Surface coated cutting tool

Abstract

To provide a surface coated cutting tool that has durability even for high-speed cutting processing to process a Ti-based alloy, a Ni-based alloy, etc., under a condition of 80 n / min or faster in cutting speed.SOLUTION: There is provided a surface-coated cutting tool that has a base body and a coating layer on the base body, wherein the coating layer has a boride layer including one kind or more of Al and Ti, the boride layer has an alternate laminate structure, which has an A layer and a B layer of 2 to 50 nm in average thickness alternately laminated. Here, the B layer has a larger Al content than the A layer, and while the A layer has an average composition (AlxTi1-x)Bz, the B layer has an average composition (AlyTi1-y)Bw, wherein 0.03≤y-x≤0.40, 1.5≤z≤3.0, and 1.5≤w≤3.0 hold.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 technology]

[0002] 2. Description of the Related Art Conventionally, as a coated tool, there has been known, for example, a tool having a coating layer formed on a substrate such as a tungsten carbide (hereinafter abbreviated as WC)-based cemented carbide. It has been proposed to obtain a coating layer with improved cutting performance by adjusting the composition, texture, crystal structure, etc. of this coating layer.

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

[0004] Patent Document 2 describes a coated tool having a coating layer on a base, the coating layer being made of one or more layers of one or more of elements from Groups 4, 5 and 6 of the periodic table, nitrides, carbides, oxides and borides of Al, and their mutual solid solutions and mixtures, at least one layer of the coating layer being columnar crystals, the columnar crystals having different growth directions, and the coated tool is said to have excellent fracture resistance even when subjected to cutting with high impacts.

[0005] Patent Document 3 describes a coated tool having a substrate coated with a boride layer made of one or more metallic elements selected from Al, Si, Cr, W, Ti, Nb and Zr, in which the boride layer has a hexagonal crystal structure, has the strongest diffraction intensity in the (001) plane in X-ray diffraction, and has a residual compressive stress of 0.1 GPa or more. The coated tool is said to have high hardness without sacrificing the adhesion of the coating layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6561048 [Patent Document 2] JP 2002-263913 A [Patent Document 3] JP 2008-238281 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in consideration of the above circumstances and proposals, and has an object to provide a surface-coated cutting tool that has durability even in high-speed cutting of difficult-to-cut materials such as Ti-based alloys, Ni-based alloys, etc. at cutting speeds of 80 m / min or more.

[0008] The surface-coated cutting tool according to an embodiment of the present invention comprises: A substrate and a coating layer on the substrate, The coating layer has a boride layer containing one or more of Al and Ti, the boride layer has an alternating laminate structure in which A layers and B layers, each having an average thickness of 2 nm or more and 50 nm or less, are alternately laminated; The Al content of the B layer is higher than that of the A layer, The average composition of the A layer is (Al x Ti 1-x ) B z The average composition of the B layer is (Al y Ti 1-y ) B w and 0.03≦y≦0.40, 1.5≦z≦3.0, 1.5≦w≦3.0 It is.

[0009] The surface-coated cutting tool according to the above embodiment may satisfy the following condition (1). (1) The aforementioned x and y are 0.00≦x≦0.30 and 0.03≦y≦0.70. Effect of the Invention

[0010] The above-mentioned surface-coated cutting tool has excellent durability even when subjected to high-speed cutting of difficult-to-cut materials such as Ti-based alloys and Ni-based alloys. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing an example of a vertical section (the definition of a vertical section will be described later) of a surface-coated cutting tool according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present inventors have conducted research into coating layers for coated tools containing metal borides, and have discovered the following.

[0013] (1) The coating layer containing TiB2 has no affinity for Ti alloys, Ni alloys, etc., and has excellent wear resistance due to its high hardness. However, it has low heat resistance in cutting processes where the cutting edge temperature is high, such as high-speed cutting, and when high-speed cutting of difficult-to-cut materials such as Ti alloys and Ni alloys, the cutting edge becomes hot and boundary damage is likely to develop, so its durability is not sufficient.

[0014] (2) When Al is added to TiB2 to form a composite boride layer of Al and Ti, the heat resistance of the coating layer is improved, but the hardness decreases, resulting in a decrease in wear resistance.

[0015] Taking these factors into consideration, the inventors conducted extensive research and discovered that it is possible to achieve both the excellent wear resistance provided by the high hardness of the TiB2 layer and the improved heat resistance provided by the Al-Ti composite boride layer by alternating stacking two types of Al-Ti composite boride layers with different Al contents to a specified thickness, thereby improving durability.

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

[0017] 1.Coating layer FIG. 1 is a schematic diagram of an example of a vertical cross section of a surface-coated cutting tool according to an embodiment of the present invention. As is clear 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 a laminated structure (3) of metal boride layers. The laminated structure (3) of metal boride is an alternating laminate of A layers (4) and B layers (5). The A layers (4) and B layers (5) are also alternately laminated in the white portion of FIG. 1. In addition to the laminated structure (3), the coating layer (2) in FIG. 1 has a base layer (6) and a surface layer (7). However, the base layer (6) and the surface layer (7) may be provided selectively and are not essential. In addition, the longitudinal section is a section perpendicular to the base body of an insert when the surface of the base body is considered to be flat and has no irregularities, and is a section perpendicular to the axis of a tool with a shaft.

[0018] (1) Metal boride layer (1-1) Laminated structure The metal boride layer has a laminated structure in which layers A and layers B (details of layers A and B will be described later) are alternately laminated, and the average thickness thereof is not particularly limited, but is preferably, for example, 0.2 μm or more and 10.0 μm or less. The reason is that if the average thickness of the laminated structure is less than 0.2 μm, the wear resistance may not be sufficient, whereas if it exceeds 10.0 μm, chipping may occur easily. As long as the layered structure has A layers and B layers alternately laminated, the layer closest to the base body and the layer closest to the tool surface may both be either an A layer or a B layer.

[0019] (1-2) Average thickness of layers A and B The average thickness of each of the A layer and the B layer constituting the laminated structure is preferably 2 nm or more and 50 nm or less. The reason why the average thickness in this range is preferable is as follows: if it is less than 2 nm, the crystal grains constituting the laminated structure become too small and chipping is likely to occur, whereas if it exceeds 50 nm, the laminated structure cannot ensure sufficient hardness.

[0020] (1-2) Average composition of layers A and B The average composition of layer A is Al x Ti 1-x B z , Al in layer B y Ti 1-y B w When the average composition is It is preferable that 0.03≦yx≦0.40, 1.5≦z≦3.0, and 1.5≦w≦3.0. The reasons are as follows.

[0021] If yx is less than 0.03, the strain present in the laminate structure is small, and the laminate structure does not have sufficient hardness. On the other hand, if yx exceeds 0.40, the strain present in the laminate structure becomes too large, resulting in locations where local stress occurs in the coating layer, making it more likely that cracks or chipping will occur.

[0022] It is more preferable that x and y satisfy the following conditions: 0.00≦x≦0.30, 0.03≦y≦0.70. When x and y are within these ranges, excellent heat resistance and wear resistance are exhibited even during high-speed cutting of difficult-to-cut materials such as Ti-based alloys and Ni-based alloys.

[0023] Furthermore, if z and w are less than 1.5, the non-affinity with the work material decreases and the coating layer does not exhibit sufficient adhesion resistance, while if they exceed 3.0, the hardness of the boride layer decreases and wear progresses early.

[0024] (3) Other layers Although the above object can be achieved by the laminated structure of the A layer and the B layer, both of which are metal boride layers, a base layer and a surface layer may be further provided.

[0025] (3-1) Base layer An underlayer may be provided which is made of one or more Ti compound layers selected from Ti carbide layers, nitride layers, carbonate layers and carbonitride layers (the composition of these Ti compound layers is not limited to the 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 laminated structure and the substrate.

[0026] (3-2) Surface layer A surface layer may be selectively provided on the laminated structure. A TiN layer (the atomic ratio of Ti and N in the TiN layer is not limited to stoichiometric) may be provided as the surface layer. When this TiN layer is provided, since the TiN layer itself has a golden color tone, it can be used as an identification layer for determining whether the coated tool is unused or used by a change in color tone. The average thickness of the TiN layer as the identification layer may be, for example, 0.1 to 1.0 μm. The surface layer may be an Al2O3 layer, the average thickness of which may be 0.1 to 15.0 μm.

[0027] (3-3) Unintended layer In this embodiment, the film is formed so that no layers other than the metal boride layer, the underlayer, and the surface layer exist; however, unintended fluctuations in pressure within the film forming apparatus, etc., may occur, resulting in the formation of an unintended layer having a composition different from that of the metal boride layer, underlayer, and surface layer of the laminated structure.

[0028] 2.Base (1)Material The material of the substrate used in this embodiment can be any known material as long as it does not hinder the achievement of the above-mentioned object. For example, cemented carbide (WC-based cemented carbide, WC, Co, and Ti, Ta, Nb, etc.), cermet (TiC, TiN, TiCN, etc.), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide), cBN sintered body, or diamond sintered body.

[0029] (2) Shape There are no particular limitations on the shape of the base body as long as it is a shape that can be used as a cutting tool, and examples of the shape include the shape of an insert and the shape of a drill.

[0030] 3.Measurement method The average thicknesses of the A layer, B layer, laminated structure, lower layer, and surface layer constituting the coating layer, and the average compositions of the A layer and B layer are measured as follows.

[0031] (1) Average thickness The coating layer is cut at a longitudinal section at an arbitrary position to prepare a specimen for observation. This specimen is prepared using, for example, a focused ion beam system (FIB), a cross section polisher (CP), etc. This specimen for observation is observed, and the average thickness of the laminated structure, lower layer, and surface layer are measured. The observation area is, for example, a rectangle with a length that includes the entire coating layer in the vertical direction (thickness direction) and a width of 5 μm in the horizontal direction (direction parallel to the substrate surface), and 5 or more of these are set. One or more line analyses are performed in each area to determine the thickness of each layer, and the average of these is used to determine the average thickness of the laminated structure, lower layer, and surface layer.

[0032] Here, the surface of the substrate is determined by observing the cross section, determining the interface between the substrate and the coating layer by element mapping, and arithmetically determining the average straight line of the roughness curve of the interface thus obtained, which is defined as the surface of the substrate. The direction perpendicular to the surface of the substrate is defined as the thickness direction.

[0033] The average thickness of layers A and B that make up the laminate structure is determined by measuring the thicknesses of layers A and B in areas that contain three or more layers of each using a transmission electron microscope (TEM) and averaging the thicknesses. This average is then calculated for at least five areas and averaged to determine the average thickness of layers A and B.

[0034] The average composition of layers A and B is determined by performing line analysis in the thickness direction of the coating layer at 20 or more points in an area containing three or more layers of both layers A and B using an Energy Dispersive X-ray Spectrometer (EDS) attached to a Transmission Electron Microscope (TEM), and averaging the results for each layer A and B. Here, the interface between layers A and B is determined by measuring the change in Al content in the thickness direction of the coating layer, and is defined as the position where the average value of the minimum value (present in layer A) and the maximum value (present in layer B) of the Al content adjacent to each other is reached.

[0035] 4. Manufacturing method The metal boride layer can be formed, for example, by a film formation method using a magnetron sputtering device or a high-output pulse sputtering device. As the film formation conditions, for example, two types of targets, TiB2 (atomic ratio of Ti and B is 1:2) and AlB2 (atomic ratio of Al and B is 1:2), are used, and the target input power is set to 500W to 5000W. Gas conditions: Ar 0.1-1.0 Pa Film forming temperature: 500~600℃ Table rotation speed: 1.5~3.0rpm Bias voltage: 50~300V Pulse frequency: 500~1500Hz Pulse application time: 50 to 150 μs can be given. EXAMPLES

[0036] Next, examples will be described, but the present invention is not limited to these examples.

[0037] The raw powders were prepared as WC powder, Co powder, TaC powder, NbC powder, and Cr3C2 powder, all with particle sizes in the range of 1 to 3 μm. These raw powders were mixed according to the composition shown in Table 1, wet mixed in a ball mill for 72 hours, and dried. They were then pressed into a green compact at a pressure of 100 MPa. This green compact was sintered in a vacuum of 6 Pa at a temperature of 1450°C for 1 hour. After sintering, the cutting edge was honed to R: 0.03 to produce WC-based cemented carbide substrates 1 and 2 with the insert shape of ISO standard SEEN1203AFTN1.

[0038] Subsequently, a coating layer was formed on each of the substrates 1 and 2 according to the following procedures (a) to (d).

[0039] (a) Each of the substrates 1 and 2 was ultrasonically cleaned in acetone and, in a dried state, was attached along the outer periphery at a position a predetermined distance away from the central axis in the radial direction on a rotating table in a high-power pulse sputtering device. Meanwhile, in the high-power pulse sputtering device, a sintered TiB2 target and a sintered AlB2 target were placed at four positions on either side of the rotating table.

[0040] (b) The inside of the high-power pulse sputtering apparatus was evacuated and maintained at a vacuum of 0.1 Pa or less, while 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 rotating table. Then, argon (hereinafter referred to as Ar) gas was introduced as a reactive gas into the apparatus, and the atmosphere was set to 2.0 Pa. Furthermore, a current of 40 A was passed through a tungsten filament provided in the apparatus to excite Ar ions, and the substrate was subjected to Ar bombardment treatment for 1 hour.

[0041] (c) The atmosphere in the apparatus was then set to 0.5 Pa, and the atmosphere in the apparatus was filled only with Ar gas. Thereafter, the TiB2 sintered compact target and the AlB2 sintered compact target were subjected to high-power pulse sputtering 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.

[0042] In addition, for the purpose of comparison, a lower layer and a coating layer were formed on these substrates 1 and 2 using a TiB2 sintered target and an AlB2 sintered target under the conditions shown in Table 2 according to the procedures (a) to (d), and comparative coated inserts 1 to 13 (hereinafter referred to as Comparative Examples 1 to 13) were produced as comparative coated tools shown in Table 3.

[0043] [Table 1]

[0044] [Table 2]

[0045] [Table 3]

[0046] In Table 3, "-" indicates that an alternating laminate structure was not formed.

[0047] For Examples 1 to 13 and Comparative Examples 1 to 13, a single-edged face milling cutting test was carried out using a cutter with a product shape of SE445R0506E manufactured by Mitsubishi Materials Corporation. The following cutting tests 1 and 2 were carried out.

[0048] Cutting test 1 Workpiece: Ti-6Al-4V block material (width 110mm x length 250mm) Cutting speed: 115m / min Cutting depth: 1.8mm Feed: 0.14mm / tooth Cutting length: 2.5m

[0049] Cutting test 2 Workpiece: Ni-19Cr-19Fe―3Mo-0.9Ti-0.5Al-5.1(Nb+Ta) block material (width 60mm x length 200mm) Cutting speed: 90m / min Cutting depth: 1.8mm Feed: 0.04mm / tooth Cutting length: 2.5m

[0050] After completion of cutting tests 1 and 2 (after completion of a cutting length of 2.5 m), the flank wear width was measured. Tables 4 and 5 show the test results. However, if abnormal damage such as chipping occurred before the end of the cutting time, cutting was stopped and the cutting length from the start of cutting was measured (shown as "cutting distance (m) until end of life" in Tables 4 and 5).

[0051] [Table 4]

[0052] [Table 5]

[0053] As is clear from the results shown in Tables 4 and 5, all of the Examples exhibit excellent durability in high-speed cutting of materials that have high adhesion to coated tools, such as Ti-based alloys and Ni-based alloys. In contrast, in all of the comparative examples, it is clear that wear of the cutting edge progresses quickly during high-speed cutting of the highly adhesive material, and the service life is reached in a short period of time. [Explanation of symbols]

[0054] 1 Base 2 Covering layer 3. Metal boride layer structure 4 A layer 5 B layer 6 Base layer 7 Surface layer

Claims

1. 1. A surface-coated cutting tool having a substrate and a coating layer on the substrate, comprising: The coating layer has a boride layer containing one or more of Al and Ti, the boride layer has an alternating laminate structure in which A layers and B layers, each having an average thickness of 2 nm or more and 50 nm or less, are alternately laminated; The Al content of the B layer is higher than that of the A layer, The average composition of the A layer is (Al ｘ Ti １－ｘ ) B ｚ and the average composition of the B layer is (Al ｙ Ti １－ｙ ) B ｗ and 0.03≦y−x≦0.40, 1.5≦z≦3.0, and 1.5≦w≦3.0; A surface-coated cutting tool comprising:

2. 2. The surface-coated cutting tool according to claim 1, wherein x and y satisfy 0.00≦x≦0.30 and 0.03≦y≦0.70.

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