Surface coated cutting tools

Abstract

A surface-coated cutting tool wherein a coating layer includes a layer in which a first layer and a second layer are laminated in an alternating manner with an average thickness of 0.1-10.0 μm. The first layer has an average thickness of 0.5-100.0 nm and an average composition of (AlxTi1-x-y-zMy)BzN (where M is one or more elements selected from the among group 4, group 5, and group 6 of the periodic table and lanthanoids, x is 0.100-0.640, y is 0.001-0.100, and z is 0.060-0.400). The second layer has an average thickness of 0.5-100.0 nm and an average composition of (AlpCr1-p)N (where p is 0.650-0.900). The content of B in the edge ridgeline of the coating layer is not less than 60% with respect the content of B in a region 1 mm or more away from the edge ridgeline of the coating layer in the flank surface direction.

Description

[Technical Field]

[0001] The present invention relates to a surface-coated cutting tool (hereinafter sometimes referred to as a coated tool). This application claims priority to Japanese Patent Application No. 2021-46163, filed on March 19, 2021. The entire contents of said Japanese patent application are incorporated herein by reference. [Background technology]

[0002] BACKGROUND ART Conventionally, a coated tool has been known in which a coating layer is formed on a tool substrate (substrate) such as a tungsten carbide (hereinafter referred to as WC) based cemented carbide. It has been proposed to obtain a coating layer with higher hardness by adjusting the composition of this coating layer.

[0003] For example, Patent Document 1 discloses a method for forming a thin film (Al x Ti 1-x )(B y N 1-y ) (x is 0.05 to 0.75, y is 0.02 to 0.12), and has an average thickness of 0.5 to 8.0 μm. The coated tool is said to exhibit excellent wear resistance and have low reactivity with iron-based work materials (low weldability) due to the boron (B) added to the coating layer to form the boron nitride layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-26756 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above circumstances and proposals, and an object of the present invention is to provide a coated tool that exhibits excellent wear resistance even when subjected to high-speed cutting of martensitic stainless steel or the like at a cutting speed that is 30% or more higher than usual. [Means for solving the problem]

[0006] The surface-coated cutting tool according to an embodiment of the present invention comprises: 1) A substrate and a coating layer on the surface of the substrate, 2) The coating layer includes a layer having an average thickness of 0.1 μm or more and 10.0 μm or less, in which first and second layers are alternately laminated, 3) The first layer has an average thickness of 0.5 nm or more and 100.0 nm or less, and an average composition of (Al x Ti 1-x-y-z M y )B z N (where M is one or more elements selected from Groups 4, 5, and 6 of the periodic table and the lanthanides, x is 0.100 or more and 0.640 or less, y is 0.001 or more and 0.100 or less, and z is 0.060 or more and 0.400 or less), 4) The second layer has an average thickness of 0.5 nm or more and 100.0 nm or less, and an average composition of (Al p Cr 1-p )N (p is 0.650 or more and 0.900 or less), 5) The B content at the cutting edge ridge of the coating layer is 60% or more of the B content in a region of the coating layer that is 1 mm or more away from the cutting edge ridge in the flank direction. It is characterized by: [Effects of the Invention]

[0007] The surface-coated cutting tool exhibits excellent wear resistance and chipping resistance even when used for high-speed cutting of stainless steels such as martensitic stainless steels. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a schematic diagram of a vertical cross section showing an example of a coating layer in a surface-coated cutting tool according to an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a schematic diagram showing a cutting edge ridgeline of a surface-coated cutting tool according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present inventors have conducted extensive research into coated tools that exhibit excellent wear resistance even when used for high-speed cutting of stainless steels such as martensitic stainless steels. As a result, they concluded that a coating layer containing B has excellent wear resistance but is brittle, and therefore, simply providing a coating layer containing B would not be enough to achieve both wear resistance and fracture resistance.

[0010] On the other hand, the inventors of the present invention considered that, considering the principles of ion plating, because B is a light element at the cutting edge, the content of B at the cutting edge will be reduced by re-sputtering in areas away from the cutting edge, and the effect of improving hardness due to the inclusion of B will not be fully exerted. As a result, the hardness will differ between the cutting edge and other areas, and wear will not progress uniformly, resulting in abnormal damage such as chipping.

[0011] Based on these considerations, the present inventors conducted further studies and discovered that if a layer that does not contain B is included in the coating layer to compensate for the brittleness of the layer that contains B and to suppress the occurrence of abnormal damage to the coating layer, and if the decrease in the B content at the cutting edge ridge is suppressed to improve the high-temperature hardness, the coating layer can exhibit excellent wear resistance.

[0012] The coated tool according to the embodiment of the present invention will be described in more detail below. In this specification and claims, when a numerical range is expressed using "A to B," this is equivalent to "A or more, B or less," and the range includes the numerical values ​​of the upper limit (B) and the lower limit (A). Furthermore, when a unit is stated only for the upper limit (B), the upper limit (B) and the lower limit (A) have the same unit. The layer structure of the coating layer of the coated tool according to the embodiment of the present invention is as shown schematically in FIG.

[0013] 1.Coating layer The coating layer will be described below.

[0014] (1) Average thickness In the coated tool according to this embodiment, the average thickness of the layer formed by alternating first and second layers included in the coating layer is preferably 0.1 μm or more and 10.0 μm or less. The reason for specifying this range for the average thickness is that if the average thickness is less than 0.1 μm, excellent wear resistance cannot be achieved over long periods of use, while if the average thickness is more than 10.0 μm, the crystal grains in the coating layer tend to become coarse, preventing improvement in chipping resistance. The average thickness is more preferably 0.8 μm or more and 8.0 μm or less.

[0015] (2) Composition of the coating layer As shown schematically in FIG. 1, the coating layer (2) in the coated tool according to this embodiment is provided on a base body (1) and includes a first layer (3) and a second layer (4) that are alternately laminated.

[0016] (2-1) 1st layer The first layers each have an average thickness of 0.5 nm or more and 100.0 nm or less, and the average composition obtained by averaging the compositions of all the stacked first layers is (Al x Ti 1-x-y-z M y )B z Preferably, the content of B is N (wherein M is one or more elements selected from Groups 4, 5, and 6 of the periodic table and the lanthanides, x is 0.100 or more and 0.640 or less, y is 0.001 or more and 0.100 or less, and z is 0.060 or more and 0.400 or less). The content z of B is sufficient as long as it satisfies the above range in the first layer as a whole, and may be locally outside the above range. Here, the elements of groups 4, 5 and 6 of the periodic table refer to Zr, Hf, V, Nb, Ta, Cr, Mo and W.

[0017] The reason why the above range is preferable for the average thickness is that if it is less than 0.5 nm, the improvement in crack propagation resistance brought about by the laminated structure cannot be fully exhibited, while if it exceeds 100.0 nm, the improvement in wear resistance brought about by the nano-lamination cannot be fully exhibited.

[0018] The reason why the above range is preferable as the average composition is as follows. If x is less than 0.100, the heat resistance of the first layer cannot be sufficiently improved by adding Al, while if x exceeds 0.640, the hardness of the first layer decreases and sufficient wear resistance cannot be achieved. If y is less than 0.001, the addition of M does not sufficiently improve the heat resistance and mechanical properties of the first layer, while if y exceeds 0.100, the toughness of the first layer decreases, making chipping and fracture more likely to occur. If z is less than 0.060, the addition of B cannot sufficiently improve the hardness of the first layer. 0.400 If the temperature exceeds this value, the toughness of the first layer decreases, and chipping and fractures become more likely to occur.

[0019] (2-2) Second layer The second layer has an average thickness of 0.5 nm or more and 100.0 nm or less per layer, and all the laminated first layers 2 The average composition of the layers was calculated as follows: (Al p Cr 1-p )N (p is preferably 0.650 or more and 0.900 or less).

[0020] The reason why the above range is preferable for the average thickness is that if it is less than 0.5 nm, the improvement in crack propagation resistance brought about by the laminated structure cannot be fully exhibited, while if it exceeds 100.0 nm, the improvement in wear resistance brought about by the nano-lamination cannot be fully exhibited.

[0021] The reason why the above range is preferable as the average composition is as follows. If p is less than 0.650, the effect of adding Al to improve the heat resistance of the second layer is not sufficiently obtained, while if it exceeds 0.900, the hardness of the second layer decreases and sufficient wear resistance cannot be exhibited.

[0022] (2-3) The first and second layers are laminated alternately. The first and second layers are preferably laminated alternately in the thickness direction. By alternately laminating the first layer, which has wear resistance due to the increased B content, the second layer, which does not contain B, compensates for the brittleness of the first layer, and the coating layer as a whole exhibits excellent wear resistance and chipping resistance even when used in high-speed cutting of stainless steels such as martensitic stainless steels. If the first and second layers are alternately stacked, the layer closest to the substrate and tool surface Either of the layers closest to the first layer may be the first layer or the second layer.

[0023] There are no particular restrictions on the number of layers in the first and second layers, as long as the first and second layers each satisfy the average thickness ranges described above and the average thickness of the coating layer also satisfies the average thickness range described above. However, to reliably achieve the above-described object, the number of layers (the sum of the number of layers in the first and second layers) is more preferably 50 to 1,000.

[0024] (2-4) B content at the cutting edge The B content at the cutting edge of the coating layer is preferably 60% or more of the B content in a region 1 mm or more away from the cutting edge in the flank direction of the coating layer. There is no upper limit to this B content, but in production by the PVD method described below, 100% is the approximate upper limit. The B content can be considered to be a constant value at a distance of 1 mm or more from the cutting edge ridge in the flank direction. Therefore, in the examples described below, the B content is measured at a point on a line 1.5 mm away from the cutting edge ridge in the flank direction.

[0025] Here, the B content can be considered to be a constant value means that, for any line segment parallel to the cutting edge ridgeline and spaced 1 mm or more from the cutting edge ridgeline in the flank face direction, the average value of the B content at any five points on this line segment is substantially the same value, i.e., coincides within the margin of error.

[0026] The B content of the coating layer at the cutting edge ridge being 60% or more of the B content in a region of the coating layer 1 mm or more away from the cutting edge ridge in the flank direction means, for example, that when the B content in the region 1 mm or more away from the cutting edge ridge in the flank direction is z=0.15, i.e., 15 atomic %, the B content at the cutting edge ridge is 9 (=0.15×60 / 100) atomic % or more. This prevents a decrease in the B content at the cutting edge ridge, improves the high-temperature hardness of the coating layer, and enables it to exhibit excellent wear resistance.

[0027] As shown in Figure 2, when the cutting face (5) and the flank (6) are approximated by straight lines, the cutting edge ridgeline is the point on the surface of the coating layer (the point indicated by the dotted arrow) that is closest to the intersection of the approximate straight lines within the area formed by connecting points on the cutting face and the flank where the straight lines are spaced apart from each other (i.e., the area from the bending point of the cutting face on the surface of the coating layer to the bending point of the flank).

[0028] The object of the present invention can be achieved by having the first and second layers. However, when a TiN layer is formed as the upper layer of the coating layer, the TiN layer itself has a golden color tone (the composition of the TiN layer is golden). tone The composition is not limited to the stoichiometric composition as long as it shows the above formula (1). For example, it can be used as an identification layer that can distinguish whether a cutting tool is unused or used by a change in color tone of the upper layer. The average thickness of the TiN layer serving as the discrimination layer may be, for example, 0.1 μm or more and 1.0 μm or less.

[0029] (4) Unintended demographic In this embodiment, the films are formed so that no layers other than the first layer, second layer, and upper layer (TiN layer) exist; however, when changing the layer to be formed (changing the film formation to another adjacent layer), an unintended fluctuation in pressure occurs within the film formation apparatus, and a layer containing unintended oxygen or carbon and having a different composition from the adjacent layers may be formed between the adjacent layers.

[0030] In this embodiment, the average thickness of each layer can be determined by observing a cross section in the layer thickness direction (a cross section perpendicular to the horizontal plane when the substrate surface is treated as a horizontal plane, ignoring minute irregularities on the substrate surface) using an energy dispersive X-ray spectrometer (EDS) attached to a scanning electron microscope (SEM) or a transmission electron microscope (TEM). That is, for example, the thickness is determined at multiple points (e.g., five points) at a magnification of 5000 times, and the average is calculated.

[0031] The average composition is determined by observing a longitudinal section using TEM-energy dispersive X-ray spectroscopy (EDS) and performing multiple (e.g., five) line analyses in the thickness direction to determine the average amounts of Al, Ti, Cr, and M. The B content z is determined by using an electron probe microanalyzer (EPMA) to determine the Al, Ti, Cr, M, and B contents from the surface to the entire coating layer. Because the second layer does not contain B, the ratio of the Ti and B contents in the first layer is the same as the ratio of the Ti and B contents in the entire coating layer. Therefore, the B content of the first layer is determined from the Ti and M contents determined by TEM-EDS and the Ti, M, and B contents determined by EPMA.

[0032] 2.Base (1)Material The substrate used in this embodiment can be any conventionally known substrate material as long as it does not hinder the achievement of the above-mentioned object. For example, it is preferably any of cemented carbide (WC-based cemented carbide, WC, Co, and Ti, Ta, Nb, etc. carbonitrides), cermet (TiC, TiN, TiCN, etc. as the main component), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), cBN sintered body, or diamond sintered body.

[0033] (2) Shape The shape of the substrate is not particularly limited as long as it is a shape that can be used as a cutting tool, and examples thereof include the shape of an insert and the shape of a drill.

[0034] 3. Manufacturing method The coating layer of the coated tool of the present invention can be produced using a film-forming device equipped with a vapor deposition source for arc ion plating (AIP), a type of PVD. Arc discharge is generated using an AlTiMB (where M is one or more elements selected from Groups 4, 5, 6, and the lanthanides of the periodic table) target for the first layer and an AlCr target for the second layer. The first and second layers are alternately laminated, and the bias voltage and arc current are controlled to ensure that the B content at the cutting edge ridge is 60% or more of the B content in a region 1 mm or more away from the cutting edge in the flank direction. [Example]

[0035] Next, an example will be described. Here, as an example of the coated tool of the present invention, we will describe an application of the coated tool to an insert cutting tool using a WC-based cemented carbide as the substrate. However, the substrate may be made of any of the above-mentioned materials, and the same applies when the coated tool is applied to cutting tools such as drills and end mills.

[0036] First, Co powder, TiC powder, VC powder, TaC powder, NbC powder, Cr3C2 powder, and WC powder were prepared as raw material powders. These raw material powders were blended according to the composition shown in Table 1, and wax was added and the mixture was wet mixed in a ball mill for 72 hours. The mixture was then dried under reduced pressure and pressed at a pressure of 100 MPa. These green compacts were sintered and processed to the specified dimensions to produce WC-based cemented carbide substrates 1 to 3 having the insert shape of ISO standard SEEN1203AFTN1.

[0037] Next, to form a coating layer on substrates 1 to 3 using a film-forming device with an AIP evaporation source, they were ultrasonically cleaned in acetone and, in a dried state, mounted along the outer periphery at a predetermined radial distance from the central axis on a rotary table in the device. In addition, an AlTiMB (M was as shown in Table 3) target and an AlCr target were placed as cathode electrodes (evaporation sources).

[0038] Next, the film forming apparatus was evacuated and -2 While maintaining a vacuum of 100 Pa or less, the inside of the apparatus was heated to 400°C with a heater, and then the atmosphere was set to 1.0 Pa with Ar gas, and a DC bias voltage of -1000 V was applied to the substrate rotating on the turntable, and the substrate surface was bombarded with argon ions for 60 minutes. Although not performed in this example, metal ion bombardment may also be performed using a metal target.

[0039] Nitrogen gas having a partial pressure in the range of 0.1 to 9.0 Pa shown in Table 2 was introduced into the film-forming apparatus as a reactive gas for a predetermined time, and the furnace temperature was maintained at the same temperature shown in Table 2. A predetermined DC bias voltage in the range of -10 to -500 V shown in Table 2 was applied to the substrate rotating on the rotary table (the same range for both the first and second layers). A predetermined current in the range of 80 to 240 A shown in Table 2 was applied to generate an arc discharge, and coated tools 1 to 9 of the present invention (hereinafter referred to as "Examples") shown in Table 3 were deposited. (However, Example 5 is a reference example.) was produced.

[0040] On the other hand, for comparison, a coating layer was formed by vapor deposition on the substrates 1 to 3 under the conditions shown in Table 2 using the same film forming apparatus as above. Covering Tools (hereinafter referred to as "Comparative Examples") 1 to 9 were produced.

[0041] The average thickness of the first and second layers constituting the coating layer and the average composition of the coating layer were determined by the above-mentioned methods.

[0042] The B content at the cutting edge ridge of the coating layer and the B content in a region of the coating layer 1 mm or more away from the cutting edge ridge in the flank direction were determined using an EPMA at five points (with a 0.5 mm interval between each point on the line segment) on the cutting edge ridge of the coating layer and on a line segment parallel to the cutting edge ridge at a distance of 1.5 mm from the cutting edge ridge in the flank direction, and the average value was calculated.

[0043] [Table 1]

[0044] [Table 2]

[0045] The furnace temperature, DC bias voltage value, and arc current value shown in Table 2 were constant during the film formation period.

[0046] [Table 3]

[0047] [Table 4]

[0048] In Table 4, "-" indicates that it is not contained.

[0049] Next, ExampleA single-blade face milling test was performed using an SE445R0506E cutter on Tools 1 to 9 and Comparative Example Tools 1 to 9. That is, Cutting Test A and Cutting Test B were performed as high-speed cutting tests on stainless steel such as martensitic stainless steel.

[0050] Cutting test A: Workpiece: 60mm wide x 200mm long block material Cutting speed: 160 m / min. Cutout: 1.5 mm Feed: 0.12 mm / tooth. Wet high-speed cutting tests were conducted on martensitic stainless steel SUS420J2 under the following conditions. The cutting length was 1.8m, the flank wear width was measured, and the state of wear on the cutting edge was observed. The results of cutting test A are shown in Table 5.

[0051] Cutting test B: Workpiece: 60mm wide x 200mm long block material Cutting speed: 170 m / min. Cutout: 1.5 mm Feed: 0.10 mm / tooth. We conducted a wet high-speed cutting test of austenitic stainless steel SUS304 under the conditions above. The cutting length was 1.8 m, the flank wear width was measured, and the state of wear on the cutting edge was observed. The results of cutting test B are shown in Table 6.

[0052] [Table 5]

[0053] [Table 6]

[0054] In Tables 5 and 6, "*" indicates that the tool reached the end of its service life before reaching the cutting length (1.8 m), and indicates the time (seconds) until the tool reached its end of service life.

[0055] According to the results in Tables 5 and 6, Examples 1 to 4 and 6~ For No. 9, no abnormal damage such as chipping or peeling occurred under either cutting condition A or B, demonstrating excellent wear resistance and chipping resistance. In contrast, it is clear that in Comparative Examples 1 to 9, under both cutting conditions A and B, chipping occurs or flank wear progresses, causing the tool to reach the end of its life in a short period of time.

[0056] The above-disclosed embodiments are merely illustrative in all respects and are not restrictive. The scope of the present invention is defined by the claims, not by the above-disclosed embodiments, and is intended to include meanings equivalent to the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0057] 1 Base 2 Covering layer 3 1st layer 4 2nd layer 5. Rake face 6 Flank

Claims

[Claim 1] A surface-coated cutting tool having a substrate and a coating layer on a surface of the substrate, 1) The coating layer includes a layer having an average thickness of 0.1 μm or more and 10.0 μm or less, in which first layers and second layers are alternately laminated, 2) The first layer has an average thickness of 0.5 nm or more and 100.0 nm or less, and an average composition of (Al ｘ Ti １－ｘ－ｙ－ｚ M ｙ ) B ｚ N (wherein M is one or more elements selected from Groups 4, 5, and 6 of the periodic table and the lanthanides; x is 0.100 or more and 0.640 or less; y is 0.001 or more and 0.100 or less; and z is 0.060 or more and 0.400 or less), 3) The second layer has an average thickness of 0.5 to 100.0 nm and an average composition of (Al ｐ Cr １－ｐ ) N (p is 0.650 or more and 0.900 or less); 4) The B content at the cutting edge ridge of the coating layer is 60% or more of the B content in a region of the coating layer that is 1 mm or more away from the cutting edge ridge in the flank direction. A surface-coated cutting tool characterized by:

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