Coated cutting tool

Abstract

This invention provides a coated cutting tool with excellent chipping resistance and wear resistance, thereby extending tool life. The coated cutting tool includes a substrate and a coating layer formed on the surface of the substrate. The coating layer sequentially includes a lower layer, an intermediate layer, and an upper layer from the substrate side toward the surface side of the coating layer. The lower layer includes one or more layers of a specific Ti compound, and the intermediate layer includes an α-Al₂O₃ layer. The upper layer includes one or more layers of a specific Ti compound, and at least one of the Ti compound layers in the upper layer is a TiCN layer. The average thickness of the upper layer is 1.00 μm or more and 6.50 μm or less. The upper layer satisfies the conditions shown in equation (i): 25 ≤ RSA₁ < 70, and equation (ii): 25 ≤ RSA₂ < 70.

Description

Technical Field

[0001] This invention relates to a coated cutting tool. Background Technology

[0002] Conventionally, a coating layer with a total thickness of 3–20 μm is deposited on the surface of a cemented carbide substrate using chemical vapor deposition to obtain a coated cutting tool for machining steel or cast iron. Common examples of such coating layers include single layers or multilayers composed of one or more of a type of Ti, such as carbides, nitrides, carbonitrides, carbon oxides, carbonitrides, and aluminum oxide (Al₂O₃).

[0003] Patent Document 1 describes a coated cemented carbide, which is a cemented carbide with a coating layer on its surface. The coating layer, from the cemented carbide side, sequentially comprises an inner layer, a middle layer, and an outer layer. The inner layer includes at least one layer selected from carbides, nitrides, borides, oxides, and their solid solutions from groups IVa, Va, and VIa of the periodic table. The middle layer includes at least one layer selected from alumina, zirconium oxide, and their solid solutions. The outer layer includes a titanium carbonitride layer with a columnar structure and includes at least one layer selected from carbides, nitrides, borides, oxides, their solid solutions, and alumina from groups IVa, Va, and VIa of the periodic table. In the cross-sectional microstructure of the coated cemented carbide, the relationship between the maximum roughness Amax of the surface portion of the middle layer and the maximum roughness Bmax of the surface portion of the columnar titanium carbonitride layer in the outer layer satisfies Equation 1:

[0004] (Bmax / Amax)<1…………………Equation 1

[0005] (Where, 0.5μm < Amax < 4.5μm, 0.5μm ≤ Bmax ≤ 4.5μm)

[0006] In addition, Patent Document 1 also describes: Formula 3 shows the orientation index TC of the titanium carbonitride layer with columnar structure in the outer layer, wherein the orientation index TC is the largest in any one of the (220) plane, (311) plane, (331) plane, and (422) plane, and its maximum value is 1.3 or more and 3.5 or less.

[0007] [Formula 1]

[0008]

[0009] I(hkl), I(h x k y l z ): The measured (hkl), (h x k y lz Diffraction intensity of the surface

[0010] Io(hkl), Io(h x k y l z ): Based on ASTM standards, (hkl) and (h x k y l z Average value of diffraction intensity of TiC and TiN powders on the surface

[0011] (hkl), (h x k y l z ): (111), (200), (220), (311), (331), (420), (422), (511) Eight sides

[0012] Existing technical documents

[0013] Patent documents

[0014] Patent Document 1: International Publication No. 2000 / 079022 (WO2000079022A1)

[0015] Technical issues

[0016] In recent years, the increasing speed, high feed rate, and deep cut of machining have led to greater demands for improved tool resistance and wear resistance. Especially in recent years, more and more machining processes, such as high-speed cutting of steel, place heavy loads on coated cutting tools. Under these demanding cutting conditions, conventional tools lack sufficient resistance and wear resistance, failing to extend tool life. While the coated cemented carbide described in Patent Document 1 exhibits excellent adhesion between the intermediate and outer layers, it lacks sufficient wear resistance, leaving room for improvement.

[0017] This invention was made in response to the above-mentioned problems, and its purpose is to provide a coated cutting tool that has excellent chip resistance and wear resistance, thereby extending the tool life. Summary of the Invention

[0018] Based on the above viewpoints, the inventors have repeatedly studied ways to extend the life of coated cutting tools and found that by adopting a specific structure, the chipping resistance and wear resistance can be improved, thereby extending the tool life, thus completing this invention.

[0019] The content of this invention is as follows: [1]

[0021] The present invention provides a coated cutting tool, including a substrate and a coating layer formed on the surface of the substrate, wherein the coating layer includes a lower layer, an intermediate layer and an upper layer in sequence from the substrate side toward the surface side of the coating layer;

[0022] The lower layer includes one or more Ti compound layers composed of Ti compounds, wherein the Ti compounds are composed of Ti and at least one element selected from C, N, O and B;

[0023] The intermediate layer includes an α-Al2O3 layer composed of α-Al2O3;

[0024] The upper layer comprises one or more Ti compound layers composed of Ti compounds, wherein the Ti compounds are composed of Ti and at least one element selected from C, N and O, and at least one of the Ti compound layers in the upper layer is a TiCN layer, and the average thickness of the upper layer is more than 1.00 μm and less than 6.50 μm;

[0025] In the upper layer, the conditions shown in equations (i) and (ii) below are satisfied:

[0026] 25≤RSA1<70………………(i)

[0027] In equation (i), in the cross section perpendicular to the surface of the substrate in the upper layer, if the total area of ​​the cross section is set to 100% area, the orientation difference A is the angle between the normal of the (220) plane of each particle with a cubic crystal structure and the normal of the surface of the substrate. The unit of the angle is degrees. RSA1 refers to the proportion of the cross section area of ​​the region where the orientation difference A is greater than 0 degrees and less than 10 degrees. The unit of the proportion is area%.

[0028] 25≤RSA2<70………………(ii)

[0029] In equation (ii), in the cross section perpendicular to the surface of the substrate in the upper layer, if the total area of ​​the cross section is set to 100% of the area, the orientation difference A is the angle between the normal of the (220) plane of each particle with a cubic crystal structure and the normal of the surface of the substrate. The unit of the angle is degrees. RSA2 refers to the proportion of the cross section area of ​​the region with an orientation difference A of more than 20 degrees and less than 30 degrees. The unit of the proportion is area. [2]

[0031] According to the coating cutting tool of [1], in the upper layer, RSA1 and RSA2 together account for more than 60% and less than 90% of the area. [3]

[0033] According to the coating cutting tool of [1] or [2], the upper layer is connected to the middle layer, and in the upper layer, the sealing layer on the side connected to the middle layer includes at least one layer selected from TiCO, TiON and TiCNO, and the average thickness of the sealing layer is more than 0.05 μm and less than 1.50 μm. [4]

[0035] According to the coating cutting tool of [1] or [2], in the intermediate layer, the texture factor TC(0,0,12) of the (0,0,12) plane of the α-Al2O3 layer shown in the following formula (1) is 5.9 or more and 8.9 or less:

[0036] [Formula 2]

[0037]

[0038] In equation (1), I(h,k,l) ​​is the intensity of the peak produced by X-ray diffraction obtained by measuring the (h,k,l) ​​plane of the α-Al2O3 layer, and I0(h,k,l) ​​is the standard diffraction intensity of the (h,k,l) ​​plane of α-All2O3 obtained based on JCPDS card number 10-0173. (h,k,l) ​​refers to the 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). [5]

[0040] According to the coating cutting tool of [1] or [2], the average thickness of the intermediate layer is above 3.00 μm and below 15.00 μm. [6]

[0042] According to the coating cutting tool of [1] or [2], the average thickness of the lower layer is above 3.00 μm and below 15.00 μm. [7]

[0044] According to the coating cutting tool of [1] or [2], the overall average thickness of the coating layer is more than 10.00 μm and less than 30.00 μm.

[0045] The coated cutting tool provided by this invention has excellent chip resistance and wear resistance, thereby extending tool life. Attached Figure Description

[0046] Figure 1 This is a cross-sectional schematic diagram of a covered cutting tool provided by the present invention.

[0047] Explanation of main component symbols

[0048] Substrate 1

[0049] Lower layer 2

[0050] Intermediate layer 3

[0051] Upper 4

[0052] Coating layer 5

[0053] Covered cutting tool 6 Detailed Implementation

[0054] The embodiments of the present invention (hereinafter referred to as "this embodiment") will now be described in detail with reference to the accompanying drawings, but the present invention is not limited to the following embodiments. Various modifications can be made to the present invention without departing from its spirit. Furthermore, unless otherwise specified, the positional relationships such as up, down, left, and right in the accompanying drawings are based on the positional relationships shown in the drawings. Moreover, the scale of the accompanying drawings is not limited to the scale shown in the drawings.

[0055] The coated cutting tool provided in this embodiment includes a substrate and a coating layer formed on the surface of the substrate. The coating layer includes a lower layer, an intermediate layer, and an upper layer sequentially from the substrate side toward the surface side of the coating layer. The lower layer includes one or more Ti compound layers composed of Ti compounds, wherein the Ti compounds are composed of Ti and at least one element selected from C, N, O, and B. The intermediate layer includes an α-Al2O3 layer composed of α-Al2O3. The upper layer includes one or more Ti compound layers composed of Ti compounds, wherein the Ti compounds are composed of Ti and at least one element selected from C, N, and O, and at least one of the Ti compound layers in the upper layer is a TiCN layer, and the average thickness of the upper layer is 1.00 μm or more and 6.50 μm or less. In the upper layer, the conditions shown in the following formulas (i) and (ii) are satisfied:

[0056] 25≤RSA1<70……………… (i)

[0057] In equation (i), in the cross section perpendicular to the surface of the substrate in the upper layer, if the total area of ​​the cross section is set to 100% area, the orientation difference A is the angle (unit: degree) between the normal of the (220) plane of each particle with a cubic crystal structure and the normal of the surface of the substrate. RSA1 refers to the proportion of the cross section area of ​​the region with an orientation difference A of 0 degrees or more and less than 10 degrees (unit: area%).

[0058] 25≤RSA2<70………………(ii)

[0059] In equation (ii), in the cross section perpendicular to the surface of the substrate in the upper layer, if the total area of ​​the cross section is set to 100% area, the orientation difference A is the angle (unit: degree) between the normal of the (220) plane of each particle with a cubic crystal structure and the normal of the surface of the substrate, and RSA2 refers to the proportion of the cross section area of ​​the region with an orientation difference A of 20 degrees or more and less than 30 degrees (unit: area%).

[0060] The coated cutting tool provided in this embodiment, by including the above-described structure, can improve chipping resistance and wear resistance, thereby extending tool life. The main factors contributing to the improved chipping resistance and wear resistance of the coated cutting tool provided in this embodiment are as follows, but the present invention is not limited to any of these factors. First, since the average thickness of the upper layer is 1.00 μm or more, the wear resistance of the coated cutting tool provided in this embodiment is improved. On the other hand, since the average thickness of the upper layer is 6.50 μm or less, the adhesion between the upper layer and the intermediate layer is improved, resulting in excellent chipping resistance for the coated cutting tool provided in this embodiment. Furthermore, since RSA1 is 25% or more, the adhesion between the upper layer and the intermediate layer is excellent, resulting in excellent chipping resistance for the coated cutting tool provided in this embodiment. On the other hand, since RSA1 is less than 70% of the area, the coated cutting tool provided in this embodiment has excellent wear resistance. Additionally, since RSA2 is 25% or more of the area, the coated cutting tool provided in this embodiment has excellent wear resistance. On the one hand, since RSA2 is less than 70% of the area, the coated cutting tool provided in this embodiment is easy to manufacture. In this way, by combining these structures, the chipping resistance and wear resistance of the coated cutting tool provided in this embodiment are improved, thereby extending the tool life.

[0061] Figure 1 This is a cross-sectional schematic diagram of a coated cutting tool provided in this embodiment. The coated cutting tool 6 includes a substrate 1 and a coating layer 5 formed on the surface of the substrate 1. In the coating layer 5, the lower layer 2, the middle layer 3, and the upper layer 4 are stacked sequentially upward from the substrate side.

[0062] The coated cutting tool provided in this embodiment includes a substrate and a coating layer formed on the surface of the substrate. Specifically, the coated cutting tool can be a replaceable cutting insert, a drill bit, or an end mill, etc., used for milling or turning operations.

[0063] The substrate used in this embodiment is not particularly limited as long as it can be used as a substrate for coating cutting tools. For example, the substrate can be cemented carbide, cermet, ceramic, cubic boron nitride sintered body, diamond sintered body, or high-speed steel, etc. Among them, if the substrate is any one of cemented carbide, cermet, ceramic, and cubic boron nitride sintered body, the wear resistance and chipping resistance are better, so these materials are preferred. Based on the same point of view, cemented carbide is more preferred as the substrate.

[0064] It should be noted that the surface of the substrate can also be modified. For example, when the substrate is made of cemented carbide, a de-β layer can be formed on its surface. Additionally, when the substrate is made of cermet, a hardened layer can be formed on its surface. Even with such surface modification, the effects of the present invention can still be achieved.

[0065] Preferably, the coating layer used in this embodiment has an overall average thickness of 10.00 μm or more and 30.00 μm or less. The coated cutting tool provided in this embodiment tends to exhibit improved wear resistance when the overall average thickness of the coating layer is 10.00 μm or more, and tends to have excellent chipping resistance and damage resistance when the overall average thickness of the coating layer is 30.00 μm or less. Based on the same viewpoint, the overall average thickness of the coating layer is more preferably 13.50 μm or more and 26.45 μm or less, and even more preferably 14.70 μm or more and 25.05 μm or less.

[0066] It should be noted that the average thickness of each layer and the overall coating layer in the coating cutting tool provided in this embodiment can be obtained by measuring the thickness of each layer or the overall coating layer at three or more cross-sections and calculating their arithmetic mean.

[0067] [Lower Level]

[0068] The lower layer used in this embodiment includes one or more Ti compound layers composed of Ti compounds, wherein the Ti compound is composed of Ti and at least one element selected from C, N, O and B. If the cutting tool is coated with a lower layer between the substrate and the intermediate layer including the α-Al2O3 layer, the wear resistance and adhesion will be improved.

[0069] The Ti compound layer in the lower layer is not particularly limited. For example, TiC layer composed of TiC, TiN layer composed of TiN, TiCN layer composed of TiCN, TiCO layer composed of TiCO, TiCNO layer composed of TiCNO, TiON layer composed of TiON, and TiB2 layer composed of TiB2 can be listed.

[0070] The lower layer can consist of one layer or multiple layers (e.g., two or three layers), but is preferably composed of multiple layers, more preferably two or three layers, and even more preferably three layers. From the viewpoint of further improving wear resistance and adhesion, the Ti compound constituting the Ti compound layer of the lower layer is preferably at least one selected from TiN, TiC, TiCN, TiCNO, TiON, and TiB2. Furthermore, if at least one layer of the lower layer is a TiCN layer, the wear resistance of the coated cutting tool provided in this embodiment can be further improved; therefore, at least one layer of the lower layer is preferably a TiCN layer. When the lower layer consists of three layers, a TiC layer or a TiN layer can be formed on the surface of the substrate as the first layer, a TiCN layer as the second layer on the surface of the first layer, and a TiCNO layer or a TiCO layer as the third layer on the surface of the second layer. Alternatively, a TiN layer can be formed on the surface of the substrate as the first layer, a TiCN layer as the second layer on the surface of the first layer, and a TiCNO layer as the third layer, thereby forming the lower layer.

[0071] Preferably, the average thickness of the lower layer used in this embodiment is 3.00 μm or more and 15.00 μm or less. Since the average thickness of the lower layer is 3.00 μm or more, the coated cutting tool provided in this embodiment tends to have improved wear resistance. On the other hand, since the average thickness of the lower layer is 15.00 μm or less, the coated cutting tool provided in this embodiment tends to have improved chipping resistance and damage resistance. Based on the same viewpoint, the average thickness of the lower layer is more preferably 3.50 μm or more and 12.50 μm or less, and even more preferably 4.50 μm or more and 10.30 μm or less.

[0072] From the viewpoint of further improving wear resistance and chip resistance, the average thickness of the TiC layer or TiN layer in the lower layer is preferably 0.05 μm or more and 2.00 μm or less. Based on the same viewpoint, the average thickness of the TiC layer or TiN layer in the lower layer is more preferably 0.10 μm or more and 1.80 μm or less, and even more preferably 0.20 μm or more and 1.50 μm or less.

[0073] From the viewpoint of further improving wear resistance and chip resistance, the average thickness of the TiCN layer in the lower layer is preferably 2.00 μm or more and 15.00 μm or less. Based on the same viewpoint, the average thickness of the TiCN layer in the lower layer is more preferably 2.50 μm or more and 14.50 μm or less, and even more preferably 3.00 μm or more and 12.00 μm or less.

[0074] From the viewpoint of further improving wear resistance and chip resistance, the average thickness of the TiCNO layer or TiCO layer in the lower layer is preferably 0.10 μm or more and 1.00 μm or less. Based on the same viewpoint, the average thickness of the TiCNO layer or TiCO layer in the lower layer is more preferably 0.20 μm or more and 0.50 μm or less.

[0075] The lower Ti compound layer is composed of Ti compounds, which consist of Ti and at least one element selected from C, N, O and B. However, as long as it serves the function of the lower layer, it may also contain trace amounts of components other than the aforementioned elements.

[0076] [Middle Layer]

[0077] The intermediate layer used in this embodiment includes an α-Al2O3 layer composed of α-Al2O3.

[0078] In this embodiment, the average thickness of the intermediate layer is preferably 3.00 μm or more and 15.00 μm or less. If the average thickness of the intermediate layer is 3.00 μm or more, there is a tendency for improved wear resistance; furthermore, TC (0, 0, 12, as described later) is easier to control. Additionally, if the average thickness of the intermediate layer is 15.00 μm or less, there is a tendency for excellent adhesion between the upper and intermediate layers and excellent chipping resistance. Based on the same viewpoint, the average thickness of the intermediate layer is more preferably 3.20 μm or more and 14.60 μm or less, and even more preferably 4.00 μm or more and 13.00 μm or less.

[0079] In the intermediate layer of the coated cutting tool provided in this embodiment, the texture coefficient TC(0, 0, 12) of the (0, 0, 12) plane of the α-Al2O3 layer shown by the following formula (1) is preferably 5.9 or more and 8.9 or less:

[0080] [Formula 3]

[0081]

[0082] In equation (1), I(h,k,l) ​​is the intensity of the peak produced by X-ray diffraction obtained by measuring the (h,k,l) ​​plane of the α-Al2O3 layer, and I0(h,k,l) ​​is the standard diffraction intensity of the (h,k,l) ​​plane of α-All2O3 obtained based on JCPDS card number 10-0173. (h,k,l) ​​refers to the 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).

[0083] Regarding the intermediate layer, by making the texture coefficient TC(0,0,12) of the (0,0,12) facet of the α-Al2O3 layer shown in Formula (1) above 5.9 or more, the coated cutting tool provided in this embodiment tends to have excellent wear resistance, and in addition, the RSA2 value can be improved. On the other hand, regarding the intermediate layer, if the texture coefficient TC(0,0,12) of the (0,0,12) facet of the α-Al2O3 layer shown in Formula (1) above is 8.9 or less, the coated cutting tool provided in this embodiment is easy to manufacture. Based on the same viewpoint, the texture coefficient TC(0,0,12) of the (0,0,12) facet of the α-Al2O3 layer shown in Formula (1) above is more preferably 6.3 or more and 8.9 or less, and even more preferably 7.0 or more and 8.9 or less.

[0084] It should be noted that, in this embodiment, the texture coefficient TC(0,0,12) of the (0,0,12) plane of the α-Al2O3 layer can be obtained by the method described in the embodiments described later.

[0085] The intermediate layer only needs to be composed of α-alumina (α-Al2O3). As long as the effect of the present invention is achieved, it may or may not include components other than α-alumina (α-Al2O3).

[0086]

upper layer

[0087] The upper layer used in this embodiment includes one or more Ti compound layers composed of Ti compounds. The Ti compounds are composed of Ti and at least one element selected from C, N, and O, and at least one of the Ti compound layers in the upper layer is a TiCN layer. Furthermore, the upper layer used in this embodiment satisfies the conditions shown by equations (i) and (iii) below:

[0088] 25≤RSA1<70………………(i)

[0089] In equation (i), in the cross section perpendicular to the surface of the substrate in the upper layer, if the total area of ​​the cross section is set to 100% area, the orientation difference A is the angle (unit: degree) between the normal of the (220) plane of each particle with a cubic crystal structure and the normal of the surface of the substrate. RSA1 refers to the proportion of the cross section area of ​​the region with an orientation difference A of 0 degrees or more and less than 10 degrees (unit: area%).

[0090] 25≤RSA2<70………………(ii)

[0091] In equation (ii), in the cross section perpendicular to the surface of the substrate in the upper layer, if the total area of ​​the cross section is set to 100% area, the orientation difference A is the angle (unit: degree) between the normal of the (220) plane of each particle with a cubic crystal structure and the normal of the surface of the substrate, and RSA2 refers to the proportion of the cross section area of ​​the region with an orientation difference A of 20 degrees or more and less than 30 degrees (unit: area%).

[0092] By making RSA1 25% or more, excellent adhesion exists between the upper and middle layers, and the coated cutting tool provided in this embodiment exhibits excellent chipping resistance. On the other hand, by making RSA1 less than 70% of the area, the coated cutting tool provided in this embodiment exhibits excellent wear resistance. Based on the same viewpoint, RSA1 is more preferably 27% or more and 61% or less, and even more preferably 30% or more and 48% or less. Furthermore, by making RSA2 25% or more of the area, the coated cutting tool provided in this embodiment exhibits excellent wear resistance. On the other hand, by making RSA2 less than 70% of the area, the coated cutting tool provided in this embodiment is easy to manufacture. Based on the same viewpoint, RSA2 is more preferably 26% or more and 65% or less, and even more preferably 28% or more and 53% or less.

[0093] Furthermore, in the upper layer of the coated cutting tool provided in this embodiment, the total area percentage of RSA1 and RSA2 is preferably 60% or more and 90% or less. When the total area percentage of RSA1 and RSA2 in the upper layer is 60% or more, the coated cutting tool provided in this embodiment tends to exhibit excellent chipping resistance and wear resistance. On the other hand, if the total area percentage of RSA1 and RSA2 in the upper layer is 90% or less, the coated cutting tool provided in this embodiment is easier to manufacture. Based on the same viewpoint, the total area percentage of RSA1 and RSA2 is more preferably 62% or more and 90% or less, and even more preferably 64% or more and 90% or less.

[0094] It should be noted that, in this embodiment, RSA1 and RSA2 can be obtained by the method described in the embodiments described later.

[0095] The upper layer used in this embodiment includes one or more Ti compound layers composed of Ti compounds, wherein the Ti compounds are composed of Ti and at least one element selected from C, N and O.

[0096] Furthermore, at least one of the upper Ti compound layers is a TiCN layer composed of TiCN. If at least one of the upper Ti compound layers is a TiCN layer, the wear resistance is improved; therefore, it is preferable that at least one of the upper Ti compound layers is a TiCN layer. Other Ti compound layers in the upper layer are not particularly limited; examples include TiC layers composed of TiC, TiN layers composed of TiN, TiCO layers composed of TiCO, TiCNO layers composed of TiCNO, and TiON layers composed of TiON.

[0097] The upper layer can consist of one layer or multiple layers (e.g., two or three layers). When the upper layer consists of multiple layers, the layer contacting the intermediate layer is preferably formed as the adhesive layer described later. Alternatively, other layers can be formed on the surface of the TiCN layer opposite to the substrate. When the upper layer consists of two layers, the TiCN layer can be formed as the first layer, and a TiN layer can be formed on the surface of the first layer as the second layer. Furthermore, when the upper layer consists of three layers, a TiCNO layer or a TiCO layer can be formed as the adhesive layer on the side contacting the intermediate layer, a TiCN layer can be formed on the surface of the adhesive layer as the second layer, and a TiN layer can be formed on the surface of the second layer as the third layer.

[0098] In this embodiment, the average thickness of the upper layer is 1.00 μm or more and 6.50 μm or less. By making the average thickness of the upper layer 1.00 μm or more, the wear resistance of the coated cutting tool provided in this embodiment is improved. On the other hand, by making the average thickness of the upper layer 6.50 μm or less, the adhesion between the upper layer and the intermediate layer is improved, and the coated cutting tool provided in this embodiment has excellent chipping resistance. Based on the same viewpoint, the average thickness of the upper layer is preferably 1.20 μm or more and 5.00 μm or less, more preferably 1.55 μm or more and 4.80 μm or less.

[0099] The average thickness of the TiCN layer in the upper layer is preferably 1.00 μm or more and 6.50 μm or less. By making the average thickness of the TiCN layer in the upper layer 1.00 μm or more, the coated cutting tool provided in this embodiment tends to have improved wear resistance. In addition, by making the average thickness of the TiCN layer in the upper layer 6.50 μm or less, the adhesion between the upper layer and the intermediate layer is improved, and the coated cutting tool provided in this embodiment tends to have excellent chipping resistance. Based on the same viewpoint, the average thickness of the TiCN layer in the upper layer is more preferably 1.50 μm or more and 5.00 μm or less, and even more preferably 2.00 μm or more and 4.80 μm or less.

[0100] In this embodiment, when the upper layer and the intermediate layer are in contact, the sealing layer (hereinafter also referred to as the "sealing layer") on the side of the upper layer that is in contact with the intermediate layer preferably includes at least one layer selected from TiCO, TiON, and TiCNO. If the upper layer used in this embodiment includes such a sealing layer, there is a tendency to improve the adhesion to the intermediate layer, and furthermore, RSA1 is easier to control. Based on the same viewpoint, the sealing layer is more preferably a TiCO layer or a TiCNO layer.

[0101] In this embodiment, the average thickness of the adhesive layer in the upper layer is preferably 0.05 μm or more and 1.50 μm or less. If the average thickness of the adhesive layer is 0.05 μm or more, the adhesion between the upper and middle layers is excellent, and the coated cutting tool provided in this embodiment tends to have excellent chipping resistance and also tends to easily increase RSA1. On the other hand, in the coated cutting tool provided in this embodiment, if the average thickness of the adhesive layer is 1.50 μm or less, the wear resistance tends to improve because the decrease in RSA2 can be suppressed. Based on the same viewpoint, the average thickness of the adhesive layer is more preferably 0.05 μm or more and 1.00 μm or less, and even more preferably 0.05 μm or more and 0.30 μm or less.

[0102] The upper Ti compound layer is composed of Ti compounds, which are composed of Ti and at least one element selected from C, N and O. However, as long as it plays the role of the upper layer, it may also contain trace amounts of components other than the above-mentioned elements.

[0103] Methods for forming the coating layer

[0104] For example, the layers constituting the coating layer in the coating cutting tool provided in this embodiment can be formed by the following method, but the method of forming each layer is not limited to this.

[0105] First, a lower layer consisting of one or more Ti compound layers is formed on the surface of a substrate. Next, the surface of the layer furthest from the substrate is oxidized. Then, an α-Al₂O₃ core is formed on the surface of the layer furthest from the substrate, and after core formation, an α-Al₂O₃ layer is formed. Finally, an upper layer consisting of one or more Ti compound layers is formed on the surface of the α-Al₂O₃ layer.

[0106] There are no particular limitations on the method for forming the Ti compound layer in the lower layer; for example, the following methods can be used.

[0107] 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. The raw material composition is: 5.0-10.0 mol% TiCl4, 20-60 mol% N2, and the remainder is H2. The temperature is set to 850-950℃ and the pressure is set to 350-450 hPa.

[0108] Ti compound layers consisting of Ti carbide layers (hereinafter also referred to as "TiC layers") can be formed by chemical vapor deposition. The raw material composition is: 1.5-3.5 mol% TiCl4, 3.5-5.5 mol% CH4, and the remainder is H2. The temperature is set to 950-1050℃ and the pressure is set to 70-80 hPa.

[0109] Ti compound layers consisting of Ti carbonitride layers (hereinafter also referred to as "TiCN layers") can be formed by chemical vapor deposition. The raw material composition is: 5.0-7.0 mol% TiCl4, 0.5-1.5 mol% CH3CN, and the remainder is H2. The temperature is set to 800-900℃ and the pressure is set to 70-90 hPa.

[0110] The Ti compound layer, consisting of a Ti carbon nitride oxide layer (hereinafter also referred to as the "TiCNO layer") in the lower layer, can be formed by chemical vapor deposition. The raw material composition is: 3.0-4.0 mol% TiCl4, 0.5-1.0 mol% CO, 30-40 mol% N2, and the remainder is H2. The temperature is set to 950-1050℃ and the pressure is set to 50-150 hPa.

[0111] Ti compound layers consisting of Ti carbon oxide layers (hereinafter also referred to as "TiCO layers") can be formed by chemical vapor deposition. The raw material composition is: 1.0-2.0 mol% TiCl4, 2.0-3.0 mol% CO, and the remainder H2. The temperature is set to 950-1050℃ and the pressure is set to 50-150 hPa.

[0112] In addition, the intermediate layer consisting of an α-Al2O3 layer (hereinafter also referred to as "Al2O3 layer") is formed, for example, by the following method.

[0113] First, the surface of the layer furthest from the substrate in the lower layer is oxidized (oxidation process). The raw material composition is: 0.1-0.5 mol% CO2, 0.05-0.15 mol% H2S, and the remainder is H2. The temperature is set to 900-950℃ and the pressure is set to 60-80 hPa. The oxidation treatment time is preferably 1-3 minutes.

[0114] Then, a core of the α-Al₂O₃ layer is formed by chemical vapor deposition (core formation process). The raw material composition is: 1.0–4.0 mol% AlCl₃, 0.05–2.0 mol% CO, 1.0–3.0 mol% CO₂, 2.0–3.0 mol% HCl, and the remainder H₂. The temperature is set to 900–950 °C, and the pressure is set to 60–80 hPa. The core formation process is preferably carried out for 3–30 minutes.

[0115] Next, an α-Al2O3 layer is formed by chemical vapor deposition (film formation process). The raw material composition is: 2.0-5.0 mol% AlCl3, 2.5-4.0 mol% CO2, 2.0-3.0 mol% HCl, 0.6-1.0 mol% H2S, and the remainder is H2. The temperature is set to 980-1020℃ and the pressure is set to 60-80 hPa.

[0116] In the intermediate layer, in order to control the texture factor TC(0, 0, 12) of the (0, 0, 12) plane of the α-Al2O3 layer shown in Equation (1) within the specific range mentioned above, this can be achieved, for example, by controlling the proportion of H2S in the gas composition during the film-forming process or by controlling the average thickness of the intermediate layer. More specifically, for example, by increasing the proportion of H2S in the gas composition during the film-forming process or by increasing the average thickness of the intermediate layer, the texture factor TC(0, 0, 12) of the (0, 0, 12) plane of the α-Al2O3 layer represented by Equation (1) tends to increase.

[0117] Furthermore, the method for forming the Ti compound layer in the upper layer is not particularly limited; for example, the following method can be used. First, if a close-fitting layer is formed on the side in contact with the intermediate layer (α-Al2O3 layer), the first step in forming the upper layer is to form a Ti compound layer on the surface of the α-Al2O3 layer. Next, the second step in forming the upper layer is to form a TiCN layer on the surface of the close-fitting layer. Furthermore, a Ti compound layer can also be formed on the surface of the TiCN layer.

[0118] As the first step in forming the upper layer, for example, when forming a TiCNO layer on the surface of an α-Al2O3 layer, chemical vapor deposition can be used. The raw material composition is: 9.0–11.0 mol% TiCl4, 0.5–1.0 mol% C2H4, 1.5–2.0 mol% CH3CN, 2.0–8.0 mol% CO, 15–25 mol% N2, with the remainder being H2. The temperature is set to 980–1020 °C, and the pressure is set to 80–100 hPa.

[0119] As the first step in forming the upper layer, for example, when forming a TiCN layer on the surface of an α-Al₂O₃ layer, chemical vapor deposition can be used. The raw material composition is: 10.0–12.0 mol% TiCl₄, 0.5–1.5 mol% C₂H₄, 1.5–2.5 mol% CH₃CN, 20–30 mol% N₂, with the remainder being H₂. The temperature is set to 980–1020 °C, and the pressure is set to 100–140 hPa. The preferred time for forming the TiCN layer is 2–8 minutes.

[0120] As the first step in forming the upper layer, for example, when forming a TiCO layer on the surface of an α-Al2O3 layer, chemical vapor deposition can be used. The raw material composition is: 8.0-10.0 mol% TiCl4, 0.3-0.7 mol% C2H4, 4.0-10.0 mol% CO, and the remainder is H2. The temperature is set to 980-1020℃ and the pressure is set to 60-80 hPa.

[0121] As the second step in forming the upper layer, the TiCN layer can be formed using chemical vapor deposition. The raw material composition is: 9.0–11.0 mol% TiCl4, 0.5–1.5 mol% CH4, 1.5–2.5 mol% CH3CN, 15–25 mol% N2, with the remainder being H2. The temperature is set to 930–970 °C, and the pressure is set to 70–120 hPa.

[0122] Furthermore, when forming a TiN layer on the surface of the TiCN layer, a chemical vapor deposition method can be used. The raw material composition is: 5.0-10.0 mol% TiCl4, 20-60 mol% N2, and the remainder is H2. The temperature is set to 950-1050℃ and the pressure is set to 300-400 hPa.

[0123] In the upper layer, to control RSA1 within the aforementioned specific range, this can be achieved, for example, by controlling the proportion of C2H4 or CO in the gas composition of the first step in forming the upper layer. Additionally, if the upper layer includes a sealing layer, this can be achieved by controlling the average thickness of the sealing layer. More specifically, for example, by increasing the proportion of C2H4 or CO in the gas composition of the first step in forming the upper layer, RSA1 can tend to increase. Furthermore, for example, if the upper layer includes a sealing layer, by increasing the average thickness of the sealing layer, RSA1 can tend to increase.

[0124] In the upper layer, to control RSA2 within the aforementioned specific range, this can be achieved, for example, by controlling the proportion of CH4 or CH3CN in the gas composition of the second process forming the upper layer. More specifically, by increasing the proportion of CH4 or CH3CN in the gas composition of the second process forming the upper layer, it is possible to make RSA2 tend to increase.

[0125] Furthermore, when the first step of forming the upper layer is not performed, or when the various conditions in the first step of forming the upper layer are outside the above range, RSA2 tends to increase when the second step of forming the upper layer is performed under the above conditions. In addition, the proportion of azimuth differences A of 30 degrees or more and 45 degrees or less also tends to increase.

[0126] 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 microstructure of the coated cutting tool using an optical microscope, scanning electron microscope (SEM), or field emission scanning electron microscope (FE-SEM). It should be noted that the average thickness of each layer in the coated cutting tool of this embodiment can be determined by measuring the thickness of each layer at three or more locations near a position approximately 50 μm from the edge of the cutting edge toward the center of the rake face of the coated cutting tool, and calculating their arithmetic mean. Alternatively, the composition of each layer can be measured from the cross-sectional microstructure of the coated cutting tool of this embodiment using energy-dispersive X-ray spectroscopy (EDS) or wavelength-dispersive X-ray spectroscopy (WDS).

[0127]

Example

[0128] The present invention will be described in more detail below by way of examples, but the present invention is not limited to these examples.

[0129] Prepare a cemented carbide cutting insert as the substrate, conforming to CNMG120408, with a composition of 88.9% WC, 7.9% Co, 1.5% TiN, 1.4% NbC, and 0.3% Cr3C2 (all by mass percentages). After smoothly honing the cutting edge of the substrate using a SiC honing brush, clean the surface of the substrate.

[0130] [Inventive Articles 1-25 and Comparative Articles 1-13]

[0131] After cleaning the substrate surface, a coating layer is formed using chemical vapor deposition. First, a lower layer is formed on the surface of the substrate. Specifically, the substrate is placed in an externally heated chemical vapor deposition apparatus, and layer A, having the composition shown in Table 6, is formed on the substrate surface according to the raw material composition, temperature, and pressure conditions shown in Table 1, so that layer A reaches the average thickness shown in Table 6. Next, layer B, having the composition shown in Table 6, is formed on the surface of layer A according to the raw material composition, temperature, and pressure conditions shown in Table 1, so that layer B reaches the average thickness shown in Table 6. Next, for inventive articles 1-22, inventive article 25, and comparative articles 1-13, layer C, having the composition shown in Table 6, is further formed on the surface of layer B according to the raw material composition, temperature, and pressure conditions shown in Table 1, so that layer C reaches the average thickness shown in Table 6. Thus, a lower layer consisting of 2 or 3 layers is formed. Afterward, the surface of the lower layer is subjected to oxidation treatment according to the composition, temperature, and pressure conditions shown in Table 2, for the time shown in Table 2. Next, according to the raw material composition, temperature, and pressure conditions shown in Table 2, within the time period shown in Table 2, an α-type alumina (α-Al2O3) core is formed on the surface of the lower layer after oxidation treatment. Further, according to the raw material composition, temperature, and pressure conditions shown in Table 3, an intermediate layer (α-Al2O3 layer) with the composition shown in Table 6 is formed on the surface of the lower layer and the α-type alumina (α-Al2O3) core, achieving the average thickness shown in Table 6. Next, an upper layer is formed on the surface of the intermediate layer (α-Al2O3 layer). Specifically, firstly, the first step of forming the upper layer is performed. For the invented products 1-7, 12-25 and comparative products 1-5, 7-10, 12, and 13, according to the raw material composition, temperature, and pressure conditions shown in Table 4, an X layer (adhesive layer) with the composition shown in Table 7 is formed on the surface of the α-Al2O3 layer, achieving the average thickness shown in Table 7. Furthermore, for the invention articles 8-11 and the comparative article 6, a first process for forming the upper layer was performed for 5 minutes under the conditions of raw material composition, temperature, and pressure shown in Table 4, forming a portion of a Y layer (TiCN layer) with the composition shown in Table 7 (average thickness: approximately 0.05 μm) on the surface of the intermediate layer (α-Al2O3 layer). Next, a second process for forming the upper layer was performed, under the conditions of raw material composition, temperature, and pressure shown in Table 5, forming a Y layer with the composition shown in Table 7 on the surface of the X layer or the intermediate layer (α-Al2O3 layer), so that the Y layer reached the average thickness shown in Table 7. Furthermore, for the invention articles 8-11 and the comparative article 6, a Y layer (TiCN layer) with the composition shown in Table 7 was formed on the surface of the intermediate layer (α-Al2O3 layer), so that the total thickness of the Y layer after performing the first and second processes for forming the upper layer reached the average thickness shown in Table 7.Furthermore, for the inventive articles 1-7, 9, 10, 12, 14, 16-25 and the comparative articles 1-3, 6-13, according to the raw material composition, temperature and pressure conditions shown in Table 1, a Z layer with the composition shown in Table 7 is formed on the surface of the Y layer, so that the Z layer reaches the average thickness shown in Table 7. In this way, the covered cutting tools of the inventive articles 1-25 and the comparative articles 1-13 are obtained.

[0132] The thickness of each layer of the sample was determined using the following method: A cross-section was determined approximately 50 μm from the center of the cutting tool's tip towards the rake face. The thickness at three points on this cross-section was measured using FE-SEM, and their arithmetic mean was calculated as the average thickness. The composition of each layer of the sample was then determined using EDS at a cross-section approximately 50 μm from the center of the cutting tool's tip towards the rake face.

[0133] Table 1

[0134]

[0135] ※The layers other than TiN in the upper layer are formed under the conditions described in Tables 4 and 5.

[0136] Table 2

[0137]

[0138] Table 3

[0139]

[0140] Table 4

[0141]

[0142] ※A “-” in the table indicates that the corresponding process was not performed.

[0143] Table 5

[0144]

[0145] Table 6

[0146]

[0147] ※The “-” in the table indicates that the corresponding layer has not been formed.

[0148] Table 7

[0149]

[0150] ※The “-” in the table indicates that the corresponding layer has not been formed.

[0151] [RSA1 and RSA2]

[0152] In the obtained sample, the upper layer cross-section was exposed in a direction perpendicular to the substrate surface. The obtained cross-section was mirror-polished, and the mirror-polished surface was observed using FE-SEM. Using the electron backscatter diffraction image analysis device (EBSD) attached to the FE-SEM, the azimuth difference A formed by the normal of the (220) plane of each particle with a cubic crystal structure and the normal of the substrate surface was measured. Let the total area of ​​the upper layer cross-section being analyzed be the total area of ​​the upper layer particle cross-section in the range of azimuth difference A above 0 degrees and below 45 degrees: RSA Total Let RSA1 (unit: area%) be the ratio of the cross-sectional area of ​​the region with an azimuth difference A of 0 degrees or more but less than 10 degrees to 100 area%. Similarly, let RSA2 (unit: area%) be the ratio of the cross-sectional area of ​​the region with an azimuth difference A of 20 degrees or more but less than 30 degrees to 100 area% of the total area of ​​the upper cross-section being analyzed. Specifically, firstly, the cross-sections of particles with an azimuth difference A of 0 degrees or more but less than 45 degrees are divided into 5-degree intervals, and the area of ​​the particle cross-section in each interval is calculated. Next, the total area of ​​the particle cross-sections in each of the intervals with an azimuth difference A of 0 degrees or more but less than 10 degrees, 10 degrees or more but less than 20 degrees, 20 degrees or more but less than 30 degrees, and 30 degrees or more but less than 45 degrees is calculated. Finally, let 100 area be the total area of ​​the particle cross-sections with an azimuth difference A of 0 degrees or more but less than 45 degrees. Within these defined intervals, RSA1 represents the total cross-sectional area of ​​particles with an azimuth difference A of 0 degrees or more but less than 10 degrees, relative to RSA. Total The ratio, denoted by RSA2, represents the total cross-sectional area of ​​particles with an azimuth difference A between 20 degrees and 30 degrees relative to RSA. Total The proportions are shown in Table 8 below. The measurement results are presented in Table 8. Furthermore, the EBSD measurement method is as follows: The sample was placed under a FE-SEM and irradiated with an electron beam at an incident angle of 70 degrees, an accelerating voltage of 15 kV, and an irradiation current of 1.0 nA. Within a measurement range of 10 μm × 50 μm, with an EBSD setting of 0.1 μm step size, the azimuth difference and cross-sectional area of ​​each particle were measured. The area of ​​the particle cross-section in the upper layer within the measurement range is the sum of the pixels corresponding to that area. That is, each layer of particles is divided every 10 or 15 degrees based on the azimuth difference A, and the total area of ​​the particle cross-section in each division interval is calculated by adding the pixels occupied by the particle cross-section in each division interval and then converting it into an area.

[0153] Table 8

[0154]

[0155] The texture factor TC(0, 0, 12) of the (0, 0, 12) plane of the α-Al2O3 layer

[0156] X-ray diffraction measurements using Cu-Kα rays were performed on the obtained sample under the following conditions using a 2θ / θ focusing optical system: output: 45 kV, 200 mA; incident-side Soler slit: 5°; divergence longitudinal slit: 2 / 3°; divergence longitudinal confinement slit: 5 mm; scattering slit: 8 mm; receiving-side Soler slit: 5°; receiving slit: 10 mm; detector: D / tex ultra; scanning mode: continuous; sampling width: 0.01°; scanning speed: 12° / min; 2θ measurement range: 25°–140°. The apparatus used was an X-ray diffractometer (model "SmartLab") manufactured by Rigaku Corporation, Japan. The peak intensities of each crystal plane in the α-Al₂O₃ layer of the intermediate layer were determined based on the X-ray diffraction pattern. Based on the peak intensities of each crystal plane, the texture coefficient TC(0, 0, 12) of the α-Al2O3 layer, as shown in Equation (1), was calculated. The results are shown in Table 9.

[0157] [Formula 4]

[0158]

[0159] In equation (1), I(h,k,l) ​​is the intensity of the peak produced by X-ray diffraction obtained by measuring the (h,k,l) ​​plane of the α-Al2O3 layer, and I0(h,k,l) ​​is the standard diffraction intensity of the (h,k,l) ​​plane of α-All2O3 obtained based on JCPDS card number 10-0173. (h,k,l) ​​refers to the 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).

[0160] Table 9

[0161]

[0162] Using the invented articles 1-25 and comparative articles 1-13, cutting tests 1 and 2 were conducted under the following conditions. Cutting test 1 was a chipping test to evaluate chipping resistance, and cutting test 2 was a wear test to evaluate wear resistance. The results of each cutting test are shown in Table 10.

[0163]

Cutting Test 1

[0164] Workpiece to be cut: SCM415;

[0165] Shape of the workpiece: a round bar with two grooves equidistantly formed on its outer circumferential surface;

[0166] Cutting speed: 200 m / min;

[0167] Cut depth: 1.5mm;

[0168] Feed: 0.3 mm / rev;

[0169] Coolant: Water-soluble coolant;

[0170] Evaluation criteria: After starting cutting, stop cutting every 500 impacts and observe the cutting edge of the tool using a stereomicroscope (100x magnification). Repeat the same procedure until chipping is confirmed at the cutting edge. The cumulative number of impacts up to the point of chipping is considered the tool life.

[0171]

Cutting Test 2

[0172] Workpiece to be cut: S45C;

[0173] Workpiece shape: round bar;

[0174] Cutting speed: 250 m / min;

[0175] Depth of cut: 2.0 mm;

[0176] Feed: 0.3 mm / rev;

[0177] Coolant: Water-soluble coolant;

[0178] Evaluation criteria: Tool life is defined as the machining time until the wear width of the cutting tool's flank exceeds 0.3 mm. The machining time up to the tool life is measured.

[0179] Regarding the cumulative number of impacts up to the tool life of Cutting Test 1 (Cheap Edge Test), a cumulative number of impacts of 12,000 or more is rated "A", a cumulative number of impacts of 8,000 or more but less than 12,000 is rated "B", and a cumulative number of impacts of less than 8,000 is rated "C". Furthermore, regarding the machining time up to the tool life of Cutting Test 2 (Wear Test), a machining time of 35 minutes or more is rated "A", a machining time of 25 minutes or more but less than 35 minutes is rated "B", and a machining time of less than 25 minutes is rated "C". In this evaluation, "A" is the best, followed by "B", and "C" is the worst, meaning that the more A or B values, the better the cutting performance. The evaluation results are shown in Table 10.

[0180] Table 10

[0181]

[0182] According to the results shown in Table 10, the chipping and wear tests of the invented article were both rated "A" or "B". On the other hand, the chipping and wear tests of the comparative article were rated "C" in both or either of them. Therefore, it can be concluded that the invented article has superior chipping resistance and wear resistance overall compared to the comparative article.

[0183] The results above show that the invented product has excellent chip resistance and wear resistance, thus having a long tool life.

[0184] Industrial availability

[0185] The coated cutting tool of the present invention has excellent chip resistance and wear resistance, which can extend the tool life compared with the past. Based on this view, it has industrial applicability.

Claims

1. A coated cutting tool, comprising a substrate and a coating layer formed on the surface of the substrate, the coating layer comprising a lower layer, an intermediate layer and an upper layer sequentially from the substrate side toward the surface side of the coating layer; The lower layer includes one or more Ti compound layers composed of Ti compounds, wherein the Ti compounds are composed of Ti and at least one element selected from C, N, O and B; The intermediate layer includes an α-Al2O3 layer composed of α-Al2O3; The upper layer comprises one or more Ti compound layers composed of Ti compounds, wherein the Ti compounds are composed of Ti and at least one element selected from C, N and O, and at least one of the Ti compound layers in the upper layer is a TiCN layer, and the average thickness of the upper layer is more than 1.00 μm and less than 6.50 μm; In the upper layer, the conditions shown in equations (i) and (ii) below are satisfied: 25≤RSA1<70………………(i) In equation (i), in the cross section of the upper layer perpendicular to the surface of the substrate, if the total area of ​​the cross section is set to 100% area, the orientation difference A is the angle between the normal of the (220) plane of each particle with a cubic crystal structure and the normal of the surface of the substrate, the unit of the angle is degrees, and RSA1 refers to the proportion of the cross section area of ​​the region where the orientation difference A is greater than 0 degrees and less than 10 degrees, the unit of the proportion is area %. 25≤RSA2<70………………(ii) In equation (ii), in the cross section of the upper layer perpendicular to the surface of the substrate, if the total area of ​​the cross section is set to 100% area, the azimuth difference A is the angle between the normal of the (220) plane of each particle with a cubic crystal structure and the normal of the surface of the substrate, the unit of the angle is degrees, and RSA2 refers to the proportion of the cross section area of ​​the region where the azimuth difference A is greater than 20 degrees and less than 30 degrees, the unit of the proportion is area.

2. The coated cutting tool according to claim 1, wherein, In the upper layer, RSA1 and RSA2 together account for more than 60% and less than 90% of the area.

3. The coated cutting tool according to claim 1 or 2, wherein, The upper layer is connected to the intermediate layer. In the upper layer, the sealing layer on the side connected to the intermediate layer includes at least one layer selected from TiCO, TiON, and TiCNO. The average thickness of the sealing layer is more than 0.05 μm and less than 1.50 μm.

4. The coated cutting tool according to claim 1 or 2, wherein, In the intermediate layer, the texture factor TC(0, 0, 12) of the (0, 0, 12) plane of the α-Al2O3 layer shown in the following formula (1) is 5.9 or more and 8.9 or less: [Formula 1] In equation (1), I(h,k,l) ​​is the intensity of the peak produced by X-ray diffraction obtained by measuring the (h,k,l) ​​plane of the α-Al2O3 layer, and I0(h,k,l) ​​is the standard diffraction intensity of the (h,k,l) ​​plane of α-Al2O3 obtained based on JCPDS card number 10-0173. (h,k,l) ​​refers to the 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).

5. The coated cutting tool according to claim 1 or 2, wherein, The average thickness of the intermediate layer is greater than 3.00 μm and less than 15.00 μm.

6. The coated cutting tool according to claim 1 or 2, wherein, The average thickness of the lower layer is greater than 3.00 μm and less than 15.00 μm.

7. The coated cutting tool according to claim 1 or 2, wherein, The overall average thickness of the coating layer is greater than 10.00 μm and less than 30.00 μm.

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