Surface coated cutting tool

Abstract

A surface-coated cutting tool having a coating layer, the average thickness of a lower layer of the coating layer being 0.1-5.0 [mu] m, the lower layer being a composite nitride layer having an average composition of (Al1-a-bTiaCrb) N (0.10 < a < = 0.55, 0.05 < = b < 0.20, and 0.40 < = (1-a-b) < = 0.70), the average thickness of an upper layer being 0.1-5.0 [mu] m, the upper layer being a composite nitride layer having an average composition of (Ti1-pSip) N (0.10 < = p < = 0.40), the average thickness of an intermediate layer being 10-500 nm, and the average thickness of an intermediate layer being 0.1-5.0 [mu] m. The intermediate layer has two or more laminated units including a first layer and a second layer, the average thickness of the first layer is 3-17 nm, the first layer is a composite nitride layer having an average composition of (Ti1-[rho] Si [rho]) N (0.10 < = [rho] < = 0.40, 1.0 < = p / [rho] < = 1.2), the average thickness (Tmu) of the second layer is 2-12 nm, and the second layer is a composite nitride layer having the same average composition as the lower layer.

Description

Technical Field

[0001] The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a "coated tool"). This application claims priority based on Japanese patent application No. 2023-019953 filed on February 13, 2023. All the contents described in the Japanese patent application are incorporated into this specification by reference. Background Art

[0002] Conventionally, in order to extend the life of cutting tools, there are coated tools in which a coating layer is formed on the surface of a substrate such as tungsten carbide (hereinafter referred to as "WC")-based cemented carbide, thereby improving the wear resistance and the like of the coated tools.

[0003] Furthermore, in order to further improve the cutting performance of the coated tool, various proposals have been made for the composition and structure of the coating layer.

[0004] Patent Document 1 describes a coated tool having a coating layer comprising alternating layers of A and B layers, each layer being alternately stacked one or more layers. The A layer is composed of a nitride including Al and Cr, and the ratio of the number of Cr atoms when the total number of metal atoms constituting the A layer is set to 1 is greater than 0 and less than 0.4. The B layer is composed of a nitride including Ti and Si without Al, and the ratio of the number of Si atoms when the total number of metal atoms constituting the B layer is set to 1 is greater than 0.05 and less than 0.3. The coating layer of this coated tool has oxidation resistance and adhesion resistance even at high temperatures during cutting, thereby suppressing chipping of the tool tip.

[0005] Patent Document 2 describes a coated tool having a coating layer composed of: a Ti b Cr c A layer I is composed of a nitride or carbonitride (0.3≤a≤0.7, 0≤b≤0.5, 0≤c≤0.7, a+b+c=1); and a layer II is a composite layer composed of a three-dimensional mixture of a nitride phase composed of CrAlN and a BN phase, the layer I and the layer II are alternately stacked in two or more layers in a manner such that the layer I is provided on the surface of the substrate and the layer II becomes the outermost layer, the average thickness of the layer I and the layer II are both greater than 50nm, the total average thickness of the coating is 0.1 to 20μm, and the coating has excellent heat resistance, chemical stability at high temperatures, wear resistance and welding resistance.

[0006] Patent document 3 describes a coated tool having a coating layer comprising an A layer formed on a substrate and a B layer formed directly above the A layer. The A layer is a Si-free film of any one of TiAlCr nitrides, oxynitrides, carbonitrides, and carbonitride oxides, and is composed of fine columnar crystals composed of cubic crystals. The width of each columnar crystal in a direction approximately orthogonal to the growth direction of the columnar crystals is formed to be less than 300 nm. The B layer is a Si-containing film mainly composed of SiTi nitrides. The coated tool has wear resistance and durability.

[0007] Patent document 4 describes a coated tool having a coating layer comprising: a first layer formed by alternating multiple layers of a first film composed of Si nitride and a second film composed of AlCr nitride; and a second layer composed of Si nitride stacked on the surface of the first layer and having a film thickness greater than that of the first and second films. The coated tool has high hardness due to the miniaturization of crystals in the coating layer.

[0008] Patent document 5 describes a coated tool, wherein the coating layer of the coated tool includes a close-contact layer in contact with the substrate and an upper layer formed on the close-contact layer, the upper layer includes TiAlN, TiAlSiN or TiSiN, the thickness of the close-contact layer is greater than 2 nm and less than 20 nm, and the close-contact layer includes Cr, Ti, Al, W, C and N (excluding Co), and the coated tool has excellent durability.

[0009] Patent Document 6 describes a coated tool having a coating layer comprising a lower film layer, an upper film layer, and an intermediate film layer formed therebetween. The intermediate film layer is formed by alternating layers, wherein a first layer composed of a nitride or carbonitride of Al, Cr, and Ti and a second layer composed of a nitride or carbonitride of Ti and Si are alternately stacked one or more times. The metal component composition of the first layer is (Al x Cr y Ti z )(x+y+z=100, 50≤x≤65, 20≤y≤30, 5≤z≤20), the metal component of the second layer is composed of (Ti a Si b )(a+b=10080≤a≤90, 10≤b≤20), the coating layer has fracture resistance and peeling resistance.

[0010] Patent Document 7 describes a coated tool in which the coating layer is formed by a layer of Ti m Si 1-m N 1-a- b C a Bb The first layer is composed of Al x Cr y M 1-x-y N 1-a-b C a B b The second layer is alternately stacked, in the first layer, 0.7≤m<1, 0<1-ab≤1, in the second layer, 0.7<x≤0.8, 0<y and 0<1-ab≤1, M is at least one selected from Ti, V, Zr, Nb, Mo, Ta, W, Y and lanthanide elements (except Pm), and the wear resistance of the coated tool is improved.

[0011] Patent Document 1: Japanese Patent No. 5254552

[0012] Patent Document 2: Japanese Patent Publication No. 2013-52477

[0013] Patent Document 3: Japanese Patent No. 4960751

[0014] Patent Document 4: Japanese Patent Publication No. 2021-70075

[0015] Patent Document 5: Japanese Patent No. 6773287

[0016] Patent Document 6: Japanese Patent Publication No. 2020-20030

[0017] Patent Document 7: Japanese Patent Publication No. 2017-179580 Summary of the Invention

[0018] The present invention has been made in view of the above circumstances and the above solutions, and an object of the present invention is to provide a coated tool having excellent durability even when used for high-speed cutting of difficult-to-cut materials such as Ni-based alloys.

[0019] Regarding the surface-coated cutting tool according to the embodiment of the present invention,

[0020] It has a base and a coating layer provided on the base,

[0021] The coating layer comprises a lower layer, an intermediate layer, and an upper layer in order from the surface of the substrate toward the surface of the tool, wherein the sum of the average thickness of the lower layer and the upper layer is 1.0 to 8.0 μm.

[0022] The average thickness of the lower layer (T l ) is 0.1 to 5.0 μm, and the lower layer has an average composition of (Al 1-a-b Ti a Cr b)N(0.10<a≤0.55, 0.05≤b<0.20, 0.40≤(1-ab)≤0.70) composite nitride layer,

[0023] The average thickness of the upper layer (T u ) is 0.1 to 5.0 μm, and the upper layer has an average composition of (Ti 1-p Si p )N(0.10≤p≤0.40) composite nitride layer,

[0024] The average thickness of the intermediate layer (T m ) is 10 to 500 nm, the intermediate layer has two or more stacked units including the first layer on the lower side and the second layer on the upper side,

[0025] The average thickness of the first layer (T ml ) is 3 to 17 nm, and the first layer has an average composition of (Ti 1-ρ Si ρ )N (0.10≤ρ≤0.40, 1.0≤p / ρ≤1.2) composite nitride layer,

[0026] The average thickness of the second layer (T mu ) is 2 to 12 nm, and the second layer is a composite nitride layer having the same average composition as that of the lower layer.

[0027] The surface-coated cutting tool according to the above-mentioned embodiment can satisfy the following requirement (1).

[0028] (1) The average thickness of the lower layer (T l ) and the average thickness of the upper layer (T u ) is 0.2≤T u / T l ≤9.0.

[0029] As described above, the surface-coated cutting tool has excellent durability even when used for high-speed cutting of difficult-to-cut materials such as Ni-based alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of a longitudinal cross section of a coating layer according to one embodiment of the present invention. DETAILED DESCRIPTION

[0031] The present inventors have conducted extensive research focusing on coating layers composed of nitrides of Al, Ti, and Cr, and nitrides of Ti and Si, both of which exhibit excellent durability. As a result, they have discovered that the aforementioned objectives can be achieved by providing a laminated structure for the intermediate layer within the coating layer, optimizing its composition, and maintaining its thickness within a specified range.

[0032] Next, a coating tool according to an embodiment of the present invention based on this knowledge will be described in detail.

[0033] In this specification and claims, when a numerical range is expressed as "L to M" (L and M are both numerical values), the range includes both the upper limit (M) and the lower limit (L). When only the upper limit is expressed in units, the units of the upper limit (M) and the lower limit (L) are the same. Each numerical value includes measurement error.

[0034] Furthermore, the substrate surface referred to in this specification and claims refers to the surface obtained by arithmetically calculating the average line (straight line) of the roughness curve of the interface between the layer of the coating layer closest to the substrate surface and the substrate. This method for calculating this average line allows the substrate surface to be calculated even if the substrate has a curved surface, as long as the tool diameter (the diameter of the substrate) is sufficiently large relative to the thickness of the coating layer. This allows the interface between the coating layer and the substrate to be treated as a flat surface.

[0035] A schematic diagram of a longitudinal section of a coated tool according to one embodiment of the present invention (a section perpendicular to a plane when the base is considered as a plane, ignoring minute irregularities of the base) is shown as follows: Figure 1 .

[0036] Depend on Figure 1 It is clear that the coating layer 8 includes a lower layer 2 directly above the substrate 1, an intermediate layer 3 directly above the lower layer, and an upper layer 7 directly above the intermediate layer. The intermediate layer includes two or more laminated units 6 each including a first layer 4 on the lower side and a second layer 5 on the upper side. Furthermore, in the region indicated as the intermediate layer, a laminated unit including a first layer and a second layer also exists in the white background portion.

[0037] Below, each layer is described in turn.

[0038] 1. Lower level

[0039] The lower layer is arranged directly above the base body.

[0040] The average thickness of the lower layer (T l The average thickness is preferably 0.1 to 5.0 μm. This preferred range is because if it is less than 0.1 μm, the wear resistance and chip resistance of the underlying layer are insufficient. On the other hand, if it exceeds 5.0 μm, the internal distortion of the underlying layer increases, making the underlying layer more susceptible to self-destruction. A more preferred average thickness is 0.2 to 4.0 μm, and an even more preferred average thickness is 0.3 to 3.6 μm.

[0041] The lower layer preferably has an average composition of (Al 1-a-b Ti a Cr b)N (0.10<a≤0.55, 0.05≤b<0.20, 0.40≤(1-ab)≤0.70). The reason why a and b preferably satisfy the above ranges is as follows.

[0042] If a does not exceed 0.10 and b does not reach 0.05 or more, the toughness improvement effect brought about by providing a complex nitride with a different lattice constant directly above the lower layer cannot be exerted. In addition, if a exceeds 0.55, the durability of the coated tool decreases due to the reduced Al content. If b is 0.20 or more, the lower layer softens and the wear resistance decreases. Furthermore, when (1-ab) is less than 0.40, the high-temperature hardness and high-temperature oxidation resistance of the lower layer decrease. On the other hand, if it exceeds 0.70, hexagonal crystal grains are formed, the hardness of the lower layer decreases, and sufficient wear resistance cannot be obtained. More preferred values ​​are a of 0.15 to 0.55, b of 0.05 to 0.15, and (1-ab) of 0.50 to 0.65. Even more preferred values ​​are a of 0.20 to 0.37, b of 0.08 to 0.15, and (1-ab) of 0.55 to 0.65.

[0043] Here, according to an example of a manufacturing method described later, it is manufactured as (Al 1-a-b Ti a Cr b The ratio of ) to N is 1: 1, but there are cases where it is not intentionally 1: 1. This also applies to other complex nitrides described below.

[0044] 2. Upper level

[0045] The upper layer is provided directly above the intermediate layer described later and is located on the surface of the cladding layer.

[0046] The average thickness of the upper layer (T u ) is preferably 0.1 to 5.0 μm. This preferred range is because if it is less than 0.1 μm, the wear resistance of the upper layer decreases. On the other hand, if it exceeds 5.0 μm, the upper layer is more likely to chip or break. A more preferred average thickness is 0.2 to 4.0 μm, and an even more preferred average thickness is 0.3 to 3.6 μm.

[0047] The average thickness of the upper layer (T u ) and the average thickness of the lower layer (T l The sum of the average thickness of the upper layer and the average thickness of the lower layer is preferably 1.0 to 8.0 μm. This is because if the thickness is less than 1.0 μm, the coating layer will not exhibit excellent wear resistance during long-term use. On the other hand, if it exceeds 8.0 μm, the upper layer is prone to abnormal damage such as chipping, missing, and peeling. The sum of the average thickness of the upper layer and the average thickness of the lower layer is more preferably 1.0 to 5.0 μm.

[0048] In addition, the average thickness of the lower layer (T l ) and the average thickness of the upper layer (T u ) is more preferably 0.2≤T u / T l ≤9.0. The reasons are as follows. When it is less than 0.2, the wear resistance and oxidation resistance of the upper layer may not be fully exerted, and sufficient adhesion strength between the substrate and the lower layer may not be obtained. On the other hand, if it exceeds 9.0, the residual stress of the entire coating layer becomes too large, and self-destruction or peeling may occur. u / T l More preferably, 0.2≤T u / T l ≤4.0.

[0049] The upper layer preferably has an average composition of (Ti 1-p Si p )N (0.10≤p≤0.40). The reason why p preferably falls within this range is as follows. If p is less than 0.10, the oxidation resistance and lubricity provided by the addition of Si cannot be exerted. On the other hand, if it exceeds 0.40, the residual stress becomes significantly excessive, causing chipping of the upper layer. The more preferred range for p is 0.10 to 0.30, and the even more preferred range is 0.15 to 0.25.

[0050] 3. Middle layer

[0051] The middle layer is disposed directly above the lower layer and directly below the upper layer.

[0052] The intermediate layer has two or more laminated units including a first layer on the lower side and a second layer on the upper side.

[0053] The first layer on the lower side preferably has an average composition of (Ti 1-ρ Si ρ )N (0.10≤ρ≤0.40, 1.0≤p / ρ≤1.2). This is because if this range is met, the lattice distortion in the intermediate layer is reduced, and the adhesion with the adjacent upper stacking unit layer is improved. However, if p / ρ is less than 1.0 or exceeds 1.2, the compositional variation with the upper layer becomes large, resulting in a sharp change in Si content, which reduces the chipping resistance of the intermediate layer.

[0054] The second layer on the upper side is preferably a composite nitride layer having the same average composition as that of the lower layer, that is, a layer having the same values ​​of a and b as those of the lower layer (Al 1-a-b Ti a Cr b)N (0.05≤a, 0.05≤b<0.20, 0.40≤(1-ab)≤0.70). The reason for this is that by having the same average composition as the lower layer, residual stress is not concentrated in the intermediate layer, and the adhesion between the lower layer and the upper layer can be improved.

[0055] The average thickness of the first layer on the lower side (T ml ) is preferably 3 to 17 nm, and the average thickness of the second layer on the upper side (T mu The reason for this is that if this range is met, the grains constituting the upper and lower stacking unit layers become finer, the grain boundary area increases, and thus plastic deformation and crack development at the grain boundaries are suppressed.

[0056] In addition, the average thickness of the first layer on the lower side (T ml ) and the average thickness of the second layer on the upper side (T mu If it is within this range, the above-mentioned object can be achieved more reliably.

[0057] The average thickness of the intermediate layer is preferably 10 to 500 nm. While the reason for this is uncertain, it is speculated that if the thickness is less than 10 nm, the adhesion between the intermediate layer and the lower and upper layers cannot be sufficiently improved. On the other hand, if the thickness exceeds 500 nm, the residual stress in the lower stacking unit layer will easily cause cracks in the intermediate layer, which will in turn reduce the adhesion. The more preferred average thickness is 10 to 450 nm, the more preferred average thickness is 10 to 250 nm, and the most preferred average thickness is 20 to 150 nm.

[0058] To achieve an average thickness of the intermediate layer within the preferred range, it is preferable to stack 2 to 100 layers. Within this range, cracks are less likely to form within the coating layer, improving chipping resistance. The number of layers is more preferably 5 to 50, and even more preferably 6 to 20.

[0059] 4. Other layers

[0060] (5-1) Possible layers

[0061] The aforementioned problems can be sufficiently solved only by the lower layer, the middle layer, and the upper layer, but a surface layer may be selectively provided in addition to these layers.

[0062] surface layer

[0063] The surface layer may be, for example, a TiN layer. Since the TiN layer has a golden hue, it can be used as an identification layer to distinguish whether the coated tool is unused or used based on the change in hue of the coated tool surface.

[0064] The average thickness of the TiN layer serving as the discrimination layer may be, for example, 0.1 to 1.0 μm.

[0065] (5-2) Layers that may appear accidentally

[0066] In this embodiment, film formation is performed so that no layers other than the lower layer, intermediate layer, upper layer, and surface layer exist. However, when the type of layer to be formed is changed, pressure or temperature changes within the film formation apparatus may occur unintentionally, and a layer with a different composition from those layers may be accidentally formed between the layers (unintentionally). Such a layer is referred to as a layer that may be accidentally formed.

[0067] 2. Matrix

[0068] (1) Material

[0069] If the substrate used in this embodiment is a material of a known substrate, any material may be used as long as it does not hinder the achievement of the aforementioned purpose. For example, preferably any of cemented carbide (WC-based cemented carbide, an alloy containing WC, Co, and carbonitrides of Ti, Ta, Nb, etc.), cermet (for example, a material containing TiC, TiN, or TiCN as a main component), ceramic (for example, titanium carbide, silicon carbide, silicon nitride, aluminum nitride, or aluminum oxide), cBN sintered body, or diamond sintered body is used.

[0070] (2) Shape

[0071] The shape of the base body is not particularly limited as long as it is a shape used as a cutting tool, and examples thereof include the shape of an insert, the shape of an end mill, and the shape of a drill.

[0072] 3. Determination method

[0073] A focused ion beam (FIB) device was used to cut a longitudinal cross-section (a cross-section perpendicular to the substrate surface when the substrate surface is treated as having no micro-concavities and convexities). The thickness of each layer was measured at five locations for each layer using a scanning electron microscope (SEM). The observation magnification was any magnification that could measure the thickness, but it was 5,000 to 200,000 times for the thickness of the lower layer, upper layer, and cladding layer as a whole, and 100,000 to 500,000 times for the thickness of the intermediate layer, upper-side laminated unit layer, and upper-side laminated unit layer. The average of these measurements was defined as the average thickness of each layer (if only one layer was present, the average of the five measurements for that layer was taken as the average thickness). Furthermore, the composition of the lower layer, intermediate layer, and upper layer was measured at five locations for each layer using energy dispersive X-ray analysis (EDS) attached to the SEM, and the average composition was calculated from the average of these measurements.

[0074] 4. Manufacturing method

[0075] The cladding layer of this embodiment can be produced by, for example, the following PVD method.

[0076] Specifically, an arc ion plating (AIP) apparatus is set to a nitrogen atmosphere, and arc discharge is generated between an Al-Ti-Cr alloy target of a specified composition and an anode electrode to form a lower layer of a specified average thickness. Next, arc discharge is generated between a Ti-Si alloy target of a specified composition and the anode electrode, also in a nitrogen atmosphere, to form a first layer on the lower side of a specified average thickness. Next, arc discharge is generated between the Al-Ti-Cr alloy target and the anode electrode to form a second layer on the upper side of a specified average thickness, thereby forming a stacked unit. After forming a specified number of layers of this stacked unit, arc discharge is generated between another Ti-Si alloy target of a specified composition and the anode electrode, also in a nitrogen atmosphere, to form an upper layer of a specified average thickness.

[0077] The above description includes the following additional features.

[0078] (Note 1)

[0079] A surface-coated cutting tool comprises a base body and a coating layer provided on the base body, wherein the surface-coated cutting tool is characterized in that:

[0080] The coating layer comprises a lower layer, an intermediate layer, and an upper layer in order from the surface of the substrate toward the surface of the tool, wherein the sum of the average thickness of the lower layer and the upper layer is 1.0 to 8.0 μm.

[0081] The average thickness of the lower layer (T l ) is 0.1 to 5.0 μm, and the lower layer has an average composition of (Al 1-a-b Ti a Cr b )N(0.10<a≤0.55, 0.05≤b<0.20, 0.40≤(1-ab)≤0.70) composite nitride layer,

[0082] The average thickness of the upper layer (T u ) is 0.1 to 5.0 μm, and the upper layer has an average composition of (Ti 1-p Si p )N(0.10≤p≤0.40) composite nitride layer,

[0083] The average thickness of the intermediate layer (T m ) is 10 to 500 nm, the intermediate layer has two or more stacked units including the first layer on the lower side and the second layer on the upper side,

[0084] The average thickness of the first layer (T ml ) is 3 to 17 nm, and the first layer has an average composition of (Ti 1-ρ Si ρ )N(0.10≤ρ≤0.40,1.0≤p / ρ≤1.2)composite nitride layer,

[0085] The average thickness of the second layer (T mu ) is 2 to 12 nm, and the second layer is a composite nitride layer having the same average composition as that of the lower layer.

[0086] (Note 2)

[0087] The surface-coated cutting tool according to Supplementary Note 1 is characterized in that the average thickness of the lower layer (T l ) and the average thickness of the upper layer (T u ) is 0.2≤T u / T l ≤9.0.

[0088] (Note 3)

[0089] The surface-coated cutting tool according to Supplementary Note 1 or 2, characterized in that it comprises two or more and 100 or less of the laminated units.

[0090] (Note 4)

[0091] The surface-coated cutting tool according to any one of Supplementary Notes 1 to 3 is characterized in that the average thickness (T ml ) and the average thickness of the second layer (T mu ) is 2 to 12 nm.

[0092] Example

[0093] Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to the Examples.

[0094] WC powder, TiC powder, VC powder, TaC powder, NbC powder, Cr3C2 powder, and Co powder were prepared as raw material powders. These raw material powders were blended according to the composition shown in Table 1, and wax was further added. The powders were wet-mixed in a ball mill for 72 hours. After drying under reduced pressure, they were compacted at a pressure of 100 MPa to form a powder compact. After sintering, a sintered round rod with a diameter of 6 mm was formed for forming a base. Next, WC-based cemented carbide end mill bases 1 to 4 were produced by grinding, each having a groove-forming portion with a diameter and length of 6 mm and a double-edged shape with a helix angle of 45 degrees.

[0095] Then, each of the end mill bases 1 to 4 was ultrasonically cleaned in acetone and dried.

[0096] An end mill base is installed along the outer periphery at a position separated by a specified distance from the central axis of the rotating table of the AIP device in the radial direction. A target (cathode electrode) composed of an Al-Ti-Cr alloy of a specified composition is arranged on one side of the AIP device, and two targets (cathode electrodes) composed of a Ti-Si alloy of a specified composition are arranged on the other side.

[0097] Then, the AIP device was evacuated and kept in vacuum (1×10 -3 Pa or less), while heating the AIP device to 500°C using a heater, a DC bias voltage of -400V is applied to the above-mentioned end mill substrate rotating on the turntable, and Ar ion bombardment treatment is carried out for 15 minutes using an ion source emitted by thermal electrons from a filament.

[0098] Furthermore, a coating layer was formed on the above-mentioned end mill base bodies 1 to 4 by the following steps, thereby manufacturing surface-coated end mills 1 to 18 (hereinafter referred to as Examples 1 to 18), respectively.

[0099] Manufacturing of the cladding layer

[0100] The coating layers of the examples shown in Table 3 were produced by the following steps 1) to 5).

[0101] 1) Film formation of the lower layer

[0102] Nitrogen gas is introduced into the device as a reaction gas and the nitrogen partial pressure is set to the lower layer film forming conditions shown in Table 2. The temperature of the above-mentioned end mill substrate rotating on the above-mentioned turntable is maintained at the temperature shown in Table 2, and a DC bias voltage shown in Table 2 is applied. A current of 150A is passed between the above-mentioned Al-Ti-Cr alloy target and the anode electrode to generate arc discharge, thereby vapor-depositing the lower layer having the composition and average thickness shown in Table 3 on the surface of the above-mentioned end mill substrate.

[0103] 2) Film formation of the first layer on the lower side

[0104] Next, the nitrogen partial pressure is set as shown in the film forming conditions of the first layer on the lower side in Table 2, the temperature of the above-mentioned end mill substrate rotating on the above-mentioned turntable is maintained at the temperature shown in Table 2, and a DC bias voltage shown in Table 2 is applied, and a current of 100A is passed between the above-mentioned Ti-Si alloy target and the anode electrode to generate arc discharge, thereby vapor-depositing the first layer on the lower side with the composition and average thickness shown in Table 3 on the surface of the above-mentioned end mill substrate.

[0105] 3) Formation of the second layer on the upper side

[0106] The nitrogen partial pressure is set as shown in the film forming conditions of the second layer on the upper side of Table 2, the temperature of the above-mentioned end mill base rotating on the above-mentioned turntable is maintained at the temperature shown in Table 2, and the DC bias voltage shown in Table 2 is applied, and a current of 150A is passed between the above-mentioned Al-Ti-Cr alloy target and the anode electrode to generate arc discharge, and the second layer on the upper side having the composition and average thickness shown in Table 3 is formed by vapor deposition.

[0107] 4) Film formation of laminate layer

[0108] Since a stacked unit is formed by the above-mentioned 2) and 3), the above-mentioned 2) and 3) operations are repeated to make the stacked unit have a predetermined number of stacked layers.

[0109] 5) Film formation on the upper layer

[0110] Finally, the nitrogen partial pressure is set as shown in the film formation conditions of the upper layer shown in Table 2, the temperature of the above-mentioned end mill substrate rotating on the above-mentioned turntable is maintained at the temperature shown in Table 2, and the DC bias voltage shown in Table 2 is applied, and a current of 100A is passed between the Ti-Si alloy target of a specified composition and the anode electrode to generate arc discharge, thereby vapor-depositing an upper layer with the composition and average thickness shown in Table 3 on the surface of the above-mentioned end mill substrate.

[0111] For comparison, each of the above-mentioned end mill bases 1 to 4 was ultrasonically cleaned in acetone and dried, and then installed along the outer periphery at a position separated by a specified distance from the central axis of the turntable of the AIP device in the radial direction. The bombardment treatment was performed in the same manner as in Examples 1 to 18, and surface-coated end mills 1' to 19' (hereinafter referred to as Comparative Examples 1' to 19') of the comparative examples were manufactured according to the film forming conditions 1' to 19' shown in Table 2.

[0112] The average thickness and average composition of Examples 1 to 18 and Comparative Examples 1' to 19' produced above were determined by the aforementioned method. Furthermore, the number of layers was calculated based on the ratio of the thickness of the intermediate layer to the thickness of the stacking unit layer.

[0113] Table 3 shows the measured and calculated values.

[0114] [Table 1]

[0115]

[0116] [Table 2]

[0117]

[0118]

[0119]

[0120] In Tables 1 and 3, “-” indicates that there is no corresponding item.

[0121] Next, cutting tests were conducted on Examples 1 to 18 and Comparative Examples 1' to 19' under the following cutting conditions, and the flank wear width was measured.

[0122] <Cutting conditions>

[0123] Workpiece: Plate of Ni-based heat-resistant alloy (Cr18 mass% -Fe18 mass% -Nb5 mass% -Mo3 mass% -Ti1 mass% -Al0.5 mass% -Ni balance) with a plane size of 75 mm × 150 mm and a thickness of 250 mm

[0124] Cutting speed: 100m / min.

[0125] Feed rate: 0.05mm / tooth

[0126] Feed amount: ap 2.4mm, ae 0.3mm

[0127] Cutting length: 50m

[0128] Cutting oil: water-soluble coolant

[0129] [Table 4]

[0130]

[0131] In Table 4, "※" represents the time when the substrate is exposed and the cutting length does not reach 50m by detecting abnormal sounds generated by damage to the coating layer (damage to the coating layer is presumably caused by peeling, welding, chipping, wear, etc.) every one minute.

[0132] As is clear from Table 4, Examples 1 to 18 all exhibited smaller flank wear widths and had durability, whereas Comparative Examples 1' to 19' all exhibited larger flank wear widths and reached their service life before reaching the cutting length of the cutting test.

[0133] The embodiments disclosed above are merely illustrative in all aspects and are not restrictive. The scope of the present invention is expressed by the claims, rather than the embodiments described above, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0134] Description of Reference Numerals

[0135] 1. Substrate

[0136] 2 Lower level

[0137] 3 Middle Layer

[0138] 4 First layer on the lower side

[0139] 5 Second floor on the upper side

[0140] 6 stacked units

[0141] 7 Upper

[0142] 8. Coating

Claims

1. A surface-coated cutting tool comprising a substrate and a coating layer provided on the substrate, wherein: The coating layer comprises a lower layer, an intermediate layer, and an upper layer in order from the surface of the substrate toward the surface of the tool, wherein the sum of the average thickness of the lower layer and the upper layer is 1.0 to 8.0 μm. The average thickness T of the lower layer l is 0.1 to 5.0 μm, and the lower layer has an average composition of (Al 1-a-b Ti a Cr b )N composite nitride layer, wherein 0.10<a≤0.55, 0.05≤b<0.20, 0.40≤(1-ab)≤0.70, The average thickness T of the upper layer u 0.1~5.0μm, the upper layer has an average composition of (Ti 1-p Si p )N composite nitride layer, wherein 0.10≤p≤0.40, The average thickness T of the intermediate layer m The thickness of the intermediate layer is 10 to 500 nm, and the intermediate layer has two or more stacked units including the first layer on the lower side and the second layer on the upper side. The average thickness T of the first layer ml 3 to 17 nm, the first layer has an average composition of (Ti 1-ρ Si ρ )N composite nitride layer, wherein 0.10≤ρ≤0.40, 1.0≤p / ρ≤1.2, The average thickness T of the second layer mu The thickness of the second layer is 2 to 12 nm, and the second layer is a complex nitride layer having the same average composition as that of the lower layer.

2. The surface-coated cutting tool according to claim 1, wherein: The average thickness T of the lower layer l and the average thickness T of the upper layer u 0.2≤T u / T l ≤9.0.

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