Coated cutting tools

Abstract

To provide a coated cutting tool with a long tool life that has improved wear resistance and chipping resistance. 【Solution means】A coated cutting tool including a substrate and a coating layer formed on the substrate, wherein the coating layer includes a laminated structure in which a lamination unit including a Y layer is repeatedly laminated between an X layer and a Z layer, and the X layer contains a compound having a composition represented by (Al a1 M b1 Ti c1 )N, the Y layer contains a compound having a composition represented by (Al a2 M b2 Ti c2 )N, the Z layer contains a compound having a composition represented by (Al a3 M b3 Ti c3 )N, and the average thickness of the laminated structure is 0.5 μm or more and 5.0 μm or less.

Description

Technical Field

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

Background Art

[0002] In recent years, with the increasing demand for higher efficiency in cutting operations, cutting tools with a longer tool life than conventional ones have been required. For this reason, as required characteristics of tool materials, improvement of wear resistance and improvement of chipping resistance related to the life of cutting tools have become even more important. Therefore, in order to improve these characteristics, a coated cutting tool including a base material made of cemented carbide, cermet, or cubic boron nitride (cBN), etc., and one or more coating layers such as a TiN layer or a TiAlN layer that coats the surface thereof is widely used.

[0003] For example, Patent Document 1 discloses a coated cutting tool including a base material and a coating layer formed on the base material, wherein the coating layer has an alternating laminated structure of a first layer and a second layer, the first layer contains a compound having a composition represented by the following formula (1), (Al a M b Ti 1-a-b )N (1) (In formula (1), M represents at least one of Nb element and Ta element, a is the atomic ratio of Al element to the total of the element represented by M and Ti element, and satisfies 0.75 ≦ a ≦ 0.90, b is the atomic ratio of the element represented by M to the total of the element represented by M and Ti element, and satisfies 0.00 < b ≦ 0.20.) The second layer contains a compound (however, a compound different from the compound contained in the first layer) having a composition represented by the following formula (2), (Al c M d Ti 1-c-d )N (2) (In equation (2), M represents at least one of the elements Nb and Ta, c is the atomic ratio of the element Al to the sum of the elements Al, the element represented by M, and the element Ti, satisfying 0.75 ≤ c ≤ 0.90, and d is the atomic ratio of the element represented by M to the sum of the elements Al, the element represented by M, and the element Ti, satisfying 0.00 ≤ d ≤ 0.20.) A coated cutting tool is disclosed, wherein at least one of a and c is 0.80 or greater, and the average thickness of the alternating laminated structure is 0.5 μm or more and 5.0 μm or less. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2023-169722 [Overview of the project] [Problems that the invention aims to solve]

[0005] In order to improve machining efficiency, cutting conditions tend to become more stringent than before, and there is a growing demand for longer tool life. However, when machining difficult-to-cut materials with low thermal conductivity, such as nickel-based heat-resistant alloys and cobalt-based heat-resistant alloys, the coating layer on the cutting edge is prone to decomposition and oxidation due to the heat generated during cutting. As a result, wear progresses due to a decrease in the hardness of the coating layer and the shedding of particles, and chipping is more likely to occur, making it difficult to extend the tool life. In this situation, the coated cutting tool described in Patent Document 1 is required to have further improvements in wear resistance and chipping resistance.

[0006] This invention has been made in view of the above circumstances, and aims to provide a coated cutting tool with improved wear resistance and fracture resistance, resulting in a longer tool life. [Means for solving the problem]

[0007] The inventor of the present invention has conducted extensive research on extending the tool life of coated cutting tools. As a result of this research, it has been found that by configuring the coated cutting tool in a specific manner, it is possible to improve wear resistance and chipping resistance, and as a result, extend the tool life of the coated cutting tool. Based on these findings, the present invention has been completed.

[0008] That is, the gist of the present invention is as follows. [1] A coated cutting tool including a substrate and a coating layer formed on the substrate, wherein the coating layer has a laminated structure in which a laminated unit including a Y layer is repeatedly laminated between an X layer and a Z layer, the X layer contains a compound having a composition represented by the following formula (1), (Al a1 M b1 Ti c1 )N (1) (In formula (1), M represents at least one of the Nb element and the Ta element, a1 is the atomic ratio of the Al element to the total of the element represented by M and the Ti element, satisfies 0.60 ≦ a1 < 0.75, b1 is the atomic ratio of the element represented by M to the total of the Al element, the element represented by M, and the Ti element, satisfies 0.00 ≦ b1 ≦ 0.20, c1 is the atomic ratio of the Ti element to the total of the Al element, the element represented by M, and the Ti element, satisfies 0.20 ≦ c1 ≦ 0.40, and a1 + b1 + c1 = 1.) the Y layer contains a compound having a composition represented by the following formula (2), (Al a2 M b2 Ti c2 )N (2) (In formula (2), M represents at least one of the Nb element and the Ta element, a2 is the atomic ratio of the Al element to the total of the element represented by M and the Ti element, satisfies 0.75 ≦ a2 ≦ 0.95, b2 is the atomic ratio of the element represented by M to the sum of the elements Al, the element represented by M, and the element Ti. Satisfying 0.03 ≤ b² ≤ 0.20, c2 is the atomic ratio of the element Ti to the total amount of the elements Al, the element represented by M, and the element Ti. Satisfying 0.00 ≤ c² ≤ 0.22, a² + b² + c² = 1. The Z layer contains a compound having the composition represented by the following formula (3): (Al a3 M b3 Ti c3 )N (3) (In formula (3), M represents at least one of the elements Nb and Ta, a3 is the atomic ratio of Al to the total of Al, the element represented by M, and the element Ti. Satisfying 0.80 ≤ a3 ≤ 0.95, b3 is the atomic ratio of the element represented by M to the sum of the elements Al, the element represented by M, and the element Ti. Satisfying 0.00 ≤ b3 < 0.03, c3 is the atomic ratio of the element Ti to the sum of the elements Al, the element represented by M, and the element Ti. Satisfying 0.05 ≤ c3 ≤ 0.20, a³ + b³ + c³ = 1. A coated cutting tool having an average thickness of 0.5 μm or more and 5.0 μm or less of the aforementioned laminated structure. [2] The coated cutting tool according to [1], wherein a1 and a3 satisfy 0.05 < (a3 - a1) ≤ 0.25. [3] The coated cutting tool according to [1] or [2], wherein a1 and a2 satisfy 0.05 ≤ (a2 - a1) ≤ 0.25. [4] The coated cutting tool according to any of [1] to [3], wherein b1 and b2 satisfy 0.02 ≤ (b2 - b1) ≤ 0.15. [5] The average composition of the entire compound of the laminated structure is represented by the following formula (4), and the coated cutting tool according to any one of [1] to [4]. (Al a M b Ti c )N (4) (In formula (4), M represents at least one of the Nb element and the Ta element, a is the atomic ratio of the Al element to the total of the element represented by M and the Ti element, satisfies 0.70 ≤ a ≤ 0.85, b is the atomic ratio of the element represented by M to the total of the Al element, the element represented by M, and the Ti element, satisfies 0.00 < b ≤ 0.15, c is the atomic ratio of the Ti element to the total of the Al element, the element represented by M, and the Ti element, satisfies 0.10 ≤ c ≤ 0.25, a + b + c = 1.) [6] In the X-ray diffraction of the laminated structure, the sum of the integrated intensities of the diffraction peaks of the cubic (111) plane and the cubic (200) plane is I cub and the sum of the integrated intensities of the diffraction peaks of the hexagonal (100) plane and the hexagonal (110) plane is I hex When taken as, I hex / I cub is 0.00 or more and 0.40 or less, and the coated cutting tool according to any one of [1] to [5]. [7] The average thickness per layer of the X layer is 2 nm or more and 300 nm or less, the average thickness per layer of the Y layer is 2 nm or more and 300 nm or less, and the average thickness per layer of the Z layer is 2 nm or more and 300 nm or less, and the coated cutting tool according to any one of [1] to [6]. [8] The coating layer has a lower layer between the base material and the laminated structure, The lower layer is a single or multilayer compound comprising at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, B, and Y, and at least one element selected from the group consisting of C, N, and O (however, a compound different from the compound contained in the layered structure). The coating cutting tool according to any one of [1] to [7], wherein the average thickness of the lower layer is 0.1 μm or more and 2.0 μm or less. [9] The coating layer has an upper layer on the surface opposite to the substrate in the laminated structure, The upper layer is a single or multilayer compound comprising at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, B, and Y, and at least one element selected from the group consisting of C, N, and O (however, a compound different from the compound contained in the layered structure). The coating cutting tool according to any one of [1] to [8], wherein the average thickness of the upper layer is 0.1 μm or more and 2.0 μm or less.

[10] The coating cutting tool according to any one of [1] to [9], wherein the average thickness of the entire coating layer is 0.5 μm or more and 5.0 μm or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a coated cutting tool with improved wear resistance and fracture resistance, resulting in a longer tool life. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing an example of a coated cutting tool of the present invention. [Figure 2] This is a schematic diagram showing another example of a coated cutting tool according to the present invention. [Modes for carrying out the invention]

[0011] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"), but the present invention is not limited to the embodiments described below. The present invention can be modified in various ways without departing from its spirit. In the drawings, the same elements are denoted by the same reference numerals, and redundant explanations are omitted. Furthermore, unless otherwise specified, positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Moreover, the dimensional ratios in the drawings are not limited to the ratios shown.

[0012] The coated cutting tool of this embodiment is a coated cutting tool comprising a base material and a coating layer formed on the base material, The coating layer includes a laminated structure in which a laminated unit containing a Y layer is repeatedly stacked between the X layer and the Z layer. The X layer contains a compound having the composition represented by the following formula (1): (Al a1 M b1 Ti c1 )N (1) (In formula (1), M represents at least one of the elements Nb and Ta, a1 is the atomic ratio of Al to the sum of the elements represented by M and Ti. Satisfying 0.60 ≤ a1 < 0.75, b1 is the atomic ratio of the element represented by M to the sum of the elements Al, M, and Ti. Satisfying 0.00 ≤ b1 ≤ 0.20, c1 is the atomic ratio of the element Ti to the sum of the elements Al, the element represented by M, and the element Ti. Satisfying 0.20 ≤ c1 ≤ 0.40, a1 + b1 + c1 = 1. The Y layer contains a compound having the composition represented by the following formula (2): (Al a2 M b2 Ti c2 )N (2) (In formula (2), M represents at least one of the elements Nb and Ta, a2 is the atomic ratio of Al to the sum of the elements represented by M and Ti. Satisfying 0.75 ≤ a2 ≤ 0.95, b2 is the atomic ratio of the element represented by M to the sum of the elements Al, the element represented by M, and the element Ti. Satisfying 0.03 ≤ b² ≤ 0.20, c2 is the atomic ratio of the element Ti to the total amount of the elements Al, the element represented by M, and the element Ti. Satisfying 0.00 ≤ c² ≤ 0.22, a² + b² + c² = 1. The Z layer contains a compound having the composition represented by the following formula (3): (Al a3 M b3 Ti c3 )N (3) (In formula (3), M represents at least one of the elements Nb and Ta, a3 is the atomic ratio of Al to the total of Al, the element represented by M, and the element Ti. Satisfying 0.80 ≤ a3 ≤ 0.95, b3 is the atomic ratio of the element represented by M to the sum of the elements Al, the element represented by M, and the element Ti. Satisfying 0.00 ≤ b3 < 0.03, c3 is the atomic ratio of the element Ti to the sum of the elements Al, the element represented by M, and the element Ti. Satisfying 0.05 ≤ c3 ≤ 0.20, a³ + b³ + c³ = 1. The average thickness of the laminated structure is between 0.5 μm and 5.0 μm.

[0013] The factors that contribute to the improved wear resistance and fracture resistance of such coated cutting tools, resulting in longer tool life, are not fully understood, but are presumed to be as follows. However, the factors are not limited to those listed below. In the X layer that forms the laminated structure, the composition is represented by formula (1) (Al a1 M b1 Ti c1If a1 in N is 0.60 or higher, the adhesion between the X layer and the Y and / or Z layers is improved, resulting in excellent fracture resistance, and also improved hardness and oxidation resistance, thus resulting in excellent wear resistance. On the other hand, if a1 is less than 0.75, the formation of hexagonal crystals in the Y and Z layers is suppressed, improving hardness, thus resulting in excellent wear resistance. Also, if b1 is 0.00 or higher, and the element represented by M is included, toughness is improved, so there is a tendency for excellent fracture resistance. On the other hand, if b1 is 0.20 or lower, the relatively high content of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or the relatively high content of Ti improves the adhesion of the coating layer, resulting in excellent fracture resistance. Also, if c1 is 0.20 or higher, the adhesion of the coating layer improves, resulting in excellent fracture resistance. On the other hand, if c1 is 0.40 or less, the relatively high content of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or the relatively high content of the element represented by M improves toughness, resulting in excellent fracture resistance. Next, in the Y layer that forms the laminated structure, the composition is represented by formula (2) (Al a2 M b2 Ti c2 If a2 in N is 0.75 or higher, the coarsening of the Y layer is suppressed, and the change in particle size from the substrate side to the surface side of the coating layer becomes smaller, resulting in a homogenized structure and improved chipping resistance, thus providing excellent fracture resistance. On the other hand, if a2 is 0.95 or lower, the formation of hexagonal crystals in the Z layer is suppressed, and the hardness is improved, resulting in excellent wear resistance. Furthermore, if b2 is 0.03 or higher, the layered structure has a Z layer with a3 of 0.80 or higher (described later), which suppresses the refinement of the structure and suppresses particle shedding during cutting, resulting in excellent wear resistance and fracture resistance, as well as improved toughness, thus providing excellent fracture resistance. On the other hand, if b2 is 0.20 or lower, the hardness is improved, resulting in excellent wear resistance. Furthermore, if c2 is 0.00 or higher, when Ti is present, the adhesion of the coating layer is improved, which tends to result in excellent fracture resistance. On the other hand, if c2 is 0.22 or less, the relatively high content of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or the high content of the element represented by M improves toughness, resulting in excellent fracture resistance. Next, in the Z layer that forms the laminated structure, the composition is represented by formula (3) (Al a3 M b3 Ti c3 If a3 in N is 0.80 or higher, hardness and oxidation resistance are improved, resulting in excellent wear resistance. On the other hand, if a3 is 0.95 or lower, the formation of hexagonal crystals is suppressed, hardness is improved, resulting in excellent wear resistance. Furthermore, if b3 is 0.00 or higher, if the element represented by M is present, toughness is improved, resulting in a tendency towards excellent fracture resistance. If the element represented by M is not present, a relatively high content of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or a relatively high content of Ti improves the adhesion of the coating layer, resulting in excellent fracture resistance. On the other hand, if b3 is less than 0.03, a relatively high content of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or a relatively high content of Ti improves the adhesion of the coating layer, resulting in excellent fracture resistance. Furthermore, if c3 is 0.05 or higher, the adhesion of the coating layer improves, resulting in excellent fracture resistance. On the other hand, if c3 is 0.20 or less, the relatively high content of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or the relatively high content of the element represented by M improves toughness, resulting in excellent fracture resistance. Furthermore, if the average thickness of the entire laminated structure is 0.5 μm or more, wear resistance is improved. On the other hand, if the average thickness of the entire laminated structure is 5.0 μm or less, peeling of the coating layer is suppressed, thus improving fracture resistance. These effects combined result in a coated cutting tool of this embodiment that has improved wear resistance and fracture resistance, and a longer tool life.

[0014] The coated cutting tool of this embodiment includes a base material and a coating layer formed on the surface of that base material. The base material used in this embodiment is not particularly limited as long as it can be used as a base material for a coated cutting tool. Examples of base materials include cemented carbide, cermet, ceramics, cubic boron nitride sintered body, diamond sintered body, and high-speed steel. Among these, it is even more preferable if the base material is cemented carbide, cermet, ceramics, or cubic boron nitride sintered body, as this provides even better wear resistance and fracture resistance for the coated cutting tool.

[0015] In the coated cutting tool of this embodiment, the average thickness of the entire coating layer is preferably 0.5 μm or more and 5.0 μm or less. In the coated cutting tool of this embodiment, if the average thickness of the entire coating layer is 0.5 μm or more, it tends to have excellent wear resistance. Furthermore, in the coated cutting tool of this embodiment, if the average thickness of the entire coating layer is 5.0 μm or less, peeling of the coating layer is suppressed, so the fracture resistance tends to be further improved. From a similar viewpoint, the average thickness of the entire coating layer is more preferably 0.6 μm or more and 4.8 μm or less, and even more preferably 0.9 μm or more and 4.5 μm or less.

[0016] [X layer] In the coated cutting tool of this embodiment, the X layer is a compound layer containing a compound having a composition represented by the following formula (1). (Al a1 M b1 Ti c1 )N (1) In equation (1), M represents at least one of the elements Nb and Ta, a1 is the atomic ratio of the element Al to the sum of the elements Al, the element represented by M, and the element Ti, satisfying 0.60 ≤ a1 < 0.75, b1 is the atomic ratio of the element represented by M to the sum of the elements Al, the element represented by M, and the element Ti, satisfying 0.00 ≤ b1 ≤ 0.20, c1 is the atomic ratio of the element Ti to the sum of the elements Al, the element represented by M, and the element Ti, satisfying 0.20 ≤ c1 ≤ 0.40, and a1 + b1 + c1 = 1.

[0017] In the X layer that forms the laminated structure, the composition is represented by formula (1) (Al a1 M b1 Ti c1 If a1 in N is 0.60 or higher, the adhesion between the X layer and the Y and / or Z layers is improved, resulting in excellent fracture resistance, and also improved hardness and oxidation resistance, thus resulting in excellent wear resistance. On the other hand, if a1 is less than 0.75, the formation of hexagonal crystals in the Y and Z layers is suppressed, improving hardness, thus resulting in excellent wear resistance. From a similar viewpoint, a1 is preferably 0.66 to 0.74, and more preferably 0.66 to 0.72. Also, if b1 is 0.00 or higher, and contains an element represented by M, the toughness is improved, so there is a tendency for excellent fracture resistance. On the other hand, if b1 is 0.20 or lower, the relatively high content of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or the relatively high content of Ti improves the adhesion of the coating layer, resulting in excellent fracture resistance. From a similar viewpoint, b1 is preferably 0.00 to 0.18, and more preferably 0.02 to 0.14. Furthermore, if c1 is 0.20 or higher, the adhesion of the coating layer improves, resulting in excellent fracture resistance. On the other hand, if c1 is 0.40 or lower, the relatively high content of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or the relatively high content of the element represented by M improves toughness, resulting in excellent fracture resistance. From a similar viewpoint, c1 is preferably 0.22 to 0.34, and more preferably 0.26 to 0.34.

[0018] In formula (1), the element represented by M is at least one of Nb and Ta. "At least one of Nb and Ta" includes cases where either Nb or Ta is present, and cases where both Nb and Ta are present. When Nb is present, the formation of hexagonal crystals is suppressed compared to when Ta is present, which tends to suppress the decrease in hardness. From this viewpoint, it is preferable that the element represented by M in formula (1) contains more Nb than Ta, and it is even more preferable that it is Nb. Furthermore, the element represented by M in equations (2) to (4) described later is the same as in equation (1).

[0019] Furthermore, in this embodiment, the composition of each compound is, for example, (Al 0.75 M 0.05 Ti 0.20 When written as )N, it means that the atomic ratio of Al to the total of Al, the element represented by M, and Ti is 0.75, the atomic ratio of the element represented by M to the total of Al, the element represented by M, and Ti is 0.05, and the atomic ratio of Ti to the total of Al, the element represented by M, and Ti is 0.20. In other words, it means that the amount of Al is 75%, the amount of the element represented by M is 5%, and the amount of Ti is 20% of the total of Al, the element represented by M, and Ti.

[0020] [Y layer] In the coated cutting tool of this embodiment, the Y layer is a compound layer containing a compound having a composition represented by the following formula (2). (Al a2 M b2 Ti c2 )N (2) In equation (2), M represents at least one of the elements Nb and Ta, a2 is the atomic ratio of Al to the sum of Al, the element represented by M, and the element Ti, satisfying 0.75 ≤ a2 ≤ 0.95, b2 is the atomic ratio of the element represented by M to the sum of Al, the element represented by M, and the element Ti, satisfying 0.03 ≤ b2 ≤ 0.20, c2 is the atomic ratio of the element Ti to the sum of Al, the element represented by M, and the element Ti, satisfying 0.00 ≤ c2 ≤ 0.22, and a2 + b2 + c2 = 1.

[0021] In the Y layer forming the laminated structure, the composition is represented by formula (2) (Al a2 M b2 Ti c2If a2 in N is 0.75 or higher, the coarsening of the Y layer is suppressed, and the change in particle size from the substrate side to the surface side of the coating layer becomes smaller, resulting in a homogenized structure and improved chipping resistance, thus providing excellent fracture resistance. On the other hand, if a2 is 0.95 or lower, the formation of hexagonal crystals in the Z layer is suppressed, and the hardness is improved, resulting in excellent wear resistance. From a similar viewpoint, a2 is preferably 0.77 to 0.92, and more preferably 0.80 to 0.90. Furthermore, if b2 is 0.03 or higher, the laminated structure has a Z layer in which a3 is 0.80 or higher, which suppresses the refinement of the structure and suppresses particle shedding during cutting, resulting in excellent wear resistance and fracture resistance, as well as improved toughness, thus providing excellent fracture resistance. On the other hand, if b2 is 0.20 or lower, the hardness is improved, resulting in excellent wear resistance. From a similar viewpoint, b2 is preferably 0.04 to 0.18, and more preferably 0.05 to 0.15. Also, if c2 is 0.00 or higher, when it contains Ti, the adhesion of the coating layer improves, and thus tends to be excellent in fracture resistance. On the other hand, if c2 is 0.22 or lower, the relatively high amount of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or the high amount of the element represented by M improves toughness, resulting in excellent fracture resistance. From a similar viewpoint, c2 is preferably 0.04 to 0.19, and more preferably 0.05 to 0.17.

[0022] [Z layer] In the coated cutting tool of this embodiment, the Z layer is a compound layer containing a compound having a composition represented by the following formula (3). (Al a3 M b3 Ti c3 )N (3) In equation (3), M represents at least one of the elements Nb and Ta, a3 is the atomic ratio of the element Al to the sum of the elements Al, the element represented by M, and the element Ti, satisfying 0.80 ≤ a3 ≤ 0.95, b3 is the atomic ratio of the element represented by M to the sum of the elements Al, the element represented by M, and the element Ti, satisfying 0.00 ≤ b3 < 0.03, c3 is the atomic ratio of the element Ti to the sum of the elements Al, the element represented by M, and the element Ti, satisfying 0.05 ≤ c3 ≤ 0.20, and a3 + b3 + c3 = 1.

[0023] In the Z layer forming the laminated structure, the composition is represented by formula (3) (Al a3 M b3 Ti c3)When a3 in N is 0.80 or higher, hardness and oxidation resistance are improved, resulting in excellent wear resistance. On the other hand, when a3 is 0.95 or lower, the formation of hexagonal crystals is suppressed, hardness is improved, resulting in excellent wear resistance. From a similar viewpoint, a3 is preferably 0.80 or higher and 0.93 or lower, and more preferably 0.85 or higher and 0.90 or lower. Furthermore, when b3 is 0.00 or higher, if the element represented by M is included, toughness is improved, resulting in a tendency towards excellent fracture resistance. If the element represented by M is not included, a relatively high content of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or a relatively high content of Ti improves the adhesion of the coating layer, resulting in excellent fracture resistance. On the other hand, when b3 is less than 0.03, a relatively high content of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or a relatively high content of Ti improves the adhesion of the coating layer, resulting in excellent fracture resistance. From a similar viewpoint, b3 is preferably 0.00 to 0.02, and more preferably 0.00 to 0.01. Furthermore, if c3 is 0.05 or higher, the adhesion of the coating layer is improved, resulting in excellent fracture resistance. On the other hand, if c3 is 0.20 or lower, the relatively high content of Al improves hardness and oxidation resistance, resulting in excellent wear resistance, or the relatively high content of the element represented by M improves toughness, resulting in excellent fracture resistance. From a similar viewpoint, c3 is preferably 0.07 to 0.19, and more preferably 0.10 to 0.18.

[0024] [Laminated structure] The coated cutting tool of this embodiment includes a laminated structure in which laminated units containing a Y layer between an X layer and a Z layer are repeatedly laminated in the coating layer. The repeatedly laminated laminated units are not particularly limited as long as they contain a Y layer between an X layer and a Z layer, but for example, they may be laminated units in which the X layer, Y layer and Z layer are formed in this order from the substrate side toward the surface side of the coating layer, or laminated units in which the Z layer, Y layer and X layer are formed in this order from the substrate side toward the surface side of the coating layer, or laminated units in which the X layer, Y layer, Z layer and Y layer are formed in this order from the substrate side toward the surface side of the coating layer. In this embodiment, if the coated cutting tool includes a Y layer between, for example, the X layer, in which the atomic ratio a1 of Al is less than 0.75, and the Z layer, in which the atomic ratio a3 of Al is 0.80 or more, the adhesion between the X layer and the Z layer is improved, microstructure refinement is suppressed, and peeling of the coating layer and shedding of particles are suppressed, resulting in a tendency for the tool to have even better wear resistance and fracture resistance.

[0025] Figure 1 is a schematic cross-sectional view showing an example of a coated cutting tool according to this embodiment. The coated cutting tool 1 shown in Figure 1 comprises a base material 2 and a coating layer 3 formed on the surface of the base material 2. The coating layer 3 includes a laminated structure 4 in which laminated units, each consisting of an X layer 41, a Y layer 42, and a Z layer 43, are repeatedly stacked from the base material 2 side. In the laminated structure 4 shown in Figure 1, the laminated units consisting of the X layer 41, Y layer 42, and Z layer 43 are repeatedly stacked four times. Figure 2 is a schematic cross-sectional view showing another example of a coated cutting tool according to this embodiment. The coated cutting tool 1 shown in Figure 2 comprises a base material 2 and a coating layer 3 formed on the surface of the base material 2. The coating layer 3 includes a laminated structure 4 in which laminated units, each consisting of an X layer 41, a Y layer 42, a Z layer 43, and a Y layer 42, are repeatedly stacked from the base material 2 side. In the laminated structure 4 shown in Figure 2, the laminated units consisting of the X layer 41, a Y layer 42, a Z layer 43, and a Y layer 42 are repeatedly stacked three times.

[0026] In the coated cutting tool of this embodiment, the number of repetitions of the laminated unit containing the Y layer between the X layer and the Z layer is preferably 3 to 750 times, more preferably 5 to 500 times, and even more preferably 10 to 400 times. When the number of repetitions of the laminated unit containing the Y layer between the X layer and the Z layer is within the above range, the fracture resistance tends to be further improved. In this embodiment, if the stacking unit containing a Y layer between the X layer and the Z layer consists of three types, for example, an X layer, a Y layer, and a Z layer, and one layer of each of the X, Y, and Z layers is formed, the "number of repetitions" is 1.

[0027] In the coating layer used in this embodiment, it is preferable that the difference between a1 in formula (1) and a3 in formula (3), (a3-a1), is greater than 0.05 and less than or equal to 0.25. When (a3-a1) is greater than 0.05, chipping resistance is improved, and thus the coating tends to have excellent fracture resistance. On the other hand, when (a3-a1) is 0.25 or less, peeling of the coating layer is suppressed, and thus the coating tends to have improved fracture resistance. From a similar viewpoint, it is more preferable that (a3-a1) is between 0.06 and 0.23, and even more preferable that it is between 0.08 and 0.20.

[0028] In the coating layer used in this embodiment, it is preferable that the difference between a1 in formula (1) and a2 in formula (2), (a2-a1), is 0.05 or more and 0.25 or less. When (a2-a1) is 0.05 or more, chipping resistance is improved, and thus the coating tends to have excellent fracture resistance. On the other hand, when (a2-a1) is 0.25 or less, peeling of the coating layer is suppressed, and thus the coating tends to have improved fracture resistance. From a similar viewpoint, it is more preferable that (a2-a1) is 0.06 or more and 0.22 or less, and even more preferable that it is 0.08 or more and 0.19 or less.

[0029] In the coating layer used in the present embodiment, it is preferable that the difference (b2 - b1) between b1 in the formula (1) and b2 in the formula (2) is 0.02 or more and 0.15 or less. When (b2 - b1) is 0.02 or more, the adhesion between the X layer and the Y layer is improved and peeling is suppressed, so that the defect resistance tends to be excellent. On the other hand, when (b2 - b1) is 0.15 or less, the change in particle size tends to be small from the substrate side toward the surface side of the coating layer, so that the structure is homogenized and the chipping resistance is improved, and thus the defect resistance tends to be excellent. From the same viewpoint, (b2 - b1) is more preferably 0.03 or more and 0.14 or less, and still more preferably 0.04 or more and 0.08 or less.

[0030] In the coated cutting tool of the present embodiment, the average composition of the entire laminated structure compound is preferably represented by the following formula (4). (Al a M b Ti c )N (4) In the formula (4), M represents at least one of the Nb element and the Ta element, a is the atomic ratio of the Al element to the total of the element represented by M and the Ti element, and satisfies 0.70 ≤ a ≤ 0.85, b is the atomic ratio of the element represented by M to the total of the Al element, the element represented by M, and the Ti element, and satisfies 0.00 < b ≤ 0.15, c is the atomic ratio of the Ti element to the total of the Al element, the element represented by M, and the Ti element, satisfies 0.10 ≤ c ≤ 0.25, and a + b + c = 1.

[0031] In the formula (4), when a is 0.70 or more, the hardness and oxidation resistance of the coating layer are improved, so that the wear resistance tends to be excellent. On the other hand, when a is 0.85 or less, the formation of hexagonal crystals is suppressed and the hardness is improved, so that the wear resistance tends to be excellent. From the same viewpoint, a is more preferably 0.73 or more and 0.84 or less, and still more preferably 0.74 or more and 0.83 or less. In equation (4), when b is greater than 0.00, toughness improves, and therefore fracture resistance tends to improve. On the other hand, when b is 0.15 or less, the relatively high Al content improves hardness and oxidation resistance, and therefore wear resistance tends to be excellent, or the relatively high Ti content improves adhesion of the coating layer, and therefore fracture resistance tends to be excellent. From a similar viewpoint, it is more preferable that b is between 0.01 and 0.12, and even more preferable that it is between 0.02 and 0.09. In formula (4), when c is 0.10 or greater, the adhesion of the coating layer improves, and thus the material tends to have excellent fracture resistance. On the other hand, when c is 0.25 or less, the relatively high content of Al improves hardness and oxidation resistance, and thus the material tends to have excellent wear resistance, or the relatively high content of the element represented by M improves toughness, and thus the material tends to have excellent fracture resistance. From a similar viewpoint, it is more preferable that c is between 0.12 and 0.23, and even more preferable that it is between 0.13 and 0.21.

[0032] In the coated cutting tool of this embodiment, it is preferable that the average thickness per layer of the X layer is 2 nm or more and 300 nm or less, the average thickness per layer of the Y layer is 2 nm or more and 300 nm or less, and the average thickness per layer of the Z layer is 2 nm or more and 300 nm or less. When the average thickness per layer of each of the X, Y, and Z layers is 2 nm or more, cracks generated during cutting are suppressed from propagating toward the substrate, which tends to further improve fracture resistance, and it also tends to be easier to form layers of uniform thickness, which tends to further stabilize the performance of the coated cutting tool. On the other hand, when the average thickness per layer of each of the X, Y, and Z layers is 300 nm or less, the adhesion between each layer is excellent, which suppresses peeling of the coating layer, and therefore tends to improve fracture resistance. From a similar viewpoint, it is more preferable that the average thickness per layer of each of the X, Y, and Z layers is 4 nm or more and 150 nm or less, even more preferable that it is 5 nm or more and 100 nm or less, and even more preferable that it is 10 nm or more and 50 nm or less. The average thickness of each layer of the X, Y, and Z layers may be the same or different.

[0033] In the coated cutting tool of this embodiment, the average thickness of the entire laminated structure is 0.5 μm or more and 5.0 μm or less. When the average thickness of the entire laminated structure is 0.5 μm or more, wear resistance is improved. On the other hand, when the average thickness of the entire laminated structure is 5.0 μm or less, peeling of the coating layer is suppressed, and thus fracture resistance is improved. From a similar viewpoint, the average thickness of the entire laminated structure is preferably 0.6 μm or more and 4.8 μm or less, and more preferably 0.9 μm or more and 4.5 μm or less.

[0034] The coated cutting tool of this embodiment, in X-ray diffraction of a layered structure, calculates the sum of the integrated intensities of the diffraction peaks of the cubic (111) plane and the cubic (200) plane to I cub Let the sum of the integrated intensities of the diffraction peaks of the hexagonal (100) plane and the hexagonal (110) plane be I hex In that case, I hex / I cub However, it is preferable that it be between 0.00 and 0.40. hex / I cub When the ratio is 0.40 or less, it indicates that the formation of hexagonal crystals is suppressed, and the hardness improves, resulting in a tendency for even better wear resistance. From a similar perspective, in a laminated structure, I hex / I cub It is more preferably 0.00 or more and 0.38 or less, even more preferably 0.00 or more and 0.33 or less, and even more preferably 0.00 or more and 0.25 or less.

[0035] The integrated intensity of the peaks of each surface index in the coating layer used in this embodiment can be determined by using a commercially available X-ray diffractometer. For example, by measuring the X-ray diffraction of a 2θ / θ focusing optical system using Cu-Kα rays using a Rigaku SmartLab (product name) X-ray diffractometer under the following conditions, the integrated intensity of the peaks of each surface index can be measured. The measurement conditions are: output: 45kV, 200mA, incident solar slit: 5°, diverging longitudinal slit: 2 / 3°, diverging longitudinal limiting slit: 5mm, scattering slit: 2 / 3°, receiving solar slit: 5°, receiving slit: 0.3mm, sampling width: 0.01°, scan speed: 4° / min, 2θ measurement range: 25°~70°. When determining the integrated intensity of the peaks of each surface index from the X-ray diffraction pattern, analysis software attached to the X-ray diffractometer may also be used. The analysis software uses a cubic approximation to perform background processing and Kα2 peak removal, and then performs profile fitting using the Pearson-VII function to determine the integrated intensity of each peak. For example, if the X-ray diffraction peak of the (111) plane of the cubic crystal originating from the layered structure is detected as a single peak, the integrated intensity of that single peak is used. If it is detected as two peaks, the sum of the integrated intensities of the two peaks is used as the integrated intensity of the X-ray diffraction peak of the (111) plane of the layered structure. Furthermore, in this embodiment, the integrated intensity of the peaks of each surface index of the coating layer can be measured and calculated specifically by the method described in the later embodiment.

[0036] [Lower layer] The coating layer used in this embodiment may consist only of a laminated structure, but it is preferable to have a lower layer between the substrate and the laminated structure. Having a lower layer tends to further improve the adhesion between the substrate and the coating layer. From a similar viewpoint, the lower layer is preferably a single or multilayer of a compound consisting of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, B, and Y and at least one element selected from the group consisting of C, N, and O (however, a compound different from the compound contained in the laminated structure), more preferably a single or multilayer of a compound consisting of at least one element selected from the group consisting of Ti, Nb, Ta, Cr, Mo, W, Al, Si, and B and at least one element selected from the group consisting of C and N, and even more preferably a single or multilayer of a compound consisting of at least one element selected from the group consisting of Ti, Cr, Al, and Si and at least one element selected from the group consisting of C and N. The specific compounds included in the lower layer are not particularly limited, but examples include TiAlN, CrN, TiCN, TiAlSiN, etc.

[0037] In this embodiment, it is preferable that the average thickness of the lower layer is 0.1 μm or more and 2.0 μm or less. When the average thickness of the lower layer is 0.1 μm or more, the adhesion between the coating layer and the substrate is further improved, and thus the fracture resistance tends to be further improved. On the other hand, when the average thickness of the lower layer is 2.0 μm or less, peeling of the coating layer is suppressed, and thus the fracture resistance tends to be further improved. From a similar viewpoint, it is more preferable that the average thickness of the lower layer is 0.3 μm or more and 1.5 μm or less, and even more preferable that it is 0.5 μm or more and 1.0 μm or less.

[0038] [Top layer] The coating layer used in this embodiment may consist only of a laminated structure, but may also have an upper layer on the surface opposite to the substrate in the laminated structure. When the coating layer has an upper layer, it tends to have even better abrasion resistance. The upper layer is preferably a single or multilayer of a compound consisting of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, B, and Y and at least one element selected from the group consisting of C, N, and O (however, a compound different from the compound contained in the laminated structure), more preferably a single or multilayer of a compound consisting of at least one element selected from the group consisting of Ti, Nb, Ta, Cr, Mo, Al, and Si and at least one element selected from the group consisting of C and N, and even more preferably a single or multilayer of a compound consisting of at least one element selected from the group consisting of Ti, Mo, Al, and Si and the element N. The specific compounds included in the upper layer are not particularly limited, but examples include TiN, TiAlN, TiSiN, TiMoN, NbN, etc.

[0039] In the coating layer used in this embodiment, the average thickness of the upper layer is preferably 0.1 μm or more and 2.0 μm or less. When the average thickness of the upper layer is 0.1 μm or more, it tends to have excellent abrasion resistance. Furthermore, when the average thickness of the upper layer is 2.0 μm or less, peeling of the coating layer is suppressed, so the chipping resistance tends to be further improved. From a similar viewpoint, the average thickness of the upper layer is more preferably 0.3 μm or more and 1.5 μm or less, and even more preferably 0.5 μm or more and 1.0 μm or less.

[0040] [Method for manufacturing the coating layer] The method for manufacturing the coating layer in the coated cutting tool of this embodiment is not particularly limited, but examples include physical vapor deposition methods such as ion plating, arc ion plating, sputtering, and ion mixing. Forming the coating layer using a physical vapor deposition method is preferable because it allows for the formation of sharp edges. Among these, the arc ion plating method is more preferable because it provides superior adhesion between the coating layer and the substrate.

[0041] [Method for manufacturing coated cutting tools] The method for manufacturing the coated cutting tool of this embodiment will be described below with specific examples. However, the method for manufacturing the coated cutting tool of this embodiment is not particularly limited, as long as the configuration of the coated cutting tool can be achieved.

[0042] First, the substrate processed into the tool shape is placed inside the reaction vessel of the physical vapor deposition apparatus, and the metal evaporation source is installed inside the reaction vessel. Then, the pressure inside the reaction vessel is increased to 1.0 × 10⁻⁶. -2 The reaction vessel is evacuated to a vacuum of less than Pa, and the substrate is heated by a heater inside the reaction vessel until its temperature reaches 200°C to 700°C. After heating, Ar gas is introduced into the reaction vessel to set the pressure inside the vessel to 0.5 Pa to 5.0 Pa. In an Ar gas atmosphere at a pressure of 0.5 Pa to 5.0 Pa, a bias voltage of -500 V to -350 V is applied to the substrate, and a current of 40 A to 50 A is passed through the tungsten filament inside the reaction vessel to perform ion bombardment treatment on the surface of the substrate with Ar gas. After ion bombardment treatment on the surface of the substrate, the pressure inside the reaction vessel is set to 1.0 × 10⁻⁶ -2 Vacuum is drawn until a vacuum of less than Pa is achieved.

[0043] When forming the lower layer used in this embodiment, the substrate temperature is controlled until it reaches 250°C to 500°C. After control, gas is introduced into the reaction vessel to set the pressure inside the reaction vessel to 3.0 Pa to 8.0 Pa. Examples of the gas used include N2 gas when the lower layer is composed of a compound consisting of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, B, and Y, and N, and when the lower layer is composed of a compound consisting of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, B, and Y, and C and N, and when a mixed gas of N2 gas and C2H2 gas is used. The volume ratio of the mixed gas is not particularly limited, but for example, N2 gas:C2H2 gas = 95:5 to 85:15 may be used. Next, a bias voltage of -200V to -40V is applied to the substrate and an arc discharge with an arc current of 80A to 120A is used to evaporate the metal evaporation source corresponding to the metal, metalloid, and nonmetal components of each layer to form the lower layer. For example, when forming a lower layer containing at least one of elements B and C, a metal evaporation source containing elements B and / or C may be used as necessary.

[0044] In this embodiment, the method for forming the laminated structure is not particularly limited as long as it involves repeatedly stacking laminated units, each containing a Y layer, between the X and Z layers. In forming the X layer used in this embodiment, the substrate temperature is controlled to 200°C to 300°C, N2 gas is introduced into the reaction vessel, and the pressure inside the reaction vessel is set to 8.0 Pa to 12.0 Pa. Then, a bias voltage of -400 V to -200 V is applied to the substrate, and the metal evaporation source corresponding to the metal component of the X layer is evaporated by arc discharge with an arc current of 80 A to 150 A to form the X layer.

[0045] When forming the Y layer used in this embodiment, the substrate temperature is controlled to 200°C to 300°C. It is preferable to set the substrate temperature to the same as the substrate temperature used when forming the X and Z layers, as this allows for the continuous formation of the X, Y, and Z layers. After controlling the temperature, N2 gas is introduced into the reaction vessel, and the pressure inside the reaction vessel is set to 8.0 Pa to 12.0 Pa. Next, a bias voltage of -400 V to -200 V is applied to the substrate, and the metal evaporation source corresponding to the metal component of the Y layer is evaporated by arc discharge with an arc current of 80 A to 150 A to form the Y layer.

[0046] When forming the Z layer used in this embodiment, the substrate temperature is controlled to 200°C to 300°C. It is preferable to set the substrate temperature to the same temperature as the substrate temperature when forming the X and Y layers, as this allows for the continuous formation of the X, Y, and Z layers. After controlling the temperature, N2 gas is introduced into the reaction vessel, and the pressure inside the reaction vessel is set to 8.0 Pa to 12.0 Pa. Next, a bias voltage of -400 V to -200 V is applied to the substrate, and the metal evaporation source corresponding to the metal component of the Z layer is evaporated by arc discharge with an arc current of 80 A to 150 A to form the Z layer.

[0047] To form a laminated structure in which laminated units containing a Y layer are repeatedly stacked between the X and Z layers, for example, a metal evaporation source corresponding to the metal component of the X layer, a metal evaporation source corresponding to the metal component of the Y layer, and a metal evaporation source corresponding to the metal component of the Z layer can be evaporated by arc discharge in a predetermined order under the conditions described above, thereby repeatedly forming laminated units containing a Y layer between the X and Z layers. The thickness of each layer constituting the laminated structure can be controlled by adjusting the arc discharge time of the metal evaporation source corresponding to the metal component of the X layer, the metal evaporation source corresponding to the metal component of the Y layer, and the metal evaporation source corresponding to the metal component of the Z layer.

[0048] In order to achieve a predetermined value for the overall composition of the compound in the laminated structure used in this embodiment, it is advisable to adjust the thickness of each layer in the laminated structure and the ratio of metal elements in each layer during the process of forming the laminated structure described above.

[0049] X-ray diffraction intensity ratio I in the coating layer used in this embodiment hex / I cub To set I to a predetermined value, for example, during the process of forming the laminated structure described above, it is advisable to adjust the temperature of the substrate, the pressure inside the reaction vessel, the bias voltage, or the atomic ratio of each metal element. More specifically, for example, during the process of forming the laminated structure, lowering the temperature of the substrate, increasing the pressure inside the reaction vessel, or increasing the negative bias voltage (moving away from zero) will result in I hex / I cubIt tends to become smaller. Also, in the process of forming a layered structure, if the atomic ratio of Al in each layer is reduced, or the atomic ratio of the element represented by M (at least one of Nb and Ta) in each layer is increased, I hex / I cub It tends to become smaller. Also, in the process of forming a layered structure, when two elements, Nb and Ta, are used as the element represented by M, if the proportion of Nb in the element represented by M is increased, I hex / I cub There is a tendency for it to become smaller.

[0050] When forming the upper layer used in this embodiment, it is preferable to form it under the same manufacturing conditions as the lower layer described above. That is, first, the temperature of the substrate is controlled until it reaches 200°C to 500°C. After control, gas is introduced into the reaction vessel to set the pressure inside the reaction vessel to 3.0 Pa to 8.0 Pa. As for the gas, for example, if the upper layer is composed of a compound consisting of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, B, and Y, and N, then N2 gas is an example. If the upper layer is composed of a compound consisting of at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, B, and Y, and C and N, then a mixed gas of N2 gas and C2H2 gas is an example. The volume ratio of the mixed gas is not particularly limited, but for example, N2 gas:C2H2 gas = 95:5 to 85:15 may be used. Next, a bias voltage of -200V to -40V is applied to the substrate, and an arc discharge with an arc current of 80A to 120A is used to evaporate a metal evaporation source corresponding to the metal, metalloid, and nonmetal components of each layer, thereby forming the upper layer. For example, when forming an upper layer containing at least one of elements B and C, a metal evaporation source containing elements B and / or C may be used as necessary.

[0051] The thickness of each layer constituting the coating layer in the coated cutting tool of this embodiment can be measured from the cross-sectional structure of the coated cutting tool using an optical microscope, scanning electron microscope (SEM), transmission electron microscope (TEM), etc. The average thickness of each layer in the coated cutting tool of this embodiment can be determined by measuring the thickness of each layer from three or more cross-sections near a position 50 μm from the cutting edge of the surface facing the metal evaporation source toward the center of the surface, and calculating the average value (arithmetic mean).

[0052] Furthermore, the composition of each layer constituting the coating layer in the coated cutting tool of this embodiment can be measured from the cross-sectional structure of the coated cutting tool of this embodiment using an energy-dispersive X-ray analyzer (EDS) or a wavelength-dispersive X-ray analyzer (WDS).

[0053] The coated cutting tools of this embodiment are thought to have the effect of extending tool life compared to conventional tools, at least due to their superior wear resistance and fracture resistance (however, the factors that can extend tool life are not limited to those mentioned above). Specifically, examples of the types of coated cutting tools of this embodiment include replaceable cutting inserts for milling or turning, drills, and end mills. [Examples]

[0054] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0055] (Example 1) As the base material, a cemented carbide alloy with a composition of 93.5%WC-6.2%Co-0.3%Cr3C2 (by mass%) was prepared, processed into an insert shape of CNMG120408-SM (manufactured by Tungaloy Corporation). A metal evaporation source was placed inside the reaction vessel of the arc ion plating apparatus to achieve the compound composition shown in Tables 1-3. The prepared base material was fixed to the fixing bracket of the rotary table inside the reaction vessel.

[0056] Subsequently, the pressure inside the reaction vessel reached 5.0 × 10-3 The system was evacuated until a vacuum of less than Pa was achieved. After evacuating, the substrate was heated in the reaction vessel using a heater until its temperature reached 450°C. After heating, Ar gas was introduced into the reaction vessel to bring the pressure down to 2.7 Pa.

[0057] Under an Ar gas atmosphere at a pressure of 2.7 Pa, a bias voltage of -400 V was applied to the substrate, and a current of 40 A was passed through the tungsten filament in the reaction vessel to perform ion bombardment treatment with Ar gas on the surface of the substrate for 30 minutes. After the ion bombardment treatment was completed, the pressure inside the reaction vessel was reduced to 5.0 × 10⁻⁶ -3 The system was evacuated until a vacuum of less than Pa was achieved.

[0058] For inventions 1-3, 7-37 and comparative products 1-9 and 12-13, a laminated unit consisting of an X layer, a Y layer, and a Z layer was formed on the surface of the substrate in the following order: for inventions 4-6, a laminated unit consisting of a Z layer, a Y layer, and an X layer was formed on the surface of the substrate in the following order: for inventions 38 and 39, a laminated unit consisting of an X layer, a Y layer, a Z layer, and a Y layer was formed on the surface of the substrate in the following order: for comparative product 10, a laminated unit consisting of an X layer and a Y layer was formed on the surface of the substrate in the following order: for comparative product 11, a laminated unit consisting of an X layer and a Z layer was formed on the surface of the substrate in the following order. First, after vacuuming, the substrate temperature was controlled to the temperatures shown in Tables 4 and 5 (temperature at the start of film formation), nitrogen gas (N2) was introduced into the reaction vessel, and the pressure inside the reaction vessel was adjusted to the pressures shown in Tables 4 and 5. Then, the bias voltages shown in Tables 4 and 5 were applied to the substrate, and the metal evaporation sources of each layer with the compositions shown in Tables 1 to 3 were evaporated by arc discharge with the arc currents shown in Tables 4 and 5, in the order of the stacked units described above, thereby forming stacked units consisting of the layers in the order described above on the surface of the substrate for the number of repetitions shown in Tables 1 to 3. At this time, the pressure inside the reaction vessel was controlled to be as shown in Tables 4 and 5. In addition, the thicknesses of layers X, Y, and Z were controlled by adjusting the respective arc discharge times so that they were the thicknesses shown in Tables 1 to 3. In Tables 1-3, the average thickness per layer of the X layer is denoted as t1, the average thickness per layer of the Y layer as t2, and the average thickness per layer of the Z layer as t3.

[0059] After forming a compound layer on the surface of the substrate to a predetermined average thickness as shown in Tables 1-3, the heater was turned off, and the sample was removed from the reaction vessel after the sample temperature had dropped below 100°C.

[0060] The average thickness of the compound layer in the obtained sample was determined by TEM observation of three cross-sections near a point 50 μm from the cutting edge of the surface facing the metal evaporation source of the coated cutting tool toward the center of the surface, measuring the thickness of the compound layer, and calculating the average value (arithmetic mean). The average thickness per layer of the X layer was calculated by dividing the total thickness obtained by summing the thicknesses of each X layer by the number of X layers (number of repetitions). Similarly, the average thickness per layer of the Y and Z layers was calculated by dividing the total thickness obtained by summing the thicknesses of each layer by the number of layers (number of repetitions). The results are shown in Tables 1 to 3.

[0061] The composition of each compound represented by formulas (1) to (3) of the obtained sample was measured using an EDS attached to a TEM at three cross-sections near the cutting edge of the surface facing the metal evaporation source of the coated cutting tool, within 50 μm from the cutting edge toward the center. Specifically, three arbitrary layered units were selected for each of the three cross-sections, and the composition of all X, Y, and Z layers contained in the selected layered units was analyzed. The average (arithmetic mean) of the obtained compositions of the X, Y, and Z layers was calculated for each compound. The differences in atomic ratios, (a3-a1), (a2-a1), and (b2-b1), were calculated by determining the differences in atomic ratios in the composition of each compound obtained from the measurement method. The results are also shown in Tables 1 to 3. Furthermore, the average composition of the entire compound of the layered structure represented by formula (4) (Al a M b Ti cThe values ​​of a, b, and c in N were measured using an EDS attached to the TEM. Specifically, surface analysis was performed on three cross-sections near the cutting edge of the surface facing the metal evaporation source of the coated cutting tool, from a position 50 μm toward the center, and the average value (arithmetic mean) was taken as the average composition. In this case, the measurement range of the surface analysis was set to "average thickness of the laminated structure" × "1 μm (length in the direction approximately parallel to the substrate surface) or more". These results are also shown in Tables 1 to 3.

[0062] [Table 1]

[0063] [Table 2]

[0064] [Table 3]

[0065] [Table 4]

[0066] [Table 5]

[0067] Ratio I in the layered structure of the obtained sample hex / I cubFor , measurements were carried out using an X-ray diffractometer of the type: SmartLab manufactured by Rigaku Corporation. Specifically, X-ray diffraction measurements were performed on a 2θ / θ focusing method optical system using Cu-Kα radiation, with the following conditions: output: 45 kV, 200 mA, incident side solar slit: 5°, divergence vertical slit: 2 / 3°, divergence vertical limiting slit: 5 mm, scattering slit: 2 / 3°, receiving side solar slit: 5°, receiving slit: 0.3 mm, sampling width: 0.01°, scan speed: 4° / min, 2θ measurement range: 25 to 70°. The integrated intensities of the peaks of the cubic (111) plane and the cubic (200) plane of the laminated structure were measured, and the integrated intensities of the peaks of the hexagonal (100) plane and the hexagonal (110) plane of the laminated structure were also measured. By doing so, the sum of the integrated intensities of the diffraction peaks of the cubic (111) plane and the cubic (200) plane was designated as I cub and the sum of the integrated intensities of the diffraction peaks of the hexagonal (100) plane and the hexagonal (110) plane was designated as I hex When calculating the ratio I hex / I cub . The results are shown in Tables 6 and 7. When determining the integrated intensities of the peaks of each of the above-mentioned plane indices from the X-ray diffraction pattern, the analysis software attached to the X-ray diffractometer was used. In the analysis software, background processing and Kα2 peak removal were performed using a third-degree polynomial approximation, profile fitting was performed using a Pearson-VII function, and the integrated intensity of each peak was determined. Also, the crystal system of the laminated structure was confirmed by X-ray diffraction measurement. More specifically, the integrated intensities of the peaks of the cubic (111) plane, cubic (200), hexagonal (100) plane, and hexagonal (110) plane of the laminated structure were measured as the measurement targets. At this time, instead of separating the peaks of the X layer, Y layer, and Z layer, the integrated intensity of the peak including both reflections was determined. For convenience, the ratio I hex / I cub was calculated from the integrated intensity of the peak obtained in this way, and I hex / I cub of the laminated structure was determined. The results are shown in Tables 6 and 7. For example, if the X-ray diffraction peak of the (111) plane of the cubic crystal originating from the layered structure was detected as a single peak, the integrated intensity of that single peak was used. If it was detected as two peaks, the sum of the integrated intensities of the two peaks was used as the integrated intensity of the X-ray diffraction peak of the (111) plane of the layered structure.

[0068] [Table 6]

[0069] [Table 7]

[0070] The obtained samples were used to perform the following cutting tests and evaluations.

[0071] [Cutting Test] Workpiece material: Inconel® 718 Workpiece shape: round bar Cutting speed: 80m / min Feed rate: 0.25mm / rev Cutting depth: 0.8mm Coolant: Water-soluble Evaluation criteria: Tool life was defined as the machining time until the wear width of the tool's flank surface exceeded 0.3 mm, or until the cutting edge broke. The damage morphology at the time of tool life was also observed using SEM. A longer machining time to tool life indicates superior wear resistance and fracture resistance. The results of the evaluation are shown in Tables 8 and 9.

[0072] [Table 8]

[0073] [Table 9]

[0074] The results shown in Tables 8 and 9 indicate that the invented product has superior wear resistance and fracture resistance compared to the comparative product, resulting in a longer tool life.

[0075] (Example 2) As the base material, a cemented carbide alloy with a composition of 93.5%WC-6.2%Co-0.3%Cr3C2 (by mass%) was prepared, processed into an insert shape of CNMG120408-SM (manufactured by Tungaloy Corporation). A metal evaporation source was placed inside the reaction vessel of the arc ion plating apparatus to achieve the compound composition shown in Tables 1-3. The prepared base material was fixed to the fixing bracket of the rotary table inside the reaction vessel.

[0076] Subsequently, the pressure inside the reaction vessel reached 5.0 × 10 -3 The system was evacuated until a vacuum of less than Pa was achieved. After evacuating, the substrate was heated in the reaction vessel using a heater until its temperature reached 450°C. After heating, Ar gas was introduced into the reaction vessel to bring the pressure down to 2.7 Pa.

[0077] Under an Ar gas atmosphere at a pressure of 2.7 Pa, a bias voltage of -400 V was applied to the substrate, and a current of 40 A was passed through the tungsten filament in the reaction vessel to perform ion bombardment treatment with Ar gas on the surface of the substrate for 30 minutes. After the ion bombardment treatment was completed, the pressure inside the reaction vessel was reduced to 5.0 × 10⁻⁶ -3 The system was evacuated until a vacuum of less than Pa was achieved.

[0078] For inventions 40-41 and 43-44, after vacuuming, the substrate temperature was controlled until it reached the temperature shown in Table 11 (the temperature at the start of film formation), N2 gas was introduced into the reaction vessel, and the pressure inside the reaction vessel was adjusted to the pressure shown in Table 11. For invention 42, after vacuuming, the substrate temperature was controlled until it reached the temperature shown in Table 11 (the temperature at the start of film formation), a mixed gas of N2 gas and C2H2 gas was introduced into the reaction vessel, and the pressure inside the reaction vessel was adjusted to the pressure shown in Table 11. Subsequently, the bias voltage shown in Table 11 was applied to the substrate, and the metal evaporation source corresponding to the lower layer composition shown in Table 10 was evaporated by arc discharge with the arc current shown in Table 11, thereby forming the lower layer on the surface of the substrate.

[0079] For invention 40, a laminated structure was formed on the surface of the lower layer under the same manufacturing conditions as invention 1; for invention 41, under the same manufacturing conditions as invention 27; for invention 42, under the same manufacturing conditions as invention 6; for invention 43, under the same manufacturing conditions as invention 1; and for invention 44, under the same manufacturing conditions as invention 10.

[0080] Next, for inventions 44-48, after vacuuming, the substrate temperature was controlled until it reached the temperature shown in Table 11 (the temperature at the start of film formation), N2 gas was introduced into the reaction vessel, and the pressure inside the reaction vessel was adjusted to the pressure shown in Table 11. Subsequently, the bias voltage shown in Table 11 was applied to the substrate, and the metal evaporation source corresponding to the composition of the upper layer shown in Table 10 was evaporated by arc discharge with the arc current shown in Table 11, thereby forming the upper layer on the surface of the laminated structure. After forming each layer on the substrate surface to the predetermined average thickness shown in Table 10, the heater was turned off, and the sample was removed from the reaction vessel after the sample temperature had dropped below 100°C.

[0081] The average thickness, composition, and ratio I of each layer in the obtained sample. hex / I cub The residual stress and other properties were measured and calculated in the same manner as in Example 1. The results are shown in Table 12. During the measurement, the peaks of the laminated structure were identified using the following methods (i) to (iii). (i) If the coating layer has an upper layer, the peaks of the laminated structure were identified by removing the upper layer by buff polishing. (ii) If the coating layer has a lower layer, the peaks of the stacked structure were identified by thin-film X-ray diffraction so as not to be affected by the lower layer. (iii) If the coating layer comprises an upper layer and a lower layer, the peaks of the laminated structure were identified by combining (i) and (ii) above.

[0082] [Table 10]

[0083] [Table 11]

[0084] [Table 12]

[0085] Using the obtained samples, a cutting test was performed in the same manner as in Example 1, and the inventive product was evaluated. The results are shown in Table 13.

[0086] [Table 13]

[0087] The results shown in Table 13 indicate that the invention further having at least one of the lower layer and the upper layer exhibits even greater wear resistance and fracture resistance, and has an even longer tool life. [Industrial applicability]

[0088] The coated cutting tool of the present invention has excellent wear resistance and fracture resistance, which extends tool life compared to conventional tools, and therefore has high potential for industrial application. [Explanation of Symbols]

[0089] 1...Coated cutting tool, 2...Base material, 3...Coating layer, 4...Laminated structure, 41...X layer, 42...Y layer, 43...Z layer.

Claims

1. A coated cutting tool comprising a base material and a coating layer formed on the base material, The coating layer includes a laminated structure in which a laminated unit containing a Y layer is repeatedly stacked between the X layer and the Z layer. The aforementioned X layer contains a compound having a composition represented by the following formula (1): (A) a1 M b1 Ti c1 (N) (1) (In formula (1), M represents at least one of the elements Nb and Ta, a1 is the atomic ratio of Al to the sum of the elements represented by M and Ti. Satisfying 0.60 ≤ a1 < 0.75, b1 is the atomic ratio of the element represented by M to the sum of the elements Al, M, and Ti. Satisfying 0.00 ≤ b1 ≤ 0.20, c1 is the atomic ratio of the Ti element to the sum of the Al element, the element represented by M, and the Ti element. Satisfying 0.20 ≤ c1 ≤ 0.40, a1 + b1 + c1 = 1. The aforementioned Y layer contains a compound having a composition represented by the following formula (2): (A) a2 M b2 Ti c2 (N) (2) (In formula (2), M represents at least one of the elements Nb and Ta, a2 is the atomic ratio of Al to the sum of the elements represented by M and Ti. Satisfying 0.75 ≤ a² ≤ 0.95, b2 is the atomic ratio of the element represented by M to the sum of the elements Al, M, and Ti. Satisfying 0.03 ≤ b² ≤ 0.20, c2 is the atomic ratio of the Ti element to the sum of the Al element, the element represented by M, and the Ti element. Satisfying 0.00 ≤ c² ≤ 0.22, a² + b² + c² = 1. The Z layer contains a compound having the composition represented by the following formula (3): (A) a3 M b3 Ti c3 (N (3)) (In formula (3), M represents at least one of the elements Nb and Ta, a3 is the atomic ratio of Al to the sum of the elements represented by M and Ti. Satisfying 0.80 ≤ a3 ≤ 0.95, b3 is the atomic ratio of the element represented by M to the sum of the elements Al, M, and Ti. Satisfying 0.00 ≤ b3 < 0.03, c3 is the atomic ratio of Ti to the sum of Al, the element represented by M, and the Ti element. Satisfying 0.05 ≤ c3 ≤ 0.20, a³ + b³ + c³ = 1. A coated cutting tool having an average thickness of 0.5 μm or more and 5.0 μm or less of the aforementioned laminated structure.

2. The coated cutting tool according to claim 1, wherein a1 and a3 satisfy 0.05 < (a3 - a1) ≤ 0.

25.

3. The coated cutting tool according to claim 1 or 2, wherein a1 and a2 satisfy 0.05 ≤ (a2 - a1) ≤ 0.

25.

4. The coated cutting tool according to claim 1 or 2, wherein b1 and b2 satisfy 0.02 ≤ (b2 - b1) ≤ 0.

15.

5. The coated cutting tool according to claim 1 or 2, wherein the average composition of the entire compound in the aforementioned layered structure is represented by the following formula (4). (A) a M b Ti c )N (4) (In formula (4), M represents at least one of the elements Nb and Ta, a is the atomic ratio of Al to the sum of the elements represented by M and Ti. Satisfying 0.70 ≤ a ≤ 0.85, b is the atomic ratio of the element represented by M to the sum of the elements Al, M, and Ti. Satisfying 0.00 < b ≤ 0.15, c is the atomic ratio of Ti to the sum of Al, the element represented by M, and the Ti element. Satisfying 0.10 ≤ c ≤ 0.25, a + b + c = 1.

6. In the X-ray diffraction of the aforementioned layered structure, the sum of the integrated intensities of the diffraction peaks of the cubic (111) plane and the cubic (200) plane is I cub The sum of the integrated intensities of the diffraction peaks of the hexagonal (100) plane and the hexagonal (110) plane is calculated as I hex In that case, I hex / I cub The coated cutting tool according to claim 1 or 2, wherein the coefficient is 0.00 or more and 0.40 or less.

7. The coated cutting tool according to claim 1 or 2, wherein the average thickness per layer of the X layer is 2 nm or more and 300 nm or less, the average thickness per layer of the Y layer is 2 nm or more and 300 nm or less, and the average thickness per layer of the Z layer is 2 nm or more and 300 nm or less.

8. The coating layer has a lower layer between the substrate and the laminated structure. The lower layer is a single or multilayer compound comprising at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, B, and Y, and at least one element selected from the group consisting of C, N, and O (however, a compound different from the compound contained in the laminated structure). The coated cutting tool according to claim 1 or 2, wherein the average thickness of the lower layer is 0.1 μm or more and 2.0 μm or less.

9. The coating layer has an upper layer on the surface opposite to the substrate in the laminated structure, The upper layer is a single or multilayer compound comprising at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, B, and Y, and at least one element selected from the group consisting of C, N, and O (however, a compound different from the compound contained in the laminated structure). The coated cutting tool according to claim 1 or 2, wherein the average thickness of the upper layer is 0.1 μm or more and 2.0 μm or less.

10. The coated cutting tool according to claim 1 or 2, wherein the average thickness of the entire coating layer is 0.5 μm or more and 5.0 μm or less.

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