Surface coated cutting tools

Abstract

To provide a coated tool which secures deposition resistance by cutting cast iron, and has superior abrasion resistance and chipping resistance.SOLUTION: Provided is a surface-coated cutting tool with a substrate and a coating layer provided on a surface of the substrate. The coating layer has a laminate layer including one or more lamination units. The lamination units includes a first layer, a second layer and a third layer in this order from the substrate toward a tool surface. The first layer is TiCxN1-x with an average thickness of 0.3 μm to 3.0 μm (an average value xavg of x is 0.50≤xavg≤0.65). The second layer is TiCyN1-y with an average thickness of 0.3 μm to 3.0 μm (an average value yavg of y is 0.65<yavg≤0.75). The third layer is TiCzN1-z with an average thickness of 0.3 μm to 3.0 μm (an average value zavg of z is 0.75<zavg≤1.00).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] To improve the cutting performance of cutting tools, there are conventional coated tools in which a coating layer is formed on the surface of a substrate such as a tungsten carbide (hereinafter referred to as WC)-based cemented carbide by vapor deposition, and these are known to exhibit excellent wear resistance. While coated tools with the aforementioned conventional coating layer exhibit excellent wear resistance, various proposals have been made for further improvements to the coating layer.

[0003] For example, Patent Documents 1 and 2 describe a coating layer having a plurality of columnar crystals, each of which is TiC x N z-x The first unit layer (0.45≦x<0.70, 0.80≦z≦1.20) and TiC y N A-y A coated tool having a multilayer structure in which a second unit layer (0.70≦y≦1, 0.80≦A≦1.20) is alternately laminated is described, and this coated tool is said to have excellent wear resistance and chipping resistance. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-171546 [Patent Document 2] Japanese Patent Publication No. 2019-171547 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The present invention has been made in view of the above circumstances and proposals, and particularly aims to provide a coated tool having excellent wear resistance and chipping resistance while ensuring weld resistance in the cutting of cast iron.

Means for Solving the Problems

[0006] The surface-coated cutting tool according to an embodiment of the present invention has a substrate and a coating layer provided on the surface of the substrate, the coating layer has a laminate layer including one or more lamination units, the lamination unit includes, in order from the substrate toward the tool surface, a first layer, a second layer, and a third layer, each of the first layer, the second layer, and the third layer The composition is substantially constant, has no intentional change in composition, the first layer is TiC with an average thickness of 0.3 μm or more and 3.0 μm or less x N 1-x (average value x of x avg is such that 0.50 ≦ x avg ≦ 0.65), the second layer is TiC with an average thickness of 0.3 μm or more and 3.0 μm or less y N 1-y (average value y of y avg is such that 0.65 < y avg ≦ 0.75), the third layer is TiC with an average thickness of 0.3 μm or more and 3.0 μm or less z N 1-z (average value z of z avg is such that 0.75 < z avg ≦ 1.00).

[0007] Furthermore, the surface-coated cutting tool according to the embodiment may satisfy one or more of the following items (1) to (3).

[0008] (1) The lamination unit is 1 or more and 30 or less. (2) The average thickness of the laminate layer is 3.0 μm or more and 16.0 μm or less. (3) On the side of the tool surface of the layer closest to the tool surface in the laminate layer, it has one or more layers selected from a TiN layer, a TiCNO layer, an Al2O3 layer, and an AlTiN layer, either with or without a TiCN layer interposed therebetween. (4) Between the substrate and the laminate layer, it has one or more layers selected from a TiC layer, a TiN layer, a TiCN layer, and a TiCNO layer.

Advantages of the Invention

[0009] The surface-coated cutting tool, in particular, in the cutting of cast iron, has excellent wear resistance and chipping resistance while ensuring weld resistance.

Brief Description of the Drawings

[0010] [Figure 1] It is a schematic diagram showing a longitudinal section of a coating layer of a surface-coated cutting tool according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0011] According to the study of the present inventor, it has been found that the coated tools described in Patent Documents 1 and 2 are excellent in wear resistance and chipping resistance, but are insufficient in weld resistance, particularly in the cutting of cast iron.

[0012] When investigating the reason, it was found that the TiCN layer formed using a hydrocarbon gas such as C2H4 as a film-forming gas has fine crystal grains, so it has excellent wear resistance. However, as the C content increases, the affinity with Fe contained in the workpiece increases, resulting in a decrease in weld resistance.

[0013] Hereinafter, the coated tool according to the embodiment of the present invention will be described in detail. In this specification and the claims, when a numerical range is expressed as "M to N" (both M and N are numerical values), it is synonymous with "M or more and N or less", and the range includes the upper limit value (N) and the lower limit value (M). When only the unit is described for the upper limit value (N), the units of the upper limit value (N) and the lower limit value (M) are the same. Furthermore, the composition of compounds not expressed using a formula is not limited to stoichiometric compositions, but includes all conventionally known atomic ratios.

[0014] Figure 1 is a schematic diagram showing an example of a longitudinal cross-section of the coating layer of a surface-coated cutting tool according to an embodiment of the present invention (a cross-section perpendicular to the surface when the surface of the substrate is treated as a flat surface, ignoring minute irregularities on the substrate surface). The substrate (1) has a coating layer (10) on its surface, and the coating layer (10) has a base layer (2), a laminate layer (7), an intermediate layer (8), and an upper layer (9). The laminate layer (7) has two laminate units (6) including a first layer (2), a second layer (3), and a third layer (4). The base layer (2), intermediate layer (6), and upper layer (7) may be provided selectively, as will be explained below. This embodiment will be described in detail below.

[0015] 1.Coating layer Let's explain the coating layer.

[0016] (1) Laminate layer The laminated structure has one or more repetitions of a laminated unit consisting of three layers, a first layer, a second layer, and a third layer, arranged sequentially from the substrate side toward the tool surface. The number of repetitions should preferably be between 2 and 30. This is because the aforementioned objective can be reliably achieved within this range of repetitions.

[0017] Here, The first layer is TiC x N 1-x (The mean value of x) avg However, 0.50 ≤ x avg ≤0.65) The second layer is TiC y N 1-y (The mean value of y) avg However, 0.65< avg y≦0.75) The third layer is TiC z N 1-z (mean z avg However, 0.75 <z avg ≤1.00) Each is preferable. x avg , y avg , z avg These are the average values ​​for all layers 1, 2, and 2, respectively.

[0018] x avg , y avg and z avg The reason why it is preferable to set the range as described above is that within this range, the difference in the coefficient of thermal expansion due to differences in composition becomes appropriate, and the stress relaxation layer can be reliably performed.

[0019] The average thickness of the first layer is between 0.3 μm and 3.0 μm. The average thickness of the second layer is between 0.3 μm and 3.0 μm. The average thickness of the third layer is between 0.3 μm and 3.0 μm. This is preferable. If each layer has this average thickness, the propagation of cracks generated during machining can be suppressed more reliably (the average thicknesses of the first, second, and third layers may be the same or different). Furthermore, when the average thickness of the laminate layers is 3.0 μm or more and 16.0 μm or less, the propagation of cracks generated during machining can be suppressed even more reliably.

[0020] (2) Upper layer On the tool surface side of the laminate, one or more layers from among TiN, TiCNO, Al2O3, and AlTiN, each with an average thickness of 0.1 μm or more and 20.0 μm or less, may be provided as an upper layer, with a total average thickness of 1.0 μm or more and 25.0 μm or less (the aforementioned objectives can be achieved even without this layer). Providing this upper layer allows the coated tool to exhibit even better wear resistance and chipping resistance. Here, if the total average thickness of the upper layer is less than 1.0 μm, the upper layer will not function sufficiently, while if it exceeds 25.0 μm, the crystal grains of the upper layer tend to coarseen, making it more prone to chipping.

[0021] (3) Middle class An intermediate layer is more preferably provided between the laminate layer and the upper layer to improve the adhesion between the two layers (Figure 1 shows an embodiment with an upper layer and an intermediate layer, but even when an upper layer is provided, the intermediate layer may be omitted). The intermediate layer is preferably a TiCNO layer, and its total average thickness is preferably 0.3 to 3.0 μm. When the average thickness is within this range, the adhesion between the laminate layer and the upper layer is further improved.

[0022] (4) Base layer A base layer may be provided between the substrate and the laminated layer to improve adhesion between them (although the aforementioned objectives can be achieved even without it). The base layer is preferably one or more Ti compound layers from among TiC, TiN, TiCN, and TiCNO layers, with a total average thickness of 0.1 to 3.0 μm. When the total average thickness is within this range, the adhesion between the two is further improved.

[0023] (5) Other layers When switching deposition gases, a very small amount of a layer other than the first, second, third, Al2O3, AlTiN, TiN, and TiCNO layers may be unintentionally produced.

[0024] 2.Base (1) Composition Any substrate conventionally known as this type of substrate can be used, as long as it does not hinder the achievement of the objectives of the present invention. Examples include 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), cermets (those mainly composed of TiC, TiN, TiCN, etc.), ceramics (titanium carbide, silicon carbide, silicon nitride, aluminum nitride, aluminum oxide, etc.), and cBN sintered bodies, and any of these is preferable.

[0025] (2) Shape There are no particular restrictions on the shape of the base, as long as it is a shape used as a cutting tool; examples include the shape of the insert and the shape of the drill.

[0026] 3.Measurement method (1) Composition The composition of each layer can be measured by observing it at multiple locations (for example, five locations) using a transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDS), identifying each layer, measuring the composition of each layer, and averaging the results.

[0027] (2) Average thickness The average thickness of each layer constituting the coating layer can be obtained, for example, by preparing a sample for observation by cutting the coating layer in a longitudinal section at an arbitrary position using a focused ion beam system (FIB), a cross-section polisher (CP), etc., and then observing the longitudinal section at multiple locations (e.g., 5 locations) using a scanning electron microscope (SEM), a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), or an energy dispersive X-ray spectrometry (EDX) system attached to an SEM or TEM, identifying each layer, measuring the thickness of each layer, and averaging the results.

[0028] In determining the average thickness, the substrate surface, which serves as the starting point for the length in the thickness direction, is defined as the reference line of the interface roughness between the substrate and the coating layer (or the underlying layer, if there is one, as described later) in an observation image of a longitudinal section (approximately in the thickness direction) perpendicular to the substrate. That is, when the substrate has a planar surface such as an insert, elemental mapping using EDS is performed on the longitudinal section, and the interface between the coating layer and the substrate is determined by performing known image processing on the obtained elemental map. The average line y0 is then arithmetically calculated for the roughness curve of the interface between the coating layer and the substrate, and this is taken as the surface of the substrate.

[0029] Here, the method for arithmetically determining the mean line y0 is to approximate the interface roughness by f(x) (where x is the distance in the direction parallel to the substrate surface) when the y-axis is taken in the thickness direction of the longitudinal section and the x-axis is taken perpendicular to it, and perform the calculation shown in [1]. Here, the length of l is preferably 4 μm or more. Then, the direction perpendicular to this average line is defined as the direction perpendicular to the substrate (the thickness direction of the coating layer).

[0030]

number

[0031] Furthermore, even if the substrate has a curved surface, such as a drill, if the tool diameter is sufficiently large relative to the thickness of the coating layer, the interface between the coating layer and the substrate in the measurement area will be approximately flat, and the surface of the substrate can be determined by a similar method. That is, for example, in the case of a drill, elemental mapping using EDS is performed on the longitudinal section of the coating layer perpendicular to the axial direction, and known image processing is performed on the obtained elemental map to determine the interface between the coating layer and the substrate. The average line of the roughness curve of the interface between the coating layer and the substrate obtained in this way is arithmetically calculated and taken as the surface of the substrate. The direction perpendicular to this average line is taken as the direction perpendicular to the substrate (thickness direction).

[0032] 4. Manufacturing method The coating layer of the present invention can be manufactured, for example, by the CVD method under the following film formation conditions.

[0033] (1) Laminate layer The percentages below represent volume percentages (capacity percentages). (1-1) 1st layer TiCl4:1.0~3.0%, CH3CN:0.5~1.5%, N2:13.0~40.0%, H2:Remaining Temperature: 850~950℃ Pressure: 5.0~7.0kPa

[0034] (1-2)Second layer TiCl4:1.0~2.0%, CH3CN:0.1~1.0%, C2H4:0.3~2.0%, N2:0.0~40.0%, H2:Remaining Temperature: 850~950℃ Pressure: 5.0~7.0kPa

[0035] (1-3)Third layer TiCl4:1.0~3.0%, CH3CN:0.1~0.8%, C2H4:2.0~3.0%, N2:0.0~15.0%, H2:Remaining Temperature: 850~950℃ Pressure: 5.0~7.0kPa

[0036] (2) Upper layer TiN layer TiCl4: 2.0~5.0%, N2: 25.0~35.0%, H2: remainder TiC layer TiCl4:2.0~5.0%, CH4:5.0~13.0%, H2:Remaining TiCNO layer TiCl4:0.5~3.5%, CH3CN:0.2~1.5%, CO:0.1~0.3%, N2:35.0~45.0%, H2:Remaining AlTiN layer AlCl3:0.2~1.3%, TiCl4:0.1~0.5%, N2: 10.0~16.0%, NH3: 2.0~6.0%, H2: remainder Al2O3 layer AlCl3:1.0~3.0%, CO2:4.5~6.5%, HCl: 1.2~4.0%, H2S: 0.1~0.3%, H2: remainder Temperature: 850~1000℃ Pressure: 4.0~30.0kPa

[0037] (3) Middle class TiCNO layer TiCl4:0.5~3.5%, CH3CN:0.2~1.5%, CO:0.1~0.3%, N2:35.0~45.0%, H2:Remaining Temperature: 850~1000℃ Pressure: 5.0~30.0kPa

[0038] (4) Base layer The deposition conditions for the TiN layer, TiC layer, and TiCNO layer are the same as for the upper layer. TiCN layer TiCl4:1.0~3.0%, CH3CN:0.5~1.5%, N2: 13.0~18.0%, H2: remaining Temperature: 850~950℃ Pressure: 5.0~10.0 kPa [Examples]

[0039] Next, we will describe some examples. Here, we will describe a specific example of the coated tool of the present invention applied to an insert cutting tool using a WC-based cemented carbide as the base material. However, as mentioned above, the base material is not limited to WC-based cemented carbide, and the same applies when the coated tool is applied to drills, end mills, etc.

[0040] First, Co powder, TiC 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, wax was added, and the mixture was wet-mixed in a ball mill for 72 hours. After drying under reduced pressure, the mixture was press-molded at a pressure of 100 MPa. These compacted bodies were sintered and processed to the specified dimensions to produce substrates A to C made of WC-based cemented carbide with insert shapes conforming to ISO standard CNMA120412. Note that each powder contained trace amounts of unavoidable impurities.

[0041] Next, on these substrates A to C, the coated tools 1 to 8 of the examples shown in Table 5 were obtained according to the conditions shown in Tables 2 and 4. In the column for the type of upper layer where two types of layers are listed, the left layer is the laminated layer, and the average thickness corresponding to each is also listed.

[0042] For comparison, coating layers were formed on the surfaces of these substrates A to C under the film formation conditions shown in Tables 3 and 4, to obtain comparative example coated tools 1 to 8 shown in Table 5.

[0043] [Table 1]

[0044] [Table 2]

[0045] [Table 3]

[0046] [Table 4]

[0047] [Table 5]

[0048] In Table 5, "-" indicates that the layer does not exist, and the layer on the right in the upper layer column is present on the coated tool surface, with its average thickness being the value on the right.

[0049] Next, for the coated tools of Examples 1-8 and the coated tools of Comparative Examples 1'-8', wet cutting tests 1 and 2, as described below, were performed with the tools clamped to the tip of a tool steel cutting tool using a fixing jig, and the wear of the flank surface of the cutting edge was measured. The results of each cutting test are shown in Tables 6 and 7.

[0050] Cutting Test 1: Wet Continuous Outer Diameter Cutting Workpiece material: FCD700 round bar with outer diameter φ300mm Cutting speed: 300m / min Cut: 2.5 mm Feed rate: 0.25 mm / rev Cutting time: 5 minutes Cutting oil material: Water-soluble cutting oil

[0051] Cutting Test 2: Wet Intermittent End Face Cutting Workpiece material: FCD700 round bar with 4 slits, outer diameter φ300mm Cutting speed: 250m / min Cut: 2.0 mm Feed rate: 0.2 mm / rev Cutting time: 5 minutes Cutting oil material: Water-soluble cutting oil

[0052] [Table 6]

[0053] [Table 7]

[0054] In Tables 6 and 7, the cutting time (minutes) until the end of life of the comparative coated tool refers to the cutting time (minutes) until the tool reaches the end of life due to chipping.

[0055] As shown in Tables 6 and 7, the coated tools 1 to 8 of the examples all have excellent wear resistance and chipping resistance while ensuring the welding resistance of the coating layer. Therefore, even when used for cutting cast iron, no chipping occurs, and they exhibit excellent wear resistance over a long period of time. In contrast, the coated tools 1 to 8 of the comparative examples, which do not satisfy even one of the requirements specified for the coated tools of the present invention, experience chipping when used for cutting cast iron and reach the end of their service life in a short time. [Explanation of Symbols]

[0056] 1 Base 2 Base layer 3 1st layer 4 2nd layer 5 3rd layer 6. Laminate Unit 7. Laminated layer 8. Middle layer 9 Upper layer 10 Covering layer

Claims

1. A surface-coated cutting tool having a substrate and a coating layer provided on the surface of the substrate, The coating layer has a laminated layer containing one or more lamination units, The aforementioned layered unit includes, in order from the substrate toward the tool surface, a first layer, a second layer, and a third layer. Each of the first, second, and third layers has a substantially constant composition. The first layer is TiC with an average thickness of 0.3 μm or more and 3.0 μm or less. ｘ N １－ｘ (The mean value of x) ａｖｇ However, 0.50 ≤ x ａｖｇ ≤ 0.65) The second layer is TiC with an average thickness of 0.3 μm or more and 3.0 μm or less. ｙ N １－ｙ (mean value of y) ａｖｇ However, 0.65 < y ａｖｇ ≤0.75) The third layer is TiC with an average thickness of 0.3 μm or more and 3.0 μm or less ｚ N １－ｚ (average value of z, z ａｖｇ where 0.75 < z ａｖｇ ≦ 1.00) A surface-coated cutting tool characterized by the following features.

2. The surface-coated cutting tool according to claim 1, characterized in that the number of lamination units is 1 or more and 30 or less.

3. A surface-coated cutting tool according to claim 1 or 2, characterized in that the average thickness of the laminated layer is 3.0 μm or more and 16.0 μm or less.

4. On the tool surface side of the layer closest to the tool surface of the laminate, with or without a TiCN layer, there are TiN layers, TiCNO layers, and Al ２ O ３ A surface-coated cutting tool according to any one of claims 1 to 3, characterized by having one or more layers, either a layer or an AlTiN layer.

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