Surface coated cutting tools

Abstract

To provide a surface-coated cutting tool having excellent abrasion resistance in cutting work of stainless steel, etc.SOLUTION: A surface-coated cutting tool includes a substrate and a coating layer on the substrate. The coating layer includes a metal boride layer including a precipitation phase. The average composition of a metal component of the metal boride layer is Ti1-xMx (M being at least one kind of Al, V, Cr, Zr, Nb, Mo, Hf, and W, and x being 0.00<x<0.50). The precipitation phase consists of metal of at least one kind of M and / or at least one kind of Ti and M, and the average composition of the precipitation phase is Ti1-yMy (0.50<y≤1.00). In a longitudinal plane of the coating layer, the precipitation phase accounts for 2-70 area% of the entire coating layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool). [Background technology]

[0002] Conventionally, coated tools have been known in which a coating layer is formed on a substrate such as a tungsten carbide (hereinafter referred to as WC)-based cemented carbide. Furthermore, it has been proposed that a coating layer with improved cutting performance can be obtained by adjusting its composition, structure, and crystal structure.

[0003] For example, Patent Document 1 describes a coated cutting tool comprising one or more layers covering a substrate, each layer containing one or more elements from groups 4, 5, and 6 of the periodic table, nitrides, carbides, oxides, borides of Al, and their mutual solid solutions and mixtures, wherein at least one of the layers is columnar crystal, and the columnar crystals have different growth directions, and the coated tool is said to have excellent wear resistance.

[0004] Patent Document 2 describes a coated tool having a boride coating layer on a substrate made of one or more metal elements selected from Al, Si, Cr, W, Ti, Nb, and Zr, wherein the boride coating layer has a hexagonal crystal structure, the (001) diffraction line is the strongest in X-ray diffraction, and the residual compressive stress is 0.1 GPa or more, and the coated tool is said to have high hardness without sacrificing the adhesion properties of the coating layer.

[0005] Patent Document 3 describes a coating tool having a coating layer comprising at least one TiB2 layer having a fibrous microstructure on a substrate, wherein the cylindrical grains of the fibrous microstructure have a diameter of 5 to 50 nm, a length-to-diameter ratio l / d > 2, and a length of 250 nm or more, and are oriented perpendicular to the surface of the substrate, and the coating tool is said to have excellent toughness of the coating layer.

[0006] Patent Document 4 describes a coated tool in which an intermediate layer made of AlxMy nitride or carbonitride (x+y=100, 40≦x≦95, 5≦y≦60, M is one or more selected from Ti, Cr, V, and Nb) is topped with a boride of one or more elements selected from Al, Si, Cr, W, Ti, Nb, and Zr, wherein the intermediate layer has a cubic crystal structure on the substrate side and a hexagonal crystal structure on the boride side, and this coated tool is said to have excellent wear resistance. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2002-263913 [Patent Document 2] Japanese Patent Publication No. 2008-2380281 [Patent Document 3] Japanese Patent Publication No. 2002-355704 [Patent Document 4] Japanese Patent Publication No. 2012-228735 [Overview of the project] [Problems that the invention aims to solve]

[0008] This invention has been made in view of the above circumstances and proposals, and aims to provide a surface-coated cutting tool that has excellent wear resistance in high-speed cutting of difficult-to-machine materials such as stainless steel.

[0009] A surface-coated cutting tool according to an embodiment of the present invention is It comprises a substrate and a coating layer on the substrate, The coating layer includes a metal boride layer containing a precipitated phase. The average composition of the metal components in the metal boride layer is Ti 1-x M x (M is at least one of Al, V, Cr, Zr, Nb, Mo, Hf, W, 0.00) <x<0.50)であり、 The precipitated phase contains M and / or Ti and M, and its average composition is Ti 1-y M y(0.50 < y ≦ 1.00), In a longitudinal cross-section of the coating layer, the precipitated phase accounts for 2 to 70 area% of the entire coating layer.

[0010] The surface-coated cutting tool according to the embodiment may satisfy at least one of the following items (1) to (3). (1) In a longitudinal cross-section of the coating layer, the average thickness of the precipitated phase, which is the average length in the thickness direction of the coating layer, is more than 20 nm and less than 500 nm. (2) In a longitudinal cross-section of the coating layer, the precipitated phase This is calculated as (length of the precipitated phase parallel to the substrate surface) / (length of the coated layer of the precipitated phase in the thickness direction). has an aspect ratio of 2 or more and 30 or less. (3) The metal boride layer has crystals with a hexagonal crystal structure, and the (100) diffraction line intensity (I (100) ), (101) diffraction line intensity (I (101) ) and (001) diffraction intensity (I (001) ) satisfy (I (100) +I (101) ) / I (001) ≧ 3 . Effects of the Invention

[0011] The above-described surface-coated cutting tool has excellent wear resistance even in cutting of difficult-to-cut materials such as stainless steel and high-speed cutting. Brief Description of the Drawings

[0012] [Figure 1] FIG. 1 is a schematic view showing an example of a longitudinal cross-section of the surface-coated cutting tool according to an embodiment of the present invention. Mode for Carrying Out the Invention

[0013] The present inventors have studied coating layers containing metal boride. As a result, they have recognized the following matters.

[0014] (1) The coating layer containing TiB2 has an incompatibility with Ti alloys and other materials, and has excellent wear resistance due to its high hardness. However, it has low heat resistance, and when cutting difficult-to-machine materials such as stainless steel, the cutting edge becomes hot, making it prone to boundary damage and leading to a premature end of its lifespan.

[0015] (2) The coating layer having TiB2 has high diffraction line intensity and therefore has columnar crystals, resulting in excellent hardness, but it has poor toughness, so chipping is likely to occur when a load is applied to the cutting edge.

[0016] Based on these considerations, we have diligently examined the matter and obtained the following findings. (a) When the coating layer contains a metal boride with M (M being at least one of Al, V, Cr, Zr, Nb, Mo, Hf, and W) in addition to Ti, boundary damage is suppressed and durability is improved, even in high-speed cutting of difficult-to-machine materials such as stainless steel where the cutting edge becomes hot.

[0017] (b) By including a metal precipitate phase that is softer than the metal boride within the coating layer, the toughness of the metal boride layer is compensated for, and chipping is suppressed when a high load is applied to the cutting edge.

[0018] (c) In the X-ray diffraction of the metal boride layer, if a predetermined relationship is satisfied for (100) diffraction line intensity, (101) diffraction line intensity, and (001) diffraction line intensity, the brittle columnar crystal structure is eliminated, and cracks that occur on the surface of the coating layer do not immediately reach the substrate surface, which can further improve the chipping resistance of the coating layer.

[0019] The present invention is derived from this finding, and a coating tool according to an embodiment of the present invention will be described in detail below. 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), and the units of the upper limit (M) and the lower limit (L) are the same.

[0020] FIG. 1 is a schematic diagram showing 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, in the surface-coated cutting tool according to the embodiment, a coating layer including a metal boride layer (2) is formed on a base body (1), and a precipitated phase (3) is precipitated in the metal boride layer (2).

[0021] 1. Coating Layer The coating layer preferably has a metal boride layer containing a precipitated phase. The description will be given in order below.

[0022] (1) Metal Boride Layer (1-1) Average Thickness The average thickness of the metal boride layer is preferably 0.5 to 10.0 µm. The reason for this is that if the average thickness is less than 0.5 µm, the metal boride layer cannot exhibit excellent wear resistance over long-term use; on the other hand, if the average thickness exceeds 10.0 µm, abnormal damage such as chipping, fracture and peeling is likely to occur. The average thickness of the metal boride layer is more preferably 1.0 to 6.0 µm.

[0023] (1-2) Average Composition The average composition of the metal components of the metal boride layer is Ti 1-x M x (wherein M is at least one selected from the group consisting of Al, V, Cr, Zr, Nb, Mo, Hf and W, and 0.00<x<0.50). When exposed to high temperature during cutting, the metal element M forms a dense oxide to prevent oxygen from penetrating into the structure of the coating layer and suppress the occurrence of boundary damage. In order to suppress the occurrence of this boundary damage, 0.00<x<0.50 is preferred. In addition, when x is within this range, precipitation of the precipitated phase described later can be achieved. Furthermore, when x is 0.50 or more, the hardness of the metal boride decreases, which is not preferable.

[0024] For the metal components Ti 1-x M x and boron B in the metal boride layer, there is no particular restriction on the ratio therebetween, but when the ratio of the former is 1, the ratio of the latter is more preferably 1.7 to 2.3. Within this more preferable range, boundary damage can be suppressed more reliably, and precipitation of the precipitated phase is ensured.

[0025] (1-3) Crystal structure The metal boride layer has a hexagonal crystal structure, and the (100) diffraction line intensity (I (100) ) and (101) diffraction line intensity (I (101) ) are preferably greater than the (001) diffraction intensity (I (001 ), and the sum of the (100) diffraction line intensity (I (100) ) and the (101) diffraction line intensity (I (101) ) is 001 diffraction line intensity (I (001) ) is 3 times or more, that is, (I (100) +I (101) ) / I (001) ≧3 is more preferable. When it is 3 times or more, the toughness of the coating layer is reliably sufficient.

[0026] (2) Precipitated phase (2-1) Average composition The precipitated phase contains M and / or Ti and M. The precipitated phase is softer than the metal boride layer, supplements the toughness of the metal boride layer, and suppresses the occurrence of chipping when a high load is applied to the cutting edge. The average composition of this precipitated phase is Ti 1-y M y (0.50 < y ≦ 1.00) is preferable. When y is 0.50 or less, exposure to high temperature during cutting processing prevents the precipitated phase from forming a dense oxide, which is not preferable.

[0027] (2-2) Size In a longitudinal section of the surface-coated cutting tool (a cross-section perpendicular to the surface when ignoring minute irregularities on the substrate surface and treating the substrate surface as a flat surface), it is more preferable that the average length of the precipitated phase in the thickness direction of the coating layer (direction perpendicular to the substrate surface) is more than 20 nm and less than 500 nm. The reason is that when the average length in the thickness direction of the coating layer is less than 20 nm, the heat resistance of the coating layer may be insufficient, and when it is more than 500 nm, the hardness of the coating layer may decrease.

[0028] The aspect ratio of the precipitated phase, that is, (Length of the precipitated phase parallel to the substrate surface) / (Length of the coated layer of the precipitated phase in the thickness direction) is, A ratio of 2 to 30 is more preferable. When the aspect ratio is within this range, the coating layer has sufficient hardness and toughness. That is, if the aspect ratio is less than 2, the (001) diffraction lines become strong and the toughness of the coating layer may not be sufficient, while if the aspect ratio exceeds 30, the hardness of the coating layer may not be sufficient.

[0029] (2-3) Occupied area In the aforementioned longitudinal section, it is more preferable that the precipitated phase occupies 2 to 70 area percent of the entire coating layer. If it is less than 2 area percent, a dense oxide phase cannot be sufficiently formed during machining, while if it is more than 70 area percent, the hardness of the metal boride layer may not be sufficient, resulting in poor wear resistance of the coating layer.

[0030] (3) Other layers In this embodiment, the film is formed so that no layers other than the metal boride layer exist. However, unintended pressure fluctuations occur within the film deposition apparatus, which may result in the formation of layers with unintended compositions different from the metal boride layer.

[0031] 2.Base (1)Material The substrate used in this embodiment can be any of the conventionally known substrate materials, as long as it does not hinder the achievement of the aforementioned objectives. For example, it is preferable to use any of the following: cemented carbide (WC-based cemented carbide, including those containing WC and Co, and further including those with carbonitrides such as Ti, Ta, and Nb added), 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.

[0032] (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 and the shape of a drill.

[0033] 3.Measurement method For example, a focused ion beam system (FIB), a cross-section polisher (CP), etc., is used to cut the coating layer into longitudinal sections at arbitrary positions to prepare a sample for observation. This sample is then observed to measure the average thickness of the coating layer, the average composition of the metal boride layer and precipitated phase, and the shape and area percentage (area %) of the precipitated phase. Here, the surface of the substrate is determined by observing this longitudinal section, and the interface between the substrate and the coating layer is defined by elemental mapping. The average straight line of the roughness curve of the interface thus obtained is then arithmetically calculated and defined as the surface of the substrate.

[0034] The average thickness of the metal boride layer constituting the coating layer is calculated by measuring the thickness at five or more points using a scanning electron microscope (SEM) and averaging the results.

[0035] The average composition of the metal boride layer is determined by performing line analysis in the thickness direction at 20 points using an energy dispersive X-ray spectrometer (EDS) attached to a transmission electron microscope (TEM), and averaging the results.

[0036] The area percentage of the precipitated phase is calculated by setting up five or more rectangular observation areas of 5 μm in the direction parallel to the substrate surface and 3 μm in the thickness direction of the coating layer using a SEM, determining the area occupied by the precipitated phase in each observation area, and averaging the area percentage of the precipitated phase. The particle size of the precipitated phase is calculated by setting up five or more of the same observation areas as described above, measuring the length of the precipitated phase parallel to the substrate surface and the length of the precipitated phase in the thickness direction of the coating layer in each observation area, averaging the results, and calculating the aspect ratio. (Length of the precipitated phase parallel to the substrate surface) / (Length of the coated layer of the precipitated phase in the thickness direction) Calculate.

[0037] The average composition of the precipitated phase is determined by extracting an arbitrary number of precipitated phases from the observation area, ensuring that the total number of extracted precipitated phases is 20 or more, performing EDS analysis on the precipitated phases, and averaging the results. Here, the precipitated phase refers to the following: When the Ti, M, and B components are measured by SEM-EDS mapping analysis and TEM-EDS mapping analysis, the region in which the metallic components Ti and M are detected, but B is not detected, is treated as the precipitated phase.

[0038] The crystal structure of the metal boride layer is measured using an X-ray diffractometer with Cu-Kα radiation as the source, under the following conditions: measurement range (2θ): 20~120°, scan step: 0.013°, and measurement time per step: 0.48 sec / step. The diffraction line intensities of the (100), (101), and (001) peaks are calculated from the obtained diffraction line results.

[0039] 4. Manufacturing method For the deposition of the metal boride layer, a deposition method using a magnetron sputtering apparatus or a high-power pulse sputtering apparatus is preferred. As for specific film deposition conditions, for example, two types of targets, TiB2 and M, are used, and the target power input is 500W to 5000W. Gas conditions: Ar 0.1~1.0 Pa Film forming temperature: 300~700℃ Bias voltage: 50~300V Pulse frequency: 500~1500Hz Pulse application time: 50-150 μs It can be given. [Examples]

[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, all having a particle size range of 1 to 3 μm, were prepared. These raw material powders were blended according to the formulation shown in Table 1, wet-mixed in a ball mill for 72 hours, and dried. Subsequently, the mixture was press-molded into compacts at a pressure of 100 MPa. These compacts were sintered in a vacuum of 6 Pa at a temperature of 1450°C for 1 hour. After sintering, the cutting edge portion was honed to R:0.03 to produce substrates 1 and 2 made of WC-based cemented carbide with an insert shape conforming to ISO standard SEEN1203AFTN1.

[0042] Next, coating layers were formed on these substrates 1 and 2 according to the following procedures (a) to (d).

[0043] (a) Each of the substrates 1 and 2 was ultrasonically cleaned in acetone and, in a dried state, mounted along the outer circumference at a predetermined radial distance from the central axis on the rotary table in the high-power pulse sputtering apparatus. Meanwhile, TiB2 sintered targets and M targets were placed at four locations opposite each other on either side of the rotary table inside the high-power pulse sputtering apparatus.

[0044] (b) The 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 -200V was applied to the substrate rotating on the rotary table. Subsequently, argon (hereinafter referred to as Ar) gas was introduced into the apparatus as a reaction gas to create an atmosphere of 2.0 Pa. Furthermore, Ar ions were excited by passing a current of 40 A through the tungsten filament provided in the apparatus, 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 consisted only of Ar gas. Then, high-power pulse sputtering was performed on the TiB2 sintered body target and the M target under the predetermined pulse sputtering conditions shown in Table 2, for a time corresponding to the layer thickness, to manufacture the example coated inserts 1 to 13 (hereinafter referred to as Examples 1 to 13) shown in Table 3.

[0046] Furthermore, for comparative purposes, a lower layer and a coating layer were formed on these substrates 1 and 2 according to the procedures (a) to (d) described above under the conditions shown in Table 4, and comparative coating inserts 1 to 7 (hereinafter referred to as comparative examples 1 to 7) were manufactured as comparative coating tools as shown in Table 5.

[0047] [Table 1]

[0048] [Table 2]

[0049] [Table 3]

[0050] In Table 3, "○" indicates that the item is satisfied, and "-" indicates that it is not satisfied. Also, the metallic component Ti of the metal boride layer. 1-x M x We have confirmed that the ratio of to boron B is 1:1.7 to 2.3.

[0051] [Table 4]

[0052] In Table 4, "-" indicates that there is no matching entry.

[0053] [Table 5]

[0054] In Table 5, "○" indicates that the item is satisfied, and "-" indicates that there is no applicable item or that the item is not satisfied. Furthermore, the metal component Ti of the metal boride layer is also indicated. 1-x M x We have confirmed that the ratio of to boron B is 1:1.7 to 2.3.

[0055] For Examples 1-13 and Comparative Examples 1-7, single-edge face milling tests were performed using the SE445R0506E cutter. High-speed cutting was performed on stainless steel SUS304 under the following cutting conditions.

[0056] Conditions for machining tests Workpiece material: JIS SUS304 block material (width 1500mm x length 250mm) Cutting speed: 220m / min Cut: 1.7mm Feed rate: 0.2mm / tooth Cutting length: 3m

[0057] After the cutting test was completed, the flank wear width was measured to observe whether chipping occurred. Since the flank wear width includes wear due to boundary damage, it is also possible to evaluate whether boundary damage was suppressed. The test results are shown in Table 6. However, if chipping occurred before the end of the cutting time, cutting was stopped and the cutting length from the start of cutting (expressed as "cutting distance to life (m)" in Table 6) was measured.

[0058] [Table 6]

[0059] As is clear from the results shown in Table 6, all of the examples demonstrate excellent resistance to welding and wear in high-speed cutting of materials with high adhesion to coated tools, such as austenitic stainless steel, while suppressing boundary damage. In contrast, in all of the comparative examples, it is clear that the wear progression of the cutting edge progresses rapidly during high-speed cutting of the highly adhesive material, and the service life is reached in a relatively short time. [Explanation of symbols]

[0060] 1 Base 2 Metal boride layer 3. Precipitated phase

Claims

1. It has a substrate and a coating layer on the substrate, The coating layer includes a metal boride layer containing a precipitated phase. The average composition of the metal components in the metal boride layer is Ti １－ｘ M ｘ (M is at least one of Al, V, Cr, Zr, Nb, Mo, Hf, and W, with a value of 0.00 < x < 0.50) The precipitated phase consists of at least one metal of M and / or Ti and at least one metal of M, and the average composition of the precipitated phase is Ti １－ｙ M ｙ (0.50 < y ≤ 1.00) In the longitudinal section of the coating layer, the precipitated phase accounts for 2 to 70% of the total area of ​​the coating layer. A surface-coated cutting tool characterized by the following features.

2. The surface-coated cutting tool according to claim 1, characterized in that, in the longitudinal cross-section of the coating layer, the average thickness of the precipitated phase is greater than 20 nm and less than 500 nm in the thickness direction of the coating layer.

3. The surface-coated cutting tool according to claim 1 or 2, characterized in that, in the longitudinal cross-section of the coating layer, the aspect ratio of the precipitated phase (length of the precipitated phase parallel to the substrate surface) / (length of the precipitated phase in the thickness direction of the coating layer) is 2 or more and 30 or less.

4. The metal boride layer has a hexagonal crystal structure, and the (100) diffraction line intensity (I) in X-ray diffraction is （１００） ), (101) diffraction line intensity (I （１０１） ) and (001) diffraction intensity (I （００１） )teeth, (I （１００） +I （１０１） ) / I （００１） ≧3 A surface-coated cutting tool according to claim 1 or 2, characterized in that it satisfies the following conditions.

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