Surface coated cutting tools

Abstract

A surface-coated cutting tool having a coating layer in which: a lower layer thereof is a composite nitride layer having an average thickness of 0.1 to 5.0 μm and an average composition of (Al1-a-bTiaCrb)N (0.10 < a ≤ 0.55, 0.05 ≤ b < 0.20, 0.40 ≤ (1-a-b) ≤ 0.70); an upper layer thereof is a composite nitride layer having an average thickness of 0.1 to 5.0 μm and an average composition of (Ti1-pSip)N (0.10 ≤ p ≤ 0.40); and an intermediate layer thereof has an average thickness of 10 to 500 nm, includes two or more stacked units containing a first layer and a second layer, the first layer being a composite nitride layer having an average thickness of 3 to 17 nm and an average composition of (Ti1-ρSiρ)N (0.10 ≤ ρ ≤ 0.40, 1.0 ≤ p / ρ ≤ 1.2), and the second layer being a composite nitride layer having an average thickness (Tmu) of 2 to 12 nm and 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, a Japanese patent application filed on February 13, 2023. All the descriptions described in the Japanese application are incorporated herein by reference.

Background Art

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

[0003] Patent Document 1 discloses a coated tool in which the coating layer includes an alternating layer in which one or more layers of an A layer and a B layer are alternately laminated, the A layer is composed of a nitride containing Al and Cr, and when the total number of metal atoms constituting the A layer is 1, the atomic ratio of Cr is greater than 0 and not more than 0.4, the B layer is composed of a nitride containing Ti and Si and not containing Al, and when the total number of metal atoms constituting the B layer is 1, the atomic ratio of Si is 0.05 or more and 0.3 or less. The coated tool is said to have oxidation resistance and adhesion resistance even at high temperatures during cutting and suppress chipping of the cutting edge.

[0004] Patent Document 2 discloses that the coating layer contains Al a Ti b Cr cA coated tool is described, comprising an I layer made of nitride or carbonitride (0.3≦a≦0.7, 0≦b≦0.5, 0≦c≦0.7, a+b+c=1) and a II layer which is a composite layer in which a nitride phase made of CrAlN and a BN phase are three-dimensionally mixed, wherein the I layer is provided on the surface of the substrate and the II layer is the outermost layer, with two or more layers of the I and II layers stacked alternately, the average thickness of both the I and II layers exceeding 50 nm, and the total average thickness of the coating layer being 0.1 to 20 μm, and the coating layer is said to have excellent heat resistance, chemical stability at high temperatures, abrasion resistance, and welding resistance.

[0005] Patent Document 3 describes a coated tool having a coating layer comprising a layer A formed on a substrate and a layer B formed directly above layer A, wherein layer A is a Si-free film of TiAlCr nitride, oxynitride, carbonitride, or oxycarbonitride, composed of fine columnar crystals with a cubic crystal structure, and the width of each columnar crystal in a direction substantially perpendicular to the growth direction of the columnar crystals is formed to be 300 nm or less, and layer B is a Si-containing film mainly composed of SiTi nitride, and the coated tool is said to have wear resistance and durability.

[0006] Patent Document 4 describes a coated tool having a first layer in which multiple layers of a first film made of Si-containing nitride and a second film made of AlCr-containing nitride are alternately laminated, and a second layer of Si-containing nitride laminated on the surface of the first layer and having a greater thickness than the first and second films, and the coated tool is said to have high hardness due to the refinement of the crystals in the coated layer.

[0007] Patent Document 5 describes a coated tool in which the coating layer comprises an adhesive layer in contact with the substrate and an upper layer formed on the adhesive layer, the upper layer comprises TiAlN, TiAlSiN, or TiSiN, the thickness of the adhesive layer is 2 nm to 20 nm and comprises Cr, Ti, Al, W, C, and N (but not Co), and the coated tool is said to have excellent durability.

[0008] Patent Document 6 discloses that a coating layer includes a lower coating layer, an upper coating layer, and an intermediate coating layer formed between the two. The intermediate coating layer is composed of an alternating laminate in which one or more layers of a first layer made of a nitride or carbonitride of Al, Cr, and Ti and a second layer made of a nitride or carbonitride of Ti and Si are alternately laminated. The composition of the metal components of the first layer is (Al x Cr y Ti z )(x + y + z = 100, 50 ≤ x ≤ 65, 20 ≤ y ≤ 30, 5 ≤ z ≤ 20), and the composition of the metal components of the second layer is (Ti a Si b )(a + b = 100 、 80 ≤ a ≤ 90, 10 ≤ b ≤ 20). The coating tool is described as having crack resistance and peeling resistance.

[0009] Patent Document 7 discloses that a coating layer includes a first layer composed of Ti m Si 1-m N 1-a-b C a B b and a second layer composed of Al x Cr y M 1-x-y N 1-a-b C a B b alternately laminated. In the first layer, 0.7 ≤ m < 1 and 0 < 1 - a - b ≤ 1. In the second layer, 0.7 < x ≤ 0.8, 0 < y, and 0 < 1 - a - b ≤ 1. M is at least one selected from the group consisting of Ti, V, Zr, Nb, Mo, Ta, W, Y, and lanthanoids (excluding Pm). The coating tool is described as having improved wear resistance.

Prior Art Documents

Patent Documents

[0010]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Summary of the Invention

Problems to be Solved by the Invention

[0011] The present invention has been made in view of the above circumstances and proposals, and an object thereof is to provide a coated tool having excellent durability even when used for high-speed cutting of difficult-to-machine materials such as Ni-based alloys.

Means for Solving the Problems

[0012] The surface-coated cutting tool according to an embodiment of the present invention has a substrate and a coating layer provided on the substrate, The coating layer has a lower layer, an intermediate layer, and an upper layer in order from the surface of the substrate toward the surface of the tool, and the sum of the average thicknesses of the lower layer and the upper layer is 1.0 to 8.0 μm. surface coating cutting The lower layer has an average thickness (T ) of 0.1 to 5.0 μm, and its average composition is a composite nitride layer of (Al l )N(0.10 < a ≤ 0.55, 0.05 ≤ b < 0.20, 0.40 ≤ (1 - a - b) ≤ 0.70), 1-a-b Ti a Cr b b The upper layer has an average thickness (T u ) of 0.1 to 5.0 μm, and its average composition is a composite nitride layer of (Ti 1-p Si p )N(0.10 ≤ p ≤ 0.40), The intermediate layer has an average thickness (T m ) of 10 to 500 nm, and has two or more stacking units including a first layer on the lower layer side and a second layer on the upper layer side. The first layer has an average thickness (T ml ) has a wavelength of 3-17 nm, and its average composition is (Ti 1-ρ Si ρ It is a composite nitride layer with N(0.10≦ρ≦0.40, 1.0≦p / ρ≦1.2), The second layer has an average thickness (T mu The composite nitride layer has a thickness of 2 to 12 nm and the same average composition as the lower layer.

[0013] The surface-coated cutting tool according to the above embodiment may satisfy the following item (1).

[0014] (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 The value must be ≤ 9.0. [Effects of the Invention]

[0015] According to the above, surface-coated cutting tools have excellent durability even when used for high-speed cutting of difficult-to-machine materials such as Ni-based alloys. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic diagram of a longitudinal cross-section of a coating layer according to one embodiment of the present invention. [Modes for carrying out the invention]

[0017] The inventors focused on a coating layer formed by laminating nitrides containing Al, Ti, and Cr, which both have excellent durability, and nitrides containing Ti and Si, and conducted extensive research. As a result, they discovered that the aforementioned objective can be achieved by making the intermediate layer of this coating layer a laminated structure, devising its composition, and setting its thickness within a predetermined range.

[0018] The following describes in detail an embodiment of the present invention based on this finding. In this specification and in the claims, when a numerical range is expressed as "L~M" (where L and M are both numerical values), the range includes an upper limit (M) and a lower limit (L). If a unit is specified only for the upper limit, the units of the upper limit (M) and the lower limit (L) are the same. Furthermore, each numerical value includes measurement error.

[0019] Furthermore, the term "surface of the substrate" as used in this specification and in the claims refers to the average line (straight line) of the roughness curve at the interface between the coating layer closest to the substrate surface and the substrate, calculated arithmetically. According to this method for calculating the average line, even if the substrate has a curved surface, if the tool diameter (diameter of the substrate) is sufficiently large relative to the thickness of the coating layer, the interface between the coating layer and the substrate can be treated as a plane, and thus the surface of the substrate can be determined in the same manner.

[0020] Longitudinal cross-section of a coating tool according to one embodiment of the present invention (substrate) surface Figure 1 shows a schematic diagram of a cross-section perpendicular to the substrate surface (ignoring minute irregularities and considering the substrate surface as a plane).

[0021] As is clear from Figure 1, the covering layer (8) has 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 has two or more stacking units (6) that include the first layer (4) on the lower side and the second layer (5) on the upper side. Note that stacking units including the first and second layers also exist in the white areas within the region indicated as the intermediate layer. The following is a description of each layer in order.

[0022] 1.Lower layer The lower layer is located directly above the base. Average thickness of the lower layer (T l The thickness is preferably 0.1 to 5.0 μm. This range is preferred because, below 0.1 μm, the wear resistance and fracture resistance of the underlying layer are insufficient, while above 5.0 μm, the internal strain of the underlying layer increases, making the underlying layer prone 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. μm That is the case.

[0023] The lower layer is So with 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 - a - b) ≤ 0.70), and it is preferably a composite nitride layer. The reasons why it is preferable for a and b to satisfy the above ranges are as follows.

[0024] If a exceeds 0.10 and b is not more than 0.05, the effect of improving toughness by providing a composite nitride with a different lattice constant directly above the lower layer cannot be exerted. Also, if a exceeds 0.55, the durability of the coated tool decreases due to a decrease in the Al content ratio, and if b is 0.20 or more, the lower layer becomes soft and the wear resistance decreases. Furthermore, if (1 - a - b) is less than 0.40, the high-temperature hardness and high-temperature oxidation resistance of the lower layer decrease, while if it exceeds 0.70, columnar crystals with a hexagonal crystal structure are formed, resulting in a decrease in the hardness of the lower layer and an inability to obtain sufficient wear resistance. More preferable values are a of 0.15 to 0.55, b of 0.05 to 0.15, and (1 - a - b) of 0.50 to 0.65. Even more preferable values are a of 0.20 to 0.37, b of 0.08 to 0.15, and (1 - a - b) of 0.55 to 0.65.

[0025] Here, according to an example of the manufacturing method described later, the ratio of (Al 1-a-b Ti a Cr b ) to N is manufactured to be 1:1, but there may be cases where it does not become 1:1 unintentionally. This is the same for other composite nitrides described below.

[0026] 2. Upper layer The upper layer is provided directly above the intermediate layer described later and is located on the surface of the coating layer. The average thickness of the upper layer (T uThe thickness is preferably 0.1 to 5.0 μm. This range is preferable because if it is less than 0.1 μm, the wear resistance of the upper layer decreases, while if it exceeds 5.0 μm, chipping and chipping of the upper layer becomes more likely. A more preferable average thickness is 0.2 to 4.0 μm, and an even more preferable average thickness is 0.3 to 3.6 μm.

[0027] Average thickness of the upper layer (T u ) and the average thickness of the lower layer (T l The sum of the upper and lower layers is preferably 1.0 to 8.0 μm. This is because if it is less than 1.0 μm, the coating layer will not be able to exhibit excellent abrasion resistance over long-term use, while if it exceeds 8.0 μm, the upper layer is prone to abnormal damage such as chipping, chipping, 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.

[0028] Also, 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 A value of ≤9.0 is more preferable. The reason is as follows: Below 0.2, the abrasion resistance and oxidation resistance of the upper layer may not be sufficiently exhibited, 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 excessive, which may cause self-destruction or delamination. u / T l More preferably, 0.2 ≤ T u / T l The value is ≤ 4.0.

[0029] The upper layer has an average composition of (Ti 1-p Si pIt is preferable that the composite nitride layer has a p-value of N(0.10≦p≦0.40). The reason why it is preferable for p to satisfy this range is as follows: If p is less than 0.10, the oxidation resistance and lubricity due to the addition of Si cannot be achieved. On the other hand, if it exceeds 0.40, the residual stress becomes excessively large, causing chipping in the upper layer. A more preferable range for p is 0.10 to 0.30, and an even more preferable range is 0.15 to 0.25.

[0030] 3. Middle class The intermediate layer is located directly above the lower layer and directly below the upper layer. The intermediate layer has two or more stacking units, which include the first layer on the lower side and the second layer on the upper side.

[0031] The first layer on the lower side has an average composition of (Ti 1-ρ Si ρ It is preferable that the composite nitride layer has N(0.10≦ρ≦0.40, 1.0≦p / ρ≦1.2). The reason is that when this range is satisfied, the lattice strain in the intermediate layer becomes small, and the adjacent upper layer Layer unit Although adhesion to the upper layer improves, if p / ρ is less than 1.0 or greater than 1.2, the range of change in composition with the upper layer becomes large, and a rapid change in Si content occurs, which reduces the chipping resistance of the intermediate layer.

[0032] The upper second layer has the same average composition as the lower layer, i.e., the same values ​​as a and b of the lower layer (Al 1-a-b Ti a Cr b )N( 0.10 It is preferable that the composite nitride layer has the following properties: ≤ a, 0.05 ≤ b < 0.20, 0.40 ≤ (1-ab) ≤ 0.70. This is because having the same average composition as the lower layer prevents residual stress from concentrating in the intermediate layer, thereby improving the adhesion between the lower and upper layers.

[0033] Average thickness of the first layer on the lower side (T ml ) is 3-17nm, the average thickness of the upper second layer (T mu) is preferably 2 to 12 nm. The reason is that if this range is satisfied, the upper layer Layer unit and the lower level Layer unit This is because the constituent crystal grains become finer, increasing the grain boundary area, which suppresses plastic deformation and crack propagation at the grain boundaries.

[0034] Also, 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 The sum of the values ​​is more preferably between 5 and 20 nm. Within this range, the aforementioned objectives are more reliably achieved.

[0035] The average thickness of the intermediate layer is preferably 10 to 500 nm. The reason for this is unclear, but if it is less than 10 nm, the adhesion between the lower and upper layers is not sufficiently improved, while if it exceeds 500 nm, the lower layer side Layer unit It is presumed that the magnitude of residual stress makes it easier for cracks to form in the intermediate layer, which in turn leads to a decrease in adhesion. A more preferable average thickness is 10-450 nm, an even more preferable average thickness is 10-250 nm, and the most preferable average thickness is 20-150 nm.

[0036] To ensure the average thickness of the intermediate layer is within the preferred range, it is preferable to stack 2 to 100 stacking units. With this range of stacking units, cracks are less likely to occur within the coating layer, improving chipping resistance. More preferably, the number of stacking units is 5 to 50, and even more preferably 6 to 20.

[0037] 4. Other layers ( 4 -1) Layers that may exist While the aforementioned problems can be adequately solved with just the lower, middle, and upper layers, a surface layer may also be selectively added in addition to these layers.

[0038] surface layer The surface layer can be exemplified by a TiN layer. Since the TiN layer has a golden hue, it can be used as an identification layer to determine, for example, whether a coated tool is unused or used by observing the change in the color tone of the tool's surface. The average thickness of this TiN layer, which serves as the identification layer, can be, for example, 0.1 to 1.0 μm.

[0039] ( 4 -2) Layers that may occur by chance In this embodiment, the film is deposited so that only the lower layer, intermediate layer, upper layer, and surface layer exist. However, when changing the type of layer to be deposited, pressure changes and temperature fluctuations may occur unintentionally, and layers with different compositions from these layers may be formed (unintentionally) by chance between them. These layers are called layers that may occur by chance.

[0040] 5 .Substrate (1)Material The substrate used in this embodiment can be any known substrate material, as long as it does not hinder the achievement of the aforementioned objectives. For example, cemented carbide (WC-based cemented carbide, including those containing WC and Co, and further containing carbonitrides such as Ti, Ta, and Nb), cermet (for example, those mainly composed of TiC, TiN, and TiCN), ceramics (for example, titanium carbide, silicon carbide, silicon nitride, aluminum nitride, and aluminum oxide), cBN sintered body, or diamond sintered body.

[0041] (2) Shape The shape of the base material is not particularly restricted as long as it is a shape that can be used as a cutting tool; examples include the shape of an insert, the shape of an end mill, and the shape of a drill.

[0042] 6 .Measurement method A focused ion beam (FIB) instrument was used to cut out a longitudinal section (a section perpendicular to the substrate surface, assuming that there are no minute irregularities on the substrate surface), and a scanning electron microscope (SEM) was used to measure the thickness of each layer at five locations (the observation magnification should be any magnification that allows for thickness measurement; 5,000 to 200,000x for the thickness measurement of the lower layer, upper layer, and the entire coating layer, and 5,000 to 200,000x for the intermediate layer, the upper layer stacking unit layer and the upper layer Layer unit The thickness measurement is performed at a magnification of 100,000 to 500,000 times, and the average value is taken as the average thickness of each layer (if only one layer exists, the average thickness is taken by averaging the results of measurements taken at 5 locations on this layer). In addition, the component composition of the lower, middle, and upper layers is measured at 5 locations on each layer using energy-dispersive X-ray spectroscopy (EDS) attached to the SEM, and the average composition is calculated from the average value.

[0043] 7 .Manufacturing method The coating layer of this embodiment can be manufactured, for example, by the following PVD method. Specifically, the AIP (Arc Ion Plating) apparatus is subjected to a nitrogen atmosphere, and an arc discharge is generated between an Al-Ti-Cr alloy target of a predetermined composition and an anode electrode to form a lower layer of a predetermined average thickness. Next, an arc discharge is generated between a Ti-Si alloy target of a predetermined composition and an anode electrode, also in a nitrogen atmosphere, to deposit a first lower layer of a predetermined average thickness. Subsequently, an arc discharge is generated between the Al-Ti-Cr alloy target and the anode electrode to deposit a second upper layer of a predetermined average thickness, forming a stacked unit. After depositing two or more predetermined stacked units, an arc discharge is generated between another Ti-Si alloy target of a predetermined composition and an anode electrode, also in a nitrogen atmosphere, to deposit an upper layer of a predetermined average thickness.

[0044] The above description includes the following features. (Note 1) A substrate and a surface having a coating layer provided on the substrate. Covering A cutting tool, The coating layer is from the surface of the substrate surface coating cutting It has a lower layer, an intermediate layer, and an upper layer in order toward the surface of the tool, and the sum of the average thicknesses of the lower layer and the upper layer is 1.0 to 8.0 μm. The lower layer has an average thickness (T l ) of 0.1 to 5.0 μm, and its average composition is (Al 1-a-b Ti a Cr b )N (0.10 < a ≦ 0.55, 0.05 ≦ b < 0.20, 0.40 ≦ (1 - a - b) ≦ 0.70), and it is a composite nitride layer. The upper layer has an average thickness (T u ) of 0.1 to 5.0 μm, and its average composition is (Ti 1-p Si p )N (0.10 ≦ p ≦ 0.40), and it is a composite nitride layer. The intermediate layer has an average thickness (T m ) of 10 to 500 nm, and has two or more stacking units including a first layer on the lower layer side and a second layer on the upper layer side. The first layer has an average thickness (T ml ) of 3 to 17 nm, and its average composition is (Ti 1-ρ Si ρ )N (0.10 ≦ ρ ≦ 0.40, 1.0 ≦ p / ρ ≦ 1.2), and it is a composite nitride layer. The second layer has an average thickness (T mu ) of 2 to 12 nm, and is a composite nitride layer having the same average composition as the lower layer. A surface-coated cutting tool characterized by the above. (Appendix 2) The average thickness (T l ) of the lower layer and the average thickness (T u ) of the upper layer satisfy 0.2 ≦ T u / T l ≦ 9.0. The surface-coated cutting tool according to Appendix 1, characterized by the above. (Appendix 3) The surface-coated cutting tool according to Appendix 1 or 2, characterized by having two or more and 100 or less of the stacking units. (Appendix 4) The sum of the average thickness (T ml ) of the first layer and the average thickness (T mu ) of the second layer is5~20 Surface-coated cutting tools as described in any of the appendices 1 to 3, in nm. [Examples]

[0045] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0046] As raw material powders, WC powder, TiC powder, VC powder, TaC powder, NbC powder, Cr3C2 powder, and Co powder were prepared. These raw material powders were blended according to the composition shown in Table 1, wax was added, and the mixture was wet-mixed in a ball mill for 72 hours. After vacuum drying, the mixture was press-molded at a pressure of 100 MPa to form a compacted powder body, which was then sintered to form a sintered round bar body for base formation with a diameter of 6 mm. Subsequently, by grinding, end mill bases 1 to 4 made of WC-based cemented carbide were manufactured, each having a groove forming section with dimensions of 6 mm diameter × 60 mm and a two-blade shape with a helix angle of 45 degrees.

[0047] Then, each of the end mill bases 1 to 4 was ultrasonically cleaned in acetone and dried.

[0048] An end mill base was mounted along the outer circumference of the rotary table of the AIP device at a predetermined radial distance from the central axis. A target (cathode electrode) made of an Al-Ti-Cr alloy of a predetermined composition was placed on one side of the AIP device, and targets (cathode electrodes) made of two types of Ti-Si alloys of predetermined compositions were placed on the other side.

[0049] Next, the AIP device is evacuated to create a vacuum (1 × 10⁻⁶). -3 While maintaining a temperature of Pa or less, the AIP apparatus was heated to 500°C by a heater, and then a DC bias voltage of -400V was applied to the end mill base rotating on the rotary table, and Ar ion bombardment was performed for 15 minutes using an ion source produced by thermionic emission from the filament.

[0050] Furthermore, a coating layer was formed on the end mill bases 1 to 4 by the following process, and surface-coated end mills 1 to 18 (hereinafter referred to as Examples 1 to 18) were manufactured, respectively.

[0051] Manufacturing of the coating layer The coating layers of the examples shown in Table 3 were manufactured by the following steps 1) to 5).

[0052] 1) Film formation in the lower layer Introducing nitrogen gas as a reaction gas into the apparatus to the lower layer shown in Table 2 Film deposition conditions The nitrogen partial pressure was set as shown, the temperature of the end mill substrate rotating on the rotary table was maintained at the temperature shown in Table 2, the DC bias voltage shown in Table 2 was applied, and an arc discharge was generated by passing a current of 150 A between the Al-Ti-Cr alloy target and the anode electrode, thereby depositing a lower layer with the composition and average thickness shown in Table 3 onto the surface of the end mill substrate.

[0053] 2) Deposition of the first layer on the lower side Next, the nitrogen partial pressure is set as shown in Table 2 as the film deposition conditions for the lower first layer, the temperature of the end mill substrate rotating on the rotary table is maintained at the temperature shown in Table 2, the DC bias voltage shown in Table 2 is applied, and an arc discharge is generated by passing a current of 100A between the Ti-Si alloy target and the anode electrode, thereby the lower layer A first layer on the lower side, with the composition and average thickness shown in Table 3, was deposited onto the surface.

[0054] 3) Deposition of the second layer on the upper side The nitrogen partial pressure for the upper second layer was set as shown in Table 2, the temperature of the end mill substrate rotating on the rotary table was maintained at the temperature shown in Table 2, the DC bias voltage shown in Table 2 was applied, and an arc discharge was generated by passing a current of 150A between the Al-Ti-Cr alloy target and the anode electrode, thereby depositing the upper second layer with the composition and average thickness shown in Table 3.

[0055] 4) Film formation of the laminated layer As described in 2) and 3) above, a stacking unit was formed, and the operations described in 2) and 3) above were repeated to form a predetermined number of stacking units.

[0056] 5) Deposition of the upper layer Finally, the nitrogen partial pressure is set to the upper layer deposition conditions shown in Table 2, the temperature of the end mill substrate rotating on the rotary table is maintained at the temperature shown in Table 2, the DC bias voltage shown in Table 2 is applied, and an arc discharge is generated by passing a current of 100A between the Ti-Si alloy target of a predetermined composition and the anode electrode, thereby achieving the above Middle class An upper layer with the composition and average thickness shown in Table 3 was deposited onto the surface.

[0057] For comparison, each of the end mill bases 1 to 4 was ultrasonically cleaned in acetone, dried, and mounted along the outer circumference at a predetermined radial distance from the central axis on the rotary table of the AIP apparatus. The bombardment process was carried out in the same manner as in Examples 1 to 18, and comparative surface coated end mills 1' to 19' (hereinafter referred to as Comparative Examples 1' to 19') were manufactured according to the film formation conditions 1' to 19' shown in Table 2.

[0058] For Examples 1 to 18 and Comparative Examples 1' to 19' manufactured as described above, the average thickness and average composition were determined using the method described above. Furthermore, Layer unit The number of layers was calculated from the ratio of the thickness of the intermediate layer to the thickness of the base layer. Table 3 shows the measured and calculated values. 。

[0059] [Table 1]

[0060] [Table 2]

[0061] [Table 6]

[0062] In Tables 1 and 3, "-" indicates that there is no matching entry.

[0063] Next, cutting tests were performed on Examples 1-18 and Comparative Examples 1'-19' under the following cutting conditions, and the flank wear width was measured. The results are shown in Table 4.

[0064] <Cutting conditions> Work material: Ni-based heat-resistant alloy plate (Cr18 mass%-Fe18 mass%-Nb5 mass%-Mo3 mass%-Ti1 mass%-Al0.5 mass%-Al0.5 mass%-Ni remainder) with planar dimensions 75 mm x 150 mm and thickness 250 mm. Cutting speed: 100m / min. Feed rate: 0.05mm / tooth Depth of cut: AP 2.4mm, ae 0.3mm Cutting length: 50m Cutting fluid: Water-soluble coolant

[0065] [Table 4]

[0066] In Table 4, the "*" indicates the time at which the substrate is exposed and the cut length reaches 50m before the end of service life, based on abnormal noises detected every minute due to damage to the coating layer, presumably caused by peeling, welding, chipping, wear, etc.

[0067] As is clear from Table 4, Examples 1 to 18 all exhibited small flank wear width and good durability, while Comparative Examples 1' to 19' all had large flank wear width and reached the end of their service life before reaching the cutting length in the cutting test.

[0068] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the claims rather than by the embodiments described herein, and all modifications within the scope are intended to be included in the meaning of equivalences of the claims. [Explanation of Symbols]

[0069] 1 base body 2 Lower layer 3. Middle Class 4. The first layer on the lower side 5. The second layer on the upper side 6 Layer Units 7 Upper layer 8 Covering layer

Claims

1. A surface-coated cutting tool having a substrate and a coating layer provided on the substrate, The coating layer has a lower layer, an intermediate layer, and an upper layer in order from the surface of the substrate toward the surface of the surface-coated cutting tool, and the sum of the average thicknesses of the lower layer and the upper layer is 1.0 to 8.0 μm. The aforementioned lower layer has an average thickness (T ｌ ) is 0.1 to 5.0 μm, and its average composition is (Al １－ａ－ｂ Ti ａ Cr ｂ The composite nitride layer is N(0.10 < a ≤ 0.55, 0.05 ≤ b < 0.20, 0.40 ≤ (1 - a - b) ≤ 0.70), The aforementioned upper layer has an average thickness (T ｕ ) is 0.1 to 5.0 μm, and its average composition is (Ti １－ｐ Si ｐ It is a composite nitride layer with N(0.10 ≤ p ≤ 0.40), The aforementioned intermediate layer has an average thickness (T ｍ The wavelength is 10 to 500 nm, and the stacking unit has two or more layers, including the lower first layer and the upper second layer. The first layer has an average thickness (T ｍｌ ), which is 3 to 17 nm, and its average composition is (Ti １－ρ Si ρ )N (0.10 ≤ ρ ≤ 0.40, 1.0 ≤ p / ρ ≤ 1.2), and is a composite nitride layer, The second layer has an average thickness (T ｍｕ ) is a composite nitride layer having a density of 2 to 12 nm and the same average composition as the lower layer. A surface-coated cutting tool characterized by the following features.

2. 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 A surface-coated cutting tool according to claim 1, characterized in that the coefficient is ≤ 9.0.

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