Cutting tools

Abstract

The present invention relates to a cutting tool comprising a support and a cutting tip of cBN or PCD, the cutting tip of cBN or PCD being attached to the support via a brazed joint having a thickness of 5-150 μm, the support being a cemented carbide comprising 3-25 wt. % metal binder, optionally up to 25 wt. % carbides or carbonitrides of one or more elements of groups 4, 5 or 6 of the Periodic Table of the Elements, and the balance WC, the metal binder comprising at least 40 wt. % Ni, the brazed joint comprising, in order from the support, a first layer of TiC having an average thickness of 10-400 nm located adjacent the support, a second layer having an average thickness of 0.5-8 μm and comprising an average of at least 5 wt. % Ni metal, an average of 25-60 wt. % Cu metal, and an average of 15-45 wt. % Ti metal, and a third layer having an average thickness of 4-145 μm and comprising Ag metal and Cu metal.

Description

Technical Field

[0001] The present invention relates to a cutting tool including a support and a cutting edge tip of cBN or PCD.

Background Art

[0002] Since it was first introduced as a cutting tool material in the 1980s, the use of cubic boron nitride (cBN) has evolved and has become a common machining solution. Application areas include hardened steel, cast iron, heat-resistant superalloys (HRSA), and powder metals. These workpieces have in common that they are generally recognized as difficult to machine. Cutting tools made of cBN material can withstand high cutting temperatures and cutting forces and still retain their cutting edges. This is why cBN provides a long and consistent tool life and produces components with excellent surface finishes.

[0003] Polycrystalline diamond (PCD) is a composite material of diamond particles sintered with a metal binder. Diamond is the hardest among all materials and thus the most wear-resistant. As a cutting tool material, PCD has good wear resistance but lacks chemical stability at high temperatures and is prone to dissolve in iron. Therefore, PCD tools are limited to non-ferrous materials such as high silicon aluminum, metal matrix-based composites (MMC), and carbon fiber reinforced plastics (CFRP). PCD containing flood coolant can also be used for titanium superfinishing applications.

[0004] When used in a cutting tool, cBN or PCD usually constitutes only a part of the cutting tool, for example, a cutting insert, more specifically, a part involved in the cutting operation such as a tip portion. Therefore, the tips of cBN or PCD are usually attached to a cemented carbide support.

[0005] Brazing materials, in the form of paste, foil, or wire, are used to bond cBN or PCD tips to cemented carbide supports. Their purpose is to provide a strong bond between the support and the cBN or PCD tip.

[0006] The cemented carbide support consists of hard WC particles in a metallic binder. One type of binder is primarily composed of Ni. [Overview of the Initiative]

[0007] The object of the present invention is to provide a cutting tool having a cBN cutting edge or PCD cutting edge brazed to a cemented carbide support using a metal binder containing at least 40% by weight of Ni, wherein the cutting edge is brazed via a novel brazed joint that provides excellent bonding strength resulting in a long tool life.

[0008] In this specification, "cutting tool" means a cutting tool for metal cutting applications, such as an insert or end mill. The application areas of metal cutting are preferably turning or milling.

[0009] At least one of these objectives is achieved by the cutting tool described in claim 1. Preferred embodiments are enumerated in the dependent claims.

[0010] This invention The cutting tool according to the present invention comprises a support and a cutting edge tip made of cBN or PCD, the cBN or PCD cutting edge tip being attached to the support via a brazed joint 5 to 150 μm thick, the support being a cemented carbide containing 3 to 25 wt% of a metal binder, optionally up to 25 wt% of carbides or carbonitrides of one or more elements from groups 4, 5, or 6 of the periodic table, and the remainder being WC, the metal binder containing at least 40 wt% Ni, and the brazed joint comprising, in order from the support and positioned adjacent to the support, a first TiC layer with an average thickness of 10 to 400 nm, a second layer with an average thickness of 0.5 to 8 μm containing at least 5 wt% metallic Ni on average, 25 to 60 wt% metallic Cu on average, and 15 to 45 wt% metallic Ti on average, and a third layer with an average thickness of 4 to 145 μm containing metallic Ag and metallic Cu.

[0011] The thickness of a brazed joint or a layer within a joint is measured in this specification in a direction perpendicular to the interface between the support and the brazed joint.

[0012] The average thickness of the brazed joint or the layers within the brazed joint can be appropriately calculated by using one or more cross-sectional images of the brazed joint, obtaining at least 10 randomly selected measurement points over a distance of at least 30 μm, and calculating the average.

[0013] In this specification, "cBN cutting edge tip" means a cutting edge tip of a cBN composite material comprising cBN particles and a metal and / or ceramic bonding phase comprising, for example, one or more aluminum compounds. The cBN composite material may also include a ceramic bonding phase which may comprise, for example, nitrides, carbides, or carbonitrides of Group 4, Group 5, or Group 6 transition metals, or mixtures thereof. The transition metal may be, for example, titanium. By varying the components and their relative amounts, cBN composite materials can be designed to achieve optimal performance in different applications, such as continuous or intermittent cutting, and in machining different metals. Known methods for producing cBN composite materials for metal machining are based on conventional powder metallurgy techniques, which include mixing and grinding raw materials into a powder mixture, forming the powder mixture into a green molded body, and subjecting the green molded body to a high-pressure and high-temperature sintering operation (HPHT sintering) to form a sintered body of cBN composite material. The sintered body of cBN composite material may be formed on a support material, for example, a cemented carbide, or it may be formed without a support material. The sintered cBN composite material is machined into a tip intended for brazing onto a cemented carbide substrate.

[0014] In this specification, "PCD cutting edge tip" means a cutting edge tip made of a PCD composite material containing diamond particles sintered with a metal binder, usually Co. The diamond particle content is preferably at least 80 volume percent. The sintered body of the PCD composite material can be formed on a support material, for example, a cemented carbide, or it can be formed without a support material. The sintered body of the PCD composite material is cut into a tip intended for brazing to a cemented carbide substrate.

[0015] "Cemented carbide" as used herein means a sintered material containing at least 75 wt% hard components distributed in a continuous metallic bonding phase. A cemented carbide comprises at least 50 wt% WC and, optionally, other hard components common in the art of manufacturing cemented carbides, such as carbides and / or carbonitrides of Group 4, 5, and 6 elements of the periodic table, and a metallic binder. The metallic binder of a cemented carbide may include elements that dissolve into the metallic binder during sintering, such as W and C derived from WC.

[0016] In this specification, "metallic Ni," "metallic Cu," "metallic Ag," "metallic Ti," and "metallic In" refer to each of the metallic elements Ni, Cu, Ag, Ti, and In, which are bonded to the same or another metal, meaning that their valence electrons move freely within the metal lattice.

[0017] In this specification, a brazed joint means the area or mass between a cemented carbide portion and a cutting edge tip of cBN or PCD, which is filled with brazing material and formed during the brazing process.

[0018] The metal binder in the cemented carbide support preferably contains 50 to 90% by weight of Ni, more preferably 60 to 80% by weight of Ni.

[0019] In one embodiment, the metallic binder in the cemented carbide support contains 10 to 20% by weight of Fe.

[0020] In one embodiment, the metallic binder in the cemented carbide support contains up to 10% by weight of Co.

[0021] In one embodiment, the metallic binder in the cemented carbide support contains 0.1 to 5% by weight of Co.

[0022] In one embodiment, the metallic binder in the cemented carbide support contains less than 1% by weight of Co.

[0023] The metal binder of the cemented carbide further contains W derived from WC that dissolves in the metal binder during sintering. The content of W that dissolves in the metal binder varies depending on the carbon content in the cemented carbide, and the content of W in the metal binder is preferably less than 20% by weight.

[0024] In one embodiment, Cr and / or V are present dissolved in the metal binder.

[0025] Other elements such as Cu and Mn may be present in the metal binder together with Fe.

[0026] In one embodiment, the metal bond Agent The total content of Ni, Fe, Co, and W in the metal binder is 80 to 100% by weight, preferably 90 to 99% by weight.

[0027] The content of the metal binder in the cemented carbide of the support is preferably 4 to 20% by weight, preferably 5 to 15% by weight.

[0028] The thickness of the brazed joint is preferably 10 to 100 μm, preferably 10 to 50 μm.

[0029] During brazing, Ti from the brazing filler metal reacts with carbon from the cemented carbide support to form a TiC layer adjacent to the support. The average thickness of the first layer of TiC is preferably 50 to 300 nm, preferably 100 to 300 nm.

[0030] In one embodiment, the brazed joint includes a TiN layer adjacent to the cBN cutting tool tip. The average thickness of the TiN layer is preferably 10 to 400 nm, preferably 50 to 300 nm.

[0031] In one embodiment, the brazed joint includes a TiC layer adjacent to the PCD cutting tool tip. The average thickness of the TiC layer is preferably 10 to 400 nm, preferably 50 to 300 nm.

[0032] The second layer preferably contains at least 10% by weight of metallic Ni on average, preferably 10 to 40% by weight of metallic Ni on average, and most preferably 15 to 30% by weight of metallic Ni on average.

[0033] The second layer preferably contains an average of 35-55% by weight of metallic Cu.

[0034] The second layer preferably contains an average of 25-40% by weight of metallic Ti.

[0035] The second layer preferably contains a total of 70-100% by weight of metallic Ni, metallic Cu, and metallic Ti on average, more preferably 80-100% by weight on average, and most preferably 90-100% by weight on average.

[0036] The average thickness of the second layer is preferably 1 to 5 μm.

[0037] In one embodiment, the brazed joint further comprises a third layer of metal In (indium).

[0038] The third layer preferably contains a total of 60-100% by weight of metallic Cu and metallic Ag on average, more preferably 80-100% by weight on average, and most preferably 90-100% by weight on average.

[0039] The third layer, which contains metallic Ag and metallic Cu, preferably contains an average of 60-80% by weight of metallic Ag and an average of 15-40% by weight of metallic Cu.

[0040] In one embodiment, In is present in a phase contained in a third layer that contains 80-95% by weight of Ag.

[0041] In one embodiment, the third layer comprises two phases, one of which contains an average of 30-50% by weight of metallic Cu and an average of 50-70% by weight of metallic Ag, and the other phase contains an average of 5-20% by weight of metallic Cu and an average of 80-95% by weight of metallic Ag.

[0042] The average thickness of the third layer is preferably 8 to 100 μm, and more preferably 12 to 50 μm.

[0043] In one embodiment, there is a Ni-deficient region on the outermost part of the support adjacent to the brazed joint, and this Ni-deficient region preferably has an average thickness of 0.5 to 5 μm.

[0044] In one embodiment, the cBN cutting edge tip comprises a cemented carbide at the bottom and a cBN composite material at the top.

[0045] In one embodiment, the cBN cutting edge tip comprises a cBN composite material as a whole.

[0046] In one embodiment, the PCD cutting edge tip comprises a cemented carbide at the bottom and a PCD composite material at the top.

[0047] In one embodiment, the PCD cutting edge tip comprises a PCD composite material as a whole.

[0048] The cutting tool may be a turning insert, a milling insert, or an end mill.

[0049] The cutting tools of the present invention are preferably manufactured by providing a cemented carbide sintered body ("blank") in the form of a cutting insert or end mill, along with a cutting edge tip made of cBN or PCD. The cemented carbide blank has a recess into which the cutting edge tip made of cBN or PCD is intended to be bonded.

[0050] A paste-like brazing material containing Ag, Cu, and Ti is applied to one or both of the recesses of the cemented carbide blank and the cBN or PCD cutting edge tip, and then the cemented carbide blank and the cBN or PCD cutting edge tip are joined together so that the brazing material is positioned between the two parts. This forms the jointed cutting tool body. Indium (In) may be included in the brazing material, especially when brazing is performed at temperatures lower than 780°C, as it lowers the melting temperature of the brazing material.

[0051] Next, the jointed cutting tool body is heat-treated in an inert atmosphere such as argon or under vacuum. When brazing cBN cutting edge tips, the temperature is maintained at approximately 800°C, and when brazing PCD cutting edge tips, it is typically maintained at approximately 700°C.

[0052] The heat treatment duration is approximately 5 to 15 minutes. This process creates a cutting tool with a strong brazed joint between the cemented carbide blank and the cBN or PCD cutting edge tip.

[0053] The brazing process requires a specific temperature range to provide a specific brazed joint between the cemented carbide support and the cBN or PCD cutting edge tip of the present invention. During brazing, Ti from the brazing material reacts with carbon in the cemented carbide portion, forming a TiC layer at the interface between the brazed joint and the cemented carbide portion. If the temperature used is too low, the TiC layer adjacent to the cemented carbide body will not form, and the layer formed containing Ni will be very irregular. This results in a low strength joint between the cemented carbide body and the cBN or PCD cutting edge tip. On the other hand, if the temperature used in the brazing process is too high, the TiC layer becomes excessively thick, making it too brittle and reducing its function as a bonding layer. [Brief explanation of the drawing]

[0054] [Figure 1] This is an overall view of a cutting tool, which is a turning insert having a support portion and a cBN / PCD cutting edge tip. [Figure 2] This is a cross-sectional view of a cutting tool equipped with a brazed joint that connects a support body and a cBN cutting edge tip. [Figure 3] This is a magnified view of a portion of Figure 2. [Modes for carrying out the invention]

[0055] Figure 1 shows an overall view of a cutting tool (1), which is a turning insert having a support (2) and a cBN / PCD cutting edge tip (3).

[0056] Figure 2 shows a cross-sectional SEM image of one embodiment of the cutting tool of the present invention having a brazed joint (4) that joins a cemented carbide support (2) and a cBN cutting edge tip (3). The brazed joint (4) comprises a layer (5) containing Ni, Cu, and Ti, and a layer (6) containing Ag and Cu.

[0057] Figure 3 shows an SEM image of an enlarged cross-section of Figure 2, showing the cemented carbide support (2) and the lower part of the brazed joint where the bottommost TiC layer (7) adjacent to the cemented carbide support (2) is visible. Furthermore, the lower parts of the second layer (5) containing Ni, Cu, and Ti, and the third layer (6) containing Ag and Cu are visible. [Examples]

[0058] Herein, exemplary embodiments of the present invention are disclosed in more detail. In a metal cutting operation, cutting tools (inserts) were prepared, analyzed, and tested. [Example 1] Manufacturing of cutting tool samples

[0059] A cemented carbide cutting insert blank was manufactured from a powder mixture having a composition of 4.89 wt% Ni, 0.83 wt% Fe, and the remainder WC. The powder mixture was pulverized using a WC-Co cemented carbide powder, dried, pressed into the insert geometry DCGW11T308, and sintered at 1410°C.

[0060] The binder content in the cemented carbide was confirmed to be approximately 6.1% by weight. The sintered cemented carbide contains approximately 4.9% by weight Ni, 0.8% by weight Fe, and 0.4% by weight Co, which are metallic bonds. Agent It was part of a metallic bond. AgentThe material itself contained approximately 75 wt% Ni, 13 wt% Fe, 3 wt% Co, and 9 wt% W. The dissolved W originated from WC particles. The Co mainly originated from pulverized WC-Co cemented carbide that was worn down during the grinding of the raw material powder mixture. No free graphite or eta phase was observed in cross-sectional SEM images of the cemented carbide substrate.

[0061] A recess for the cBN tip was created in the tip portion of the cutting insert blank. This recess forms the support structure for the cBN cutting tip.

[0062] Two types of cBN cutting edges were prepared. The first type (cBN1) was manufactured from a powder mixture of cBN and TiN, pressed into a geometric S01020 cutting edge, and sintered. The sintered blank contained 47 vol% cBN equilibrated with TiN and a small amount of reaction products. The second type (cBN2) was manufactured from a powder mixture of cBN and TiCN, pressed into a geometric S01020 cutting edge, and sintered. The sintered blank contained 65 vol% cBN equilibrated with TiCN and a small amount of reaction products. The cBN1 and cBN2 cutting edges were commercially available.

[0063] Next, the cBN cutting edge tip was joined to the cutting insert blank by applying brazing paste to the surface of the recess of the cutting insert blank on the cemented carbide support. Two different brazing pastes were used. The first brazing paste (TB629, manufactured by Tokyo Blaze Co., Ltd.) was Ag 59 Cu 27 In 13 The composition is Ti1), and the second brazing paste (TB608 manufactured by Tokyo Blaze Co., Ltd.) is Ag 70 Cu 28 It had a Ti2 composition.

[0064] Brazing was performed in a furnace at three different temperatures: 740°C, 820°C, and 900°C. The brazing processes at 740°C and 820°C were carried out under vacuum in an Ipsen Corporation VFC-124 batch furnace, while the brazing process at 900°C was carried out in a Tokyo Blaze Corporation continuous belt furnace using argon as a protective gas. The first brazing paste was used for the 740°C and 900°C brazing processes, and the second brazing paste was used for the 820°C brazing process. There was also a slight difference in process time between the 740°C and 820°C processes and the 900°C process.

[0065] Therefore, three different brazing processes are defined. Table 1 TIFF0007846692000001.tif28170

[0066] The final cutting insert geometry was DCGW11T308S01020. After the brazing process was completed, the bonded assembly of the support and the cBN cutting tip was given a final grind.

[0067] Several assemblies of the support and the second type of cBN cutting edge tip were coated with a 2-4 μm thick TiN layer following a common PVD process used in the field of cutting tools. Because the deposition temperature of TiN is sufficiently low (approximately 450°C), the deposition of the TiN coating had no effect on the properties of the brazed joint.

[0068] Table 2 summarizes the composition of the samples and the brazing processes used to manufacture them. Table 2 TIFF0007846692000002.tif132170 [Example 2] Analysis of brazed joints

[0069] The brazed joint was analyzed using an electron probe microanalyzer (EPMA). Figures 2 and 3 show SEM images using a backscattered electron (BSE) detector. This detector separates elements by atomic weight, with lighter materials appearing darker and heavier materials appearing brighter. For example, Ag appears very bright relative to Cu.

[0070] The layered structure of the brazed joint was also analyzed by wavelength-dispersive spectroscopy (WDS) using EPMA. The EPMA instrument used was the JXA-8530 F Hyperprobe from JEOL. This provides different images for different elements, allowing visualization of the presence of specific elements (Ni, Ti, Cu, Ag, In, C, etc.) at specific locations within the brazed joint, and the intensity of the signal can indicate the level of their content.

[0071] Energy-dispersive X-ray spectroscopy (EDS) provided by the EPMA was used to analyze the content of specific elements (metallic Ni, Ti, Cu, Ag, and In) in the layers. The EPMA instrument used was a JEOL JXA-8530 F Hyperprobe. A large number of randomly selected measurement points were chosen to obtain reliable average values.

[0072] Analysis was performed on the brazed joints of samples 1, 2, and 3. Transparent layers 1, 2, and 3 were found. Table 3 shows the elemental content of each layer and the average thickness of each layer.

[0073] The thickness of the TiC layer is preferably measured by considering the concentration of C adjacent to the cemented carbide support, in combination with the presence of TiN. However, this is preferably done in combination with the SEM-BSE image obtained as described above, in which the TiC layer is clearly visible.

[0074] Analysis of sample 1, which was brazed at 740°C, revealed the following: Similar to Ti, carbon is not visible adjacent to the cemented carbide. However, a very thin layer containing elemental Ti is visible. A transparent thin layer is visible in the SEM-BSE image. Therefore, a very thin first layer of TiC exists. The second layer contains a considerable amount of Ni, Cu, and Ti. However, the layer is highly heterogeneous, contains several phases, and is not well-defined. No Ni-deficient region is observed at the top of the cemented carbide.

[0075] Analysis of sample 2, which was brazed at 820°C, revealed the following: Similar to Ti, the carbon adjacent to the cemented carbide is clearly visible. A transparent layer is seen in the SEM-BSE image. Therefore, the first layer of TiC is present. The second layer contains substantial amounts of Ni, Cu, and Ti and is well-defined. A Ni-deficient region of approximately 1 μm is observed at the top of the cemented carbide.

[0076] Analysis of sample 3, which was brazed at 900°C, revealed the following: Similar to Ti, the carbon adjacent to the cemented carbide is clearly visible. A transparent layer is seen in the SEM-BSE image. Therefore, the first layer of TiC is present. The second layer contains substantial amounts of Ni, Cu, and Ti and is well-defined. A Ni-deficient region of approximately 2 μm is observed at the top of the cemented carbide.

[0077] Table 3 shows further results from the analysis. Table 3 TIFF0007846692000003.tif162170 * It is difficult to measure several phases, layers with insufficient definition, average metallic element content, and layer thickness. ** Although metallic elements are present, they are located in several phases, making it difficult to measure their average content. [Example 3] Cutting test using the sample

[0078] Cutting tools were tested in metal cutting operations. The tested specimens were specimens 5 and 8, i.e., cBN cutting edge tips of different compositions and brazing paste 2, brazed under vacuum at a temperature of 820°C for 10 minutes. The test method involved intermittent cutting of hardened steel. To provide intermittent cutting, a ring of through-hardened steel SS2258 with grooves prepared in a soft stage was prepared. The test method involved turning operations by making cuts opposite to the grooved portion until the edge broke. The cutting parameters were gradually increased with each cut to apply incremental load. This test method allows for a good view of the cutting tool performance under harsh cutting conditions, including the determination of the robustness of the brazed joint.

[0079] The cutting data used is shown in Table 4. The feed rate (fn) and depth of cut (ap) were set to the same value. The recommended starting values ​​for fn and ap vary depending on the type and grade of the insert being tested. The cutting speed (vc) was 120 m / min. Table 4 TIFF0007846692000004.tif38170

[0080] The test is conducted until the blade breaks (confirmed with an optical microscope after each pass), and the test results are reported as the feed / cutting depth (or number of passes) at which the blade breaks.

[0081] For each path, the values ​​of fn and ap were increased by 0.02.

[0082] Many blades were tested to obtain reliable results. Table 5 TIFF0007846692000005.tif33170

[0083] Regarding the samples, the results showed that all failures occurred in cBN material of the expected failure size. There was no indication that the brazing would result in the weakest bond. Therefore, it can be concluded that the brazed joints of the present invention function very well. Furthermore, it should be noted that all the samples tested function very well in industry applications, since the loads used in this test method were significantly higher than those associated with typical metal machining operations of hardened steel.

Claims

1. A cutting tool (1) comprising a support (2) and a cutting edge tip (3) made of cBN or PCD, The cutting edge tip (3) of cBN or PCD is attached to the support (2) via a brazed joint (4) with a thickness of 5 to 150 μm, the support (2) is a cemented carbide containing 3 to 25% by weight of a metal binder and the remainder being WC, the metal binder mainly comprising at least 40% by weight of Ni, up to 10% by weight of Co, and 10 to 20% by weight of Fe, and the brazed joint (4) is attached to the support (2) in order from the support ( A cutting tool (1) comprising: a first TiC layer (7) adjacent to (2) with an average thickness of 10 to 400 nm; a second layer (5) with an average thickness of 0.5 to 8 μm and containing at least 5 wt% metallic Ni, 25 to 60 wt% metallic Cu, and 15 to 45 wt% metallic Ti on average; and a third layer (6) with an average thickness of 4 to 145 μm and containing 60 to 80 wt% metallic Ag and 15 to 40 wt% metallic Cu on average.

2. A cutting tool (1) comprising a support (2) and a cutting edge tip (3) made of cBN or PCD, The cutting edge tip (3) of cBN or PCD is attached to a support (2) via a brazed joint (4) with a thickness of 5 to 150 μm, the support (2) is a cemented carbide containing 3 to 25 wt% of a metal binder, up to 25 wt% of carbides or carbonitrides of one or more elements from Group 4, Group 5, or Group 6 of the periodic table, and the remainder being WC, the metal binder mainly consists of at least 40 wt% Ni, up to 10 wt% Co, and 10 to 20 wt% Fe, and the brazed joint The joint (4) comprises, in order from the support (2), a first TiC layer (7) having an average thickness of 10 to 400 nm, arranged adjacent to the support (2); a second layer (5) having an average thickness of 0.5 to 8 μm and containing an average of at least 5 wt% metallic Ni, an average of 25 to 60 wt% metallic Cu, and an average of 15 to 45 wt% metallic Ti; and a third layer (6) having an average thickness of 4 to 145 μm and containing an average of 60 to 80 wt% metallic Ag and an average of 15 to 40 wt% metallic Cu, for a cutting tool (1).

3. The cutting tool (1) according to claim 1 or 2, wherein the metallic binder in the cemented carbide of the support (2) contains 50 to 90% by weight of Ni.

4. The cutting tool (1) according to any one of claims 1 to 3, wherein the thickness of the brazed joint (4) is 10 to 100 μm.

5. The cutting tool (1) according to any one of claims 1 to 4, wherein the average thickness of the first TiC layer (7) is 50 to 300 nm.

6. The cutting tool (1) according to any one of claims 1 to 5, wherein the second layer (5) contains an average of 10 to 40% by weight of metallic Ni.

7. The cutting tool (1) according to any one of claims 1 to 6, wherein the second layer (5) contains an average of 35 to 55% by weight of metallic Cu.

8. The cutting tool (1) according to any one of claims 1 to 7, wherein the second layer (5) contains an average of 25 to 40% by weight of metallic Ti.

9. The cutting tool (1) according to any one of claims 1 to 8, wherein the average thickness of the second layer (5) is 1 to 5 μm.

10. The cutting tool (1) according to any one of claims 1 to 9, wherein the second layer (5) has a total weight of metal Ni, metal Cu, and metal Ti of an average of 70 to 100% by weight.

11. The cutting tool (1) according to any one of claims 1 to 10, wherein the third layer (6) has a total weight of metal Cu and metal Ag of 75 to 100% on average.

12. The cutting tool (1) according to any one of claims 1 to 11, wherein the outermost Ni-deficient region of the support (2) adjacent to the brazed joint (4) has an average thickness of 0.5 to 5 μm.

13. A cutting tool (1) according to any one of claims 1 to 12, which is a turning insert, a milling insert, or an end mill.

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