Coated Cutting Tools

Abstract

To provide a coated cutting tool capable of extending a tool life by having excellent wear resistance, chipping resistance and fracture resistance.SOLUTION: The coating layer includes a lower layer, an intermediate layer, and an upper layer in this order from the substrate side toward the coating layer surface side, the lower layer includes a specific Ti compound layer, and the intermediate layer includes an α - Al2O3 layer, wherein the upper layer includes a TiCN layer, an average thickness of the entire coating layer is 8.5 μm or more and 30.0 μm or less, an average thickness of the upper layer is 1.0 μm or more and 6.0 μm or less, and in the TiCN layer of the upper layer, an average diameter of a region in which an orientation difference B between a normal line of a cross section in a direction parallel to a surface of the base material and a (220) plane normal line is 0° or more and less than 15° is less than 5.0 μm, and in the TiCN layer of the upper layer, 20≤RSA≤70 and 20≤RSB≤60 are satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a coated cutting tool. [Background technology]

[0002] It is well known that coated cutting tools, which are formed by depositing a coating layer with a total thickness of 3 to 20 μm by chemical vapor deposition on the surface of a substrate made of cemented carbide, are used for cutting steel, cast iron, etc. As the coating layer, for example, a coating layer consisting of a single layer or a multilayer of two or more types selected from the group consisting of Ti carbide, nitride, carbonitride, carbonate, and carbonitride oxide, and aluminum oxide (Al2O3) is known.

[0003] For example, Patent Document 1 describes a surface-coated member in which a multi-layer coating including at least one TiCN layer is provided on the surface of a substrate, and the uppermost TiCN layer among the TiCN layers is made of TiCN granular crystals and has the strongest (422) peak in X-ray diffraction measurement.

[0004] Furthermore, for example, Patent Document 2 describes a coated hard alloy having a coating layer provided on the surface of the hard alloy, the coating layer comprising an inner layer, an intermediate layer, and an outer layer, in that order from the hard alloy side, the inner layer comprising one or more layers selected from carbides, nitrides, borides, oxides, and solid solutions thereof of Groups IVa, Va, and VIa of the periodic table, the intermediate layer comprising one or more layers selected from aluminum oxide, zirconium oxide, and solid solutions thereof, the outer layer comprising one or more layers selected from carbides, nitrides, borides, oxides, and solid solutions thereof of Groups IVa, Va, and VIa of the periodic table, and aluminum oxide, including a titanium carbonitride layer having a columnar structure, and the maximum roughness Amax of the surface layer portion of the intermediate layer in the cross-sectional structure of the coated hard alloy and the maximum roughness Bmax of the surface layer portion of the titanium carbonitride layer having a columnar structure in the outer layer satisfying Formula 1. (Bmax / Amax)<1 …Equation 1 (However, 0.5 μm <Amax<4.5μm 0.5μm≦Bmax≦4.5μm) Patent Document 2 also describes that the relationship between the maximum roughness Amax of the surface layer of the intermediate layer in the cross-sectional structure of the coated hard alloy and the roughness Bmax of the surface layer of the titanium carbonitride layer having a columnar structure in the outer layer satisfies Equation 2. (Bmax / Amax)<0.8 …Equation 2 Patent Document 2 also describes that the orientation index TC of the titanium carbonitride layer having a columnar structure in the outer layer, as shown in Equation 3, is largest in any one of the (220), (311), (331) and (422) planes, and that the maximum value is 1.3 or more and 3.5 or less.

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[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-188626 [Patent Document 2] International Publication No. 2000 / 079022 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent cutting processes, speeds, feed rates, and depths of cut have become increasingly pronounced, necessitating improved tool wear resistance, chipping resistance, and fracture resistance. In particular, cutting processes that place loads on coated cutting tools, such as high-speed steel cutting, have become more common in recent years. Under such harsh cutting conditions, conventional tools lack sufficient wear resistance, chipping resistance, and fracture resistance, preventing tool life extension. The surface-coated member described in Patent Document 1 has an uppermost TiCN layer with the strongest (422) peak. While this layer offers excellent wear resistance, it is prone to particle shedding, leaving room for improvement in chipping resistance and fracture resistance. Furthermore, the coated hard alloy described in Patent Document 2 does not take into account the dispersion of particles oriented in the (220) plane of the TiCN layer (titanium carbonitride layer) in the outer layer, leaving room for improvement in wear resistance, chipping resistance, and fracture resistance.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coated cutting tool that has excellent wear resistance, chipping resistance, and fracture resistance, thereby enabling an extension of tool life. [Means for solving the problem]

[0008] From the above viewpoint, the inventors have conducted extensive research into extending the tool life of coated cutting tools, and as a result have discovered that a specific configuration can improve wear resistance, chipping resistance, and fracture resistance, thereby making it possible to extend the tool life, which has led to the completion of the present invention.

[0009] That is, the present invention is as follows. [1] A coated cutting tool comprising a substrate and a coating layer formed on a surface of the substrate, the coating layer includes a lower layer, an intermediate layer, and an upper layer in this order from the substrate side toward the surface side of the coating layer, the lower layer includes a Ti compound layer made of a Ti compound of Ti and at least one element selected from the group consisting of C, N, O, and B, the intermediate layer includes an α-Al2O3 layer made of α-type aluminum oxide, the upper layer includes a TiCN layer made of Ti carbonitride, The average thickness of the entire coating layer is 8.5 μm or more and 30.0 μm or less, The upper layer has an average thickness of 1.0 μm or more and 6.0 μm or less, The upper TiCN layer satisfies the conditions represented by the following formulas (i) and (ii), 30≦RSA≦70 (i) (In formula (i), RSA is the ratio (unit: area %) of the total cross-sectional area of ​​a region A in which the misorientation A, which is the angle (unit: degree) between the normal to the cross-section of the TiCN layer of the upper layer in a direction parallel to the surface of the base material and the normal to the (422) plane of a grain of the TiCN layer, is 0 degrees or more and less than 15 degrees, when the total area of ​​the entire cross-section is taken as 100 area %).) 20≦RSB≦60 (ii) (In formula (ii), RSB is the ratio (unit: area %) of the total cross-sectional area of ​​a region B in which the misorientation B, which is the angle (unit: degree) between the normal to the cross-section of the TiCN layer of the upper layer parallel to the surface of the base material and the normal to the (220) plane of a grain of the TiCN layer, is 0 degrees or more and less than 15 degrees, when the total area of ​​the entire cross-section is taken as 100 area %).) A coated cutting tool, wherein the average diameter of the region B in the upper TiCN layer is less than 5.0 μm. [2] The coated cutting tool according to [1], wherein the average diameter of the region B in the upper TiCN layer is 1.0 μm or more. [3] The coated cutting tool according to [1] or [2], wherein the average diameter of the region A in the upper TiCN layer is 5.0 μm or more and 30.0 μm or less. [4] The coated cutting tool according to any one of [1] to [3], wherein the average particle size of the particles in the upper TiCN layer is 0.3 μm or more and 1.2 μm or less. [5] The coated cutting tool according to any one of [1] to [4], wherein in the intermediate layer, a texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-AlO layer, represented by the following formula (iii), is 5.0 or more and 8.9 or less.

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[0010] The coated cutting tool of the present invention has excellent wear resistance, chipping resistance and fracture resistance, thereby enabling an extended tool life. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing an example of a coated cutting tool of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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. The present invention can be modified in various ways without departing from the gist of the present invention. In the drawings, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios of the drawings are not limited to the ratios shown in the drawings.

[0013] The coated cutting tool of this embodiment is a coated cutting tool including a substrate and a coating layer formed on the surface of the substrate, the coating layer comprising, from the substrate side toward the surface side of the coating layer, a lower layer, an intermediate layer, and an upper layer in this order, the lower layer comprising a Ti compound layer comprising a Ti compound of Ti and at least one element selected from the group consisting of C, N, O, and B, the intermediate layer comprising an α-Al2O3 layer comprising α-aluminum oxide, the upper layer comprising a TiCN layer comprising Ti carbonitride, the average thickness of the entire coating layer being 8.5 μm or more and 30.0 μm or less, the average thickness of the upper layer being 1.0 μm or more and 6.0 μm or less, and the TiCN layer of the upper layer satisfying the conditions represented by the following formulas (i) and (ii): 30≦RSA≦70 (i) (In formula (i), RSA is the ratio (unit: area %) of the total cross-sectional area of ​​region A in which the misorientation A, which is the angle (unit: degrees) between the normal to the cross-section of the TiCN layer of the upper layer in a direction parallel to the surface of the substrate and the normal to the (422) plane of the grain of the TiCN layer, is 0 degrees or more and less than 15 degrees, when the total area of ​​the entire cross-section is taken as 100 area %).) 20≦RSB≦60 (ii) (In formula (ii), RSB is the ratio (unit: area %) of the total cross-sectional area of ​​region B in which the misorientation B, which is the angle (unit: degree) between the normal to the cross-section of the TiCN layer of the upper layer in a direction parallel to the surface of the substrate and the normal to the (220) plane of the grain of the TiCN layer, is 0 degrees or more and less than 15 degrees, when the total area of ​​the entire cross-section is taken as 100 area %).) In the upper TiCN layer, the average diameter of the region B is less than 5.0 μm.

[0014] The coated cutting tool of this embodiment, having the above-described configuration, can improve wear resistance, chipping resistance, and fracture resistance, thereby extending tool life. The factors that contribute to the improved wear resistance, chipping resistance, and fracture resistance of the coated cutting tool of this embodiment are believed to be as follows. However, the present invention is not limited by these factors. Specifically, the coated cutting tool of this embodiment includes a Ti compound layer composed of a Ti compound containing Ti and at least one element selected from the group consisting of C, N, O, and B as the lower layer of the coating layer. The coated cutting tool of this embodiment has improved wear resistance and adhesion when such a lower layer is provided between the substrate and the intermediate layer containing an α-Al2O3 layer composed of α-aluminum oxide. Furthermore, the coated cutting tool of this embodiment includes a TiCN layer composed of Ti carbonitride as the upper layer, which increases hardness and improves wear resistance. Furthermore, the coated cutting tool of this embodiment has excellent wear resistance because the average thickness of the entire coating layer is 8.5 μm or more. On the other hand, the coated cutting tool of this embodiment has an average thickness of the entire coating layer of 30.0 μm or less, which improves the adhesion of the coating layer, resulting in excellent chipping resistance and fracture resistance. Furthermore, the coated cutting tool of this embodiment has an average thickness of the upper layer of 1.0 μm or more, which improves the wear resistance. On the other hand, the coated cutting tool of this embodiment has an average thickness of the upper layer of 6.0 μm or less, which improves the adhesion of the coating layer, resulting in excellent chipping resistance and fracture resistance. Furthermore, the coated cutting tool of this embodiment has an RSA of 30 area % or more, which improves the wear resistance. On the other hand, the coated cutting tool of this embodiment has an RSA of 70 area % or less, which suppresses particle shedding, resulting in excellent chipping resistance and fracture resistance. Furthermore, the coated cutting tool of this embodiment has an RSB of 20 area % or more, which suppresses particle shedding, resulting in excellent chipping resistance and fracture resistance. On the other hand, the coated cutting tool of this embodiment has an RSB of 60 area % or less, which improves wear resistance.Furthermore, in the coated cutting tool of this embodiment, the average diameter of regions B in the upper TiCN layer is less than 5.0 μm, which indicates that regions B are dispersed throughout the TiCN layer, and the effect of suppressing particle shedding by making the RSB 20 area % or more can be effectively and reliably achieved, and wear resistance is improved by reducing the coarse regions B. The combination of these features is believed to improve the wear resistance, chipping resistance, and fracture resistance of the coated cutting tool of this embodiment, resulting in an extended tool life.

[0015] 1 is a 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 the surface of the substrate 1. The coating layer 5 includes a lower layer 2, an intermediate layer 3, and an upper layer 4 stacked in this order from the substrate side upward.

[0016] The coated cutting tool of this embodiment includes a substrate and a coating layer formed on the surface of the substrate. Specific examples of the coated cutting tool include indexable cutting inserts for milling or turning, drills, and end mills.

[0017] The substrate used in this embodiment is not particularly limited as long as it can be used as the substrate of a coated cutting tool. Examples of such substrates include cemented carbide, cermet, ceramics, cubic boron nitride sintered body, diamond sintered body, and high-speed steel. Among them, if the substrate is any of cemented carbide, cermet, ceramics, and cubic boron nitride sintered body, it is preferable because it has better wear resistance and chipping resistance, and from the same viewpoint, it is more preferable that the substrate is cemented carbide.

[0018] The substrate may have a surface modified. For example, if the substrate is made of cemented carbide, a de-β layer may be formed on the surface. If the substrate is made of cermet, a hardened layer may be formed on the surface. Even if the surface of the substrate is modified in this way, the effects of the present invention can be achieved.

[0019] The coating layer used in this embodiment has an overall average thickness of 8.5 μm or more and 30.0 μm or less. The coated cutting tool of this embodiment has excellent wear resistance because the overall average thickness of the coating layer is 8.5 μm or more. Meanwhile, the coated cutting tool of this embodiment has excellent chipping resistance and fracture resistance because the overall average thickness of the coating layer is 30.0 μm or less, which improves the adhesion of the coating layer. From the same perspective, the overall average thickness of the coating layer is preferably 11.3 μm or more and 28.1 μm or less, and more preferably 13.5 μm or more and 25.1 μm or less. The average thickness of each layer and the entire coating layer in the coated cutting tool of this embodiment can be determined by measuring the thickness of each layer or the thickness of the entire coating layer from three or more cross sections of each layer or the entire coating layer, and calculating the arithmetic mean value.

[0020] Bottom Layer The lower layer used in this embodiment includes a Ti compound layer made of a Ti compound of Ti and at least one element selected from the group consisting of C, N, O, and B. When such a lower layer is provided between the substrate and the intermediate layer containing an α-Al2O3 layer made of α-aluminum oxide, the coated cutting tool of this embodiment has improved wear resistance and adhesion.

[0021] The Ti compound layer in the lower 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, a TiCNO layer made of TiCNO, a TiON layer made of TiON, and a TiB2 layer made of TiB2.

[0022] The lower layer may be composed of one layer or multiple layers (e.g., two or three layers). It is preferably composed of multiple layers, more preferably two or three layers, and even more preferably three layers. The Ti compound constituting the Ti compound layer contained in the lower layer preferably includes at least one layer selected from the group consisting of a TiN layer, a TiC layer, a TiCN layer, a TiCNO layer, and a TiCO layer, from the viewpoint of further improving wear resistance and adhesion. Furthermore, in the coated cutting tool of this embodiment, when at least one lower layer is a TiCN layer, wear resistance tends to be further improved. Furthermore, in the coated cutting tool of this embodiment, when at least one lower layer is a TiN layer and the TiN layer is formed on the surface of the substrate, adhesion tends to be further improved. Furthermore, in the coated cutting tool of this embodiment, when at least one lower layer is a TiCNO layer and the TiCNO layer is formed in contact with an intermediate layer containing an α-Al2O3 layer, adhesion tends to be further improved. When the lower layer is composed of three layers, a TiC layer or a TiN layer may be formed on the surface of the substrate as a first layer, a TiCN layer may be formed on the surface of the first layer as a second layer, and a TiCNO layer or a TiCO layer may be formed on the surface of the second layer as a third layer. Among them, the lower layer may be formed on the surface of the substrate as a first layer, a TiCN layer may be formed on the surface of the first layer as a second layer, and a TiCNO layer may be formed on the surface of the second layer as a third layer.

[0023] The average thickness of the lower layer used in this embodiment is preferably 3.0 μm or more and 15.0 μm or less. The coated cutting tool of this embodiment tends to have excellent wear resistance because the average thickness of the lower layer is 3.0 μm or more. On the other hand, the coated cutting tool of this embodiment tends to have excellent chipping resistance and fracture resistance because the average thickness of the lower layer is 15.0 μm or less, which improves the adhesion of the coating layer. From the same perspective, the average thickness of the lower layer is preferably 3.2 μm or more and 14.5 μm or less, and more preferably 4.0 μm or more and 13.0 μm or less.

[0024] In the lower layer used in this embodiment, for example, the average thickness of the TiC or TiN layer is preferably 0.1 μm or more and 1.0 μm or less from the viewpoint of further improving wear resistance and chipping resistance. From the same viewpoint, the average thickness of the TiC or TiN layer is more preferably 0.1 μm or more and 0.5 μm or less, and even more preferably 0.1 μm or more and 0.3 μm or less.

[0025] In the lower layer used in this embodiment, for example, the average thickness of the TiCN layer is preferably 3.0 μm or more and 14.0 μm or less from the viewpoint of further improving wear resistance and chipping resistance, more preferably 3.5 μm or more and 12.5 μm or less, and further preferably 4.5 μm or more and 9.5 μm or less from the same viewpoint.

[0026] In the lower layer used in this embodiment, for example, the average thickness of the TiCNO or TiCO layer is preferably 0.1 μm or more and 1.0 μm or less from the viewpoint of further improving wear resistance and chipping resistance, more preferably 0.2 μm or more and 1.0 μm or less, and even more preferably 0.3 μm or more and 1.0 μm or less from the same viewpoint.

[0027] The Ti compound layer in the lower layer is a layer consisting 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 trace amounts of components other than the above elements as long as the lower layer exhibits its desired effect.

[0028] [Middle layer] The intermediate layer used in this embodiment contains an α-Al2O3 layer made of α-type aluminum oxide.

[0029] The average thickness of the intermediate layer used in this embodiment is preferably 3.0 μm or more and 15.0 μm or less. When the average thickness of the intermediate layer containing an α-Al2O3 layer is 3.0 μm or more, the coated cutting tool of this embodiment tends to have excellent wear resistance. Furthermore, the TC(0,0,12) described below is easily controlled. On the other hand, when the average thickness of the intermediate layer containing an α-Al2O3 layer is 15.0 μm or less, the coated cutting tool of this embodiment tends to have excellent chipping resistance and fracture resistance due to improved adhesion of the coating layer. From the same viewpoint, the average thickness of the intermediate layer is more preferably 4.0 μm or more and 14.0 μm or less, and even more preferably 5.0 μm or more and 10.0 μm or less.

[0030] In the coated cutting tool of this embodiment, the texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-Al2O3 layer, represented by the following formula (iii), is preferably 5.0 or more and 8.9 or less in the intermediate layer.

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[0031] The coated cutting tool of this embodiment tends to have excellent wear resistance when the texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-AlO layer, represented by the above formula (iii), is 5.0 or more. On the other hand, the coated cutting tool of this embodiment can be easily manufactured when the texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-AlO layer, represented by the above formula (iii), is 8.9 or less. From the same viewpoint, the texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-AlO layer, represented by the above formula (iii), is more preferably 5.3 or more and 8.8 or less, and even more preferably 6.3 or more and 8.4 or less. In this embodiment, the texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-Al2O3 layer can be determined by the method described in the examples below.

[0032] The intermediate layer only needs to contain an α-Al2O3 layer made of α-aluminum oxide, and may or may not contain components other than α-aluminum oxide (α-Al2O3) as long as the effects of the present invention are achieved.

[0033] [Top layer] The upper layer used in this embodiment includes a TiCN layer made of Ti carbonitride. The coated cutting tool of this embodiment has high hardness due to the inclusion of the TiCN layer made of Ti carbonitride in the upper layer, thereby improving wear resistance.

[0034] Furthermore, the TiCN layer of the upper layer used in this embodiment satisfies the conditions expressed by the following formulas (i) and (ii). 30≦RSA≦70 (i) (In formula (i), RSA is the ratio (unit: area %) of the total cross-sectional area of ​​a region A in which the misorientation A, which is the angle (unit: degree) between the normal to the cross-section of the TiCN layer of the upper layer in a direction parallel to the surface of the base material and the normal to the (422) plane of a grain of the TiCN layer, is 0 degrees or more and less than 15 degrees, when the total area of ​​the entire cross-section is taken as 100 area %).) 20≦RSB≦60 (ii) (In formula (ii), RSB is the ratio (unit: area %) of the total cross-sectional area of ​​a region B in which the misorientation B, which is the angle (unit: degree) between the normal to the cross-section of the TiCN layer of the upper layer parallel to the surface of the base material and the normal to the (220) plane of a grain of the TiCN layer, is 0 degrees or more and less than 15 degrees, when the total area of ​​the entire cross-section is taken as 100 area %).) The analysis position for RSA and RSB is the cross section exposed in a direction parallel to the surface of the substrate at a position where 60% or more of the average thickness of the TiCN layer in the upper layer remains from the substrate side.

[0035] The coated cutting tool of this embodiment has excellent wear resistance due to an RSA of 30 area % or more. Meanwhile, the coated cutting tool of this embodiment has excellent chipping resistance and fracture resistance due to an RSA of 70 area % or less, which suppresses particle shedding. From the same perspective, the RSA is more preferably 33 area % to 68 area %, and even more preferably 40 area % to 64 area %. Furthermore, the coated cutting tool of this embodiment has excellent chipping resistance and fracture resistance due to an RSB of 20 area % or more, which suppresses particle shedding. Meanwhile, the coated cutting tool of this embodiment has excellent wear resistance due to an RSB of 60 area % or less. From the same perspective, the RSB is more preferably 22 area % to 58 area %, and even more preferably 24 area % to 56 area %. In this embodiment, RSA and RSB can be determined by the method described in the Examples below.

[0036] In the coated cutting tool of this embodiment, the average diameter of region B in the upper TiCN layer is less than 5.0 μm. In the coated cutting tool of this embodiment, the average diameter of region B in the upper TiCN layer is less than 5.0 μm, which indicates that region B is dispersed throughout the TiCN layer. This effectively and reliably achieves the effect of suppressing particle shedding achieved by setting the RSB to 20% by area or more. Furthermore, the reduction in coarse region B improves wear resistance. Furthermore, in the coated cutting tool of this embodiment, the average diameter of region B in the upper TiCN layer is preferably 1.0 μm or more. In the coated cutting tool of this embodiment, when the average diameter of region B in the upper TiCN layer is 1.0 μm or more, the effect of suppressing particle shedding by region B tends to be effectively and reliably achieved. From the same perspective, the average diameter of region B in the upper TiCN layer is more preferably 1.1 μm to 4.8 μm, and even more preferably 1.5 μm to 4.6 μm.

[0037] In addition, in the coated cutting tool of this embodiment, the average diameter of region A in the upper TiCN layer is preferably 5.0 μm or more and 30.0 μm or less. In the coated cutting tool of this embodiment, when the average diameter of region A in the upper TiCN layer is 5.0 μm or more, the effect of improving wear resistance by setting the RSA to 30 area % or more tends to be further improved. On the other hand, in the coated cutting tool of this embodiment, when the average diameter of region A in the upper TiCN layer is 30.0 μm or less, manufacturing is easy. From the same viewpoint, the average diameter of region A in the upper TiCN layer is more preferably 5.3 μm or more and 27.5 μm or less, and even more preferably 6.0 μm or more and 18.5 μm or less.

[0038] In this embodiment, the average diameter of region B is determined by calculating the equivalent circle diameter for each region and calculating the area average value as the "average diameter of region B." The average diameter of region A is also determined in the same manner as the "average diameter of region B," except that the specified region is region A instead of region B. Specifically, it can be determined by the method described in the examples below.

[0039] In the coated cutting tool of this embodiment, the average particle size of the particles in the upper TiCN layer is preferably 0.3 μm or more and 1.2 μm or less. In the coated cutting tool of this embodiment, when the average particle size of the particles in the upper TiCN layer is 0.3 μm or more, the chipping resistance tends to be improved. On the other hand, in the coated cutting tool of this embodiment, when the average particle size of the particles in the upper TiCN layer is 1.2 μm or less, the wear resistance tends to be improved. From the same viewpoint, it is more preferable that the average particle size of the particles in the upper TiCN layer is 0.5 μm or more and 1.1 μm or less. In this embodiment, the average particle size of the particles in the TiCN layer is calculated by determining the circle-equivalent diameter of each particle and averaging the area thereof. Specifically, this can be calculated by the method described in the examples below.

[0040] The upper layer used in this embodiment may include one or more Ti compound layers made of a Ti compound of Ti and at least one element selected from the group consisting of C, N, and O, in addition to the TiCN layer made of Ti carbonitride. The Ti compound layer other than the TiCN layer in the upper layer is not particularly limited, but examples thereof include a TiC layer made of TiC, a TiN layer made of TiN, a TiCO layer made of TiCO, a TiCNO layer made of TiCNO, and a TiON layer made of TiON. Of these, the TiN layer and the TiCNO layer are preferred.

[0041] The upper layer may be composed of one layer or multiple layers (e.g., two or three layers). When the upper layer is composed of multiple layers, it is preferable to form an adhesion layer (described later) on the side in contact with the intermediate layer, and another layer may be formed on the surface of the TiCN layer opposite the substrate. When the upper layer is composed of two layers, the TiCN layer may be formed as the first layer, and a TiN layer may be formed on the surface of the first layer as the second layer. When the upper layer is composed of three layers, a TiCNO layer or a TiCO layer may be formed as the adhesion layer on the side in contact with the intermediate layer, a TiCN layer may be formed on the surface of the adhesion layer as the second layer, and a TiN layer may be formed on the surface of the second layer as the third layer.

[0042] The average thickness of the upper layer used in this embodiment is 1.0 μm or more and 6.0 μm or less. The coated cutting tool of this embodiment has excellent wear resistance because the average thickness of the upper layer is 1.0 μm or more. On the other hand, the coated cutting tool of this embodiment has excellent chipping resistance and fracture resistance because the average thickness of the upper layer is 6.0 μm or less, which improves the adhesion of the coating layer. From the same perspective, the average thickness of the upper layer is preferably 1.3 μm or more and 5.8 μm or less, and more preferably 1.4 μm or more and 5.7 μm or less.

[0043] The average thickness of the TiCN layer in the upper layer is preferably 1.0 μm or more and 5.5 μm or less. The coated cutting tool of this embodiment tends to have improved wear resistance because the average thickness of the TiCN layer in the upper layer is 1.0 μm or more. Furthermore, the coated cutting tool of this embodiment tends to have excellent chipping resistance and fracture resistance because the average thickness of the TiCN layer in the upper layer is 5.5 μm or less, which improves the adhesion of the coating layer. From the same perspective, the average thickness of the TiCN layer in the upper layer is more preferably 1.2 μm or more and 5.5 μm or less, and even more preferably 2.0 μm or more and 5.5 μm or less.

[0044] When the upper layer used in this embodiment is in contact with the intermediate layer, the upper layer preferably includes at least one layer selected from the group consisting of a layer made of TiCO, a layer made of TiON, and a layer made of TiCNO as an adhesion layer (hereinafter also simply referred to as "adhesion layer") on the side in contact with the intermediate layer. When the upper layer used in this embodiment includes such an adhesion layer, adhesion to the intermediate layer tends to be improved. From the same viewpoint, a TiCO layer or a TiCNO layer is more preferable as the adhesion layer.

[0045] In the upper layer used in this embodiment, the average thickness of the adhesion layer is preferably 0.1 μm or more and 1.0 μm or less. In the coated cutting tool of this embodiment, when the average thickness of the adhesion layer is 0.1 μm or more, the adhesion between the upper layer and the intermediate layer is excellent and chipping resistance tends to be improved. On the other hand, in the coated cutting tool of this embodiment, when the average thickness of the adhesion layer is 1.0 μm or less, the wear resistance tends to be improved. From the same viewpoint, the average thickness of the adhesion layer is more preferably 0.1 μm or more and 0.5 μm or less, and even more preferably 0.1 μm or more and 0.3 μm or less.

[0046] When the upper layer used in this embodiment is composed of multiple layers (for example, two or three layers), a TiN layer may be formed as the outermost layer (hereinafter simply referred to as the "outermost layer") that is the furthest from the substrate among the layers constituting the upper layer. When the coated cutting tool of this embodiment has such an outermost layer as the upper layer, it tends to be easier to identify the corner that has been used. In the upper layer used in this embodiment, the range of the average thickness of such an outermost layer is, for example, 0.05 μm or more and 1.0 μm or less, preferably 0.1 μm or more and 0.5 μm or less, and more preferably 0.1 μm or more and 0.3 μm or less.

[0047] The Ti compound layer in the upper layer is a Ti compound layer consisting of a Ti compound of Ti and at least one element selected from the group consisting of C, N, and O, but may contain trace amounts of components other than the above elements as long as the upper layer exhibits its functional effects.

[0048] [Method for forming coating layer] The layers constituting the coating layer of the coated cutting tool of this embodiment can be formed, for example, by the following method, although the method for forming each layer is not limited thereto.

[0049] First, a lower layer consisting of one or more Ti compound layers is formed on the surface of the substrate. Next, the surface of the layer farthest from the substrate is oxidized. After that, an α-Al2O3 layer is formed on the surface of the layer farthest from the substrate, and with this nucleus formed, an α-Al2O3 layer is formed. Furthermore, an upper layer consisting of a Ti compound layer including a TiCN layer is formed on the surface of the α-Al2O3 layer.

[0050] The method for forming the Ti compound layer in the lower layer is not particularly limited, but the following method can be mentioned, for example. For example, a Ti compound layer consisting of a Ti nitride layer (hereinafter also referred to as a "TiN layer") can be formed by chemical vapor deposition using a raw material composition of TiCl4: 5.0 to 10.0 mol%, N2: 20 to 60 mol%, H2: balance, at a temperature of 850 to 950°C and a pressure of 350 to 450 hPa.

[0051] A Ti compound layer consisting of a Ti carbide layer (hereinafter also referred to as a "TiC layer") can be formed by chemical vapor deposition using a raw material composition of TiCl4: 1.5 to 3.5 mol%, CH4: 3.5 to 5.5 mol%, H2: balance, at a temperature of 950 to 1050°C and a pressure of 70 to 80 hPa.

[0052] A Ti compound layer consisting of a Ti carbonitride layer (hereinafter also referred to as a "TiCN layer") can be formed by chemical vapor deposition using a raw material composition of TiCl4: 5.0 to 7.0 mol%, CH3CN: 0.5 to 1.5 mol%, H2: balance, at a temperature of 800 to 900°C and a pressure of 70 to 90 hPa.

[0053] The Ti compound layer consisting of a Ti oxycarbonitride layer (hereinafter also referred to as "TiCNO layer") in the lower layer can be formed by chemical vapor deposition using a raw material composition of TiCl4: 3.0 to 4.0 mol%, CO: 0.5 to 1.0 mol%, N2: 30 to 40 mol%, H2: balance, at a temperature of 950 to 1050°C and a pressure of 50 to 150 hPa.

[0054] A Ti compound layer consisting of a Ti carbonate layer (hereinafter also referred to as a "TiCO layer") can be formed by a chemical vapor deposition method using a raw material composition of TiCl4: 1.0 to 2.0 mol%, CO: 2.0 to 3.0 mol%, and H2: balance, at a temperature of 950 to 1050°C and a pressure of 50 to 150 hPa.

[0055] Moreover, the intermediate layer made of an α-Al2O3 layer (hereinafter also simply referred to as an "Al2O3 layer") is formed, for example, by the following method.

[0056] First, the surface of the lower layer farthest from the substrate is oxidized under conditions of a raw material composition of CO: 0.1-0.5 mol%, H2S: 0.05-0.15 mol%, H2: balance, a temperature of 900-950°C, and a pressure of 60-80 hPa (oxidation step). The oxidation treatment time is preferably 1-5 minutes.

[0057] Thereafter, the nuclei of the α-Al2O3 layer are formed by chemical vapor deposition using a raw material composition of AlCl3: 1.0-4.0 mol%, CO: 0.05-2.0 mol%, CO2: 1.0-3.0 mol%, HCl: 2.0-3.0 mol%, and H2: balance, at a temperature of 900-950°C and a pressure of 60-80 hPa (nucleation step). The preferred time for the nucleation step is 3-30 minutes.

[0058] The α-Al2O3 layer is formed by chemical vapor deposition using a raw material composition of AlCl3: 3.5 to 5.5 mol%, CO2: 3.0 to 4.0 mol%, HCl: 3.5 to 4.5 mol%, H2S: 0.4 to 1.0 mol%, and H2: balance, at a temperature of 980 to 1030°C and a pressure of 70 to 90 hPa (film formation process).

[0059] In order to set the texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-AlO layer, expressed by formula (iii), in the intermediate layer within the above-mentioned specific range, for example, the proportion of H2S in the gas composition in the deposition process or the average thickness of the intermediate layer may be controlled. More specifically, for example, increasing the proportion of H2S in the gas composition in the deposition process or increasing the average thickness of the intermediate layer tends to increase the texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-AlO3 layer, expressed by formula (iii). Furthermore, by carrying out the first step of forming the upper layer described below and increasing the texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-AlO layer expressed by formula (iii), the average diameter of region A tends to be increased.

[0060] Furthermore, the method for forming the upper layer is not particularly limited, but examples thereof include the following methods. First, when an adhesive layer is formed on the side that contacts the intermediate layer (α-Al2O3 layer), a Ti compound layer (adhesion layer) is formed on the surface of the α-Al2O3 layer as the first step for forming the upper layer. Next, a TiCN layer is formed on the surface of the adhesion layer as the second step for forming the upper layer. Furthermore, a Ti compound layer may be formed on the surface of the TiCN layer. Alternatively, a TiCN layer may be formed on the surface of the α-Al2O3 layer as the first step for forming the upper layer, and then a TiCN layer may be further formed as the second step for forming the upper layer.

[0061] In the first step of forming the upper layer, for example, when a TiCNO layer is formed on the surface of the α-Al2O3 layer, the upper layer can be formed by chemical vapor deposition using a raw material composition of TiCl4: 7.5 to 10.0 mol%, C2H4: 1.2 to 3.5 mol%, CH3CN: 0.7 to 1.2 mol%, CO: 1.8 to 2.4 mol%, N2: 15.0 to 25.0 mol%, H2: balance, at a temperature of 760 to 850°C and a pressure of 70 to 110 hPa.

[0062] In the first step of forming the upper layer, for example, a TiCN layer is formed on the surface of the α-Al2O3 layer. This can be formed by chemical vapor deposition using a raw material composition of TiCl4: 7.5-10.0 mol%, C2H4: 1.2-3.5 mol%, CH3CN: 0.7-1.2 mol%, N2: 15.0-25.0 mol%, and H2: balance, at a temperature of 760-850°C and a pressure of 70-110 hPa. Here, the time for forming the TiCN layer is preferably 15-25 minutes.

[0063] In the second step of forming the upper layer, when a TiCN layer is formed, the raw material composition is TiCl4: 5.0 to 7.0 mol%, CH3CN: 1.5 to 2.5 mol%, N2: 15.0 to 25.0 mol%, H2: balance, and the layer can be formed by chemical vapor deposition at a temperature of 800 to 900°C and a pressure of 70 to 120 hPa.

[0064] Furthermore, when a TiN layer is formed on the surface of a TiCN layer, it can be formed by chemical vapor deposition using a raw material composition of TiCl4: 5.0 to 10.0 mol%, N2: 20.0 to 60.0 mol%, H2: balance, at a temperature of 950 to 1050°C and a pressure of 300 to 400 hPa.

[0065] In order to set the RSA of the upper TiCN layer within the above-mentioned specific range, for example, the first step of forming the upper layer described above may be carried out and the texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-Al2O3 layer, expressed by formula (iii), may be controlled. More specifically, for example, the RSA tends to be increased by carrying out the first step of forming the upper layer described above and increasing the texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-Al2O3 layer, expressed by formula (iii).

[0066] In order to set RSB in the TiCN upper layer within the above-mentioned specific range, for example, in the first step of forming the upper layer, when the first layer formed on the surface of the intermediate layer is a TiCN layer, the proportion of C2H4 in the gas composition may be controlled. More specifically, in the first step of forming the upper layer, when the first layer formed on the surface of the intermediate layer is a TiCN layer, the RSB tends to be increased by increasing the proportion of C2H4 in the gas composition. Furthermore, in order to set RS in the TiCN layer of the upper layer within the above-mentioned specific range, for example, if the layer formed first on the surface of the intermediate layer in the first step of forming the upper layer is a TiCNO layer, the average thickness of the TiCNO layer or the proportion of C2H4 and / or CO in the gas composition may be controlled. More specifically, if the layer formed first on the surface of the intermediate layer in the first step of forming the upper layer is a TiCNO layer, RS tends to be increased by increasing the average thickness of the TiCNO layer or increasing the proportion of C2H4 and / or CO in the gas composition.

[0067] In the TiCN layer of the upper layer, the average diameter of region B can be set within the above-mentioned specific range by, for example, controlling the temperature in the first step of forming the upper layer. More specifically, by lowering the temperature in the first step of forming the upper layer, the average diameter of region B tends to be smaller.

[0068] In the upper TiCN layer ,grain In order to set the average particle size of the particles within the above-mentioned specific range, for example, the temperature may be controlled in the second step of forming the upper layer. More specifically, increasing the temperature in the second step of forming the upper layer tends to increase the average particle size of the particles. Furthermore, increasing the average particle size of the particles in the TiCN layer of the upper layer tends to increase the average diameters of the particles in region A and region B.

[0069] The thickness of each layer in the coating layer of the coated cutting tool of this embodiment can be measured by observing the cross-sectional structure of the coated cutting tool using an optical microscope, a scanning electron microscope (SEM), a field emission scanning electron microscope (FE-SEM), or the like. The average thickness of each layer in the coated cutting tool of this embodiment can be determined as the arithmetic mean of measurements of the thickness of each layer at three or more locations in the vicinity of a position 50 μm from the cutting edge ridge toward the center of the flank face of the coated cutting tool. The composition of each layer can be measured from the cross-sectional structure of the coated cutting tool of this embodiment using an energy dispersive X-ray spectrometer (EDS), a wavelength dispersive X-ray spectrometer (WDS), or the like. [Example]

[0070] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0071] A cutting insert made of cemented carbide with an insert shape of CNMG120408 (ISO standard) and a composition of 87.0% WC-8.6% Co-2.0% TiN-2.0% NbC-0.4% Cr3C2 (all mass%) was prepared as the substrate. The cutting edge of this substrate was subjected to round honing with a SiC brush, and then the surface of the substrate was cleaned.

[0072] [Invention products 1-26 and comparison products 1-15] After cleaning the surface of the substrate, a coating layer was formed by chemical vapor deposition. First, a lower layer was formed on the surface of the substrate. Specifically, the substrate was loaded into an externally heated chemical vapor deposition apparatus, and an A layer, whose composition is shown in Table 6, was formed on the surface of the substrate under the conditions of the raw material composition, temperature, and pressure shown in Table 1, to an average thickness shown in Table 6. Next, a B layer, whose composition is shown in Table 6, was formed on the surface of A under the conditions of the raw material composition, temperature, and pressure shown in Table 1, to an average thickness shown in Table 6. Next, a C layer, whose composition is shown in Table 6, was formed on the surface of B under the conditions of the raw material composition, temperature, and pressure shown in Table 1, to an average thickness shown in Table 6. This resulted in a lower layer consisting of three layers. Thereafter, the surface of the lower layer was subjected to an oxidation treatment under the conditions of the composition, temperature, and pressure shown in Table 2 for the time shown in Table 2. Next, α-type aluminum oxide (α-Al2O3) nuclei were formed on the surface of the oxidized lower layer under the conditions of the raw material composition, temperature, and pressure shown in Table 2 for the time shown in Table 2. Furthermore, under the conditions of the raw material composition, temperature, and pressure shown in Table 3, an intermediate layer (α-Al2O3 layer) with the composition shown in Table 6 was formed on the surface of the lower layer and the α-aluminum oxide (α-Al2O3) core to an average thickness shown in Table 6. Next, an upper layer was formed on the surface of the intermediate layer (α-Al2O3 layer). Specifically, in the first step of forming the upper layer, for Inventive Products 1 to 20 and 25 to 26 and Comparative Products 1 to 11 and 13 to 16, an X layer (adhesion layer) with the composition shown in Table 7 was formed on the surface of the α-Al2O3 layer under the conditions of the raw material composition, temperature, and pressure shown in Table 4 to an average thickness shown in Table 7. For invention products 21 to 24, the first step of forming the upper layer was carried out for 20 minutes under the conditions of the raw material composition, temperature, and pressure shown in Table 4, and a portion (average thickness: approximately 0.2 μm) of the Y layer (TiCN layer) whose composition is shown in Table 7 was formed on the surface of the intermediate layer (α-Al2O3 layer). For comparison product 12, the first step of forming the upper layer was not carried out. Next, as the second step of forming the upper layer, a Y layer whose composition is shown in Table 7 was formed on the surface of the X layer or the surface of the intermediate layer (α-Al2O3 layer) under the conditions of the raw material composition, temperature, and pressure shown in Table 5, to the average thickness shown in Table 7.For invention products 21 to 24, a Y layer (TiCN layer) having the composition shown in Table 7 was formed on the surface of the intermediate layer (α-Al2O3 layer) so that the combined average thickness of the first and second steps for forming the upper layer would be as shown in Table 7. Furthermore, for invention products 5 to 10, 14 to 16, 20, 23, and 24 and comparative products 1 to 3, 5 to 9, 12, 14, and 15, a Z layer (outermost layer) having the composition shown in Table 7 was formed on the surface of the Y layer under the conditions of raw material composition, temperature, and pressure shown in Table 1. In this way, coated cutting tools 1 to 26 and comparative products 1 to 15 were obtained.

[0073] The thickness of each layer of the sample was determined as follows: using FE-SEM, the thickness was measured at three locations on the cross section of the coated cutting tool, located 50 μm from the cutting edge ridge toward the center of the flank, and the arithmetic mean value was calculated as the average thickness. The composition of each layer of the obtained sample was measured using EDS on the cross section of the coated cutting tool, located 50 μm from the cutting edge ridge toward the center of the flank.

[0074] [Table 1]

[0075] [Table 2]

[0076] [Table 3]

[0077] [Table 4]

[0078] [Table 5]

[0079] [Table 6]

[0080] [Table 7]

[0081] [RSA and RSB] RSA and RSB were calculated as follows: In the obtained sample, a cross section of the upper TiCN layer was exposed in a direction parallel to the surface of the substrate at a position where 80% of the average thickness of the TiCN layer in the upper layer remained from the substrate side. The obtained cross section was mirror-polished, and the mirror-polished surface was observed with a field-emission scanning electron microscope (FE-SEM). Using an electron backscattering diffraction (EBSD) attached to the FE-SEM, the misorientation A between the normal to the exposed cross section and the normal to the (422) plane of the TiCN layer grains was measured. The sum of the cross-sectional areas of the analyzed upper TiCN layer in the region where the misorientation A was between 0 and 15 degrees (the sum of the cross-sectional areas of the upper TiCN layer where the misorientation A was between 0 and 45 degrees: RSA) was calculated. Total ) to 100% area was defined as RSA (unit: area%). Specifically, first, the cross-sectional area of ​​the region where the misorientation A is in the range of 0 degrees or more and less than 15 degrees and the cross-sectional area of ​​the region where the misorientation A is in the range of 0 degrees or more and less than 45 degrees were calculated. The total cross-sectional area of ​​the region where the misorientation A is in the range of 0 degrees or more and less than 45 degrees is 100% area. Of these cross-sectional areas based on misorientation A, the total cross-sectional area of ​​the region where the misorientation A is in the range of 0 degrees or more and less than 15 degrees was calculated as RSA. Total The RSA was expressed as a ratio to the normal of the exposed cross section. Similarly, the misorientation B between the normal of the exposed cross section and the normal of the (220) plane of the grains of the TiCN layer was measured using EBSD attached to the FE-SEM. The cross-sectional area of ​​the region where the misorientation B is 0 degrees or more and less than 15 degrees is the sum of the cross-sectional areas of the TiCN layer in the upper layer analyzed (the sum of the cross-sectional areas of the TiCN layer in the upper layer where the misorientation B is in the range of 0 degrees or more and 45 degrees or less: RSB Total) to 100% area was defined as RSB (unit: area%). Specifically, first, the cross-sectional area of ​​the region where the misorientation B is in the range of 0 degrees or more and less than 15 degrees and the cross-sectional area of ​​the region where the misorientation B is in the range of 0 degrees or more and less than 45 degrees were calculated. The total cross-sectional area of ​​the region where the misorientation B is in the range of 0 degrees or more and less than 45 degrees is 100% area. Of these cross-sectional areas based on misorientation B, the total cross-sectional area of ​​the region where the misorientation B is in the range of 0 degrees or more and less than 15 degrees was defined as RSB. Total The RSB was expressed as a ratio to the σ. The measurement results are shown in Table 8 below. The EBSD measurements were performed as follows: The sample was placed in the FE-SEM. The sample was irradiated with an electron beam at an incident angle of 70°, an accelerating voltage of 15 kV, and a probe current of 1.0 nA. The misorientation and cross-sectional area of ​​each grain were measured using EBSD settings of a measurement range of 120 μm × 120 μm and a step size (distance between measurement points) of 0.05 μm. The cross-sectional area of ​​the upper TiCN layer within the measurement range was calculated as the sum of the pixels corresponding to that area. In other words, the total cross-sectional area of ​​each region based on misorientation A and B was calculated by counting the pixels occupied by the cross-sections of the regions corresponding to each misorientation range and converting them to area. Similar EBSD measurements were performed in a total of three fields within the above measurement range, and the average of each area was calculated. The RSA and RSB were calculated from the average values ​​obtained.

[0082] [Average diameter of each region] The average diameter of region A was determined by calculating the equivalent circle diameter for each region, and the area average of the equivalent circle diameters was calculated as the "average diameter of region A." Specifically, it was calculated as follows. EBSD measurements were performed in a total of three fields of view, with a measurement range of 120 μm × 120 μm and an EBSD setting of 0.05 μm step size (distance between measurement points). A region surrounded by the boundary between measurement points where the misorientation A was 0 degrees or more and less than 15 degrees and the other measurement points, where the misorientation A was 0 degrees or more and less than 15 degrees, was defined as one region A, and the cross-sectional area occupied by each region A was calculated. The diameter of each region A was determined as the diameter of the circle having the same area as the obtained cross-sectional area. The area average diameter of the diameters of region A included in the measurement range was determined as the average diameter of region A. The measurement method for the "average diameter of region B" was the same as that for the average diameter of region A, except that the specified boundary was the "boundary between the measurement point where misorientation B was 0 degrees or more and less than 15 degrees and the other measurement points," and the specified region was the "region where misorientation B was 0 degrees or more and less than 15 degrees." The results are shown in Table 8 below.

[0083] [Average particle size of TiCN layer] The average particle size of the particles in the TiCN layer was calculated by determining the circle-equivalent diameter for each particle and averaging the area. Specifically, it was calculated as follows. EBSD measurements were performed in a total of three fields of view, with a measurement range of 120 μm × 120 μm and an EBSD step size (distance between measurement points) of 0.05 μm. The boundaries between measurement points with an orientation difference of 5° or more were considered to be grain boundaries. The area surrounded by a grain boundary was defined as one particle, and the cross-sectional area occupied by each particle was calculated. The diameter of a circle having the same area as the obtained cross-sectional area was considered to be the particle size of each particle. The area-average diameter of the particle sizes of all particles included in the measurement range was considered to be the average particle size of the particles in the TiCN layer. The results are shown in Table 8 below.

[0084] [Table 8]

[0085] [Texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-Al2O3 layer] X-ray diffraction measurements were performed on the resulting samples using Cu-Kα radiation with a 2θ / θ focusing optical system under the following conditions: output: 45 kV, 200 mA; incident Soller slit: 5°; divergence vertical slit: 2 / 3°; divergence vertical limiting slit: 5 mm; scattering slit: 8 mm; receiving Soller slit: 5°; receiving slit: 10 mm; detector: D / tex ultra; scan mode: continuous; sampling width: 0.01°; scan speed: 12° / min; 2θ measurement range: 25°–140°. A Rigaku Corporation X-ray diffractometer (model “SmartLab”) was used. The peak intensity of each crystal plane in the α-AlO layer in the intermediate layer was determined from the X-ray diffraction pattern. The texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-AlO layer, expressed by the following formula (iii), was calculated from the peak intensity of each crystal plane. The results are shown in Table 9.

number

[0086] [Table 9]

[0087] Using the obtained invention products 1 to 26 and comparison products 1 to 15, cutting test 1 and cutting test 2 were carried out under the following conditions. Cutting test 1 was a test to evaluate wear resistance and chipping resistance, and cutting test 2 was a test to evaluate fracture resistance. The results of each cutting test are shown in Table 10.

[0088] [Cutting test 1] Work material: SCM415, Workpiece shape: Round bar with two equally spaced grooves on the outer surface, Cutting speed: 240m / min, Cutting depth: 1.5mm, Feed: 0.20mm / rev, Coolant: Water-soluble coolant, Evaluation items: The tool life was measured when the sample was chipped or the maximum flank wear width reached 0.3 mm. The machining time until the tool life was reached was measured. In addition, the damage state after 10 minutes of machining was confirmed using an SEM.

[0089] [Cutting test 2] Work material: S45C, Workpiece shape: Round bar with four equally spaced grooves on the outer surface, Cutting speed: 180m / min, Cutting depth: 1.5mm, Feed: 0.25mm / rev, Coolant: Water-soluble coolant, Evaluation items: The time when the sample was chipped was regarded as the tool life, and the number of impacts until the tool life was reached was measured.

[0090] In Cutting Test 1, the machining time until the end of tool life was evaluated as "A" for 37 minutes or more, "B" for 25 minutes or more but less than 37 minutes, and "C" for less than 25 minutes. In Cutting Test 2, the cumulative number of impacts until the end of tool life was evaluated as "A" for 15,000 or more, "B" for 10,000 or more but less than 15,000, and "C" for less than 10,000. In this evaluation, "A" indicates the best, followed by "B" for best, and "C" for worst. The more A or B, the better the cutting performance. The evaluation results are shown in Table 10. Comparative Product 15 broke before the 10-minute machining period was completed, so it was marked "-."

[0091] [Table 10]

[0092] From the results shown in Table 10, the inventive product was evaluated as either "A" or "B" in both Cutting Test 1 and Cutting Test 2. On the other hand, the comparative product was evaluated as "C" in both or either the chipping test and the wear test. Therefore, it can be seen that the wear resistance, chipping resistance, and fracture resistance of the inventive product are generally superior to those of the comparative product.

[0093] From the above results, it was found that the inventive product has excellent wear resistance, chipping resistance and fracture resistance, resulting in a long tool life. [Industrial Applicability]

[0094] The coated cutting tool of the present invention has excellent wear resistance, chipping resistance and fracture resistance, and can therefore extend the tool life compared to conventional tools, and from this perspective, has industrial applicability. [Explanation of symbols]

[0095] 1...substrate, 2...lower layer, 3...intermediate layer, 4...upper layer, 5...coating layer, 6...coated cutting tool.

Claims

1. A coated cutting tool comprising a substrate and a coating layer formed on a surface of the substrate, the coating layer includes a lower layer, an intermediate layer, and an upper layer in this order from the substrate side toward the surface side of the coating layer, the lower layer includes a Ti compound layer made of a Ti compound of Ti and at least one element selected from the group consisting of C, N, O, and B; The intermediate layer is made of α-type aluminum oxide. 2 O 3 layer, the upper layer includes a TiCN layer made of Ti carbonitride; The average thickness of the entire coating layer is 8.5 μm or more and 30.0 μm or less, The upper layer has an average thickness of 1.0 μm or more and 6.0 μm or less, The upper TiCN layer satisfies the conditions represented by the following formulas (i) and (ii), 30≦RSA≦70 (i) (In formula (i), RSA is the percentage (unit: area %) of the total cross-sectional area of ​​a region A in which the misorientation A, which is the angle (unit: degree) between the normal to the cross-section of the TiCN layer of the upper layer in a direction parallel to the surface of the base material and the normal to the (422) plane of a particle of the TiCN layer, is 0 degrees or more and less than 15 degrees, when the total area of ​​the entire cross-section is taken as 100 area %).) 20≦RSB≦60 (ii) (In formula (ii), RSB is the ratio (unit: area %) of the total cross-sectional area of ​​a region B in which the misorientation B, which is the angle (unit: degree) between the normal to the cross-section of the TiCN layer of the upper layer in a direction parallel to the surface of the base material and the normal to the (220) plane of a particle of the TiCN layer, is 0 degrees or more and less than 15 degrees, when the total area of ​​the entire cross-section is taken as 100 area %).) A coated cutting tool, wherein the average diameter of the region B in the upper TiCN layer is less than 5.0 μm.

2. 2. The coated cutting tool according to claim 1, wherein the average diameter of the region B in the upper TiCN layer is 1.0 μm or more.

3. 3. The coated cutting tool according to claim 1, wherein the average diameter of the regions A in the upper TiCN layer is 5.0 μm or more and 30.0 μm or less.

4. 3. The coated cutting tool according to claim 1, wherein the average grain size of the grains in the upper TiCN layer is 0.3 [mu]m or more and 1.2 [mu]m or less.

5. In the intermediate layer, α-Al represented by the following formula (iii) 2 O 3 3. The coated cutting tool according to claim 1, wherein a texture coefficient TC(0,0,12) of the (0,0,12) plane of the layer is 5.0 or more and 8.9 or less. [Equation 1] (In formula (iii), I(h, k, l) represents the α-Al contained in the intermediate layer. 2 O 3 is the peak intensity by X-ray diffraction measured on the (h, k, l) plane of the layer, and I 0 (h, k, l) is the standard diffraction intensity of the (h, k, l) plane of α-type aluminum oxide according to JCPDS card number 10-0173, and (h, k, l) refers to nine crystal planes: (0, 1, 2), (1, 0, 4), (1, 1, 3), (0, 2, 4), (1, 1, 6), (2, 1, 4), (3, 0, 0), (0, 2, 10), and (0, 0, 12).

6. 3. The coated cutting tool according to claim 1, wherein the intermediate layer has an average thickness of 3.0 μm or more and 15.0 μm or less.

7. 3. The coated cutting tool according to claim 1, wherein the lower layer has an average thickness of 3.0 μm or more and 15.0 μm or less.

8. 3. The coated cutting tool according to claim 1, wherein the substrate is any one of cemented carbide, cermet, ceramics, and cubic boron nitride sintered body.

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