阅读说明：本技术 被覆切削工具 (Coated cutting tool ) 是由 城地司 高桥欣也 福岛直幸 于 2020-02-14 设计创作，主要内容包括：本发明提供一种工具寿命较长且加工面品质优良的被覆切削工具,其具备基材与被覆层,被覆切削工具具有至少1个后刀面、至少1个前刀面及连接后刀面和前刀面的被倒圆的珩磨部,被覆层从基材侧依次包含下部层、中间层和上部层,下部层含有一层以上的由特定Ti化合物构成的Ti化合物层,中间层含有α型Al<Sub>2</Sub>O<Sub>3</Sub>,上部层含有特定化合物,被覆层的后刀面侧中的平均厚度为5.0μm以上30.0μm以下,位于从中间层的上部层侧的界面朝向基材侧至1μm为止的距离并与基材和下部层之间的界面平行的第1截面、和位于从上部层的中间层侧的界面朝向其相反侧的界面至1μm为止的距离并与基材和下部层之间的界面平行的第2截面分别满足指定条件,中间层至少在珩磨部中露出。(The present invention provides a coated cutting tool with long tool life and excellent processing surface quality, which comprises a base material and a coating layer, wherein the coated cutting tool comprises at least 1 flank face, at least 1 rake face and a rounded honing part connecting the flank face and the rake face, the coating layer comprises a lower layer, an intermediate layer and an upper layer in sequence from the base material side, the lower layer comprises more than one Ti compound layer composed of specific Ti compounds, the intermediate layer comprises α type Al compound 2 O 3 The upper layer contains a specific compound, the average thickness of the coating layer on the rear blade side is 5.0 [ mu ] m or more and 30.0 [ mu ] m or less, a 1 st cross section parallel to the interface between the base material and the lower layer and located at a distance of 1 [ mu ] m from the interface on the upper layer side of the intermediate layer toward the base material side, and a 2 nd cross section parallel to the interface between the base material and the lower layer and located at a distance of 1 [ mu ] m from the interface on the intermediate layer side of the upper layer toward the interface on the opposite side thereof satisfy predetermined conditions, respectively, and the intermediate layer is exposed at least in the honing portion.)

1. A coated cutting tool in which, in a cutting tool,

the coated cutting tool comprises a base material and a coating layer formed on the base material,

the coated cutting tool has at least 1 flank face, at least 1 rake face, and a rounded honing portion connecting the flank face and the rake face,

the coating layer comprises a lower layer, an intermediate layer and an upper layer in this order from the substrate side,

the lower layer contains one or more Ti compound layers composed of Ti compounds including Ti and at least 1 element selected from the group consisting of C, N, O and B,

the intermediate layer contains α type Al₂O₃，

The upper layer contains a compound represented by the following formula (1):

Ti(C_1-x-yN_xO_y) (1)

wherein x is an atomic ratio of N to the total of C, N and O, y is an atomic ratio of O to the total of C, N and O, and x is 0.15. ltoreq. x.ltoreq.0.65, and y is 0. ltoreq. y.ltoreq.0.20,

the average thickness of the coating layer on the rear blade side is 5.0 [ mu ] m or more and 30.0 [ mu ] m or less,

a 1 st cross section parallel to an interface between the substrate and the lower layer and located at a distance of 1 μm from the interface on the upper layer side of the intermediate layer toward the substrate side satisfies a condition represented by the following formula (i),

RSA≥40 (i)

wherein RSA is a ratio of a cross-sectional area of particles having a misorientation A of 0 degrees or more and less than 10 degrees to a cross-sectional area of particles having a misorientation A of 0 degrees or more and 45 degrees or less in the 1 st cross-section, and the misorientation A is a normal line of the 1 st cross-section and α type Al in the intermediate layer₂O₃The angle formed by the normal line of the (001) plane of the particle of (2) is expressed in degrees,

a 2 nd cross section parallel to the interface between the base material and the lower layer and located at a distance of 1 μm from the interface on the intermediate layer side of the upper layer toward the interface on the opposite side thereof satisfies a condition represented by the following formula (ii),

RSB≥40 (ii)

wherein RSB is a ratio of a cross-sectional area of particles having a misorientation B of 0 degrees or more and less than 10 degrees to a cross-sectional area of particles having a misorientation B of 0 degrees or more and 45 degrees or less in the 2 nd cross-section, and a unit of RSB is an area%, and rsB is an angle formed by a normal line of the 2 nd cross-section and a normal line of a (111) plane of particles of the compound represented by formula (1) in the upper layer, and a unit of rsB is degrees,

the intermediate layer is exposed at least in the honing portion.

2. The coated cutting tool of claim 1,

the intermediate layer is also exposed in an area of the rake face up to 3mm from a boundary with the honing portion.

3. The coated cutting tool of claim 1 or 2,

the upper layer has an average thickness of 1.0 [ mu ] m or more and 6.0 [ mu ] m or less on the flank side.

4. The coated cutting tool according to any one of claims 1 to 3,

the average thickness of the intermediate layer on the flank side is 3.0 μm or more and 15.0 μm or less.

5. The coated cutting tool according to any one of claims 1 to 4,

the lower layer has an average thickness of 3.0 to 15.0 [ mu ] m on the flank side.

6. The coated cutting tool according to any one of claims 1 to 5,

the Ti compound in the Ti compound layer is selected from TiN, TiC, TiCN, TiCNO, TiON and TiB₂At least 1 of the group consisting.

7. The coated cutting tool according to any one of claims 1 to 6,

the base material is hard alloy, metal ceramic, ceramic or cubic boron nitride sintered body.

Technical Field

The present invention relates to a coated cutting tool.

Background

Conventionally, a coated cutting tool in which a coating layer is formed by vapor deposition on the surface of a substrate made of cemented carbide by a chemical vapor deposition method in a total film thickness of 3 to 20 μm has been used for cutting of steel, cast iron, and the like. As the coating layer, for example, a titanium compound or alumina (Al) is known₂O₃) And the like or a multilayer of two or more of them.

Patent document 1 describes a surface-coated cutting tool in which a lower layer made of a titanium compound layer and an aluminum oxide layer (Al) are vapor-deposited on the surface of a tool base made of a tungsten carbide-based cemented carbide₂O₃Layer) as a hard coating layer, wherein the hard coating layer is composed of an aluminum oxide layer (Al)₂O₃Layer) has a (006) plane orientation coefficient TC (006) of 1.8 or more, a ratio I (104)/I (110) of a peak intensity I (104) of a (104) plane to a peak intensity I (110) of a (110) plane is 0.5 to 2.0, and an alumina layer (Al) is formed₂O₃Layer) has an absolute value of residual stress value of 100MPa or less.

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-132717

Disclosure of Invention

In recent years, cutting work has been increasingly carried out with higher feed and deeper feed, and there is a demand for improvement in wear resistance and chipping resistance of cutting tools as compared with conventional cutting tools. In recent years, cutting work such as high-speed cutting of steel, which applies a large load to a coated cutting tool, has been increasing, and under such severe cutting conditions, a crater wear (crater wear) due to the shedding of particles of a coating layer and a defect due to welding have occurred in a conventional coated cutting tool. Thereby causing a problem of shortening the tool life.

In the coated cutting tool, when a cutting material of a workpiece is welded to a portion actually involved in cutting, the machined surface of the workpiece is damaged, and a problem of quality of the machined surface such as cloudiness occurs.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a coated cutting tool exhibiting a long tool life and excellent machining surface quality.

From the above-described viewpoint, the present inventors have conducted extensive studies on the combination of the extension of the tool life of the coated cutting tool and the quality of the machined surface.

Further, there is obtained a finding that a coated cutting tool exhibiting a long tool life and excellent machining surface quality can be obtained by including a lower layer, an intermediate layer, and an upper layer of a specific material in the coating layer of the coated cutting tool, setting RSA described later in the intermediate layer and RSB described later in the upper layer to be within predetermined ranges, setting the average thickness of the coating layer to be within a predetermined range, and exposing the intermediate layer to the honing portion of the coated cutting tool.

Namely, the present invention is as follows.

[1]

A coated cutting tool comprising a base material and a coating layer formed on the base material,

the coated cutting tool has at least 1 flank face, at least 1 rake face, and a rounded honing portion connecting the flank face and the rake face,

the coating layer comprises a lower layer, an intermediate layer and an upper layer in this order from the substrate side,

the lower layer contains one or more Ti compound layers composed of Ti compounds including Ti and at least 1 element selected from the group consisting of C, N, O and B,

the intermediate layer contains α type Al₂O₃，

The upper layer contains a compound represented by the following formula (1):

Ti(C_1-x-yN_xO_y) (1)

(wherein x is the atomic ratio of N to the total of C, N and O, and y is the atomic ratio of O to the total of C, N and O, and satisfies 0.15. ltoreq. x.ltoreq.0.65 and 0. ltoreq. y.ltoreq.0.20.)

The average thickness of the coating layer on the flank side is 5.0 to 30.0 [ mu ] m,

a 1 st cross section parallel to the interface between the substrate and the lower layer and located at a distance of 1 μm from the interface on the upper layer side of the intermediate layer toward the substrate side satisfies a condition represented by the following formula (i),

RSA≥40 (i)

(wherein RSA is the ratio (unit: area%) of the cross-sectional area of the particles having the misorientation A of 0 degrees or more and less than 10 degrees to the cross-sectional area of the particles having the misorientation A of 0 degrees or more and 45 degrees or less in the 1 st cross-section, and the misorientation A is the normal line of the 1 st cross-section and α type Al in the intermediate layer₂O₃Angle (unit: degree) formed by the normal line of the (001) plane of the particle (1). )

A 2 nd cross section parallel to the interface between the base material and the lower layer and located at a distance of 1 μm from the interface on the intermediate layer side of the upper layer toward the interface on the opposite side thereof satisfies a condition represented by the following formula (ii),

RSB≥40 (ii)

(wherein RSB is the ratio (unit: area%) of the cross-sectional area of the particle having the misorientation B of 0 degrees or more and less than 10 degrees to the cross-sectional area of the particle having the misorientation B of 0 degrees or more and 45 degrees or less in the 2 nd cross-section, and the misorientation B is the angle (unit: degrees) formed by the normal line of the 2 nd cross-section and the normal line of the (111) plane of the particle of the compound represented by formula (1) in the upper layer.)

The intermediate layer is exposed at least in the honing portion.

[2]

The coated cutting tool according to [1], wherein the intermediate layer is exposed in a region of the rake face up to 3mm from a boundary with the honed portion.

[3]

The coated cutting tool according to [1] or [2], wherein the upper layer has an average thickness of 1.0 μm or more and 6.0 μm or less on the side of the back cutting edge.

[4]

The coated cutting tool according to any one of [1] to [3], wherein the average thickness of the intermediate layer on the flank side is 3.0 μm or more and 15.0 μm or less.

[5]

The coated cutting tool according to any one of [1] to [4], wherein the average thickness of the lower layer on the side of the back cutting edge is 3.0 μm or more and 15.0 μm or less.

[6]

Such as [1]]To [ 5]]The coated cutting tool according to any one of the preceding claims, wherein the Ti compound in the Ti compound layer is selected from TiN, TiC, TiCN, TiCNO, TiON and TiB₂At least 1 of the group consisting.

[7]

The coated cutting tool according to any one of [1] to [6], wherein the base material is a cemented carbide, a cermet, a ceramic, or a sintered cubic boron nitride.

The present invention can provide a coated cutting tool exhibiting a long tool life and excellent machined surface quality.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of a coated cutting tool according to the present embodiment.

Fig. 2 is a schematic cross-sectional view showing an example of the coated cutting tool according to the present embodiment.

Fig. 3 is a schematic cross-sectional view showing an example of the coated cutting tool according to the present embodiment.

Detailed Description

Hereinafter, a mode for carrying out the present invention (hereinafter, simply referred to as "the present embodiment") will be described in detail with reference to the drawings as necessary, but the present invention is not limited to the present embodiment described below. The present invention can be variously modified within a range not exceeding the gist thereof. It should be noted that positional relationships such as up, down, left, and right in the drawings are based on the positional relationships shown in the drawings unless otherwise specified. The dimensional ratios in the drawings are not limited to the illustrated ratios.

[ coated cutting tool ]

The coated cutting tool of the present embodiment includes a substrate and a coating layer formed on the substrate.

The coated cutting tool includes at least 1 flank face, at least 1 rake face, and a rounded honing portion connecting the flank face and the rake face.

Further, the coating layer comprises a lower layer, an intermediate layer and an upper layer in this order from the substrate side,

the lower layer contains one or more Ti compound layers composed of Ti compound(s) of Ti and at least 1 element selected from the group consisting of C, N, O and B, and the intermediate layer contains α type Al₂O₃The upper layer contains a compound represented by the following formula (1):

Ti(C_1-x-yN_xO_y) (1)

(wherein x is the atomic ratio of N to the total of C, N and O, and y is the atomic ratio of O to the total of C, N and O, and satisfies 0.15. ltoreq. x.ltoreq.0.65 and 0. ltoreq. y.ltoreq.0.20.)

The average thickness of the coating layer on the flank side is 5.0 to 30.0 [ mu ] m,

and a 1 st cross section parallel to the interface between the substrate and the lower layer and located at a distance of 1 μm from the interface on the upper layer side of the intermediate layer toward the substrate side satisfies a condition represented by the following formula (i).

RSA≥40 (i)

(wherein RSA is the ratio (unit: area%) of the cross-sectional area of the particles having the misorientation A of 0 degrees or more and less than 10 degrees to the cross-sectional area of the particles having the misorientation A of 0 degrees or more and 45 degrees or less in the 1 st cross-section, and the misorientation A is the normal line of the 1 st cross-section and α type Al in the intermediate layer₂O₃Angle (unit: degree) of the normal line of the (001) plane of the particle. )

And a 2 nd cross section parallel to the interface between the base material and the lower layer, the 2 nd cross section being located at a distance of 1 μm from the interface on the intermediate layer side of the upper layer toward the interface on the opposite side thereof, and satisfying a condition represented by the following formula (ii).

RSB≥40 (ii)

(wherein RSB is the ratio (unit: area%) of the cross-sectional area of the particle having the misorientation B of 0 degrees or more and less than 10 degrees to the cross-sectional area of the particle having the misorientation B of 0 degrees or more and 45 degrees or less in the 2 nd cross-section, and the misorientation B is the angle (unit: degrees) formed by the normal line of the 2 nd cross-section and the normal line of the (111) plane of the particle of the compound represented by formula (1) in the upper layer.)

The intermediate layer is exposed at least in the honing portion.

The coated cutting tool according to the present embodiment can provide a coated cutting tool exhibiting a long tool life and excellent machining surface quality by having the above-described structure.

The reason why the effect of the coated cutting tool of the present embodiment is obtained is not clear, but is considered as follows. However, the present invention is not limited to the following factors.

The coated cutting tool of the present embodiment is considered to exhibit a long tool life mainly due to the improvement of wear resistance and the improvement of crater wear resistance.

It is considered that in the coated cutting tool of the present embodiment, since the average thickness of the coating layer is 5.0 μm or more, the wear resistance will be improved, and since the average thickness of the coating layer is 30.0 μm or less, the adhesion with the base material and the chipping resistance of the coating layer will be improved.

The intermediate layer contains α type Al₂O₃When RSA described later is a predetermined value or more, α type Al oriented in the (001) plane is contained in a large amount in the intermediate layer₂O₃Particles. It is considered that since the intermediate layer having such a structure exhibits excellent heat resistance, the coated cutting tool is excellent in resistance to crater wear, and the wear resistance is improved.

If containing a large amount of α type Al oriented along the (001) plane₂O₃The particles may fall off under cutting conditions under which a load acts on the coated cutting tool. Therefore, the coated cutting tool of the present embodiment has an upper layer on the surface of the intermediate layer, the upper layer having RSB, which will be described later, of a predetermined value or more and containing a large amount of formula (1) [ Ti (C) oriented along the (111) plane_1-x-yN_xO_y)]The adhesion between the upper layer and the intermediate layer is good, and α type Al can be suppressed₂O₃The particles fall off, and as a result, the wear resistance and the fracture resistance are improved.

Further, in the coated cutting tool of the present embodiment, the intermediate layer is exposed at least in the honing portion. By exposing the intermediate layer to the portion in contact with the workpiece during cutting, it was confirmed that the welding of the workpiece was reduced and the quality of the machined surface was improved.

Fig. 1 is a schematic cross-sectional view showing an example of a coated cutting tool according to the present embodiment. The coated cutting tool 6 includes a substrate 1 and a coating layer 5 formed on a surface of the substrate 1, and in the coating layer 5, a lower layer 2, an intermediate layer 3, and an upper layer 4 are laminated on a surface side in this order from the substrate side.

Fig. 2 is a schematic cross-sectional view showing an example of the coated cutting tool according to the present embodiment. The coated cutting tool 6 includes a rake face 7, a flank face 8, and a honed portion 9. The honing 9 connects the rake face 7 and the flank face 8 and is rounded.

The coating layer 5 is formed on the surface of the substrate 1, and the intermediate layer 3 is exposed in the honing portion 9. in the rake face 7 and the flank face 8, the coating layer 5 has the lower layer 2, the intermediate layer 3, and the upper layer 4. the intermediate layer 3 of the present embodiment contains α type Al₂O₃Thus, the reaction with the material to be cut is suppressed compared to, for example, TiCN or TiCNO for the upper layer 4. Thus, it is considered that if the intermediate layer 3 is exposed at the honing portion 9, welding can be suppressed. Further, it is considered that when the workpiece is welded to the honing portion 9, the machined surface is damaged by contact with the welded workpiece, and the machined surface is clouded. Therefore, the intermediate layer 3 is exposed to the honing portion 9, whereby the quality of the machined surface can be improved.

The intermediate layer 3 is also exposed in the region of the rake face 7 up to 3mm from the boundary with the honed portion 9. In fact, welding occurs not only in the honing portion 9 but also in the range of 3mm from the boundary with the honing portion 9 of the rake face 7, and therefore, exposing the intermediate layer 3 in this range will improve the processed surface quality.

The coated cutting tool 6 brings the rake face 7 and the honing portion 9 into contact with the workpiece, and the cut workpiece is discharged to the outside from the flank face 8.

Fig. 3 is a schematic cross-sectional view showing an example of the coated cutting tool according to the present embodiment. As shown in fig. 3, the intermediate layer 3 may be exposed on the rake face 7 of the coated cutting tool 6.

The coated cutting tool of the present embodiment includes a base material and a coating layer formed on a surface of the base material. Specific examples of the type of coated cutting tool include replaceable cutting inserts for milling or turning, drills, and end mills.

< substrate >

The base material used in the present embodiment is not particularly limited as long as it can be used as a base material for a coated cutting tool. Examples of such a base material include cemented carbide, cermet, ceramics, a cubic boron nitride sintered body, a diamond sintered body, and high-speed steel. Among them, the base material is preferably a cemented carbide, a cermet, a ceramic, or a sintered cubic boron nitride compact, and more preferably a cemented carbide, because wear resistance and chipping resistance are more excellent.

In addition, the substrate may be a substrate whose surface has been modified. For example, in the case where the base material is made of cemented carbide, a de- β layer may also be formed on the surface thereof. In addition, in the case where the substrate is made of cermet, a hardened layer may also be formed on the surface thereof. Even if the surface of the substrate is modified in this way, the effects of the present invention can be exhibited.

< coating layer >

The average thickness of the coating layer used in the present embodiment on the rear blade side is 5.0 μm or more and 30.0 μm or less. In the coated cutting tool of the present embodiment, if the average thickness of the coating layer is 5.0 μm or more, the wear resistance is improved, and if the average thickness of the coating layer is 30.0 μm or less, the adhesion between the coating layer and the substrate and the chipping resistance are improved. From the same viewpoint, the average thickness of the coating layer is preferably 10.0 μm to 27.0 μm, more preferably 12.0 μm to 25.5 μm, still more preferably 13.0 μm to 20.0 μm, and yet more preferably 14.9 μm to 19.3 μm.

The average thickness of the entire coating layer in the coated cutting tool of the present embodiment can be obtained by measuring the thickness of the entire coating layer at a section at the rear cutting edge side 3 or more and calculating the arithmetic mean value thereof.

(lower layer)

The lower layer used in the present embodiment comprises one or more Ti compound layers composed of Ti and a Ti compound of at least one element selected from the group consisting of C, N, O and B if the coated cutting tool is used on a substrate and contains α type Al₂O₃The lower layer is provided between the intermediate layers, so that the abrasion resistance and adhesion are improved.

The Ti compound layer is not particularly limited, but examples thereof include a TiC layer made of TiC, a TiN layer made of TiN, a TiCN layer made of TiCN, a TiCO layer made of TiCO, and TiCTiCNO layer, TiON layer made of TiON, and TiB₂Formed TiB₂And (3) a layer.

The lower layer may be composed of one layer or may be composed of a plurality of layers (for example, two or three layers), but is preferably composed of a plurality of layers, more preferably composed of two or three layers, and still more preferably composed of three layers. From the viewpoint of further improving the wear resistance and adhesion, the Ti compound constituting the Ti compound layer included in the lower layer is preferably selected from TiN, TiC, TiCN, TiCNO, TiON, and TiB₂At least one member of the group consisting of. Further, if at least one layer of the lower layer is a TiCN layer, it is preferable because the abrasion resistance is further improved. In the case where the lower layer is composed of three layers, a TiC layer or a TiN layer may be formed as a 1 st layer on the surface of the base material, a TiCN layer may be formed as a 2 nd layer on the surface of the 1 st layer, and a TiCNO layer or a TiCO layer may be formed as a 3 rd layer on the surface of the 2 nd layer. Among them, the lower layer may also be one in which a TiN layer is formed as a 1 st layer on the surface of the base material, a TiCN layer is formed as a 2 nd layer on the surface of the 1 st layer, and a TiCNO layer is formed as a 3 rd layer on the surface of the 2 nd layer.

The average thickness of the lower layer used in the present embodiment is preferably 3.0 μm or more and 15.0 μm or less on the rear blade side. In the coated cutting tool of the present embodiment, the wear resistance is improved by making the average thickness of the lower layer 3.0 μm or more. On the other hand, in the coated cutting tool of the present embodiment, when the average thickness of the lower layer is 15.0 μm or less, the peeling of the coating layer is suppressed mainly, and the chipping resistance is improved. From the same viewpoint, the average thickness of the lower layer is preferably 3.5 μm to 13.0 μm, more preferably 4.0 μm to 12.5 μm, and still more preferably 5.0 μm to 11.0 μm on the back blade side.

The average thickness of the lower layer is preferably in the above range even in the front blade side and the honing portion side. The thicknesses of the respective materials described below are preferably in the same range on the rear blade side, the front blade side, and the honing portion side.

From the viewpoint of further improving the wear resistance and the chipping resistance, the average thickness of the TiC layer or the TiN layer is preferably 0.05 μm or more and 1.0 μm or less. From the same viewpoint, the average thickness of the TiC layer or TiN layer is preferably 0.10 μm or more and 0.5 μm or less, and more preferably 0.15 μm or more and 0.3 μm or less.

From the viewpoint of further improving the wear resistance and the chipping resistance, the average thickness of the TiCN layer is preferably 2.0 μm or more and 20.0 μm or less. From the same viewpoint, the average thickness of the TiCN layer is more preferably 2.5 μm or more and 15.0 μm or less, and still more preferably 4.5 μm or more and 12.0 μm or less.

From the viewpoint of further improving the wear resistance and the defect resistance, the average thickness of the TiCNO layer or the TiCO layer is preferably 0.1 μm or more and 1.0 μm or less. From the same viewpoint, the average thickness of the TiCNO layer or TiCO layer is more preferably 0.2 μm or more and 0.5 μm or less.

The Ti compound layer is a layer composed of a Ti compound of Ti and at least one element selected from the group consisting of C, N, O and B, but may contain a trace amount of components other than the above elements as long as the function and effect of the lower layer can be exerted.

(intermediate layer)

The intermediate layer used in the present embodiment contains α type Al₂O₃。

In the intermediate layer used in the present embodiment, the 1 st cross section parallel to the interface between the substrate and the lower layer at a distance of 1 μm from the interface on the upper layer side of the intermediate layer toward the substrate satisfies the condition represented by the following formula (i).

RSA≥40 (i)

(wherein RSA is the ratio (unit: area%) of the cross-sectional area of the particles having the misorientation A of 0 degrees or more and less than 10 degrees to the cross-sectional area of the particles having the misorientation A of 0 degrees or more and 45 degrees or less in the 1 st cross-section, and the misorientation A is the normal line of the 1 st cross-section and α type Al in the intermediate layer₂O₃Angle (unit: degree) formed by the normal line of the (001) plane of the particle (1). )

Since the coated cutting tool of the present embodiment has RSA of 40 area% or more and excellent crater wear resistance, wear resistance can be improved. From the same viewpoint, RSA is preferably 43 area% or more, more preferably 50 area% or more, and further preferably 60 area% or more. The upper limit of RSA is not particularly limited, and may be 80 area% or less, for example.

RSA can be determined by the method described in the examples.

The average thickness of the intermediate layer used in the present embodiment is preferably 3.0 μm or more and 15.0 μm or less on the back blade side. If the average thickness of the intermediate layer is 3.0 μm or more, the dent wear resistance in the rake face of the coated cutting tool tends to be further improved, and if the average thickness of the intermediate layer is 15.0 μm or less, the peeling of the coating layer is further suppressed, and the chipping resistance of the coated cutting tool tends to be further improved. From the same viewpoint, the average thickness of the intermediate layer is more preferably 3.0 μm or more and 12.0 μm or less, and still more preferably 3.0 μm or more and 10.0 μm or less on the back blade side.

The average thickness of the intermediate layer is also preferably in the above range in the front blade side and in the honing side. When the treatment for removing the upper layer of the rake face is performed, the average thickness of the intermediate layer on the rake face side may be smaller than the average thickness of the intermediate layer on the flank face side.

The intermediate layer is formed of α type Al₂O₃A layer made of (α type alumina) may be used, and α type Al may or may not be contained as long as the effect of the present invention can be exhibited₂O₃Other components.

(Upper layer)

The upper layer used in this embodiment contains a compound represented by the following formula (1):

Ti(C_1-x-yN_xO_y) (1)

(wherein x is the atomic ratio of N to the total of C, N and O, and y is the atomic ratio of O to the total of C, N and O, and satisfies 0.15. ltoreq. x.ltoreq.0.65 and 0. ltoreq. y.ltoreq.0.20.)

In the upper layer used in the present embodiment, a 2 nd cross section parallel to the interface between the substrate and the lower layer, which is located at a distance of 1 μm from the interface on the intermediate layer side of the upper layer toward the interface on the opposite side thereof, satisfies the condition represented by the following formula (ii).

RSB≥40 (ii)

(wherein RSB is the ratio (unit: area%) of the cross-sectional area of the particle having the misorientation B of 0 degrees or more and less than 10 degrees to the cross-sectional area of the particle having the misorientation B of 0 degrees or more and 45 degrees or less in the 2 nd cross-section, and the misorientation B is the angle (unit: degrees) formed by the normal line of the 2 nd cross-section and the normal line of the (111) plane of the particle of the compound represented by formula (1) in the upper layer.)

Since the coated cutting tool of the present embodiment has RSB of 40 area% or more, α type Al can be suppressed₂O₃The wear resistance and the defect resistance will be improved. From the same viewpoint, RSB is preferably 45 area% or more, and more preferably 50 area% or more. The upper limit of RSB is not particularly limited, and may be, for example, 75 area% or less.

RSB can be obtained by the method described in the examples.

The average thickness of the upper layer used in the present embodiment is preferably 1.0 μm or more and 6.0 μm or less on the back blade side, and α type Al is suppressed by setting the average thickness to 1.0 μm or more₂O₃The effect of particle shedding tends to be further improved, and the defect resistance tends to be further improved by setting the average thickness of the upper layer to 6.0 μm or less. From the same viewpoint, the average thickness of the upper layer is more preferably 1.4 μm or more and 5.8 μm or less on the rear blade side.

When having an upper layer on the rake face side, the average thickness of the upper layer is preferably in the above range even in the rake face side.

With respect to the compound represented by the formula (1) used for the upper layer, if x is 0.15 or more, the toughness tends to be improved and hence the chipping resistance tends to be further improved, and on the other hand, if x is 0.65 or less, the hardness becomes high and the reaction wear can be suppressed since the contents of C and O are relatively high, and hence the wear resistance and the oxidation resistance tend to be further improved. From the same viewpoint, x in the formula (1) is preferably 0.18 to 0.50, and more preferably 0.20 to 0.40.

In the compound represented by the formula (1) used for the upper layer, if y is 0.20 or less, the content of C and N is relatively high, so that the hardness is high and the toughness is improved, and therefore the wear resistance and the fracture resistance tend to be further improved, from the same viewpoint, y in the formula (1) is preferably 0.01 to 0.18, more preferably 0.03 to 0.15, and if y is 0.01 or more, the adhesiveness is mainly improved, so that α type Al can be suppressed from being improved₂O₃The particles of the layer fall off, as a result of which the wear resistance and the defect resistance will be improved.

The upper layer may contain or not contain a component different from the compound represented by formula (1) as long as it has a layer composed of the compound represented by formula (1) and can exhibit the effects of the present invention.

(outermost layer)

The coating layer used in this embodiment may include an outermost layer on the side opposite to the substrate (i.e., the surface of the upper layer) of the upper layer. It is preferable that the outermost layer is a layer of a compound composed of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si and Y and at least one element selected from the group consisting of C, N, O and B (preferably N element), because the wear resistance is more excellent. From the same viewpoint, the outermost layer is more preferably a layer of a compound composed of at least one element selected from the group consisting of Ti, Nb, Cr, Al, and Si and at least one element selected from the group consisting of C, N, O and B (preferably N), even more preferably a layer of a compound composed of at least one element selected from the group consisting of Ti, Cr, Al, and Si and N, and even more preferably a TiN layer composed of TiN.

In the present embodiment, the average thickness of the outermost layer is preferably 0.1 μm or more and 1.0 μm or less on the rear blade side. By making the average thickness of the outermost layer within the above range, the wear resistance tends to be further improved. From the same viewpoint, the average thickness of the outermost layer is preferably 0.1 μm or more and 0.5 μm or less.

If the outermost layer is provided on the rake face side, the average thickness of the outermost layer is preferably in the above range also on the rake face side.

(method of Forming coating layer)

Examples of the method for forming each layer constituting the coating layer in the coated cutting tool according to the present embodiment include the following methods. However, the method of forming each layer is not limited to this.

For example, a Ti compound layer composed of a nitride layer of Ti (hereinafter also referred to as "TiN layer") can be formed by a chemical vapor deposition method performed under the following conditions: the composition of the raw material gas is TiCl₄：5.0～10.0mol％、N₂：20～60mol％、H₂: the temperature of the remaining part is 850 to 1050 ℃, and the pressure is 300 to 400 hPa.

A Ti compound layer composed of a carbide layer of Ti (hereinafter also referred to as a "TiC layer") can be formed by a chemical vapor deposition method performed under the following conditions: the raw material composition is set as TiCl₄：1.5～3.5mol％、CH₄：3.5～5.5mol％、H₂: the temperature of the remaining part is set to 950 to 1050 ℃ and the pressure is set to 70 to 80 hPa.

The Ti compound layer composed of a carbonitride layer of Ti (hereinafter also referred to as "TiCN layer") can be formed by a chemical vapor deposition method performed under the following conditions: the raw material composition is set as TiCl₄：5.0～7.0mol％、CH₃CN：0.5～1.5mol％、H₂: the remaining part is set to 800 to 900 ℃ and 60 to 80 hPa.

The Ti compound layer composed of a Ti oxycarbonitride layer (hereinafter also referred to as "TiCNO layer") in the lower layer can be formed by a chemical vapor deposition method performed under the following conditions: the raw material composition is set as TiCl₄：3.0～4.0mol％、CO：0.5～1.0mol％、N₂：30～40mol％、H₂: the temperature of the remaining part is set to 950 to 1050 ℃ and the pressure is set to 50 to 150 hPa.

The Ti compound layer composed of a Ti oxycarbide layer (hereinafter also referred to as "TiCO layer") can be formed by a chemical vapor deposition method performed under the following conditions:the raw material composition is set as TiCl₄：1.0～2.0mol％、CO：2.0～3.0mol％、H₂: the temperature of the remaining part is set to 950 to 1050 ℃ and the pressure is set to 50 to 150 hPa.

Containing α type Al₂O₃The intermediate layer of (2) can be formed, for example, by the following method.

First, one or more lower layers composed of a Ti compound layer are formed on the surface of a base material, then, the surface of the layer farthest from the base material among those layers is oxidized, and then, α type Al is formed on the surface of the layer farthest from the base material₂O₃Form α type Al in a state where the core is formed₂O₃。

More specifically, the oxidation of the surface of the layer farthest from the base material is performed with a raw material composition of CO: 0.1 to 0.3 mol% of CO₂：0.3～1.0mol％、H₂: the rest is carried out at 950 to 1050 ℃ and under 50 to 60hPa (oxidation step). The time for the oxidation treatment is preferably 1 to 3 minutes.

Thereafter, α type Al₂O₃The core of the layer is formed by making the raw material composition AlCl₃：1.0～4.0mol％、CO：0.05～2.0mol％、CO₂：1.0～3.0mol％、HCl：2.0～3.0mol％、H₂: the remainder is formed by chemical vapor deposition at 880 to 930 ℃ and under 60 to 80hPa (nucleation step).

Then, α type Al₂O₃By making the raw material composition AlCl₃：2.0～5.0mol％、CO₂：2.5～4.0mol％、HCl：2.0～3.0mol％、H₂S：0.15～0.25mol％、H₂: the remaining part is formed by chemical vapor deposition at 950 to 1000 ℃ and under 60 to 80hPa (film forming step).

In order to set RSA (area%) to a specific value or more, the oxidation treatment time in the oxidation step, the proportion of CO in the gas composition in the oxidation step and/or the nucleation step, or the film formation temperature in the film formation step may be controlled. More specifically, by increasing the oxidation treatment time in the oxidation step, increasing the proportion of CO in the gas composition in the oxidation step and/or the nucleation step, or increasing the film formation temperature in the film formation step to be higher than the nucleation temperature in the nucleation step, the proportion (area%) of particles having an angular orientation difference a within a specific range can be increased, thereby increasing the RSA.

Further, an upper layer composed of a layer of a carbon oxynitride of Ti (hereinafter, also referred to as "TiCNO layer") is formed on the surface of the intermediate layer.

The TiCNO layer in the upper layer can be formed by making the starting material composition TiCl₄：4.0～8.0mol％、CH₃CN：0.3～2.5mol％、C₂H₄：0～2.0mol％、CO：0～3.5mol％、N₂：1.0～25.0mol％、H₂: the remaining part is formed by chemical vapor deposition at 950 to 1050 ℃ and under 60 to 80hPa (upper layer forming step).

In order to set RSB (area%) to a specific value or more, the temperature is controlled in the upper layer forming step, or CH in the raw material composition is controlled₃The proportion of CN is just needed. More specifically, the temperature in the upper layer forming step is increased, or CH in the raw material composition is increased₃The proportion of CN can increase RSB (area%).

In order to control the atomic composition of the compound represented by the above formula (1), the raw material composition may be appropriately adjusted. More specifically, for example, in order to increase the proportion of carbon (C) in the atomic composition of the compound represented by the above formula (1), a method of increasing the proportion of CO in the raw material composition is exemplified.

The thickness of each layer in the coating layer of the coated cutting tool of the present embodiment can be measured by observing the cross-sectional structure of the coated cutting tool with an optical microscope, a Scanning Electron Microscope (SEM), an FE-SEM, or the like. The average thickness of each layer in the coated cutting tool of the present embodiment can be determined by measuring the thickness of each layer at 3 or more points in the vicinity of a position 50 μm from the edge line portion of the cutting edge toward the center portion of the flank of the coated cutting tool and calculating the arithmetic mean value thereof. The composition of each layer can be measured from the cross-sectional structure of the coated cutting tool of the present embodiment by using an energy dispersive X-ray spectrometer (EDS), a wavelength dispersive X-ray spectrometer (WDS), or the like.