JP2021142610A - Cutting tool - Google Patents

Abstract

To provide a cutting tool that can suppress peeling off and horizontal crack of a hard coating during laser-peening processing, and apply high compressive residual stress to the hard coating and a tool base body, which can improve defect resistance of a cutting blade.SOLUTION: A cutting tool comprises a tool base body 1 made of sintered alloy, a hard coating 2 and a cutting blade 3. In the hard coating 2, thicknesses of the whole thereof are 1 μm or more and 30 μm or less, and the hard coating 2 has titanium carbonitride layer 2a whose thickness is 1 μm or more and 10 μm or less. In the titanium carbonitride layer 2a, when a composition of at least a mostfront layer of the titanium carbonitride layer 2a is represented by a composition formula: Ti(CXN1-X), an X value which is an atom ratio is 0.4 or more and 0.6 or less. Residual stress of the mostfront layer of a cutting blade 3 portion and a portion adjacent to the cutting blade 3, in the titanium carbonitride layer 2a, is -1.5 GPa or less, and residual stress of the cutting blade 3 portion and the portion adjacent to the cutting blade 3, in the mostfront layer of the tool base body 1, is -2.0 GPa or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to a cutting tool such as a cemented carbide tool with a hard coating having a titanium carbonitride layer formed and having excellent fracture resistance.

In a cutting tool in which a hard coating is coated on a tool base made of cemented carbide, compressive residual stress is applied to the hard coating near the cutting edge and the surface of the tool base as one of the means for improving the fracture resistance of the cutting edge. The method of granting is known. For example, in Patent Document 1, the residual stress is controlled by the impact force generated by colliding a submillimeter-order steel ball or the like with the tool surface by shot peening.

Japanese Unexamined Patent Publication No. 6-108258

In the method of Patent Document 1, the compressive residual stress of the hard phase of the hard coating or the surface layer of the tool substrate can be increased by increasing the projection pressure of the medium. However, there is a problem that the hard film is peeled off or cracked due to the direct impact given by the media, and the compressive residual stress cannot be stably applied. According to Patent Document 1, the maximum value at which compressive residual stress can be stably applied by shot peening is described as about -200 MPa for a hard coating (TiC) and about -800 MPa for a tool substrate (WC) (minus is compression). side).

Laser peening is known as a method other than shot peening in which compressive residual stress is applied to a metal. Laser peening is a method of irradiating a work with a short pulse laser and instantaneously removing surface elements in a very short time to give an impact to the lower layer due to a mechanical reaction when it is scattered by fine particles or plasma. be. In laser peening, it is possible to apply a larger compressive residual stress than the shot peening process while suppressing damage to the work surface.

However, when laser peening is actually applied to a cutting tool with a hard coating, the coating is peeled off or horizontal due to the indirect effect that the hard coating cannot follow the instantaneous plastic deformation of the tool substrate caused by the laser impact. There was a crack. As a result, the hard coating is lost or reduced (thinned), resulting in reduced wear resistance (it is not a vertical crack, so it does not become a starting point for cutting edge defects during cutting), or due to cracks. Since the residual stress is released, it has been a problem that a large compressive residual stress cannot be stably applied.
The horizontal crack is a peeling crack along the surface direction of the surface of the tool substrate, and the vertical crack is a crack that divides the hard coating or the surface layer of the tool substrate.

In view of the above circumstances, the present invention can suppress peeling and horizontal cracking of the hard coating during the laser peening treatment, and can apply a high compressive residual stress to the hard coating and the tool substrate, whereby the fracture resistance of the cutting edge can be suppressed. One of the purposes is to provide a cutting tool that can improve the stress.

One aspect of the cutting tool of the present invention is a tool base made of a sintered alloy, a hard coating formed on the surface of the tool base, and the hard coating formed on the ridgeline portion of the tool base. The hard coating has a total thickness of 1 μm or more and 30 μm or less, and the hard coating has a titanium nitride layer having a thickness of 1 μm or more and 10 μm or less. When the composition of at least the outermost layer of the titanium nitride layer is _{represented by the composition formula Ti (C X} N _1-X ), the titanium nitride layer has an X value which is an atomic ratio of 0. The residual stress of the outermost layer of the titanium nitride layer of 4 or more and 0.6 or less, the cutting edge portion and the portion adjacent to the cutting edge is −1.5 GPa or less, and the surface layer of the tool substrate. Of these, the residual stress of the cutting edge portion and the portion adjacent to the cutting edge is −2.0 GPa or less.

As a result of diligent research on the relationship between the hard coating and the laser peening technology, the inventor of the present application has an X value of 0.4 to 0 when the _{titanium nitride layer is represented by the composition formula Ti (C X} N _1-X). The titanium nitride layer can follow the plastic deformation during laser peening when it has the outermost layer satisfying .6, that is, when the titanium nitride layer having a higher nitrogen atom ratio than the conventional product is present in the hard coating. I found. As a result, when the laser peening treatment is applied to the vicinity of the cutting edge, the titanium nitride layer is as large as -1.5 GPa or less and the surface layer of the tool base is as large as -2.0 GPa or less while leaving a hard coating on the surface of the tool base. It has become possible to apply compressive residual stress.

Specifically, when the X value is smaller than 0.4, the titanium nitride layer is easily ablated by laser irradiation, and the titanium nitride layer disappears or is reduced (thinned), resulting in a hard coating. Abrasion resistance may decrease.
If the X value exceeds 0.6, the titanium nitride layer cannot follow the momentary plastic deformation of the tool substrate during laser irradiation, causing peeling of the hard coating and horizontal cracks, resulting in the expected compressive residual stress. May not be granted.

According to the present invention, peeling of a hard coating and horizontal cracks during laser peening treatment can be suppressed, and the titanium nitride layer can be stably retained even after laser irradiation to increase the film thickness of the titanium nitride layer. Can be secured. Laser peening can stably apply high compressive residual stress to the hard coating and the tool substrate, thereby improving the fracture resistance of the cutting edge.

When the film thickness of the titanium carbonitride layer is 1 μm or more, the wear resistance of the hard coating is stably enhanced. Further, when the film thickness of the titanium carbonitride layer is 10 μm or less, the chipping resistance of the cutting edge is well maintained.

In the cutting tool, the titanium nitride layer is the first titanium nitride layer satisfying the X value of 0.4 or more and 0.6 or less when represented by _{the composition formula Ti (C X} N _1-X). The titanium nitride layer may be composed of a single layer of the first titanium nitride layer.

In this case, the structure of the titanium nitride layer can be simplified and the manufacturing of a cutting tool becomes easy while the above-mentioned excellent effects can be obtained by the titanium nitride layer.

In the cutting tool, the titanium nitride layer is the first titanium nitride layer satisfying the X value of 0.4 or more and 0.6 or less when represented by _{the composition formula Ti (C X} N _1-X). The first titanium nitride layer is provided with a second titanium nitride layer that satisfies the X value of 0.6 or more and 0.8 or less and overlaps with the first titanium nitride layer in the film thickness direction. Is located on the outermost surface layer of the titanium nitride layer, has a film thickness of 1 μm or more, and the ratio of the film thickness of the first titanium nitride layer to the total film thickness of the titanium nitride layer is 25%. It may be the above.

For the purpose of suppressing peeling of the hard coating and horizontal cracks during the laser peening treatment, excellent effects can be obtained even if the titanium nitride layer is a single layer containing only the first titanium nitride layer (N-rich TiCN layer). However, as in the above configuration of the present invention, the first titanium nitride layer having high laser impact resistance is arranged in the upper layer, and the second titanium nitride layer (N-pore TiCN layer) having high wear resistance is placed in the lower layer. By adopting the arranged two-layer (multi-layer) structure, the wear resistance of the entire titanium nitride layer is further improved. The titanium nitride layer may be composed of three or more layers.

Further, by setting the film thickness of the first titanium nitride layer to 1 μm or more and setting the ratio of the film thickness of the first titanium nitride layer to the total film thickness of the titanium carbonitride layer to 25% or more, the carbon by laser irradiation is used. The disappearance and loss of the titanium nitride layer can be stably suppressed. The titanium nitride layer can be stably retained even after laser irradiation, and a large film thickness of the titanium nitride layer can be secured. Further, by setting the above ratio to 25% or more, it is easier for the titanium nitride layer to follow the momentary plastic deformation of the tool substrate at the time of laser irradiation.

The cutting tool is provided with a rake face connected to the cutting edge, and the portion adjacent to the cutting edge is preferably in a range of at least 200 μm from the cutting edge in the rake face.

In general, a cutting tool is often judged to have reached the end of its tool life when it is worn to a range of 200 μm from the cutting edge (at the unused initial position) on the rake face by cutting. According to the above configuration of the present invention, the fracture resistance in the vicinity of the cutting edge can be stably increased until the tool life is reached.

In the cutting tool, it is preferable that the titanium nitride layer is arranged at least in a portion connected to a part of the cutting edge and the part of the rake face.

In this case, by arranging the titanium nitride layer in the vicinity of the cutting edge where the fracture resistance is particularly desired to be improved, the range of laser peening processing can be kept small to improve the productivity of the cutting tool, and the above-mentioned effects can be obtained. Obtainable.

In the cutting tool, the cutting edge has a convex curved corner blade portion and a linear straight blade portion connected to the corner blade portion, and the straight blade portion is planned to be at a cutting boundary position. It is preferable that the titanium carbonitide layer is arranged at least in a portion of the cutting edge that is connected to the planned boundary portion and the rake face.

In this case, by arranging the titanium nitride layer in the vicinity of the planned boundary portion, which is particularly necessary to improve the fracture resistance, in the vicinity of the cutting edge, the range of laser peening processing can be kept small and the productivity of the cutting tool can be improved. The above-mentioned effects can be obtained.

In the cutting tool, the titanium nitride layer has an X value of 0.5 or more and 0.6 or less when _{the composition of the outermost layer is represented by the composition formula Ti (C X} N _1-X). The residual stress of the outermost layer of the titanium nitride layer of the cutting edge portion and the portion adjacent to the cutting edge is −2.0 GPa or less, and the cutting edge portion and the cutting edge portion of the surface layer of the tool substrate and the above. The residual stress of the portion adjacent to the cutting edge is preferably −2.5 GPa or less.

In this case, when laser peening treatment is applied to the vicinity of the cutting edge, ablation processing, peeling, horizontal cracks, etc. of the titanium nitride layer can be suppressed more stably, and a hard coating is stably left on the surface of the tool substrate. On the other hand, it is possible to apply a larger compressive residual stress of −2.0 GPa or less to the titanium nitride layer and −2.5 GPa or less to the surface layer of the tool substrate.

In the cutting tool, when the titanium nitride layer is represented by the composition formula Ti (C _X N _1-X ), the X value changes from the outermost layer toward the tool substrate in the film thickness direction. Is preferable.

In this case, the titanium carbonitride layer can be made into, for example, a gradation layer by changing the magnitude of the X value of the composition formula Ti (C _X N _{1-X) in the film thickness direction.} The gradation layer is a layer in which the ratio of the atomic ratios of C and N of the titanium carbonitride layer gradually changes in the film thickness direction. According to the above configuration, the titanium nitride layer can flexibly meet the demands of various cutting tools while obtaining the above-mentioned effects.

According to the cutting tool of one aspect of the present invention, peeling and horizontal cracking of the hard coating during the laser peening process can be suppressed, and high compressive residual stress can be applied to the hard coating and the tool substrate, whereby the cutting edge can be obtained. Fracture resistance can be improved.

FIG. 1 is a perspective view showing a cutting tool of the present embodiment. FIG. 2 is an enlarged cross-sectional view showing the vicinity of the cutting edge of the cutting tool of the present embodiment. FIG. 3 shows the X value of the composition formula Ti (C _X N _1-X ) of the titanium nitride layer, and the residual stresses of the titanium nitride layer (TiCN) and the surface layer (WC) of the tool substrate after the laser peening treatment. It is a graph which shows the relationship of. FIG. 4 is a graph showing the relationship between the X value of the composition formula Ti (C _X N _1-X ) of the titanium carbonitride layer and the film thickness of the titanium carbonitride layer after the laser peening treatment. FIG. 5 is an enlarged SEM image showing a cross section in the vicinity of the cutting edge of the cutting tool according to the embodiment of the present invention after the laser peening process. FIG. 6 is an enlarged SEM image showing a cross section in the vicinity of the cutting edge of the cutting tool of the comparative example after the laser peening process. FIG. 7 is a graph showing the relationship between the film thickness of the first titanium nitride layer (N-rich TiCN layer) and the film residual ratio of the entire titanium nitride layer after the laser peening treatment. FIG. 8 shows the ratio (X-axis) of the film thickness of the first titanium nitride layer (N-rich TiCN layer) to the total film thickness of the titanium nitride layer, and the film of the entire titanium nitride layer after the laser peening treatment. It is a graph which shows the relationship with the residual rate (Y axis).

A cutting tool 10 according to an embodiment of the present invention and a method for manufacturing the cutting tool 10 will be described with reference to the drawings. The cutting tool 10 of this embodiment is a cutting insert. The cutting tool 10 of the present embodiment is used, for example, for a cutting edge replaceable cutting tool that turns a work material.

As shown in FIG. 1, the cutting tool 10 of the present embodiment has a plate shape. Specifically, the cutting tool 10 has a polygonal plate shape, and in the illustrated example, it has a quadrangular plate shape. The cutting tool 10 may have a polygonal plate shape, a disk shape, or the like other than the quadrangular plate shape.

In the present embodiment, the direction in which the central axis C of the cutting tool 10 extends, that is, the direction parallel to the central axis C is referred to as an axial direction. In the plan view of the cutting tool 10, the central axis C is located at the center of the cutting tool 10. The central axis C extends along the thickness direction of the cutting tool 10.
The direction orthogonal to the central axis C is called the radial direction. Of the radial directions, the direction closer to the central axis C is called the radial inner side, and the direction away from the central axis C is called the radial outer side.
The direction of orbiting around the central axis C is called the circumferential direction.

As shown in FIG. 2, the cutting tool 10 of the present embodiment includes a tool base 1 made of a sintered alloy, a hard coating 2 arranged on the surface (outer surface) of the tool base 1, and a ridgeline portion of the tool base 1. A cutting edge 3 including a portion of the hard coating 2 formed on the ridge line portion is provided. That is, the cutting tool 10 of the present embodiment is a cutting insert in which a hard coating 2 is coated on a tool base 1.
As shown in FIG. 1, the cutting tool 10 includes a pair of plate surfaces 10a and 10b, an outer peripheral surface 10c, and a through hole 10d.

The pair of plate surfaces 10a and 10b have a polygonal shape and face the axial direction of the central axis C. In the present embodiment, the pair of plate surfaces 10a and 10b have a quadrangular shape, respectively. The pair of plate surfaces 10a and 10b has one plate surface 10a and the other plate surface 10b. One plate surface 10a and the other plate surface 10b are arranged apart from each other in the axial direction and face opposite to each other in the axial direction.

In the present embodiment, the direction from the other plate surface 10b to one plate surface 10a is referred to as one side in the axial direction, and the direction from one plate surface 10a to the other plate surface 10b is the axial direction and the other. Called the side.
Of the pair of plate surfaces 10a and 10b, at least one plate surface 10a has a part (corner portion or the like) of the plate surface 10a facing a work material (not shown) during cutting.

Of the pair of plate surfaces 10a and 10b, at least one plate surface 10a has a rake surface 5 connected to the cutting edge 3. That is, the cutting tool 10 includes a rake face 5. The rake face 5 constitutes at least a part of the plate surface 10a. In the present embodiment, the rake face 5 is arranged at least two corners of the four corners located on the peripheral edge of the plate surface 10a. The two corner portions are arranged at positions that are 180 ° rotationally symmetric with each other about the central axis C.

As shown in FIG. 2, the rake face 5 has a land portion 5a and an inclined portion 5b.
The land portion 5a is a portion of the rake face 5 that is connected to the cutting edge 3. The land portion 5a is arranged inside the cutting edge 3 in the radial direction. In the present embodiment, the land portion 5a is an inclined surface that inclines toward the other side in the axial direction as it goes inward in the radial direction from the cutting edge 3. The land portion 5a may have a flat shape extending in a direction perpendicular to the central axis C.

The inclined portion 5b is a portion of the rake face 5 located inside the land portion 5a in the radial direction. The inclined portion 5b is connected to the radial inner end portion of the land portion 5a. The inclined portion 5b is an inclined surface that inclines toward the other side in the axial direction as it goes inward in the radial direction from the land portion 5a. The amount of displacement in the axial direction per unit length along the radial direction of the inclined portion 5b is larger than the amount of displacement in the axial direction per unit length along the radial direction of the land portion 5a. That is, the inclination of the inclined portion 5b with respect to the virtual plane (not shown) perpendicular to the central axis C is larger than the inclination of the land portion 5a with respect to the virtual plane.

As shown in FIG. 1, the outer peripheral surface 10c is connected to a pair of plate surfaces 10a and 10b and faces outward in the radial direction. Both ends of the outer peripheral surface 10c in the axial direction are connected to a pair of plate surfaces 10a and 10b. Specifically, one end of the outer peripheral surface 10c on one side in the axial direction is connected to one plate surface 10a. The end of the outer peripheral surface 10c on the other side in the axial direction is connected to the other plate surface 10b. The outer peripheral surface 10c extends over the entire circumferential direction of the cutting tool 10.

The outer peripheral surface 10c has a flank 6 connected to the cutting edge 3. That is, the cutting tool 10 includes a flank 6. The flank 6 constitutes at least a part of the outer peripheral surface 10c. The flank 6 is arranged on a portion of the outer peripheral surface 10c adjacent to each rake surface 5. In the present embodiment, the flank 6 is arranged at least two corners of the four corners protruding outward in the radial direction on the outer peripheral surface 10c. The two corner portions are arranged at positions that are 180 ° rotationally symmetric with each other about the central axis C.

The through hole 10d penetrates the cutting tool 10 in the axial direction. The through hole 10d opens in a pair of plate surfaces 10a and 10b and extends in the axial direction. The central axis of the through hole 10d is arranged coaxially with the central axis C. In the illustrated example, the through hole 10d has a circular hole shape. For example, a clamp screw (not shown) or the like is inserted into the through hole 10d.

The cutting edge 3 is formed at a ridge line portion where the rake face 5 and the flank surface 6 are connected, that is, an intersecting ridge line portion between the rake face 5 and the flank surface 6. In the present embodiment, the cutting edge 3 is arranged at at least two corner portions of the four corner portions located on the peripheral edge portion of the plate surface 10a. As shown in FIG. 2, in the present embodiment, the cutting edge 3 has a round honing. The cutting edge 3 may have chamfer honing.

As shown in FIG. 1, the cutting edge 3 has a corner edge portion 3a and a straight edge portion 3b. The corner blade portion 3a has a convex curved shape that protrudes outward in the radial direction. The straight blade portion 3b is linear and is connected to the corner blade portion 3a. In the present embodiment, a pair of straight blade portions 3b are connected to both ends of the corner blade portion 3a in the blade length direction. That is, a pair of straight blade portions 3b is provided. The corner blades 3a and the pair of straight blades 3b are substantially V-shaped as a whole when viewed from the axial direction. The blade length direction is a direction in which the cutting edge 3 extends, and specifically, a direction in which the blade portions 3a and 3b of the cutting edge 3 extend.

Although not particularly shown, the straight blade portion 3b has a planned boundary portion scheduled at a cutting boundary position when cutting a work material. By cutting the work material with the cutting tool 10, boundary wear (boundary) is preferentially applied to the surface (outer surface) of the cutting tool 10 in the vicinity of the planned boundary portion of the cutting edge 3 over the portion other than the vicinity of the planned boundary portion. Damage) occurs.

As shown in FIG. 2, the cutting edge 3 is composed of a ridge line portion (crossed ridge line portion) of the tool substrate 1 and a portion of the hard coating 2 coated on the ridge line portion.

As shown in FIG. 1, the tool base 1 has the same shape as the cutting tool 10 described above. The tool substrate 1 has a carbide having a carbide of a group 4a, 5a, 6a metal in the periodic table, a nitride, and at least one hard phase in these mutual solid solutions, and a Ni, Co or Ni—Co alloy. It is made of bond metal. The tool base 1 is composed mainly of the hard phase and a Ni, Co or Ni—Co alloy. In this embodiment, the tool base 1 is made of a WC-based cemented carbide. The tool base 1 may be made of a cermet such as a TiC group or a Ti (C, N) group.

By performing the laser peening treatment described later, the residual stress of the cutting edge 3 portion and the portion adjacent to the cutting edge 3 in the surface layer of the tool substrate 1 is set to -2.0 GPa or less, and in the present embodiment, it is -2.5 GPa. It is said to be as follows. Specifically, in FIGS. 1 and 2, the cutting tool 10 after laser irradiation has a residual stress in the range A corresponding to the cutting edge 3 portion and the portion adjacent to the cutting edge 3 in the surface layer of the tool substrate 1. It is 2.0 GPa or less, and in this embodiment, it is −2.5 GPa or less.
The “surface layer of the tool base 1” in the present embodiment refers to a surface layer portion of the tool base 1 that is at least 1 μm from the surface (outer surface) of the tool base 1.

Further, the above-mentioned "range A corresponding to the cutting edge 3 portion and the portion adjacent to the cutting edge 3" is a portion irradiated with the short pulse laser in the laser peening step described later, and thus is paraphrased as an "irradiating portion". May be good.
Further, in the present embodiment, the above-mentioned "portion adjacent to the cutting edge 3" is a range A of at least 200 μm from the cutting edge 3 in the rake face 5. The "portion adjacent to the cutting edge 3" is preferably a range A of the rake face 5 within 500 μm from the cutting edge 3.

As shown in FIG. 2, the hard coating film 2 is formed on at least a part of the surface (outer surface) of the tool substrate 1 by a chemical vapor deposition method or a physical vapor deposition method. The hard coating 2 is arranged on the surface of the tool substrate 1 in a region including at least the cutting edge 3. In this embodiment, the hard coating 2 is arranged on at least the cutting edge 3, the rake face 5, and the flank surface 6. The hard coating film 2 may be formed on the entire outer surface of the tool substrate 1.

The overall film thickness of the hard coating 2 is 1 μm or more and 30 μm or less. The hard coating 2 is composed of a single layer or a plurality of layers. In the present embodiment, the hard coating 2 is composed of a plurality of layers laminated on the surface of the tool substrate 1. The hard coating 2 has a first layer 2a located on the surface of the tool substrate 1 and a second layer 2b located on the first layer 2a. The hard coating 2 may have a third layer (not shown) located on the second layer 2b. Further, the hard coating 2 may be composed of four or more layers. Of the plurality of layers of the hard coating 2, the thickest layer is the first layer 2a. When the hard coating 2 is a single layer, the hard coating 2 has a first layer 2a. That is, the hard coating 2 has at least the first layer 2a.

The first layer 2a is a titanium nitride (TiCN) layer. The film thickness of the titanium carbonitride layer 2a is 1 μm or more and 10 μm or less. The titanium nitride layer 2a is arranged directly on the surface of the tool substrate 1 or indirectly with an intermediate layer (not shown) interposed therebetween. The titanium nitride layer 2a is formed by, for example, a chemical vapor deposition method (CVD method).

The titanium nitride layer 2a has an X value which is an atomic ratio when the composition of at least the outermost layer, that is, the layer including the outermost surface of the titanium nitride layer 2a is _{represented by the composition formula Ti (C X} N _1-X). Is 0.4 or more and 0.6 or less, and in the present embodiment, the X value is 0.5 or more and 0.6 or less.
The "outermost surface layer of the titanium nitride layer 2a" in the present embodiment refers to a surface layer portion of the titanium nitride layer 2a at least 1 μm from the outermost surface of the titanium nitride layer 2a in the film thickness direction.

The titanium nitride layer 2a has a first titanium nitride layer. The first titanium nitride layer satisfies an X value of 0.4 or more and 0.6 or less when represented by the composition formula Ti (C _X N _1-X). Since the first titanium nitride layer has a larger proportion of N than the titanium carbonitride layer used in conventional cutting tools, it may be paraphrased as an N-rich TiCN layer. In the present embodiment, the titanium nitride layer 2a is composed of a single layer of the first titanium nitride layer. Therefore, the titanium nitride layer 2a may be rephrased as the first titanium nitride layer 2a.

By performing the laser peening treatment described later, the residual stress of the outermost layer of the cutting edge 3 portion and the portion adjacent to the cutting edge 3 of the titanium nitride layer 2a is set to −1.5 GPa or less, and in the present embodiment, it is −. It is set to 2.0 GPa or less. Specifically, the cutting tool 10 after laser irradiation has a range A (that is, an irradiation portion) corresponding to the cutting edge 3 portion and the portion adjacent to the cutting edge 3 in the titanium nitride layer 2a in FIGS. 1 and 2. The residual stress of the outermost layer is −1.5 GPa or less, and in this embodiment, it is −2.0 GPa or less.
Specifically, the residual stress of the entire portion of the titanium nitride layer 2a located in the range A (the entire area in the film thickness direction including the outermost layer) is −1.5 GPa or less, and in the present embodiment, −2. It is 0 GPa or less.

The titanium nitride layer 2a is arranged at least in a part of the cutting edge 3 in the blade length direction and a part of the rake face 5 connected to the part. Specifically, the titanium nitride layer 2a is arranged at least at a portion connected to the planned boundary portion of the cutting edge 3 (straight blade portion 3b) and the planned boundary portion of the rake face 5. The titanium nitride layer 2a is arranged over at least 1 mm in the blade length direction of the cutting edge 3. In the present embodiment, the titanium nitride layer 2a is arranged at a portion connected to the entire area (overall length) of the cutting edge 3 in the blade length direction and the entire area of the cutting edge 3 of the rake face 5.

The second layer 2b is arranged directly on the surface (outer surface) of the first layer 2a, that is, the titanium nitride layer 2a, or indirectly with an intermediate layer (not shown) interposed therebetween. The second layer 2b contains carbides, nitrides, oxides, borides, carbides of Si, nitrides, oxides of Al, nitrides, and mutual solid solutions thereof of the metals of groups 4a, 5a, and 6a in the periodic table. It is composed of diamond, cubic boron nitride, etc. The second layer 2b is, for example, an Al ₂ O ₃ layer, a TiN layer, or the like. Further, the second layer 2b may be an Al ₂ O ₃ layer, and the third layer (not shown) may be a TiN layer. By _{providing the Al 2} O ₃ layer, the heat resistance and wear resistance of the rake face 5 and the cutting edge 3 are improved. By providing the TiN layer, the appearance of the cutting tool 10 is enhanced, and it is easy to distinguish whether the cutting tool 10 has been used or not, that is, whether it has been used or not. Can be done.

In the example shown in FIG. 2, the portion of the second layer 2b that has been subjected to the laser peening process by the pulse laser described later disappears. The pulse laser is irradiated over the radial outer end portion of the inclined portion 5b, the land portion 5a, and the cutting edge 3. Therefore, the second layer 2b is arranged at a portion other than the radial outer end portion of the inclined portion 5b, the land portion 5a, and the cutting edge 3. The second layer 2b may remain on the radial outer end portion of the inclined portion 5b, the land portion 5a, and the cutting edge 3 after the pulse laser irradiation.

Next, a method of manufacturing the cutting tool 10 will be described.
Although not particularly shown, the method for manufacturing the cutting tool 10 of the present embodiment includes a sintering step, a film forming step, and a laser peeling step.

In the sintering step, the green compact in the shape of the tool base 1, that is, the intermediate compact formed by the green compact in the manufacturing process of the tool base 1 is sintered. In the present embodiment, the green compact is plate-shaped, specifically polygonal plate-shaped.

In the film forming step, the hard coating film 2 is formed on the surface (outer surface) of the sintered tool substrate 1. That is, in the film forming step, a hard coating film 2 having at least the titanium nitride layer 2a is formed on the surface of the tool substrate 1. In the present embodiment, the titanium nitride layer (first layer) 2a is formed directly on the surface of the tool substrate 1 or indirectly with an intermediate layer (not shown) sandwiched therein, and is formed on the titanium nitride layer 2a. , Directly or indirectly across an intermediate layer (not shown _{), a film of Al 2} O ₃ layer (second layer) 2b is formed, and directly or indirectly across an intermediate layer on the _{Al 2} O _{3 layer.} Therefore, a TiN layer (third layer) (not shown) is formed. Note on the surface of the tool substrate 1, of titanium carbonitride layer 2a, may be formed of composed hard film 2 with four or more layers including the Al ₂ O ₃ layer 2b and TiN layer.

In the laser peening step, a pulse laser having a pulse width of 10 ps (picoseconds) or less is irradiated on the hard film 2 to perform a laser peening process. Specifically, in the laser peening step, the rake face 5 and the cutting edge 3 are irradiated with the pulse laser. As shown in FIG. 2, in the present embodiment, the pulse laser is irradiated to the radial outer end portion of the inclined portion 5b, the land portion 5a, and the range A (irradiation portion) extending over the cutting edge 3. The reason why the pulse width of the pulse laser is set to 10 ps or less is that the peak power density of the laser is increased while eliminating the thermal influence on the work, and a high compressive residual stress is applied to the surface layer of the hard coating 2 and the tool substrate 1 by a strong impact. To do.

Specifically, the laser beam is hatch-scanned in the above range A using a galvano scanner (not shown) and an fθ lens. The processing atmosphere at this time is in the atmosphere or in any gas. The arbitrary gas is, for example, an inert gas that suppresses oxidation. The laser beam is a short pulse laser having a pulse width of 10 ps or less, and is adjusted by appropriately changing the pulse width and pulse energy so that ^{the peak power density is 5 TW / cm 2 or more.} The peak power density is a value calculated by pulse energy / (pulse width × spot area). The spot diameter on the surface of the work (cutting tool 10) of the pulse laser is, for example, 30 μm or less. The spots on the work surface of the pulse laser may not overlap each other or may overlap each other.

By the laser peening treatment, the residual stress of the outermost layer of the titanium nitride layer 2a of the cutting edge 3 portion and the portion adjacent to the cutting edge 3 (range A, that is, the irradiation portion; the same applies hereinafter) becomes -1.5 GPa or less, and the tool The residual stress of the cutting edge 3 portion and the portion adjacent to the cutting edge 3 in the surface layer of the substrate 1 is −2.0 GPa or less. In the present embodiment, the residual stress of the outermost surface layer of the irradiation portion of the titanium nitride layer 2a is -2.0 GPa or less, and the residual stress of the irradiation portion of the surface layer of the tool substrate 1 is -2.5 GPa or less. ..

_{By this laser irradiation, the Al 2} O ₃ layer (second layer) 2b and the TiN layer (third layer) (not shown) of the irradiation unit (range A) may or may not be removed. If it is removed, the welding resistance and wear resistance of the hard coating 2 may decrease. Therefore, laser irradiation should be limited to the range A near the cutting edge 3 as shown in FIG. preferable. _{In other words, even if the Al 2} O ₃ layer 2b and the TiN layer are removed in the range A in the vicinity of the cutting edge 3, the influence on the welding resistance and the wear resistance is suppressed to be small.

According to the cutting tool 10 of the present embodiment described above, the following effects are obtained.
That is, as a result of diligent research on the relationship between the hard coating 2 and the laser peening technology, the inventor of the present application has an X value of 0 when the _{titanium nitride layer 2a is represented by the composition formula Ti (C X} N _1-X). When the outermost layer satisfying .4 to 0.6 is provided, that is, when the titanium nitride layer 2a having a higher nitrogen atom ratio than that of the conventional product is present in the hard coating 2, the titanium nitride layer 2a is laser peened. It was discovered that it can follow the plastic deformation of time. As a result, when the laser peening treatment is applied to the vicinity of the cutting edge 3, the titanium nitride layer 2a is −1.5 GPa or less and the surface layer of the tool substrate 1 is −2 while leaving the hard coating 2 on the surface of the tool substrate 1. It has become possible to apply a large compressive residual stress of .0 GPa or less.

Specifically, when the X value is smaller than 0.4, the titanium nitride layer 2a is likely to be ablated by laser irradiation, and the titanium nitride layer 2a disappears or is reduced (thinned). The wear resistance of the hard coating 2 may decrease.
If the X value exceeds 0.6, the titanium nitride layer 2a cannot follow the momentary plastic deformation of the tool substrate 1 during laser irradiation, and the hard coating 2 is peeled off or horizontal cracks occur, which is expected. It may not be possible to apply compressive residual stress.

According to this embodiment, peeling and horizontal cracks of the hard film 2 during the laser peening treatment can be suppressed, and the titanium nitride layer 2a remains stably even after laser irradiation, so that the titanium nitride layer 2a can be formed. A large film thickness can be secured. Laser peening can stably apply high compressive residual stress to the hard coating 2 and the tool substrate 1, thereby improving the fracture resistance of the cutting edge 3.

When the film thickness of the titanium nitride layer 2a is 1 μm or more, the wear resistance of the hard coating 2 is stably enhanced. Further, when the film thickness of the titanium nitride layer 2a is 10 μm or less, the chipping resistance of the cutting edge 3 is maintained well.

Further, in the present embodiment, when the titanium nitride layer 2a is represented by the composition formula Ti (C _X N _1-X ), the first titanium nitride layer satisfying an X value of 0.4 or more and 0.6 or less. Consists of only a single layer.
In this case, the titanium nitride layer 2a can simplify the configuration of the titanium nitride layer 2a while obtaining the above-mentioned excellent effects, and the cutting tool 10 can be easily manufactured.

Further, in the present embodiment, the residual stress of the outermost surface layer of the titanium nitride layer 2a is −1.5 GPa or less in the range A of at least 200 μm from the cutting edge 3 of the rake face 5, and the residual stress of the surface layer of the tool substrate 1 is formed. Is -2.0 GPa or less.
In general, a cutting tool is often judged to have reached the end of its tool life when it is worn to a range of 200 μm from the cutting edge (at the unused initial position) on the rake face by cutting. According to the above configuration of the present embodiment, the fracture resistance in the vicinity of the cutting edge 3 can be stably increased until the tool life is reached.

Further, when the range A (that is, the irradiation portion) is 500 μm or less from the cutting edge 3 of the rake face 5, the hard coating 2 other than the titanium nitride layer (first layer) 2a is subjected to laser peening treatment. Even if the Al ₂ O ₃ layer (second layer) 2b and the TiN layer (third layer) are removed, the welding resistance and wear resistance of the rake face 5 are maintained well.

Further, in the present embodiment, the titanium nitride layer 2a is arranged at least in a portion connected to a part of the cutting edge 3 and the part of the rake face 5.
In this case, by arranging the titanium nitride layer 2a in the vicinity of the cutting edge 3 where the fracture resistance is particularly desired to be improved, the range to be subjected to the laser peening process is suppressed to a small size and the productivity of the cutting tool 10 is increased, while the above-mentioned description is performed. The action effect can be obtained.

Further, in the present embodiment, the titanium nitride layer 2a is arranged at least in a portion connected to the planned boundary portion of the cutting edge 3 and the planned boundary portion of the rake face 5.
In this case, by arranging the titanium nitride layer 2a in the vicinity of the planned boundary portion where it is necessary to particularly improve the fracture resistance among the vicinity of the cutting edge 3, the range of laser peening processing can be suppressed to a small size and the productivity of the cutting tool 10 can be improved. While enhancing, the above-mentioned action and effect can be obtained.

Further, in the present embodiment, the titanium nitride layer 2a has an X value of 0.5 or more and 0.6 or less when _{the composition of the outermost layer thereof is represented by the composition formula Ti (C X} N _1-X). The residual stress of the outermost surface layer of the irradiation portion (range A) of the titanium nitride layer 2a is -2.0 GPa or less, and the residual stress of the irradiation portion (range A) of the surface layer of the tool substrate 1 is -2. It is less than .5 GPa.
In this case, when the laser peening treatment is applied to the vicinity of the cutting edge 3, the ablation processing, peeling, horizontal cracks, etc. of the titanium nitride layer 2a can be suppressed more stably, and the hard coating 2 is stabilized on the surface of the tool substrate 1. It is possible to apply a larger compressive residual stress of −2.0 GPa or less to the titanium nitride layer 2a and −2.5 GPa or less to the surface layer of the tool substrate 1 while retaining the stress.

The present invention is not limited to the above-described embodiment, and the configuration can be changed without departing from the spirit of the present invention, for example, as described below.

In the above-described embodiment, the example in which the titanium nitride layer 2a is composed of a single layer of the first titanium nitride layer has been given, but the present invention is not limited to this.
Although not particularly shown, as a first modification of the above-described embodiment, the titanium nitride layer 2a includes a first titanium nitride layer and a second titanium nitride layer that overlaps the first titanium nitride layer in the film thickness direction. , May have. The first titanium nitride layer satisfies an X value of 0.4 or more and 0.6 or less when represented by the composition formula Ti (C _X N _1-X). The second titanium nitride layer satisfies an X value of 0.6 or more and 0.8 or less when represented by the composition formula Ti (C _X N _1-X). Since the ratio of N in the second titanium nitride layer is smaller than that in the first titanium nitride layer, it may be paraphrased as an N-pore TiCN layer.
In the first modification, the first titanium nitride layer is located on the outermost surface of the titanium carbonitride layer 2a and has a film thickness of 1 μm or more. The ratio of the film thickness of the first titanium nitride layer to the total film thickness of the titanium carbonitride layer 2a is 25% or more.

For the purpose of suppressing peeling and horizontal cracking of the hard coating 2 during the laser peening treatment, even if the titanium nitride layer 2a is a single layer containing only the first titanium nitride layer (N-rich TiCN layer), an excellent effect is obtained. However, as in the first modification described above, the first titanium nitride layer having high laser impact resistance is arranged in the upper layer, and the second titanium nitride layer (N-pore TiCN) having high wear resistance is arranged in the lower layer. By forming a two-layer (multi-layer) structure in which the layers) are arranged, the wear resistance of the titanium nitride layer 2a as a whole is further improved. The titanium nitride layer 2a may be composed of three or more layers.

Further, in the first modification, the film thickness of the first titanium nitride layer is 1 μm or more, and the ratio of the film thickness of the first titanium nitride layer to the total film thickness of the titanium carbonitride layer 2a is 25% or more. Therefore, the disappearance and loss of the titanium nitride layer 2a due to laser irradiation can be stably suppressed. The titanium nitride layer 2a can be stably retained even after laser irradiation, and a large film thickness of the titanium nitride layer 2a can be secured. Further, by setting the above ratio to 25% or more, it is easier for the titanium nitride layer 2a to follow the momentary plastic deformation of the tool substrate 1 at the time of laser irradiation.

Although not particularly shown, as a second modification of the above-described embodiment, when the titanium nitride layer 2a is represented by the composition formula Ti (C _X N _1-X ), the tool substrate 1 is formed from the outermost layer in the film thickness direction. The X value may change toward. For example, when the titanium nitride layer 2a is represented by the composition formula Ti (C _X N _1-X ), the X value may increase from the outermost layer toward the tool substrate 1 in the film thickness direction.
In this case, the titanium carbonitride layer 2a can be made into, for example, a gradation layer by changing the magnitude of the X value of the composition formula Ti (C _X N _{1-X) in the film thickness direction.} The gradation layer is a layer in which the ratio of the atomic ratios of C and N of the titanium carbonitride layer 2a gradually changes in the film thickness direction. According to the above configuration, the titanium nitride layer 2a can flexibly meet the demands of various cutting tools 10 while obtaining the above-mentioned effects.

In the above-described embodiment, an example in which the cutting tool 10 is used for the cutting edge replaceable cutting tool has been given, but the present invention is not limited to this. The cutting tool 10 may be used, for example, in a cutting edge replaceable drill, a cutting edge replaceable end mill, or the like for rolling a work material.
Further, the example in which the cutting tool 10 is a cutting insert has been given, but the present invention is not limited to this. The cutting tool 10 may be, for example, a solid type drill, an end mill, a reamer, or other cutting tool.

In addition, each configuration (component) described in the above-described embodiments, modifications, and notes may be combined as long as it does not deviate from the gist of the present invention. It can be changed. Further, the present invention is not limited to the above-described embodiments, but is limited only to the scope of claims.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to this embodiment.

As each cutting tool of the examples and comparative examples of the present invention, a cutting insert having a JIS standard CNMG120408 shape was prepared. The tool base 1 of each cutting tool is made of WC cemented carbide having a composition of 9.0% by mass of Co. The titanium nitride layer 2a of the hard coating film 2 was formed on the surface of each tool substrate 1 by a CVD method to have a film thickness (average film thickness) of 5 μm. For the titanium nitride layer 2a of each cutting tool, _{the X value when represented by the composition formula Ti (C X} N _1-X ) is as shown in Table 1 below. The titanium nitride layer 2a of each cutting tool is a single layer. _{TiCl 4} , N ₂ , CH ₄ , CH ₃ CN, H _2, etc. were used as the reaction gas, and the X value was changed by controlling the flow rate ratio of each. Then, on the titanium carbonitride layer 2a, an α-Al ₂ O ₃ layer was formed with a film thickness of 2 μm and a TiN layer was formed with a film thickness of 0.2 μm by a CVD method.

Next, a short pulse laser was irradiated from the surface of the hard coating 2 to perform laser peening treatment. The laser conditions were a laser wavelength of 1030 nm, a repetition frequency of 10 kHz, a pulse width of 1 ps, a pulse energy of 0.4 mJ, a beam profile of Gaussian, and a spot diameter of φ30 μm on the work surface. The laser irradiation pattern was made into a regular triangular lattice so that the compressive residual stress was applied isotropically to the work, and the distance between the spot centers was 10 μm. In each sample (cutting tool), the α-Al ₂ O ₃ layer and the TiN layer of the irradiated portion irradiated with the laser were peeled off or ablated.

After measuring the residual stress of the titanium nitride layer 2a and the surface layer of the tool substrate 1 after laser irradiation, observe the cross section of the titanium nitride layer 2a of the laser irradiation part and record the film thickness and the presence or absence of cracks after laser irradiation. bottom. The residual stress of the titanium nitride layer 2a could not be measured for the sample having a thin film thickness of the titanium nitride layer 2a after laser irradiation.

Regarding the calculation of the film thickness and atomic ratio X value of the titanium carbonitide layer 2a, the vertical cross section with respect to the surface of the hard coating 2 and the tool substrate 1 is a scanning electron microscope (SEM), a transmission electron microscope (TEM), and an energy dispersive type. It was measured using X-ray spectroscopy (EDS).
The residual stress was measured by using the X-ray residual stress measuring device manufactured by Pulstec Co., Ltd. and using the cosα method. A Cu tube is used as the X-ray source, and the residual stress is measured using the WC (113) diffraction peak near 2θ = 154 ° and the TiCN (431) diffraction peak near 2θ = 133 °. bottom. Using an X-ray shielding plate, only a width of 0.2 mm was exposed from the cutting edge 3 to the rake face 5 side, and measurement was performed so that the stress value was only the laser peening processing portion.

The criteria for judgment in Table 1 are as follows.
A: The residual stress (TiCN residual stress) of the titanium nitride layer 2a is -2.0 GPa or less, and the residual stress (WC residual stress) of the surface layer of the tool substrate 1 is -2.5 GPa or less.
B: The residual stress (TiCN residual stress) of the titanium nitride layer 2a is -1.5 GPa or less, and the residual stress (WC residual stress) of the surface layer of the tool substrate 1 is -2.0 GPa or less.
C: The residual stress (TiCN residual stress) of the titanium nitride layer 2a is larger than -1.5 GPa, or the residual stress (WC residual stress) of the surface layer of the tool substrate 1 is larger than -2.0 GPa.

Further, FIG. 3 shows the X value of the composition formula Ti (C _X N _1-X ) of the titanium nitride layer 2a, the surface layer of the titanium nitride layer 2a after the laser peening treatment, and the surface layer of the tool substrate 1 based on Table 1. It is a graph which shows the relationship with each residual stress.
As shown in Table 1 and FIG. 3, in Examples 1 to 4 in which the X value was in the range of 0.4 to 0.6, the determination was A or B, and the compressive residual stress was remarkably increased. Among them, Examples 3 and 4 in which the X value is in the range of 0.5 to 0.6 were judged as A, and it was found that the compressive residual stress was particularly remarkably increased.

FIG. 4 shows the relationship between the X value of the composition formula Ti (C _X N _1-X ) of the titanium nitride layer 2a and the film thickness of the titanium nitride layer 2a after the laser peening treatment, based on Table 1. It is a graph.
As shown in FIG. 4, in the range of the X value of 0.4 to 0.6 (Examples 1 to 4), a large film thickness of the titanium nitride layer 2a is secured even after laser irradiation, that is, the film disappears. It was found that the loss was suppressed.

FIG. 5 is an enlarged SEM image showing a cross section in the vicinity of the cutting edge 3 after the laser peening process of the cutting tool 10 of the third embodiment. As shown in FIG. 5, in the third embodiment, the disappearance and loss of the titanium nitride layer 2a are suppressed to be small even after the laser peening treatment, and the titanium nitride layer 2a is not peeled or horizontally cracked.

On the other hand, as shown in Table 1 and FIG. 3, all of Comparative Examples 1 to 7 in which the X value is out of the range of 0.4 to 0.6 are judged as C, and the compressive residual stress is increased to the desired value. I couldn't. Specifically, in Comparative Examples 1 to 3 in which the X value is smaller than 0.4, the metal bonding property of the titanium nitride layer 2a is high, and ablation processing is likely to occur by laser irradiation, so that the coating film is processed and removed. It is thought that it was. Further, in Comparative Examples 4 to 7 in which the X value is larger than 0.6, the covalent bond property of the titanium nitride layer 2a is increased and the toughness of the coating film is lowered, so that the plasticity of the tool substrate 1 at the time of laser irradiation is increased. It is probable that horizontal cracks occurred in the coating because it could not follow the deformation.

FIG. 6 is an enlarged SEM image showing a cross section in the vicinity of the cutting edge 3 after the laser peening process of the cutting tool of Comparative Example 6. As shown in FIG. 6, in Comparative Example 6, a large number of horizontal cracks and peeling (interfacial cracks) occurred in the titanium nitride layer 2a after the laser peening treatment. When such cracks occur, the coating film is reduced and it becomes difficult for compressive residual stress to be applied to the coating film.

Next, a case where the titanium nitride layer 2a of the cutting tool 10 had a two-layer structure was confirmed by a laser peening process.
As each cutting tool 10 of the embodiment of the present invention, a cutting insert having a JIS standard CNMG120408 shape was prepared. The tool base 1 of each cutting tool 10 is made of a WC cemented carbide having a composition of 9.0% by mass of Co. The titanium nitride layer 2a has a two-layer structure, and is formed by a CVD method with a lower second titanium nitride layer (N-pore TiCN layer) on the surface of the tool substrate 1 at each film thickness shown in Table 2 below. , A first titanium nitride layer (N-rich TiCN layer) as an upper layer was formed. The first titanium nitride layer has _{an X value of composition formula Ti (C X} N _1-X ) of 0.58, and the second titanium nitride layer has a composition formula Ti (C _X N _1-X ). The X value was 0.7. Then, on the titanium carbonitride layer 2a, it was formed _{the Al} 2 _{O 3} layer thickness 2 [mu] m, a TiN layer with a thickness of 0.2μm by CVD.

Next, the surface of the hard coating 2 was irradiated with a short pulse laser and subjected to laser peening treatment. The laser conditions were the same as the above-mentioned laser conditions of this example. The method for measuring each film thickness of the titanium carbonitride layer 2a is the same as described above.

Further, FIG. 7 is a graph showing the relationship between the film thickness of the first titanium nitride layer (N-rich TiCN layer) and the film residual ratio of the entire titanium nitride layer 2a after the laser peening treatment, based on Table 2. Is. FIG. 8 shows the ratio (X-axis) of the film thickness of the first titanium nitride layer (N-rich TiCN layer) to the total film thickness of the titanium nitride layer and the carbon after the laser peening treatment, based on Table 2. It is a graph which shows the relationship with the film thickness residual ratio (Y axis) of the whole titanium nitride layer.

As shown in Table 2, FIG. 7 and FIG. 8, the film thickness of the first titanium nitride layer is less than 1 μm, and the ratio of the film thickness of the first titanium nitride layer to the total film thickness of the titanium nitride layer 2a. In Example 5 in which the ratio was less than 25%, the titanium nitride layer 2a tended to be less likely to remain after laser irradiation. As in Examples 6 and 7, the film thickness of the first titanium nitride layer located on the outermost surface of the titanium carbonitride layer 2a is 1 μm or more, and the first carbonitriding occupies the entire film thickness of the titanium carbonitride layer 2a. When the ratio of the film thickness of the titanium layer was 25% or more, the titanium nitride layer 2a remained stable after laser irradiation.

According to the cutting tool of the present invention, peeling and horizontal cracking of the hard coating during the laser peening process can be suppressed, and high compressive residual stress can be applied to the hard coating and the tool substrate, whereby the fracture resistance of the cutting edge can be suppressed. Can be improved. Therefore, it has industrial applicability.

1 ... Tool base, 2 ... Hard coating, 2a ... Titanium nitride layer, 3 ... Cutting edge, 3a ... Corner blade, 3b ... Straight blade, 5 ... Scooping surface, 10 ... Cutting tool, A ... Range

Claims (8)

Tool base made of sintered alloy and
A hard coating placed on the surface of the tool substrate and
A cutting edge formed on the ridgeline portion of the tool substrate and including a portion of the hard coating portion located at the ridgeline portion is provided.
The overall film thickness of the hard coating is 1 μm or more and 30 μm or less.
The hard coating has a titanium carbonitride layer having a film thickness of 1 μm or more and 10 μm or less.
The titanium nitride layer has a composition of at least the outermost layer of the titanium nitride layers.
Composition formula Ti (C _X N _1-X )
When represented by, the X value, which is the atomic ratio, is 0.4 or more and 0.6 or less.
The residual stress of the outermost layer of the titanium nitride layer at the cutting edge portion and the portion adjacent to the cutting edge is −1.5 GPa or less.
The residual stress of the cutting edge portion and the portion adjacent to the cutting edge in the surface layer of the tool substrate is −2.0 GPa or less.
Cutting tools. The titanium nitride layer has a first titanium nitride layer having an X value of 0.4 or more and 0.6 or less when represented by _{the composition formula Ti (C X} N _1-X).
The titanium nitride layer is composed of a single layer of the first titanium nitride layer.
The cutting tool according to claim 1. The titanium nitride layer is represented by the composition formula Ti (C _X N _1-X ).
A first titanium nitride layer satisfying the X value of 0.4 or more and 0.6 or less,
It has a second titanium nitride layer that satisfies the X value of 0.6 or more and 0.8 or less and overlaps with the first titanium nitride layer in the film thickness direction.
The first titanium nitride layer is located on the outermost surface layer of the titanium carbonitride layer and has a film thickness of 1 μm or more.
The ratio of the film thickness of the first titanium nitride layer to the total film thickness of the titanium carbonitride layer is 25% or more.
The cutting tool according to claim 1. With a rake face to connect to the cutting edge
The portion adjacent to the cutting edge is at least 200 μm from the cutting edge in the rake face.
The cutting tool according to any one of claims 1 to 3. The titanium nitride layer is arranged at least in a portion of the cutting edge and a portion of the rake face connected to the portion.
The cutting tool according to claim 4. The cutting edge is
Convex curved corner blade and
It has a linear straight blade portion connected to the corner blade portion, and has.
The straight blade portion has a planned boundary portion scheduled at a cutting boundary position, and has a planned boundary portion.
The titanium nitride layer is arranged at least in a portion of the cutting edge that connects to the planned boundary portion and the rake face.
The cutting tool according to claim 4 or 5. The composition of the outermost layer of the titanium nitride layer is
Composition formula Ti (C _X N _1-X )
When represented by, the X value is 0.5 or more and 0.6 or less.
The residual stress of the outermost layer of the titanium nitride layer at the cutting edge portion and the portion adjacent to the cutting edge is −2.0 GPa or less.
The residual stress of the cutting edge portion and the portion adjacent to the cutting edge in the surface layer of the tool substrate is −2.5 GPa or less.
The cutting tool according to any one of claims 1 to 6. When the titanium nitride layer is represented by the composition formula Ti (C _X N _1-X ), the X value changes from the outermost layer toward the tool substrate in the film thickness direction.
The cutting tool according to any one of claims 1 to 7.

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