Surface-coated cutting tool

Abstract

Provided is a surface-coated cutting tool including a composite carbonitride layer or a composite nitride layer of Ti, Al, and V having columnar crystal grains with an NaCl-type face-centered cubic structure, wherein: the composition thereof is (AlXVYTi1-X-Y)(CαN1-α) (where Xavg, Yavg, and αavg, serving as the average values of X, Y, and α, satisfy the expressions 0.600 ≤ Xavg ≤ 0.950, 0.010 ≤ Yavg ≤ 0.300, 0.610 ≤ Xavg + Yavg ≤ 0.990, and 0.0000 ≤ αavg ≤ 0.0050) and has crystal grains having an Al content variation; Xmax, serving as the average value of the maximum values Xmax* of X, and Xmin, serving as the average value of the minimum values Xmin* of X, in the crystal grains satisfy the expression 0.020 ≤ Xmax - Xmin ≤ 0.400; and the lattice coefficient A (nm), which is calculated from an XRD pattern, and A* (nm), which is A* = 0.4045 × Xavg + 0.4130 × Yavg + 0.4242 × (1-Xavg - Yavg), satisfy |A-A*| < 0.0010 (nm).

Description

surface coated cutting tools

[0001] The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool). This application claims priority to Japanese Patent Application No. 2022-56505, filed on March 30, 2022. The entire contents of said Japanese patent application are incorporated herein by reference.

[0002] Conventionally, coated tools have been known in which a coating layer is formed on the surface of a substrate such as a tungsten carbide (hereinafter referred to as WC)-based cemented carbide, and it is known that such coated tools exhibit excellent wear resistance. Various proposals have been made to improve the coating layer.

[0003] For example, Patent Document 1 discloses a method for manufacturing a ceramic substrate comprising a substrate and an abrasion-resistant coating formed thereon, the abrasion-resistant coating being made of (Ti x , Al y , V z ) (C u , N v , O w ) (x+y+z=1, u+v+w=1, 0.2<x<1, 0≦y<0.8, 0.02≦z<0.6, 0≦u<0.7, 0.3<v≦1, and 0≦w<0.5), and the thickness of the wear-resistant coating is 0.5 μm or more and 15 μm or less, and the coated tool is said to have improved wear resistance.

[0004] Japanese Patent Application Publication No. 10-237628

[0005] The present invention has been made in consideration of the above circumstances and proposals, and an object of the present invention is to provide a coated tool that has excellent chipping resistance, thermal cracking resistance, and wear resistance even in, for example, high-speed intermittent cutting.

[0006] A surface-coated cutting tool according to an embodiment of the present invention has a substrate and a coating layer on the surface of the substrate, (a) the coating layer includes a composite nitride layer or composite carbonitride layer of Ti, Al, and V having columnar crystal grains of a face-centered cubic structure of NaCl, (b) the composite nitride or composite carbonitride is (Al Ｘ V Ｙ Ti １－Ｘ-Ｙ ) (C α N １－α) (X, Y, α average value X ａｖｇ , Y ａｖｇ , α ａｖｇ are 0.600≦X ａｖｇ ≦0.950, 0.010≦Y ａｖｇ ≦0.300, 0.610≦X ａｖｇ +Y ａｖｇ ≦0.990, 0.0000≦α ａｖｇ (c) the composite nitride layer or composite carbonitride layer has crystal grains with a varying Al content, and the maximum value X of X in the crystal grains is ｍａｘ * is the average value of X ｍａｘ and the minimum value X of X ｍｉｎ * is the average value of X ｍｉｎ However, 0.020≦X ｍａｘ -X ｍｉｎ (d) A satisfies the condition of ≦0.400; ＊ = 0.4045 x X ａｖｇ +0.4130 x Y ａｖｇ +0.4242×(1-X ａｖｇ -Y ａｖｇ ) A ＊ (nm) and the lattice constant A (nm) calculated from the XRD pattern are expressed as |A-A ＊ |<0.0010 (nm) is satisfied.

[0007] Furthermore, the surface-coated cutting tool according to the above embodiment may satisfy the following (1).

[0008] (1) The composite nitride layer or composite carbonitride layer has crystal grains having both the Al content change and the V content change, and the maximum value Y of Y in the crystal grains ｍａｘ * is the average value of Y ｍａｘ and the minimum value Y ｍｉｎ * is the average value of Y ｍｉｎ However, 0.010≦Y ｍａｘ -Y ｍｉｎ The condition of ≦0.200 must be satisfied.

[0009] The surface-coated tools have improved chipping resistance, thermal cracking resistance and wear resistance.

[0010] 1 is a schematic diagram showing an example of a longitudinal section of a surface-coated cutting tool according to an embodiment of the present invention, a perspective schematic diagram of a part of a gas supply pipe of an example of an apparatus for manufacturing a surface-coated cutting tool according to an embodiment of the present invention, and a cross-sectional schematic diagram of the gas supply pipe of FIG.

[0011] The present inventors have conducted extensive research into improving the thermal crack resistance and wear resistance of a composite nitride layer or composite carbonitride layer of Al, V, and Ti (hereinafter, sometimes referred to as "(AlVTi)CN") in high-speed interrupted cutting, for example, at a cutting speed of 300 m / min or more using an insert. As a result, they have found that sufficient chipping resistance, thermal cracking resistance, and wear resistance cannot be obtained by simply coating a (AlVTi)CN layer, but that the chipping resistance, thermal cracking resistance, and wear resistance of the layer are improved when a predetermined relationship is established between the lattice constant calculated based on the composition in accordance with Vegard's law and the lattice constant determined by XRD.

[0012] Furthermore, it was discovered that when crystal grains having varying Al content (composition) exist and the difference between the maximum and minimum values ​​satisfies a specified range, the thermal cracking resistance and chipping resistance are improved, and further, when the V content (composition) also changes in crystal grains having varying Al content (composition) and the difference between the maximum and minimum contents satisfies a specified range, the thermal cracking resistance and chipping resistance are further improved.

[0013] Hereinafter, a surface-coated cutting tool according to an embodiment of the present invention will be described. In this specification and claims, when a numerical range is expressed as "L to M" (where L and M are both numerical values), this is synonymous with "not less than L and not more than M," and the range includes an upper limit (M) and a lower limit (L). When a unit is specified for only the upper limit, the upper limit (M) and the lower limit (L) have the same unit.

[0014] 1. Coating Layer As shown in Figure 1, the coating layer (2) provided on the substrate (1) may have an underlayer (4) and an upper layer (5) described below in addition to the (AlTiV)CN layer (3), but these underlayer (4) and upper layer (5) are not essential. Each of these will be explained in turn below.

[0015] 1-1. (AlTiV)CN Layer The (AlVTi)CN layer that is always included in the coating layer will now be described.

[0016] (1) Average Thickness In this embodiment, it is preferable to have an (AlVTi)CN layer with an average thickness of 1.0 to 20.0 μm. The reason for setting the average thickness of the (AlVTi)CN layer within this range is that if the average thickness is less than 1.0 μm, the thermal crack resistance and wear resistance provided by this layer cannot be exhibited, while if it exceeds 20.0 μm, chipping resistance decreases. The average thickness is more preferably 3.0 to 15.0 μm.

[0017] (2) Crystal Grain Shape In the (AlVTi)CN layer, it is preferable to have columnar crystal grains with a NaCl-type face-centered cubic structure in the longitudinal section described below. Here, columnar crystal grains refer to crystal grains with an aspect ratio of 1.5 or more. The reason for this is that columnar crystal grains have few grain boundaries existing in a direction parallel to the substrate, so chipping originating from these grain boundaries can be suppressed. Columnar crystal grains with a NaCl-type face-centered cubic structure and an aspect ratio of 1.5 or more preferably account for 50 area% or more in the longitudinal section. If they account for 50 area% or more (or even 100 area%), chipping can be suppressed.

[0018] The aspect ratio is more preferably 2.0 or more, and the area ratio of columnar crystal grains of NaCl type face-centered cubic structure having an aspect ratio of 2.0 or more is more preferably 70 area % or more in the longitudinal section.

[0019] The reason is that if the area ratio is 70% or more (100% by area, i.e., all crystal grains may be crystal grains having a columnar structure with an aspect ratio of 2.0 or more), the occurrence of chipping can be further suppressed.

[0020] Here, the longitudinal section refers to a section perpendicular to the base when the surface of the base is considered to be flat and has no irregularities on the surface of the insert, and to a section perpendicular to the axis of a tool with a shaft.

[0021] Although there is no upper limit to the aspect ratio, the upper limit is preferably 10.0. This is because, if the aspect ratio exceeds 10.0, the columnar crystal structure becomes more susceptible to fracture, which may result in significant chipping. The method for calculating the aspect ratio will be described later.

[0022] (3) Composition (3-1) Average composition The (AlVTi)CN layer has the formula: (Al Ｘ V Ｙ Ti １－Ｘ-Ｙ ) (C α N １－α ) where X, Y, and α are the average values ​​of ａｖｇ , Y ａｖｇ , α ａｖｇ are 0.600≦X ａｖｇ ≦0.950, 0.010≦Y ａｖｇ ≦0.300, 0.610≦X ａｖｇ +Y ａｖｇ ≦0.990, 0.0000≦α ａｖｇ It is preferred that the value is ≦0.0050.

[0023] X ａｖｇ The reason for setting the content of X in the above range is that ａｖｇ If it is less than 0.600, the hardness of the (AlVTi)CN layer is insufficient and the wear resistance is reduced, while if it exceeds 0.950, the hexagonal structure of wurtzite in the layer is likely to be formed, which may cause abnormal damage such as uneven wear.

[0024] Y ａｖｇ The reason for setting the content of Y in the above range is that ａｖｇ If it is less than 0.010, the improvement in the lubricity of the (AlVTi)CN layer is insufficient, while if it exceeds 0.300, the hardness of the layer becomes insufficient, resulting in a decrease in wear resistance.

[0025] X ａｖｇ +Y ａｖｇ The reason for specifying the content range is that the lower limit is X ａｖｇ and Y ａｖｇ On the other hand, if it exceeds 0.990, the hardness of the (AlVTi)CN layer becomes insufficient, and the wear resistance decreases.

[0026] X ａｖｇ , Y ａｖｇ, and X ａｖｇ +Y ａｖｇ are respectively 0.760≦X ａｖｇ ≦0.900, 0.020≦Y ａｖｇ ≦0.050, 0.780≦X ａｖｇ +Y ａｖｇ It is more preferable that it is ≦0.950.

[0027] α ａｖｇ The reason why the content of α is set to the above range is that when it is within this range, the wear resistance of the (AlVTi)CN layer is improved, while when it is outside this range, abnormal damage such as uneven wear occurs. ａｖｇ is 0.0020≦α ａｖｇ It is more preferable that the value is ≦0.0035.

[0028] Cl is inevitably contained in the manufacturing process. The ratio Z of the number of Cl atoms to the total number of Al, Ti, V, C, N, and Cl atoms is more preferably 0.005 atomic % or more and 0.500 atomic % or less. The reason is that if it is less than 0.005 atomic %, the lubricity of the (AlVTi)CN layer may be insufficient, resulting in reduced wear resistance. On the other hand, if it exceeds 0.500 atomic %, the hardness may be reduced, resulting in insufficient wear resistance of the rake face of the layer, resulting in early wear. It is even more preferable that Z is 0.005 atomic % or more and 0.100 atomic % or less.

[0029] (3-2) Content Change There are crystal grains having a predetermined content (composition) change of Al within the grains, and the maximum value X of the Al content X in the crystal grains ｍａｘ * is the average value of X ｍａｘ and the minimum value X of X ｍｉｎ * is the average value of X ｍｉｎ However, 0.020≦X ｍａｘ -X ｍｉｎ It is preferable that the maximum value Y of the V content Y in the crystal grains is 0.400 or less in order to further improve the thermal crack resistance and chipping resistance. ｍａｘ * is the average value of Y ｍａｘ and the minimum value Y ｍｉｎ * is the average value of Y ｍｉｎ However, 0.010≦Y ｍａｘ-Y ｍｉｎ When the range of 0.200 or less is satisfied, the thermal cracking resistance and chipping resistance of the coated tool are further improved. Here, the subscript "*" indicates that the value is determined for each crystal grain.

[0030] The proportion of crystal grains having a change in the Al content alone or in the contents of both Al and V within the grains is 50 area % or more, more preferably 70 area % or more (it may be 100 area %) in the longitudinal section, because if it is less than 70 area %, the thermal crack resistance and chipping resistance of the coated tool may be reduced when subjected to high-speed interrupted cutting.

[0031] (3-3) (Al Ｘ V Ｙ Ti １－Ｘ-Ｙ ) and (C α N １－α ) and the ratio (Al Ｘ V Ｙ Ti １－Ｘ-Ｙ ) and (C α N １－α The ratio of Al to Al is not particularly limited. Ｘ V Ｙ Ti １－Ｘ-Ｙ ) is set to 1, (C α N １－α The ratio of (Al) to (Al) is preferably 0.8 to 1.2. Ｘ V Ｙ Ti １－Ｘ-Ｙ ) to (C α N １－α ) within the above range, the above-mentioned object can be more reliably achieved.

[0032] (3-4) NaCl-Type Face-Centered Cubic Structure The (AlVTi)CN layer preferably contains crystal grains having a NaCl-type face-centered cubic structure. That is, in the longitudinal section, the proportion of crystal grains having a NaCl-type face-centered cubic structure is preferably 50 area % or more, more preferably 70 area % or more. Furthermore, all crystal grains (area proportion 100%) may have a NaCl-type face-centered cubic structure.

[0033] (4) Lattice constant difference The lattice constant (A) calculated from the composition of the (AlVTi)CN layer ＊It is preferable that the difference between the lattice constant (A (nm)) obtained by XRD and the lattice constant (A (nm)) is a predetermined value. ＊ It is preferable that |<0.0010 (nm). The reason is that if it is 0.0010 or more, the number of crystal grains having a crystal structure other than the NaCl-type face-centered cubic structure increases, and the wear resistance of the (AlVTi)CN layer decreases.

[0034] Here, A ＊ is calculated from the following formula according to Vegard's law, and A ＊ = 0.4045 × X + 0.4130 × Y + 0.4242 × (1 − X − Y).

[0035] In contrast, A is determined by powder X-ray diffraction measurement in a state where the influence of residual stress has been eliminated (after removing as much of the substrate as possible from the (AlVTi)CN layer by polishing, etching, etc., and then pulverizing the (AlVTi)CN layer), calculating the values ​​of the lattice spacings d(111) and d(200) from the diffraction angles of the 111 diffraction line and the 200 diffraction line in the obtained X-ray diffraction pattern, and calculating A(111) or A(200) defined as A(111) = √3d(111) and A(200) = 2d(200), and then calculating the average of these values.

[0036] Here, the X-ray diffraction pattern is determined, for example, as follows. Measurement is performed using a PANalytical Empyrean manufactured by Spectris Corporation as the X-ray diffractometer, with CuKα radiation, using the 2θ-θ method. The measurement conditions are: measurement range (2θ): 15 to 135 degrees, X-ray output: 45 kV, 40 mA, divergence slit: 0.5 degrees, scan step: 0.013 degrees, and measurement time per step: 0.16 seconds / step. The diffraction angle is calculated using the WPPD method (Whole-powder-pattern Decomposition method; see, for example, Bulletin of the Japan Institute of Metals, Vol. 28, No. 3 (1989), p. 189).

[0037] 1-2. Other Layers The (AlVTi)CN layer of this embodiment is sufficient to achieve the above-mentioned object, but an underlayer and / or an upper layer may also be provided.

[0038] (1) Underlayer The underlayer is composed of one or more Ti compound layers selected from the group consisting of Ti carbide, nitride, carbonate, and oxycarbonitride layers (the composition of these Ti compound layers is not limited to a stoichiometric composition), and has a total average layer thickness of 0.1 to 20.0 μm. The underlayer improves adhesion between the (AlVTi)CN layer and the substrate.

[0039] (2) Upper Layer The upper layer has an average total thickness of 0.1 to 25.0 μm, including the aluminum oxide layer (not limited to the stoichiometric composition). The upper layer improves wear resistance.

[0040] (3) Unintended Layers In this embodiment, no layers other than the underlayer, (AlVTi)CN layer, and upper layer are intentionally formed. However, due to unpredictable changes in the furnace pressure or temperature when switching the deposition gas, there is a possibility that unintended layers other than these layers may be formed.

[0041] 2. Substrate (1) Material Any conventionally known substrate material can be used as long as it does not impede the achievement of the object of the present invention. For example, WC-based cemented carbide (containing Co in addition to WC, and also containing carbonitrides of Ti, Ta, Nb, etc.), cermet (containing TiC, TiN, TiCN, etc. as its main component), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide), or cBN sintered body is preferred.

[0042] (2) Shape The shape of the substrate is not particularly limited as long as it is a shape that can be used as a cutting tool, and examples thereof include the shape of an insert and the shape of a drill.

[0043] 3. Manufacturing Method The (AlVTi)CN layer of this embodiment is manufactured by, for example, NH ３ , Ar, H ２ and a gas group A containing TiCl ４ , VCl ４ , AlCl ３ , Ar, N ２ , C ２ H ４ , H ２ The deposition can be carried out by a CVD method using a gas group B containing the above.

[0044] Here, gas groups A and B are supplied separately into the space within the reaction chamber of the thermal CVD apparatus up to just before the object to be deposited (substrate). Then, gas groups A and B are mixed and reacted just before the object to be deposited in the reaction chamber. This is an effective method for uniformly depositing a film across the deposition region using gas species that are highly reactive with each other, and detailed technical details are disclosed, for example, in Japanese Patent Publication No. 6,358,420.

[0045] The film forming apparatus described in the publication has a gas supply pipe as shown in Figures 2 and 3, the structure of which will be described below. As shown in Figures 2 and 3, the gas supply pipe (6), which is a cylindrical pipe that rotates around its center at a predetermined rotational speed, has its interior divided into approximately two equal parts by a partition member extending along its axial direction, and has a gas group A flow section (9) and a gas group B flow section (10).

[0046] As shown in FIG. 2, the gas supply pipe (6) is provided with a plurality of gas group A outlets (7) and gas group B outlets (8) along the axial direction, which constitute pairs of outlets located at approximately the same height.

[0047] The gas group A outlet (7) and the gas group B outlet (8) shown in Figure 3 belong to the same outlet pair, and the distance (14) between the center (11) of the outer peripheral opening end of the gas group A outlet (7) and the center (12) of the outer peripheral opening end of the gas group B outlet (8) is set to a predetermined value. Also, the angle (15) formed by the center (11) of the outer peripheral opening end of the gas group A outlet (7), the center (13) of the rotation axis of the gas supply pipe, and the center (12) of the outer peripheral opening end of the gas group B outlet (8) projected onto a plane perpendicular to the rotation axis is set to a predetermined value.

[0048] 4. Measurement Method The following describes the measurement method for each numerical value in this embodiment. In the description of this specification, the longitudinal section refers to a cross section perpendicular to the surface of the substrate when the insert is treated as a flat surface, ignoring minute irregularities on the surface of the substrate. In addition, in this specification, the surface of the substrate refers to the average line (straight line) of the interface roughness between the substrate and the coating layer in the observed image of the longitudinal section. The direction perpendicular to this average line is the direction perpendicular to the substrate (thickness direction of the coating layer). Even if the substrate has a curved surface, such as a drill, the surface of the substrate can be determined using a similar method. The longitudinal section is prepared by polishing the coating layer using a focused ion beam system (FIB), a cross section polisher (CP), or the like.

[0049] (1) Average Thickness A vertical section (when the coated tool is an insert, a vertical section including a flank is preferable) is observed with a scanning electron microscope, with a rectangular measurement area being 100 μm in the horizontal direction (direction parallel to the surface of the substrate) and allowing the entire thickness of the coating layer to be observed in the vertical direction (thickness direction of the coating layer). The average value of the thicknesses measured at multiple locations (for example, five locations) is taken as the average thickness.

[0050] (2) The area ratio of crystal grains with a NaCl-type face-centered cubic structure to columnar crystal grains with an aspect ratio of 1.5 or more and 2.0 or more. In the measurement region of the longitudinal cross section, an electron backscatter diffraction (EBSD) analyzer is used. For example, a measurement region including the entire thickness of the (AlTiV)CN layer and containing 20 or more crystal grains to be measured is irradiated with an electron beam at an incident angle of 70 degrees, an accelerating voltage of 15 kV, an irradiation current of 1 nA, and an interval of 0.01 μm. The crystal structure is analyzed based on the obtained electron backscatter diffraction image, thereby defining the boundaries of regions with different crystal structures and identifying the crystal grains. By analyzing this crystal structure, the area ratio of crystal grains determined to have a NaCl-type face-centered cubic structure is determined.

[0051] Then, image processing is performed on the crystal grains determined to have an NaCl-type face-centered cubic structure, and the maximum length Hi of this crystal grain i in the direction perpendicular to the surface of the substrate (the direction perpendicular to the surface when the surface of the substrate is treated as a flat surface), the particle width Wi, which is the maximum length of the crystal grain i in the direction horizontal to the substrate (the direction parallel to the surface when the surface of the substrate is treated as a flat surface), and the area Si of the crystal grain i are calculated. The aspect ratio Ai of the crystal grain i is calculated as Ai = Hi / Wi. The aspect ratio A is then calculated according to [Equation 1] (n in [Equation 1] is 20 or more).

[0052]

[0053] (3) Values ​​of X, Y, and α The values ​​of X and Y that define the composition of the (AlVTi)CN layer can be determined, for example, by using an electron probe microanalyzer (EPMA) to irradiate the surface of a polished longitudinal section of the (AlVTi)CN layer with an electron beam (beam diameter: 1 μm) and averaging the 10-point analysis results of the characteristic X-rays obtained. Alternatively, the polished surface of the longitudinal section of the (AlVTi)CN layer can be irradiated with an electron beam using energy dispersive X-ray spectroscopy (EDS) to perform multiple line analyses (e.g., five lines) in the thickness direction of the (AlVTi)CN layer, and the average values ​​can be determined based on the composition analysis results of Al, Ti, and V obtained.

[0054] Furthermore, α is determined by secondary ion mass spectrometry (SIMS). That is, the content in the depth direction of the (AlVTi)CN layer is measured by alternately repeating surface analysis using an ion beam and etching using a sputtered ion beam. Specifically, the average value of the C and N contents measured at a depth of at least 1 μm at a pitch of 0.1 μm or less in the thickness direction from the surface of the coating layer of the (AlVTi)CN layer is determined, and the average value of C / (C+N) calculated from this measurement at at least 10 locations is determined as the C content.

[0055] In addition, the maximum value X of the Al content X in a crystal grain having a change in the content of only Al or both Al and V within the grain ｍａｘ * is the average value of X ｍａｘ and the minimum value X of X ｍｉｎ * is the average value of X ｍｉｎ , the maximum value Y of the V content Y ｍａｘ * is the average value of Y ｍａｘ and the minimum value Y ｍｉｎ * is the average value of Y ｍｉｎ Furthermore, the area ratio of the crystal grains having predetermined changes in the content of Al and V in the (AlVTi)CN layer can be calculated, for example, as follows.

[0056] A vertical cross section of the (AlVTi)CN layer is observed at an appropriate magnification from 160,000 to 320,000 times using an energy dispersive X-ray spectrometer attached to a scanning transmission electron microscope (STEM).

[0057] Then, a rectangular observation field is set in the longitudinal section of the (AlVTi)CN layer so that the longitudinal length includes the entire thickness of the AlVTi)CN layer and the lateral length is set to 2 μm or more in the direction parallel to the surface of the substrate, and the content (X) of Al in the total amount of V, Ti, and Al and the content (Y) of V in the total amount of V, Ti, and Al are determined over the entire observation field.

[0058] For each crystal grain (not limited to those with a NaCl-type face-centered cubic structure) included in the entire observation field, the distribution of the Al content (X) in the total amount of V, Ti, and Al, and the V content (Y) in the total amount of V, Ti, and Al is calculated, and the maximum value X ｍａｘ * and minimum value X ｍｉｎ * and maximum value Y ｍａｘ * and minimum Y ｍｉｎ * are the average values ​​of X and Y (X ａｖｇ * and Y ａｖｇ *), the crystal grain is judged to contain a change in the Al content (composition) only, or in the Al and V content (composition).

[0059] That is, a crystal grain having a change in the content of only Al or both Al and V within the grain refers to a region that combines (totals) crystal grains that are determined to have a change in the content of only Al or both Al and V. The maximum value X measured in each crystal grain ｍａｘ *, minimum value X ｍｉｎ *The average value of each is the maximum value X ｍａｘ , minimum value X ｍｉｎ , maximum value Y ｍａｘ *, minimum value Y ｍｉｎ *The average value of each is the maximum value Y ｍａｘ , minimum value Y ｍｉｎ Let's say.

[0060] The average value of X in the region including the change in the content of Al (X ａｖｇ It is more preferable that regions having a difference of +1% or more with respect to the average particle diameter (A) (high Al content regions) and regions having a difference of -1% or more with respect to the average particle diameter (A) (*) are distributed in a mesh, layer, or granular pattern. Furthermore, it is even more preferable that the minimum distance between the outer edges of high Al content regions separated by low Al content regions, or between the outer edges of low Al content regions separated by high Al content regions, is 1 nm or more and less than 50 nm.

[0061] The reason is that when the minimum value of the interval of change in the Al content is within this range, the thermal cracking resistance and chipping resistance of the coated tool are improved, but if it is less than 1 nm, the improvement in thermal cracking resistance may not be sufficient, and if it is 50 nm or more, the improvement in chipping resistance may not be sufficient.

[0062] In the observation field, the proportion of the total area of ​​crystal grains having a predetermined change in the content of only Al within the grains, and the proportion of the total area of ​​crystal grains having a predetermined change in the content of Al and V within the grains are defined as the area proportion of crystal grains having a predetermined change in the content of only Al within the (AlVTi)CN layer and the area proportion of crystal grains having a predetermined change in the content of Al and V within the grains, respectively.

[0063] Furthermore, even if the (AlVTi)CN layer contains a small amount of unavoidable impurities (impurities that are unintentionally contained) such as oxygen, this does not hinder the achievement of the above-mentioned object.

[0064] (4) Z Value The Cl content in the (AlVTi)CN layer is determined, for example, by using an EPMA to irradiate a polished vertical cross section of a sample with an electron beam and obtain the chlorine content from the analysis results of the characteristic X-rays.

[0065] The above description includes the following additional features: (Additional Note 1) A surface-coated cutting tool having a substrate and a coating layer on the surface of the substrate, (a) the coating layer includes a composite nitride layer or composite carbonitride layer of Ti, Al, and V having columnar crystal grains of a face-centered cubic structure of NaCl, (b) the composite nitride or composite carbonitride is (Al Ｘ V Ｙ Ti １－Ｘ-Ｙ ) (C α N １－α ) (X, Y, α average value X ａｖｇ , Y ａｖｇ , α ａｖｇ are 0.600≦X ａｖｇ ≦0.950, 0.010≦Y ａｖｇ ≦0.300, 0.610≦X ａｖｇ +Y ａｖｇ ≦0.990, 0.0000≦α ａｖｇ (c) the composite nitride layer or composite carbonitride layer has crystal grains with a varying Al content, and the maximum value X of X in the crystal grains is ｍａｘ * is the average value of X ｍａｘ and the minimum value X of X ｍｉｎ * is the average value of X ｍｉｎ However, 0.020≦X ｍａｘ -X ｍｉｎ (d) A satisfies the condition of ≦0.400; ＊ = 0.4045 x X ａｖｇ +0.4130 x Y ａｖｇ +0.4242×(1-X ａｖｇ -Y ａｖｇ ) A ＊ (nm) and the lattice constant A (nm) calculated from the XRD pattern are expressed as |A-A ＊The surface-coated cutting tool is characterized in that the composite nitride layer or composite carbonitride layer has crystal grains having both the Al content change and the V content change, and the maximum value Y of Y in the crystal grains satisfies |<0.0010. ｍａｘ * is the average value of Y ｍａｘ and the minimum value Y ｍｉｎ * is the average value of Y ｍｉｎ However, 0.010≦Y ｍａｘ -Y ｍｉｎ ≦0.200. (Appendix 3) The surface-coated cutting tool according to Appendix 1, wherein the crystal grains having a varying Al content account for 50 area % or more and 100 area % or less in the longitudinal section. (Appendix 4) The surface-coated cutting tool according to any one of Appendixes 1 to 3, wherein, in the crystal grains having a varying Al content, the minimum value of the spacing between outer edges of high Al content regions separated by low Al content regions, or between outer edges of low Al content regions separated by high Al content regions, is 1 nm or more and less than 50 nm. (Appendix 5) The surface-coated cutting tool according to Appendix 2, wherein the crystal grains having both a varying Al content and a varying V content account for 50 area % or more and 100 area % or less in the longitudinal section. (Appendix 6) The surface-coated cutting tool according to any one of Appendixes 1 to 5, wherein the columnar crystal grains having an NaCl-type face-centered cubic structure account for 50 area % or more in the longitudinal section. (Appendix 7) The surface-coated cutting tool according to any one of Appendices 1 to 6, wherein the columnar crystal grains of the NaCl-type face-centered cubic structure have an aspect ratio of 1.5 or more. (Appendix 8) The surface-coated cutting tool according to any one of Appendices 1 to 7, wherein a ratio Z of the number of Cl atoms to the total number of Al, Ti, V, C, N, and Cl atoms is 0.005 atomic % or more and 0.500 atomic % or less.

[0066] The present invention will be described below with reference to examples, but is not limited to these examples. That is, an insert cutting tool using a WC-based cemented carbide as the substrate material will be described. However, the substrate material may be any of the above-mentioned materials, and the shape thereof may be that of a drill or the like, as described above.

[0067] 1. Manufacturing of the substrate As raw material powders, WC powder, TiC powder, TaC powder, NbC powder, Cr ３ C ２ These raw material powders were blended to the composition shown in Table 1, and wax was added thereto. The mixture was ball milled in acetone for 24 hours, dried under reduced pressure, and then pressed into a powder compact of a predetermined shape at a pressure of 98 MPa.

[0068] Thereafter, this compact was vacuum sintered under conditions of 5 Pa vacuum and 1420°C for 1 hour, and after sintering, WC-based cemented carbide substrates a to c having the insert shape of SEMT13T3AGSN-JM manufactured by Mitsubishi Materials Corporation, with the cutting edge portion honed to R: 0.06 mm, and WC-based cemented carbide substrates d to f having the insert shape of CNMG120408-MA manufactured by Mitsubishi Materials Corporation, with the cutting edge portion honed to R: 0.05 mm, were produced.

[0069] 2. Film Formation An (AlVTi)CN layer was formed on the surface of each of the substrates a to f using a CVD apparatus to obtain Examples 1 to 11 shown in Table 5. The film formation conditions were as shown in Table 2, and were roughly as follows:

[0070] Reaction gas composition (the content (%) of gas components is expressed as volume % when the total of gas group A and gas group B is 100 volume %): Gas group A: TiCl ４ :0.01~0.30%, AlCl ３ :0.30~1.60%, VCl ４ :0.05~0.70%, Ar:5.0~10.0%, N ２ :0.0~10.0%, C ２ H ４ :0.0~0.5%, H ２ : Remaining Gas group B: NH ３ :1.00~3.50%, N ２ :0.0~12.0%, H ２ : 30.0 to 50.0% Reaction atmosphere pressure: 4.0 to 5.0 kPa Reaction atmosphere temperature: 700 to 900°C

[0071] Here, gas group A and gas group B were supplied as source gas A and source gas B, respectively, to the CVD apparatus described in the aforementioned Japanese Patent No. 6358420. The rotation speed of the gas supply pipe, the distance (14) between the center (11) of the outer peripheral opening end of the gas group A outlet (7) of the gas supply pipe and the center (12) of the outer peripheral opening end of the gas group B outlet (8), and the angle (15) formed by the center (11) of the outer peripheral opening end of the gas group A outlet (7), the center (13) of the rotation axis of the gas supply pipe, and the center (12) of the outer peripheral opening end of the gas group B outlet (8) projected onto a plane perpendicular to the rotation axis are as follows:

[0072] Gas supply pipe rotation speed: 30 rpm Distance (14): 6 mm Angle (15): 16 degrees

[0073] In Examples 1 to 11, as shown in Table 4, under the conditions shown in Table 3, only the underlayer or both the underlayer and the upper layer were formed in some of the examples.

[0074] For comparison, (AlVTi)CN layers were formed on the surfaces of substrates a to f under the film formation conditions shown in Table 2, and Comparative Examples 1 to 10 shown in Table 5 were obtained.

[0075] In the example, gas groups A and B were supplied separately within the reaction chamber of the thermal CVD apparatus until just before the film formation target, where they mixed and reacted. However, in the comparative example, the source gas was not separated into two systems but was supplied into the reaction chamber of the thermal CVD apparatus from a single gas supply pipe. Therefore, a gas supply pipe was used in which there was no distinction between the gas group A outlet (9) and the gas group B outlet (10), and no pair of outlets existed.

[0076] In Comparative Examples 1 to 10, as shown in Table 4 under the conditions shown in Table 3, only the underlayer or both the underlayer and the upper layer were formed in some of the comparative examples.

[0077]

[0078]

[0079]

[0080]

[0081] In Table 4, "-" indicates that there is no corresponding layer, and type 1 indicates that there is neither a base layer nor an upper layer.

[0082]

[0083] In Table 5, Y ａｖｇ is less than 0.001, α ａｖｇ When Y is less than 0.0001 and Z is less than 0.001 atomic %, they are below the analytical limit. ａｖｇ and Z is 0.000, α ａｖｇ can be regarded as 0.0000. ｍａｘ -Y ｍｉｎ The "-" in ａｖｇ is less than 0.001, the V element is below the detection limit, and Y ｍａｘ -Y ｍｉｎ This indicates that it is not possible to calculate (there is no change in content).

[0084] In addition, "existence in a mesh-like, layered, or granular form" means "an average value of X (X ａｖｇ *) and regions (high Al content regions) where there is a difference of +1% or more from the reference value (*), and regions (low Al content regions) where there is a difference of -1% or more are distributed in a mesh-like, layered or granular form, and a "○" indicates that there is a distribution, and a "-" indicates that there is no distribution. The "minimum value of the distance between the outer edges of each region" means "the minimum value of the distance between the outer edges of high Al content regions separated by low Al content regions, or the minimum value of the distance between the outer edges of low Al content regions separated by high Al content regions."

[0085] Next, for Examples 1 to 11 and Comparative Examples 1 to 10, the following cutting tests 1 and 2 were carried out with each sample clamped to the tip of a tool steel cutter with a cutter diameter of 125 mm using a fixing jig, and the flank wear width of the cutting edge was measured.

[0086] Cutting test 1: Dry high-speed face milling, center cut cutting Cutter diameter: 125 mm Workpiece: JIS S55C block material, width 100 mm, length 400 mm Rotation speed: 891 / min Cutting speed: 350 m / min Depth of cut: 2.0 mm Feed per tooth: 0.2 mm / tooth Cutting time: 20.2 minutes (normal cutting speed is 150-250 m / min)

[0087] Cutting test 2: Dry high-speed intermittent cutting Workpiece: JIS S55C round bar with four longitudinal grooves spaced equally apart Cutting speed: 300 m / min Depth of cut: 2.0 mm Feed: 0.2 mm / rev Cutting time: 10 minutes (normal cutting speed is 150-200 m / min)

[0088] Tables 6 and 7 show the results of Cutting Test 1 and Cutting Test 2, respectively. Note that for Comparative Examples 1 to 10, the end of life was reached due to chipping before the end of the cutting time, so the time (minutes) until the end of life is shown instead of the flank wear width (mm).

[0089]

[0090]

[0091] As is clear from the results shown in Tables 6 and 7, none of the Examples experienced chipping, had improved fracture resistance, and demonstrated excellent cutting performance over a long period of time. In contrast, in Comparative Examples 1 to 10, chipping occurred before the end of the cutting time, and the cutting life was reached in a short period of time.

[0092] The above-disclosed embodiments are merely illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not by the above-disclosed embodiments, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0093] REFERENCE SIGNS LIST 1 substrate 2 coating layer 3 (AlVTi)CN layer 4 underlayer 5 upper layer 6 gas supply pipe 7 gas group A outlet 8 gas group B outlet 9 gas group A flow section 10 gas group B flow section 11 center of outer peripheral opening end of gas group A outlet 12 center of outer peripheral opening end of gas group B outlet 13 center of rotation axis 14 distance 15 angle

Claims

1. A surface-coated cutting tool having a substrate and a coating layer on a surface of the substrate, (a) the coating layer includes a layer of a composite nitride of Ti, Al, and V or a layer of a composite carbonitride having columnar crystal grains of a NaCl type face-centered cubic structure, (b) The composite nitride or composite carbonitride is (Al Ｘ V Ｙ Ti １－Ｘ-Ｙ ) (C α N １－α ) (X, Y, α average value X ａｖｇ , Y ａｖｇ , α ａｖｇ Each of them is 0.600≦X ａｖｇ ≦0.950, 0.010≦Y ａｖｇ ≦0.300, 0.610≦X ａｖｇ +Y ａｖｇ ≦0.990, 0.0000≦α ａｖｇ ≦0.0050), (c) The composite nitride layer or composite carbonitride layer has crystal grains having a change in Al content, and the maximum value X of X in the crystal grains ｍａｘ * is the average value of X ｍａｘ and the minimum value X of X ｍｉｎ * is the average value of X ｍｉｎ However, 0.020≦X ｍａｘ -X ｍｉｎ ≦0.400 is satisfied, (d) A ＊ = 0.4045 x X ａｖｇ +0.4130 x Y ａｖｇ +0.4242×(1-X ａｖｇ -Y ａｖｇ ) A ＊ (nm) and the lattice constant A (nm) calculated from the XRD pattern. | A-A ＊ | < 0.0010 (nm) A surface-coated cutting tool comprising:

2. The composite nitride layer or composite carbonitride layer has crystal grains having both the change in Al content and the change in V content, and the maximum value Y of Y in the crystal grains ｍａｘ * is the average value of Y ｍａｘ and the minimum value Y ｍｉｎ * is the average value of Y ｍｉｎ However, 0.010≦Y ｍａｘ -Y ｍｉｎ 2. The surface-coated cutting tool according to claim 1, characterized in that it satisfies ≦0.200.