Cutting Tools

Abstract

A cutting tool comprising a substrate and a coating disposed on the substrate, the coating including a first layer located on the substrate, a second layer located on the first layer, and a third layer located on the second layer, the first layer being made of titanium carbonitride, the second layer being made of aluminum oxide, and the third layer being made of titanium carbonitride, a residual stress X of the first layer and a residual stress Y of the second layer satisfying the relationship of Equation 1, and the residual stress Y of the second layer and a residual stress Z of the third layer satisfying the relationship of Equation 2.

Description

[Technical field]

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

[0002] 2. Description of the Related Art Conventionally, cutting tools including a substrate and a coating disposed on the substrate have been used in cutting processes (Patent Documents 1 to 6). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-037150 A [Patent Document 2] JP 2020-116645 A [Patent Document 3] International Publication No. 2009 / 112116 [Patent Document 4] International Publication No. 2022 / 244241 [Patent Document 5] International Publication No. 2022 / 244242 [Patent Document 6] International Publication No. 2022 / 244243 Summary of the Invention

[0004] The cutting tool of the present disclosure comprises: 1. A cutting tool comprising a substrate and a coating disposed on the substrate, the coating includes a first layer disposed on the substrate, a second layer disposed on the first layer, and a third layer disposed on the second layer; the first layer is made of titanium carbonitride; the second layer is made of aluminum oxide; the third layer is made of titanium carbonitride; The residual stress X of the first layer and the residual stress Y of the second layer satisfy the relationship of Equation 1, The residual stress Y of the second layer and the residual stress Z of the third layer satisfy the relationship of Equation 2. Formula 1: X < Y Formula 2: Z < Y

Brief Description of the Drawings

[0005] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating one aspect of a cutting tool of the present disclosure. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an example of a CVD (Chemical Vapor Deposition) apparatus used in manufacturing the cutting tool of the present disclosure.

Modes for Carrying Out the Invention

[0006] [Problems to be Solved by the Present Disclosure] In recent years, the demand for improving tool life has been increasing. In particular, in high-speed turning of steel with a low carbon content, further improvement in tool life is required. Important factors for further improving tool life in high-speed turning of steel with a low carbon content include "wear resistance" and "chipping resistance". Also, from the perspective of improving wear resistance, in high-speed turning of steel with a low carbon content, a cutting tool including a substrate and a coating disposed on the substrate is used. The coating includes a first layer located on the substrate, a second layer located on the first layer, and a third layer located on the second layer. The first layer is made of titanium carbonitride, the second layer is made of aluminum oxide, and the third layer is made of titanium carbonitride. However, in such a coating, since it is difficult for the residual stress of the first layer to be sufficiently low, the "chipping resistance" may not be sufficient. Also, wear may easily occur due to minute damage caused by insufficient "chipping resistance" (that is, the "wear resistance" may not be sufficient). Therefore, it is required to extend the tool life, especially in high-speed turning of steel with a low carbon content, by combining excellent "wear resistance" and excellent "chipping resistance".

[0007] Therefore, an object of the present disclosure is to provide a cutting tool having a long tool life, especially in high-speed turning of steel with a low carbon content.

[0008] [Advantages of the Present Disclosure] According to the present disclosure, it is possible to provide a cutting tool having a long tool life, particularly in high-speed turning of steel with a low carbon content.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) The cutting tool of the present disclosure is a cutting tool including a substrate and a coating disposed on the substrate, wherein the coating includes a first layer located on the substrate, a second layer located on the first layer, and a third layer located on the second layer, the first layer is made of titanium carbonitride, the second layer is made of aluminum oxide, the third layer is made of titanium carbonitride, a residual stress X of the first layer and a residual stress Y of the second layer satisfy the relationship of Formula 1, the residual stress Y of the second layer and a residual stress Z of the third layer satisfy the relationship of Formula 2. X < Y Formula 1 Z < Y Formula 2

[0010] According to the present disclosure, it is possible to provide a cutting tool having a long tool life, particularly in high-speed turning of steel with a low carbon content.

[0011] (2) In the above (1), the residual stress X of the first layer is preferably -1.0 GPa or more and -0.3 GPa or less. Thereby, it is possible to provide a cutting tool having an even longer tool life, particularly in high-speed turning of steel with a low carbon content.

[0012] (3) In the above (1) or (2), the residual stress Y of the second layer is preferably -0.5 GPa or more and 0.1 GPa or less. Thereby, it is possible to provide a cutting tool having an even longer tool life, particularly in high-speed turning of steel with a low carbon content.

[0013] (4) In any one of the above (1) to (3), the residual stress Z of the third layer is preferably −1.0 GPa or more and −0.3 GPa or less, thereby providing a cutting tool having a longer tool life, particularly in high-speed turning of steel with a low carbon content.

[0014] (5) In any one of the above (1) to (4), the thickness of the first layer is preferably 3 μm or more and 15 μm or less, thereby providing a cutting tool having a longer tool life, particularly in high-speed turning of steel with a low carbon content.

[0015] (6) In any one of the above (1) to (5), the thickness of the second layer is preferably 3 μm or more and 15 μm or less, thereby providing a cutting tool having a longer tool life, particularly in high-speed turning of steel with a low carbon content.

[0016] (7) In any one of the above (1) to (6), the thickness of the third layer is preferably 2 μm or more and 4 μm or less, thereby providing a cutting tool having a longer tool life, particularly in high-speed turning of steel with a low carbon content.

[0017] [Details of the embodiment of the present disclosure] A specific example of a cutting tool according to an embodiment of the present disclosure (hereinafter also referred to as the "present embodiment") will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference symbols represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been appropriately changed for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0018] In this specification, the expression "A to B" means the upper and lower limits of a range (i.e., A or more and B or less). When no unit is specified for A and a unit is specified only for B, the unit of A and the unit of B are the same.

[0019] [Embodiment 1: Cutting Tool] A cutting tool according to an embodiment of the present disclosure will be described with reference to FIG. 1. One embodiment of the present disclosure (hereinafter also referred to as "this embodiment") is a cutting tool 10 including a base material 1 and a coating 2 disposed on the base material 1, the coating 2 includes a first layer 3 located on the base material 1, a second layer 4 located on the first layer 3, and a third layer 5 located on the second layer 4, the first layer 3 is made of titanium carbonitride, the second layer 4 is made of aluminum oxide, the third layer 5 is made of titanium carbonitride, the residual stress X of the first layer 3 and the residual stress Y of the second layer 4 satisfy the relationship of Formula 1, the residual stress Y of the second layer 4 and the residual stress Z of the third layer 5 satisfy the relationship of Formula 2. X < Y Formula 1 Z < Y Formula 2

[0020] According to the present disclosure, it is possible to provide a cutting tool having a long tool life even in high-speed turning of steel with a low carbon content. The reason is presumed as follows.

[0021] The residual stress X of the first layer 3 and the residual stress Y of the second layer 4 satisfy the relationship of Formula 1, the residual stress Y of the second layer 4 and the residual stress Z of the third layer 5 satisfy the relationship of Formula 2. X < Y Formula 1 Z < Y Formula 2 Thereby, the residual stress on the base material 1 side of the coating 2 and the residual stress on the surface side of the coating 2 are relatively low, and the chipping resistance can be improved. In addition, the residual stress in the region sandwiched between the region on the base material 1 side of the coating 2 and the region on the surface side of the coating 2 is relatively high, and in particular, in high-speed turning of steel with a low carbon content, it is easy to suppress the peeling due to the welding of the second layer 4 that contributes to the suppression of wear progression, so the wear resistance can be improved.

[0022] That is, according to the present disclosure, cutting tool 1 0 Since the material can combine excellent "wear resistance" and excellent "fracture resistance," it is possible to provide a cutting tool having a long tool life, especially in high-speed turning of steel with a low carbon content.

[0023] ≪Cutting tools≫ As shown in FIG. 1, a cutting tool 10 according to an embodiment of the present disclosure includes a substrate 1 and a coating 2 disposed on the substrate 1. The coating 2 preferably covers the entire surface of the substrate 1, but even if a part of the substrate 1 is not covered with the coating 2 or the configuration of the coating 2 is partially different, this does not depart from the scope of this embodiment. In the case where a part of the substrate 1 is not covered with the coating 2, the coating 2 is preferably disposed so as to cover at least the surface of the part of the substrate 1 involved in cutting. In this specification, the part of the substrate 1 involved in cutting means, depending on the size and shape of the substrate 1, a region of the substrate 1 surrounded by the cutting edge ridge and a virtual surface whose distance from the cutting edge ridge to the substrate 1 along the perpendicular line to the tangent line of the cutting edge ridge is, for example, 5 mm, 3 mm, 2 mm, 1 mm, or 0.5 mm.

[0024] The cutting tool 10 of this embodiment can be suitably used as cutting tools 10 such as drills, end mills, indexable cutting tips for drills, indexable cutting tips for end mills, indexable cutting tips for milling, indexable cutting tips for turning, metal saws, gear cutting tools, reamers, taps, etc.

[0025] ≪Base material≫ Any of the conventionally known substrates 1 of this type can be used as the substrate 1. For example, the substrate 1 is preferably any of cemented carbide (WC-based cemented carbide, cemented carbide containing WC and Co, and cemented carbide containing carbonitrides of Ti, Ta, Nb, etc.), cermet (mainly composed of TiC, TiN, TiCN, etc.), high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cubic boron nitride sintered body, and diamond sintered body.

[0026] It is particularly preferable to select a WC-based cemented carbide or a cermet (particularly a TiCN-based cermet) from among these various substrates 1. These substrates 1 have an excellent balance between hardness and strength, particularly at high temperatures, and therefore, when used as the substrate 1 of a cutting tool 10, they can contribute to extending the life of the cutting tool 10.

[0027] ≪Coating≫ The coating 2 includes a first layer 3 located on the substrate 1, a second layer 4 located on the first layer 3, and a third layer 5 located on the second layer 4. By covering the substrate 1, the coating 2 has the effect of improving various properties of the cutting tool 10, such as wear resistance and chipping resistance, and thereby extending the life of the cutting tool 10. Note that the coating 2 may include "other layers" (described later) in addition to the first layer 3, second layer 4, and third layer 5, as long as the effects of the present disclosure are not impaired.

[0028] The thickness of the coating 2 is preferably 6 μm or more and 30 μm or less. If the thickness of the coating 2 is less than 6 μm, the coating 2 is too thin, and the life of the cutting tool 10 tends to be shortened. On the other hand, if the thickness of the coating 2 exceeds 30 μm, chipping of the coating 2 is likely to occur in the early stages of cutting, and the life of the cutting tool 10 tends to be shortened. The thickness of the coating 3 can be measured by observing the cross section of the coating 2 using a scanning electron microscope (SEM). Specifically, the observation magnification of the cross-sectional sample is set to 5,000 to 10,000 times, and the observation area is set to 100 to 500 μm. 2 The thickness width is measured at three points in one visual field, and the average value is taken as the “thickness.” The same applies to the thickness of each layer described below unless otherwise specified.

[0029] <1st layer> <Composition of the first layer> The first layer 3 is made of titanium carbonitride. Here, "made of titanium carbonitride" means that in addition to titanium carbonitride, inevitable impurities can be contained, as long as the effects of the present disclosure are exhibited. Examples of the inevitable impurities include chlorine atoms (Cl). The total content of inevitable impurities in the first layer 3 is preferably greater than 0 mass% and less than 3 mass%.

[0030] It is identified by X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX) that the first layer 3 is made of titanium carbonitride. The content of inevitable impurities in the first layer 3 is measured by secondary ion mass spectrometry (SIMS). It has been confirmed that, as long as the measurements are performed using the same cutting tool 10, there is no variation in the measurement results even if the measurement points are arbitrarily selected.

[0031] <First layer structure> The thickness of the first layer 3 is preferably 3 μm or more and 15 μm or less. This allows both superior wear resistance and superior chipping resistance to be achieved, and therefore a cutting tool having a longer tool life can be provided, especially in high-speed turning of steel with a low carbon content. The lower limit of the thickness of the first layer 3 is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more. The upper limit of the thickness of the first layer 3 is preferably 15 μm or less, more preferably 13 μm or less, and even more preferably 11 μm or less. The thickness of the first layer 3 is more preferably 5 μm or more and 13 μm or less, and even more preferably 7 μm or more and 11 μm or less.

[0032] <Residual stress in the first layer> The residual stress X of the first layer 3 is preferably -1.0 GPa or more and -0.3 GPa or less. This makes it easier to suppress the spread of damage when a small defect occurs, so that a cutting tool with a longer tool life can be provided, especially in high-speed turning of steel with a low carbon content. The lower limit of the residual stress X of the first layer 3 is preferably -1.0 GPa or more, more preferably -0.9 GPa or more, and even more preferably -0.8 GPa or more. The upper limit of the residual stress X of the first layer 3 is preferably -0.3 GPa or less, more preferably -0.4 GPa or less, and even more preferably -0.5 GPa or less. The residual stress X of the first layer 3 is more preferably -0.9 GPa or more and -0.4 GPa or less, and even more preferably -0.8 GPa or more and -0.5 GPa or less.

[0033] The residual stress X of the first layer 3 can be determined by measuring the first layer 3 with an X-ray residual stress device using the sin2ψ method (see pages 54-66 of "X-Ray Stress Measurement Method" (published by Yokendo Co., Ltd. in 1981 by the Japan Society for Materials Science). The temperature during the measurement is room temperature (20°C). It has also been confirmed that, as long as the measurement is performed using the same cutting tool 10, there is no variation in the measurement results even if the measurement location is arbitrarily selected.

[0034] <2nd layer> <Composition of the second layer> The second layer 4 is made of aluminum oxide. Here, "made of aluminum oxide" means that in addition to aluminum oxide, inevitable impurities can be contained, as long as the effect of the present disclosure is exhibited. Examples of the inevitable impurities include chlorine atoms (Cl). The total content of inevitable impurities in the second layer 4 is preferably greater than 0 mass% and less than 3 mass%.

[0035] The fact that the second layer 4 is made of aluminum oxide is identified by X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX). The content of inevitable impurities in the second layer 4 is measured by secondary ion mass spectrometry (SIMS). It has been confirmed that, as long as the measurements are performed using the same cutting tool 10, there is no variation in the measurement results even if the measurement points are arbitrarily selected.

[0036] <Second layer structure> The thickness of the second layer 4 is preferably 3 μm or more and 15 μm or less. This makes it possible to achieve both better wear resistance and better chipping resistance, and therefore it is possible to provide a cutting tool with a longer tool life, especially in high-speed turning of steel with a low carbon content. The lower limit of the thickness of the second layer 4 is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 7 μm or more. The upper limit of the thickness of the second layer 4 is preferably 15 μm or less, more preferably 13 μm or less, and even more preferably 11 μm or less. The thickness of the second layer 4 is more preferably 5 μm or more and 13 μm or less, and even more preferably 7 μm or more and 11 μm or less.

[0037] <Residual stress in the second layer> The residual stress Y of the second layer 4 is preferably -0.5 GPa or more and 0.1 GPa or less. As a result, the alumina structure is not easily destroyed by the introduction of a moderate residual stress, and the chipping resistance can be improved, so that a cutting tool having a longer tool life can be provided, especially in high-speed turning of steel with a low carbon content. The lower limit of the residual stress Y of the second layer 4 is preferably -0.5 GPa or more, more preferably -0.4 GPa or more, and even more preferably -0.3 GPa or more. The upper limit of the residual stress Y of the second layer 4 is preferably 0.1 GPa or less, more preferably 0 GPa or less, and even more preferably -0.1 GPa or less. The residual stress Y of the second layer 4 is more preferably -0.4 GPa or more and 0 GPa or less, and even more preferably -0.3 GPa or more and -0.1 GPa or less.

[0038] The residual stress Y in the second layer 4 can be determined by a method similar to that for measuring the residual stress X in the first layer 3, except that the measurement is performed on the second layer 4. It has been confirmed that, as long as the measurement is performed using the same cutting tool 10, there is no variation in the measurement results even if the measurement location is arbitrarily selected.

[0039] <3rd layer> <Composition of the third layer> The third layer 5 is made of titanium carbonitride. Here, "made of titanium carbonitride" means that in addition to titanium carbonitride, inevitable impurities can be contained, as long as the effects of the present disclosure are exhibited. Examples of the inevitable impurities include chlorine atoms (Cl). The total content of inevitable impurities in the third layer 5 is preferably greater than 0 mass% and less than 3 mass%.

[0040] X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDX) identify that the third layer 5 is made of titanium carbonitride. The content of inevitable impurities in the third layer 5 is measured by secondary ion mass spectrometry (SIMS). It has been confirmed that, as long as the measurements are performed using the same cutting tool 10, there is no variation in the measurement results even if the measurement points are arbitrarily selected.

[0041] <Structure of the third layer> The thickness of the third layer 5 is preferably 2 μm or more and 4 μm or less. This allows both superior fracture resistance and superior wear resistance to be achieved, and therefore a cutting tool having a longer tool life can be provided, especially in high-speed turning of steel with a low carbon content. The lower limit of the thickness of the third layer 5 is preferably 2 μm or more, and more preferably 2.5 μm or more. The upper limit of the thickness of the third layer 5 is preferably 4 μm or less, and more preferably 3.5 μm or less. The thickness of the third layer 5 is more preferably 2.5 μm or more and 3.5 μm or less.

[0042] <Residual stress in the third layer> The residual stress Z of the third layer 5 is preferably -1.0 GPa or more and -0.3 GPa or less. By this, it is possible to suppress the non-uniform generation of minute defects that become the starting points of wear. Therefore, even in high-speed turning of steel with a low carbon content, a cutting tool having a longer tool life can be provided. The lower limit of the residual stress Z of the third layer 5 is preferably -1.0 GPa or more, more preferably -0.9 GPa or more, and still more preferably -0.8 GPa or more. The upper limit of the residual stress Z of the third layer 5 is preferably -0.3 GPa or less, more preferably -0.4 GPa or less, and still more preferably -0.5 GPa or less. The residual stress Z of the third layer 5 is more preferably -0.9 GPa or more and -0.4 GPa or less, and still more preferably -0.8 GPa or more and -0.5 GPa or less.

[0043] The residual stress Z of the third layer 5 can be specified by a method similar to the method for measuring the residual stress X of the first layer 3, except that the measurement is performed on the third layer 5. It should be noted that as long as the measurement is performed with the same cutting tool 10, it has been confirmed that there is no variation in the measurement results even if the measurement location is arbitrarily selected.

[0044] <Relationship among the first layer, the second layer, and the third layer> The residual stress X of the first layer 3 and the residual stress Y of the second layer 4 satisfy the relationship of Equation 1, The residual stress Y of the second layer 4 and the residual stress Z of the third layer 5 satisfy the relationship of Equation 2. X < Y Equation 1 Z < Y Equation 2 By this, the cutting tool 10 can have both excellent wear resistance and excellent chipping resistance. Therefore, even in high-speed turning of steel with a low carbon content, it is possible to exhibit a long tool life.

[0045] YX is preferably 0.1 or more and 0.6 or less. This makes it more difficult for chipping to occur from the first layer 3 to the second layer 4, and therefore the cutting tool 10 can have better fracture resistance. YX is more preferably 0.15 or more and 0.55 or less, and further preferably 0.2 or more and 0.5 or less.

[0046] YZ is preferably 0.1 or more and 0.6 or less. This makes it more difficult for excessive breakage of the second layer 4 to occur, so that the cutting tool 10 can have better chipping resistance and better wear resistance. YZ is more preferably 0.15 or more and 0.55 or less, and further preferably 0.2 or more and 0.5 or less.

[0047] <Other layers> Examples of the other layers include an underlayer (not shown), an intermediate layer (not shown), and a surface layer (not shown). The underlayer is a layer disposed between the substrate 1 and the first layer 3. The surface layer is a layer located on the surface of the coating 2. The intermediate layer is a layer disposed between the first layer 3 and the second layer 4, between the second layer 4 and the third layer 5, or both. The intermediate layer is a thin adhesive layer such as TiCNO. Therefore, the intermediate layer does not affect the stress distribution.

[0048] [Embodiment 2: Manufacturing method of cutting tool] The method for manufacturing the cutting tool of this embodiment will be described with reference to Fig. 2. Fig. 2 is a schematic cross-sectional view of an example of a CVD apparatus used in the manufacture of the cutting tool of this embodiment.

[0049] A method for manufacturing a cutting tool according to the present embodiment is the method for manufacturing the cutting tool according to the first embodiment, A first step of preparing a substrate; A second step of forming a coating on the substrate; and a third step of subjecting the coating to a blast treatment to obtain a cutting tool. The second step includes, in this order, a step 2A of forming a first layer by a CVD method, a step 2B of forming a second layer by a CVD method, and a step 2C of forming a third layer by a CVD method. Each step will be described in detail below.

[0050] ≪1st process≫ In the first step, a substrate is prepared. The substrate described in the first embodiment can be used.

[0051] For example, when a cemented carbide is used as the substrate, a commercially available substrate may be used, or the substrate may be manufactured by a general powder metallurgy method. When the substrate is manufactured 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. The mixed powder is dried and then molded into a predetermined shape to obtain a molded body. The molded body is further sintered to obtain a WC-Co-based cemented carbide (sintered body). Next, the sintered body is subjected to a predetermined cutting edge processing such as honing, thereby manufacturing a substrate made of a WC-Co-based cemented carbide. Substrates other than those mentioned above can also be prepared as long as they are conventionally known as substrates of this type.

[0052] ≪Second process≫ In the second step, a coating is formed on the substrate to obtain a cutting tool. The coating is formed, for example, by using a CVD apparatus shown in FIG. 2. The CVD apparatus 30 includes a plurality of substrate setting jigs 31 for holding the substrate 1, and a reaction vessel 32 made of heat-resistant alloy steel that covers the substrate setting jigs 31. A temperature control device 33 for controlling the temperature inside the reaction vessel 32 is provided around the reaction vessel 32. The reaction vessel 32 is provided with a gas introduction pipe 35 having a gas introduction port 34. The gas introduction pipe 35 is arranged to extend vertically in the internal space of the reaction vessel 32 in which the substrate setting jigs 31 are arranged, and is arranged to be rotatable about the axis of the vertical direction, and is provided with a plurality of ejection holes (through holes 36) for ejecting gas into the reaction vessel 32. Using this CVD apparatus 30, the first layer, second layer, and third layer that constitute the coating can be formed as follows.

[0053] The second step includes, in this order, a step 2A of forming a first layer by a CVD method, a step 2B of forming a second layer by a CVD method, and a step 2C of forming a third layer by a CVD method. When the coating includes the "other layer" described in the first embodiment, the "other layer" can be formed by a conventionally known method.

[0054] <Step 2A: Step of forming the first layer by CVD method> In step 2A, the first layer is formed by the CVD method. More specifically, first, the substrate 1 is placed in a substrate setting jig 31, and a raw material gas for the first layer is introduced into the reaction vessel 32 from a gas introduction pipe 35 while controlling the temperature and pressure in the reaction vessel 32 within a predetermined range. As a result, the first layer is formed on the substrate 1.

[0055] The source gas for the first layer is a mixture of TiCl4, CH3CN, CO, N2, HCl, and H2.

[0056] The TiCl4 content in the mixed gas is preferably 8.0 vol% or more and 9.0 vol% or less. The CH3CN content in the mixed gas is preferably 0.2 vol% or more and 1.0 vol% or less. The CO content in the mixed gas is preferably 1.3 vol% or more and 2.0 vol% or less. The N2 content in the mixed gas is preferably 8.0 vol% or more and 12.0 vol% or less. The HCl content in the mixed gas is preferably 1.0 vol% or more and 3.0 vol% or less.

[0057] The temperature inside the reaction vessel 32 is preferably controlled to be 800° C. or higher and 850° C. or lower, and the pressure inside the reaction vessel 32 is preferably controlled to be 100 hPa or higher and 120 hPa or lower. When introducing the gas, it is preferable to rotate the gas introduction pipe 35.

[0058] In the above-mentioned manufacturing method, the state of the first layer can be changed by controlling each condition of the CVD method. For example, the thickness of the first layer can be controlled by adjusting the film formation time.

[0059] <Step 2B: Step of forming the second layer by CVD method> In step 2B, the second layer is formed by a CVD method. More specifically, the first cutting tool precursor having the first layer formed on the substrate is placed in a substrate setting jig 31, and a raw material gas for the second layer is introduced into the reaction vessel 32 from a gas introduction pipe 35 while controlling the temperature and pressure in the reaction vessel 32 within a predetermined range. This forms the second layer on the first layer.

[0060] The source gas for the second layer is a mixture of AlCl3, CO2, H2S, and H2.

[0061] The content of AlCl3 in the mixed gas is preferably 2.0% by volume or more and 2.5% by volume or less. The content of CO2 in the mixed gas is preferably 2.5% by volume or more and 3.5% by volume or less. The content of H2S in the mixed gas is preferably 0.5% by volume or more and 1.0% by volume or less.

[0062] The temperature inside the reaction vessel 32 is preferably controlled to be 980° C. or higher and 1015° C. or lower, and the pressure inside the reaction vessel 32 is preferably controlled to be 60 hPa or higher and 75 hPa or lower. It is preferable to rotate the gas introduction pipe 35 when introducing the gas.

[0063] In the above-mentioned manufacturing method, the state of the second layer can be changed by controlling each condition of the CVD method. For example, the thickness of the second layer can be controlled by adjusting the film formation time.

[0064] <2C process: process of forming the third layer by CVD method> In step 2C, the third layer is formed by a CVD method. More specifically, first, a second cutting tool precursor having a first layer formed on a substrate and a second layer formed on the first layer is placed in a substrate setting jig 31, and a source gas for the third layer is introduced into the reaction vessel 32 from a gas introduction pipe 35 while controlling the temperature and pressure in the reaction vessel 32 within a predetermined range. This forms the third layer on the second layer.

[0065] The source gas for the third layer is a mixture of TiCl4, CH3CN, CO, N2, HCl, and H2.

[0066] The TiCl4 content in the mixed gas is preferably 8.0 vol% or more and 9.0 vol% or less. The CH3CN content in the mixed gas is preferably 0.2 vol% or more and 0.8 vol% or less. The CO content in the mixed gas is preferably 1.3 vol% or more and 2.0 vol% or less. The N2 content in the mixed gas is preferably 8.0 vol% or more and 12.0 vol% or less. The HCl content in the mixed gas is preferably 1.0 vol% or more and 3.0 vol% or less.

[0067] The temperature inside the reaction vessel 32 is preferably controlled to be 950° C. or higher and 1000° C. or lower, and the pressure inside the reaction vessel 32 is preferably controlled to be 80 hPa or higher and 100 hPa or lower. When introducing the gas, it is preferable to rotate the gas introduction pipe 35.

[0068] In the above-mentioned manufacturing method, the state of the third layer can be changed by controlling each condition of the CVD method. For example, the thickness of the third layer can be controlled by adjusting the film formation time.

[0069] <Third process: A process of obtaining a cutting tool by blasting the coating> In the third step, the coating is subjected to a blasting treatment to obtain a cutting tool. Here, "blasting" refers to a process in which a large number of small spheres (media) of steel or non-ferrous metal (e.g., ceramics) are collided (projected) at high speed onto the surface of the coating, such as the rake face, to change various properties of the surface, such as residual stress.

[0070] The types of media include, for example, ceramics, zirconia, alumina, and the like.

[0071] The average particle size of the media is, for example, 5 μm or more and 15 μm or less.

[0072] The concentration of the projected media is 100 g / min or more and 350 g / min or less. Preferably, the concentration of the projected media is 100 g / min or more and 250 g / min or less.

[0073] The distance between the projection part that projects the media and the surface of the coating (hereinafter, also referred to as "projection distance") is 30 mm or more and 55 mm or less. Preferably, the projection distance is 30 mm or more and 40 mm or less.

[0074] The projection angle of the media is 45° with respect to the surface of the coating.

[0075] Preferably, the pressure applied to the above media during projection (hereinafter, also referred to as "projection pressure") is 0.10 MPa or more and 0.50 MPa or less.

[0076] Preferably, the blasting treatment time is 15 seconds or more and 30 seconds or less.

[0077] Each of the above blasting treatment conditions can be appropriately adjusted according to the configuration of the above coating.

[0078] <Other Processes> In the manufacturing method according to the present embodiment, in addition to the above-described processes, additional processes may be appropriately performed within a range that does not impair the effects of the present embodiment.

[0079] <Features of the Manufacturing Method of the Cutting Tool of the Present Embodiment> The cutting tool obtained by the above manufacturing method is a cutting tool including a base material and a coating disposed on the base material, the coating including a first layer located on the base material, a second layer located on the first layer, and a third layer located on the second layer, the first layer being made of titanium carbonitride, the second layer being made of aluminum oxide, the third layer being made of titanium carbonitride, the residual stress X of the first layer and the residual stress Y of the second layer satisfying the relationship of Formula 1, and the residual stress Y of the second layer and the residual stress Z of the third layer satisfying the relationship of Formula 2. A cutting tool can be manufactured. X < Y Formula 1 Z < Y Formula 2 The reasons for this are presumed to be as follows.

[0080] The cutting tool manufacturing method of this embodiment is characterized in that, in the 2C step, a third layer located on the second layer is formed, and then, in the 3rd step, fine media having an average particle size of 5 to 15 μm is used, the concentration of the media projected is 100 g / min to 350 g / min, the projection angle is 45° with respect to the surface of the coating, and the projection distance is 30 mm to 55 mm. By projecting the fine media from a projection angle of 45°, stress is easily introduced to the surface side of the coating. In addition, since the concentration of the media is low, it is easy to increase the projection speed of the media, and stress is easily introduced to the substrate side of the coating. In addition, since the projection distance is close, it is possible to differentiate the stress of the third layer from the stress of the second layer. As a result, the residual stress X of the first layer and the residual stress Y of the second layer satisfy the relationship of the above formula 1, and the residual stress Y of the second layer and the residual stress Z of the third layer can satisfy the relationship of the above formula 2. This is a new finding made by the present inventors as a result of extensive investigations. EXAMPLES

[0081] The present embodiment will be described more specifically with reference to examples, although the present embodiment is not limited to these examples.

[0082] <Cutting tool manufacturing> Cutting tools according to Samples 1 to 31 and 101 to 104 were produced in the following manner.

[0083] <1st process> As the substrate, a cemented carbide indexable cutting tip (shape: Sumitomo Electric Hardmetal Corp., CNMG120408N-UX) with a composition consisting of TaC (2.0 mass%), Co (11.0 mass%) and WC (balance) (but containing unavoidable impurities) was prepared.

[0084] <Second process> A first layer was formed on the above-mentioned substrate by a CVD method under the following conditions so that the composition of the first layer was as shown in Tables 3 and 4 (Step 2A). The deposition time was appropriately adjusted so that the first layer had a thickness as shown in Tables 3 and 4. (Conditions for Step 2A) TiCl4 content in mixed gas: 8.0-9.0% by volume CH3CN content in mixed gas: 0.2-1.0% by volume CO content in mixed gas: 1.3-2.0% by volume N2 content in mixed gas: 8.0-12.0% by volume HCl content in mixed gas: 1.0-3.0% by volume H2 content in mixed gas: Remaining ·Temperature: 800~850℃ Pressure: 100~120hPa

[0085] Next, a second layer was formed on the first layer by CVD under the following conditions so that the composition of the second layer was as shown in Tables 3 and 4 (step 2B). The deposition time was appropriately adjusted so that the second layer had a thickness as shown in Tables 3 and 4. (Conditions for Step 2B) AlCl3 content in mixed gas: 2.0-2.5% by volume -CO2 content in mixed gas: 2.5-3.5% by volume H2S content in mixed gas: 0.5-1.0% by volume H2 content in mixed gas: Remaining ·Temperature: 980~1015℃ Pressure: 60~75hPa

[0086] Next, a third layer was formed on the second layer by a CVD method under the following conditions so that the composition of the third layer was as shown in Tables 3 and 4 (step 2C). The deposition time was appropriately adjusted so that the third layer had a thickness as shown in Tables 3 and 4. (Conditions for 2C process) TiCl4 content in mixed gas: 8.0-9.0% by volume CH3CN content in mixed gas: 0.2-0.8% by volume CO content in mixed gas: 1.3-2.0% by volume N2 content in mixed gas: 8.0-12.0% by volume HCl content in mixed gas: 1.0-3.0% by volume H2 content in mixed gas: Remaining ·Temperature: 950~1000℃ Pressure: 80~100hPa

[0087] <3rd process> A blasting treatment was performed on the surface of the cutting tool on which the first, second and third layers were formed (in other words, the cutting tool on which the coating was formed) under the conditions shown in Tables 1 and 2.

[0088] By the above procedure, cutting tools according to Samples 1 to 31 and 101 to 104 were produced.

[0089] [Table 1]

[0090] [Table 2]

[0091] [Table 3]

[0092] [Table 4]

[0093] <Cutting tool characteristic evaluation> <Composition of the first layer> The composition of the first layer of each sample cutting tool was determined by the method described in embodiment 1. The results are shown in the "Composition" column of the "First Layer" column in Tables 3 and 4. When "TiCN" is written in the "Composition" column of the "First Layer" column in Tables 3 and 4, it means that the first layer is made of titanium carbonitride.

[0094] <Residual stress X of the first layer> For each sample cutting tool, the residual stress X of the first layer was determined by the method described in embodiment 1. The results are shown in the "X [GPa]" column of Tables 3 and 4.

[0095] <Composition of the second layer> The composition of the second layer of each sample cutting tool was determined by the method described in embodiment 1. The results are shown in the "Composition" column of the "Second Layer" column in Tables 3 and 4. When "Al2O3" is written in the "Composition" column of the "Second Layer" column in Tables 3 and 4, it means that the second layer is made of aluminum oxide.

[0096] <Residual stress Y in the second layer> For each sample cutting tool, the residual stress Y of the second layer was determined by the method described in embodiment 1. The results are shown in the "Y [GPa]" column of Tables 3 and 4.

[0097] <Composition of the third layer> The composition of the third layer of each sample cutting tool was determined by the method described in embodiment 1. The results are shown in the "Composition" column of the "Third Layer" column in Tables 3 and 4. When "TiCN" is written in the "Composition" column of the "Third Layer" column in Tables 3 and 4, it means that the third layer is made of titanium carbonitride.

[0098] <Residual stress Z of the third layer> For each sample cutting tool, the residual stress Z of the third layer was determined by the method described in embodiment 1. The results are shown in the "Z [GPa]" column of Tables 3 and 4.

[0099] <Coating thickness> The thickness of the coating of each sample cutting tool was determined by the method described in embodiment 1. The results are shown in the "Thickness [μm]" column of the "Coating" column in Tables 3 and 4.

[0100] <Cutting test> Cutting tests were carried out using the cutting tools for each sample under the following cutting conditions. The tool life was measured as the time until damage progressed due to a combination of rake face wear and minor chipping, and chipping due to the progression of rake face wear or chipping from the ridge line occurred. The results are shown in the "Tool life [min]" column in Tables 3 and 4. (Cutting conditions) Work material: SCM420H (round bar) Processing: Round bar external diameter turning Cutting speed: 400m / min Feed rate: 0.3mm / rev Depth of cut: 2.0mm Cutting fluid: Water-soluble cutting fluid The above mentioned cutting conditions correspond to those for high speed turning of low carbon steels.

[0101] The cutting tools of Samples 1 to 31 correspond to Examples. The cutting tools of Samples 101 to 104 correspond to Comparative Examples. From the results in Tables 3 and 4, it was found that the cutting tools of Samples 1 to 31 have a longer tool life than the cutting tools of Samples 101 to 104, even in high-speed turning of steel with a low carbon content.

[0102] From the above, it was found that the cutting tools according to Samples 1 to 31 had a long tool life even in high-speed turning of steel with a low carbon content.

[0103] Although the embodiments and examples of the present disclosure have been described above, it is intended from the outset that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways.

[0104] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is indicated by the claims, not by the embodiments and examples described above, and is intended to include the meaning equivalent to the claims and all modifications within the scope. [Explanation of symbols]

[0105] REFERENCE SIGNS LIST 1 substrate, 2 coating, 3 first layer, 4 second layer, 5 third layer, 10 cutting tool, 30 CVD device, 31 substrate setting jig, 32 reaction vessel, 33 temperature control device, 34 gas inlet, 35 gas inlet pipe, 36 through hole

Claims

1. A cutting tool comprising a substrate and a coating disposed on the substrate, wherein the coating includes a first layer located on the substrate, a second layer located on the first layer, and a third layer located on the second layer, the first layer is made of titanium carbonitride, the second layer is made of aluminum oxide, the third layer is made of titanium carbonitride, the residual stress X of the first layer and the residual stress Y of the second layer satisfy the relationship of Formula 1, and the residual stress Y of the second layer and the residual stress Z of the third layer satisfy the relationship of Formula 2. A cutting tool. X < Y Formula 1 Z < Y Formula 2

2. The cutting tool according to Claim 1, wherein the residual stress X of the first layer is not less than -1.0 GPa and not more than -0.3 GPa.

3. The cutting tool according to Claim 1 or Claim 2, wherein the residual stress Y of the second layer is not less than -0.5 GPa and not more than 0.1 GPa.

4. The cutting tool according to Claim 1 or Claim 2, wherein the residual stress Z of the third layer is not less than -1.0 GPa and not more than -0.3 GPa.

5. The cutting tool according to Claim 1 or Claim 2, wherein the thickness of the first layer is not less than 3 μm and not more than 15 μm.

6. The cutting tool according to Claim 1 or Claim 2, wherein the thickness of the second layer is not less than 3 μm and not more than 15 μm.

7. The cutting tool according to Claim 1 or Claim 2, wherein the thickness of the third layer is not less than 2 μm and not more than 4 μm.

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