Surface-coated cutting tool

Abstract

To provide a surface-coated cutting tool having durability even in high-speed intermittent cutting of hard-to-cut materials including Ti-based alloys and Ni-based alloys.SOLUTION: A surface-coated cutting tool comprising a substrate and a coating layer on the substrate, the coating layer being formed by alternately laminating an A layer and a B layer each having an average thickness of 2 nm or more and 50 nm or less, wherein an average composition of the A layer is (Ti1-xLx)Bz, an average composition of the B layer is (Ti1-yLy)Bw, L is at least one lanthanoid element, 0.01≤y-x≤0.10, y≤0.20, 1.5≤z≤3.0, and 1.5≤w≤3.0.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool).

Background Art

[0002] Conventionally, as a coated tool, for example, a coated tool in which a coating layer is formed on a substrate such as a tungsten carbide (hereinafter represented by WC) - based cemented carbide is known. And, by adjusting the composition, structure, crystal structure, etc. of this coating layer, proposals have been made to obtain a coating layer with improved cutting performance, including cutting of difficult-to-cut materials such as Ti - based alloys and Ni - based alloys.

[0003] For example, Patent Document 1 describes a coated tool having a coating layer containing one or more TiB2 layers on a substrate, and the coating layer exhibits a hardness of 50 GPa or more and a (001) plane orientation.

[0004] Patent Document 2 describes a coated tool in which the coating layer is Ti 1-x M x B y (M is one or more elements of Groups 4 to 6 of the periodic table, 0.05 ≦ x ≦ 0.50, 1.0 ≦ y ≦ 2.5), where x repeatedly changes in the thickness direction, and the difference between the average value of the maximum value and the average value of the minimum value of x and the average interval between the maximum value and the minimum value are each a predetermined value. The coated tool is said to have excellent crack resistance and wear resistance even when used for cutting Ti - based alloys.

[0005] Patent Document 3 describes a coated tool in which the coating layer contains a composite boride layer of Ti and a lanthanoid element, and the coated tool is said to have excellent wear resistance and chipping resistance even when used for high - speed and high - efficiency machining of difficult - to - cut materials such as Ti - based alloys.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention has been made in view of the above circumstances and proposals, and an object thereof is to provide a surface-coated cutting tool having durability even in high-speed interrupted cutting of difficult-to-machine materials such as Ti-based alloys and Ni-based alloys.

[0008] The surface-coated cutting tool according to an embodiment of the present invention has a substrate and a coating layer on the substrate, the coating layer is formed by alternately laminating an A layer and a B layer each having an average thickness of 2 nm or more and 50 nm or less, the average composition of the A layer is (Ti 1-x L x )B z and the average composition of the B layer is (Ti 1-y L y )B w where L is one or more lanthanoid elements, 0.01 ≦ y - x ≦ 0.10, 0.01 ≦ y ≦ 0.20, 1.5 ≦ z ≦ 3.0, 1.5 ≦ w ≦ 3.0 is satisfied.

[0009] The surface-coated cutting tool according to the above embodiment may satisfy the following item (1). (1) When the coating layer is analyzed by X-ray, the X-ray intensity corresponding to the (001) plane is the maximum.

Advantages of the Invention

[0010] The above surface-coated cutting tool has excellent durability even in high-speed interrupted cutting of difficult-to-machine materials such as Ti-based alloys and Ni-based alloys.

Brief Description of the Drawings

[0011]

Figure 1

Embodiments for Carrying Out the Invention

[0012] The present inventor has studied a coating layer for a coated tool having a metal boride. As a result, the following matters have been recognized and found.

[0013] (1) The coating layer having TiB2 has a non-affinity for Ti alloys, Ni-based alloys, etc., and has excellent wear resistance due to its high hardness.

[0014] (2) In order to improve the durability of the coating layer having TiB2, when a composite boride layer of Ti and a lanthanoid element is used as the coating layer in addition to Ti, the heat resistance is improved and it has durability for high-speed and high-efficiency machining of difficult-to-cut materials such as Ti-based alloys and Ni-based alloys. However, further improvement in durability is desired in high-speed interrupted machining.

[0015] (3) In order to improve the durability for this high-speed interrupted cutting process, it is preferable that the coating layer is a two-layer structure in which at least one layer is a composite boride layer of Ti and a lanthanoid element and the two layers are alternately laminated.

[0016] The present invention has been derived based on these recognitions and findings, and hereinafter, the coated tool according to the embodiment of the present invention will be described in detail. In this specification and the claims, when a numerical range is expressed as "L to M" (both L and M are numerical values), the range includes the upper limit value (M) and the lower limit value (L). When there is no description of the unit of the lower limit value and only the unit of the upper limit value is described, the units of the upper limit value (M) and the lower limit value (L) are the same.

[0017] 1. Coating layer Fig. 1 shows a schematic diagram of an example of a longitudinal section of a surface-coated cutting tool according to an embodiment of the present invention. As is apparent from Fig. 1, the surface-coated cutting tool according to this embodiment has a coating layer (2) on a substrate (1). The coating layer (2) has an alternating laminate (3) of metal boride layers. The alternating laminate (3) of metal borides is formed by alternately laminating an A layer (4) and a B layer (5). The A layer (4) and the B layer (5) are also alternately laminated in the blank portion of Fig. 1. Further, the coating layer (2) in Fig. 1 has an underlayer (6) and a surface layer (7) in addition to the alternating laminate (3). However, both the underlayer (6) and the surface layer (7) may be selectively provided and are not essential. Note that the longitudinal section is, in the case of an insert, a cross section perpendicular to the substrate when the surface of the substrate is considered as a plane without unevenness on the surface of the substrate, and in the case of a shaft tool, a cross section perpendicular to the axis.

[0018] (1) Metal boride layer (1-1) Alternating laminate The metal boride layer is formed by alternately laminating an A layer and a B layer (details of the A layer and the B layer will be described later) (hereinafter sometimes referred to as an alternating laminate), and its average thickness is preferably 0.2 μm or more and 10.0 μm or less. The reason is that when the average thickness of the alternating laminate is less than 0.2 μm, the wear resistance may not be sufficiently exhibited. On the other hand, when it exceeds 10.0 μm, defects may easily occur. The average thickness of the alternating laminate is more preferably 1.0 μm or more and 4.0 μm or less. Note that as long as the A layer and the B layer are alternately laminated in the alternating laminate, both the layer closest to the substrate side and the layer closest to the tool surface side of the alternating laminate may be either the A layer or the B layer.

[0019] (1-2) Average thickness of each of the A layer and the B layer The average thicknesses of the A layer and the B layer constituting the alternating laminate are both preferably 2 nm or more and 50 nm or less. Note that the average thicknesses of the A layer and the B layer may be the same or different. The reason why the average thickness within this range is preferable is as follows. If it is less than 2 nm, the crystal grains constituting the alternating laminate become too small, and chipping is likely to occur. On the other hand, if it exceeds 50 nm, the alternating laminate cannot ensure sufficient hardness.

[0020] (1-2) Average composition of layer A and layer B When the average composition of layer A is (Ti 1-x L x )B z and the average composition of layer B is (Ti 1-y L y )B w (where L is one or more lanthanoid elements), it is preferable that 0.01 ≦ y - x ≦ 0.10, 0.01 ≦ y ≦ 0.20, 1.5 ≦ z ≦ 3.0, and 1.5 ≦ w ≦ 3.0. The reasons are as follows.

[0021] If y - x is less than 0.01, the strain existing within the alternating laminate is small, and the alternating laminate does not have sufficient hardness. On the other hand, if it exceeds 0.10, the strain existing within the alternating laminate becomes too large, and local stress occurs in the coating layer, making it easy for cracks and chipping to occur. Also, if y exceeds 0.20, the hardness and toughness of the metal boride layer decrease, making chipping and defects likely to occur.

[0022] More preferably, 0.00 ≦ x ≦ 0.10 and 0.01 ≦ y ≦ 0.15. If x and y are within this range, even in high-speed cutting of difficult-to-machine materials such as Ti-based alloys and Ni-based alloys, more excellent heat resistance and wear resistance can be exhibited.

[0023] Also, when z and w are less than 1.5, the non-affinity with the workpiece decreases, and sufficient weld resistance of the coating layer cannot be exhibited. If it exceeds 3.0, the hardness of the metal boride layer decreases, and wear progresses early.

[0024] Further, when subjected to X-ray analysis, it is more preferable that the metal boride layer has the maximum X-ray intensity corresponding to the (001) plane. The reason is that when the intensity of the (001) plane is maximum, sufficient film hardness and film toughness can be maintained.

[0025] (3) Other Layers The aforementioned object can be achieved only by alternately laminating the A layer and the B layer, both of which are metal boride layers. Further, an underlayer may be provided between the substrate and the metal boride layer, and a surface layer may be provided on the surface of the metal boride layer.

[0026] (3-1) Underlayer An underlayer may be provided which is composed of one or two or more Ti compound layers selected from a Ti carbide layer, a Ti nitride layer, a Ti carbonitride layer, and a Ti carbon oxynitride layer (the composition of these Ti compound layers is not limited to a stoichiometric composition) and has a total average layer thickness of 0.1 to 10.0 μm. The underlayer improves the adhesion between the coating layer including the alternating lamination and the substrate.

[0027] (3-2) Surface Layer A surface layer may be selectively provided on the alternating lamination. As the surface layer, a TiN layer (the atomic ratio of Ti and N in the TiN layer is not limited to a stoichiometric one) may be provided. When this TiN layer is provided, since the TiN layer itself has a golden color tone, for example, it can be utilized as a discrimination layer for discriminating whether the coated tool is unused or used by the change in color tone. The average thickness of the TiN layer as this discrimination layer may be, for example, 0.1 to 1.0 μm. Further, the surface layer may be an Al2O3 layer. The average thickness of this Al2O3 layer may be 0.1 to 15.0 μm.

[0028] (3-3) Unintended Layer In this embodiment, the film is formed so that there are no layers other than the alternating lamination of the A layer and the B layer, the underlayer, and the surface layer. However, fluctuations in the pressure in the film forming apparatus or the like may occur unintentionally, and layers of an unintended composition different from that of the alternating laminated metal boride layer, the underlayer, and the surface layer may be formed.

[0029] 2. Substrate (1) Material As long as the material of the substrate used in this embodiment is a known one and does not inhibit the achievement of the above-mentioned object, any material can be used. For example, cemented carbide (WC-based cemented carbide, including WC and those containing Co and further added with carbonitrides such as Ti, Ta, Nb, etc.), cermet (mainly composed of TiC, TiN, TiCN, etc.), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide), cBN sintered body, or diamond sintered body.

[0030] (2) Shape The shape of the substrate is not particularly restricted as long as it is a shape used as a cutting tool, and examples include the shape of an insert and the shape of a drill.

[0031] 3. Measuring method[[ID= sixteen]] The average compositions of the A layer and the B layer constituting the coating layer and the average thicknesses of the A layer, the B layer, the lower layer, and the surface layer are measured as follows.

[0032] (1) Average composition A sample for observation is prepared by cutting the coating layer in a longitudinal section at an arbitrary position. This sample can be prepared using, for example, a focused ion beam system (FIB) or a cross section polisher (CP). Hereinafter, measurements are performed on this sample for observation.

[0033] The average compositions of the A layer and the B layer are obtained by performing line analysis in the thickness direction of the coating layer on a region where both the A layer and the B layer contain three or more layers using an energy dispersive X-ray spectrometer (EDS) attached to a transmission electron microscope (TEM) at 20 or more points and averaging the results for each of the A layer and the B layer.

[0034] Here, the interface between the A layer and the B layer is set to the position that is the average value of the minimum value of the L content (existing within the A layer) and the maximum value of the L content (existing within the B layer) that are adjacent to each other, by measuring the change in the L content in the thickness direction of the coating layer.

[0035] (2) Average thickness The observation region is, for example, a rectangle with a length in the vertical direction (thickness direction) that includes the entire coating layer and a width in the horizontal direction (direction parallel to the substrate surface) of 5 μm, and this is set to 5 or more. Using the definition result of the interface between the aforementioned A layer and B layer, line analysis is performed to obtain the thickness of each layer, and by averaging these, the average thicknesses of the alternating laminate, the lower layer, and the surface layer are obtained.

[0036] Here, the surface of the substrate is observed in this longitudinal section, the interface between the substrate and the coating layer is determined by elemental mapping, and for the roughness curve of the interface thus obtained, an average line is arithmetically obtained and this is taken as the surface of the substrate. Then, the direction perpendicular to this surface of the substrate is defined as the thickness direction.

[0037] Also, for the average thicknesses of the A layer and B layer that constitute the alternating laminate, using a transmission electron microscope (TEM), in a region where both the A layer and B layer contain 3 or more layers, the thicknesses of the A layer and B layer are measured and their respective average values are obtained. Then, the average value is obtained for at least 5 regions and averaged to obtain the average thicknesses of the A layer and B layer.

[0038] (3) Orientation For the measurement of the diffraction peak intensity of the metal boride by X-ray diffraction method, an X-ray diffraction method of the 2θ / θ focusing method engineering system using Cu-Kα rays (wavelength λ: 0.15405 nm) can be used. Also, the (001) plane of the hexagonal crystal may sometimes be expressed as the (0001) plane.

[0039] 4. Manufacturing method As an example of the method for forming the metal boride layer, a film-forming method using a magnetron sputtering apparatus or a high-power pulse sputtering apparatus can be cited. As the film-forming conditions, for example, the targets are TiB2 and TiLB2, and the target input power is set to 500 W to 5000 W Gas condition: Ar 0.2 - 1.0 Pa Film formation temperature: 350 - 750 °C Table rotation speed: 1.5 - 3.0 rpm Bias voltage: 50 - 300 V Pulse frequency: 500 - 1500 Hz Pulse application time: 50 - 150 μsec can be increased.

Example

[0040] Next, examples will be described, but the present invention is not limited to these examples.

[0041] As raw material powders, WC powder, Co powder, TaC powder, NbC powder and Cr3C2 powder were prepared. These raw material powders were blended according to the blending composition shown in Table 1, wet-mixed in a ball mill for 72 hours, and dried. Then, it was press-molded into a compact at a pressure of 100 MPa. This compact was sintered in a vacuum of 6 Pa under the condition of maintaining the temperature at 1450 °C for 1 hour. After sintering, honing with R: 0.03 was performed on the cutting edge portion to produce 1 - 2 substrates made of WC-based cemented carbide having an insert shape of ISO standard · SEEN1203AFTN1.

[0042] Subsequently, a coating layer was formed on these substrates 1 - 2 by the following procedures (a) - (d).

[0043] (a) Each of the substrates 1 - 2 was ultrasonically cleaned in acetone and mounted along the outer periphery at a position radially away from the central axis on the rotating table in a high-power pulse sputtering apparatus in a dried state. On the other hand, in the high-power pulse sputtering apparatus, a TiB2-based sintered body target and a TiLB2-based sintered body target having the composition shown in Table 2 were respectively arranged at four positions sandwiching the rotating table. The pulse frequency and pulse application time of the TiB2-based sintered body target and the TiLB2-based sintered body target were the same.

[0044] (b) The inside of the high-power pulse sputtering apparatus was evacuated and maintained at a vacuum of 0.1 Pa or less, and the inside of the apparatus was heated to 500 °C with a heater. Then, a DC bias voltage of -200 V was applied to the substrate rotating on the rotary table. Then, argon gas (hereinafter referred to as Ar) was introduced into the apparatus as a reaction gas, and an atmosphere of 2.0 Pa was obtained. Further, by passing a current of 40 A through the tungsten filament provided in the apparatus, Ar ions were excited, and the substrate was subjected to Ar bombardment for 1 hour.

[0045] (c) Subsequently, the atmosphere inside the apparatus was set to 0.5 Pa, and the atmosphere inside the apparatus was made of only Ar gas. Then, high-power pulse sputtering was performed on the TiB2-based sintered body target and the TiLB2-based sintered body target under the predetermined pulse sputtering conditions shown in Table 2, and the coated inserts 1 to 13 of the examples shown in Table 3 (hereinafter referred to as Examples 1 to 13) were manufactured respectively.

[0046] Also, for the purpose of comparison, for these substrates 1 to 2, using a TiB2-based sintered body target and a TiLB2-based sintered body target, the lower layer and the coating layer were formed by the procedures of (a) to (d) under the conditions shown in Table 2, and the comparative coated inserts 1 to 13 as the comparative coating tools shown in Table 3 (hereinafter referred to as Comparative Examples 1 to 13) were manufactured respectively.

[0047] Comparative Example 13 was formed by film deposition using two TiB2-based sintered body targets without using a (Ti,L)B2-based sintered body target, and the input power, pulse frequency, and pulse application time of the targets in these two TiB2-based sintered body targets were the same.

[0048]

Table 1

[0049]

Table 2

[0050]

Table 3

[0051] In Table 2 and Table 3, "-" indicates that the corresponding item does not exist or is not applicable. Also, in Table 3, "○" indicates that the corresponding item is applicable.

[0052] Regarding Examples 1 to 13 and Comparative Examples 1 to 13, a single-edge wet face milling cutting test, which is a type of high-speed interrupted cutting, was carried out using a cutter of SE445R0506E, which is the product shape of Mitsubishi Materials Corporation. The following Cutting Tests 1 and 2 were carried out.

[0053] Cutting Test 1 Workpiece material: Ti-6Al-4V block material (width 110 mm × length 250 mm) Cutting speed: 110 m / min Depth of cut: 1.8 mm Feed: 0.18 mm / tooth Cutting length: 2.5 m

[0054] Cutting Test 2 Workpiece material: Ni-19Cr-19Fe-3Mo-0.9Ti-0.5Al-5.1(Nb+Ta) block material (width 60 mm × length 250 mm) Cutting speed: 90 m / min Depth of cut: 1.8 mm Feed: 0.18 mm / tooth Cutting length: 2.5 m

[0055] After the completion of Cutting Tests 1 and 2 (after the completion of cutting with a cutting length of 2.5 m), the flank wear width was measured. Tables 4 and 5 show the respective test results. However, when excessive wear progress, chipping, or other abnormal damages occurred before the end of the cutting time, the cutting was stopped and the cutting length from the start of cutting (indicated as "Cutting distance (m) until reaching the life" in Tables 4 and 5) was measured.

[0056]

Table 4

[0057]

Table 5

[0058] As is clear from the results shown in Tables 4 and 5, all of the examples exhibit excellent durability in high-speed interrupted cutting of materials with high weldability for coated tools such as Ti-based alloys and Ni-based alloys. On the other hand, all of the comparative examples clearly reach the service life in a short time because the wear progress of the cutting edge part is fast and chipping also occurs in the high-speed interrupted cutting of the material with high weldability.

Explanation of Signs

[0059] 1 Substrate 2 Coating layer 3 Alternate lamination 4 A layer 5 B layer 6 Underlayer 7 Surface layer

Claims

1. A surface-coated cutting tool having a substrate and a coating layer on the substrate, wherein the coating layer is formed by alternately laminating an A layer and a B layer each having an average thickness of 2 nm or more and 50 nm or less, The average composition of the A layer is (Ti １－ｘ L ｘ )B ｚ whereas the average composition of the B layer is (Ti １－ｙ L ｙ )B ｗ whereas L is one or more lanthanoid elements, 0.01 ≦ y - x ≦ 0.10, 0.01 ≦ y ≦ 0.20, 1.5 ≦ z ≦ 3.0, 1.5 ≦ w ≦ 3.0, and a surface-coated cutting tool characterized by the above.

2. The surface-coated cutting tool according to claim 1, wherein when the coating layer is analyzed by X-ray, the X-ray intensity corresponding to the (001) plane is the maximum.

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