Surface-coated cutting tools

Abstract

A surface-coated cutting tool has a substrate and a coating layer disposed on the substrate. The substrate is a sintered cBN body, wherein the average particle size of the cBN particles in the sintered cBN body is 2.5 μm or more and 6.0 μm or less, and the content is 40% by volume or more and 70% by volume or less. The surface roughness R of the substrate is 0.1 μm or more and 1.5 μm or less. The coating layer has an average thickness of 1.0 μm or more and 5.0 μm or less and comprises a layer A, a layer B, and a layer C. The average composition of layer A is (Al... 1‑x Ti x N(0.35≤x≤0.60), average thickness t A The thickness is above 0.1 μm and below 1.0 μm, and the average composition of layer B is (Al... 1‑y‑z Ti y Si z N(0.35≤y≤0.60, 0.01≤z≤0.10), average thickness t B The thickness is above 0.2 μm and below 2.0 μm, and the average composition of the C layer is (Al... 1‑a‑b‑c Cr a Si b Cu c N(0.150≤a≤0.400, 0.050≤b≤0.200, 0.005≤c≤0.050), average thickness t C For particles larger than 0.1 μm and smaller than 2.0 μm, t B / t A For values ​​above 2.0 and below 6.0, R ≤ t C .

Description

Technical Field

[0001] This invention relates to surface-coated cutting tools (hereinafter, sometimes referred to as coating tools). This application claims priority to Japanese Patent Application No. 2021-043485, filed March 17, 2021. All descriptions in that Japanese patent application are incorporated herein by reference. Background Technology

[0002] In the past, in order to improve the life of cutting tools, coated tools with a coating layer formed on the surface of a matrix such as cubic boron nitride (hereinafter, sometimes referred to as cBN) sintered body have been developed, and the wear resistance of such coated tools has been improved.

[0003] Furthermore, in order to further improve the cutting performance of coated tools, various schemes have been proposed regarding the composition and structure of the coating layer.

[0004] For example, Patent Document 1 describes a coating tool having a matrix surface of a cBN sintered body having multiple protrusions formed by cBN particles and multiple recesses formed by a bonding material.

[0005] The coating layer includes M x L y A layer consisting of (0 < x ≤ 1.2, y = 1, M being at least one element selected from Groups 4 to 6 of the periodic table, aluminum, and silicon, and L being at least one element selected from boron, carbon, nitrogen, and oxygen).

[0006] The Rsub value of the substrate surface is 0.1–0.4 μm.

[0007] The outermost surface of the coating layer has an Rsurf of 0–0.15 μm and a Rasurf of 0–0.1 μm.

[0008] The Rsub is greater than the Rsurf, and the thickness of the coating layer is 0.2 to 10 μm. This coated tool also has durability in high-load and high-efficiency cutting processes.

[0009] Patent Document 1: Patent No. 5879664 Summary of the Invention

[0010] The present invention was made in view of the above circumstances and the above solution, and its object is to provide a coating tool that exhibits excellent wear resistance and chipping resistance even under high-load cutting.

[0011] The surface coating cutting tools involved in the embodiments of the present invention are as follows:

[0012] It has a matrix and a coating layer disposed on the matrix.

[0013] The matrix is ​​a cubic boron nitride sintered body, wherein the average particle size of the cubic boron nitride is 0.5 μm or more and 6.0 μm or less, the content of the cubic boron nitride is 40% by volume or more and 70% by volume, and the surface roughness R of the matrix is ​​0.1 μm or more and 1.5 μm or less.

[0014] The coating layer has an average thickness of 1.0 μm or more and 5.0 μm or less, and has layers A, B, and C extending from the surface of the substrate toward the tool surface.

[0015] The average composition of layer A is (Al) 1-x Ti x N(0.35≤x≤0.60), the average thickness t of layer A. A The size is between 0.1 μm and 1.0 μm.

[0016] The average composition of layer B is (Al) 1-y-z Ti y Si z N(0.35≤y≤0.60, 0.01≤z≤0.10), the average thickness t of layer B. B The size is between 0.2 μm and 2.0 μm.

[0017] The average composition of the C layer is (Al) 1-a-b-c Cr a Si b Cu c N(0.150≤a≤0.400, 0.050≤b≤0.200, 0.005≤c≤0.050), the average thickness t of layer C. C The size is between 0.1 μm and 2.0 μm.

[0018] The average thickness t of layer B B With respect to the average thickness t of layer A A The ratio of t B / t A For versions with a speed of 2.0 or higher and 6.0 or lower,

[0019] The average thickness t of layer C C For the surface roughness R above (t) C ≥R).

[0020] Furthermore, the surface-coating cutting tool involved in the above embodiments can satisfy the following (1).

[0021] (1) A TiN layer is present on the C layer.

[0022] The surface-coated cutting tool also exhibits excellent wear resistance and chipping resistance during high-load cutting. Attached Figure Description

[0023] Figure 1 This is a schematic diagram showing a longitudinal section of a surface-coated cutting tool according to an embodiment of the present invention. Detailed Implementation

[0024] The inventors studied the coating tool described in the aforementioned Patent Document 1 and realized that sufficient chipping resistance could not be obtained simply by controlling the surface roughness of the substrate and the surface roughness of the coating layer.

[0025] Therefore, the inventors conducted in-depth research. The results yielded the following new insights: By stacking an Al and Ti composite nitride layer (hereinafter, sometimes referred to as an AlTiN layer) and an Al, Ti, and Si composite nitride layer (hereinafter, sometimes referred to as an AlTiSiN layer) on a cBN sintered body, and further providing an Al, Cr, Si, and Cu composite nitride layer (hereinafter, sometimes referred to as an AlCrSiCuN layer), controlling the surface roughness of the substrate, and controlling the thickness of the AlCrSiCuN layer according to the surface roughness of the substrate, it is possible to obtain a coated tool that exhibits excellent wear resistance and chipping resistance even under high-load cutting.

[0026] Here, high-load cutting refers to cutting processes that apply a further load to the cutting tool compared to normal cutting processes.

[0027] The coating tool according to embodiments of the present invention will now be described in detail.

[0028] Furthermore, in this specification and claims, when “L~M” (L and M are both numerical values) is used to represent a numerical range, the range includes an upper limit value (M) and a lower limit value (L). When only the unit of the upper limit value (M) is recorded, the units of the upper limit value (M) and the lower limit value (L) are the same.

[0029] Figure 1 The diagram schematically shows a longitudinal section of the coating tool according to this embodiment (the definition will be described later). As can be seen from the figure, the coating tool according to this embodiment has a coating layer on the surface of the cBN sintered body 1, which serves as the substrate. This coating layer sequentially includes an AlTiN layer 2 as layer A, an AlTiSiN layer 3 as layer B, and an AlCrSiCuN layer 4 as layer C. Furthermore, the TiN layer 5 is selectively provided as described later, or it may be omitted.

[0030] They will be explained in turn below.

[0031] 1. Cubic boron nitride (cBN) sintered body

[0032] Depend on Figure 1It can be seen that the cBN sintered body as the matrix has cBN particles 6 as the hard phase and a bonding phase 7.

[0033] (1) cBN particles

[0034] The average particle size of cBN particles and the content of cBN particles in cBN sintered body are explained.

[0035] (1-1) Average particle size

[0036] In this embodiment, the average particle size of the cBN particles is preferably in the range of 0.5 μm or more and 6.0 μm or less.

[0037] The reason for this is that, in addition to improving the resistance to chipping by including cBN particles in the sintered body, if the average particle size is 0.5 to 6.0 μm, when used as a substrate for coated tools, it not only reliably suppresses chipping and breakage caused by the uneven shape of the tool tip due to the shedding of cBN particles from the substrate surface, but also sufficiently suppresses the propagation of cracks that develop from the interface between the cBN particles and the bonding phase due to stress applied to the tool tip during cutting, or cracks that develop due to the cracking of cBN particles, thereby achieving superior resistance to chipping. The average particle size of the cBN particles is more preferably 1.0 μm or more and 6.0 μm or less, more preferably 2.5 μm or more and 6.0 μm or less, and even more preferably 2.5 μm or more and 4.0 μm or less.

[0038] Here, the average particle size of cBN particles can be determined as follows.

[0039] The longitudinal section of the cBN sintered body (a section considered as a plane and perpendicular to the plane, ignoring minor surface irregularities) was mirror-finished, and the microstructure of the mirror-finished surface was observed using a scanning electron microscope (SEM) to obtain a secondary electron image. Next, the cBN particle portion within the obtained image was extracted through image processing, and the average particle size was calculated based on the maximum length of each particle obtained through image analysis, as described later.

[0040] Here, when extracting the cBN particle part in the image through image processing, in order to clearly distinguish between cBN particles and the binding phase, the image is represented by a monochrome of 256 gray levels with black being 0 and white being 255. For the peak value (A) of the pixel value of the cBN particle part and the peak value (B) of the pixel value of the binding phase part, the value calculated by (BA) / 2+A is used as the threshold for binarization.

[0041] Furthermore, for the region used to determine the pixel values ​​of the cBN particle portion, a region of approximately 0.5 μm × 0.5 μm is preferably selected, and the average value calculated from at least three different locations within the same image region is set as the peak value of the aforementioned pixel value of the cBN. Moreover, for the region used to determine the pixel values ​​of the binding phase portion, a region of approximately 0.2 μm × 0.2 μm to approximately 0.5 μm × 0.5 μm is preferably selected, and similarly, the average value calculated from at least three different locations within the same image region is set as the peak value of the aforementioned pixel value of the binding phase.

[0042] In addition, after binarization, processes such as cutting apart the parts of cBN particles that are considered to be in contact with each other are performed, for example, by using watershed image processing to separate the cBN particles that are considered to be in contact with each other.

[0043] Particle analysis is performed on the portion (black portion) corresponding to cBN particles in the image obtained after the aforementioned binarization process. The maximum length of each cBN particle is then used as its diameter. As the particle analysis for determining the maximum length, the larger of the two lengths obtained by calculating the Frit diameter for a cBN particle is taken as the maximum length, and this maximum length is used as the diameter of each particle.

[0044] Assuming each particle is an ideal sphere with the specified diameter, the cumulative volume is calculated using the calculated volume as the volume of each particle. A graph is then plotted based on this cumulative volume, with the vertical axis representing volume percentage (%) and the horizontal axis representing diameter (μm). The diameter at 50% volume percentage is taken as the average particle size of the cBN particles. This process is applied to three observation regions, and their average value is taken as the average particle size (μm) of the cBN particles.

[0045] When performing particle analysis, the length (μm) of each pixel is set using a scale value known in advance from the SEM. The observation area used in image processing is preferably a region in which at least 30 cBN particles are observed, i.e., with an average cBN particle size of about 3 μm, for example, a field of view of about 15 μm × 15 μm is preferred.

[0046] (1-2) content

[0047] The content (volume%) of cBN particles in the cBN sintered body is preferably 40% or more and 70% or less.

[0048] The reason is that when the content is less than 40% by volume, there are fewer cBN particles acting as hard materials in the cBN sintered body, which sometimes reduces the resistance to defects. On the other hand, when the content is greater than 70% by volume, voids that can become crack initiation points are generated in the cBN sintered body, which sometimes reduces the resistance to defects. The cBN particle content is more preferably 45% by volume or more and 65% by volume or less.

[0049] The content of cBN particles in the cBN sintered body can be determined as follows: The cross-sectional microstructure of the cBN sintered body is observed using SEM; the cBN particle portion is extracted from the secondary electron image obtained through image processing; and the area occupied by the cBN particles is calculated through image analysis. The average value of the calculated area for at least three observation regions is taken as the cBN particle content (volume %). Preferably, the observation region used in image processing is one in which at least 30 cBN particles are observed, i.e., a field of view of approximately 15 μm × 15 μm, assuming an average cBN particle size of approximately 3 μm.

[0050] (2) Bonding phase

[0051] The bonding phase in this embodiment can be a bonding phase with a conventional composition, that is, a bonding phase using at least one or more particles selected from Ti nitrides, carbides, carbonitrides, borides and Al nitrides and oxides.

[0052] (3) Surface roughness

[0053] The surface roughness R of the cBN sintered body is preferably 0.1 μm or more and 1.5 μm or less. The reasons are as follows. When the surface roughness R is less than 0.1 μm, sufficient adhesion with layer A cannot be obtained. On the other hand, when the surface roughness R is greater than 1.5 μm, cBN particles will fall off at the interface between the substrate and layer A during cutting, which is prone to tool breakage. In addition, since the surface roughness of the coating layer is also greater than 1.5 μm, tool breakage or abnormal damage is likely to occur, and the surface roughness of the workpiece will also deteriorate. R is measured by SEM, and its definition will be described later (refer to 2.(6)).

[0054] 2. Coating layer

[0055] The coating layers include: an AlTiN layer as layer A; an AlTiSiN layer as layer B; an AlCrSiCuN layer as layer C; and a TiN layer, the average thickness of which is the combined average thickness of layers A, B, and C. T Preferably, the micrometer size is 1.0 μm or larger and 5.0 μm or smaller.

[0056] The reason is that, at an average thickness of tT When the thickness is less than 1.0 μm, sufficient wear resistance of the coating layer cannot be obtained. When the thickness is greater than 5.0 μm, the distortion in the coating layer will increase, and the coating layer is prone to self-destruction.

[0057] The AlTiN layer (layer A), AlTiSiN layer (layer B), AlCrSiCuN layer (layer C), and TiN layer will be described in turn.

[0058] (1) AlTiN layer as layer A

[0059] Regarding the AlTiN layer as layer A, its average composition is given by the formula: (Al 1-x Ti x When N is represented, x is preferably 0.35 to 0.60. The reason is that when x is less than 0.35, the grain distortion of the A layer becomes larger, and the A layer is prone to self-destruction. On the other hand, when x is greater than 0.60, the hardness of the A layer decreases, and its oxidation resistance also decreases. x is more preferably 0.40 or more and 0.55 or less.

[0060] Furthermore, according to one example of the manufacturing method described later, with (Al) 1-x Ti x It is manufactured with a 1:1 ratio of nitrogen to nitrogen, but sometimes, unavoidably (unintentionally), the ratio is not 1:1. This also applies to other nitrides described below (composite nitrides constituting B and C layers, and TiN, respectively).

[0061] In addition, the average thickness t of layer A A Preferably, the thickness is 0.1 μm or more and 1.0 μm or less. The reason for this is that, at an average thickness t... A When the thickness is less than 0.1 μm, layer A cannot function effectively as a tight bonding layer with the substrate, and peeling of the coating layer is likely to occur under high loads applied to the cutting edge. On the other hand, when the thickness is greater than 1.0 μm, the distortion in layer A increases, and layer A is prone to self-destruction. The average thickness t of layer A. A More preferably, the micrometer is 0.2 μm or more and 0.7 μm or less.

[0062] (2) AlTiSiN layer as B layer

[0063] Regarding the AlTiSiN layer as layer B, its average composition is given by the formula: (Al 1-y-z Ti y Si z When N is represented, y is preferably 0.35 or higher and 0.60 or lower, and z is preferably 0.01 or higher and 0.10 or lower. The reasons are as follows.

[0064] When y is less than 0.35, the grain distortion of the B layer increases, making the B layer prone to self-destruction. On the other hand, when y is greater than 0.60, the hardness and oxidation resistance of the B layer decrease. y is more preferably 0.40 or more and 0.55 or less. Furthermore, when z is less than 0.01, the B layer does not achieve sufficient wear resistance. When z is greater than 0.10, the lattice distortion of the B layer increases, and the damage resistance of the B layer becomes insufficient. z is more preferably 0.03 or more and 0.07 or less.

[0065] In addition, the average thickness t of layer B B Preferably, the thickness is 0.2 μm or more and 2.0 μm or less. The reason for this is that, at an average thickness t... B When the thickness is less than 0.2 μm, the B layer cannot fully function as a wear-resistant layer. On the other hand, when the thickness is greater than 2.0 μm, the distortion in the B layer increases, making it prone to self-destruction. The average thickness t of the B layer... B More preferably, the micrometer is 0.5 μm or more and 1.5 μm or less.

[0066] Here, it is preferable that there exists a tA between the average thickness tA of layer A and the average thickness tB of layer B. B / t A The relationship is between 2.0 and 6.0. The reason is that when it is less than 2.0, the proportion of layer B in the overall coating is small, so it cannot obtain sufficient wear resistance. On the other hand, when it is greater than 6.0, the coating is prone to peeling under high load on the tool tip (high load cutting).

[0067] (3) AlCrSiCuN layer as C layer

[0068] In the AlCrSiCuN layer, which serves as the C layer, each component has the following function.

[0069] That is, the Al component has the effect of improving high-temperature hardness, the Cr component has the effect of improving high-temperature toughness and high-temperature strength, and the high-temperature oxidation resistance when Al and Cr coexist. Furthermore, the Si component has the effect of improving heat resistance and plastic deformation, and the Cu component has the effect of improving wear resistance by achieving grain refinement.

[0070] Furthermore, regarding the AlCrSiCuN layer as the C layer, its average composition is given by the formula: (Al 1-a-b-c Cr a Si b Cu c When N is represented, a is preferably 0.150 or higher and 0.400 or lower, b is preferably 0.050 or higher and 0.200 or lower, and c is preferably 0.005 or higher and 0.050 or lower. The reasons are as follows.

[0071] When a is less than 0.150, the C layer cannot possess sufficient high-temperature toughness and high-temperature strength, thus failing to suppress the formation of cracks that cause chipping, defects, etc. On the other hand, when a is greater than 0.400, the wear resistance of the C layer decreases due to the relative reduction in Al content. A is more preferably 0.150 or more and 0.300 or less.

[0072] When b is less than 0.050, it is not expected that improving the wear resistance can be achieved by improving the heat resistance and plastic deformation of the C layer. On the other hand, when b is greater than 0.200, the wear resistance of the C layer will decrease. b is more preferably 0.070 or more and 0.150 or less.

[0073] When c is less than 0.005, no improvement in wear resistance can be expected. When c is greater than 0.050, particles are easily generated during the formation of the C layer, and the crack resistance of the C layer will decrease. c is more preferably 0.010 or higher and 0.040 or lower.

[0074] The average thickness t of layer C C Preferably, the thickness is 0.1 μm or more and 2.0 μm or less. The reason for this is that, at an average thickness t... C When the thickness is less than 0.1 μm, the C layer cannot function effectively as a chipping-resistant layer. On the other hand, when the thickness is greater than 2.0 μm, the distortion in the C layer increases, making it prone to self-destruction. The average thickness t of the C layer... C More preferably, the micrometer is 0.5 μm or more and 1.5 μm or less.

[0075] In addition, it is preferred to be in t C There exists R≤t between R and R. C The relationship is as follows: If this relationship holds, cracks generated during high-load cutting can be buffered (absorbed) in the C layer, thereby improving the chipping resistance of the coated tool. In other words, when this relationship does not hold, cracks propagate to the substrate during high-load cutting, causing all cBN particles to detach and resulting in chipping.

[0076] (4) TiN layer

[0077] A TiN layer can be further added on top of the C layer.

[0078] In the case of forming a TiN layer, since the TiN layer itself has a golden yellow hue, the TiN layer can be used as an identification layer (the composition of TiN is only required to make it golden yellow, and is not limited to a stoichiometric composition). This identification layer can determine whether the coating tool is unused or used based on the hue change of the surface.

[0079] Furthermore, the average thickness of the TiN layer serving as the identification layer can be between 0.1 and 1.0 μm. This is because when the thickness is less than 0.1 μm, interference fringes will be generated, and sometimes the identification layer cannot adequately visually recognize tonal changes. On the other hand, when the thickness is greater than 1.0 μm, the TiN layer can become a cause of chipping.

[0080] (5) Other layers

[0081] In this embodiment, film formation is performed without any layers other than layer A, layer B, and layer C. However, when the layer to be formed is changed (the film formation is changed to other adjacent layers), unintentional changes in pressure or temperature occur within the film forming apparatus. Sometimes, between the adjacent layers, unintentional oxygen- or carbon-containing layers with compositions different from those of the layers are formed.

[0082] (6) Measurements related to the coating layer

[0083] The surface of the matrix serving as the cBN sintered body is determined as follows: A longitudinal section is defined, and elemental mapping is performed in this section using energy dispersive X-ray spectroscopy (EDS) to determine the interface between the matrix and layer A (the beam diameter of EDS can be exemplified as 20 nm). Then, the average line of the roughness curve based on this interface is calculated arithmetically, and this average line is taken as the surface of the matrix.

[0084] The average line is a straight line m that crosses the roughness curve. It is drawn on the region enclosed by a roughness curve with a length of at least 15 μm (as defined in the longitudinal section, at least 15 μm in length in the direction parallel to the surface of the cBN sintered body treated as a plane), with the area of ​​this region being equal on both the upper and lower sides of the line m. Furthermore, when drawing the line m, portions of the roughness curve less than 10% of their maximum height (peak) and maximum depth (valley) are treated as noise and are not included in the area comparison when drawing the line.

[0085] Furthermore, the sum of the average absolute values ​​of the peak heights measured in the direction perpendicular to the average line, from the highest peak up to the fifth peak in descending order, and the average absolute values ​​of the valley depths measured in the direction of the deepest valley up to the fifth valley in descending order, is set as the surface roughness R.

[0086] If the surface of the substrate is determined, then using that surface as a reference, the average thickness of each of the layers A, B, C, and TiN (TiN layer is set as needed), as well as the average thickness of the coating layer, are measured. That is, multiple (three or more) perpendicular lines are drawn to the above average lines, the thickness is calculated according to each of these multiple perpendicular lines, and the average of the calculated thicknesses is taken as the average thickness.

[0087] In addition, the average composition of layers A, B and C was determined by SEM, transmission electron microscopy (TEM), and cross-sectional measurements were performed using energy-dispersive X-ray spectroscopy (EDS) with a beam diameter of 20 nm. The average value of the measured values ​​was then used to calculate the composition.

[0088] 3. Manufacturing method

[0089] The manufacturing method of the coating tool involved in this embodiment can be exemplified by the following method.

[0090] (1) cBN sintered body

[0091] The method for manufacturing cBN sintered bodies can use conventionally known methods. For example, cBN particles are prepared as raw material powder for forming the hard phase, and TiN powder, TiCN powder, Al powder, AlN powder, and Al2O3 powder are prepared as raw material powder for forming the binding phase. The mixtures are combined such that the cBN particle content is 40-70% by volume. After wet mixing and drying, the mixtures are stamped and pre-sintered at a specified temperature under a vacuum atmosphere. Then, the mixtures are placed in an ultra-high pressure sintering apparatus and sintered at a specified temperature.

[0092] (2) Covering layer

[0093] The coating layer can be manufactured by, for example, by arc ion plating (AIP), and film formation parameters such as arc voltage, reactive gas pressure, and bias voltage are adjusted. The arc ion plating (AIP) method uses a target composed of an alloy corresponding to the composition of each of the A layer, B layer, C layer and TiN layer (the TiN layer is set as needed).

[0094] The above description includes the following features.

[0095] (Postscript 1)

[0096] A surface-coated cutting tool, comprising a substrate and a coating layer disposed on the substrate, characterized in that,

[0097] The matrix is ​​a cubic boron nitride sintered body, wherein the average particle size of the cubic boron nitride is 0.5 μm or more and 6.0 μm or less, the content of the cubic boron nitride is 40% by volume or more and 70% by volume, and the surface roughness R of the matrix is ​​0.1 μm or more and 1.5 μm or less.

[0098] The coating layer has an average thickness of 1.0 μm or more and 5.0 μm or less, and has layers A, B, and C extending from the surface of the substrate toward the tool surface.

[0099] The average composition of layer A is (Al) 1-x Ti x N(0.35≤x≤0.60), the average thickness t of layer A. A The size is between 0.1 μm and 1.0 μm.

[0100] The average composition of layer B is (Al) 1-y-z Ti y Si z N(0.35≤y≤0.60, 0.01≤z≤0.10), the average thickness t of layer B. B The size is between 0.2 μm and 2.0 μm.

[0101] The average composition of the C layer is (Al) 1-a-b-c Cr a Si b Cu c N(0.150≤a≤0.400, 0.050≤b≤0.200, 0.005≤c≤0.050), the average thickness t of layer C. C The size is between 0.1 μm and 2.0 μm.

[0102] t B / t A For values ​​above 2.0 and below 6.0, R ≤ t C .

[0103] (Postscript 2)

[0104] The surface-coated cutting tool according to Appendix 1 is characterized in that it has a TiN layer on the C layer.

[0105] (Note 3)

[0106] The surface-coated cutting tool according to Appendix 1 or 2 is characterized in that the average particle size of the cubic boron nitride particles is 2.5 μm or more and 6.0 μm or less.

[0107] (Postscript 4)

[0108] The surface-coated cutting tool according to any one of Appendices 1 to 3 is characterized in that the content of the cubic boron nitride particles is 40% by volume or more and 70% by volume or less.

[0109] Example

[0110] The present invention is illustrated below with examples, but the present invention is not limited to the examples.

[0111] 1. Fabrication of cBN sintered body

[0112] As raw material powders, cBN particles with an average particle size of 2.5–6.0 μm were prepared as raw material powders for forming the hard phase. Additionally, TiN powder, TiC powder, TiCN powder, Al powder, AlN powder, and Al₂O₃ powder were prepared as raw material powders for forming the bonding phase, and were blended according to the proportions shown in Table 1. Furthermore, these raw material powders contain trace amounts of unavoidable impurities.

[0113] Next, after wet mixing the raw material powder in a ball mill for 72 hours and drying it, it was pressed into a size of 50 mm in diameter and 1.5 mm in thickness at a forming pressure of 100 MPa. The shaped body was then pre-sintered in a vacuum atmosphere at a pressure of less than 1 Pa at a specified temperature within the range of 1000 °C. Then it was placed in an ultra-high pressure sintering device and sintered at a specified temperature within the range of 5 GPa and 1300 °C to produce a cBN sintered body.

[0114] [Table 1]

[0115]

[0116] By cutting the sintered body into specified dimensions using a wire electrical discharge machining (EDM) machine, welding the welded portion (corner) of the WC-based cemented carbide insert body with a composition of Co: 5% by mass, TaC: 5% by mass, and WC: balance, and an insert shape conforming to ISO standard CNGA120408, using Ag-based solder (Cu: 26% by mass, Ti: 5% by mass, Ag: balance), and performing grinding and edge finishing on the top, bottom, and outer periphery, a cBN matrix 1-3 with an insert shape conforming to ISO standard CNGA120408 is manufactured.

[0117] 2. Film formation of the coating layer

[0118] For substrates 1 to 3, a coating layer is formed by the following steps (1) to (5) using an arc ion plating apparatus. In the arc ion plating apparatus, a target composed of an alloy corresponding to the composition of each of the A layer, B layer, C layer and TiN layer to be formed is arranged.

[0119] (1) With the substrates 1 to 3 ultrasonically cleaned in acetone and dried, they are mounted along the outer periphery at a position radially away from the central axis of the rotating stage in the arc ion plating apparatus.

[0120] (2) Exhaust the air from the arc ion plating apparatus and maintain a temperature of 10°C. -2While maintaining a vacuum below Pa, the apparatus is heated to 500°C using a heater, then an Ar gas atmosphere of 2.0 Pa is established. A DC bias voltage of -300V is applied to the substrate rotating on the aforementioned rotating stage, thereby bombarding the substrate surface with argon ions for 30 minutes. At this time, the bombardment conditions are controlled to achieve the specified R.

[0121] (3) The film formation of layer A is carried out in the following manner.

[0122] Nitrogen gas is introduced into the arc ion plating apparatus as a reaction gas, and the reaction atmosphere is set to the specified reaction atmosphere of 4.0 to 8.0 Pa as shown in Table 2. The temperature inside the apparatus is maintained as shown in Table 2. A specified DC bias voltage of -30 to -60 V as shown in Table 2 is applied to the substrate. At the same time, a specified current of 120 to 160 A as shown in Table 2 is flowed between the cathode electrode (evaporation source) and the anode electrode, which are composed of an Al-Ti alloy target with a specified composition, to generate an arc discharge. An A layer composed of an (Al, Ti)N layer with the composition and average thickness shown in Table 4 is deposited on the surface of the substrate 1.

[0123] (4) The film formation of layer B is carried out in the following manner.

[0124] Nitrogen gas is introduced into the arc ion plating apparatus as a reaction gas, and the reaction atmosphere is set within the range of 5.0 to 8.0 Pa as shown in Table 2. The temperature inside the apparatus is also maintained as shown in Table 2. A DC bias voltage within the range of -30 to -60 V as shown in Table 2 is applied to the substrate. A current within the range of 120 to 180 A as shown in Table 2 flows between the cathode electrode (evaporation source) and the anode electrode, which are composed of an Al-Ti-Si alloy target with a specified composition, to generate an arc discharge. A B layer with the composition and average thickness shown in Table 4 is deposited on the surface of the A layer.

[0125] (5) The film formation of layer C is carried out in the following manner.

[0126] Nitrogen gas is introduced into the arc ion plating apparatus as a reaction gas, and the reaction atmosphere is set within the range of 4.0 to 7.0 Pa as shown in Table 2. The temperature inside the apparatus is also maintained as shown in Table 2. A DC bias voltage within the range of -30 to -70 V as shown in Table 2 is applied to the substrate. A current within the range of 100 to 180 A as shown in Table 2 flows between the cathode electrode (evaporation source) and the anode electrode, which are composed of an Al-Cr-Si-Cu alloy target with a specified composition, to generate an arc discharge. A C layer with the composition and average thickness shown in Table 4 is deposited on the surface of the B layer.

[0127] As described above, the coating tools of the present invention (referred to as Examples) 1 to 10 were manufactured.

[0128] On the other hand, for comparison, for the above-mentioned cBN substrates 1 to 3, the conditions in (3) to (5) above were changed to the values ​​shown in Table 3 respectively, and the coating tools (referred to as comparative examples) 1 to 6 of the comparative examples shown in Table 5 were made.

[0129] Furthermore, in Examples 2, 3, 5, 6, 8 and 9 and Comparative Examples 3, 4 and 6, a cathode electrode (evaporation source) made of metallic Ti was attached in an arc ion plating apparatus, and a TiN layer with a thickness of 0.1 to 1.0 μm was further deposited on the coating layer under the following formation conditions.

[0130] Regarding the film formation conditions of the TiN layer, nitrogen gas was introduced into the arc ion plating apparatus as a reaction gas, and the reaction atmosphere was set to 5.0 Pa. The apparatus temperature of each embodiment and comparative example shown in Tables 2 and 3 was maintained. A DC bias voltage of -40 V was applied to the substrate, and a specified current of 120 A was simultaneously flowed between the cathode electrode (evaporation source) and the anode electrode composed of a Ti target for a specified time to generate an arc discharge, thereby forming the TiN layer.

[0131]

[0132]

[0133]

[0134]

[0135] Next, the following cutting tests were conducted on Examples 1-10 and Comparative Examples 1-6.

[0136] Cutting test

[0137] Workpiece: Round bar of JIS·SCr420 carburized and quenched material (HRC60)

[0138] Cutting speed: 200m / min

[0139] Depth of cut: 0.1mm

[0140] Feed rate: 0.15mm

[0141] Cut to a cutting length of 1000m and measure the wear on the flank face.

[0142] The results are shown in Table 6.

[0143] [Table 6]

[0144]

[0145] In Table 6, "※" indicates that the tool breaks before reaching the cutting length of the cutting test and thus reaches its lifespan. The time (sec) from the start of cutting to reach the lifespan is recorded.

[0146] Based on the results in Table 6, it was confirmed that Examples 1 to 10 were able to perform cutting without chipping and had excellent wear resistance.

[0147] On the other hand, it can be seen that Comparative Examples 1 to 6 reached their lifespan in a short time due to the occurrence of tool breakage or the progression of flank wear.

[0148] The embodiments disclosed above are merely exemplary in all respects and are not restrictive. The scope of the invention is defined by the claims, not by the foregoing embodiments, and is intended to include all modifications in the same sense and scope as the claims.

[0149] Explanation of reference numerals in the attached figures

[0150] 1. Matrix (cBN sintered body)

[0151] 2A layer (AlTiN layer)

[0152] 3B layer (AlTiSiN layer)

[0153] 4C layer (AlCrSiCuN layer)

[0154] 5 TiN layers

[0155] 6 cBN particles

[0156] 7. Binding phase

Claims

1. A surface-coated cutting tool, comprising a substrate and a coating layer disposed on the substrate, characterized in that, The substrate is a cubic boron nitride sintered body, wherein the average particle size of the cubic boron nitride is 2.5 μm or more and 6.0 μm or less, and the content of the cubic boron nitride is 40% by volume or more and 70% by volume or less. A straight line that crosses the surface roughness curve of the substrate and whose upper and lower sides of the surface roughness curve have equal areas is defined as the surface of the substrate. The portion of the surface roughness curve less than 10% of its maximum height and maximum depth is not included in the area comparison. When the surface roughness R is defined as the sum of the absolute values ​​of the peak heights measured in a direction perpendicular to the surface of the substrate, from the highest peak in descending order up to the fifth peak, and the absolute values ​​of the valley depths measured in a direction descending order from the deepest valley in descending order up to the fifth valley, the surface roughness R of the substrate is 0.1 μm or more and 1.5 μm or less. The coating layer has an average thickness of 1.0 μm or more and 5.0 μm or less, and has layers A, B, and C extending from the surface of the substrate toward the tool surface. The average composition of layer A is (Al) 1-x Ti x N, the average thickness t of layer A A The value is greater than 0.1 μm and less than 1.0 μm, where 0.35 ≤ x ≤ 0.

60. The average composition of layer B is (Al) 1-y-z Ti y Si z N, the average thickness t of layer B B The micrometer size is greater than 0.2 μm and less than 2.0 μm, where 0.35 ≤ y ≤ 0.60 and 0.01 ≤ z ≤ 0.

10. The average composition of the C layer is (Al) 1-a-b-c Cr a Si b Cu c N, the average thickness t of the C layer C The size is greater than 0.1 μm and less than 2.0 μm, where 0.150 ≤ a ≤ 0.400, 0.050 ≤ b ≤ 0.200, and 0.005 ≤ c ≤ 0.

050. t B / t A For values ​​above 2.0 and below 6.0, R ≤ t C .

2. The surface-coated cutting tool according to claim 1, characterized in that, A TiN layer is present on the C layer.

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