JP2014087858A - Cutting tool - Google Patents

Abstract

To provide a cutting tool capable of reliably suppressing wear and peeling of a hard coating layer and extending the tool life even when carbon steel is used as a work material.
A first composite nitride layer 11 and a second composite nitride layer 12 are alternately arranged as a hard coating layer 3 on a surface 2a of a tool base 2 made of a tungsten carbide base cemented carbide. The first composite nitride layer 11 is formed directly on at least the surface 2a of the tool base 2 and has an average layer thickness of 0.5 to 1.25 μm. When expressed by Al _1-X Ti _X ) N, it comprises a composite nitride layer of Al and Ti having an average composition satisfying 0.3 ≦ X ≦ 0.7 (where X value is an atomic ratio), The second composite nitride layer 12 has an average layer thickness of 0.5 to 1.25 μm, and 0.2 ≦ a ≦ 0 when expressed by _a composition formula: (Al _1-a Cr _a ) N. .6 (where the a value is the atomic ratio) and consists of an Al and Cr composite nitride layer having an average composition.
[Selection] Figure 1

Description

  The present invention relates to a cutting tool in which a hard coating layer made of a composite nitride layer is formed on the surface of a tool base made of a tungsten carbide base cemented carbide.

Conventionally, as this type of cutting tool, for example, as shown in Patent Document 1 below, as a hard coating layer having a hardness higher than that of the tool base, Al and Ti are provided on the surface of the tool base made of tungsten carbide base cemented carbide. A drill or the like in which a composite nitride layer is formed is known.
In this cutting tool, the Al component contained in the hard coating layer improves the high-temperature hardness and heat resistance of the hard coating layer, and the Ti component contained in the hard coating layer improves the high-temperature strength of the hard coating layer. Yes.

Japanese Patent Publication No. 5-67705

  However, in the conventional cutting tool described above, when carbon steel is cut as a work material, a hard coating layer that has become hot due to frictional heat or the like is cut as compared with the case of cutting materials other than the carbon steel. It has been a problem that it is easily worn or peeled off due to adhesion to the material. Specifically, in a drill, for example, when carbon steel is cut, the hard coating layer easily wears or peels off from a margin portion adjacent to the outer peripheral blade, and margin wear tends to occur.

  The present invention has been made in view of such circumstances, and even when carbon steel is used as a work material, wear and delamination of the hard coating layer can be reliably suppressed, and the tool life can be reduced. It aims at providing the cutting tool which can be extended.

In order to solve such problems and achieve the above object, the present invention proposes the following means.
That is, the cutting tool of the present invention has a total of four layers of the first composite nitride layer and the second composite nitride layer alternately on the surface of the tool base made of tungsten carbide base cemented carbide as the hard coating layer. The first composite nitride layer is formed directly on at least the surface of the tool base, has an average layer thickness of 0.5 to 1.25 μm, and has a composition formula: (Al _{1− X} Ti _X ) N, the composite nitride layer of Al and Ti having an average composition satisfying 0.3 ≦ X ≦ 0.7 (where X value is an atomic ratio), The composite nitride layer has an average layer thickness of 0.5 to 1.25 μm, and 0.2 ≦ a ≦ 0.6 (provided that expressed by the composition formula: (Al _1-a Cr _a ) N) , A is a composite nitride layer of Al and Cr having an average composition satisfying an atomic ratio).

In the cutting tool of the present invention, a hard coating layer is formed by alternately laminating a total of four or more first composite nitride layers and second composite nitride layers on the surface of a tool base made of a tungsten carbide base cemented carbide. Is formed.
When the first composite nitride layer is expressed by a composition formula: (Al _1-X Ti _X ) N, 0.3 ≦ X ≦ 0.7 (where the X value is an atomic ratio) is satisfied. It consists of a composite nitride layer of Al and Ti with an average composition (hereinafter abbreviated as (Al, Ti) N layer), and such (Al, Ti) N layer is formed directly on the surface of at least the tool base. Therefore, the bonding strength between the hard coating layer and the surface of the tool base is stably increased, and the peeling of the hard coating layer is suppressed.

Further, the second composite nitride layer satisfies 0.2 ≦ a ≦ 0.6 (where a value is an atomic ratio) when expressed by the composition formula: (Al _1-a Cr _a ) N. A composite nitride layer of Al and Cr having an average composition (hereinafter abbreviated as (Al, Cr) N layer), and such (Al, Cr) N layer is brought into contact with the work material, When carbon steel is used as the work material, the hard coating layer is difficult to adhere to the carbon steel even at high temperatures during cutting, and wear and peeling of the hard coating layer are stably suppressed.

  Specifically, the Al component contained in the first and second composite nitride layers improves the high temperature hardness and heat resistance of the hard coating layer. Further, the high temperature strength and the like of the hard coating layer are improved by the Ti component contained in the first composite nitride layer. Further, the Cr component contained in the second composite nitride layer improves high temperature oxidation resistance, welding resistance, and the like.

And since the average layer thickness of each of the first and second composite nitride layers described above is 0.5 μm or more, crystal growth is sufficiently promoted in each layer during the production of the hard coating layer, Generation of internal stress is suppressed and impact resistance is stably improved.
Specifically, when the average layer thickness is less than 0.5 μm, it is difficult for crystals to grow sufficiently in each layer at the time of production, and internal stress tends to increase, which may reduce impact resistance.

In addition, since the average layer thickness of each of the first and second composite nitride layers is set to 1.25 μm or less, cracks may greatly develop in the hard coating layer in the layer thickness direction. Is prevented. Specifically, when a crack develops in the hard coating layer, after the crack that has progressed in the layer thickness direction from the outermost layer reaches the interlayer, it should easily proceed in the direction perpendicular to the layer thickness direction along the interlayer. Therefore, the average layer thickness of each layer constituting the hard coating layer is suppressed to a small value of 1.25 μm or less, so that the hard coating layer is largely prevented from peeling off from the surface of the tool substrate, and the tool substrate It is prevented that the surface of is exposed to the outside.
Specifically, when the average layer thickness exceeds 1.25 μm, cracks are likely to be greatly propagated in the layer thickness direction of the hard coating layer, and the hard coating layer is easily separated from the surface of the tool base. As a result, the surface of the tool base is likely to be exposed, and the wear resistance may not be ensured.

  Furthermore, in the present invention, since the first and second composite nitride layers are alternately provided in a total of four or more layers, the performance of each layer described above is maintained over a long period of time, and high-quality cutting is stabilized. Can be done.

  Specifically, in this cutting tool, at least two or more of the first and second composite nitride layers are provided as the hard coating layer, respectively, and therefore, a part of these first and second composite nitride layers. Even if the surface is worn or peeled off, the other first and second composite nitride layers are newly exposed from the inside in the layer thickness direction, and the above-described effects (suppressing wear and peeling of the hard coating layer are suppressed. And the effect of improving impact resistance can be stably obtained over a long period of time.

  In addition, since the hard coating layer is composed of a total of four or more layers, when the crack is about to progress toward the inside in the layer thickness direction in the hard coating layer, the crack does not pass through a plurality of layers. Since the crack does not reach the surface of the tool base and the cracks easily propagate along the layers as described above, the cracks are effectively suppressed from progressing in the layer thickness direction. That is, by providing three or more layers in the hard coating layer, it is remarkably prevented that cracks penetrate the hard coating layer and reach the base material (tool base).

  The above-described effects of the present invention can be remarkably obtained not only when carbon steel is used as a work material but also when a material other than carbon steel is used as the work material.

  Thus, according to the present invention, even when carbon steel is used as the work material, wear and delamination of the hard coating layer can be reliably suppressed, and the tool life can be extended.

  In the cutting tool of the present invention, the outermost layer of the hard coating layer may be the second composite nitride layer.

  In this case, when carbon steel is used as the work material, the outermost layer of the hard coating layer in contact with the work material is an (Al, Cr) N layer. The hard coating layer is less likely to adhere to the carbon steel, and wear and peeling of the hard coating layer are more significantly suppressed.

  Moreover, the cutting tool of this invention WHEREIN: The average layer thickness as the whole of the said hard coating layer is good also as being 2-5 micrometers.

In this case, the above-described effect can be more reliably obtained while preventing the hard coating layer from being peeled off from the surface of the tool base in a wide range.
Specifically, when the average thickness of the hard coating layer as a whole is less than 2 μm, the thickness of each of the hard coating layers composed of four or more first and second composite nitride layers is reduced. In the thinned layer, the crystal does not grow sufficiently, or the internal stress increases, so that the above-described effects may not be sufficiently obtained.
In addition, when the average thickness of the hard coating layer as a whole exceeds 5 μm, the hard coating layer is easily peeled from the surface of the tool base in a wide range, and such peeling causes the surface of the tool base. When exposed to the outside, there is a risk that the wear is likely to proceed significantly from the exposed portion.

  According to the cutting tool of the present invention, even when carbon steel is used as the work material, wear and peeling of the hard coating layer can be reliably suppressed, and the tool life can be extended.

It is a longitudinal cross-sectional view explaining the hard coating layer of the cutting tool which concerns on one Embodiment of this invention.

Hereinafter, a cutting tool 1 according to an embodiment of the present invention will be described with reference to the drawings.
The cutting tool 1 of this embodiment is a drill or miniature drill used for cutting such as drilling of a work material made of carbon steel, for example, and at least a contact portion of the tool base 2 with the work material is surface-coated. Is a surface-coated cutting tool to which

  As shown in FIG. 1, the cutting tool 1 includes a tool base 2 made of a tungsten carbide-based cemented carbide and a hard coating layer 3 formed on the surface 2 a of the tool base 2.

  The hard coating layer 3 is formed by alternately laminating a total of four or more first composite nitride layers 11 and second composite nitride layers 12. In this embodiment, the hard composite layer 3 is formed by providing the first composite nitride layer 11 and the second composite nitride layer 12 on the surface 2a of the tool base 2 in total, two layers each of which is two layers. Yes.

The first composite nitride layer 11 is directly formed on at least the surface 2a of the tool base 2, and has an average layer thickness of 0.5 to 1.25 μm. In the example shown in the figure, the first composite nitride layer 11 is provided in two layers at intervals in the layer thickness direction (vertical direction in FIG. 1), and one of these layers (arranged inside the layer thickness direction). Layer) is formed directly on the surface 2a of the tool base 2, and the other layer (layer disposed outside the layer thickness direction) is formed on the second composite nitride layer 12 described later. .
The first composite nitride layer 11 is an average satisfying 0.3 ≦ X ≦ 0.7 (where the X value is an atomic ratio) when represented by the composition formula: (Al _1-X Ti _X ) N. It consists of a composite nitride layer ((Al, Ti) N layer) of Al and Ti having a composition.

The second composite nitride layer 12 is formed on the first composite nitride layer 11 and has an average layer thickness of 0.5 to 1.25 μm. In the illustrated example, the second composite nitride layer 12 is provided in two layers at intervals in the layer thickness direction, and these layers are formed on the two first composite nitride layers 11 described above, respectively. ing.
The second composite nitride layer 12 is an average satisfying 0.2 ≦ a ≦ 0.6 (where a value is an atomic ratio) when expressed by _a composition formula: (Al _1-a Cr _a ) N. It consists of a composite nitride layer ((Al, Cr) N layer) of Al and Cr of composition.

Of the first and second composite nitride layers 11 and 12 constituting the hard coating layer 3, the outermost layer (the outer side in the layer thickness direction of the hard coating layer 3 (the side opposite to the surface 2a of the tool base 2)) The layer located in the part) is the second composite nitride layer 12 which is an (Al, Cr) N layer. That is, the hard coating layer 3 formed by alternately laminating the first and second composite nitride layers 11 and 12 has a total of 6 layers, 8 layers, etc. It is preferable that the total is an even number and the number of each of the layers 11 and 12 is the same. More desirably, as in the present embodiment, the hard coating layer 3 may be formed by alternately laminating a total of four first and second composite nitride layers 11 and 12.
Moreover, the average layer thickness as a whole of the hard coating layer 3 is in the range of 2 to 5 μm.

The hard coating layer 3 of this embodiment is produced on the surface 2a of the tool base 2 by the following procedure, for example.
Using an arc ion plating apparatus, the tool base 2 is disposed in the furnace, and the furnace is heated to a temperature of about 500 ° C. by a heating means such as a heater, and an Al—Ti alloy having a predetermined composition is set. Arc discharge was generated between the cathode electrode (evaporation source) and the anode electrode under the condition of current: 100 A, and simultaneously nitrogen gas (N ₂ ) was introduced into the furnace as a reaction gas, pressure: 3.5 Pa. A bias voltage of −30 V is applied to the tool base 2. Thus, the first composite nitride layer 11 (the innermost layer, that is, the inner side in the layer thickness direction of the hard coating layer 3 (the surface 2a of the tool base 2) is formed on the surface 2a of the tool base 2. Layer) located at the end of side) is formed by vapor deposition.

  Next, arc discharge is generated under the condition of current: 100 A between the cathode electrode (evaporation source) on which the Al—Cr alloy having a predetermined composition is set and the anode electrode, and the other conditions are the same as those described above. Then, a second composite nitride layer 12 made of an (Al, Cr) N layer is deposited on the first composite nitride layer 11 formed as the innermost layer.

  Similarly, a first composite nitride layer 11 is newly deposited on the second composite nitride layer 12, and a second composite nitride is newly formed on the first composite nitride layer 11. The hard coating layer 3 composed of a total of four (Al, Ti) N layers and (Al, Cr) N layers is formed on the surface 2a of the tool base 2 by vapor-depositing the physical layer 12.

  The average layer thickness of each of the layers 11 and 12 constituting the hard coating layer 3 can be controlled by the operating time of the apparatus, and in this embodiment, the target thickness of each of the layers 11 and 12 is all 1 μm. . That is, the target thickness of the hard coating layer 3 as a whole is 4 μm.

  And the hard coating layer 3 of this embodiment manufactured in this way was, for example, Vickers hardness: 2900 Hv and oxidation start temperature: 1100 ° C. On the other hand, a hard coating layer (target thickness: 4 μm) made of a single layer of (Al, Ti) N layer manufactured as a reference example (comparative example) different from this embodiment has a Vickers hardness of 2800 Hv and an oxidation start temperature. : 840 ° C. That is, the hard coating layer 3 composed of a total of four layers described in the present embodiment is superior in hardness (high temperature hardness), heat resistance, and high temperature strength as compared with a conventional hard coating layer composed of a single layer. Even when the temperature becomes high due to frictional heat with the work material, etc., it has a property that wear and peeling are unlikely to occur.

In the cutting tool 1 of the present embodiment described above, the first composite nitride layer 11 and the second composite nitride layer 12 are alternately arranged on the surface 2a of the tool base 2 made of tungsten carbide base cemented carbide in total 4 in total. The hard coating layer 3 is formed by laminating more than one layer.
When the first composite nitride layer 11 is expressed by a composition formula: (Al _1-X Ti _X ) N, 0.3 ≦ X ≦ 0.7 (where X value is an atomic ratio) is satisfied. A composite nitride layer ((Al, Ti) N layer) of Al and Ti having an average composition is formed, and such (Al, Ti) N layer is directly formed on the surface 2a of the tool base 2 at least. Therefore, the bonding strength between the hard coating layer 3 and the surface 2a of the tool base 2 is stably increased, and the peeling of the hard coating layer 3 is suppressed.

Further, the second composite nitride layer 12 satisfies 0.2 ≦ a ≦ 0.6 (where a value is an atomic ratio) when expressed by _a composition formula: (Al _1-a Cr _a ) N. A composite nitride layer of Al and Cr ((Al, Cr) N layer) having an average composition, and the (Al, Cr) N layer is brought into contact with the work material so that the work material When carbon steel is used, the hard coating layer 3 is hardly attached to the carbon steel at the time of cutting even at a high temperature, and wear and peeling of the hard coating layer 3 are stably suppressed.

  Specifically, the Al component contained in the first and second composite nitride layers 11 and 12 improves the high temperature hardness and heat resistance of the hard coating layer 3. Moreover, the high temperature strength of the hard coating layer 3 is improved by the Ti component contained in the first composite nitride layer 11. Further, the Cr component contained in the second composite nitride layer 12 improves high-temperature oxidation resistance, welding resistance, and the like.

Since the first and second composite nitride layers 11 and 12 described above have an average layer thickness of 0.5 μm or more, crystal growth occurs in each of the layers 11 and 12 when the hard coating layer 3 is manufactured. Is sufficiently promoted, the generation of internal stress is suppressed, and the impact resistance is stably improved.
Specifically, when the average layer thickness is less than 0.5 μm, it is difficult for crystals to grow sufficiently in each of the layers 11 and 12 during manufacturing, the internal stress tends to increase, and the impact resistance may be reduced. is there.

Moreover, since the average layer thickness of each of the first and second composite nitride layers 11 and 12 is 1.25 μm or less, cracks greatly develop in the hard coating layer 3 in the layer thickness direction. This is prevented. Specifically, when a crack progresses in the hard coating layer 3, after the crack that has progressed in the layer thickness direction from the outermost layer reaches the interlayer, it tends to progress in a direction perpendicular to the layer thickness direction along the interlayer. Accordingly, the average layer thickness of each of the layers 11 and 12 constituting the hard coating layer 3 is suppressed to a small value of 1.25 μm or less, so that the hard coating layer 3 is largely separated from the surface 2 a of the tool base 2. Is suppressed, and the surface 2a of the tool base 2 is prevented from being exposed to the outside.
Specifically, when the average layer thickness exceeds 1.25 μm, cracks are likely to greatly increase in the layer thickness direction of the hard coating layer 3, and the hard coating layer 3 is largely gathered from the surface 2 a of the tool base 2. It becomes easy to peel off, the surface 2a of the tool base 2 is likely to be exposed, and there is a possibility that the wear resistance cannot be ensured.

  Further, in the present embodiment, since the first and second composite nitride layers 11 and 12 are alternately provided in a total of four or more layers, the performance of each of the layers 11 and 12 described above is maintained over a long period of time. It is possible to stably perform high-quality cutting.

  Specifically, in this cutting tool 1, at least two or more first and second composite nitride layers 11 and 12 are provided as the hard coating layer 3, respectively. Even if part of the material layers 11 and 12 is worn or peeled off, the other first and second composite nitride layers 11 and 12 are newly exposed from the inside in the layer thickness direction, and the above-mentioned Effects (an effect of suppressing wear and peeling of the hard coating layer 3 and an effect of improving impact resistance) can be obtained stably over a long period of time.

  In addition, since the hard coating layer 3 is composed of a total of four or more layers, the crack passes through a plurality of layers when the crack is about to progress inward in the layer thickness direction in the hard coating layer 3. Unless this is done, the surface 2a of the tool base 2 is not reached, and cracks are likely to propagate along the layers as described above, so that the cracks are effectively suppressed from progressing in the layer thickness direction. That is, by providing three or more layers in the hard coating layer 3, it is remarkably prevented that cracks penetrate the hard coating layer 3 and reach the base material (tool base 2).

  Note that the effects described above in the present embodiment can be remarkably obtained not only when carbon steel is used as a work material but also when a material other than carbon steel is used as the work material.

  Thus, according to the present embodiment, even when carbon steel is used as the work material, wear and peeling of the hard coating layer 3 can be reliably suppressed, and the tool life can be extended. In particular, when the margin part of the drill (cutting tool 1) is covered with the hard coating layer 3 as in the present embodiment, when using a material other than carbon steel as the work material, Even when carbon steel is used, margin wear can be remarkably suppressed, and the tool life is extended.

Moreover, since the outermost layer of the hard coating layer 3 is the second composite nitride layer 12, the following effects are obtained.
That is, when carbon steel is used as the work material, the outermost layer of the hard coating layer 3 that contacts the work material is an (Al, Cr) N layer, so even if the temperature becomes high due to frictional heat or the like during cutting. The hard coating layer 3 is less likely to adhere to the carbon steel, and wear and peeling of the hard coating layer 3 are more significantly suppressed.

Moreover, since the average layer thickness as a whole of the hard coating layer 3 is 2-5 micrometers, there exists the following effect.
That is, while preventing the hard coating layer 3 from being peeled over a wide range from the surface 2a of the tool base 2, the above-described effects can be obtained more reliably.
Specifically, when the average thickness of the hard coating layer 3 as a whole is less than 2 μm, each layer 11, 12 of the hard coating layer 3 composed of four or more first and second composite nitride layers 11, 12. The thickness of the thin film becomes thin, and crystals may not grow sufficiently in the thinned layer, or internal stress may increase, and the above-described effects may not be sufficiently obtained.
When the average thickness of the hard coating layer 3 as a whole exceeds 5 μm, the hard coating layer 3 is easily peeled from the surface 2a of the tool base 2 in a wide range, and this peeling occurs to cause the tool. When the surface 2a of the base body 2 is exposed to the outside, there is a possibility that the wear is likely to proceed remarkably from the exposed portion.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the hard coating layer 3 is formed by alternately laminating the first and second composite nitride layers 11 and 12 in total, but the present invention is not limited to this. That is, the hard coating layer 3 may be formed by alternately stacking a total of five or more first and second composite nitride layers 11 and 12 on the surface 2 a of the tool base 2.

  In the above-described embodiment, the outermost layer of the hard coating layer 3 is the second composite nitride layer 12. However, the outermost layer is not limited to this, and the outermost layer is the first composite layer. The nitride layer 11 may be used. That is, the total (total number of stacked layers) of the layers 11 and 12 constituting the hard coating layer 3 is not limited to the even number described above, and may be an odd number. However, when the outermost layer of the hard coating layer 3 is the second composite nitride layer 12 as in the above-described embodiment, the hard coating layer 3 adheres more to the work material such as carbon steel. This is preferable because wear and peeling of the hard coating layer 3 are remarkably suppressed.

  Further, apart from the hard coating layer 3, on the outside of the hard coating layer 3 in the layer thickness direction (vertical direction in FIG. 1), for example, a layer thickness thinner than the first and second composite nitride layers 11, 12. A colored layer (decorative layer) for appearance decoration may be provided.

  Moreover, in the above-mentioned embodiment, although the drill was used as the cutting tool 1, it is not limited to this. That is, the cutting tool 1 may be, for example, an end mill, a cutting tool or the like other than a drill, or a cutting insert (detachable) mounted on a holder (tool body) in a cutting edge exchangeable cutting tool such as a milling cutter. It may be a cemented carbide chip having a cutting edge.

  In addition, in the range which does not deviate from the meaning of this invention, you may combine each structure (component) demonstrated by the above-mentioned embodiment, a modified example, a note, etc., addition of a structure, omission, substitution, others It can be changed. Further, the present invention is not limited by the above-described embodiments, and is limited only by the scope of the claims.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to this embodiment.

[Tool life confirmation test]
As an example of the present invention, the drill (cutting tool 1) described in the above-described embodiment was produced.
Specifically, as the tool base 2, Mitsubishi Materials Corporation model number: MWE0600MA (diameter φ6 mm) was prepared. Then, using the arc ion plating apparatus, the tool base 2 made of tungsten carbide base cemented carbide is disposed in the furnace, and the furnace is heated to a temperature of about 500 ° C. by a heating means such as a heater. First, arc discharge is generated under the condition of current: 100 A between the cathode electrode (evaporation source) on which an Al—Ti alloy having a predetermined composition is set and the anode electrode, and at the same time, nitrogen gas is used as a reaction gas in the furnace. (N ₂ ) is introduced to form a reaction atmosphere at a pressure of 3.5 Pa, a bias voltage of −30 V is applied to the tool base 2, and a second layer made of an (Al, Ti) N layer is formed on the surface 2 a of the tool base 2. 1 composite nitride layer 11 was formed by vapor deposition.

  Next, an arc discharge is generated under the condition of current: 100 A between the cathode electrode (evaporation source) on which the Al—Cr alloy having a predetermined composition is set and the anode electrode, and the other conditions are the same as above. A second composite nitride layer 12 made of an (Al, Cr) N layer was formed on the first composite nitride layer 11 by vapor deposition.

Next, a new first composite nitride layer 11 was formed by vapor deposition on the second composite nitride layer 12 under the same conditions as those for the first composite nitride layer 11 described above.
Next, a new second composite nitride layer 12 was formed by vapor deposition on the new first composite nitride layer 11 under the same conditions as those for the second composite nitride layer 12 described above.
In this way, a hard coating layer 3 was formed on the surface 2a of the tool base 2 by laminating a total of four (Al, Ti) N layers and (Al, Cr) N layers.

  Moreover, about the average layer thickness of each layer 11 and 12 which comprises the hard coating layer 3, while controlling by the operating time of an apparatus, all the target thickness of each layer 11 and 12 shall be 1 micrometer, and the hard coating layer 3 whole The target thickness was set to 4 μm. The hard coating layer 3 thus produced had a layer thickness in the range of 4 to 4.3 μm.

On the other hand, as a comparative example, the tool base 2 is made of Mitsubishi Materials Corporation, model: MWE0600MA (diameter φ6 mm), and the surface 2a of the tool base 2 made of a tungsten carbide base cemented carbide is used. A drill having a single hard coating layer having the same composition as the (Al, Ti) N layer was prepared.
Specifically, a cathode electrode (evaporation source) in which an Al—Ti alloy having a predetermined composition is set in a state in which the tool base 2 is disposed in a furnace and heated in the same manner as described above using the arc ion plating apparatus described above. ) And the anode electrode, arc discharge is generated under the condition of current: 100 A, and simultaneously, nitrogen gas is introduced into the furnace as a reaction gas to form a reaction atmosphere of pressure: 4 Pa, and the tool substrate 2 has a bias voltage. : −50 V was applied to form a single hard coating layer consisting of an (Al, Ti) N layer on the surface 2a of the tool base 2 by vapor deposition.
The target thickness of the (Al, Ti) N layer was 4 μm (that is, the target thickness of the entire hard coating layer was 4 μm).

  And using each drill of these Examples and comparative examples, a plurality of work materials which consist of various materials were cut, respectively, and performance and tool life were checked. As for cutting conditions, a vertical machining center PCV40 manufactured by Osaka Kiko Co., Ltd., cutting speed (vc): 80 m / min, feed per rotation (fr): 0.2 mm / rev, drilling length (ld): 19 mm, cutting fluid (external oiling): a chlorine-free emulsion. The results are shown in Table 1.

As shown in Table 1, in the case where carbon steel (S50C) was used as the work material, it was confirmed that the tool life was extended twice or more as compared with the comparative example. For S50C, cutting with a small-diameter drill and high-speed cutting were also tested, and as a result, the tool life of each example was extended compared to the comparative example. Moreover, when using various materials other than carbon steel as a work material, it turned out that the tool life equivalent to an Example is ensured with an Example.
As described above, according to the example of the present invention, it is found that the tool life can be remarkably extended particularly when carbon steel is used as the work material while ensuring the same performance (machining accuracy) as the comparative example. It was.

DESCRIPTION OF SYMBOLS 1 Cutting tool 2 Tool base body 2a Surface 3 Hard coating layer 11 1st composite nitride layer 12 2nd composite nitride layer

Claims (3)

A total of four or more first composite nitride layers and second composite nitride layers are alternately formed as hard coating layers on the surface of the tool base made of tungsten carbide based cemented carbide.
The first composite nitride layer is formed directly on at least the surface of the tool base and has an average layer thickness of 0.5 to 1.25 μm;
Composition _{formula: (Al 1-X Ti X} ) N
In the case of the above, it comprises a composite nitride layer of Al and Ti having an average composition satisfying 0.3 ≦ X ≦ 0.7 (where X value is an atomic ratio),
The second composite nitride layer has an average layer thickness of 0.5 to 1.25 μm,
Composition formula: (Al _1-a Cr _a ) N
A cutting tool comprising a composite nitride layer of Al and Cr having an average composition satisfying 0.2 ≦ a ≦ 0.6 (where a value is an atomic ratio). The cutting tool according to claim 1,
A cutting tool, wherein the outermost layer of the hard coating layer is the second composite nitride layer. The cutting tool according to claim 1 or 2,
The cutting tool, wherein the average thickness of the hard coating layer as a whole is 2 to 5 µm.

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