Coated cemented carbide and tool

Abstract

This coated cemented carbide comprises a base material that is made of cemented carbide and a diamond layer that is disposed directly on at least part of the base material, wherein: the cemented carbide contains tungsten carbide particles and cobalt; the base material includes an external region that has a gradient composition in which the cobalt content ratio increases from the interface with the diamond layer toward the inside of the base material, and an internal region which is further inside the base material than the external region; the cobalt content ratio in the internal region is not less than 2 mass%; and the percentage (T2 / T1)×100 of the standard deviation T2 μm of the thickness of the external region with respect to the average thickness T1 μm of the external region is not more than 30%.

Description

Coated cemented carbide and tools

[0001] The present disclosure relates to coated cemented carbides and tools.

[0002] Conventionally, coated cemented carbide, which comprises a substrate made of cemented carbide and a diamond layer disposed directly on at least a portion of the substrate, has been used as a material for cutting tools and the like (Patent Documents 1 to 3).

[0003] Japanese Patent Application Laid-Open No. 03-094062 International Publication No. 2004 / 031437 Japanese Patent Application Laid-Open No. 2011-038150

[0004] The coated cemented carbide of the present disclosure is a coated cemented carbide comprising a substrate made of cemented carbide and a diamond layer disposed directly on at least a portion of the substrate, wherein the cemented carbide contains tungsten carbide particles and cobalt, the substrate comprises an outer region having a gradient composition in which the cobalt content increases from the interface with the diamond layer toward the interior of the substrate, and an inner region located more inward of the substrate than the outer region, wherein the cobalt content in the inner region is 2 mass % or more, and the outer region has an average thickness T １ The standard deviation T of the thickness of the outer region in μm ２ Percentage of μm (T ２ / T １ ) x 100 is 30% or less.

[0005] Fig. 1 is a diagram schematically showing a cross section of a coated cemented carbide according to an embodiment of the present disclosure, Fig. 2 is an enlarged view of region II in Fig. 1, and Fig. 3 is a perspective view illustrating one embodiment of a tool.

[0006] [Problem to be Solved by the Present Disclosure] When a coated cemented carbide having a substrate made of cemented carbide and a diamond layer disposed directly on at least a portion of the substrate is used as a material for a tool such as a cutting tool, the resistance to peeling of the diamond layer from the substrate (i.e., "peeling resistance") may be insufficient. Therefore, when such a coated cemented carbide is used for a tool such as a cutting tool, the tool life may be insufficient.

[0007] Therefore, an object of the present disclosure is to provide a coated cemented carbide having excellent peeling resistance and a tool made of the coated cemented carbide.

[0008] Effect of the Present Disclosure According to the present disclosure, it is possible to provide a coated cemented carbide having excellent peeling resistance and a tool made of the coated cemented carbide.

[0009] [Explanation of embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and explained. (1) The coated cemented carbide of the present disclosure is a coated cemented carbide comprising a substrate made of cemented carbide and a diamond layer disposed directly on at least a portion of the substrate, wherein the cemented carbide contains tungsten carbide particles and cobalt, the substrate includes an outer region having a gradient composition in which the cobalt content increases from the interface with the diamond layer toward the inside of the substrate, and an inner region located more inward of the substrate than the outer region, the cobalt content in the inner region is 2 mass % or more, and the average thickness T of the outer region is 1000 . １ the standard deviation T of the thickness of the outer region, in μm ２ Percentage of μm (T ２ / T １ ) x 100 is 30% or less.

[0010] According to the present disclosure, it is possible to provide a coated cemented carbide having excellent peeling resistance and a tool made of the coated cemented carbide.

[0011] (2) In the above (1), the average thickness T of the outer region １ The thickness may be 1 μm or more and 5 μm or less. This makes it possible to provide a coated cemented carbide having better peeling resistance and a tool made of the coated cemented carbide.

[0012] (3) In the above (1) or (2), the average thickness of the diamond layer may be 3 μm or more and 28 μm or less, thereby providing a coated cemented carbide having superior peeling resistance and a tool made of the coated cemented carbide.

[0013] (4) In any of the above (1) to (3), in a cross section of the coated cemented carbide taken along the normal direction to the surface of the diamond layer, the substrate may have a recess having a depth of 1 μm or more at the interface between the substrate and the diamond layer, and the average width of the recess at a depth of 1 μm may be 1 μm or more and 3 μm or less. This makes it possible to provide a coated cemented carbide having superior peeling resistance and a tool made of the coated cemented carbide.

[0014] (5) In the above (4), in a rectangular field of view provided on the cross section, which includes the interface between the substrate and the diamond layer, and which has a length of 80 μm along the normal direction to the surface of the diamond layer and a length of 110 μm along the surface of the diamond layer, the number of first indentations whose width at a depth of 1 μm from the indentation exceeds 10 μm may be 1 or less. This makes it possible to provide a coated cemented carbide having superior peeling resistance and a tool made of the coated cemented carbide.

[0015] (6) In any one of the above (1) to (5), the content of the tungsten carbide particles in the cemented carbide may be 90% by mass or more and 98% by mass or less, thereby providing a coated cemented carbide having superior peeling resistance and a tool made of the coated cemented carbide.

[0016] (7) In any one of the above (1) to (6), the content of cobalt in the cemented carbide may be 2% by mass or more and 10% by mass or less, thereby providing a coated cemented carbide having better peeling resistance and a tool made of the coated cemented carbide.

[0017] (8) The tool of the present disclosure is made of the coated cemented carbide described in (1) to (7) above.

[0018] According to the present disclosure, a tool made of a coated cemented carbide having excellent peeling resistance can be provided.

[0019] [Details of the embodiment of the present disclosure] A specific example of a coated cemented carbide according to one embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") will be described below with reference to the drawings. In the drawings of the present disclosure, the same reference symbols represent the same or corresponding parts. Furthermore, dimensional relationships such as length, width, thickness, and depth have been changed as appropriate for clarity and simplification of the drawings, and do not necessarily represent actual dimensional relationships.

[0020] In the present disclosure, the notation in the form of "A to B" means the upper and lower limits of a range (i.e., A or more and B or less), and when no unit is specified for A and a unit is specified only for B, the units of A and B are the same.

[0021] 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.

[0022] [Embodiment 1: Coated Cemented Carbide] A coated cemented carbide according to an embodiment of the present disclosure will be described with reference to Figures 1 and 2. Figure 1 is a diagram schematically showing a cross section of a coated cemented carbide according to an embodiment of the present disclosure. Figure 2 is an enlarged view of region II in Figure 1. One embodiment of the present disclosure (hereinafter also referred to as "this embodiment") is a coated cemented carbide 3 comprising a substrate 1 made of cemented carbide and a diamond layer 2 disposed directly on at least a portion of the substrate 1, wherein the cemented carbide contains tungsten carbide particles and cobalt, the substrate 1 comprises an outer region R2 having a gradient composition in which the cobalt content increases from the interface with the diamond layer 2 toward the interior of the substrate 1, and an inner region R1 located more inward than the outer region R2, the cobalt content in the inner region R1 being 2 mass% or more, and the average thickness T of the outer region R2 １ The standard deviation T of the thickness of the outer region R2 in μm ２ Percentage of μm (T ２ / T １ ) x 100 is 30% or less.

[0023] According to the present disclosure, it is possible to provide a coated cemented carbide 3 having excellent peeling resistance and a tool made of the coated cemented carbide 3. The reason for this is presumed to be as follows.

[0024] In the coated cemented carbide 3 of this embodiment, the substrate 1 includes an outer region R2 having a gradient composition in which the cobalt content increases from the interface with the diamond layer 2 toward the inside of the substrate 1, and an inner region R1 that is closer to the inside of the substrate 1 than the outer region R2, and the cobalt content in the inner region R1 is 2 mass % or more, and the average thickness T １ The standard deviation T of the thickness of the outer region R2 in μm ２ Percentage of μm (T ２ / T １ ) × 100 is 30% or less. This allows the variation in thickness of the outer region R2 to be kept sufficiently low, thereby improving the adhesion between the substrate 1 and the diamond layer 2, and thereby improving the peeling resistance of the coated cemented carbide 3.

[0025] <<Substrate>> The coated cemented carbide 3 includes a substrate 1 made of a cemented carbide. The cemented carbide includes tungsten carbide particles and cobalt. The cemented carbide may further include nickel. The cemented carbide may further include other components as long as the effects of the present disclosure are not impaired. Examples of other components include carbides, nitrides, or carbonitrides containing at least one element selected from the group consisting of titanium (Ti), tantalum (Ta), niobium (Nb), zirconium (Zr), hafnium (Hf), and molybdenum (Mo), as well as inevitable impurities. Examples of inevitable impurities include iron (Fe), calcium (Ca), oxygen (O), and sulfur (S).

[0026] The content of tungsten carbide particles in the cemented carbide alloy may be 90% by mass or more and 98% by mass or less. This ensures a sufficient area of ​​the contact interface between the tungsten carbide particles, which have high adhesion, and the diamond particles in the diamond layer 2 described below, thereby further improving the peeling resistance of the coated cemented carbide alloy 3. The content of tungsten carbide particles in the cemented carbide alloy may be 91% by mass or more and 97% by mass or less, or 92% by mass or more and 96% by mass or less. The tungsten carbide particles include at least one of "pure WC particles (including WC containing no impurity elements and WC containing impurity elements below the detection limit)" and "WC particles containing impurity elements intentionally or unavoidably contained therein, as long as the effects of the present disclosure are not impaired." The impurity content of the tungsten carbide particles (when two or more elements constituting the impurities are present, the total content of these elements) is less than 0.1% by mass. The content of impurity elements in the tungsten carbide particles is measured by ICP optical emission spectroscopy (measuring device: "ICPS-8100" (trademark) manufactured by Shimadzu Corporation).

[0027] The cobalt content in the cemented carbide may be 2% by mass or more and 10% by mass or less, thereby suppressing the generation of graphite due to the presence of cobalt, and further improving the peeling resistance of the coated cemented carbide 3. The cobalt content in the cemented carbide may be 3% by mass or more and 9% by mass or less, or 4% by mass or more and 8% by mass or less.

[0028] The composition of the substrate 1 can be determined by determining the content of each component in the internal region R1 by ICP optical emission spectroscopy (measuring device: Shimadzu Corporation's "ICPS-8100" (trademark)), and calculating the average (arithmetic mean) of the content of each component in the internal region R1.

[0029] In the first embodiment, the average particle size of the tungsten carbide particles is not particularly limited. The average particle size of the tungsten carbide particles can be, for example, 0.5 μm or more and 3 μm or less. It has been confirmed that the coated cemented carbide 3 of the first embodiment can have excellent peeling resistance regardless of the average particle size of the tungsten carbide particles.

[0030] The average particle size of tungsten carbide particles can be determined by the following steps (A1) to (H1). (A1) An arbitrary position of the coated cemented carbide 3 is cut out to expose a cross section. The cross section is mirror-finished using a cross-section polisher (manufactured by JEOL Ltd.). (B1) The region of the substrate 1 on the mirror-finished surface of the coated cemented carbide 3 is analyzed using a scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) (apparatus: Carl Zeiss Gemini 450 (trademark)) to identify the elements contained in the substrate 1. (C1) The region of the substrate 1 on the mirror-finished surface of the coated cemented carbide 3 is photographed with a scanning electron microscope (SEM) to obtain a backscattered electron image. The photographed region of the image is set to the center of the region of the substrate 1 on the cross section of the coated cemented carbide 3, i.e., a position that does not include areas with properties clearly different from the bulk portion, such as the vicinity of the interface between the diamond layer 2 and the substrate 1 (a position where the entire photographed region is the bulk portion of the substrate 1). The observation magnification was 5000x. The measurement conditions were an acceleration voltage of 3 kV, a current value of 2 nA, and a working distance (WD) of 5 mm. (D1) The photographed region of (C1) above was analyzed using an energy dispersive X-ray analyzer (SEM-EDX) attached to an SEM to identify the distribution of the elements identified in (B1) above in the photographed region, and an element mapping image was obtained. (E1) The backscattered electron image obtained in (C1) above was imported into a computer and binarized using image analysis software (OpenCV, SciPy). The binarization process was performed so that only tungsten carbide particles were extracted from the tungsten carbide particles and binder phase in the backscattered electron image. The binarization threshold value varies depending on the contrast, and is therefore set for each image. (F1) By overlaying the element mapping image obtained in (D1) above with the binarized image obtained in (E1) above, the presence area of ​​tungsten carbide particles was identified on the binarized image. Specifically, the regions shown in white in the binarized image and containing tungsten (W) and carbon (C) in the element mapping image correspond to the regions containing tungsten carbide particles. (G1) A rectangular measurement field of view of 12.0 μm × 8.2 μm is set in the binarized image.Using the image analysis software, the outer edge of each tungsten carbide particle in the measurement field is identified, and the circle-equivalent diameter (Heywood diameter: diameter equivalent to a circle with an equal area) of each tungsten carbide particle is calculated. (H1) Based on all tungsten carbide particles in the measurement field, the circle-equivalent diameter D50 of the tungsten carbide particles is calculated.

[0031] It has been confirmed that as long as the same coated cemented carbide 3 is measured by the above method, there is no variation in the measurement results even if the measurement location is changed arbitrarily.

[0032] <Internal region and external region> The substrate 1 includes an external region R2 having a gradient composition in which the cobalt content increases from the interface with the diamond layer 2 towards the interior of the substrate 1, and an internal region R1 located closer to the interior of the substrate 1 than the external region R2. The cobalt content in the internal region R1 is 2 mass% or more. The substrate 1 may consist of the external region R2 and the internal region R1.

[0033] Average thickness T of the outer region R2 １ The standard deviation T of the thickness of the outer region R2 in μm ２ Percentage of μm (T ２ / T １ ) × 100 is 30% or less. This makes it possible to improve the peeling resistance of the coated cemented carbide 3. ２ / T １ ) × 100 may be 1% or more and 30% or less, 3% or more and 25% or less, or 5% or more and 20% or less.

[0034] Average thickness T of the outer region R2 １ The average thickness T of the outer region R2 may be 1 μm or more and 5 μm or less. This can further improve the peeling resistance of the coated cemented carbide 3. １ may be 1.5 μm or more and 4.5 μm or less, and the average thickness T １ may be 2 μm or more and 4 μm or less.

[0035] Standard deviation T of the thickness of the outer region R2 ２The standard deviation T of the thickness of the outer region R2 may be 0.2 μm or more and 1.5 μm or less. This can further improve the peeling resistance of the coated cemented carbide 3. ２ The μm may be 0.25 μm or more and 1.25 μm or less, or 0.3 μm or more and 1.0 μm or less.

[0036] Average thickness T of the outer region R2 １ μm and the standard deviation T of the thickness of the outer region R2 ２The thickness of μm can be determined by the following steps (A2) to (E2). (A2) A cross section is obtained by cutting the coated cemented carbide 3 along a plane perpendicular to the surface of the diamond layer 2, and the cross section is then polished. (B2) Using an electron microscope, two images are taken of a rectangular field of view measuring 25 μm long and 40 μm wide, so that the diamond layer 2 and the substrate 1 are included. (C2) EDX (energy dispersive X-ray spectroscopy) line analysis is performed. Line analysis is performed over a width of approximately 8 μm, extending from the center of the thickness of the diamond layer 2 to a portion of the substrate 1 where the binder phase has not been removed. The direction of line analysis is perpendicular to the interface between the diamond layer 2 and the substrate 1. The line analysis extends from the center beyond the outer region where voids are present, and ends at the internal region where no voids are observed. Measurements are performed at any five locations within one field of view. (D2) Numerical data on the concentration profiles of tungsten atoms (W) and cobalt atoms (Co) is obtained from the EDX line analysis in a CSV format, etc. (E2) Fitting is performed on the concentration profile. First, fitting is performed on the region where the concentrations of W and Co are constant using "y = const." (Step I). Let W: F(x) = a, Co: G(x) = b. Here, by confirming that the Co concentration in the fitting is 2 mass%, it is determined that the cobalt content in the internal region is 2 mass% or more. Next, fitting is performed on the region where the concentration gradient of W and Co exists using the linear function "y = ax + b" (Step II). The region to be fitted is set to a region that is centered at 50% of the constant value obtained by fitting in Step I and falls within a certain range (e.g., 50% ± 20% or 50% ± 30%) around it. Let W: H(x) = cx + d, Co: I(x) = ex + f. Next, the thickness of the external region R2 is calculated (Step III). The difference between the solution of H(x) = 0 (x coordinate where the W concentration rises) and the solution of G(x) = I(x) (x coordinate where the Co concentration starts to drop) is defined as the thickness of the outer region R2. Data is acquired at any 10 locations, and the average thickness and standard deviation of those thicknesses are calculated to obtain the average thickness T １ and standard deviation T ２ Identify.

[0037] As long as the same coated cemented carbide 3 is measured by the above method, it has been confirmed that there is no variation in the measurement results even if the measurement location is changed arbitrarily or the range of the fitting area in Step II is changed arbitrarily within the above range.

[0038] <Dentition of substrate> In a cross section of the coated cemented carbide 3 taken along the normal direction to the surface of the diamond layer 2, the substrate 1 has a dent of 1 μm or more in depth at the interface between the substrate 1 and the diamond layer 2, and the average width of the dent at a depth of 1 μm may be 1 μm or more and 3 μm or less. This suppresses the occurrence of local crack initiation points and provides an anchor effect due to the moderate unevenness, thereby further improving the peeling resistance of the coated cemented carbide 3. The average width of the dent at a depth of 1 μm may be 1.5 μm or more and 2.5 μm or less.

[0039] The average width of the recesses at a depth of 1 μm can be determined by the following steps (A3) to (D3). (A3) A cross section is obtained by cutting the coated cemented carbide 3 along a plane perpendicular to the surface of the diamond layer 2, and the cross section is polished. (B3) Using an electron microscope, two fields of view are imaged, each measuring 80 μm long and 110 μm wide, so that the diamond layer 2 and substrate 1 are included. The surface of the diamond layer 2 is imaged so that it is parallel to the edge of the image (FIG. 2). (C3) A line L1 is drawn between the two points on the WC grains closest to the surface of the diamond layer 2 in the field of view, and a parallel line L2 is drawn 1 μm away from this line L1 toward the substrate 1 (FIG. 2). (D3) Identify the regions of the diamond layer 2 that lie beyond the parallel line L2 on the substrate 1 side, measure the number of such regions and the length of the line segment on the parallel line L2 in each region (in other words, the width W1 of the recess at a depth of 1 μm from the recess), and calculate the average length of the line segment in a total of two fields of view to determine the average width of the recess (Figure 2).

[0040] It has been confirmed that as long as the same coated cemented carbide 3 is measured by the above method, there is no variation in the measurement results even if the measurement location is changed arbitrarily.

[0041] In a rectangular field of view provided on the cross section, which includes the interface between the substrate 1 and the diamond layer 2, and which has a length of 80 μm along the normal to the surface of the diamond layer 2 and a length of 110 μm along the surface of the diamond layer 2, the number of first indentations whose width at a depth of 1 μm exceeds 10 μm may be 1 or less. This ensures a contact area between the substrate 1 and the diamond layer 2 and ensures the anchor effect between the substrate 1 and the diamond layer 2, thereby further improving the peeling resistance of the coated cemented carbide 3. The number of first indentations may be 0 or more and 1 or less, 0 or more and 0.8 or less, or 0 or more and 0.6 or less.

[0042] The number of first dents can be determined by the following steps (A4) to (B4): (A4) Perform the above steps (A3) to (C3). (B4) Identify an area of ​​the diamond layer 2 located on the substrate 1 side beyond the parallel lines, and count the number of first dents in that area where the length of the line segment on the parallel line (in other words, the width of the dent at a depth of 1 μm from the dent) exceeds 10 μm. The number of first dents is determined by calculating the average value (arithmetic mean) of the two fields of view.

[0043] It has been confirmed that as long as the same coated cemented carbide 3 is measured by the above method, there is no variation in the measurement results even if the measurement location is changed arbitrarily.

[0044] <Diamond Layer> <Composition of Diamond Layer> The coated cemented carbide 3 includes a diamond layer 2 disposed directly on at least a portion of the substrate 1. Here, "directly on" is not limited to the surface side of the coated cemented carbide 3 (i.e., the upper surface side of the substrate 1) during use, but also encompasses the back side of the coated cemented carbide 3 (i.e., the lower surface side of the substrate 1) during use. The diamond layer 2 refers to a layer containing diamond. The diamond may be polycrystalline diamond. Here, polycrystalline diamond refers to diamond particles of approximately 10 nm to several μm firmly bonded together. The diamond layer 2 may contain graphite, amorphous carbon, silicon atoms (Si), inevitable impurities (e.g., copper atoms (Cu), iron atoms (Fe), nickel atoms (Ni)), etc., as components other than diamond, within a range that does not impair the effects of the present disclosure. The presence of components other than diamond in the diamond layer 2 can be identified by X-ray diffraction (XRD), Raman spectroscopy, secondary ion mass spectrometry (SIMS), etc.

[0045] The coated cemented carbide 3 comprises a diamond layer 2 disposed directly on at least a portion of the substrate 1. The average thickness of the diamond layer 2 may be 3 μm or more and 28 μm or less. This can alleviate local stress concentration when a load is applied to the diamond layer 2, thereby further improving the peeling resistance of the coated cemented carbide 3. The average thickness of the diamond layer 2 may be 4 μm or more and 27 μm or less, or 5 μm or more and 26 μm or less. The average thickness of the diamond layer 2 can be adjusted by appropriately changing the film formation time in the diamond layer formation step.

[0046] The average thickness of the diamond layer 2 can be determined, for example, by using a scanning electron microscope (SEM) to measure any five points on a cross-sectional sample parallel to the normal direction of the surface of the diamond layer 2 and calculating the average value of the thicknesses measured at the five points. For example, a focused ion beam device, a cross-section polisher device, etc. can be used to prepare the cross-sectional sample.

[0047] <<Uses of Coated Cemented Carbide>> The coated cemented carbide 3 of this embodiment can be used for tools (cutting tools, saw blades, wear-resistant parts, etc.), molds, etc. Examples of cutting tools include cutting tools for general-purpose machining. More specifically, cutting tools include drills, end mills, turning tools, indexable inserts, indexable cutting tips for drills, indexable cutting tips for end mills, indexable cutting tips for milling, indexable cutting tips for turning, metal saws, gear cutting tools, reamers, taps, etc.

[0048] [Embodiment 2: Manufacturing method of coated cemented carbide] The coated cemented carbide of this embodiment comprises, in this order, a step of preparing a substrate intermediate made of cemented carbide (hereinafter also referred to as the "substrate intermediate preparation step"), a step of performing a surface treatment on the surface of the substrate intermediate to obtain a substrate (hereinafter also referred to as the "surface treatment step"), and a step of forming a diamond layer on the substrate by chemical vapor deposition to obtain a coated cemented carbide (hereinafter also referred to as the "diamond layer formation step").

[0049] <Preparation Step> In the preparation step, an intermediate substrate made of a cemented carbide is prepared. The intermediate substrate made of a cemented carbide may be prepared by manufacturing using a conventionally known method, or may be prepared by purchasing a commercially available product.

[0050] <Surface Treatment Step> In the surface treatment step, a substrate is obtained by performing a surface treatment on the surface of the substrate intermediate made of cemented carbide. As the surface treatment, an etching treatment is performed. As the surface treatment, prior to the etching treatment, a "sandblasting treatment" in which alumina or silicon carbide particles are sprayed, a "lapping treatment" in which the surface roughness of the substrate intermediate is reduced, or both may be further performed.

[0051] In the sandblasting process, the particle size may be, for example, 5 μm or more and 40 μm or less. This allows the "number of first recesses" described in embodiment 1 to be adjusted to a desired range. In the sandblasting process, the blasting pressure may be 0.1 MPa or more and 0.4 MPa or less.

[0052] Specific examples of lapping include mechanical polishing and ion milling. Examples of mechanical polishing include the AERO LAP (registered trademark) mirror polishing device. The lapping time may be, for example, 1 minute or more and 4 minutes or less. This allows the "average recess width" described in embodiment 1 to be adjusted to a desired range.

[0053] The etching process is carried out by immersing the intermediate substrate in a mixed acid of sulfuric acid and nitric acid to dissolve a part of the surface of the intermediate substrate. The etching process is carried out while stirring the mixed acid. By these steps, the cobalt content in the outer region is adjusted to a desired range, and the average thickness T of the outer region directly below the diamond layer is reduced. １ The standard deviation T of the thickness of the outer region in μm ２ Percentage of μm (T ２ / T １ ) × 100 can be adjusted to a desired range. In the mixed acid, the concentration of sulfuric acid may be 10 mass % or more and 98 mass % or less, and the concentration of nitric acid may be 10 mass % or more and 70 mass % or less. In addition, the time for immersing the intermediate substrate in the mixed acid (in other words, the processing time of the etching treatment) may be 0.5 minutes or more and 60 minutes or less. By adjusting the time for immersing the intermediate substrate in the mixed acid within the above range, the average thickness T １ The stirring speed may be 100 rpm or more and 300 rpm or less.

[0054] <Diamond Layer Forming Step> In the diamond layer forming step, a diamond layer is formed on a substrate by chemical vapor deposition to obtain a coated cemented carbide. Specifically, first, a diamond seed crystal is applied to the surface of the substrate to perform a seeding treatment. At this time, the diamond seed crystal is dispersed in water at a concentration of 0.01 g / L or more, and the substrate is immersed in this diamond seed crystal aqueous solution.

[0055] The average particle size of the diamond seed crystals is preferably 0.005 μm or more and 0.5 μm or less. This results in an optimal diamond nucleation density, a lower average void area ratio of the diamond layer, and improved peeling resistance of the diamond layer. Here, "average particle size" refers to the median diameter (d50) in the volume-based particle size distribution (volume distribution). The particle size of each crystal grain used to calculate the average particle size of the diamond seed crystals is measured using a field emission scanning electron microscope (FE-SEM).

[0056] Next, a diamond layer is formed by CVD on the surface of the substrate on the side where the diamond seed crystal is attached, to obtain a coated cemented carbide. The CVD method may be a conventionally known CVD method, such as microwave plasma CVD, plasma jet CVD, or hot filament CVD.

[0057] For example, a diamond layer can be formed on the substrate by placing the substrate in a hot filament CVD apparatus, introducing methane gas and hydrogen gas into the apparatus in a volumetric ratio of 0.5:99.5 to 10:90, and maintaining the substrate temperature at 700°C or higher and 900°C or lower.

[0058] [Embodiment 3: Tool] A tool according to one embodiment of the present disclosure will be described with reference to Fig. 3. Fig. 3 is a perspective view illustrating one aspect of the tool. The tool 10 according to this embodiment is made of the coated cemented carbide described in embodiment 1.

[0059] According to the present disclosure, it is possible to provide a tool made of a coated cemented carbide having excellent peeling resistance, for the reasons described in the first embodiment.

[0060] An example of the tool 10 of the present disclosure is a cutting tool having a shape shown in FIG.

[0061] <<Method of Manufacturing Tool>> The method of manufacturing the tool 10 of the present disclosure can be carried out in the same manner as a conventionally known method, except that the coated cemented carbide described in the first embodiment is used.

[0062] The present embodiment will be described in more detail with reference to examples, although the present embodiment is not limited to these examples.

[0063] <<Preparation of Coated Cemented Carbide>> The coated cemented carbide samples 1 to 20 and 101 were prepared by carrying out the following steps in the following order.

[0064] <Preparation step> As a substrate intermediate made of cemented carbide, a turning insert was prepared, the material of which was WC—Co (cemented carbide) and the shape of which was tool model number SNGN 120408. The WC content and Co content in the WC—Co were adjusted to the contents [mass%] shown in Table 3.

[0065] <Surface Treatment Step> A substrate was obtained by performing a surface treatment on the surface of the turning cutting insert (substrate intermediate) under the conditions listed in Table 1. The sandblasting, lapping, and etching treatments were performed in this order. In Table 1, 0 rpm in the "Stirring Speed ​​[rpm]" column under "Etching Treatment" means that no stirring was performed during the etching treatment. When stirring was performed during the etching treatment, the stirring was performed using a magnetic stirrer. In the etching treatment, a mixed acid containing sulfuric acid and nitric acid in a volumetric ratio of 1:3 was used. When lapping was performed, the surface of the substrate intermediate was polished using a dry shot mirror polisher for the time listed in Table 1.

[0066] <Diamond layer formation process> First, a diamond seed crystal was seeded on the surface of the substrate. Next, a diamond layer was formed on the substrate by chemical vapor deposition under the conditions shown in Table 2 until the average thickness of the diamond layer reached the value shown in Table 3. The concentration of methane gas relative to hydrogen gas was 1% by volume.

[0067] According to the above procedure, coated cemented carbide samples 1 to 20 and 101 were produced.

[0068]

[0069]

[0070]

[0071] <Characteristics evaluation of coated cemented carbide> <Average thickness of outer region T １ and the standard deviation of the thickness of the outer region T ２ > For each sample of coated cemented carbide, the average thickness T of the outer region １ The results are shown in the "external region" column of Table 3 under "average thickness T １ The standard deviation T of the thickness of the outer region of each coated cemented carbide sample is shown in the "[μm]" column. ２ was determined by the method described in embodiment 1. The results are shown in the "External Region" column of Table 3, with the "Standard Deviation T ２ [μm]" column.

[0072] <Average width of dents> For each coated cemented carbide sample, the average width of the dents at a depth of 1 μm was determined by the method described in embodiment 1. The results obtained are shown in the "Average width of dents [μm]" column of Table 3.

[0073] <Number of First Indentations> For each coated cemented carbide sample, the number of first indentations having a width of more than 10 μm at a depth of 1 μm from the indentations was determined by the method described in embodiment 1. The results obtained are shown in the "Number of First Indentations" column in Table 3.

[0074] <Content of tungsten carbide particles and content of cobalt> For each of the coated cemented carbide samples, the content of tungsten carbide particles in the cemented carbide was determined by the method described in embodiment 1. The results are shown in the "WC particle content [mass %]" column of Table 3. Furthermore, for each of the coated cemented carbide samples, the content of cobalt in the cemented carbide was determined by the method described in embodiment 1. The results are shown in the "Co content [mass %]" column of Table 3.

[0075] <Cutting test> Using the coated cemented carbide according to each sample as a cutting tool, milling was carried out on the upper surface of the following workpiece under the following conditions. The milling was carried out until the diamond layer peeled off from the cutting tool, and the machined area until the peeling occurred was determined. The results obtained are shown in the "Cutting test" column of Table 3 under "Machine area [mm ２ ]" column. The larger the machining area, the better the peeling resistance. <Cutting conditions> Workpiece: A390 (aluminum alloy) Cutting speed Vc: 500 m / min Feed per tooth: 0.2 mm / rev Depth of cut: 0.5 mm Cutting fluid: Water-soluble coolant

[0076] The coated cemented carbide according to Samples 1 to 20 corresponds to Examples. The coated cemented carbide according to Sample 101 corresponds to Comparative Example. From the results in Table 3, it was found that the coated cemented carbide according to Samples 1 to 20 had superior peeling resistance compared to the coated cemented carbide according to Sample 101.

[0077] From the above, it was found that the coated cemented carbide according to Samples 1 to 20 had excellent peeling resistance.

[0078] Although the embodiments and examples of the present disclosure have been described above, it is originally intended that the configurations of the above-described embodiments and examples may be appropriately combined or modified in various ways.

[0079] 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 embodiments and examples described above, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims.

[0080] 1 base material, 2 diamond layer, 3 coated cemented carbide, R1 internal region, R2 external region, L1 straight line, L2 parallel line, W1 width, 10 tool, 1a rake face, 1b flank face, 1c cutting edge face

Claims

1. A coated cemented carbide comprising a substrate made of cemented carbide and a diamond layer disposed directly on at least a portion of the substrate, wherein the cemented carbide contains tungsten carbide particles and cobalt, the substrate comprises an outer region having a gradient composition in which the cobalt content increases from the interface with the diamond layer toward the interior of the substrate, and an inner region located closer to the interior of the substrate than the outer region, wherein the cobalt content in the inner region is 2 mass% or more, and the average thickness T of the outer region is １ the standard deviation T of the thickness of the outer region, in μm ２ Percentage of μm (T ２ / T １ ) × 100 is 30% or less.

2. The average thickness T of the outer region １ The coated cemented carbide according to claim 1, wherein the thickness is 1 μm or more and 5 μm or less.

3. The coated cemented carbide according to claim 1 or 2, wherein the average thickness of the diamond layer is 3 μm or more and 28 μm or less.

4. A coated cemented carbide according to any one of claims 1 to 3, wherein, in a cross section of the coated cemented carbide taken along the normal direction to the surface of the diamond layer, the substrate has a depression at the interface between the substrate and the diamond layer, the depression having a depth of 1 μm or more, and the average width of the depression at a depth of 1 μm from 1 μm to 3 μm.

5. The coated cemented carbide according to claim 4, wherein in a rectangular field of view provided on the cross section, which includes the interface between the substrate and the diamond layer, and which has a length of 80 μm along the normal direction to the surface of the diamond layer and a length of 110 μm along the surface of the diamond layer, the number of first indentations whose width at a depth of 1 μm from the indentation exceeds 10 μm is 1 or less.

6. A coated cemented carbide according to any one of claims 1 to 5, wherein the content of the tungsten carbide particles in the cemented carbide is 90% by mass or more and 98% by mass or less.

7. A coated cemented carbide according to any one of claims 1 to 6, wherein the cobalt content in the cemented carbide is 2 mass % or more and 10 mass % or less.

8. A tool made of the coated cemented carbide according to any one of claims 1 to 7.

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