Surface coated cutting tools

Abstract

To provide a surface coated cutting tool having wear resistance and thermal crack resistance.SOLUTION: In a surface coated cutting tool, a) a coating layer has an upper layer, an intermediate layer, and a lower layer, b) the upper layer has an average thickness of 1.0 to 10.0 μm and contains an α-Al2O3 layer, c) there is a crack on a cross section of the α-Al2O3 layer parallel to a substrate and density of the crack is 0.4 to 6.5 cracks / mm, d) the intermediate layer has an average thickness of 1.5 to 5.0 μm and contains a TiCN layer, e) the lower layer has an average thickness of 3.0 to 10.0 μm and contains a composite nitride layer or a composite carbonitride layer of Ti and Al, f) the composite nitride layer or the composite carbonitride layer of Ti and Al contains crystal grains of a NaCl type face-centered cubic structure of 80 to 100 area% in a longitudinal section of the coating layer, and an average composition thereof is (Ti1-XavgAlXavg)(CYavgN1-Yavg)(0.70≤Xavg≤0.90, 0.000≤Yavg≤0.050).SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool).

Background Art

[0002] Conventionally, there has been a coated tool in which a coating layer is coated on the surface of a substrate such as a tungsten carbide (hereinafter sometimes referred to as WC)-based cemented carbide in order to extend the life of a cutting tool, and this coated tool has improved wear resistance and the like. And in order to further improve the cutting performance of the coated tool, various proposals have been made regarding the composition and structure of the coating layer.

[0003] For example, Patent Document 1 describes a coated tool having an Al2O3 layer on a coating layer of Ti 1-x Al x N layer and / or Ti 1-x Al x C layer and / or Ti 1-x Al x CN layer (where x is 0.65 to 0.95), and this coated tool is said to be excellent in durability because the coating layer has heat insulation properties.

[0004] Also, for example, Patent Document 2 discloses an inner layer of Ti in which the average thickness of the coating layer is 4 to 14 μm 1-x Al x N, an intermediate layer of TiCN of the same 0.05 to ?1 1 μm, and at least one outer layer of α-Al2O3 of the same 1 to 9 μm, where the texture coefficient TC(hkl) of the α-Al2O3 layer is TC(hkl)=[I(hkl) / I0(hkl)] ?1 [where the (hkl) reflections used in the calculation are (0 2 4), (1 1 6), (3 0 0), and (0 0 12), I(hkl) = the measured intensity (peak intensity) of the (hkl) reflection, I0(hkl) = Standard intensity according to ICDD PDF card No. 00 - 042 - 1468 n = number of reflections, There is described a coated tool where 3 < TC(0 0 12) < 4, and the coated tool is said to have improved wear resistance and resistance to comb - shaped cracks.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of the above circumstances and the above proposals, and an object thereof is to obtain a surface - coated cutting tool having excellent chipping resistance in cutting operations including high - speed intermittent cutting.

Means for Solving the Problems

[0007] The 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, and the coating layer has at least three layers: an upper layer, an intermediate layer, and a lower layer. (a) The upper layer has an average thickness of 1.0 to 10.0 μm and includes an α - Al2O3 layer. (b) Cracks exist in the cross - section parallel to the substrate of the α - Al2O3 layer, and the density of the cracks is 0.4 to 6.5 cracks / mm. (c) The intermediate layer has an average thickness of 1.5 to 5.0 μm and includes a TiCN layer. (d) The lower layer has an average thickness of 3.0 to - 10.0 μm and includes a composite nitride layer or a composite carbonitride layer of Ti and Al. It should be noted that there seems to be an error in the original text where it says "3.0 to - 10.0 μm" in item (d). It is assumed this should be "3.0 to 10.0 μm" and the translation is made accordingly.(e) The composite nitride layer or composite carbonitride layer of Ti and Al contains 80 to 100 area% of crystal grains having a face-centered cubic structure of the NaCl type in the longitudinal section of the coating layer, and its average composition is (Ti 1-Xavg Al Xavg )(C Yavg N 1-Yavg )(0.70 ≦ Xavg ≦ 0.90, 0.000 ≦ Yavg ≦ 0.050).

[0008] Furthermore, the surface-coated cutting tool according to the embodiment may satisfy at least one of the following (1) to (4).

[0009] (1) The orientation index TC(0 0 12) of the α-Al2O3 layer is 6.0 or more and 7.0 or less, and the distribution ratio of Σ3 in the entire ΣN+1 of the α-Al2O3 layer in the graph of the distribution of constituent atom shared lattice points is 40% or more and 100% or less. Here, TC(0 0 12) = [I(0 0 12) / I0(0 0 12)] ×[(1 / 7)×Σ(I(hkl) / I0(hkl)] ?1 However, I(0 0 12): Measured value of the X-ray diffraction peak intensity on the (0 0 12) plane I0(0 0 12): Average value of the standard X-ray diffraction peak intensity on the (0 0 12) plane of the crystal plane of Al2O3 described in ICDD card 00-042-1468 Σ(I(hkl) / I0(hkl)): Sum of the values of ([Measured value of X-ray diffraction peak intensity] / [Average value of standard diffraction peak intensity of Al2O3 published in ICDD card]) for each of the seven planes of (0 1 2), (1 0 4), (1 1 3), (1 1 6), (3 0 0), (2 1 4), and (0 0 12)

[0010] (2) The α-Al2O3 layer has crystals with a residual stress of 0 to +300 MPa. (3) In the α-Al2O3 layer, ρα = [S] / ([Al] + [O] + [S]) (where [Q] represents the number of atoms of element Q) is 0.00001 to 0.00050.

[0011] (4) The orientation index TC(422) of the TiCN layer is 2.0 or more and 4.0 or less. Here, TC(422) = [I(422) / I0(422)] ×[(1 / 4)×Σ(I(hkl) / I0(hkl)] ?1 However, I(422): Measured value of the X-ray diffraction peak intensity on the (422) plane I0(422): Average value of the standard X-ray diffraction peak intensity on the (422) plane of the crystal plane of TiCN described in ICDD card 00-042-1489 Σ(I(hkl) / I0(hkl)): Sum value of the values of ([Measured value of the X-ray diffraction peak intensity] / [Average value of the standard diffraction peak intensity of TiCN published in the ICDD card]) for each of the four planes of (111), (200), (420), and (422) is.

Advantages of the Invention

[0012] The surface-coated cutting tool according to the above embodiment has excellent chipping resistance.

Brief Description of the Drawings

[0013] [Figure 1] It is a schematic longitudinal sectional view of a surface-coated cutting tool according to an embodiment of the present invention. [Figure 2] It is a schematic diagram of a measurement line for measuring crack density.

Modes for Carrying Out the Invention

[0014] The inventor has intensively studied measures for having more excellent chipping resistance in a coated tool having an α-Al2O3 layer on the upper layer of the coating layer as described in the above-mentioned prior art documents. As a result, we found that, regarding cracks which are preferable to be absent in Patent Document 1, if they exist at a predetermined density in a cross section parallel to the substrate surface of the α-Al2O3 layer, the coated tool will exhibit excellent chipping resistance.

[0015] The following describes in detail an embodiment of the coating tool of the present invention. In this specification and in the claims, when a numerical range is expressed as "L~M" (where L and M are both numerical values), it is synonymous with "greater than or equal to L and less than or equal to M," and the range includes both an upper limit (M) and a lower limit (L). If a unit is specified only for the upper limit, the unit for the lower limit is also the same.

[0016] Figure 1 schematically shows a longitudinal cross-section of a coating tool according to one embodiment of the present invention (a cross-section perpendicular to the horizontal plane of the substrate surface, treating minute irregularities on the substrate surface as nonexistent). As is clear from Figure 1, the coating tool according to this embodiment has a lower layer (2) in contact with the surface of the substrate (1), an intermediate layer (3) in contact with the lower layer (2) on the tool surface side of the lower layer (2), and an upper layer (4) in contact with the intermediate layer (3) on the tool surface side of the intermediate layer (3). The lower layer (2), intermediate layer (3), and upper layer (4) constitute a coating layer (5). The following explains each layer in order.

[0017] 1. Lower layer The lower layer contains a composite nitride layer of Ti and Al or a composite carbonitride layer (sometimes called (TiAl)(CN)).

[0018] (1) Average thickness The average thickness of the lower layer is preferably 3.0 to 10.0 μm. This is because if the average thickness is less than 3.0 μm, it will not exhibit excellent wear resistance over long-term use, while if the average thickness exceeds 10.0 μm, abnormal damage such as chipping is more likely to occur during high-speed intermittent cutting. The average thickness of the lower layer is more preferably 5.0 to 8.0 μm.

[0019] (2) Content of NaCl-type face-centered cubic crystal grains The content of NaCl-type face-centered cubic crystal grains is preferably 80 area % or more in the longitudinal section. This is because if it is less than 80 area % the proportion of the original stable phase of (TiAl)(CN), which is a soft wurtzite-type hexagonal crystal structure, increases in the lower layer, and sufficient durability of the coating tool cannot be obtained. The proportion of crystal grains having the NaCl-type face-centered cubic structure is more preferably 90 area % or more, and may even be 100 area %.

[0020] (3) Average composition The average composition of the Ti and Al composite nitride layer or carbonitride layer is (Ti 1-Xavg Al Xavg )(C Yavg N 1-Yavg It is preferable that Xavg is (0.70 ≤ Xavg ≤ 0.90, 0.000 ≤ Yavg ≤ 0.050). The reason is that if Xavg is less than 0.70, the high oxidation resistance properties of (AlTi)CN cannot be sufficiently obtained, while if it is greater than 0.90, sufficient wear resistance cannot be obtained. It is more preferable that Xavg is between 0.75 and 0.85.

[0021] Furthermore, since the carbon (C) component in (AlTi)(CN) has the effect of improving hardness, it may also contain carbon (C). However, if Yavg exceeds 0.050, the chipping resistance decreases, so it is preferable to keep it between 0.000 and 0.050.

[0022] The atomic ratio of (AlTi) to (CN) is deposited to be 1:1, but it is acceptable if it is in the range of 1:0.8 to 1:1.2.

[0023] 2. Middle class The intermediate layer, which is in contact with the surface of the lower layer and is located on the tool surface side, includes a TiCN layer and acts as a layer that tightly adheres the lower and upper layers together.

[0024] (1) Average thickness The average thickness of the intermediate layer is preferably 1.5 to 5.0 μm. This is because if the average thickness is less than 1.5 μm, sufficient adhesion between the lower and upper layers cannot be ensured, and cracks present in the α-Al2O3 layer contained in the upper layer (described later) can further propagate into the intermediate layer, making chipping more likely to occur starting from cracks in the intermediate layer. On the other hand, if it exceeds 5.0 μm, the TiCN layer is prone to fracture and chipping during processing such as high-speed intermittent cutting. The average thickness of the intermediate layer is more preferably 2.5 to 4.0 μm.

[0025] (2) Composition The composition of the TiCN layer contained in the intermediate layer is not limited to stoichiometric composition.

[0026] (3) Orientation Index It is more preferable that the orientation index TC(422) of the TiCN layer contained in the intermediate layer is 2.0 or higher and 4.0 or lower. Here, TC(422)=[I(422) / I0(422)] ×[(1 / 4)×Σ(I(hkl) / I0(hkl)] ?1 however, I(422): Measured X-ray diffraction peak intensity on the (422) plane. I0(422): The average value of the standard X-ray diffraction peak intensity at the (422) plane of the TiCN crystal plane, as described on ICDD card 00-042-1489. Σ(I(hkl) / I0(hkl)): The sum of the values ​​of ([measured X-ray diffraction peak intensity] / [average standard diffraction peak intensity of TiCN listed on the ICDD card]) for each of the four faces (111), (200), (420), and (422). That is the case.

[0027] The reason why a TC(422) of 2.0 or higher is preferable is that if it is less than 2.0, cracks present in the α-Al2O3 layer contained in the upper layer (described later) may propagate further into the TiCN layer, making chipping more likely to occur starting from cracks in the TiCN layer. Note that the theoretical maximum value of TC(422) is 4.0.

[0028] 3. Upper layer The upper layer, which is in contact with the surface of the intermediate layer and is located on the tool surface side, contains an α-Al2O3 layer and acts as a layer that exhibits excellent high-temperature hardness and high-temperature oxidation resistance.

[0029] (1) Average thickness The average thickness of the upper layer is preferably 1.0 to 10.0 μm. This is because if it is less than 1.0 μm, it cannot exhibit excellent wear resistance over a long period of time, and furthermore, the crack density in the α-Al2O3 layer contained in the upper layer, which will be described later, tends to be low, making chipping more likely to occur during cutting. On the other hand, if it exceeds 10.0 μm, chipping tends to occur more likely during cutting. The average thickness of the upper layer is more preferably 3.0 to 8.0 μm.

[0030] (2) Composition The composition of the α-Al2O3 layer in the upper layer is not limited to its stoichiometric composition.

[0031] (3) Crack density The α-Al2O3 layer contained in the upper layer preferably has cracks in a cross section parallel to the substrate (a cross section parallel to the plane when the substrate surface is treated as a plane, excluding minute irregularities on the tool substrate surface), and the density of these cracks is preferably 0.4 to 6.5 cracks / mm. The reason why this range of crack density is preferable is that if it is less than 0.4 cracks / mm, the low crack density causes stress on the upper layer during cutting to concentrate locally, making chipping more likely. On the other hand, if it exceeds 6.5 cracks / mm, the high crack density makes chipping more likely during cutting. The crack density is more preferably 0.8 to 3.6 cracks / mm.

[0032] Crack density is measured as follows: The upper layer is polished until its thickness is approximately halved, obtaining a cross-section parallel to the substrate surface. Then, a 1 mm square field of view is observed in this cross-section using an optical microscope. Next, as shown in Figure 2, ten lines of at least 1 mm in length are drawn horizontally across the square observation area, at intervals that divide the vertical direction into 11 equal parts. These lines are designated as analysis lines, and the number of cracks intersecting each of the ten analysis lines is counted. The average value of these crack counts is then defined as the crack density.

[0033] (4) Orientation index TC(0 0 12) and the proportion of Σ3 to the total ΣN+1 It is more preferable that the orientation index TC(0 0 12) of the upper layer is 6.0 or higher and 7.0 or lower, and that the proportion of Σ3 in the total ΣN+1 of the α-Al2O3 layer is 40% or higher and 100% or lower. Here, TC(0 0 12)=[I(0 0 12) / I0(0 0 12)] ×[(1 / 7)×Σ(I(hkl) / I0(hkl)] ?1 however, I(0 0 12): Measured values ​​of X-ray diffraction peak intensity on the (0 0 12) plane. I0(0 0 12): The average value of the standard X-ray diffraction peak intensity at the (0 0 12) plane of the α-Al2O3 crystal plane as described in ICDD card 00-042-1468. Σ(I(hkl) / I0(hkl)): The sum of the values ​​of ([measured X-ray diffraction peak intensity] / [average value of standard diffraction peak intensity of Al2O3 listed on the ICDD card]) for each of the seven faces: (0 1 2), (1 0 4), (1 1 3), (1 1 6), (3 0 0), (2 1 4), and (0 0 12). That is the case.

[0034] If TC(0 0 12) is between 6.0 and 7.0 (7.0 being the theoretical upper limit), better wear resistance is obtained, and welding of the workpiece becomes less likely. Furthermore, if the proportion of Σ3 in the total ΣN+1 in the α-Al2O3 layer is 40% or more, better wear resistance is obtained, the grain boundary strength of the α-Al2O3 layer does not decrease, and the occurrence of chipping originating from cracks in the α-Al2O3 layer is more reliably suppressed. This proportion of Σ3 may also be 100%.

[0035] (5) Residual stress It is even more preferable that the residual stress of the α-Al2O3 layer be between 0 and +300 MPa. The reason why a residual stress in this range is even more preferable is that if it is less than 0 MPa (compressive residual stress exists), the adhesion strength between the α-Al2O3 layer and the TiCN layer decreases, making chipping more likely due to delamination of the α-Al2O3 layer. On the other hand, if it exceeds 300 MPa, chipping is more likely to occur starting from cracks in the α-Al2O3 layer.

[0036] (6) Atomic ratio of S (sulfur) In the α-Al2O3 layer, it is even more preferable that ρα = [S] / ([Al]+[O]+[S]) ([Q] represents the number of atoms of element Q) is between 0.00001 and 0.00050. This is because if ρα is less than 0.00001, the α-Al2O3 layer may not be able to follow the plastic deformation of the substrate, making it prone to abnormal damage such as chipping. On the other hand, if it exceeds 0.00050, the grain boundary strength of the α-Al2O3 layer decreases, making it easier for chipping to occur starting from cracks in the α-Al2O3 layer.

[0037] 4. Other layers Other layers can be broadly categorized into two types: layers that are intentionally created and layers that are not intentionally created (unintentional). These will be explained in order below.

[0038] 4-1. Layers that are intentionally created The following layers are intentionally created layers.

[0039] (1) Base layer An underlayer may be provided between the substrate and the lower layer. The underlayer may be one or more layers selected from a composite Ti and Al nitride layer or composite carbonitride layer, a Ti carbide layer, a nitride layer, a carbonitride layer, a carbon oxide layer, and a carbonitride layer, each having a different composition from the lower layer. The composition of these layers is not limited to stoichiometric compositions.

[0040] (2) Lower adhesion layer A lower adhesion layer may be provided between the lower layer and the intermediate layer. The lower adhesion layer may consist of one or more layers selected from among Ti carbide layers, nitride layers, and carbonitride layers. The composition of these layers is not limited to stoichiometric compositions.

[0041] (3) Upper adhesion layer An upper adhesion layer may be provided between the intermediate layer and the upper layer. The upper adhesion layer may consist of one or more layers selected from among Ti carbide layers, nitride layers, carbonitride layers, carbonoxide layers, and carbonitride layers. The composition of these layers is not limited to stoichiometric compositions.

[0042] 4-2. Unintended Layers When switching deposition gases, a small amount of layers different from the Ti and Al composite nitride or carbonitride layer as the lower layer, the TiCN layer as the intermediate layer, the α-Al2O3 layer as the upper layer, the underlayer, the lower adhesion layer, and the upper adhesion layer may be unintentionally produced.

[0043] 5.Base (1) Composition In this embodiment, the substrate may be, but is not limited to, a WC-based cemented carbide (containing Co in addition to WC, and also including those with added carbides or carbonitrides such as Ti, Ta, and Nb), a cermet (for example, one mainly composed of TiC, TiN, TiCN, etc.), a ceramic (for example, silicon nitride, sialon, aluminum oxide), or a cBN sintered body.

[0044] (2) Shape The shape of the base material is not particularly restricted as long as it is a shape that can be used as a cutting tool; examples include the shape of an insert and the shape of a drill.

[0045] 6. Measurement of average thickness The average thickness of each layer constituting the coating layer can be obtained, for example, by preparing a sample for observation of the longitudinal section of the coating layer at an arbitrary position using a focused ion beam system (FIB), a cross-section polisher (CP), etc., observing the longitudinal section at multiple locations (e.g., 5 locations) using a scanning electron microscope (SEM) or TEM, a scanning transmission electron microscope (STEM), or an energy dispersive X-ray spectrometer (EDX) attached to an SEM or TEM, determining the thickness, and averaging these values.

[0046] 7. Measurement of composition The atomic content in each layer was determined by using Auger electron spectroscopy (AES) on a sample whose cross-section had been polished. The electron beam was irradiated onto the longitudinal section, and five or more line analyses were performed in the thickness direction of the coating layer, with the measurement results being averaged.

[0047] 8. Measurement of the proportion of crystal grains in NaCl-type face-centered cubic structure The grain boundaries of the (TiAl)CN layer are determined and the grains are identified in the following manner. Specifically, using a crystal orientation analyzer attached to a transmission electron microscope (TEM), an electron beam tilted at, for example, 0.5 to 1.0 degrees relative to the normal direction of the polished surface is irradiated in a precessional manner on a polished longitudinal section. The electron beam is scanned at arbitrary beam diameters and intervals, and electron diffraction patterns are continuously acquired to analyze the crystal orientation of each measurement point. An example of the observation field is a width of 50 μm in the direction parallel to the substrate surface (lateral direction) and the thickness of the coating layer (average thickness) in the longitudinal direction.

[0048] The conditions used to acquire the electron diffraction pattern in this measurement were, for example, an acceleration voltage of 200 kV, a camera length of 20 cm, a beam size of 2.4 nm, and a measurement step of 5.0 nm. The measured crystal orientation was determined by discretely examining the measurement surface, and the orientation distribution of the entire measurement surface was obtained by representing the region up to the midpoint between adjacent measurement points with the measurement result. A regular hexagonal shape can be used as an example of the region represented by these measurement points (hereinafter sometimes referred to as a pixel).

[0049] If there is an angular difference of 5 degrees or more in crystal orientation between adjacent pixels, or if only one of adjacent pixels exhibits a face-centered cubic structure of the NaCl type or a hexagonal structure of the wurtzite type, the edges of the region where these pixels meet are defined as grain boundaries. The area enclosed by these grain boundary edges is defined as a single crystal grain. However, pixels that exist alone, such as those with an orientation difference of 5 degrees or more from all adjacent pixels, or those for which there are no adjacent measurement points exhibiting a face-centered cubic structure of the NaCl type, are not considered crystal grains. Only pixels that are connected in groups of two or more are treated as crystal grains. In this way, grain boundary determination is performed to identify the crystal grains.

[0050] Furthermore, by performing crystal orientation analysis, a covalent lattice point distribution graph of the constituent atoms is created for each of the α-Al2O3 layers, and the distribution ratio of Σ3 within the entire ΣN+1 is determined. The covalent lattice point distribution graph of constituent atoms is obtained by scanning an electron beam tilted at, for example, 0.5 to 1.0 degrees relative to the normal direction of the polished surface in a polished longitudinal section, while precessing the electron beam, using an arbitrary beam diameter and spacing. The inclination angle between the normals of the (0001) plane and the (10-10) plane, which are crystal planes of the crystal grains, is measured relative to the normal of the polished surface. Based on the obtained measured inclination angles, the covalent lattice point distribution graph of each constituent atom at the interface of mutually adjacent crystal grains is determined. The distribution of lattice points that share one constituent atom with each other (common constituent atom lattice points) is calculated, and when the common constituent atom lattice point configuration in which there are N lattice points that do not share a constituent atom with each other is represented as ΣN+1, the distribution ratio of each ΣN+1 in the whole ΣN+1 is calculated.

[0051] In the resulting shared lattice point distribution graph of the constituent atoms of the α-Al2O3 layer, the distribution ratio of Σ3 within the entire ΣN+1 (the sum of the distribution ratios of Σ3, Σ7, Σ11, Σ13, Σ17, Σ19, Σ21, Σ23, and Σ29 from the above results) is determined.

[0052] 10. Measurement of TC (hkl) It is not possible to obtain X-ray diffraction results for only the intermediate layer or only the upper layer; the X-ray diffraction results for the lower layer, intermediate layer, and upper layer are presented together (summarized). In other words, the X-ray diffraction results for the coating layer are shown.

[0053] The orientation index TC(0 0 12) of the α-Al2O3 layer can be calculated as follows. TC(0 0 12)=[I(0 0 12) / I0(0 0 12)] ×[(1 / 7)×Σ(I(hkl) / I0(hkl)] ?1 however, I(0 0 12): Measured X-ray diffraction peak intensity at the (0 0 12) plane of the α-Al2O3 layer. I0(0 0 12): The average value of the standard X-ray diffraction peak intensity at the (0 0 12) plane of the α-Al2O3 crystal plane as described in ICDD card 00-042-1468. Σ(I(hkl) / I0(hkl)): The sum of the values ​​of ([measured X-ray diffraction peak intensity] / [average value of standard diffraction peak intensity for Al2O3 listed on the ICDD card]) for each of the seven faces (0 1 2), (1 0 4), (1 1 3), (1 1 6), (3 0 0), (2 1 4), and (0 0 12) in the α-Al2O3 layer. That is the case.

[0054] The orientation index TC(422) of the TiCN layer is calculated as follows: TC(422)=[I(422) / I0(422)] ×[(1 / 4)×Σ(I(hkl) / I0(hkl)] ?1 however, I(422): Measured X-ray diffraction peak intensity at the (422) plane of the TiCN layer. I0(422): The average value of the standard X-ray diffraction peak intensity at the (422) plane of the TiCN crystal plane, as described on ICDD card 00-042-1489. Σ(I(hkl) / I0(hkl)): The sum of the values ​​of ([measured X-ray diffraction peak intensity] / [average value of standard diffraction peak intensity of TiCN listed on the ICDD card]) for each of the four faces (111), (200), (420), and (422) in the TiCN layer. That is the case.

[0055] Furthermore, the diffraction lines of the four faces (111), (200), (420), and (422) in the TiCN layer, and the diffraction lines of the seven faces (0 1 2), (1 0 4), (1 1 3), (1 1 6), (3 0 0), (2 1 4), and (0 0 12) in the α-Al2O3 layer, are observed to be separated from the peaks of the upper, intermediate, and lower layers when X-ray diffraction is performed on the coating layer, i.e., the upper layer, intermediate layer, and lower layer. Furthermore, X-ray diffraction is performed using Cu-Kα rays as the source, under the following conditions: measurement range (2θ): 15.0~135.0 degrees, scan step: 0.013 degrees, and measurement time per step: 0.48 sec / step.

[0056] The residual stress in the α-Al2O3 layer is measured using the sin2Ψ method with an X-ray diffractometer using Cu-Kα rays, under the following conditions: measurement range (2θ): 125.7~130.1 degrees, scan step: 0.013 degrees, and measurement time per step: 359.3 seconds / step. The measurement uses the diffraction peak of the (13_10) plane, and calculations are performed using a Young's modulus of 386 GPa and a Poisson's ratio of 0.27 (Source: B. Eigenmann, B. Scholtes, E. Macherauch, "Grundlagen und Anwendung der rontgenographischen Spannungsermittlung an Keramiken und Metall-Keramik-Verbundwerkstofften, Materialwissenschaft und Werkstofftechnik, vol.20, pp.314-325, 1989).

[0057] 14. Manufacturing method The coating layer of the coating tool of this embodiment can be manufactured by chemical vapor deposition under the following manufacturing conditions, for example.

[0058] In other words, by setting the proportion of HCl and H2S, which are the film-forming gases for the α-Al2O3 layer contained in the upper layer, to predetermined values, and setting the cooling rate of 400-800°C during the cooling process after film formation of all layers to predetermined values, the crack density in the α-Al2O3 layer can be controlled. The following are examples of film deposition conditions for each layer.

[0059] (1) Deposition of the lower layer ((TiAl)(CN) layer) Reaction gas composition (volume %): Gas group A: NH3: 0.1~0.8%, H2: 25.0~35.0% Gas group B: AlCl3: 0.02-0.09%, TiCl4: 0.01-0.03%, N2: 0.0-10.0%, C2H4: 0.0-0.5%, H2: residual Reaction atmosphere pressure: 4.0~5.0 kPa Reaction atmosphere temperature: 700~850℃ Supply cycle of gas group A and gas group B: 1-5 seconds Gas supply time per cycle: 0.15-0.25 seconds Phase difference between the supply of gas group A and the supply of gas group B: 0.10~0.20 seconds

[0060] (2) Formation of the intermediate layer (TiCN layer) Reaction gas composition (volume %): CH3CN: 0.5~1.0%, TiCl4: 1.5~5.0% N2: 8.0~25.0%, H2: remainder, Reaction atmosphere temperature: 800~900℃ Reaction atmosphere pressure: 4.0~10.0 kPa

[0061] (3) Formation of the upper layer (α-Al2O3 layer) <Initial nucleation conditions> Reaction gas composition (volume %): AlCl3: 1.0~5.0%, CO2: 0.5~2.0%, HCl: 0.3~3.0%, H2: residual Reaction atmosphere pressure: 4.0~10.0 kPa Reaction atmosphere temperature: 800~900℃

[0062] <Nucle growth conditions> Reaction gas composition (volume %): AlCl3: 1.0~5.0%, CO2: 3.0~7.0%, HCl: 0.3~3.0%, H2S: 1.0~2.0%, H2: residual Reaction atmosphere pressure: 4.0~10.0 kPa Reaction atmosphere temperature: 800~900℃

[0063] (4) Cooling process Cooling rate in the temperature range of 400-800°C: 0.9-1.6°C / min [Examples]

[0064] Next, we will describe some examples. Here, we will describe an example in which the method is applied to an insert cutting tool using a WC-based cemented carbide as the base material. However, the same applies when the aforementioned material is used as the base material, and also when applied to drills and end mills.

[0065] As raw material powders, WC powder, TiC powder, TaC powder, NbC powder, Cr3C2 powder, and Co powder were prepared and blended as shown in Table 1. After adding wax and mixing in acetone with a ball mill for 24 hours, the mixture was dried under reduced pressure and then press-molded into a compact of a predetermined shape at a pressure of 98 MPa. This compact was then vacuum-sintered at 1420°C for 1 hour in a vacuum of 5 Pa to produce substrates A to C made of WC-based cemented carbide with the ISO standard SEEN1203AFSN shape. Note that each raw material powder contained trace amounts of unavoidable impurities.

[0066] Next, the lower layer, intermediate layer, and upper layer were sequentially deposited on the surfaces of these substrates A to C according to the manufacturing conditions shown in Tables 2 to 4, respectively, to obtain the coated tools 1 to 8 of the examples shown in Table 5 (hereinafter, Examples 1 to 8).

[0067] On the other hand, for comparison, the lower layer, intermediate layer, and upper layer were sequentially deposited on the surfaces of substrates A to C according to the manufacturing conditions shown in Tables 2 to 4, respectively, to obtain comparative example coated tools 1 to 8 (hereinafter referred to as comparative examples 1 to 8) shown in Table 5.

[0068] [Table 1]

[0069] [Table 2]

[0070] [Table 3]

[0071] [Table 4]

[0072] [Table 5]

[0073] Next, for the coated tools 1-8 of the present invention and comparative coated tools 1-8, the various tool bases A-C (ISO standard SEEN1203AFSN shape) were clamped to the tip of an alloy steel cutter with a cutter diameter of 125 mm using a fixing jig, and the following dry high-speed face milling and center-cut cutting tests were performed on ductile cast iron, and the wear width of the flank surface of the cutting edge was measured. Table 7 shows the results of the cutting tests. Note that for comparative coated tools 1-8, the time until the end of cutting time was shown because they reached the end of their lifespan due to chipping.

[0074] Cutting tests: Dry high-speed face milling, center cut cutting tests Cutter diameter: 125mm Workpiece material: JIS FCD700 block material Cutting speed: 300m / min Cutting depth: 2.0mm Feed rate: 0.2mm / blade Cutting time: 12 minutes

[0075] [Table 6]

[0076] In Table 6, the cutting time (minutes) until the end of life for the comparative example refers to the cutting time (minutes) until the end of life due to chipping.

[0077] As is clear from Table 6, all of the examples had a long maximum processing time, which is the processing time until the cutting edge breaks, and exhibited excellent durability. [Explanation of Symbols]

[0078] 1. Matrix 2 Lower layer 3. Intermediate layer 4. Upper layer 5. Covering layer

Claims

1. A surface-coated cutting tool having a substrate and a coating layer on the surface of the substrate, (a) The coating layer has at least three layers: an upper layer, an intermediate layer, and a lower layer. (b) The upper layer has an average thickness of 1.0 to 10.0 μm, and is made of α-Al ２ O ３ Including layers, (c) the α-Al ２ O ３ Cracks are present in the layer in a cross-section parallel to the substrate, and the density of these cracks is 0.4 to 6.5 cracks / mm. (d) The intermediate layer has an average thickness of 1.5 to 5.0 μm and includes a TiCN layer. (e) The lower layer has an average thickness of 3.0 to 10.0 μm and includes a Ti and Al composite nitride layer or a composite carbonitride layer. (f) The Ti and Al composite nitride layer or composite carbonitride layer contains 80 to 100 area percent of NaCl-type face-centered cubic crystal grains in the longitudinal cross-section of the coating layer, and its average composition is (Ti １－Ｘａｖｇ Al Ｘａｖｇ ) (C Ｙａｖｇ N １－Ｙａｖｇ (0.70 ≤ Xavg ≤ 0.90, 0.000 ≤ Yavg ≤ 0.050) A surface-coated cutting tool characterized by the following features.

2. The above-mentioned α-Al ２ O ３ The orientation index TC(0 0 12) of the layer is 6.0 or more, and in the constituent atom shared lattice point graph, the above-mentioned α-Al ２ O ３ The distribution ratio of Σ3 in the whole ΣN+1 of the layer is 40% or more and 100% or less. Here, TC(0 0 12) = [I(0 0 12) / I0(0 0 12)] ×[(1 / 7)×Σ(I(hkl) / I0(hkl)] ?１ however, I(0 0 12): Measured X-ray diffraction peak intensity on the (0 0 12) plane. I0 (0 0 12): Al as described on ICDD card 00-042-1468 ２ O ３ The average value of the standard X-ray diffraction peak intensity at the (0 0 12) plane of the crystal plane. Σ(I(hkl) / I0(hkl)): (0 1 2), (1 0 4), (1 1 3), (1 1 6), (3 0 0), (2 1 4) and (0 0 12) ([X-ray diffraction peak intensity measurement] / [Listed on the ICDD card, Al ２ O ３ [Average value of standard diffraction peak intensity] (total value) The surface-coated cutting tool according to claim 1, characterized in that it is the same as described in claim 1.

3. The α-Al ２ O ３ The surface-coated cutting tool according to claim 1 or 2, characterized in that the layer has crystals with a residual stress of 0 to +300 MPa.

4. The α-Al ２ O ３ A surface-coated cutting tool according to claim 1 or 2, characterized in that in the layer, ρα = [S] / ([Al] + [O] + [S]) (where [Q] represents the number of atoms of element Q) is 0.00001 to 0.00050.

5. The orientation index TC(422) of the TiCN layer is 2.0 or greater. Here, TC(422) = [I(422) / I0(422)] ×[(1 / 8)×Σ(I(hkl) / I0(hkl)] ?１ however, I(422): Measured X-ray diffraction peak intensity on the (422) plane. I0(422): The average value of the standard X-ray diffraction peak intensity at the (422) plane of the TiCN crystal plane as described on ICDD card 00-042-1489. Σ(I(hkl) / I0(hkl)): The sum of the values ​​of ([measured X-ray diffraction peak intensity] / [average standard diffraction peak intensity of TiCN listed on the ICDD card]) for each of the eight faces (111), (200), (420), and (422). The surface-coated cutting tool according to claim 1, characterized in that it is the same as described in claim 1.

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