Cutting tool

Abstract

Provided is a cutting tool comprising a base material and a coating film provided on the base material, wherein: the coating film includes an α-Al2O3 layer; the thickness of the α-Al2O3 layer is 3-20 μm; and in a rectangular measurement field of view provided in a cross-section of the coating film extending along a normal with respect to the surface of the coating film, said field of view having a length of 30 μm in a first direction extending along the surface of the coating film and being such that the length thereof in a second direction orthogonal to the first direction of the coating film includes the entire thickness of the α-Al2O3 layer extending along the second direction, the number of first Σ3-type crystal grain boundaries that are continuous from a virtual line L1 to a virtual line L2 and intersect a virtual line L3 is 5 or greater, the virtual line L1 being at a distance of 0.5 μm into the α-Al2O3 layer from a first interface positioned on the base-material side of the α-Al2O3 layer, the virtual line L2 being at a distance of 0.5 μm into the α-Al2O3 layer from a second interface positioned on the coating-film-surface side of the α-Al2O3 layer, and the virtual line L3 being equidistant from the virtual line L1 and the virtual line L2.

Description

cutting tools

[0001] The present disclosure relates to cutting tools.

[0002] Conventionally, cutting tools have been used in which a coating is formed on a substrate. ２ O ３ ") is used as a coating material due to its excellent mechanical properties (Patent Documents 1 and 2).

[0003] JP 2002-131058 A JP 2023-101044 A

[0004] The cutting tool of the present disclosure is a cutting tool including a substrate and a coating provided on the substrate, the coating being α-Al ２ O ３ layer, ２ O ３ The thickness of the layer is 3 μm or more and 20 μm or less, and the length of the layer in a first direction along the surface of the coating, which is provided on a cross section of the coating along a normal line to the surface of the coating, is 30 μm, and the length of the layer in a second direction perpendicular to the first direction is 30 μm. ２ O ３ In a rectangular measurement field including the entire thickness of the layer along the second direction, the number of first Σ3 type crystal grain boundaries that are continuous from the imaginary line L1 to the imaginary line L2 and intersect with the imaginary line L3 is 5 or more, and the imaginary line L1 is ２ O ３ The α-Al ２ O ３ The imaginary line L2 is a virtual line with a distance of 0.5 μm to the α-Al layer side. ２ O ３ the α-Al ２ O ３ The imaginary line L3 is an imaginary line that is 0.5 μm away from the layer side, and the imaginary line L1 is an imaginary line that is the same distance from the imaginary line L1 and the imaginary line L2.

[0005] Fig. 1 is a schematic diagram showing an example of a cross section of a cutting tool according to embodiment 1. Fig. 2 is a diagram illustrating a method for measuring the number of first Σ3 type crystal grain boundaries. Fig. 3 is a diagram illustrating the α-Al ２ O ３ 1 is an enlarged view of a region near the interface between a first layer and a second layer.

[0006] [Problem to be Solved by the Present Disclosure] In the techniques of Patent Documents 1 and 2, α-Al is easily removed by using a cutting tool. ２ O ３ Crater wear occurs, accompanied by particle shedding, and tool life tends to decrease.

[0007] Therefore, the present disclosure provides α-Al ２ O ３ An object of the present invention is to provide a cutting tool having a coating including a layer, the cutting tool having a long tool life.

[0008] [Advantages of the Present Disclosure] According to the present disclosure, α-Al ２ O ３ It is possible to provide a cutting tool with a coating including the layer, the cutting tool having an extended tool life.

[0009] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described. (1) A cutting tool of the present disclosure is a cutting tool including a substrate and a coating provided on the substrate, and the coating is an α-Al ２ O ３ layer, ２ O ３ The thickness of the layer is 3 μm or more and 20 μm or less, and the length of the layer in a first direction along the surface of the coating, which is provided on a cross section of the coating along a normal line to the surface of the coating, is 30 μm, and the length of the layer in a second direction perpendicular to the first direction is 30 μm. ２ O ３ In a rectangular measurement field including the entire thickness of the layer along the second direction, the number of first Σ3 type crystal grain boundaries that are continuous from the imaginary line L1 to the imaginary line L2 and intersect with the imaginary line L3 is 5 or more, and the imaginary line L1 is ２ O ３ The α-Al ２ O ３The imaginary line L2 is a virtual line with a distance of 0.5 μm to the α-Al layer side. ２ O ３ the α-Al ２ O ３ The imaginary line L3 is an imaginary line that is 0.5 μm away from the layer side, and the imaginary line L1 is an imaginary line that is the same distance from the imaginary line L1 and the imaginary line L2.

[0010] According to the present disclosure, α-Al ２ O ３ It is possible to provide a cutting tool with a coating including the layer, the cutting tool having an extended tool life.

[0011] (2) In the above (1), the number of the first Σ3 type crystal grain boundaries may be 100 or less. ２ O ３ α-Al generated by excessive particle refinement during use of cutting tools ２ O ３ Particle shedding is suppressed, and α-Al ２ O ３ The abrasion resistance of the layer is improved.

[0012] (3) In the above (1) or (2), the number of all grain boundaries that intersect with the virtual line L3 in the measurement field may be 20 or more. ２ O ３ The particle size is not coarsened, and α-Al ２ O ３ The abrasion resistance of the layer is improved.

[0013] (4) In any one of the above (1) to (3), the α-Al ２ O ３ The layer may have an orientation index TC(hkl) of 5 or more, TC(0 0 12). ２ O ３ The abrasion resistance of the layer is improved.

[0014] (5) In any one of the above (1) to (4), the coating is a film made of the substrate and the α-Al ２ O ３The coating may further include a first layer disposed between the first and second layers, the first layer being a TiCN layer, which improves the wear resistance and chipping resistance of the coating.

[0015] (6) In any one of the above (1) to (5), the coating is ２ O ３ The cutting tip further includes a second layer disposed on a main surface opposite to the main surface of the layer closest to the substrate, and the second layer may include at least one selected from the group consisting of a TiN layer, a TiCN layer, and a TiCNO layer. When the second layer is at least one of a TiN layer and a TiCN layer, it is easy to identify the corners of the cutting tip after use (identification of the used portion). When the second layer includes a TiCNO layer, α-Al ２ O ３ When a TiCN layer is disposed immediately above the α-Al layer, and a TiN layer or a TiCN layer is disposed immediately above the TiCN layer, ２ O ３ This improves the adhesion between the first layer and the second layer, and suppresses the progress of wear in the initial stage of cutting.

[0016] [Details of the Embodiments of the Present Disclosure] Specific examples of cutting tools according to the present disclosure will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference numerals 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.

[0017] In the present disclosure, the notation in the form of "A to B" means A or more and B or less, and 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.

[0018] In the present disclosure, when a compound or the like is represented by a chemical formula, unless the atomic ratio is particularly limited, it is intended to include any conventionally known atomic ratio, and should not necessarily be limited to only those within the stoichiometric range.

[0019] In the present disclosure, when one or more numerical values ​​are listed as the lower limit and the upper limit of a numerical range, the combination of any one numerical value listed as the lower limit and any one numerical value listed as the upper limit is also considered to be disclosed.

[0020] In this disclosure, "comprises," "includes," "has," and variations thereof are open-ended terms. Open-ended terms may or may not include additional elements in addition to the required elements. The term "consisting of" is closed-ended. However, even a configuration expressed in closed terms may include additional elements that are normally incidental impurities or unrelated to the subject technology.

[0021] To better understand this disclosure, first, α-Al ２ O ３ The structure of the α-Al layer will be explained. ２ O ３ α-Al contained in the layer ２ O ３ There are "grain boundaries" between the particles.

[0022] α-Al ２ O ３ The grain boundaries in the layer include CSL grain boundaries and general grain boundaries, which are Σ3 type grain boundaries, Σ7 type grain boundaries, Σ11 type grain boundaries, Σ17 type grain boundaries, Σ19 type grain boundaries, Σ21 type grain boundaries, Σ23 type grain boundaries, and Σ29 type grain boundaries.

[0023] The Σ3 type grain boundary is α-Al ２ O ３ Therefore, α-Al has the lowest grain boundary energy among the CSL grain boundaries. ２ O ３ The higher the proportion of Σ3 type grain boundaries in the total grain boundaries in the layer, the greater the α-Al ２ O ３ The mechanical properties of the layer, including its resistance to plastic deformation, are improved.

[0024] In both Patent Document 1 and Patent Document 2, α-Al ２ O ３ On the other hand, when the present inventors tried to cut chromium-molybdenum steel using the cutting tools described in Patent Documents 1 and 2, they found that α-Al ２ O ３It was confirmed that crater wear accompanied by particle shedding occurred, resulting in a shortened tool life. The present inventors investigated the reasons for this and obtained the following findings.

[0025] In Patent Document 1, α-Al ２ O ３ The proportion of Σ3 type grain boundaries is increased in the lower part of the layer near the substrate, but the α-Al ２ O ３ The proportion of Σ3 type grain boundaries is low in the upper part of the layer. ２ O ３ Particles tend to fall off and crater wear occurs.

[0026] In Patent Document 2, α-Al ２ O ３ The deposition of the α-Al layer is performed in two separate steps, the first step and the second step. Therefore, the Σ3 type grain boundaries in the region deposited in the first step are not continuous with the Σ3 type grain boundaries in the region deposited in the second step. ２ O ３ When a crack develops in the layer, α-Al ２ O ３ Particles tend to fall off and crater wear occurs.

[0027] As a result of extensive research based on the above findings, the present inventors have found that α-Al ２ O ３ It has been found that the tool life of a cutting tool can be improved by controlling the amount of Σ3 type grain boundaries in a layer as well as the morphology of the Σ3 type grain boundaries. The cutting tool of the present disclosure will be described below.

[0028] [Embodiment 1: Cutting Tool] A cutting tool according to one embodiment of the present disclosure (hereinafter also referred to as "this embodiment") will be described with reference to Fig. 1. The cutting tool of this embodiment includes a substrate 10 and a coating 15 provided on the substrate 10. The coating 15 is made of α-Al ２ O ３ Layer 11 includes α-Al ２ O ３The thickness of the layer 11 is 3 μm or more and 20 μm or less. The length of the layer 11 in a first direction along the surface P1 of the coating 15 is 30 μm, and the length of the layer 11 in a second direction perpendicular to the first direction is α-Al ２ O ３ In a rectangular measurement field of view R1 that includes the entire thickness of the layer 11 along the second direction, the number of first Σ3 type crystal grain boundaries that are continuous from the imaginary line L1 to the imaginary line L2 and intersect with the imaginary line L3 is 5 or more. ２ O ３ From the first interface S1 located on the substrate 10 side of the layer 11, α-Al ２ O ３ The imaginary line L2 is 0.5 μm away from the layer 11. ２ O ３ From the second interface S2 located on the surface P1 side of the coating 15 of the layer 11, α-Al ２ O ３ The imaginary line L3 is an imaginary line that is 0.5 μm away from the layer 11. The imaginary line L3 is an imaginary line that is the same distance from the imaginary line L1 and the imaginary line L2.

[0029] In FIG. ２ O ３ Since the first layer 12 is provided directly under the layer 11, ２ O ３ The interface between the layer 11 and the first layer 12 corresponds to the first interface S1. ２ O ３ The first layer 12 is not provided directly below the layer 11, and the α-Al ２ O ３ When the layer 11 is provided directly on the substrate 10, α-Al ２ O ３ The interface between the layer 11 and the substrate 10 corresponds to the first interface S1. ２ O ３ The first layer 12 is not provided directly below the layer 11, and the α-Al ２ O ３ When layer 11 is provided directly on another layer such as an intermediate layer, α-Al ２ O ３ The interface between the layer 11 and another layer corresponds to the first interface S1.

[0030] In FIG.２ O ３ Since the second layer 13 is provided directly on the layer 11, the α-Al ２ O ３ The interface between the layer 11 and the second layer 13 corresponds to the second interface S2. ２ O ３ The second layer 13 is not provided directly on the layer 11, and the α-Al ２ O ３ When the layer 11 is the outermost layer of the coating, α-Al ２ O ３ The surface of the layer 11 corresponds to the second interface S2.

[0031] The cutting tool of the present disclosure is an α-Al ２ O ３ The cutting tool of the present disclosure has a coating including a layer, and can have a long tool life. The reason for this is presumed to be as follows: In the measurement field of view R1, the number of first Σ3 type grain boundaries that are continuous from the imaginary line L1 to the imaginary line L2 and intersect with the imaginary line L3 is 5 or more. The first Σ3 type grain boundaries are composed of α-Al ２ O ３ Among the Σ3 type grain boundaries in the layer, α-Al ２ O ３ It is an index showing the amount of Σ3 type grain boundaries that continue from the region close to the substrate of the layer to the region close to the surface of the coating. ２ O ３ If there are many first Σ3 type grain boundaries in the layer, the α-Al ２ O ３ Particles are less likely to fall off, and crater wear is suppressed, thereby improving the tool life of the cutting tool of the present disclosure.

[0032] 1, the cutting tool 1 of this embodiment includes a substrate 10 and a coating 15 provided on the substrate 10. The coating 15 is made of α-Al ２ O ３The coating 15 includes a layer 11. The coating 15 may cover at least a portion of the portion of the substrate involved in cutting, or may cover the entire surface of the substrate. The portion of the substrate involved in cutting refers to an area of ​​the substrate surface that is within 1.5 mm of the cutting edge. It is within the scope of the present disclosure even if a portion of the substrate is not covered with this coating or if the coating configuration is partially different.

[0033] <Uses of Cutting Tool> The cutting tool of the present disclosure may be, for example, a drill, an end mill, an indexable cutting tip for a drill, an indexable cutting tip for an end mill, an indexable cutting tip for milling, an indexable cutting tip for turning, a metal saw, a gear cutting tool, a reamer, or a tap.

[0034] <Substrate> The substrate includes a rake face and a flank face, and any conventionally known substrate of this type can be used. The material of the substrate may be, for example, cemented carbide (for example, a WC-based cemented carbide such as a WC-Co-based cemented carbide, where the cemented carbide can contain carbonitrides of Ti, Ta, Nb, etc.), cermet (a material mainly composed of TiC, TiN, TiCN, etc.), high-speed steel, ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), a cubic boron nitride sintered body, or a diamond sintered body.

[0035] The substrate may be made of cemented carbide (particularly WC-based cemented carbide) or cermet (particularly TiCN-based cermet). Substrates made of cemented carbide or cermet have an excellent balance of hardness and strength at high temperatures and have excellent properties as substrates for cutting tools used in the above applications. When a WC-based cemented carbide is used as the substrate, its structure may contain free carbon and abnormal layers called η-phase or ε-phase.

[0036] The substrate may have a surface that has been modified. For example, in the case of a cemented carbide, a de-β layer may be formed on the surface, and in the case of a cermet, a surface-hardened layer may be formed. The substrate exhibits the desired effect even when its surface has been modified.

[0037] When the cutting tool is an indexable cutting insert, the substrate may or may not have a chip breaker. The shape of the cutting edge ridge can be any of a sharp edge (the ridge where the rake face and flank intersect), a honed edge (a sharp edge with a radius), a negative land (a chamfered edge), or a combination of a honed edge and a negative land.

[0038] <Coating> <Coating Structure> The coating is an α-Al film formed on a substrate. ２ O ３ The coating 15 includes an α-Al layer. ２ O ３ In this case, the α-Al layer may be formed directly on the substrate. ２ O ３ layer is provided, and α-Al ２ O ３ The principal surface of the layer opposite to the principal surface close to the substrate corresponds to the outermost surface of the coating.

[0039] As shown in FIG. 1, the coating 15 is made of a substrate 10 and an α-Al ２ O ３ It may further include a first layer 12 disposed between layer 11 .

[0040] As shown in FIG. 1, the coating 15 is made of α-Al ２ O ３ The layer 11 may further include a second layer 13 disposed on the major surface opposite to the major surface close to the substrate 10 .

[0041] As shown in FIG. 1, the coating 15 comprises a first layer and an α-Al ２ O ３ An intermediate layer (not shown) may be included between the layers.

[0042] <<Total Coating Thickness>> The total coating thickness may be 5 μm or more and 30 μm or less, 7 μm or more and 20 μm or less, or 10 μm or more and 15 μm or less. When the average thickness of the total coating is 5 μm or more, the abrasion resistance of the coating is improved. When the average thickness of the total coating is 30 μm or less, the peeling resistance of the coating is improved.

[0043] The total thickness of the coating is measured by obtaining a cross-sectional sample parallel to the normal direction of the surface of the substrate and observing the sample with a scanning transmission electron microscope (STEM). An example of a scanning transmission electron microscope is JEM-2100F (product name) manufactured by JEOL Ltd.

[0044] In this disclosure, "thickness" refers to an average thickness. The specific measurement method is as follows: A cutting tool is cut along a cross section parallel to the normal direction of the surface to obtain a sample with the cross section of the coating exposed. The sample is observed with a scanning transmission electron microscope (STEM). The observation magnification is 5000x. A rectangular measurement field of view of (30 μm in the direction parallel to the substrate surface) × (a distance including the entire thickness of the coating) is set in the STEM image, and the thickness width is measured at 10 points in the measurement field, and the average value is taken as the "thickness." The thickness of each layer described below is also measured in the same way.

[0045] <α-Al ２ O ３ layer>≪α-Al ２ O ３ Layer thickness≫ α-Al ２ O ３ The thickness of the layer may be 3 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 12 μm.

[0046] <α-Al ２ O ３ Layer configuration>> In this embodiment, α-Al ２ O ３ The layer is made of a plurality of α-Al ２ O ３ (aluminum oxide having an α-type crystal structure) particles. ２ O ３ The layer is made of a plurality of α-Al ２ O ３ It may consist of α-Al particles. ２ O ３ The layer may contain unavoidable impurities as long as the effects of this embodiment are not impaired. Examples of the unavoidable impurities include chlorine (Cl). ２ O ３The content of unavoidable impurities in the layer may be 3% by mass or less. ２ O ３ The content of unavoidable impurities in the layer is measured by secondary ion mass spectrometry (SIMS).

[0047] α-Al of this embodiment ２ O ３ The grain boundaries in the layer include CSL grain boundaries and general grain boundaries. The CSL grain boundaries consist of Σ3 type grain boundaries, Σ7 type grain boundaries, Σ11 type grain boundaries, Σ17 type grain boundaries, Σ19 type grain boundaries, Σ21 type grain boundaries, Σ23 type grain boundaries, and Σ29 type grain boundaries. The scope of the present disclosure does not deviate from the case where one or more grain boundaries other than the Σ3 type grain boundaries are not observed, as long as the effects of the present disclosure are not impaired.

[0048] <Σ3 type grain boundary> α-Al of this embodiment ２ O ３ In the layer, the number of first Σ3 type crystal grain boundaries in the measurement field of view R1 is 5 or more. From the viewpoint of improving crater wear resistance, the number of first Σ3 type crystal grain boundaries in the measurement field of view R1 may be 5 or more and 100 or less, 10 or more and 75 or less, or 20 or more and 50 or less.

[0049] The method for measuring the number of first Σ3 type crystal grain boundaries in the measurement field of view R1 will be described with reference to Figs. 2 and 3. Fig. 2 is a diagram for explaining the method for measuring the number of first Σ3 type crystal grain boundaries. Fig. 2 is a diagram for explaining the method for measuring the number of first Σ3 type crystal grain boundaries. Fig. 2 is a schematic diagram showing an example of a cross section of a coating. Fig. 3 is a diagram for explaining a method for setting the first interface. Fig. 3 shows the α-Al ２ O ３ The region near the interface between the first layer and the second layer is shown enlarged.

[0050] (A1) The cutting tool is cut with a diamond wire along the normal line of the rake face of the substrate, and α-Al ２ O ３ The cross section of the layer is exposed. The cutting position is set at a position where the surface of the cutting tool is smooth and includes the cutting edge of the cutting tool. The exposed cross section is subjected to ion milling using Ar ions to make the cross section mirror-finished. The ion milling conditions are as follows: the acceleration voltage is 6 kV; the irradiation angle is α-Al ２ O３ α-Al in the cross section of the layer ２ O ３ The angle was 0° from the direction of a line parallel to the thickness direction of the layer. The irradiation time was 6 hours.

[0051] (A2) The mirror-finished cross section is observed at 5000x magnification with a field emission scanning electron microscope (EF-SEM) to obtain a backscattered electron image (EBSD image). The SEM conditions are as follows: the normal to the cross section is tilted 70° relative to the incident beam; the analysis is performed at 15 kV; a pressure of 10 Pa is applied to avoid charging effects; a high current mode is used in conjunction with an aperture diameter of 60 μm or 120 μm; and the step is 0.1 μm / step.

[0052] (A3) Data processing is performed on the EBSD image to obtain a first image in which the Σ3 grain boundary is displayed distinctly from other grain boundaries in the EBSD image. Data processing is performed with and without noise filtering. Noise filtering and grain boundary character distribution are determined using commercially available software (trade name: "orientation Imaging Microscopy Ver. 6.2" manufactured by EDAX). Analysis of grain boundary character distribution is performed based on data available from Grimmer (H. Grimmer, R. Bonnet, Philosophical Magazine A 61 (1990), 493-509). The Brandon criterion (ΔΘ<Θ(Σ)−0.5, where Θ=15°) is used to allow for a tolerance of experimental values ​​from theoretical values ​​(D. Brandon Acta Metall. 14 (1966), 1479-1484).

[0053] (A4) In the first image, the length of the coating 15 in the first direction along the surface P1 is 30 μm, and the length of the coating 15 in the second direction perpendicular to the first direction is α-Al ２ O ３ A rectangular measurement field of view R1 is set to include the entire thickness of the layer 11 along the second direction.

[0054] (A5) In the first image, α-Al ２ O ３ From the first interface S1 located on the substrate 10 side of the layer 11, α-Al２ O ３ The imaginary line L1, α-Al, with a distance of 0.5 μm to the layer side ２ O ３ From the second interface S2 located on the surface P1 side of the coating 15 of the layer, ２ O ３ An imaginary line L2 is set at a distance of 0.5 μm toward the layer side, and an imaginary line L3 is set at the same distance from the imaginary line L1 and the imaginary line L2.

[0055] 3, the first interface S1 is regarded as a line S11 that passes through the valley bottom B of the first interface S1 and is the same distance from an imaginary line LB that is parallel to the main surface 10a of the substrate 10, and that passes through the peak T of the first interface S1 and is parallel to the main surface 10a of the substrate 10. When the actual second interface S2 is uneven, the second interface S2 is also regarded as a line S11 that passes through the valley bottom B of the second interface S2 and is the same distance from an imaginary line that is parallel to the main surface of the substrate, and that passes through the peak T of the second interface S2 and is parallel to the main surface of the substrate.

[0056] (A6) Within the measurement field of view R1, the number of first Σ3 type crystal grain boundaries that are continuous from the virtual line L1 to the virtual line L2 and intersect with the virtual line L3 is counted. Seven first Σ3 type crystal grain boundaries are observed within the measurement field of view R1 shown in FIG. 2. A specific counting method will be explained with reference to FIG. 3. In FIG. 3, the thick lines within the measurement field of view R1 indicate Σ3 type crystal grain boundaries.

[0057] The Σ3 type grain boundary a1 is continuous as one line from the imaginary line L1 to the imaginary line L2 and intersects with the imaginary line L3. In this case, the number of first Σ3 type grain boundaries intersecting with the imaginary line L3 is one.

[0058] The Σ3 type grain boundary a2 and the Σ3 type grain boundary a3 merge at a position closer to the substrate than the imaginary line L3 to form a single Σ3 type grain boundary, which intersects with the imaginary line L3 as a single boundary. In this case, the number of first Σ3 type grain boundaries intersecting with the imaginary line L3 is one.

[0059] The Σ3 type grain boundary a4 branches into two Σ3 type grain boundaries at a position closer to the surface of the coating than the imaginary line L3, and each of the two Σ3 type grain boundaries continues to the imaginary line L2. In this case, the number of first Σ3 type grain boundaries intersecting with the imaginary line L3 is one.

[0060] The Σ3 type grain boundary a5 branches into two Σ3 type grain boundaries at a position closer to the substrate than the imaginary line L3, and each of the two Σ3 type grain boundaries continues to the imaginary line L2. In this case, the number of first Σ3 type grain boundaries intersecting with the imaginary line L3 is two.

[0061] The Σ3 type grain boundary a6 and the Σ3 type grain boundary a7 merge at a position closer to the surface of the coating than the imaginary line L3 to form a single Σ3 type grain boundary, which intersects with the imaginary line L3 as a single boundary. In this case, the number of first Σ3 type grain boundaries intersecting with the imaginary line L3 is two.

[0062] (A7) The number of the first Σ3 type crystal grain boundaries is measured in three mutually non-overlapping measurement visual fields R1. The average of the numbers of the first Σ3 type crystal grain boundaries in the three measurement visual fields R1 is calculated. In the present disclosure, this average corresponds to the number of the first Σ3 type crystal grain boundaries in the measurement visual field.

[0063] It was confirmed that similar results could be obtained even when the above measurements were performed on the same sample by arbitrarily setting multiple measurement fields.

[0064] α-Al of this embodiment ２ O ３ In the above measurement field of view provided in the layer, the number of all crystal grain boundaries that intersect with the virtual line L3 may be 20 or more, 20 to 150, 40 to 150, or 50 to 100.

[0065] The method for measuring the number of all grain boundaries that intersect with the virtual line L3 in the measurement field of view is described below. An EBSD image is obtained using the same methods as (A1) and (A2) of the method for measuring the number of first Σ3 type grain boundaries in the measurement field of view R1. Data processing is performed on the EBSD image to obtain a second image in which all grain boundaries are displayed in the SEM image. The measurement field of view R1 and the virtual line L3 are set in the second image using the same methods as (A4) and (A5) above. The number of all grain boundaries that intersect with the virtual line L3 in the measurement field of view R1 is measured. This measurement is performed for three measurement fields of view R1 that do not overlap with each other. The average of the numbers of grain boundaries in the three measurement fields of view R1 is calculated. In the present disclosure, this average corresponds to the number of all grain boundaries that intersect with the virtual line L3 in the measurement field of view.

[0066] It was confirmed that similar results could be obtained even when the above measurements were performed on the same sample by arbitrarily setting multiple measurement fields.

[0067] <Orientation Index> α-Al of this embodiment ２ O ３ The layer may have an orientation index TC(hkl) of 5 or more, TC(0 0 12) of 5 or more, 5 or more and 8 or less, or 7 or more and 8 or less. The orientation index TC(hkl) is expressed by the following formula (1).

[0068]

[0069] In the formula (1), I(hkl) represents the X-ray diffraction intensity of the (hkl) reflection plane, and I ０ (hkl) indicates the standard intensity according to ICDD PDF card number 00-010-0173. Furthermore, n in formula (1) indicates the number of reflections used in the calculation, which is 8 in this embodiment. The (hkl) planes used for reflection are (012), (104), (110), (0 0 12), (113), (024), (116), and (300).

[0070] ICDD (registered trademark) is an abbreviation for International Centre for Diffraction Data, and PDF (registered trademark) is an abbreviation for Powder Diffraction File.

[0071] The above-described measurement of TC(hkl) is possible by analysis using an X-ray diffraction apparatus. TC(hkl) can be measured under the following conditions, for example, using a SmartLb / a (registered trademark) manufactured by Rigaku Corporation (scan speed: 21.7° / min, step: 0.01°, scan range: 15 to 140°). In this embodiment, the measurement results of TC(hkl) using an X-ray diffraction apparatus are referred to as "XRD results."

[0072] Characteristic X-rays: Cu-Kα Tube voltage: 45 kV Tube current: 200 mA Filter: Multilayer mirror Optical system: Focusing method X-ray diffraction method: θ-2θ method When using an X-ray diffraction device, X-rays are irradiated onto the flank of the cutting tool. Normally, unevenness is formed on the rake face, whereas the flank is flat. Therefore, it is preferable to irradiate the X-ray onto the flank in order to eliminate disturbance factors. In particular, X-rays are irradiated onto a portion of the flank extending over a range of approximately 2 to 4 mm from the cutting edge ridge. This increases the reproducibility of the results. In this embodiment, α-Al on the flank of the substrate is irradiated. ２ O ３ The value of TC(hkl) of the layer is the α-Al ２ O ３ It is the same as the value of TC(hkl) of the layer.

[0073] It was confirmed that similar results could be obtained even when the above measurements were performed on the same sample by arbitrarily setting multiple measurement fields.

[0074] <First Layer> The coating 15 of this embodiment is a first layer made of a substrate 10 and an α-Al ２ O ３ The first layer 12 may be disposed between the layer 11 and the substrate 10. The first layer 12 corresponds to an underlayer. The first layer 12 may be disposed directly on the substrate 10. ２ O ３ The layer 11 may be provided directly on the first layer 12. The first layer 12 may be a TiCN layer or a TiN layer, or may be a TiCN layer.

[0075] The first layer may have an average thickness of 0.1 μm or more and 20 μm or less, which further improves the wear resistance and chipping resistance of the coating.

[0076] <Second Layer> The coating 15 of this embodiment is made of α-Al ２ O ３ The coating may further include a second layer 13 disposed on the main surface of the layer 11 opposite the main surface closest to the substrate 10. The second layer corresponds to a surface layer. The main surface of the second layer opposite the main surface closest to the substrate corresponds to the outermost surface of the coating. The second layer may be a TiN layer, a TiCN layer, or a TiCNO layer.

[0077] The second layer may have an average thickness of 0.05 μm or more and 1 μm or less, which improves the adhesion between the second layer and the adjacent layer.

[0078] <Intermediate layer> The coating 15 is made of the first layer and α-Al ２ O ３ The first layer may include an intermediate layer (not shown) disposed between the first layer and the α-Al layer. ２ O ３ The intermediate layer may be in contact with a TiCN layer or a TiCNO layer. The TiCN layer and the TiCNO layer have excellent abrasion resistance, and therefore can impart suitable abrasion resistance to the coating. The average thickness of the intermediate layer may be 1 μm or more and 20 μm or less.

[0079] <Method for Manufacturing Cutting Tool> The cutting tool of this embodiment can be manufactured by forming a coating on a substrate by chemical vapor deposition (CVD). ２ O ３ The layer can be formed, for example, by the following method. ２ O ３ The layers other than the layer can be formed under conventionally known conditions.

[0080] α-Al ２ O ３ The layer forming process includes a first step and a second step. ２ O ３ The conditions throughout the layer formation process are a temperature of 1000° C. and a pressure of 70 hPa. The gas flow rate (total gas flow rate) in the first process is 70 to 90 L / min, and the gas flow rate (total gas flow rate) in the second process is 100 to 130 L / min.

[0081] As a raw material gas, AlCl ３ , HCl, CO ２ , CO, H ２ S and H ２ From the start of film formation, the formed α-Al ２ O ３ The compounding ratio of the source gases is changed depending on the thickness of the layer. Specifically, it is set as follows:

[0082] The first step is from the start of film formation to α-Al ２ O ３ This is a process for forming a region in which the layer thickness is up to 1.5 μm. In the first process, the raw material gas is mixed with AlCl ３ : 1.3 to 1.7 vol%, HCl: 1.8 to 2.2 vol%, CO ２ : 1.3 to 1.7 vol%, CO: 2.2 to 2.8 vol%, and H ２ : The remaining volume % when the entire raw material gas is taken as 100 volume %. The blending amount of CO in the raw material gas of 2.2 to 2.8 volume % is ２ O ３ It is larger than the amount of CO contained in the source gas used to form the layer (for example, 0 to 1% by volume).

[0083] The second step is α-Al ２ O ３ In the second step, the raw material gas is mixed with AlCl ３ : 0.8 to 1.2 vol%, HCl: 0.5 to 4.0 vol%, CO ２ : 3.5 to 4.0 vol%, CO: 1.0 to 5.5 vol%, H ２ S: 0.5 to 0.7 volume %, and H ２ : The remaining volume % when the entire source gas is taken as 100 volume %. In the second step, the film formation temperature is set high at 1000°C, and CO, HCl, CO ２ and H ２ By controlling the blending ratio of S within the above range, the amount of Σ3 grain boundaries is increased, and α-Al ２ O ３ This prevents particles from becoming coarse.

[0084] When transitioning from the first process to the second process, α-Al ２ O ３ When the layer thickness reaches 1.5 μm, the total gas flow rate is gradually increased over 240 seconds. ２ O ３ layer, and α-Al formed in the second step. ２ O ３ Between the layers, Σ3 grain boundaries are likely to be formed continuously.

[0085] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0086] <Preparation of substrate> A substrate was prepared. The raw material powders of the substrate (TaC powder: 2.0 mass%, NbC powder: 1.0 mass%, Co powder: 10.0 mass%, WC: remainder) were uniformly mixed, press-molded into a predetermined shape, and then sintered at 1300 to 1500 °C for 1 to 2 hours to obtain a substrate made of cemented carbide (shape: model number CNMG120408N-UX (manufactured by Sumitomo Electric Hardmetal)). "WC: remainder" indicates that WC accounts for the remainder of the compounded composition (mass %).

[0087] <Formation of Coating> A coating was formed on the surface of the substrate obtained above to produce a cutting tool. Specifically, the substrate was set in a CVD apparatus, and a coating was formed on the substrate by CVD.

[0088] <<Formation of First Layer>> For samples in which "TiCN" is listed in the "Composition" column of "First Layer" in Table 3, a TiCN layer was formed on the substrate. The thickness of the first layer is as shown in Table 3. The conditions for forming the TiCN layer are as follows: Raw material gas composition: TiCl ４ : 8.5 vol%, CH ３ CN: 0.5 vol%, CO: 1.65 vol%, N ２ : 10.0 vol%, HCl: 2.0 vol%, H ２ : Remaining volume % when the entire raw material gas is 100% by volume Raw material gas flow rate: 120 L / min Pressure: 70 hPa Temperature: 850°C

[0089] <α-Al ２ O ３ Next, α-Al is formed directly on the first layer or on the substrate. ２ O ３ A layer of α-Al was formed. ２ O ３ The layer forming process includes a first step and a second step.

[0090] The first step is from the start of film formation to α-Al ２ O ３This is a process for forming a region in which the layer thickness is up to 1.5 μm. The film formation conditions (pressure, temperature, total gas flow rate) and source gas composition in the first process are as shown in Table 1.

[0091] The second step is α-Al ２ O ３ This is a process for forming a region in which the layer thickness exceeds 1.5 μm. The film formation conditions (pressure, temperature, total gas flow rate) and source gas composition in the second process are as shown in Table 2. α-Al formed in the second process ２ O ３ When the layer thickness reached the thickness shown in the "Thickness" column of Table 2, the second step was completed.

[0092] In the samples marked with "Yes" in the "Transition step" column of Table 1, α-Al ２ O ３ When the layer thickness reached 1.5 μm, the total gas flow rate was gradually changed over 240 seconds. For samples with "None" in the "Transition Step" column in Table 1, the gas flow rate was switched without any particular control.

[0093] <<Formation of Second Layer>> Next, in the samples in which “TiN, TiCN” is listed in the “Composition” column of “Second Layer” in Table 3, α-Al ２ O ３ A TiN layer and a TiCN layer were formed directly on the layer in the above order. The thicknesses of each layer are as shown in Table 3. The conditions for forming the TiN layer and the TiCN layer are as follows:

[0094] Conditions for forming the TiN layer: Raw material gas composition: TiCl ４ : 4.0 vol%, N ２ : 42.5% by volume, H ２ : Remaining volume % when the entire raw material gas is 100 volume % Raw material gas flow rate: 80 L / min Pressure: 70 hPa Temperature: 1000°C

[0095] Conditions for forming the TiCN layer: Raw material gas composition: TiCl ４ : 8.5 vol%, CH ３ CN: 0.5 vol%, CO: 1.65 vol%, N ２ : 10.0 vol%, HCl: 2.0 vol%, H ２: Remaining volume % when the entire raw material gas is 100 volume % Raw material gas flow rate: 120 L / min Pressure: 90 hPa Temperature: 1000°C

[0096] Through the above steps, each sample cutting tool was obtained.

[0097]

[0098]

[0099]

[0100] [Evaluation] <Number of first Σ3 type crystal grain boundaries> α-Al of cutting tool of each sample ２ O ３ In the layer, the number of first Σ3 type grain boundaries in the measurement field of view described in embodiment 1 was measured. The specific measurement method is as described in embodiment 1. The results are shown in the "Number of first Σ3 type grain boundaries" column in Table 3.

[0101] <Number of all grain boundaries intersecting with the virtual line L3> α-Al of the cutting tool of each sample ２ O ３ In the layer, the number of all grain boundaries intersecting with the virtual line L3 in the measurement field of view described in embodiment 1 was measured. The specific measurement method is as described in embodiment 1. The results are shown in the "Total number of grain boundaries" column in Table 3.

[0102] <Orientation index TC (0 0 12)> α-Al of each sample cutting tool ２ O ３ The orientation index TC (0 0 12) of the layer was measured. The specific measurement method is as described in embodiment 1. The results are shown in Table 3.

[0103] <Cutting test> Using each sample cutting tool, a cutting test was carried out under the following conditions: The exposed area of ​​the substrate on the rake face (mm ２ ) was measured. ２ The time when this time was exceeded was defined as the tool life. The results are shown in Table 3. A longer tool life indicates better crater wear resistance of the cutting tool.

[0104] <Cutting conditions> Workpiece: SCM415 Processing: Round bar external diameter turning Cutting speed: 500 m / min Feed rate: 0.2 mm / rev Depth of cut: 2.0 mm Cutting fluid: Water-soluble cutting oil

[0105] <Discussion> The cutting tools of Samples 1 to 12 correspond to Examples. The cutting tools of Samples 1-1 to 1-3 correspond to Comparative Examples. It was confirmed that the cutting tools of Samples 1 to 12 had longer tool life than the cutting tools of Samples 1-1 to 1-3.

[0106] α-Al of Sample 1-1 ２ O ３ In the layer, the proportion of Σ3 type grain boundaries is high in the lower part near the substrate, but ２ O ３ In the upper part of the layer, the proportion of Σ3 type grain boundaries was low, and the number of first Σ3 type grain boundaries was small. ２ O ３ Particles were easily shed and crater wear was easily caused.

[0107] α-Al of Sample 1-2 ２ O ３ In the Al layer, the Σ3 type grain boundaries in the region formed in the first step were not continuous with the Σ3 type grain boundaries in the region formed in the second step, and the number of first Σ3 type grain boundaries was small. ２ O ３ As the cracks grow in the layer, the α-Al ２ O ３ Particles were easily shed and crater wear was easily caused.

[0108] α-Al of Sample 1-3 ２ O ３ In the layer, the proportion of Σ3 type grain boundaries was low in the entire region, and the number of first Σ3 type grain boundaries was small. ２ O ３ As the cracks grow in the layer, the α-Al ２ O ３ Particles were easily shed and crater wear was easily caused.

[0109] Although the embodiments and examples of the present disclosure have been described above, it is intended from the beginning that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways. The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments and examples, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0110] 10 Base material, 10a Main surface, 11 α-Al ２ O ３ layer, 12 first layer, 13 second layer, 15 coating, S1 first interface, S2 second interface, R1 measurement field, a1, a2, a3, a4, a5, a6, a7 Σ3 type grain boundary.

Claims

1. A cutting tool comprising a substrate and a coating provided on the substrate, wherein the coating is α-Al ２ O ３ the α-Al layer; ２ O ３ The thickness of the layer is 3 μm or more and 20 μm or less, and the length of the layer in a first direction along the surface of the coating, which is provided on a cross section of the coating along a normal line to the surface of the coating, is 30 μm, and the length of the layer in a second direction perpendicular to the first direction is 30 μm. ２ O ３ In a rectangular measurement field of view that includes the entire thickness of the layer along the second direction, the number of first Σ3 type crystal boundaries that are continuous from the imaginary line L1 to the imaginary line L2 and intersect with the imaginary line L3 is 5 or more, and the imaginary line L1 is ２ O ３ The α-Al ２ O ３ The imaginary line L2 is a line extending from the α-Al layer to the α-Al layer. ２ O ３ the α-Al ２ O ３ a virtual line L3 having a distance of 0.5 μm toward a layer side, and the virtual line L3 being a virtual line having the same distance from the virtual line L1 and the virtual line L2.

2. The cutting tool according to claim 1, wherein the number of the first Σ3 type grain boundaries is 100 or less.

3. A cutting tool according to claim 1 or 2, wherein the number of all grain boundaries that intersect with said imaginary line L3 in said measurement field of view is 20 or more.

4. The α-Al ２ O ３ The cutting tool according to claim 1 , wherein the layer has an orientation index TC(hkl) of TC(0 0 12) of 5 or more.

5. The coating is made of the substrate and the α-Al ２ O ３ The cutting tool of claim 1 , further comprising a first layer disposed between the first and second layers, the first layer being a TiCN layer.

6. The coating is the α-Al ２ O ３ 6. The cutting tool according to claim 1, further comprising a second layer disposed on a main surface of the layer opposite to the main surface close to the substrate, the second layer comprising at least one layer selected from the group consisting of a TiN layer, a TiCN layer, and a TiCNO layer.

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