Cutting Tools

Abstract

A cutting tool includes a substrate and a coating disposed on the substrate, wherein the coating comprises: a first alumina layer disposed on the substrate; a titanium compound layer disposed directly above the first alumina layer; and a second alumina layer disposed directly above the titanium compound layer. In the first alumina layer, a portion adjacent to the titanium compound layer forms an interface region, and a portion of the first alumina layer not comprising the interface region forms a non-interface region. The nitrogen content in the interface region is 0.2 at% or more and 12 at% or less, and the nitrogen content in the non-interface region is 0 at% or more and 0.15 at% or less. The titanium compound layer comprises a multilayer structure adjacent to the first alumina layer, the multilayer structure being composed of a first unit layer and a second unit layer, wherein the first unit layer and the second unit layer are alternately stacked, the first unit layer being composed of titanium carbonitride, and the second unit layer being composed of titanium carbonitride.

Description

Technical Field

[0001] The present disclosure relates to cutting tools. Background Art

[0002] Cutting tools having a coating on a substrate have long been used. For example, Japanese Patent Publication No. 2020-037150 (Patent Document 1) discloses a coated cutting tool comprising a substrate and a coating layer formed on the surface of the substrate, wherein the coating layer comprises a lower layer, an intermediate layer, and an upper layer stacked in sequence from the substrate side toward the surface side of the coating layer, the lower layer comprises one or more Ti compound layers formed of Ti and a Ti compound of at least one element selected from the group consisting of C, N, O, and B, and the intermediate layer comprises α-type Al2 O3, the upper layer contains TiCN, the average thickness of the lower layer is greater than 4.0μm and less than 10.0μm, the average thickness of the middle layer is greater than 3.0μm and less than 10.0μm, the average thickness of the upper layer is greater than 1.5μm and less than 6.5μm, the length of the Σ3 grain boundary in a specific area of ​​the upper layer is greater than 20% and less than 60% relative to the total length of all grain boundaries (100%), and the proportion of particles on the (111) plane of the upper layer is greater than 30 area%.

[0003] In addition, Japanese Patent Gazette No. 2003-266213 (Patent Document 2) discloses a boron-containing film coated tool, characterized in that a boron-containing film is coated on the surface of a substrate formed of cemented carbide, high-speed steel or special steel at a position closer to the tool surface side than the aluminum oxide film, and the boron-containing film is composed of a single-layer film or a multi-layer film of any one of carbides, nitrides, carbonitrides, carbon oxides, nitrogen oxides, and carbonitride oxides composed of one or more of boron and one or more of the metals of Groups 4a, 5a, and 6a of the periodic table, and has tensile residual stress.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-037150

[0007] Patent Document 2: Japanese Patent Application Publication No. 2003-266213 Summary of the invention

[0008] The cutting tool according to the present disclosure comprises a substrate and a coating provided on the substrate, wherein:

[0009] The above-mentioned coating includes:

[0010] A first aluminum oxide layer, which is disposed on the substrate;

[0011] a titanium compound layer disposed directly above the first aluminum oxide layer; and

[0012] a second aluminum oxide layer disposed directly above the titanium compound layer;

[0013] In the first aluminum oxide layer, a portion adjacent to the titanium compound layer forms an interface region,

[0014] In the first aluminum oxide layer, a portion other than the interface region forms a non-interface region.

[0015] The nitrogen content in the interface region is 0.2 at % or more and 12 at % or less,

[0016] The nitrogen content in the non-interface region is 0 at % or more and 0.15 at % or less,

[0017] The titanium compound layer includes a multilayer structure layer adjacent to the first aluminum oxide layer.

[0018] The multi-layer structure layer is composed of a first unit layer and a second unit layer.

[0019] In the multilayer structure, the first unit layers and the second unit layers are alternately stacked.

[0020] The first unit layer is composed of titanium carbonitride.

[0021] The second unit layer is composed of titanium oxycarbonitride. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a perspective view showing an example of one embodiment of a base material of a cutting tool.

[0023] Figure 2 This is a schematic cross-sectional view of a cutting tool in one form of the present embodiment.

[0024] Figure 3 This is a schematic cross-sectional view of a cutting tool in another form of the present embodiment.

[0025] Figure 4 This is a schematic cross-sectional view of a coating layer in one form of the present embodiment.

[0026] Figure 5 This is a schematic cross-sectional view showing an example of a chemical vapor deposition apparatus used for producing a coating film.

[0027] Figure 6 These are photographs showing the grades corresponding to the surface quality of the processed surface. DETAILED DESCRIPTION

[0028] [Problems to be Solved by the Present Disclosure]

[0029] In Patent Documents 1 and 2, it is expected that the wear resistance and the adhesion between the aluminum oxide layer and other layers in contact with the aluminum oxide layer will be improved by using the coating having the above-mentioned structure, thereby extending the life of the cutting tool.

[0030] However, in recent years, the cutting process has been progressing at a higher speed and with a higher efficiency, and the load applied to the cutting tool has increased, and there is a tendency for the life of the cutting tool to become shorter. Therefore, it is required to further improve the mechanical properties of the coating of the cutting tool (for example, wear resistance, welding resistance, and defect resistance, etc.).

[0031] The present disclosure has been made in view of the above circumstances, and an object of the present invention is to provide a cutting tool having improved wear resistance and defect resistance.

[0032] [Effects of the present disclosure]

[0033] According to the present disclosure, it is possible to provide a cutting tool having improved wear resistance and defect resistance.

[0034] [Description of Embodiments of the Present Disclosure]

[0035] First, embodiments of the present disclosure will be described by way of examples.

[0036] [1] The cutting tool according to the present disclosure comprises a substrate and a coating provided on the substrate, wherein:

[0037] The above-mentioned coating includes:

[0038] A first aluminum oxide layer, which is disposed on the substrate;

[0039] a titanium compound layer disposed directly above the first aluminum oxide layer; and

[0040] a second aluminum oxide layer disposed directly above the titanium compound layer;

[0041] In the first aluminum oxide layer, a portion adjacent to the titanium compound layer forms an interface region,

[0042] In the first aluminum oxide layer, a portion other than the interface region forms a non-interface region.

[0043] The nitrogen content in the interface region is 0.2 at % or more and 12 at % or less,

[0044] The nitrogen content in the non-interface region is 0 at % or more and 0.15 at % or less,

[0045] The titanium compound layer includes a multilayer structure layer adjacent to the first aluminum oxide layer.

[0046] The multi-layer structure layer is composed of a first unit layer and a second unit layer.

[0047] In the multilayer structure, the first unit layers and the second unit layers are alternately stacked.

[0048] The first unit layer is composed of titanium carbonitride.

[0049] The second unit layer is composed of titanium oxycarbonitride.

[0050] The above-mentioned cutting tool has improved wear resistance and defect resistance by having the above-mentioned structure. Here, "wear resistance" refers to the resistance to the situation that the coating is worn when used for cutting. "Defect resistance" refers to the resistance to the situation that the coating is defective when used for cutting.

[0051] The above-mentioned cutting tool is used for cutting processes such as turning, but it is known that the highest temperature during turning is not the edge portion (the edge line portion of the blade tip) of the cutting tool but the portion slightly away from the edge (the portion contacted by the chips). In this case, high hardness is required for the edge portion, but heat resistance and defect resistance are required for the portion slightly away from the edge. However, the coating has not been designed so far in consideration of the properties required for the edge and the portion away from the edge of the cutting tool. In the present disclosure, by further providing a titanium compound layer and a second aluminum oxide layer on the basis of the first aluminum oxide layer, the properties required for the edge and the portion away from the edge of the cutting tool are successfully taken into account.

[0052] [2] Preferably, the thickness of the first aluminum oxide layer is greater than the thickness of the second aluminum oxide layer. By specifying in this way, a cutting tool having excellent heat resistance is obtained.

[0053] [3] Preferably, the thickness of the titanium compound layer is 1 μm or more and 11 μm or less. By defining the thickness in this way, the wear resistance is further improved.

[0054] [4] Preferably, the thickness of the second aluminum oxide layer is not less than 0.2 μm and not more than 6.5 μm. By specifying in this way, the defect resistance is further improved.

[0055] [5] Preferably, the thickness of the first aluminum oxide layer is 2.5 μm or more and 20.5 μm or less. By defining the thickness in this way, a cutting tool having excellent wear resistance is obtained.

[0056] [6] Preferably, the interface region of the first aluminum oxide layer is a region sandwiched between the interface S between the first aluminum oxide layer and the titanium compound layer and an imaginary plane A parallel to the interface S and passing through a point 0.5 μm away from the interface S in the thickness direction. By defining in this way, a cutting tool having excellent defect resistance is formed.

[0057] [7] Preferably, the nitrogen content in the interface region of the first aluminum oxide layer is 0.5 at % or more and 10 at % or less. By specifying in this way, a cutting tool having excellent adhesion between the first aluminum oxide layer and the titanium compound layer can be provided.

[0058] [8] Preferably, the thickness of the second aluminum oxide layer is 0.2 μm to 6.5 μm, and the residual stress of the titanium compound layer is -3 GPa to 0 GPa. By specifying in this way, a cutting tool with better wear resistance can be provided.

[0059] [9] Preferably, the bottommost layer of the multilayer structure layer is the second unit layer. By defining in this way, a cutting tool having excellent defect resistance is obtained.

[0060]

[10] Preferably, the titanium compound layer further includes a layer of titanium nitride or titanium carbide. By defining in this way, a cutting tool having excellent wear resistance is obtained.

[0061] [Details of the embodiments of the present disclosure]

[0062] An embodiment of the present disclosure (hereinafter referred to as "this embodiment") is described below. However, this embodiment is not limited thereto. In this specification, expressions in the form of "X to Z" refer to the upper and lower limits of a range (i.e., greater than X and less than Z). When there is no unit recorded in X and only a unit is recorded in Z, the unit of X is the same as the unit of Z. Furthermore, in this specification, when a compound is represented by a chemical formula in which the composition ratio of the constituent elements is not limited, such as "TiC", the chemical formula includes all previously known composition ratios (element ratios). In this case, the above chemical formula includes not only stoichiometric compositions, but also non-stoichiometric compositions. For example, the chemical formula of "TiC" includes not only the stoichiometric composition "Ti1C1", but also, for example, "Ti1C 0.8 " This is a non-stoichiometric composition. The same applies to the description of compounds other than "TiC".

[0063] Cutting Tools

[0064] The cutting tool according to the present disclosure comprises a substrate and a coating provided on the substrate.

[0065] The above-mentioned coating includes:

[0066] A first aluminum oxide layer, which is disposed on the substrate;

[0067] a titanium compound layer disposed directly above the first aluminum oxide layer; and

[0068] a second aluminum oxide layer disposed directly above the titanium compound layer;

[0069] In the first aluminum oxide layer, a portion adjacent to the titanium compound layer forms an interface region,

[0070] In the first aluminum oxide layer, a portion other than the interface region forms a non-interface region.

[0071] The nitrogen content in the interface region is 0.2 at % or more and 12 at % or less,

[0072] The nitrogen content in the non-interface region is 0 at % or more and 0.15 at % or less,

[0073] The titanium compound layer includes a multilayer structure layer adjacent to the first aluminum oxide layer.

[0074] The multi-layer structure layer is composed of a first unit layer and a second unit layer.

[0075] In the multilayer structure, the first unit layers and the second unit layers are alternately stacked.

[0076] The first unit layer is composed of titanium carbonitride.

[0077] The second unit layer is composed of titanium oxycarbonitride.

[0078] The cutting tool 50 of the present embodiment includes a substrate 10 and a coating 40 (hereinafter sometimes simply referred to as a “cutting tool”) provided on the substrate 10. Figure 2 The coating 40 includes a first aluminum oxide layer 20 disposed on the substrate 10, a titanium compound layer 21 disposed directly above the first aluminum oxide layer 20, and a second aluminum oxide layer 22 disposed directly above the titanium compound layer 21. In addition to the above layers, the cutting tool 50 may further include a base layer 23 ( Figure 3 The cutting tool 50 may further include a surface layer provided on the second aluminum oxide layer 22. The other layers such as the base layer 23 and the surface layer will be described later.

[0079] The cutting tool (hereinafter sometimes simply referred to as “cutting tool”) 50 of the present embodiment includes a substrate 10 and a coating 40 (see FIG. 4 ) covering the substrate 10. Figure 2 , Figure 3 In one aspect of the present embodiment, the coating may cover the front cutting edge of the substrate, or may cover a portion other than the front cutting edge (e.g., the back cutting edge). The cutting tool may be, for example, a drill, an end mill, an indexable insert type cutting insert for a drill, an indexable insert type cutting insert for an end mill, an indexable insert type cutting insert for milling, an indexable insert type cutting insert for turning, a metalworking saw, a gear cutting tool, a reamer, a tap, etc.

[0080] <Base Material>

[0081] The substrate of the present embodiment can be any substrate as long as it is conventionally known as such a substrate. For example, the substrate preferably includes at least one selected from the group consisting of cemented carbide (e.g., tungsten carbide (WC)-based cemented carbide, cemented carbide containing Co in addition to WC, cemented carbide to which carbonitrides such as Cr, Ti, Ta, Nb, etc. are added in addition to WC, etc.), cermet (cermet with TiC, TiN, TiCN, etc. as the main component), high-speed steel, ceramic (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cubic boron nitride sintered body (cBN sintered body), and diamond sintered body, and more preferably includes at least one selected from the group consisting of cemented carbide, cermet, and cBN sintered body.

[0082] Among these various substrates, WC-based cemented carbide or cBN sintered body is particularly preferably selected because these substrates have an excellent balance between hardness and strength, especially at high temperatures, and have excellent properties as substrates for cutting tools for the above-mentioned purposes.

[0083] When using cemented carbide as a substrate, such a cemented carbide, even if it contains free carbon or an abnormal phase called η phase in the structure, also shows the effect of the present embodiment. In addition, the substrate used in the present embodiment can also be a substrate whose surface is modified. For example, in the case of cemented carbide, a de-β layer can be formed on its surface, and in the case of a cBN sintered body, a surface hardening layer can be formed, even if the surface is modified like this, also shows the effect of the present embodiment.

[0084] Figure 1 This is a stereoscopic diagram showing an example of a substrate for a cutting tool. A substrate of such a shape is used, for example, as a substrate for an indexable insert type cutting insert for turning. The substrate 10 has a rake face 1, a flank face 2, and a blade edge line portion 3 where the rake face 1 and the flank face 2 intersect. That is, the rake face 1 and the flank face 2 are surfaces connected by sandwiching the blade edge line portion 3. The blade edge line portion 3 constitutes the front end portion of the cutting edge of the substrate 10. The shape of such a substrate 10 can also be understood as the shape of the above-mentioned cutting tool.

[0085] In the case where the cutting tool is an indexable insert type cutting insert, the substrate 10 includes a shape with a chip breaker and a shape without a chip breaker. The shape of the blade edge line portion 3 includes any one of a sharp edge (a ridge where the front cutting surface and the back cutting surface intersect), a honing (a shape in which a circular arc is given to the sharp edge), a negative land (a shape with chamfering), and a shape in which honing and a negative land are combined.

[0086] Above, use Figure 1 The shape of the substrate 10 and the names of the parts have been described, but in the cutting tool 50 involved in this embodiment, the same terms as above are used for the shape and the names of the parts corresponding to the substrate 10. That is, the cutting tool has a rake face, a flank face, and a cutting edge line portion connecting the rake face and the flank face.

[0087] <Lamination>

[0088] The coating 40 according to the present embodiment includes a first aluminum oxide layer 20 provided on the substrate 10, a titanium compound layer 21 provided directly above the first aluminum oxide layer 20, and a second aluminum oxide layer 22 provided directly above the titanium compound layer 21 (see Figure 2 ). The "coating" has the function of improving the defect resistance, wear resistance, welding resistance and other properties of the cutting tool by covering at least a portion of the above-mentioned substrate (for example, the front cutting face that contacts the cut material during cutting). The above-mentioned coating is not limited to covering a portion of the above-mentioned substrate, and preferably covers the entire surface of the above-mentioned substrate. However, even if a portion of the above-mentioned substrate is not covered by the above-mentioned coating, or the composition of the coating is partially different, it does not deviate from the scope of this embodiment.

[0089] The thickness of the above-mentioned film is preferably more than 10μm and less than 40μm, and more preferably more than 15μm and less than 35μm. Here, the thickness of the film refers to the sum of the thicknesses of the layers constituting the film. As "layers constituting the film", for example, the first aluminum oxide layer, titanium compound layer, second aluminum oxide layer, base layer and surface layer described later can be listed. The thickness of the above-mentioned film can be measured, for example, by using a field emission scanning electron microscope (SEM) to measure any ten points in a cross-sectional sample parallel to the normal direction of the surface of the substrate, and taking the average value of the thickness of the ten points measured. At this time, the measured cross section of the above-mentioned cross-sectional sample is ground by ion milling. The same is true for measuring the thickness of the first aluminum oxide layer, titanium compound layer, second aluminum oxide layer, base layer and surface layer described later. As a field emission scanning electron microscope, for example, SU3500 (trade name) manufactured by Hitachi High-Technologies Co., Ltd. can be listed. As an apparatus for performing ion milling treatment, for example, IM4000 (trade name) manufactured by Hitachi High-Technologies Corporation can be cited.

[0090] (First Aluminum Oxide Layer)

[0091] The first aluminum oxide layer 20 in this embodiment is disposed on the substrate 10. Here, "disposed on the substrate" is not limited to being disposed directly above the substrate (see Figure 2 ), and also includes a method of being provided on a substrate through other layers (refer to Figure 3 That is, as long as the effects of the present disclosure are achieved, the first aluminum oxide layer may be provided directly above the substrate, or may be provided on the substrate via other layers such as a base layer described later.

[0092] The first aluminum oxide layer may be composed of aluminum oxide (Al2O3) alone or may be composed of aluminum oxide and inevitable impurities. Examples of the inevitable impurities include chlorine and sulfur. The aluminum oxide is preferably α-type aluminum oxide (α-Al2O3).

[0093] (Nitrogen Content Ratio in the Interface Region and Non-Interface Region of the First Aluminum Oxide Layer)

[0094] In the first aluminum oxide layer, a portion adjacent to the titanium compound layer forms an interface region. In addition, in the first aluminum oxide layer, a portion other than the interface region forms a non-interface region. The interface region of the first aluminum oxide layer is preferably a region sandwiched between an interface S between the first aluminum oxide layer and the titanium compound layer and an imaginary plane A parallel to the interface S and passing through a point 0.5 μm away from the interface S in the thickness direction ( Figure 4The non-interface region of the first aluminum oxide layer is preferably a region sandwiched between the imaginary plane A and the interface Q on the substrate side of the first aluminum oxide layer ( Figure 4 ). In addition, in the first aluminum oxide layer, there may or may not be a clear boundary between the interface region and the non-interface region.

[0095] The nitrogen content in the interface region of the first aluminum oxide layer is greater than 0.2 at% and less than 12 at%, preferably greater than 0.5 at% and less than 10 at%, and more preferably greater than 1 at% and less than 9 at%. Here, the nitrogen content is an atomic ratio based on the total of aluminum, oxygen, and nitrogen in the first aluminum oxide layer.

[0096] In the first aluminum oxide layer having the above-mentioned structure, nitrogen atoms are concentrated in the interface region between the first aluminum oxide layer and the titanium compound layer. Therefore, nitrogen atoms diffuse from the interface region to the titanium compound layer to improve the adhesion between the first aluminum oxide layer and the titanium compound layer. In the past, the titanium compound layer provided on the aluminum oxide layer was only required to function as a layer indicating the state of use, so the adhesion with the above-mentioned aluminum oxide layer and other mechanical properties were not taken seriously. In addition, it is known that if nitrogen exists inside the aluminum oxide layer, it becomes thermally unstable, which reduces the performance of the aluminum oxide layer. Therefore, nitrogen has not been actively added inside the aluminum oxide layer in the past.

[0097] In the present disclosure, nitrogen atoms are localized in the interface region of the first aluminum oxide layer to improve adhesion with the titanium compound layer (especially the multilayer structure layer adjacent to the first aluminum oxide layer), and furthermore, predetermined mechanical properties can be imparted to the titanium compound layer.

[0098] The nitrogen content ratio can be obtained by performing line analysis on a cross-sectional sample parallel to the normal direction of the surface of the above-mentioned substrate using the Auger electron spectroscopy method (AES method). Specifically, first, the cut surface of the above-mentioned cross-sectional sample is ground by cross-sectional polishing (CP processing) and the like. For the cut surface after grinding, a cross-sectional SEM image of the substrate (under the condition of being provided with an underlayer), the first aluminum oxide layer and the titanium compound layer is obtained by using a field emission scanning microscope (FE-SEM) for analysis. The measurement magnification at this time is 50,000 times. At this time, the substrate, the underlayer and the titanium compound layer are observed as darker areas, and the first aluminum oxide layer is observed as a brighter area. Then, in the field of view of the above-mentioned cross-sectional SEM image, in a direction parallel to the stacking direction of the above-mentioned titanium compound layer, from the titanium compound layer side toward the first aluminum oxide layer side, the cut surface after grinding is analyzed by the AES method. The measurement spacing at this time is 0.016 μm. In addition, other measurement conditions of the AES method are the following conditions. As a measuring apparatus of the AES method, PHI700 (trade name) manufactured by ULVAC-PHI Corporation is mentioned, for example.

[0099] (Measurement conditions of AES method)

[0100] Measurement acceleration voltage: 10kV

[0101] Measuring current: 10mA

[0102] Sample tilt angle: 30°

[0103] Sputtering voltage: 1kV

[0104] Next, based on the results of the above-mentioned line analysis, a graph was prepared in which the distance from the measurement start point was set as the X-axis (horizontal axis) and the atomic ratio (at%) of each element of the measurement object was set as the Y-axis (vertical axis). Based on this graph, the location where the atomic ratio of aluminum was 10 at% and the location closer to the above-mentioned titanium compound layer was set as the "interface S between the first aluminum oxide layer and the titanium compound layer" (refer to Figure 4 ). In addition, a plane including a point 0.5 μm away from the interface S toward the first aluminum oxide layer is defined as a “virtual plane A” (refer to Figure 4 ). Then, based on the above graph, the average value of the atomic ratio of nitrogen in the region (interface region) sandwiched between the interface S and the virtual plane A is determined.

[0105] The above-described measurement is performed at least three times, and the average value of the values ​​obtained in the respective measurements is defined as the nitrogen content ratio in the interface region of the first aluminum oxide layer.

[0106] The nitrogen content ratio in the above-mentioned non-interface region of the above-mentioned first aluminum oxide layer is greater than 0at% and less than 0.15at%, preferably greater than 0at% and less than 0.1at%. The nitrogen content ratio in the above-mentioned non-interface region can be obtained by performing line analysis on the cross-sectional sample using the AES method in the same manner as described above. At this time, in the graph obtained based on the results of the above-mentioned line analysis, the location where the atomic ratio of aluminum is 10at% and the location closer to the above-mentioned substrate is set as the "interface Q on the substrate side of the first aluminum oxide layer" (refer to Figure 4 ). Then, based on the above graph, the average value of the atomic ratio of the nitrogen in the region (non-interface region) sandwiched between the imaginary plane A and the interface Q is calculated. The above measurement is performed at least three times, and the average value of the values ​​calculated in each measurement is used as the nitrogen content ratio in the non-interface region of the first aluminum oxide layer.

[0107] The thickness of the first aluminum oxide layer is preferably 2.5 μm to 20.5 μm, more preferably 3 μm to 20 μm, and more preferably 6 μm to 17 μm. The thickness of the first aluminum oxide layer can be confirmed by observing the vertical cross section of the substrate and the coating using SEM in the same manner as above.

[0108] In one aspect of the present embodiment, the thickness of the first aluminum oxide layer is preferably greater than the thickness of the second aluminum oxide layer described below.

[0109] (Titanium compound layer)

[0110] The titanium compound layer 21 according to this embodiment is provided directly above the first aluminum oxide layer 20 ( Figure 2 ). The titanium compound layer includes a multilayer structure layer adjacent to the first aluminum oxide layer. In one aspect of the present embodiment, it can also be understood that the multilayer structure layer is arranged directly above the first aluminum oxide layer. The titanium compound layer can be composed only of the multilayer structure layer adjacent to the first aluminum oxide layer, or it can be composed of the multilayer structure layer adjacent to the first aluminum oxide layer and a layer of other titanium compounds. The thickness of the titanium compound layer is preferably greater than 1 μm and less than 11 μm, more preferably greater than 1.5 μm and less than 9.5 μm, and further preferably greater than 2.5 μm and less than 8.5 μm. The thickness of the titanium compound layer is thinner than before. However, as described later, the titanium compound layer has a predetermined residual stress and thus becomes a layer with sufficient hardness. The thickness of the titanium compound layer can be confirmed by observing the vertical cross-section of the substrate and the coating using SEM using the same method as above.

[0111] In this embodiment, the multilayer structure layer 24 is composed of a first unit layer 24a and a second unit layer 24b ( Figure 2). In the above-mentioned multilayer structural layer, the above-mentioned first unit layer and the above-mentioned second unit layer are stacked alternately. In one aspect of the present embodiment, the bottom layer of the above-mentioned multilayer structural layer is preferably the above-mentioned second unit layer. In another aspect of the present embodiment, the top layer of the above-mentioned multilayer structural layer can be the above-mentioned first unit layer or the above-mentioned second unit layer. Here, the "bottom layer" refers to the layer closest to the above-mentioned substrate among the layers constituting the above-mentioned multilayer structural layer. The "top layer" refers to the layer farthest from the above-mentioned substrate among the layers constituting the above-mentioned multilayer structural layer.

[0112] The thickness of the multilayer structure layer is preferably 1 μm to 11 μm, more preferably 1.5 μm to 9.5 μm, and further preferably 3.0 μm to 8.0 μm. The thickness of the multilayer structure layer can be confirmed by observing the vertical cross section of the substrate and the coating using SEM in the same manner as above.

[0113] The first unit layer is composed of titanium carbonitride (TiCN). The first unit layer may be composed of titanium carbonitride alone or may be composed of titanium carbonitride and inevitable impurities. Examples of the inevitable impurities include oxygen and chlorine.

[0114] The thickness of the first unit layer is preferably 50 nm or more and 2000 nm or less, more preferably 100 nm or more and 1000 nm or less, and further preferably 300 nm or more and 700 nm or less. The thickness of the first unit layer can be confirmed by observing the vertical cross-section of the substrate and the coating using SEM using the same method as described above. The magnification at this time is, for example, 20,000 times. In the case where the multilayer structure layer contains more than two first unit layers, the thickness of each first unit layer is first obtained by the above method, and the average value of the obtained value (that is, the average value of multiple first unit layers) is used as the thickness of the first unit layer in the multilayer structure layer. When the first unit layer contained in the multilayer structure layer exceeds ten layers, in the ten first unit layers selected arbitrarily, the thickness of each of the ten first unit layers is obtained by the above method, and the average value of the values ​​obtained by each first unit layer is used as the thickness of the first unit layer in the multilayer structure layer.

[0115] The second unit layer is composed of titanium oxycarbonitride (TiCNO). The second unit layer may be composed of titanium oxycarbonitride alone or may be composed of titanium oxycarbonitride and inevitable impurities. Examples of the inevitable impurities include oxygen and chlorine.

[0116] The thickness of the second unit layer is preferably 50 nm or more and 2000 nm or less, more preferably 100 nm or more and 1000 nm or less, and further preferably 300 nm or more and 700 nm or less. The thickness of the second unit layer can be confirmed by observing the vertical cross-section of the substrate and the coating using SEM in the same manner as described above. The magnification at this time is, for example, 20,000 times. In the case where the multilayer structure layer contains more than two second unit layers, the thickness of each second unit layer is first obtained by the above method, and the average value of the obtained value (that is, the average value of multiple second unit layers) is used as the thickness of the second unit layer in the multilayer structure layer. In the case where the second unit layer contained in the multilayer structure layer exceeds ten layers, in the ten second unit layers selected arbitrarily, the thickness of each of the ten second unit layers is obtained by the above method, and the average value of the values ​​obtained by each second unit layer is used as the thickness of the second unit layer in the multilayer structure layer.

[0117] In one aspect of the present embodiment, the titanium compound layer preferably further includes a layer of titanium nitride (TiN) or titanium carbide (TiC).

[0118] The thickness of the titanium nitride or titanium carbide layer is preferably 0.5 μm to 5.5 μm, more preferably 0.5 μm to 2.5 μm. The thickness of the titanium nitride or titanium carbide layer can be confirmed by observing the vertical cross section of the substrate and the coating using SEM in the same manner as above.

[0119] The residual stress of the titanium compound layer is preferably from -3 GPa to 0 GPa, and more preferably from -2.5 GPa to -0.5 GPa.

[0120] Here, "residual stress" is a kind of internal stress (intrinsic strain) existing in the layer. As the above-mentioned residual stress, it is roughly divided into compressive residual stress and tensile residual stress. Compressive residual stress refers to the residual stress represented by a "-" (negative) numerical value (in this specification, its unit is expressed by "GPa"). For example, "10GPa of compressive residual stress" can be understood as a residual stress of -10GPa. Therefore, the concept of a larger compressive residual stress means that the absolute value of the above numerical value becomes larger, and the concept of a smaller compressive residual stress means that the absolute value of the above numerical value becomes smaller. Tensile residual stress refers to the residual stress represented by a "+" (positive) numerical value (in this specification, its unit is expressed by "GPa"). For example, "10GPa of tensile residual stress" can be understood as a residual stress of 10GPa. Therefore, the concept of a larger tensile residual stress means that the above numerical value becomes larger, and the concept of a smaller tensile residual stress means that the above numerical value becomes smaller.

[0121] In this embodiment, the residual stress of the titanium compound layer is determined by using X-ray based 2θ-sin 2 The residual stress can be obtained by the ψ method. As a specific method, first, the 2θ-sin 2 The ψ method measures the crystal plane spacing of the diffraction plane of titanium carbonitride, namely the (331) plane. Here, the diffraction angle during measurement specifies the diffraction angle corresponding to the crystal plane of the measurement object. The above-mentioned measurement field of view refers to the "measurement field of view of the surface of the titanium compound layer". Next, based on the measured crystal plane spacing of the (331) plane, the residual stress of the entire measurement field of view is calculated. Such measurements are performed in multiple measurement fields, and the average value of the residual stresses obtained in each measurement field of view is used as the "residual stress of the titanium compound layer".

[0122] In this embodiment, based on 2θ-sin 2 The residual stress measurement by the ψ method was performed under the following conditions.

[0123] Equipment: SmartLab (manufactured by Rigaku Co., Ltd.)

[0124] X-ray: Cu / Kα / 45kV / 200mA

[0125] Counter: D / teX Ultra250 (manufactured by Rigaku Co., Ltd.)

[0126] Diffraction surface: (331)

[0127] Scanning range: 72°~74°(tilt method)

[0128] (Second Aluminum Oxide Layer)

[0129] The second aluminum oxide layer 22 in this embodiment is arranged directly above the titanium compound layer 21. The second aluminum oxide layer may also be provided with other layers such as a surface layer thereon. In addition, the second aluminum oxide layer may also be the outermost surface of the coating. The second aluminum oxide layer may be composed only of aluminum oxide (Al2O3), or may be composed of aluminum oxide and inevitable impurities. As the inevitable impurities, for example, chlorine, sulfur, etc. may be listed. The aluminum oxide is preferably α-type aluminum oxide (α-Al2O3). The composition of the second aluminum oxide layer may be the same as or different from that of the first aluminum oxide layer. The thickness of the second aluminum oxide layer is preferably greater than 0.2 μm and less than 6.5 μm, more preferably greater than 0.5 μm and less than 5 μm, and further preferably greater than 1 μm and less than 4.5 μm. The thickness of the second aluminum oxide layer is thinner than before. However, since the second aluminum oxide layer is thinner, a predetermined residual stress can be imparted to the titanium compound layer by performing sandblasting after forming the second aluminum oxide layer as described later. The thickness of the second aluminum oxide layer can be confirmed by observing the vertical cross section of the substrate and the coating using an SEM in the same manner as described above.

[0130] In one aspect of the present embodiment, preferably, the thickness of the second aluminum oxide layer is greater than or equal to 0.2 μm and less than or equal to 6.5 μm, and the residual stress of the titanium compound layer is greater than or equal to −3 GPa and less than or equal to 0 GPa.

[0131] In one aspect of the present embodiment, the portion of the second aluminum oxide layer adjacent to the titanium compound layer may form an interface region, and nitrogen may be contained in the interface region. Here, in the second aluminum oxide layer, the portion other than the interface region forms a non-interface region. The interface region of the second aluminum oxide layer is preferably a region sandwiched between the interface between the second aluminum oxide layer and the titanium compound layer and an imaginary plane parallel to the interface passing through a location 0.5 μm away from the interface in the thickness direction. The nitrogen content in the interface region of the second aluminum oxide layer is preferably greater than 0.5 at% and less than 10 at%. Thus, a cutting tool having excellent adhesion between the second aluminum oxide layer and the titanium compound layer can be provided. In one aspect of the present embodiment, the nitrogen content in the non-interface region of the second aluminum oxide layer is preferably greater than 0 at% and less than 0.15 at%. The nitrogen content in the interface region or the non-interface region of the second aluminum oxide layer can be obtained by line analysis of a cross-sectional sample by the AES method according to the above method.

[0132] (basal layer)

[0133] The coating 40 preferably further includes a base layer 23 disposed between the substrate 10 and the first aluminum oxide layer 20 (see Figure 3The base layer 23 preferably includes titanium nitride (TiN), titanium carbonitride (TiCN) or titanium oxycarbonitride (TiCNO). The TiN, TiCN and TiCNO are preferably cubic crystals.

[0134] The thickness of the base layer is preferably 3 μm to 20 μm, more preferably 5 μm to 15 μm. Such thickness can be confirmed by observing the vertical cross section of the substrate and the coating using SEM in the same manner as described above.

[0135] (Surface layer)

[0136] The coating preferably further includes a surface layer provided on the second aluminum oxide layer. The surface layer preferably includes a compound composed of titanium and at least one element selected from the group consisting of C, N, and B.

[0137] Examples of the compound contained in the surface include TiC, TiN, TiCN, and TiB 2 .

[0138] The thickness of the surface layer is preferably 0.2 μm to 3 μm, more preferably 0.5 μm to 1.5 μm. Such thickness can be confirmed by observing the vertical cross section of the substrate and the coating using SEM in the same manner as described above.

[0139] (Other layers)

[0140] The coating may further include other layers within the scope of not impairing the effect of the cutting tool involved in the present embodiment. The composition of the other layers may be different from or the same as that of the first aluminum oxide layer, the titanium compound layer, the second aluminum oxide layer, the base layer or the surface layer. Examples of compounds contained in the other layers include TiN, TiCN, TiBN and Al2O3. In addition, the stacking order of the other layers is not particularly limited. The thickness of the other layers is not particularly limited within the scope of not impairing the effect of the present embodiment, and may be, for example, greater than 0.1 μm and less than 20 μm.

[0141] 《Manufacturing method of cutting tool》

[0142] The method for manufacturing a cutting tool according to the present embodiment includes:

[0143] a first step in which the substrate is prepared (hereinafter sometimes referred to as the "first step");

[0144] a second step, in which the first aluminum oxide layer is formed on the substrate by chemical vapor deposition (hereinafter, sometimes referred to as the “second step”);

[0145] a third step of forming the titanium compound layer directly on the first aluminum oxide layer by chemical vapor deposition (hereinafter, sometimes referred to as the “third step”); and

[0146] a fourth step, in which the second aluminum oxide layer is formed directly on the titanium compound layer by chemical vapor deposition (hereinafter sometimes referred to as the "fourth step"),

[0147] In the final stage of the second step, a first aluminum oxide layer is formed using a raw material gas containing a gas including aluminum as a constituent element, a gas including nitrogen as a constituent element, and a gas including oxygen as a constituent element.

[0148] In the third step, a multi-layer structure layer is formed directly on the first aluminum oxide layer.

[0149] <First step: step of preparing a substrate>

[0150] In the first step, a substrate is prepared. For example, a cemented carbide substrate is prepared as the substrate. The cemented carbide substrate can be a commercial product or can be manufactured by a general powder metallurgy method. In the case of manufacturing by a general powder metallurgy method, for example, WC powder and Co powder are mixed by a ball mill or the like to obtain a mixed powder. After the mixed powder is dried, it is formed into a predetermined shape to obtain a formed body. Further, by sintering the formed body, a WC-Co based cemented carbide (sintered body) is obtained. Then, by subjecting the sintered body to predetermined tool tip processing such as honing, a substrate composed of a WC-Co based cemented carbide can be manufactured. In the first step, even a substrate other than the above-mentioned substrates can be prepared as long as it is a substrate that is previously known as such a substrate.

[0151] <Second step: step of forming a first aluminum oxide layer on a substrate>

[0152] In the second step, a first aluminum oxide layer is formed on the substrate by chemical vapor deposition (CVD). In addition, in the final stage of the second step, the first aluminum oxide layer is formed using a raw material gas containing a gas including aluminum as a constituent element, a gas including nitrogen as a constituent element, and a gas including oxygen as a constituent element.

[0153] Figure 5 FIG. 1 is a schematic cross-sectional view showing an example of a chemical vapor deposition device (CVD device) used in the manufacture of a coating. Figure 5The second step is described. The CVD device 30 is provided with a plurality of substrate setting fixtures 31 for holding the substrate 10 and a reaction vessel 32 made of heat-resistant alloy steel covering the substrate setting fixtures 31. In addition, a temperature regulating device 33 for controlling the temperature in the reaction vessel 32 is provided around the reaction vessel 32. A gas introduction pipe 35 having a gas introduction port 34 is provided in the reaction vessel 32. The gas introduction pipe 35 is arranged to extend in the vertical direction in the internal space of the reaction vessel 32 provided with the substrate setting fixture 31 and can rotate with the vertical direction as the axis. In addition, the gas introduction pipe 35 is provided with a plurality of ejection holes 36 for ejecting gas into the reaction vessel 32. Using this CVD device 30, the first aluminum oxide layer constituting the above-mentioned coating can be formed in the following manner.

[0154] First, the substrate 10 is placed on the substrate setting jig 31, and the raw material gas for the first aluminum oxide layer is introduced into the reaction container 32 from the gas introduction pipe 35 while the temperature and pressure in the reaction container 32 are controlled within a predetermined range. Thus, the first aluminum oxide layer 20 is formed on the substrate 10. Here, it is preferred that the raw material gas for the base layer is introduced into the reaction container 32 from the gas introduction pipe 35 before the first aluminum oxide layer 20 is formed (that is, before the second step), thereby forming a base layer (for example, a layer containing TiN) on the surface of the substrate 10. Hereinafter, a method for forming the first aluminum oxide layer 20 after forming the base layer on the surface of the substrate 10 is described.

[0155] The raw material gas for the above-mentioned base layer is not particularly limited. For example, when forming a TiN layer, a mixed gas of TiCl4 and N2 can be cited. When forming a TiCN layer, the raw material gas, for example, a mixed gas of TiCl4, N2, CH3CN, CH4, and C2H4 can be cited. When forming a TiCNO layer, the raw material gas, for example, a mixed gas of TiCl4, N2, CO, and CH4 can be cited.

[0156] The temperature in the reaction container 32 when forming the above-mentioned base layer is preferably controlled at 1000-1100° C. The pressure in the reaction container 32 when forming the above-mentioned base layer is preferably controlled at 0.1-1013 hPa. In addition, H2 is preferably used as a carrier gas. In addition, when the gas is introduced, it is preferred that the gas introduction pipe 35 is rotated by a driving unit not shown. Thereby, each gas can be uniformly dispersed in the reaction container 32.

[0157] Furthermore, the above-mentioned base layer can also be formed by the MT (Medium Temperature)-CVD method (medium temperature chemical vapor deposition method). The MT-CVD method is different from the CVD method (hereinafter also referred to as the "HT-CVD method") implemented at a temperature of 1000 to 1100°C. It is a method of forming a layer by maintaining the temperature in the reaction container 32 at a relatively low temperature of 850 to 950°C. Compared with the HT-CVD method, the MT-CVD method is implemented at a relatively low temperature, so it can reduce the damage to the substrate 10 caused by heating. In particular, when the above-mentioned base layer is a TiN layer, it is preferably formed by the MT-CVD method.

[0158] Next, the first aluminum oxide layer is formed on the base layer. As the raw material gas in the nucleus generation stage, for example, a mixed gas of AlCl3, CO, CO2, and HCl is used. As the raw material gas in the crystal growth stage, for example, a mixed gas of AlCl3, CO, CO2, HCl, and H2S is used. As the raw material gas used in the final stage of the second process, for example, a mixed gas of AlCl3 (a gas containing aluminum as a constituent element), CO, CO2, HCl, and N2 (a gas containing nitrogen as a constituent element) is used.

[0159] The content of AlCl3 in the raw material gas is preferably 1 to 5% by volume, more preferably 1.5 to 4% by volume, and still more preferably 2 to 3.5% by volume. The preferred flow rate of AlCl3 is 0.5 to 3.5 L / min.

[0160] The content of CO in the raw material gas is preferably 0.5 to 4% by volume, more preferably 0.8 to 3.5% by volume, and even more preferably 1 to 2.5% by volume. The preferred flow rate of CO is 0.5 to 2 L / min.

[0161] The content of CO 2 in the raw material gas is preferably 0.2 to 2.5% by volume, more preferably 0.3 to 2% by volume, and still more preferably 0.5 to 1.5% by volume. The preferred flow rate of CO 2 is 0.4 to 1.5 L / min.

[0162] The content of HCl in the raw material gas is preferably 1 to 6% by volume, more preferably 1.5 to 5.5% by volume, and even more preferably 2 to 4.5% by volume. The preferred flow rate of HCl is 0.5 to 4.5 L / min.

[0163] The content of H2S in the raw material gas is preferably 0.5 to 3.5% by volume, more preferably 1.0 to 3.0% by volume, and still more preferably 1.5 to 2.5% by volume. The preferred flow rate of H2S is 0.3 to 2.5 L / min.

[0164] The content of N2 in the raw material gas is preferably 0.1 to 1% by volume, more preferably 0.2 to 0.8% by volume, and still more preferably 0.3 to 0.6% by volume. The preferred flow rate of N2 is 0.1 to 0.5 L / min.

[0165] The temperature in the reaction container 32 is preferably controlled at 950 to 1000° C. The pressure in the reaction container 32 is preferably controlled at 50 to 100 hPa. In addition, H 2 can be used as a carrier gas. In addition, when the gas is introduced, it is preferable to rotate the gas introduction pipe 35, which is the same as described above.

[0166] Regarding the above-mentioned manufacturing method, the pattern of each layer is changed by controlling each condition of the CVD method. For example, the composition of each layer is determined by the composition of the raw material gas introduced into the reaction container 32. The thickness of each layer is controlled by the implementation time (film formation time).

[0167] <Third step: step of forming a titanium compound layer directly on the first aluminum oxide layer>

[0168] In the third step, the titanium compound layer is formed directly on the first aluminum oxide layer by chemical vapor deposition. In the third step, a multilayer structural layer is formed directly on the first aluminum oxide layer. The multilayer structural layer is formed by alternately stacking the first unit layer and the second unit layer.

[0169] As the raw material gas of the first unit layer, for example, a mixed gas of TiCl 4 , CH 4 , and N 2 is used.

[0170] The content of TiCl4 in the raw material gas is preferably 2 to 7% by volume, more preferably 3 to 6% by volume, and still more preferably 4 to 5% by volume. The preferred flow rate of TiCl4 is 1.5 to 5.0 L / min.

[0171] The content of CH 4 in the raw material gas is preferably 2 to 7% by volume, more preferably 2.5 to 6.5% by volume, and still more preferably 3 to 6% by volume. The preferred flow rate of CH 4 is 1.5 to 5.0 L / min.

[0172] The content of N2 in the raw material gas is preferably 5 to 40% by volume, more preferably 7 to 35% by volume, and further preferably 10 to 25% by volume. The preferred flow rate of N2 is 4 to 28 L / min.

[0173] The temperature in the reaction container 32 is preferably controlled at 950 to 1005° C. The pressure in the reaction container 32 is preferably controlled at 50 to 200 hPa. In addition, H 2 can be used as a carrier gas. In addition, when the gas is introduced, it is preferable to rotate the gas introduction pipe 35, which is the same as described above.

[0174] As the raw material gas of the second unit layer, for example, a mixed gas of TiCl 4 , CH 4 , N 2 , and CO is used.

[0175] The content of TiCl4 in the raw material gas is preferably 1.5 to 4.5% by volume, more preferably 2.0 to 4.0% by volume, and still more preferably 2.5 to 3.5% by volume. The preferred flow rate of TiCl4 is 0.8 to 2.3 L / min.

[0176] The content of CH4 in the raw material gas is preferably 0.5 to 3.5% by volume, more preferably 1.0 to 3.0% by volume, and still more preferably 1.5 to 2.5% by volume. The preferred flow rate of CH4 is 0.3 to 1.8 L / min.

[0177] The content of N2 in the raw material gas is preferably 15 to 45% by volume, more preferably 20 to 40% by volume, and further preferably 25 to 35% by volume. The preferred flow rate of N2 is 7.5 to 22.5 L / min.

[0178] The content of CO in the raw material gas is preferably 1.5 to 4.5% by volume, more preferably 2.0 to 4.0% by volume, and even more preferably 2.5 to 3.5% by volume. The preferred flow rate of CO is 0.8 to 2.3 L / min.

[0179] The temperature in the reaction container 32 is preferably controlled at 950 to 1005° C. The pressure in the reaction container 32 is preferably controlled at 100 to 300 hPa. In addition, H 2 can be used as a carrier gas. In addition, when the gas is introduced, it is preferable to rotate the gas introduction pipe 35, which is the same as described above.

[0180] In one aspect of the present embodiment, in the third step, in addition to the multilayer structure layer described above, a layer of titanium nitride, titanium carbide, titanium oxycarbonitride, or the like may be formed as a layer constituting the titanium compound layer.

[0181] <Fourth step: step of forming a second aluminum oxide layer directly on the titanium compound layer>

[0182] In the fourth step, a second aluminum oxide layer is formed directly on the titanium compound layer by chemical vapor deposition.

[0183] As the raw material gas, for example, a mixed gas of AlCl 3 , CO, CO 2 , H 2 S, HCl, and TiCl 4 is used.

[0184] The content of AlCl3 in the raw material gas is preferably 1 to 5% by volume, more preferably 1.5 to 4% by volume, and still more preferably 2 to 3.5% by volume. The preferred flow rate of AlCl3 is 0.5 to 3.5 L / min.

[0185] The content of CO in the raw material gas is preferably 0.5 to 4% by volume, more preferably 0.8 to 3.5% by volume, and even more preferably 1 to 2.5% by volume. The preferred flow rate of CO is 0.3 to 3 L / min.

[0186] The content of CO 2 in the raw material gas is preferably 0.2 to 2.5% by volume, more preferably 0.3 to 2% by volume, and still more preferably 0.5 to 1.5% by volume. The preferred flow rate of CO 2 is 0.1 to 1.5 L / min.

[0187] The content of H2S in the raw material gas is preferably 0.2 to 2.5% by volume, more preferably 0.3 to 2.0% by volume, and still more preferably 0.5 to 1.5% by volume. The preferred flow rate of H2S is 0.1 to 1.5 L / min.

[0188] The content of HCl in the raw material gas is preferably 1 to 7% by volume, more preferably 1.5 to 6.5% by volume, and still more preferably 2 to 6% by volume. The preferred flow rate of HCl is 0.5 to 4.5 L / min, and more preferably 1 to 4 L / min.

[0189] The content ratio of TiCl4 in the raw material gas is preferably 0.01 to 0.09 volume%, more preferably 0.02 to 0.08 volume%, and further preferably 0.03 to 0.07 volume%. The preferred flow rate of TiCl4 is 0.05 to 0.6 L / min. By including TiCl4 in the raw material gas, the adhesion between the titanium compound layer and the second aluminum oxide layer can be improved.

[0190] The temperature in the reaction container 32 is preferably controlled at 950 to 1000° C. The pressure in the reaction container 32 is preferably controlled at 50 to 200 hPa. In addition, H 2 can be used as a carrier gas. In addition, when the gas is introduced, it is preferable to rotate the gas introduction pipe 35, which is the same as described above.

[0191] In one aspect of the present embodiment, in the initial stage of the fourth step, a raw material gas containing a gas including aluminum as a constituent element, a gas including nitrogen as a constituent element, and a gas including oxygen as a constituent element can be used to form the second aluminum oxide layer. Thus, a cutting tool having excellent adhesion between the second aluminum oxide layer and the titanium compound layer can be provided. As the raw material gas, for example, a mixed gas of AlCl3, CO, CO2, H2S, HCl, TiCl4, and N2 is used. The content ratio of each of AlCl3, CO, CO2, H2S, HCl, and TiCl4 in the raw material gas is preferably within the above range.

[0192] The content of N2 in the raw material gas is preferably 0.1 to 1 volume percent, more preferably 0.2 to 0.8 volume percent, and still more preferably 0.3 to 0.6 volume percent. The preferred flow rate of N2 is 0.1 to 0.5 L / min, and more preferably 0.2 to 0.4 L / min.

[0193] <Other Processes>

[0194] In the manufacturing method involved in the present embodiment, in addition to the above-mentioned steps, additional steps can also be appropriately performed within the range that does not impair the effect of the present embodiment. As the above-mentioned additional steps, for example, a step of forming a surface layer on the above-mentioned second aluminum oxide layer, and a step of sandblasting the coating, etc. can be listed. In the present embodiment, the thickness of the second aluminum oxide layer located directly above the titanium compound layer is thinner than the thickness of the first aluminum oxide layer. Therefore, if sandblasting is performed after the above-mentioned fourth step, a predetermined compressive residual stress can be given to the above-mentioned titanium compound layer. The conditions for sandblasting can be listed, for example, as the conditions described in the embodiments described later. As a method for forming the surface layer, there is no particular limitation, and for example, a method of forming by a CVD method or the like can be listed.

[0195] Example

[0196] Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

[0197] 《Manufacturing of cutting tools》

[0198] <First step: step of preparing a substrate>

[0199] As a substrate, a cutting insert (shape: CNMG120408N-UX, manufactured by Sumitomo Electric Hardmetal Co., Ltd., JIS B4120 (2013)) made of cemented carbide having a composition consisting of TaC (2.0 mass%), NbC (1.0 mass%), Co (10.0 mass%) and WC (balance) (including inevitable impurities) was prepared.

[0200] <Step of Forming Base Layer>

[0201] Before the second step described later, a base layer is formed on the prepared substrate using a CVD device with the raw gas composition and film forming conditions described in Table 1. In addition, the film forming time is appropriately adjusted in such a manner as to form the thickness shown in Table 5. In addition, the thickness of the base layer and the composition of the base layer are shown in Table 5. In Table 5, the composition of the base layer is described in order from near to far from the substrate. For example, the expression "TiN (1.0) / TiCN (10.5) / TiCNO (1.5)" means that a layer of TiN (thickness of 1.0 μm), a layer of TiCN (thickness of 10.5 μm) and a layer of TiCNO (thickness of 1.5 μm) are formed in sequence from the layer closer to the substrate.

[0202] Table 1

[0203]

[0204] <Second step: step of forming a first aluminum oxide layer on a substrate>

[0205] For the prepared substrate or the substrate with a base layer formed thereon, a first aluminum oxide layer is formed using a CVD device, and then the process proceeds to the third step of the subsequent process. The formation conditions of the first aluminum oxide layer are shown in Table 2. As shown in Table 2, according to each stage of "nucleation" (initial stage), "crystal growth" (intermediate stage), and "formation of an N-containing layer" (final stage), the composition of the raw material gas is changed to form the first aluminum oxide layer. For samples 101 and 103, the raw material gas in "formation of an N-containing layer" (final stage) is not used, and the first aluminum oxide layer is formed through two stages of "nucleation" (initial stage) and "crystal growth" (intermediate stage). In addition, the film formation time is appropriately adjusted in such a way as to form the thickness shown in Table 5. In addition, the thickness of the first aluminum oxide layer and the composition of the first aluminum oxide layer are shown in Table 5.

[0206] Table 2

[0207]

[0208] <Third step: step of forming a titanium compound layer directly on the first aluminum oxide layer>

[0209] Next, a titanium compound layer is formed directly above the first aluminum oxide layer using a CVD device for the substrate on which the first aluminum oxide layer is formed. Here, in the third step, a multilayer structure layer is formed directly above the first aluminum oxide layer. The multilayer structure layer is formed by alternately stacking a first unit layer (a layer of titanium carbonitride) and a second unit layer (a layer of titanium oxide carbonitride). The formation conditions of the titanium compound layer are shown in Table 3. In addition, the film forming time is appropriately adjusted in such a manner as to form a thickness as shown in Table 5. In addition, the thickness of the titanium compound layer and the composition of the titanium compound layer are shown in Table 5. In Table 5, the composition of the titanium compound layer is recorded in order from near to far from the first aluminum oxide layer. For example, the expression "ML (8.0) / TiN (3.0)" means that a multilayer structure layer (with a thickness of 8.0 μm) and a TiN layer (with a thickness of 3.0 μm) are formed in sequence from the layer closer to the first aluminum oxide layer.

[0210] Table 3

[0211]

[0212] <Fourth step: step of forming a second aluminum oxide layer directly on the titanium compound layer>

[0213] Next, a second aluminum oxide layer was formed directly on the titanium compound layer using a CVD device on the substrate having the titanium compound layer formed thereon. The conditions for forming the second aluminum oxide layer are shown in Table 4. In addition, the film forming time was appropriately adjusted so as to form the thickness shown in Table 5. In addition, the thickness of the second aluminum oxide layer and the composition of the second aluminum oxide layer are shown in Table 5.

[0214] Table 4

[0215]

[0216] <Step of Forming Surface Layer>

[0217] Finally, a surface layer was formed on the substrate having the second aluminum oxide layer using a CVD device. The conditions for forming the surface layer are as follows. In addition, the thickness and composition of the surface layer are shown in Table 5. In addition, the places indicated by "-" in Table 5 mean that the corresponding layer is not provided.

[0218] (In the case of TiN)

[0219] Raw material gas composition: TiCl4 (7.0 vol%), N2 (40.0 vol%), H2 (balance)

[0220] Total gas flow: 60L / min

[0221] Pressure: 250hPa

[0222] Temperature: 1000℃

[0223] (In the case of TiC)

[0224] Raw material gas composition: TiCl4 (4.0 vol%), CH4 (4.0 vol%), H2 (balance)

[0225] Total gas flow: 50L / min

[0226] Pressure: 80hPa

[0227] Temperature: 1000℃

[0228] <Sandblasting process>

[0229] Finally, the coating was subjected to a sandblasting treatment under the following conditions while the cutting tool was rotated at 90 rpm with the through hole at the center of the rake face as the axis center.

[0230] Sand blasting conditions

[0231] Medium: A water solvent containing 7% by volume of ceramic particles with a particle size of 100 μm as abrasive particles

[0232] Spray angle: 45° relative to the rotation axis

[0233] Spray distance: 10mm from the edge of the blade

[0234] Injection pressure: 0.05~0.10MPa

[0235] Spray time: 5 to 20 seconds

[0236] The injection pressure and injection time were adjusted so as to obtain the residual stress shown in Table 6.

[0237]

[0238] Through the above-described steps, cutting tools of samples 1 to 13 and samples 101 to 103 were produced.

[0239] 《Evaluation of cutting tool characteristics》

[0240] Using the cutting tools of the samples prepared as described above, various characteristics of the cutting tools were evaluated as follows: Here, samples 1 to 13 correspond to Examples, and samples 101 to 103 correspond to Comparative Examples.

[0241] <Measurement of Thickness of Each Layer Constituting the Film>

[0242] The thickness of each layer constituting the coating is measured by using a field emission scanning electron microscope (SEM) (manufactured by Hitachi High-Technologies Co., Ltd., trade name: SU3500) to measure any ten points in the cross-sectional sample parallel to the normal direction of the surface of the substrate, and taking the average value of the thickness of the ten measured points. At this time, the measured cross section of the above cross-sectional sample is ground by ion milling (manufactured by Hitachi High-Technologies Co., Ltd., trade name: IM4000) and then measured. The results are shown in Tables 5 and 6. In addition, the SEM image determines whether the bottom layer in the multilayer structure layer is the first unit layer or the second unit layer.

[0243] <Nitrogen Content Ratio in the Interface Region and Non-Interface Region of the First Aluminum Oxide Layer (AES Measurement)>

[0244] The atomic ratio of each element (oxygen, nitrogen, aluminum) in the interface region and non-interface region of the first aluminum oxide layer is obtained by line analysis of a cross-sectional sample parallel to the normal direction of the surface of the above-mentioned substrate using Auger electron spectroscopy (AES method). Specifically, first, the cut surface of the above-mentioned cross-sectional sample is ground by cross-sectional polishing. For the cut surface after grinding, a cross-sectional SEM image of the base layer, the first aluminum oxide layer and the titanium compound layer is obtained by analysis using a field emission scanning microscope (FE-SEM). The measurement magnification at this time is 50,000 times. At this time, the base layer and the titanium compound layer are observed as darker areas, and the first aluminum oxide layer is observed as a brighter area. Then, in the field of view of the above-mentioned cross-sectional SEM image, in a direction parallel to the stacking direction of the above-mentioned titanium compound layer, from the titanium compound layer side toward the first aluminum oxide layer side, the cut surface after grinding is analyzed by the AES method. The measurement spacing at this time is 0.016μm. Other measurement conditions of the AES method are the following conditions.

[0245] (Measurement conditions of the AES method)

[0246] Measuring device: manufactured by ULVAC-PHI, trade name: PHI700

[0247] Measurement acceleration voltage: 10kV

[0248] Measuring current: 10mA

[0249] Sample tilt angle: 30°

[0250] Sputtering voltage: 1kV

[0251] A graph is prepared from the data obtained by the above line analysis. In the above graph, the X-axis (horizontal axis) represents the distance from the measurement start point, and the Y-axis (vertical axis) represents the atomic ratio (at%) of each element of the measurement object. Next, based on the graph, the location where the atomic ratio of aluminum is 10 at% and the location closer to the above titanium compound layer is defined as the "interface S between the first aluminum oxide layer and the titanium compound layer" (for example, refer to Figure 4 ). In addition, a plane including a point 0.5 μm away from the interface S toward the first aluminum oxide layer is defined as a “virtual plane A” (for example, refer to Figure 4 In the above diagram, the location where the atomic ratio of aluminum is 10 at% and closer to the above substrate is defined as "interface Q on the substrate side of the first aluminum oxide layer" (refer to Figure 4 ). Then, based on the above graph, the average value of the atomic ratio of the nitrogen in the region (interface region) sandwiched between the interface S and the imaginary plane A, and the average value of the atomic ratio of the nitrogen in the region (non-interface region) sandwiched between the imaginary plane A and the interface Q were respectively calculated. This measurement was performed three times, and the average values ​​of the values ​​calculated in each measurement were respectively used as the nitrogen content ratio in the interface region of the first aluminum oxide layer, and the nitrogen content ratio in the non-interface region of the first aluminum oxide layer. The results are shown in Table 6.

[0252] <Residual Stress in Titanium Compound Layer>

[0253] Through the above 2θ-sin 2 The residual stress in the titanium compound layer was measured by the ψ method under the following conditions. The results are shown in Table 6. In Table 6, the residual stress represented by a negative value refers to the compressive residual stress, and the residual stress represented by a positive value refers to the tensile residual stress.

[0254] Equipment: SmartLab (manufactured by Rigaku Co., Ltd.)

[0255] X-ray: Cu / Kα / 45kV / 200mA

[0256] Diffraction surface: (331)

[0257] Counter: D / teX Ultra250 (manufactured by Rigaku Co., Ltd.)

[0258] Scanning range: 72°~74°(tilt method)

[0259]

[0260] 《Cutting Test》

[0261] (Cutting evaluation 1: continuous machining test, evaluation of wear resistance)

[0262] Using the cutting tools of the samples (samples 1 to 13 and samples 101 to 103) prepared as described above, the cutting time (minutes) until the wear amount of the flank surface reaches 0.3 mm was measured under the following cutting conditions. The results are shown in Table 6. The longer the cutting time, the better the wear resistance of the cutting tool.

[0263] Cutting conditions for continuous machining

[0264] Cutting material: SCM415 (shape: round bar)

[0265] Cutting speed: 350m / min

[0266] Feed speed: 0.23mm / rev

[0267] Incision: 1.5mm

[0268] Cutting oil: Yes

[0269] (Cutting evaluation 2: Evaluation of surface quality)

[0270] In the above cutting test, the machined surface of the workpiece was visually observed 1 minute after the start of the cutting process. Figure 6 The surfaces were graded into A to E based on the criteria shown. The results are shown in Table 6. Grades A to C were evaluated as good processed surfaces. By performing the cutting evaluation 2, the welding resistance of the cutting tool can be evaluated.

[0271] (Cutting evaluation 3: intermittent machining test, evaluation of defect resistance)

[0272] Using the cutting tools of the samples (samples 1 to 13 and samples 101 to 103) prepared as described above, the cutting time (minutes) from the start of chipping until the cutting edge ridgeline is chipped was measured under the following cutting conditions. The results are shown in Table 6. The longer the cutting time, the better the chipping resistance of the cutting tool.

[0273] Cutting conditions for intermittent machining

[0274] Cutting material: SCM435 intermittent material (shape: round bar with slit groove)

[0275] Cutting speed: 220m / min

[0276] Feed speed: 0.25mm / rev

[0277] Cutting: 2.0mm

[0278] Cutting oil: Yes

[0279] According to the results in Table 6, the cutting tools of samples 1 to 13 (cutting tools of the examples) obtained good results of cutting time of 13.5 minutes or more in cutting evaluation 1. On the other hand, the cutting time of cutting tools of samples 101 to 103 (cutting tools of the comparative examples) in cutting evaluation 1 was less than 5 minutes. From the above results, it can be seen that the cutting tools of the examples are superior in wear resistance compared with the cutting tools of the comparative examples.

[0280] In addition, according to the results of Table 6, the surface quality of the cutting tools of samples 1 to 13 (cutting tools of the embodiments) in the cutting evaluation 2 was grade A to C, and good results were obtained. On the other hand, the surface quality of the cutting tools of samples 102 and 103 (cutting tools of the comparative examples) in the cutting evaluation 2 was grade E. The surface quality of the cutting tool of sample 101 (cutting tool of the comparative example) in the cutting evaluation 2 was grade C, but the cutting time in the above-mentioned cutting evaluation 1 was 4.5 minutes, and it was not possible to achieve both wear resistance and welding resistance.

[0281] According to the results in Table 6, the cutting tools of samples 1 to 13 (cutting tools of the examples) obtained good results of cutting time of 10.5 minutes or more in cutting evaluation 3. On the other hand, the cutting time of cutting tools of samples 101 to 103 (cutting tools of the comparative examples) in cutting evaluation 3 was 7.5 minutes or less. From the above results, it can be seen that the cutting tools of the examples are superior in chipping resistance compared with the cutting tools of the comparative examples.

[0282] From the above results, it is understood that the cutting tool of the example is superior in wear resistance and welding resistance as compared with the cutting tool of the comparative example.

[0283] As mentioned above, although embodiment and Example of this invention were demonstrated, it is planned from the beginning that the structure of each embodiment and Example mentioned above may be combined suitably.

[0284] The embodiments and examples disclosed herein are illustrative in all aspects and are not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and is intended to include all modifications within the scope and meaning equivalent to the claims.

[0285] Description of Reference Numerals

[0286] 1: front cutting edge; 2: back cutting edge; 3: cutting edge ridge; 10: substrate; 20: first aluminum oxide layer; 21: titanium compound layer; 22: second aluminum oxide layer; 23: base layer; 24: multilayer structure layer; 24a: first unit layer; 24b: second unit layer; 30: CVD device; 31: substrate setting fixture; 32: reaction container; 33: temperature control device; 34: gas inlet port; 35: gas inlet pipe; 36: ejection hole; 40: coating; 50: cutting tool; A: an imaginary plane A including a point 0.5 μm away from the interface S between the first aluminum oxide layer and the titanium compound layer to the first aluminum oxide layer side; Q: interface Q on the substrate side of the first aluminum oxide layer; S: interface S between the first aluminum oxide layer and the titanium compound layer.

Claims

1. A cutting tool comprising a substrate and a coating provided on the substrate, wherein: The coating comprises: a first aluminum oxide layer disposed on the substrate; a titanium compound layer disposed directly above the first aluminum oxide layer; as well as a second aluminum oxide layer disposed directly above the titanium compound layer, In the first aluminum oxide layer, a portion adjacent to the titanium compound layer forms an interface region, In the first aluminum oxide layer, a portion other than the interface region forms a non-interface region, The nitrogen content in the interface region is greater than or equal to 0.2 at % and less than or equal to 12 at %, The nitrogen content in the non-interface region is greater than or equal to 0 at % and less than or equal to 0.15 at %, The titanium compound layer includes a multi-layer structure layer adjacent to the first aluminum oxide layer, The multi-layer structure layer is composed of a first unit layer and a second unit layer, In the multilayer structure layer, the first unit layers and the second unit layers are alternately stacked, and the first unit layers are composed of titanium carbonitride. The second unit layer is composed of titanium oxycarbonitride, The nitrogen content ratio in the interface region and the nitrogen content ratio in the non-interface region are atomic ratios based on the total of aluminum, oxygen and nitrogen in the first aluminum oxide layer, and the interface region of the first aluminum oxide layer is a region sandwiched between an interface (S) between the first aluminum oxide layer and the titanium compound layer and an imaginary plane (A) parallel to the interface (S) and passing through a point 0.5 μm away from the interface (S) in the thickness direction.

2. The cutting tool according to claim 1, wherein: The thickness of the first aluminum oxide layer is greater than the thickness of the second aluminum oxide layer.

3. The cutting tool according to claim 1 or 2, wherein: The titanium compound layer has a thickness of 1 μm or more and 11 μm or less.

4. The cutting tool according to claim 1 or 2, wherein: The titanium compound layer has a thickness of 2.5 μm or more and 8.5 μm or less.

5. The cutting tool according to claim 1 or 2, wherein: The second aluminum oxide layer has a thickness of 0.2 μm or more and 6.5 μm or less.

6. The cutting tool according to claim 1 or 2, wherein: The first aluminum oxide layer has a thickness of 2.5 μm or more and 20.5 μm or less.

7. The cutting tool according to claim 1 or 2, wherein: A content ratio of nitrogen in the interface region of the first aluminum oxide layer is greater than or equal to 0.5 at % and less than or equal to 10 at %.

8. The cutting tool according to claim 1 or 2, wherein: The thickness of the second aluminum oxide layer is greater than or equal to 0.2 μm and less than or equal to 6.5 μm. The residual stress of the titanium compound layer is greater than or equal to -3 GPa and less than or equal to 0 GPa.

9. The cutting tool according to claim 1 or 2, wherein: The lowermost layer of the multi-layer structure is the second unit layer.

10. The cutting tool according to claim 1 or 2, wherein: The titanium compound layer further includes a layer of titanium nitride or titanium carbide.

11. The cutting tool according to claim 1 or 2, wherein: The coating has a thickness of 10 μm or more and 40 μm or less.

12. The cutting tool according to claim 1 or 2, wherein: The coating further includes a base layer disposed between the substrate and the first aluminum oxide layer.

13. The cutting tool according to claim 1 or 2, wherein: The coating further includes a surface layer provided on the second aluminum oxide layer.

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