Coated cutting tools and cutting tools

Abstract

The coated cutting tool of the present invention has a substrate and a coating. The substrate is formed of cemented carbide or cermet. The coating is located on the substrate. Further, when measuring the hardness by pressing a indenter into the coating to a depth of 20% while changing the indentation load of the indenter from the surface of the coating, taking the minimum hardness among the hardness values as the first hardness, the maximum hardness as the second hardness, the depth of the first hardness as the first hardness depth, and the depth of the second hardness as the second hardness depth, the second hardness depth is shallower than the first hardness depth, and the difference between the first hardness and the second hardness is greater than 7 GPa.

Description

Technical Field

[0001] The present invention relates to coated cutting tools and cutting tools. Background Art

[0002] As a tool used in cutting processes such as turning or milling, there is known a coated cutting tool in which the surface of a substrate made of cemented carbide, cermet, ceramic, etc. is coated with a coating to improve wear resistance and the like (see Patent Document 1).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent No. 5160231 Gazette Summary of the Invention

[0006] A coated cutting tool according to one aspect of the present invention has a substrate and a coating. The substrate is formed of cemented carbide or cermet. The coating is located on the substrate. Further, when measuring the hardness by pressing a indenter into the coating to a depth of 20% while changing the pressing load of the indenter from the surface of the coating, assuming the minimum hardness among the hardnesses as the first hardness and the maximum hardness as the second hardness, and assuming the depth of the first hardness as the first hardness depth and the depth of the second hardness as the second hardness depth, the second hardness depth is shallower than the first hardness depth, and the difference between the first hardness and the second hardness is greater than 7 GPa. Brief Description of the Drawings

[0007] Figure 1 is a perspective view showing an example of a coated cutting tool according to an embodiment.

[0008] Figure 2 is a side cross-sectional view showing an example of a coated cutting tool according to an embodiment.

[0009] Figure 3 is a cross-sectional view showing an example of a coating according to an embodiment.

[0010] Figure 4 is Figure 3 a schematic enlarged view of part H shown.

[0011] Figure 5 is a front view showing an example of a cutting tool according to an embodiment.

[0012] Figure 6 is a table showing the constitution of each specimen.

[0013] Figure 7 is a table showing the results of indentation hardness tests performed on each specimen.

[0014] Figure 8 is a graph showing the results of indentation hardness tests for hard with metal layer and hard without metal layer.

[0015] Figure 9 It is a graph showing the results of indentation hardness tests for cermets with a metal layer and cermets without a metal layer.

[0016] Figure 10 It is a graph showing the change in the residual stress of the coating when the film thickness of the metal layer is changed. Detailed implementation mode

[0017] Hereinafter, while referring to the accompanying drawings, the modes for implementing the coated cutting tool and the cutting tool of the present invention (hereinafter, described as "implementation modes") will be described in detail. Also, the coated cutting tool and the cutting tool of the present invention are not limited to this implementation mode. In addition, the respective implementation modes can be appropriately combined within the range where there is no contradiction in the processing content. In addition, in the following respective implementation modes, the same reference numerals are attached to the same parts, and repeated descriptions are omitted.

[0018] In addition, in the implementation modes shown below, there are cases where expressions such as "constant", "orthogonal", "perpendicular", or "parallel" are used, but these expressions do not need to be "constant", "orthogonal", "perpendicular", or "parallel" in the strict sense. That is, the above respective expressions allow for deviations in, for example, manufacturing accuracy, setting accuracy, etc.

[0019] In the above prior art, there is room for further improvement in enhancing the adhesion between the coating and the substrate.

[0020] In view of the above, the present invention provides a coated cutting tool and a cutting tool capable of enhancing the adhesion between the coating and the substrate.

[0021] <Coated cutting tool>

[0022] Figure 1 It is a perspective view showing an example of the coated cutting tool of the implementation mode. In addition, Figure 2 It is a side sectional view showing an example of the coated cutting tool of the implementation mode. As Figure 1 shown, the coated cutting tool 1 of the implementation mode has a blade body 2.

[0023] (Blade body 2)

[0024] The blade body 2, for example, has a hexahedral shape with a parallelogram shape on the upper surface and the lower surface (the surface intersecting the Z-axis shown as Figure 1 ).

[0025] One corner of the blade body 2 functions as a cutting edge portion. The cutting edge portion has a first surface (e.g., the upper surface) and a second surface (e.g., the side surface) connected to the first surface. In the embodiment, the first surface functions as a "rake face" for scraping off chips generated by cutting, and the second surface functions as a "flank face". The cutting edge is located on at least a part of the ridge line where the first surface and the second surface intersect, and the coated cutting tool 1 cuts the workpiece by contacting the workpiece with this cutting edge.

[0026] In the central portion of the blade body 2, a through hole 5 that penetrates the blade body 2 vertically is provided. In the through hole 5, a bolt 75 (see Figure 5 ) for mounting the coated cutting tool 1 on a tool holder 70 described later is inserted.

[0027] As Figure 2 shown, the blade body 2 has a substrate 10 and a coating 20.

[0028] (Substrate 10)

[0029] The substrate 10 is formed of, for example, cemented carbide. The cemented carbide contains W (tungsten), specifically WC (tungsten carbide). In addition, the cemented carbide may contain Ni (nickel) and Co (cobalt). Alternatively, the substrate 10 may be formed of cermet. The cermet contains, for example, Ti (titanium), specifically TiC (titanium carbide) or TiN (titanium nitride). In addition, the cermet may contain Ni and Co. The coating 20 will be described later.

[0030] (Coating 20)

[0031] The coating 20 is coated on the substrate 10, for example, for the purpose of improving the wear resistance, heat resistance, etc. of the substrate 10. In Figure 2 the example, the coating 20 integrally coats the substrate 10. It is sufficient that the coating 20 is at least located on the substrate 10. When the coating 20 is located on the first surface (here, the upper surface) of the substrate 10, the wear resistance and heat resistance of the first surface are high. When the coating 20 is located on the second surface (here, the side surface) of the substrate 10, the wear resistance and heat resistance of the second surface are high.

[0032] Here, with reference to Figure 3 the specific configuration of the coating 20 will be described. Figure 3 is a cross-sectional view showing an example of the coating 20 of the embodiment.

[0033] As Figure 3 shown, the coating 20 has a hard layer 21. The hard layer 21 is a layer having excellent wear resistance compared to a metal layer 22 described later. The hard layer 21 has one or more metal nitride layers. The hard layer 21 may also be a single layer. Alternatively, it may be like Figure 3A plurality of metal nitride layers are overlapped as shown. In addition, the hard layer 21 may also have a stacked portion 23 formed by stacking a plurality of metal nitride layers, and a third metal nitride layer 24 located above the stacked portion 23. The configuration of such a hard layer 21 will be described later.

[0034] (Metal layer 22)

[0035] In addition, the coating 20 has a metal layer 22. The metal layer 22 is located between the substrate 10 and the hard layer 21. Specifically, the metal layer 22 is in contact with the upper surface of the substrate 10 on one surface (here, the lower surface), and is in contact with the lower surface of the hard layer 21 on the other surface (here, the upper surface).

[0036] The adhesion of the metal layer 22 to the substrate 10 is higher than that of the hard layer 21. As metal elements having such characteristics, for example, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, Y, and Ti can be cited. The metal layer 22 contains at least one or more of the above metal elements.

[0037] In addition, Ti, Zr, V, Cr, and Al elemental substances are not used as the metal layer 22. This is because they all have low melting points and low oxidation resistance, so they are not suitable for use in cutting tools. In addition, Hf, Nb, Ta, and Mo elemental substances have low adhesion to the substrate 10. However, there is no such limitation for alloys containing Ti, Zr, V, Cr, Ta, Nb, Hf, and Al.

[0038] The metal layer 22 may also be an Al - Cr alloy layer containing an Al - Cr alloy. Such a metal layer 22 has a particularly high adhesion to the substrate 10, so the effect of improving the adhesion between the substrate 10 and the coating 20 is high.

[0039] When the metal layer 22 is an Al - Cr alloy layer, the content of Al in the metal layer 22 may be more than the content of Cr in the metal layer 22. For example, the composition ratio (atomic %) of Al to Cr in the metal layer 22 may be 70:30. By having such a composition ratio, the adhesion between the substrate 10 and the metal layer 22 is higher.

[0040] The metal layer 22 may also contain components other than the above-mentioned metal elements (Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, Si, Y, Ti). However, from the viewpoint of adhesion to the substrate 10, the metal layer 22 may contain the above-mentioned metal elements in a total amount of at least 95 atomic% or more. More preferably, the metal layer 22 may contain the above-mentioned metal elements in a total amount of 98 atomic% or more. For example, when the metal layer 22 is an Al-Cr alloy layer, the metal layer 22 may contain at least Al and Cr in a total amount of 95% or more. In addition, the metal layer 22 may also contain at least Al and Cr in a total amount of 98% or more. Further, the ratio of the metal components in the metal layer 22 can be specified by analysis using EDS (Energy Dispersive X-ray Spectrometer), for example.

[0041] The substrate 10 may have a binder phase such as Co. The binder phase made of metal has high affinity with the metal layer 22. Therefore, by providing the binder phase on the substrate 10, the adhesion between the substrate 10 and the metal layer 22 can be further improved.

[0042] Thus, in the coated cutting tool 1 of the embodiment, by providing a metal layer 22 having higher wettability with the substrate 10 than the hard layer 21 between the substrate 10 and the hard layer 21, the adhesion between the substrate 10 and the coating 20 can be improved. Further, since the adhesion between the metal layer 22 and the hard layer 21 is also high, it is difficult for the hard layer 21 to peel off from the metal layer 22.

[0043] In addition, the coated cutting tool 1 may have a compound containing the metal elements contained in the substrate 10 and the metal elements contained in the metal layer 22 at the interface F between the substrate 10 and the metal layer 22.

[0044] For example, when the substrate 10 is cemented carbide and the metal layer 22 may be a TiSi layer containing Ti and Si. In this case, the coated cutting tool 1 may have TiW (titanium tungsten) at the interface F between the substrate 10 and the metal layer 22.

[0045] By having a compound containing the metal elements contained in the substrate 10 and the metal elements contained in the metal layer 22 present at the interface F between the substrate 10 and the metal layer 22 in this way, the bonding force between the substrate 10 and the metal layer 22 can be improved. Therefore, according to the coated cutting tool 1, the adhesion between the coating 20 and the substrate (here, the substrate 10) can be improved.

[0046] The metal layer 22 is formed by an arc ion plating method (AIP method). The AIP method is a method of forming a metal nitride film by evaporating a target metal by arc discharge in a vacuum atmosphere and combining it with N 2 gas. At this time, the bias voltage applied to the substrate 10 as the object to be coated may be 400 V or more. The hard layer 21 described later can also be formed by the AIP method.

[0047] (Hard layer 21)

[0048] Next, with reference to Figure 4 The structure of the hard layer 21 will be described. Figure 4 is Figure 3 a schematic enlarged view of the H part shown in

[0049] As Figure 4 shown, the hard layer 21 has a stacked portion 23 located above the metal layer 22 and a third metal nitride layer 24 located above the stacked portion 23.

[0050] The stacked portion 23 has a plurality of first metal nitride layers 23a and a plurality of second metal nitride layers 23b. The stacked portion 23 has a structure in which the first metal nitride layers 23a and the second metal nitride layers 23b are alternately stacked.

[0051] The thicknesses of the first metal nitride layer 23a and the second metal nitride layer 23b can be 50 nm or less, respectively. By forming the first metal nitride layer 23a and the second metal nitride layer 23b thinly like this, the residual stress of the first metal nitride layer 23a and the second metal nitride layer 23b is small. Thus, for example, peeling and cracking of the first metal nitride layer 23a and the second metal nitride layer 23b are less likely to occur, and thus the durability of the coating 20 is high.

[0052] The first metal nitride layer 23a is a layer in contact with the metal layer 22, and the second metal nitride layer 23b is formed on the first metal nitride layer 23a.

[0053] The first metal nitride layer 23a and the second metal nitride layer 23b may contain the metals contained in the metal layer 22.

[0054] For example, the metal layer 22 contains two metals (here, "first metal" and "second metal"). In this case, the first metal nitride layer 23a contains the nitride of the first metal and the third metal. The third metal is a metal not contained in the metal layer 22. In addition, the second metal nitride layer 23b contains the nitrides of the first metal and the second metal.

[0055] For example, in the embodiment, the metal layer 22 may contain Al and Cr. In this case, the first metal nitride layer 23a may contain Al. Specifically, the first metal nitride layer 23a may be an AlTiN layer containing AlTiN which is a nitride of Al and Ti. In addition, the second metal nitride layer 23b may be an AlCrN layer containing AlCrN which is a nitride of Al and Cr.

[0056] In this way, by disposing the first metal nitride layer 23a containing the metal included in the metal layer 22 on the metal layer 22, the adhesion between the metal layer 22 and the hard layer 21 is high. Thus, since the hard layer 21 is difficult to peel off from the metal layer 22, the durability of the coating 20 is high.

[0057] The first metal nitride layer 23a, which is an AlTiN layer, is excellent in, for example, abrasion resistance in addition to the adhesion to the metal layer 22 described above. Further, the second metal nitride layer 23b, which is an AlCrN layer, is excellent in, for example, heat resistance and oxidation resistance. Thus, by including the first metal nitride layer 23a and the second metal nitride layer 23b having different compositions, the coating 20 can control characteristics such as the abrasion resistance and heat resistance of the hard layer 21. Thereby, the tool life of the coated tool 1 can be extended. For example, in the hard layer 21 of the embodiment, the excellent heat resistance of AlCrN can be maintained while improving mechanical properties such as the adhesion to the metal layer 22 and abrasion resistance.

[0058] The third metal nitride layer 24 may be disposed on the stacked portion 23. Specifically, the third metal nitride layer 24 is in contact with the second metal nitride layer 23b in the stacked portion 23. The third metal nitride layer 24 is, for example, a metal nitride layer (AlTiN layer) containing Ti and Al, like the first metal nitride layer 23a.

[0059] The thickness of the third metal nitride layer 24 may be thicker than the thicknesses of the first metal nitride layer 23a and the second metal nitride layer 23b. Specifically, when the thicknesses of the first metal nitride layer 23a and the second metal nitride layer 23b are 50 nm or less as described above, the thickness of the third metal nitride layer 24 may be 1 μm or more. For example, the thickness of the third metal nitride layer 24 may also be 1.2 μm.

[0060] Thus, for example, when the friction coefficient of the third metal nitride layer 24 is low, the anti-bonding property of the coated tool 1 can be improved. Further, for example, when the hardness of the third metal nitride layer 24 is high, the abrasion resistance of the coated tool 1 can be improved. Further, for example, if the oxidation start temperature of the third metal nitride layer 24 is high, the oxidation resistance of the coated tool 1 can be improved.

[0061] In addition, the thickness of the third metal nitride layer 24 may be thicker than the thickness of the stacked portion 23. Specifically, in the embodiment, when the thickness of the stacked portion 23 is 0.5 μm or less, the thickness of the third metal nitride layer 24 may be 1 μm or more. For example, when the thickness of the stacked portion 23 is 0.3 μm, the thickness of the third metal nitride layer 24 may be 1.2 μm. Thus, by making the third metal nitride layer 24 thicker than the stacked portion 23, the improvement effects such as the anti-bonding property and abrasion resistance are higher.

[0062] Further, the thickness of the metal layer 22 can be, for example, 0.1 μm or more and less than 0.6 μm. That is, the metal layer 22 can be thicker than the thicknesses of the first metal nitride layer 23a and the second metal nitride layer 23b, respectively, and can also be thinner than the stacked portion 23.

[0063] When the metal layer 22 is a TiSi layer, the first metal nitride layer 23a can be a nitride layer containing Al, Cr, and Si (AlCrSiN layer), and the second metal nitride layer 23b can be a nitride layer containing Ti and Si (TiSiN layer).

[0064] When the first metal nitride layer 23a is an AlCrSiN layer, it is preferable that the composition ratio of Cr in the first metal nitride layer 23a is more than the composition ratio of Al in the first metal nitride layer 23a. That is, the first metal nitride layer 23a is preferably Cr-rich. For example, the composition ratio (atomic %) of Al to Cr in the AlCrSiN layer is preferably 40:50. By having such a composition ratio, the peel resistance of the coating 20 can be improved compared to the case of being Al-rich.

[0065] <Cutting Tool>

[0066] Next, with reference to Figure 5 , the structure of a cutting tool having the above-described coated tool will be described. Figure 5 FIG. is a front view showing an example of a cutting tool according to an embodiment.

[0067] As Figure 5 shown, the cutting tool 100 according to the embodiment includes a coated tool 1 and a tool shank 70 for fixing the coated tool 1.

[0068] The tool shank 70 is a rod-shaped member extending from a first end ( Figure 5 the upper end in Figure 5 ) toward a second end (

[0069] The tool shank 70 has a clamping groove 73 at the end on the first end side. The clamping groove 73 is a portion for mounting the coated tool 1 and has a support surface intersecting the rotation direction of the workpiece to be cut and a restricting side surface inclined with respect to the support surface. A bolt hole for tightening a bolt 75 described later is provided on the support surface.

[0070] The coated cutting tool 1 is located in the card slot 73 of the tool shank 70 and is mounted on the tool shank 70 by a bolt 75. That is, the bolt 75 is inserted into the through hole 5 of the coated cutting tool 1, and the front end of the bolt 75 is inserted into the bolt hole of the supporting surface formed in the card slot 73, and the threaded portions are tightened. Thus, the coated cutting tool 1 is mounted on the tool shank 70 in such a manner that the cutting edge portion protrudes outward from the tool shank 70.

[0071] In the embodiment, a cutting tool for so-called turning is illustrated. As turning, for example, internal diameter machining, external diameter machining, and grooving can be cited. Further, as the cutting tool, it is not limited to the one for turning. For example, a coated cutting tool 1 for milling can also be used.

[0072] For example, the cutting of the work material includes: (1) a step of rotating the work material; (2) a step of cutting the work material by bringing the cutting edge of the coated cutting tool 1 into contact with the rotating work material; and (3) a step of separating the coated cutting tool 1 from the work material. Further, as a representative example of the material of the work material, carbon steel, alloy steel, stainless steel, cast iron, or non-ferrous metal can be cited.

[0073] (Example 1: Indentation hardness test)

[0074] The inventors of the present application conducted indentation hardness tests on specimens having a coating formed on cemented carbide and specimens having a coating formed on cermet, respectively.

[0075] The specimens are the following 4 types.

[0076] (1a) A specimen having a coating with a metal layer formed on cemented carbide (hereinafter, referred to as "cemented carbide with metal layer")

[0077] (1b) A specimen having a coating without a metal layer formed on cemented carbide (hereinafter, referred to as "cemented carbide without metal layer")

[0078] (2a) A specimen having a coating with a metal layer formed on cermet (hereinafter, referred to as "cermet with metal layer")

[0079] (2b) A specimen having a coating without a metal layer formed on cermet (hereinafter, referred to as "cermet without metal layer")

[0080] Refer to Figure 6 The specific configurations of the respective specimens will be described. Figure 6 It is a table showing the configurations of the respective specimens.

[0081] As Figure 6As shown, the hard metal layer has a coating including a metal layer and a hard layer on a substrate formed of cemented carbide. Specifically, a metal layer is provided on the substrate, and a hard layer is provided on the metal layer. On the other hand, the hard metal without a metal layer has a coating including a hard layer on a substrate formed of cemented carbide. Similarly, the cermet with a metal layer has a coating including a metal layer and a hard layer on a substrate formed of cermet, and the cermet without a metal layer has a coating including a hard layer on a substrate formed of cermet.

[0082] The metal layers in the hard metal with a metal layer and the cermet with a metal layer contain Al and Cr. The specific composition of such a metal layer is Al 70 Cr 30 . That is, the metal layer contains 70 atomic % of Al and 30 atomic % of Cr. In addition, the thickness of the metal layer is 0.2 μm.

[0083] The hard layer of each specimen has a first metal nitride layer, a second metal nitride layer, and a third metal nitride layer. The first metal nitride layer and the second metal nitride layer are alternately stacked. In addition, the third metal nitride layer is located above the alternately stacked first metal nitride layer and second metal nitride layer.

[0084] In Figure 6 , in the ratio of only the metal components of the first metal nitride layer described as TiAlNbWSiN, Ti is 42 atomic %, Al is 48 atomic %, Nb is 3 atomic %, W is 4 atomic %, and Si is 3 atomic %. In addition, in the first metal nitride layer, about 100 atomic % of N is contained relative to 100 atomic % of the metal components. The thickness of one first metal nitride layer is 50 nm.

[0085] In Figure 6 , in the ratio of only the metal components of the second metal nitride layer described as AlCrN, Al is 70 atomic % and Cr is 30 atomic %. In addition, in the second metal nitride layer, about 100 atomic % of N is contained relative to 100 atomic % of the metal components. The thickness of one second metal nitride layer is 50 nm.

[0086] The total thickness of the multiple first metal nitride layers and the multiple second metal nitride layers is 0.5 μm.

[0087] The composition of the third metal nitride layer is the same as that of the first metal nitride layer. The thickness of the third metal nitride layer is 2 μm.

[0088] The results of the indentation hardness test on such specimens are shown in Figures 7 to 9 . Figure 7 is a table showing the results of the indentation hardness test on each specimen. In addition, Figure 8It is a graph showing the results of the indentation hardness tests for hard materials with a metal layer and hard materials without a metal layer. Figure 9 It is a graph showing the results of the indentation hardness tests for cermets with a metal layer and cermets without a metal layer.

[0089] Furthermore, this test was conducted using a micro-indentation hardness tester "ENT-1100b / a" (manufactured by Elionix, Inc.).

[0090] Before measuring the hardness, the thickness of the coating was measured in a cross-section of the substrate orthogonal to the substrate surface. The thickness of the coating was 2.7 μm when there was a metal layer. When there was no metal layer, the thickness of the coating was 2.5 μm. From the surface of the coating, the indenter was pressed into an amount equal to 20% of the coating thickness. The indenter was pressed into the coating surface by approximately 0.02 μm each time. This indentation depth could be increased by increasing the indentation load. Increasing the indentation depth by 0.02 μm each time, in other words, was equivalent to increasing the indentation load by approximately 5 mN each time.

[0091] In this test, if the indenter was pressed into a depth equal to 20% of the coating thickness, the hardness near the substrate surface could basically be measured from the surface of the coating. In the present invention, the hardness of the coating, as described above, is the hardness obtained by pressing the indenter into a depth of 20% of the coating while changing the indentation load of the indenter from the surface of the coating. In the indentation hardness test, the deeper the indentation depth, the deeper the region from the coating surface where the hardness can be measured.

[0092] In Figure 8 , the measurement results for hard materials with a metal layer are represented by open circles, and the measurement results for hard materials without a metal layer are represented by filled triangles. Additionally, in Figure 9 , the measurement results for cermets with a metal layer are represented by open circles, and the measurement results for cermets without a metal layer are represented by filled triangles.

[0093] As Figure 8 shown, it can be seen that compared with hard materials without a metal layer, the overall hardness of hard materials with a metal layer is higher. This increase in hardness is significant in the region where the indentation depth is above 100 nm and below 200 nm. The hardness at an indentation depth above 100 nm and below 200 nm represents the hardness of the hard layer. From this, it can be known that compared with hard materials without a metal layer, the hardness of the hard layer of hard materials with a metal layer is higher.

[0094] This tendency is the same for cermets with a metal layer. That is, as Figure 9 shown, it can be seen that compared with cermets without a metal layer, the hardness of the hard layer of cermets with a metal layer is also higher.

[0095] Refer to Figure 10 for an explanation of this point. Figure 10It is a graph showing the change in the residual stress of the coating when the film thickness of the metal layer changes.

[0096] In Figure 10 it shows the results of measuring the residual stress of the coating based on the warpage amount of the stainless steel plate with the coating having the metal layer formed thereon. In Figure 10 the results for a film thickness of 0 μm represent the residual stress of the coating without the metal layer, that is, the coating having only the hard layer. In addition, the results for film thicknesses of 0.2 μm, 0.4 μm, and 0.6 μm represent the residual stress of the coating with the metal layer.

[0097] As Figure 10 shown, it can be seen that the residual stress of the coating with the metal layer is higher than that of the coating without the metal layer. The higher the residual stress, the higher the hardness of the coating. Therefore, it can be seen that the hardness of the coating is increased by forming the metal layer.

[0098] As one of the reasons for the increase in the residual stress of the coating under the action of the metal layer, it is considered that, for example, there are the following reasons. That is, in PVD coating, a bias voltage is applied to the object to be coated (such as cemented carbide), and the metal layer is formed. As a result, more ions are attracted to the object to be coated when the bias voltage is applied. As a result, it is considered that a greater residual stress occurs in the coating with the metal layer compared to the coating without the metal layer.

[0099] Also, when the film thickness of the metal layer is 0.6 μm, peeling of the coating occurs and the residual stress decreases. Based on this result, the film thickness of the metal layer is preferably 0.1 μm or more and less than 0.6 μm.

[0100] In addition, as Figure 8 and Figure 9 shown, the hard coating with the metal layer and the cermet coating with the metal layer have a valley in hardness near a penetration depth of 300 - 350 nm. This is a characteristic not seen in the hard coating without the metal layer and the cermet coating without the metal layer. The hardness near a penetration depth of 300 - 350 nm represents the hardness of the metal layer. Since the metal layer is softer compared to the hard layer, it is considered that this valley in hardness is caused.

[0101] Figure 7 Among the results shown, the so-called "maximum hardness" is the maximum value of the hardness in the measurement range (the range from the surface of the coating to 20% of the coating depth), the so-called "minimum hardness" is the minimum value of the hardness in the above measurement range. The so-called "maximum hardness load" is the indentation load of the indenter for the maximum hardness, the so-called "maximum hardness depth" is the indentation depth of the indenter for the maximum hardness. The so-called "minimum hardness load" is the indentation load of the indenter for the minimum hardness, and the so-called "minimum hardness depth" is the indentation depth of the indenter for the minimum hardness.

[0102] The so-called "maximum hardness difference" is the difference between the maximum hardness and the minimum hardness. The so-called "average hardness" is the average value of the hardness within the measurement range.

[0103] Here, for the hard metal layer and the cermet with a metal layer, the minimum hardness is respectively denoted as the "first hardness", and the maximum hardness is denoted as the "second hardness". Additionally, the indentation depth of the first hardness is denoted as the "first hardness depth", and the indentation depth of the second hardness is denoted as the "second hardness depth".

[0104] As Figure 8 and Figure 9 shown, it can be seen that in the hard metal layer and the cermet with a metal layer, the second hardness depth is shallower than the first hardness depth. That is, in the hard metal layer and the cermet with a metal layer, the maximum hardness exists on the surface side of the coating. Additionally, in the hard metal layer and the cermet with a metal layer, the difference between the first hardness and the second hardness (maximum hardness difference) is greater than 7 GPa.

[0105] Thus, the coating can also have regions with high hardness and regions with low hardness. Additionally, the region with high hardness is located on the surface side of the coating compared to the region with low height, and the difference can be greater than 7 GPa. In this case, the region with high hardness has high wear resistance, and the region with low hardness has high chipping resistance. Therefore, the coated cutting tool with such a coating has a long service life.

[0106] Moreover, in the hard metal layer and the cermet with a metal layer, the first hardness depth is greater than 100 nm, which is the minimum value of the indentation depth.

[0107] In this case, the region with a hardness lower than the first hardness is located on the surface side of the coating. Therefore, for the coated cutting tool with such a coating, the toughness on the surface side is relatively high, and initial defects are less likely to occur.

[0108] Furthermore, in the hard metal layer and the cermet with a metal layer, taking the minimum value of the indentation depth (100 nm) as the "third hardness depth", and the hardness at the third hardness depth as the "third hardness". In this case, the hard metal layer has a fourth hardness lower than the third hardness between the third load and the first load.

[0109] Thus, the coated cutting tool with a coating in which regions with low hardness and regions with high hardness are alternately arranged has a long service life.

[0110] The first hardness depth of the hard metal layer can be 300 nm or more and 600 nm or less.

[0111] In this case, the region with high hardness is near the surface of the coating, and the region with the most excellent wear resistance is exposed at an earlier time. Therefore, the coated cutting tool with such a coating has a long service life.

[0112] (Example 2: Scratch Test and Peel Test)

[0113] In addition, the inventors of the present application conducted scratch tests and peel tests on each of the above-mentioned samples of metal-free hard, metal-layered hard, metal-free cermet, and metal-layered cermet. The scratch test is evaluated by the magnitude of the peel load. The larger the peel load, the more difficult it is to peel. In addition, the longer the peel time, the more difficult it is to peel.

[0114] The scratch test was carried out under the conditions of a diamond indenter with a tip shape having an R (radius of curvature) of 200 μm at a speed of 10 mm / min and a load speed of 100 N / min for 1 minute.

[0115] For the peel test, for the quenched material of the work material SCM415, a sample with a tool shape of CNGA120408S01225 was used, and the machining conditions were a cutting speed of 150 m / min, a feed rate of 0.1 mm / rev, and a cutting depth of 0.2 mm, and the time until the hard layer peeled off was evaluated.

[0116] When comparing the metal-free hard and the metal-layered hard, the metal-layered hard has a larger peel load and a significantly longer peel time compared to the metal-free hard. In addition, when comparing the metal-free cermet and the metal-layered cermet, the metal-layered cermet has a larger peel load and a significantly longer peel time compared to the metal-free cermet. Thus, for the metal-layered hard and the metal-layered cermet, compared with the metal-free hard and the metal-free cermet, coating peeling is less likely to occur, that is, the coating has high durability.

[0117] <Modification Example>

[0118] In the above-described embodiment, an example in which the shapes of the upper surface and the lower surface of the coated cutting tool 1 are parallelograms is shown, but the shapes of the upper surface and the lower surface of the coated cutting tool 1 may also be rhombuses, squares, etc. In addition, the shapes of the upper surface and the lower surface of the coated cutting tool 1 may also be triangles, pentagons, hexagons, etc.

[0119] In addition, the shape of the coated cutting tool 1 may be a positive type or a negative type. The positive type is a type in which the side surface is inclined with respect to the central axis passing through the center of the upper surface and the center of the lower surface of the coated cutting tool 1, and the negative type is a type in which the side surface is parallel to the above-mentioned central axis.

[0120] In the above-described embodiment, it is described that the coated cutting tool 1 is used for cutting, but the coated cutting tool of the present application can also be applied to tools other than cutting tools such as excavation tools or cutting tools with cutting edges, for example.

[0121] More effects and modification examples can be easily derived by those skilled in the art. Therefore, the broader aspects of the present invention are not limited by the specific details and representative embodiments described as above. Accordingly, various modifications can be made without departing from the spirit or scope of the general inventive concept defined by the appended claims and their equivalents.

[0122] Symbol Explanation

[0123] 1 Coated cutting tool

[0124] 2 Blade body

[0125] 5 Through-hole

[0126] 10 Substrate

[0127] 20 Coating

[0128] 21 Hard layer

[0129] 22 Metal layer

[0130] 23 Laminated portion

[0131] 23a First metal nitride layer

[0132] 23b Second metal nitride layer

[0133] 24 Third metal nitride layer

[0134] 70 Tool shank

[0135] 73 Card slot

[0136] 75 Bolt

[0137] 100 Cutting tool

Claims

1. A coated cutting tool having: a substrate formed of cemented carbide or cermet, and a coating located on the substrate, said coating comprising: a hard layer; a metal layer located between the substrate and the hard layer, said hard layer having: a stacked portion located above the metal layer and formed by alternately stacking a first metal nitride layer and a second metal nitride layer; a third metal nitride layer located above the stacked portion, said metal layer containing Al and Cr, said first metal nitride layer containing AlTiN, said second metal nitride layer containing AlCrN, said third metal nitride layer containing AlTiN, the thickness of said metal layer being thinner than the thickness of said stacked portion, and the thickness of said third metal nitride layer being thicker than the thickness of said stacked portion, when measuring the hardness by pressing a indenter into the coating from the surface of the coating while changing the indentation load of the indenter until a depth of 20% of the coating is reached, taking the minimum hardness among said hardnesses as the first hardness, the maximum hardness as the second hardness, the depth of said first hardness as the first hardness depth, and the depth of said second hardness as the second hardness depth, said second hardness depth being shallower than said first hardness depth, the difference between said first hardness and said second hardness being greater than 7 GPa.

2. The coated cutting tool according to claim 1, wherein, said first hardness depth is greater than 100 nm.

3. The coated cutting tool according to claim 1, wherein, when taking the hardness at a depth of 100 nm as the third hardness, there is a fourth hardness having a hardness lower than said third hardness between 100 nm and said first hardness depth.

4. The coated cutting tool according to any one of claims 1 to 3, wherein, said substrate is cemented carbide, said first hardness depth is 300 nm or more and 600 nm or less.

5. The coated cutting tool according to any one of claims 1 to 3, wherein, said metal layer contains Al and Cr in a total amount of 95 atomic % or more.

6. The coated cutting tool according to any one of claims 1 to 3, wherein, said substrate has a binder phase.

7. The coated cutting tool according to claim 1, wherein, the thickness of each of said first metal nitride layer and said second metal nitride layer is 50 nm or less.

8. The coated cutting tool according to any one of claims 1 to 3, wherein, said hard layer has: a stacked portion including a plurality of said first metal nitride layers and a plurality of said second metal nitride layers, and formed by alternately stacking said first metal nitride layer and said second metal nitride layer; a third metal nitride layer located at a position farther from the substrate than said stacked portion, the thickness of said third metal nitride layer being thicker than the thickness of each of said first metal nitride layer and said second metal nitride layer.

9. A cutting tool having: a rod-shaped tool shank having a groove at its end; the coated cutting tool according to any one of claims 1 to 8 located in said groove.

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