[DESCRIPTION]
[Title of Invention]
CUTTING TOOL
[Technical Field]
The present invention generally relates to cutting tools, and more particularly to
cutting tools with a multi-layer coating formed on the surface of the cutting tool.
[Background Art]
Various types of coatings were conventionally used to improve the cutting
performance and extend the life of cutting tools. In order to improve the performance
of coatings, multi-layer coatings stacked with multiple layers were used, wherein each
layer has a thickness of few nanometers. In such multi-layer coatings, the
compositions of adjacent layers were configured differently, thereby resulting in
different lattice parameters and interaction between adjacent layers. Thus, the
hardness and wear resistance of the multi-layer coatings were improved. However,
when multiple layers with only a few nanometers of thickness were stacked, there was a
problem in that the accumulated torsion stress from the stacked structure caused a
decrease in impact-resistance, hence increasing the occurrences of brittle fractures.
In another prior art technology, the toughness and impact-resistance of a multi¬
layer coating were enhanced by employing an interlaid thick layer, which has a
thickness ranging from a few hundred nanometers to a few micrometers, into a structure
in which multiple layers were deposited, wherein each multiple layer has a thickness of
a few nanometers. The thick layer lowered the high torsion stress caused by the
deposited layers, wherein each layer has a few nanometers thickness to improve the
toughness and impact-resistance of the multi-layer coating. However, in order to
achieve the above, the interlaid layer had to be thick, which consequently lowered the
hardness enhancement effect expected by the interaction between the layers with a
thickness of few nanometers. This causes a problem of degrading the hardness and
wear-resistance of the multi-layer coating.
Thus, the conventional multi-layer coatings could only improve one of the
mechanical properties, i.e., hardness or toughness. Accordingly, cutting tools having
the multi-layer coatings of the prior art were only limited to achieving one purpose, i.e.,
high wear-resistance or high impact-resistance. Moreover, since one of the mechanical
properties (i.e., either wear-resistance or impact resistance) was relatively inferior
compared to the other property, the multi-layer coating of the prior art had limitations in
extending the lifespan of the cutting tool.
[Disclosure of Invention]
[Technical Problem]
An object of the present invention is to enhance the technical properties of both
wear-resistance and impact-resistance of the cutting tool, thereby allowing the cutting
tool to be used in a wide range of processes requiring either a high wear-resistance or a
high-impact resistance. Another object of the present invention is to provide a cutting
tool with a multi-layer coating, which remarkably enhances the lifespan of the cutting
tool, even with an increase in the cutting speed.
[Solution to Problem]
In order to achieve the above objects, the cutting tool of the present invention
comprises a base material and a multi-layer coating formed on the surface of the base
material. The multi-layer coating comprises an A-layer, a B-layer and a C-layer. The
layers are repeatedly deposited in the order of A-layer, C-layer and B-layer from the
base material toward an outer surface of the multi-layer coating. The A-layer consists
of ai layers comprising Ti4 6~49Al 5 1 5 N and having a thickness of 4nm~30nm, as well as
a2 layers comprising Ti34~38Al62--6 N and having a thickness of 2nm~25nm. The
layers and a2 layers are non-periodically deposited. The total number of deposited
layers of the ai layers and a2 layers ranges from 8 to 20 per lOOnm. One unit layer of
the A-layer includes the deposited layers consisting of the a i layers and a2 layers, and
has a thickness of 0.5~2.0 . The B-layer comprises Ti3 3 Al 2 66N and one unit layer
consisting of the B-layer, and has a thickness of . . The C-layer comprises
ΐ 46 91 54and has a thickness of 55~95nm.
The total thickness ratio of the B-layer to the A-layer (total B-layer
thickness/total A-layer thickness) in the multi-layer coating of the present invention is
less than 0.3.
Furthermore, the total thickness ratio of a layer to a2 layer (total a layer
thickness /total a2 layer thickness) in the A-layer ranges from 1.1-2.1 .
The A-layer in the multi-layer coating of the present invention has a hardness
adjusted to 27-32 GPa. Further, the B-layer has a hardness adjusted to 22-24 GPa,
and the C-layer has a hardness adjusted to 26-30 GPa.
[Advantageous Effects of the Invention]
According to the present invention, since the mechanical properties of wearresistance
and impact-resistance of a cutting tool are both improved by the multi-layer
coating, the cutting tool can be widely used for processes requiring either a high-wear
resistance or a high-impact resistance. Also, since both the wear-resistance and the
0 005735
impact-resistance are improved, the cutting blade is highly stable during cutting works.
Thus, the lifespan of the cutting tool can be remarkably enhanced even with the increase
of cutting speed.
[Brief Description of Drawings]
Fig. 1 is a schematic diagram of the cutting tool comprising the multi-layer
coating according to the present invention.
Fig. 2 is an outline drawing of an embodiment of a sputtering device, which is
used to form the cutting tool with the multi-layer coating according to the present
invention.
Fig. 3 is a graph in which the cutting tool lifespan is compared when the Alayer
is formed with various compositions on the base material 1 (Micro WC — —11
wt% Co).
Fig. 4 is a graph in which the cutting tool lifespan is compared when the Alayer
is formed with various compositions on the base material 2 (General WC - 10~13
wt% Co - 1-2 wt% minor metal carbide).
Fig. 5(a) is a graph showing the thickness of the non-periodically deposited a
layers and a2 layers.
Fig. 5(b) is a microscopic picture of a part of the A-layer, in which layers and
a2 layers are non-periodically deposited.
Fig. 6(a) is a graph showing the thickness of the almost periodically deposited
a layers and a2 layers.
Fig. 6(b) is a microscopic picture of a part of the A-layer in which the a layers
and the a2 layers are almost periodically deposited.
Fig. 7(a) shows a method of measuring the toughness of the non-periodically
deposited a layer and a layer and almost periodically deposited ai layers and a2 layers.
Fig. 7(b) is a graph in which the toughness is compared between the nonperiodically
deposited Ά layer and a2 layer and the almost periodically deposited
layers and a2 layers.
Fig. 8(a) is a schematic diagram of the multi-layer coating in which the total
thickness ratio of the B-layer to the A-layer (total B-layer thickness/total A-layer
thickness) is 1.
Fig. 8(b) is a schematic diagram of the multi-layer coating in which the total
thickness ratio of the B-layer to the A-layer (total B-layer thickness/total A-layer
thickness) is 0.2.
Fig. 9 is a graph in which the wear-resistance and the impact-resistance are
compared when the total thickness ratio of the B-layer to the A-layer (total B-layer
thickness/total A-layer thickness) is 1 and 0.2.
Fig. 10(a) is a picture of the cutting blade after a cutting test wherein an SCM4
workpiece is cut by the cutting tool comprising the multi-layer coating with the C-layer.
Fig. 10(b) is a picture of the cutting blade after a cutting test wherein an SCM4
workpiece is cut by the cutting tool comprising the multi-layer coating without the Clayer.
Fig. 11(a) is a picture of the cutting blade after a cutting test wherein an
SUS304 workpiece is cut by the cutting tool comprising the multi-layer coating with the
C-layer.
Fig. 11(b) is a picture of the cutting blade after a cutting test wherein SUS304
workpiece is cut by the cutting tool comprising the multi-layer coating without the Clayer.
Fig. 12(a) is a graph showing a comparison in lifespan of the cutting tool in a
cutting process with an SUS304 workpiece, wherein the comparison is made between
the experiment example with a base material (Micro WC - 5.5~ 6.5wt% Co), in which
the B-layer in the multi-layer coating according to the present invention comprises
and the C-layer comprises 3 - 3 12 6, and the comparative example,
in which the multi-layer coating comprises only the A-layer without the B-layer and the
C-layer.
Fig. 12(b) is a graph showing a comparison in the lifespan of the cutting tool in a
cutting process with an Inconel718 workpiece, wherein the comparison is made between
the experiment example with the base material (Micro WC - 5.5- 6.5wt% Co), in which
the B-layer in the multi-layer coating according to the present invention comprises
ΐ 46 915 4and the C-layer comprises Ti34 3 Al62 66 , and the comparative example
in which the multi-layer coating comprises only the A-layer without the B-layer and the
C-layer.
[Mode for the Invention]
Detailed embodiments of the present invention will be explained with reference
to the drawings.
Fig. 1 is a schematic diagram of a cutting tool comprising the multi-layer
coating according to one embodiment of the present invention. The cutting tool of the
present invention comprises a base material and a multi-layer coating formed on the
surface of the base material. The base material may be made from materials such as
tungsten carbide. The multi-layer coating formed on the surface of the base material
KR2010/005735
comprises an A-layer, a B-layer and a C-layer. The layers are repeatedly deposited in
the order of A-layer, C-layer and B-layer from the base material toward an outer surface
of the multi-layer coating.
The A-layer comprises ai layers and a2 layers, both of which have compositions
that can remarkably enhance the hardness of the multi-layer coating and which form a
depositional structure to improve the toughness of the multi-layer coating.
Furthermore, the toughness of the multi-layer coating of the present invention can be
enhanced by a B-layer, which has a predetermined thickness. The B-layer relieves the
torsion stress generated by the deposition of the a layers and a2 layers in the A-layer.
Moreover, the multi-layer coating of the present invention is structured such that a Clayer
having a predetermined composition and a predetermined thickness is first
deposited on the A-layer, wherein the B-layer is then deposited on top of the C-layer.
By doing so, the B-layer can be uniformly formed and the toughness enhancement
effect by the B-layer can be maximized. As such, the multi-layer coating of the
present invention can enhance its toughness by depositing layer and a2 layer nonperiodically.
The toughness enhancement effect of the B-layer is maximized by the Clayer.
Thus, the B-layer, which is necessary for sufficient toughness, can be thinly
formed. As the B-layer becomes thin, the thickness ratio of the A-layer increases,
which increases the hardness of the entire multi-layer coating. Also, contrary to
expectations that the toughness of the entire multi-layer coating would be lowered when
the B-layer is formed to be thin, when the total thickness ratio of the B-layer to that of
the A-layer (total B-layer thickness/total A-layer thickness) is controlled to be less than
0.3, the toughness of the multi-layer coating is enhanced. Hereinafter, functions and
properties of each layer of the multi-layer coating according to the present invention
will be explained in detail.
The A-layer is formed by alternately depositing the a layers and a layers,
wherein the ai layers and a2 layers have compositions different from each other. The
ai layers comprise Ti 9A l51-. N, while the a2 layers comprise Ti34~3 Al62~66N. As
such, the hardness enhancement effect caused by the interaction between the layers is
maximized. This leads to a remarkable enhancement in the wear-resistance of the
multi-layer coating, as well as to a remarkable improvement in the lifespan of the
cutting tool. The inventor of the present invention conducted several cutting
performance tests with respect to the compositions of the a.\ layer and a2 layer, as
described below:
[Experiment 1]
P T/KR2010/005735
In this experiment, the coating was formed on the surfaces of the base material
1 (Micro WC - 9~l lwt% Co) and base material 2 (General WC - 0 3 t% Co -
1-2 wt% minor metal carbide). The coatings on the surfaces of these two base
materials were formed by two types of Arc targets as shown in Fig. 2. Five different
types of coatings were then deposited on each base material. In each experiment
example, targets with compositions as shown in Table 1 below were used as the O ¬
position target and the R-position target. In experiment examples 1~4, multi-layer
coatings were formed by arranging targets in the Q-position and R-position with
different compositions. Further, in experiment example 5, a single-layer coating
was formed by arranging the same type of target in the Q-position and R-position
with a composition of 50150.
[Table 1]
The cutting performance test was conducted by measuring the lifespan of the
cutting tool during a cutting process of an SKT4 workpiece and an SKD1 1 workpiece.
The cutting performance test was conducted as follows: the SKT4 workpiece was cut
via dry-cutting under conditions of a 150m/min cutting speed, a 0.1 mm/tooth feeding
rate and a 2.0mm cutting depth. SKD1 1 workpiece was cut via dry-cutting under the
conditions of 150m/min in cutting speed, 0.12mm/tooth in feeding rate and 2.0mm in
cutting depth. Both cutting processes used an octagon milling insert. The lifespan of
the cutting tool was compared and evaluated by measuring the cutting distance until the
abrasion amount of the side surface reached 0.45mm. Fig. 3 shows the lifespan of the
cutting tool comprising the coatings formed on the surface of base material 1, using the
targets of each experiment example. Fig. 4 shows the lifespan of a cutting tool
comprising the coatings formed on the surface of base material 2, using the targets of
each experiment example. Figs. 3 and 4 confirm that the cutting tool, which comprises
the multi-layer coating formed by using the Q-target that has the composition of
Ti50Al50 and the R-target that has the composition of Ti33Al , has a remarkably
enhanced lifespan compared to other experiment examples. The two types of layers of
the multi-layer coatings formed by the targets of experiment example 4 were identified
to have the compositions of Ti46 49Al5i 5 N and Ti34~38Al62~66N. From this, it can be
understood that if layers having the compositions of Ti A l 1 54N and Ti34 8Al62 N
are alternately deposited, then the hardness enhancement expected by the interaction
between layers due to the difference in lattice constants can be maximized and the wearresistance
of the multi-layer coating becomes remarkably enhanced. This eventually
extends the lifespan of the cutting tool.
Moreover, in the A-layer, the total thickness ratio of the a layers to the a2 layers
(total ai layer thickness/total a2 layer thickness) is adjusted to be 1.1—2.1. If the total
thickness ratio of the ai layer to the a2 layer (total a.\ layer thickness/total a2 layer
thickness) in the A-layer went below 1.1, then the wear-resistance was enhanced, but the
impact-resistance was degraded. However, if the total thickness ratio exceeded 2.1,
then the impact-resistance increased, but the wear-resistance was decreased. Thus, in
order to keep both the wear-resistance and the impact-resistance in good shape, the total
thickness ratio of the a layer to the a2 layer (total a.\ layer thickness/total a2 layer
thickness) was limited to be between 1.1 and 2.1.
Further, the thickness of the a i layers and a2 layers making up the A-layer falls
within the range of 4nm~30nm and 2nm~25nm. Also, they are deposited nonperiodically.
That is, the ai layer and a2 layer each have thicknesses in the range as
stated above. 8-20 layers of the . layers and the a2 layers in total are deposited per
lOOnm. One unit layer of the A-layer wherein the & layers and a2 layers are deposited
as stated above has a thickness of 0.5~2.0/zm. The toughness of the A-layer is
remarkably enhanced through such non-periodical deposition. Accordingly, the multi¬
layer coating of the present invention can provide the functional effect of maximizing
the hardness enhancement by the interaction between layers, using ai layers and a2
layers having the compositions as described above. Furthermore, the multi-layer
coating of the present invention can also improve the toughness of the A-layer by
depositing the Ά layer and a2 layer such that they have a non-periodical thickness. The
inventor of the present invention conducted cutting performance tests with respect to the
thicknesses of the a layer and a2 layer, as follows.
[Experiment 2]
In experiment example 1, a i layers (Ti 7Al53N) that had thicknesses of
6nm~21nm and a2 layers (Ti37Al 3N) that had thicknesses of 3nm~15nm were nonperiodically
deposited, as shown in Fig. 5(a). Fig. 5(b) is a picture of the multi-layer
coating of experiment example 1 as observed through a microscope. In experiment
2010/005735
example 2, ai layers (Ti47Al 3N) that had thicknesses of 3~7nm and a2 layers (Ti3 Al63N)
that had thicknesses of 3~6nm were deposited periodically, as shown in Fig. 6(a). Fig.
6(b) is a picture of the multi-layer coating structure of experiment example 2 as
observed through a microscope.
In this experiment, the cutting performance of a cutting tool comprising said
two coatings was tested. Fig. 7(b) shows two experiment examples of the cutting
performance test and the test results from two comparative examples. The cutting
performance test was conducted using a milling cutting method as shown in Fig. 7(a).
The test with the SKT4 workpiece was started with the conditions of V=50 m/min,
d=2mm, dry, and 0.15 mm/tooth initial feeding rate and using a SPKN 1203 type
milling insert. Cutting the workpiece 200mm without damaging the insert was
referred to as 1 pass. The test was conducted by increasing the feeding rate by
0.07mm/tooth interval until the insert was damaged (e.g., 0.15 - 0.22 - 0.29 - 0.36 -
0.43...), and the toughness of each insert was relatively evaluated, according to how
many "passes" the insert has gone through without damage.
As shown in the result of this experiment, the experiment examples with the
non-periodical depositions of the a layers and a2 layers demonstrate a toughness twotimes
greater than the comparative examples, which had an almost periodical deposition.
The B-layer in the multi-layer coating of the present invention has a
composition of Ti34~38Al62- N and one unit layer of the B-layer has a thickness of
0. 1 ~ .5. Due to the thickness of over 0.1 , the B-layer relieves the torsion stress
accumulated in the A-layer. Further, since the B-layer has a thickness of under 0.5 ,
it prevents wear-resistance degradation in the multi-layer coating.
In the multi-layer coating of the present invention, the total thickness ratio of
the B-layer to the A-layer (total B-layer thickness/total A-layer thickness) is controlled
to be less than 0.3. Thus, the functional effect of remarkably enhancing the wearresistance
of the multi-layer coating is provided. The inventor of the present invention
conducted a cutting performance test with respect to the total thickness ratio of the Blayer
to the A-layer (total B-layer thickness/total A-layer thickness), as follows:
[Experiment 3]
As shown in Fig. 8(a), experiment example 1 of this test shows a cutting
performance experiment wherein a multi-layer coating is formed such that the total
thickness ratio of the B-layer to the A-layer (total B-layer thickness/total A-layer
thickness) is 1. As shown in Fig. 8(b), experiment example 2 shows a cutting
performance test regarding the wear-resistance and impact-resistance of the cutting tool,
KR2010/005735
wherein a multi-layer coating is formed such that the total thickness ratio of the B-layer
to the A-layer (total B-layer thickness/total A-layer thickness) is 0.3. The test on
wear-resistance was conducted under two conditions, one with an SCM4 workpiece
under conditions of V=250, fz=0.1, ap=3.0, and the other with an SUS304 workpiece
under conditions of V=150, fz=0.1, ap=2.0. The test on impact-resistance was
conducted with an SCM440 workpiece under conditions of N=100, (Start)fz=0.28,
ap=2.0. Fig. 9 presents a graph showing a comparison between the cutting
performance test results of experiment examples 1 and 2. The average percentage in
Fig. 9 refers to the average lifespan ratio with respect to a cutting tool comprising a
coating without the B-layer.
As shown in the test results provided in Fig. 9, experiment example 1 with the
SUS304 workpiece, wherein the total thickness ratio of the B-layer to the A-layer (total
thickness of the B-layer/total thickness of the A-layer) is 1, showed that the wearresistance
is rather degraded when compared to the coating without the B-layer. On
the other hand, experiment example 2, wherein the total thickness ratio of the B-layer to
the A-layer (total B-layer thickness/total A-layer thickness) was controlled to be 0.3,
showed that not only the wear-resistance but also the impact-resistance was enhanced.
These experiment examples indicate that despite the decrease in thickness ratio of the
B-layer, which primarily controls the toughness, the impact-resistance can be enhanced.
This is because when the total thickness ratio of the B-layer to the A-layer (total B-layer
thickness/total A-layer thickness) becomes less than 0.3, more interfaces are formed
between the A-layer and the B-layer. Further, since crack propagation is suppressed
by crack separation and crack deflection at the interfaces, the toughness is increased.
The C-layer, which is part of the multi-layer coating of the present invention
comprises Ti46 9Al51 N and has a thickness of 55~95nm. The C-layer is always
formed on top of the A-layer, and functions as a transfer layer between the A-layer and
the B-layer. As the composition and thickness of the C-layer are kept within the
above-stated range, the C-layer helps the B-layer form uniformly and helps to maximize
the toughness enhancement effect of the B-layer. When the thickness of the C-layer
becomes less than 50nm, it is difficult to form the B-layer uniformly on top of the Clayer
since the C-layer cannot cover the entire insert uniformly. When the thickness of
the C-layer exceeds 95run, the impact-resistance might be degraded. The inventor of
the present invention conducted a cutting process with respect to the functional effects
of the C-layer under the following conditions. The cutting blade after the cutting is as
shown in Figs. 0 and 1.
0 005735
10
[Experiment 4]
Comparative examples 1-4 of this test employed coatings, which are the same
as those used in experiment example 2 of Experiment 3. Such coatings do not
comprise the C-layer. Experiment examples 1-4 of this experiment employed the
same coating as that used in experiment example 2 of Experiment 3, but with a C-layer
this time. Experiment examples 1 and 2, as well as comparative examples 1 and 2, ran
the test using an SCM4 workpiece under conditions of V=250m/min, f=0.1 mm/tooth, dc=
3.0mm, dry, and a 0.8M cutting length, and the cutting blades were observed
thereafter. Experiment examples 3 and 4, as well as comparative examples 3 and 4,
ran the test with an SUS304 workpiece under the conditions of V=150m/min,
f=0.1 mm/tooth, d-c=2.0mm, dry, and a 0.8M cutting length, and the cutting blades were
observed thereafter.
Fig. 10(a), which shows experiment examples 1 and 2, and Fig. 10(b), which
shows comparative examples 1 and 2, indicate that experiment examples 1 and 2
provide a greater excellence in fine chipping and side surface abrasion property,
compared to comparative examples 1 and 2. Moreover, Fig. 11(a), which shows
experiment examples 3 and 4, and Fig. 11(b), which shows comparative examples 3 and
4, show that experiment examples 3 and 4 provide a greater excellence in fine chipping
and side surface abrasion property, compared to comparative examples 3 and 4.
Further, they show that the deviation is smaller in experiment examples 3 and 4 than
comparative examples 3 and 4.
From these results, it is clear that the addition of the C-layer maximizes the
toughness enhancement effect of the B-layer and leads to further enhancements of the
wear-resistance and impact-resistance of the entire coating.
Moroever, the inventor of the present invention conducted the following test in
order to confirm the coating performance when the compositions of the B-layer and Clayer
are exchanged with each other.
[Experiment 5]
The present experiment switches the composition of the B-layer with the
composition of the C-layer in a turning operation test and then compares the results.
Figs. 12(a) and 12(b) show the performance test results of the multi-layer coatings in the
experiment with an SUS304 workpiece and an Inconel718 workpiece, respectively, both
using a parallelogram-shaped insert (base material: Micro WC -5.5%~6.5wt%Co). In
the experiment, the multi-layer coating of the experiment example comprises the Alayer,
the C-layer and the B-layer as in the present invention. However, the
5735
compositions of the B-layer and C-layer are switched with each other (i.e., the B-layer
comprises Ti46 9Al 5 1 54N and the C-layer comprises 34 3 162 6) . The multi-layer
coating of the comparative examples comprises only the A-layer.
This experiment confirms that even though the B-layer and the C-layer are
deposited with their compositions being switched with each other, the present invention
still performs better than the comparative examples that exclude the B-layer and the Clayer.
As confirmed in the above experiment results, the present invention
successfully maximized the hardness enhancement by the interaction between the layers
by adjusting the compositional differences in the subordinate layers of the A-layer.
Simultaneously, the present invention also enhanced the toughness of the A-layer by
depositing the subordinate layers of the A-layer non-periodically. By controlling the
total thickness ratio of the B-layer to the A-layer to be less than 0.3, the wear-resistance
of the entire coating can be maintained while the impact-resistance is enhanced.
Furthermore, by the addition of the C-layer, which helps the B-layer be formed to be
uniformly, the uniformity of the B-layer can be enhanced, and the toughness
enhancement effect of the B-layer can be maximized. Thus, the present invention
successfully keeps both the wear-resistance and the impact-resistance in good shape,
thereby providing a cutting tool that can be widely used for various purposes and which
has a remarkably enhanced lifespan.
The present invention has been explained with preferable embodiments so far.
However, the embodiments are only examples, and the invention is not limited thereto.
A person skilled in the art will understand that the present invention can be practiced
with various modifications within the scope of the invention.
[CLAIMS]
1. A cutting tool, comprising:
a base material and a multi-layer coating formed on a surface of said base
material, said multi-layer coating comprising an A-layer, a C-layer and a B-layer which
are repeatedly deposited in an order of A-layer, C-layer and B-layer from the base
material toward an outer surface of the multi-layer coating;
the A-layer having a thickness of 0.5-2. and comprising a i layers having
thicknesses of 4nm~30nm and comprising and a2 layers having
thicknesses of 2nm~25nm and comprising Ti34~3 Al 2 N , wherein 8-20 layers of said
a\ layers and a2 layers are non-periodically deposited per lOOnm;
the B-layer having a thickness of 0.1 m~ 0 .5 i and comprising 34~38162 66;
the C-layer having a thickness of 55-95 run and comprising Ti46~49Al 5i 54N;
wherein a total thickness ratio of the B-layer to the A-layer in the multi-layer
coating (total B-layer thickness/total A-layer thickness) is less than 0.3.
2. A cutting tool, comprising:
a base material and a multi-layer coating formed on a surface of said base
material, said multi-layer coating comprising an A-layer, a C-layer and a B-layer which
are repeatedly deposited in an order of A-layer, C-layer and B-layer from the base
material toward an outer surface of the multi-layer coating;
the A-layer having a thickness of 0.5~2.0 m and comprising a i layers having
thicknesses of 4nm~30nm and comprising Ti4 - 9A15 1 54N, and a layers having
thicknesses of 2nm~25nm and comprising Ti34 3 A l6 2~ 6 , wherein 8-20 layers of said
a layers and a2 layers are non-periodically deposited per lOOnm;
the B-layer having a thickness of 0.1 m~ 0 .5 im and comprising Ti46- 9A 1 -.54 ;
the C-layer having a thickness of 55~95nm and comprising 3 38162~66;
wherein a total thickness ratio of the B-layer to the A-layer in the multi-layer
coating (total B-layer thickness/total A-layer thickness) is less than 0.3.
3. The cutting tool according to Claim 1 or 2, wherein a total thickness of the alayers to the a2 layers (total a\ layer thickness/total a2 layer thickness) in the A-layer is
1.1 - 2 .1.
4. The cutting tool according to Claim 1 or 2, wherein said A-layer has a hardness
adjusted to 27-32 GPa, wherein said B-layer has a hardness adjusted to 22-24 GPa, and
wherein said C-layer has a hardness adjusted to 26-30 GPa.