of the nitride coating,
Bouzakis et al. [52].
Schulz et al. [48] showed the performance of oxide
Al2O3 and ZrO2 PVD-coatings in dry cutting operations
of high strength graphic cast iron. Commercial titaniumbased hard coatings like TiN, TiCN and TiAlN with high
hardness even at high temperatures provide a high wear
resistance. Oxide PVD-coatings specially developed for
dry machining additionally combine a reduction of friction at elevated temperatures with high wear resistance.
The changed contact conditions will decrease the heat
generation. Then, the tendency for the work material to
adhere on the rake face is reduced and the chip flow is
improved. The substrate of the drilling tool was a fine
grain tungsten carbide with 10% of cobalt (K20–40).
The advantage is a much better toughness and a reduced
risk of cutting edge chipping. Different oxide PVD-coatings were tested: TiAlN–Al2O3, TiAlN–ZrO2, TiZrN–
ZrO2 and compared with the uncoated and the simple
TiAlN coated tool performances. Due to the high hardness, increased resistance and a low friction coefficient
even at elevated temperatures, the oxide-coated tools
show notable advantages for dry drilling in high strength
materials. With the different oxide coatings, the tool life
was remarkably improved. The TiAlN–ZrO2 coating had
the best performance. A significant reduction of the cutting edge temperature by using the oxide coating was
also observed.
Hard coatings such as TiAlN may increase tool performance and tool life by arresting or slowing down certain types of wear. However, these coatings retain a high
coefficient of friction and require a lubricant. For dry
cutting applications, a solid lubricant such as
MoS2/titanium composite coatings may be used to
reduce the friction coefficient and then to decrease the
cutting forces and temperatures which reduces the local
welding and, in consequence, improves surface finish.
The MoS2/titanium composite coatings have a much
lower wear rate than the traditional hard coatings. They
have also a very low friction (0.02–0.1) which allows
them to be used at high speeds. Beside the commercially
obtainable MoS2 coatings, other low-friction coatings
such as tungsten carbide/carbon (WC/C) coatings are
available. This type of hard/lubricant coating was proposed for dry machining, [53–56].
A new highly improved AlTiN film has been
developed and proposed by Arndt and Kacsich [57] for
dry or minimum quantity lubrication and high speed
machining of stainless steel as well as hardened steel up
to 63 HRC. The improvement of the deposition operation has led, to the new coating, to possess better
characteristic properties such as high hardness associated
to an ultra-fine crystallinity. The cutting performances
of the new coating were compared with success to other
commercial (Ti,Al)N films.
Recent hard coatings are the superlattice structured
PVD hard coatings presented by Hovsepian and Münz
[58]. They are dedicated to high-temperature performance and for tribological applications. Abrasion resistant
TiAlN was combined with VN to achieve a wear resistant low friction coefficient coated tool tested with success during dry machining of steels. In the same way,
the hard coating TiAlCrYN was overcoated with
lubricious and non-sticking coating C/Cr and tested on
end mills for the machining of extremely abrasive high
Co containing Ni-based alloys. However, no published
results from these tests have yet been found.
6. Conclusions
Inconel 718 is a high strength thermal resistant
material alloy. It is a highly strain rate sensitive material
which work hardens readily, and contains hard particles
making it a very difficult-to-cut material. The difficulty
of machining Inconel 718 resolves into short tool life
and poor surface integrity. The main wear mechanism is
abrasion observed for all the tested tools. Welding and
adhesion on the cutting tool frequently occur to form a
BUE. The BUE is repeatedly removed leading to severe
notching. Machining induces plastic deformation and
heat generation, the consequences are metallurgical
transformations and residual stresses in the machined
surface layer. The residual stress distribution exhibits a
maximum tensile stress near the machined surface and
then a compressive stress. The depth of affected layer
and the tensile and compressive stresses increase when
the cutting speed increases.
Cemented carbide tools are largely used for machining
nickel-based alloys at very low cutting speeds of 20–30
m/min, the K20 grade appears to be the best for cutting
Inconel 718. Higher cutting speeds, certainly up to 100
m/min, under dry conditions may be achieved with
coated carbide tools. The PVD (Ti,Al)N coating seems
to be most suitable. It displays high oxidation resistance,
high-temperature chemical stability, high hot hardness
and low thermal conduction. The nanolayer structures
with higher hardness appear to give encouraging results.
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
Much higher cutting speeds (from 200 to 700 m/min)
are attained with ceramic tools. The Al2O3–TiC is the
chemical most stable to Inconel 718; it has most thermal
resistance in high speed machining. Round inserts of SiC
whisker-reinforced ceramic improve the cutting performance for milling of Inconel 718, in comparison with
the square ones. Ceramics are poor conductors and vulnerable to thermal cracks and dry machining is recommended with them.
The use of coolants is undesirable for environment
and human health; furthermore, it induces high
additional costs. New concepts have been introduced to
minimise coolant lubrication and in the same way new
coatings with a potential for dry machining have been
developed.
In dry machining, the positive effects of coolants have
to be obtained by another way. For the removal of chips
from cutting zone, heat evacuation must be guaranteed.
The process must preserve an acceptable surface integrity. Tools with high hot hardness, high refractivity, low
adhesion and low friction properties are required. Oxide
PVD-coatings combine a reduction of friction at elevated
temperature with high wear resistance, they show excellent performance during drilling high strength materials.
Solid lubricants such as MoS2/titanium composite coatings or WC/C coatings should give useful results when
machining Inconel 718 under dry conditions.
Experiments and machining simulation now have to
work together to find a way to the dry cutting of Inconel
718. The objective is to find the suitable tool and appropriate coating, to define the better geometrical tool configuration and the optimal cutting conditions in order to
obtain more acceptable surface integrity and the longer
tool life.
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
Acknowledgements
[17]
The research work published in this paper was carried
out with the financial aid of ADEME, French Agency for
Environment and Energy Management. It corresponds to
the first stage of the study concerning high speed and
dry cutting of Inconel 718.
References
[1] J.M. Vieira, A.R. Machado, E.O. Ezugwu, Performance of cutting
fluids during face milling of steels, Journal of Materials Processing Technology 16 (2001) 244–251.
[2] A. Sharman, R.C. Dewes, D.K. Aspinwall, Tool life when high
speed ball nose end milling Inconel 718, Journal of Materials
Processing Technology 118 (2001) 29–35.
[3] E.O. Ezugwu, Z.M. Wang, A.R. Machado, The machinability of
nickel-based alloys: a review, Journal of Materials Processing
Technology 86 (1999) 1–16.
[4] M. Rahman, W.K.H. Seah, T.T. Teo, The machinability of
[18]
[19]
[20]
[21]
[22]
455
Inconel 718, Journal of Materials Processing Technology 63
(1997) 199–204.
A. Jawaid, S. Koksal, S. Sharif, Cutting performance and wear
characteristics of PVD coated and uncoated carbide tools in face
milling Inconel 718 aerospace alloy, Journal of Materials Processing Technology 116 (2001) 2–9.
L. Li, N. He, M. Wang, Z.W. Wang, High speed cutting of
Inconel 718 with coated carbide and ceramic inserts, Journal of
Materials Processing Technology 129 (2002) 127–130.
T. Kitagawa, A. Kubo, K. Maekawa, Temperature and wear of
cutting tools in high speed machining of Inconel and Ti–6Al–
6V–2Sn, Wear 202 (1997) 142–148.
R. Arunachalam, M.A. Mannan, Machinability of nickel-based
high temperature alloys, Machining Science and Technology 4
(1) (2000) 127–168.
E.O. Ezugwu, S.H. Tang, Surface abuse when machining cast
iron (G-17) and nickel-base superalloy (Inconel 718) with ceramic tools, Journal of Materials Processing Technology 55 (1995)
63–69.
S. Brunet, Influence des contraintes résiduelles induites par l’usinage sur la tenue enfatigue des matériaux métalliques aéronautiques, Thèse de doctorat, ENSAM, 1991.
L. Guerville, J. Vigneau, Influence of machining conditions on
residual stresses, in: D. Dudzinski, A. Molinari, H. Schulz (Eds.),
Metal Cutting and High Speed Machining, Kluwer Academic Plenum Publishers, 2002, pp. 201–210.
B.K. Subhas, Bhat Ramaraja, K. Ramachandra, H.K. Balakrishna,
Simultaneous optimization of machining parameters for dimensionnal instability control in aero gas turbine components made
of Inconel 718 alloy, Journal of Manufacturing Science and
Engineering, Transactions ASME A22 (2000) 586–590.
B.K. Subhas, Bhat Ramaraja, K. Ramachandra, H.K. Balakrishna,
Dimensionnal instability studies in machining of Inconel 718
nickel based superalloy as applied to aerogas turbine components,
Journal of Engineering for Gas Turbines and Power, Transactions
ASME 122 (January 2000) 55–61.
Y.S. Liao, R.H. Shiue, Carbide tool wear mechanism in turning
of Inconel 718 superalloy, Wear 193 (1996) 16–24.
M. Alaudin, M.A. El Baradie, M.S.J. Hashmi, Tool life testing
in the end milling of Inconel 718, Journal of Materials Processing
Technology 55 (1995) 321–330.
S. Derrien, J. Vigneau, High speed milling of difficult to machine
alloys, in: A. Molinari, H. Schulz, H. Schulz (Eds.), Proceedings
of the First French and German Conference on High Speed Machining, University of Metz, France, 1997.
K. Itakura, M. Kuroda, H. Omokawa, H. Itani, K. Yamamoto, Y.
Ariura, Wear mechanism of coated cemented carbide tool in
coated tool in cutting of Inconel 718 super-heat resisting alloy,
International Journal of Japanese Society for Precision Engineering 33 (4) (December 1999) 326–333.
P.C. Jindal, A.T. Santhanam, U. Schleinkofer, A.F. Shuster, Performance of PVD TiN, TiCN and TiAlN coated cemented carbide
tools in turning, International Journal of Refractory Metals and
Hard Materials 17 (1999) 163–170.
H.G. Prengel, P.C. Jindal, K.H. Wendt, A.T. Santhanam, P.L.
Hedge, R.M. Penich, A new class of high performance PVD coatings for carbide cutting tools, Surface and Coatings Technology
139 (2001) 25–34.
C. Ducros, V. Benevent, F. Sanchette, Deposition, characterization and machining performance of multilayer PVD coatings on
cemented carbide cutting tools, Surface and Coatings Technology
163-164 (2003) 681–688.
N. Narutaki, Y. Yamane, K. Hayashi, T. Kitagawa, High speed
machining of Inconel 718 with ceramic tools, Annals of CIRP
42 (1) (1993) 103–106.
T.I. El-Wardany, E. Mohammed, M.A. Elbestawi, Cutting temperature of ceramic tools in high speed machining of difficult-to-
456
[23]
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
D. Dudzinski et al. / International Journal of Machine Tools & Manufacture 44 (2004) 439–456
cut materials, International Journal of Machine Tools and Manufacture 36 (5) (1996) 611–634.
M.A. Elbestawi, T.I. El-Wardany, Yan Di, Tan Min, Performance
of whisker-reinforced ceramic tools in milling nickel-based alloy,
Annals of CIRP 42 (1) (1993) 99–102.
T.I. El-Wardany, M.A. Elbestawi, High speed machining of
nickel based superalloys with silicon carbide whisker reinforced
ceramics, paper MR 95-160 IN, First International Machining and
Grinding Conference, September 1995, Dearborn, USA.
A. Gatto, L. Iuliano, Advanced coated ceramic tools for machining superalloys, International Journal of Machine Tools and
Manufacture 37 (5) (1997) 591–605.
J.W. Nowak, Y.C. Shin, F.P. Incropera, Assessment of plasma
enhanced machining for improved machinability of Inconel 718,
Journal of Manufacturing Science and Engineering 119 (1997)
119–129.
C.E. Leshock, Kim Jin-Nam, Y.C. Shin, Plasma enhanced machining of Inconel 718: modelling of workpiece temperature with
plasma heating and experimental results, International Journal of
Machine Tools and Manufacture 41 (2001) 877–897.
J. Vigneau, Usinage des matériaux aéronautiques à faible usinabilité, Techniques de l’ingénieur, Traité de Génie Mécanique, BM
1285, 1999.
Z.Y. Wang, K.P. Rajurkar, Cryogenic machining of hard-to-cut
materials, Wear 239 (2000) 168–175.
S.Y. Hong, I. Markus, W.C. Jeong, New cooling approach and
tool life improvement in cryogenic machining of titanium alloy
Ti–6Al–4V, International Journal of Machine Tool Manufacture
41 (2001) 2245–2260.
S.W. Kim, D.W. Lee, M.C. Kang, J.S. Kim, Evaluation of machinability by cutting environments in high-speed milling of difficult-to-cut materials, Journal of Processing Technology 111
(2001) 256–260.
D.A. Axinte, R.C. Dewes, Surface integrity of hot work tool steel
after high speed milling—experimental data and empirical models, Journal of Materials Processing Technology 127 (2002)
325–335.
M. Field, J.F. Khales, Review of surface integrity of machined
components, Annals of CIRP 20 (2) (1971) 153–163.
M. Jacobson, P. Dahlman, F. Gunnberg, Cutting speed influence
on surface integrity of hard turned bainite steel, Journal of
Materials Processing Technology 128 (2002) 318–323.
E. Brinkmeier, J.T. Cammet, W. König, P. Leskovar, J. Peters,
K. Tönshoff, Residual stresses—measurement and causes in
machining processes, Annals of the CIRP 31 (2) (1982) 491.
B. Bresseler, T.I. El-Wardany, M.A. Elbestawi, Material side
flow in high speed finish boring of case hardened steel, in: Proceedings of the First French and German Conference on High
Speed Machining, Metz, France, 1997, pp. 196–206.
H.A. Kishawy, M.A. Elbestawi, Effects of process parameters on
material side flow during hard turning, International Journal of
Machine Tools and Manufacture 39 (1999) 1017–1030.
C. Schlauer, R.L. Peng, M. Odén, Residual stresses in a nickelbased superalloy introduced by turning, Materials Science Forum
404-407 (2002) 173–178.
E.G. Ng, S.L. Soo, C. Sage, R.C. Dewes, R. Dewes, D.K. Aspinwall, High speed ball nose end milling of Inconel 718 with variable tool geometry—experimental and finite element analysis, in:
D. Dudzinski, A. Molinari, H. Schulz (Eds.), Metal Cutting and
High Speed Machining, Kluwer Academic Plenum Publishers,
2002, pp. 191–200.
R. Komanduri, T.A. Schroeder, On shear instability in machining
a nickel–iron base superalloy, Journal of Engineering for Industry
108 (May 1986) 93–100.
[41] F. Klocke, Dry cutting, Annals of the CIRP 46 (2) (1997)
519–526.
[42] M. Lahres, O. Doerfel, R. Neumüller, Applicability of different
hard coatings in dry machining an austenitic steel, Surface and
Coatings Technology 120-121 (1999) 687–691.
[43] E. Brinksmeier, A. Walter, R. Janssen, P. Diersen, Aspects of
cooling lubrication reduction in machining advanced materials,
Proceedings of the Institution of Mechanical Engineers 213 (Part
B) (1999) 769–778.
[44] A.R. Machado, J. Wallbank, The effect of extremely low lubricant volumes in machining, Wear 219 (1997) 76–82.
[45] H. Popke, Th. Emmer, J. Steffenhagen, Environmentally clean
metal cutting processes—machining on the way to dry cutting,
Proceedings of the Institution of Mechanical Engineers 213 (Part
B) (1999) 329–332.
[46] A.S. Varadarajan, P.K. Philip, B. Ramamoorthy, Investigations
on hard turning with minimal cutting fluid application (HTMF)
and its comparison with dry and wet turning, International Journal
of Machine Tools and Manufacture 42 (2002) 193–200.
[47] F. Klocke, G. Eisenblätter, Machinability investigation of the
drilling process using minimal cooling lubrication techniques,
Annals of the CIRP 46 (1) (1997) 19–24.
[48] H. Schulz, J. Dörr, I.J. Rass, M. Schulze, T. Leyendecker, G.
Erkens, Performance of oxide PVD-coatings in dry cutting operations, Surface and Coatings Technology 146-147 (2001) 480–
485.
[49] K. Tönshoff, A. Mohfeld, PVD-coatings wear protection in dry
cutting operations, Surface and Coatings Technology 93 (1997)
88–92.
[50] K. Tönshoff, A. Mohfeld, T. Leyendecker, H.G. Fuss, G. Erkens,
R. Wenke, T. Cselle, M. Schwenck, Wear mechanisms of
(Ti1⫺x,Alx)N coatings in dry drilling, Surface and Coatings Technology 94-95 (1997) 603–609.
[51] K. Tönshoff, B. Karpuschewski, A. Mohfeld, T. Leyendecker, G.
Erkens, H.G. Fuss, R. Wenke, Performance of oxygen-rich TiAlON coatings in dry cuttings applications, Surface and Coatings
Technology 108-109 (1998) 535–542.
[52] K.D. Bouzakis, N. Vidakis, N. Michailidis, T. Leyendecker, G.
Erkens, G. Fuss, Quantification of properties modification and
cutting performance of (Ti1⫺xAlx)N coatings at elevated temperatures, Surface and Coatings Technology 120-121 (1999) 34–43.
[53] N.M. Renevier, N. Lobiondo, V.C. Fox, D.G. Teer, J. Hampshire,
Performance of MoS2/metal composite coatings used for dry
machining and other industrial applications, Surface and Coatings
Technology 123 (2000) 84–91.
[54] V. Derflinger, H. Brändle, H. Zimmerman, New hard/lubricant
coating for dry machining, Surface and Coatings Technology 113
(1999) 286–292.
[55] B. Navinsek, P. Panjan, M. Cekada, D.T. Quinto, Interface
characterization of combination hard/solid lubricant coatings by
specific methods, Surface and Coatings Technology 154 (2002)
194–203.
[56] N.M. Renevier, H. Oosterling, U. König, H. Dautzenberg, B.J.
Kim, L. Geppert, F.G.M. Koopmans, J. Leopold, Performance
and limitation of hybrid PECVD (hard coating)–PVD magnetron
sputtering (MoS2/Ti composite) coated inserts tested for dry high
speed milling of steel and grey cast iron, Surface and Coatings
Technology 163-164 (2003) 659–667.
[57] M. Arndt, T. Kacsich, Performance of new AlTiN coatings in
dry and high speed cutting, Surface and Coatings Technology
163-164 (2003) 674–680.
[58] P.Eh. Hovsepian, W.-D. Münz, Recent progress in large scale
production of nanoscale multilayer/superlattice hard coatings,
Vacuum 69 (2003) 27–36.