Coated tool

Abstract

Provided is a coated tool comprising a hard film on a base material. The hard film is a sputtering film, wherein the hard film has an intermediate film and a laminated film. An a1 layer and an a2 layer are alternately laminated. In atomic ratio to the total amount of metallic elements including a semi-metal, the a1 layer is a nitride or carbonitride containing 65-85% of Al, and 15-35% of Cr, wherein the total content of Al and Cr is 90-100%. The a2 layer is a nitride or carbonitride containing 50-70% of Al, wherein the total content of Cr and / or Ti is 30-50%, and the total content of Al and Cr and / or Ti is 90-100%. The a1 layer has an Al content larger than that of the a2 layer, and the a1 layer has an average film thickness of 0.08-0.5 μm, which is greater than that of the a2 layer. The intermediate film has a thickness greater than the average film thickness of the a1 layer, and the laminated film is thicker than the intermediate film.

Description

Covered tools

[0001] The present invention relates to a coating tool applicable to tools such as molds and cutting tools. This application claims priority based on Japanese Patent Application No. 2025-005661, filed in Japan on January 15, 2025, the contents of which are incorporated herein by reference.

[0002] AlCr nitride is a film type with excellent wear resistance and heat resistance, and is widely used as a coated mold and coated cutting tool. In recent years, coated tools with Al-rich AlCr nitride containing more than 70 atomic percent of Al have begun to be proposed by the arc ion plating method (Patent Documents 1-3). Furthermore, the applicant of this application has proposed coated tools with Al-rich AlCr nitride using the high-power sputtering method (Patent Documents 4-6).

[0003] Japanese Patent Publication No. 2016-032861, Japanese Patent Publication No. 2018-059146, Japanese Patent Publication No. 2020-040175, International Publication No. 2023 / 022230, International Publication No. 2024 / 048304, International Publication No. 2024 / 048306

[0004] The inventors have confirmed that when the Al content of Al-rich AlCr nitride produced by high-power sputtering reaches 80 atomic percent, the film contains a large number of brittle hexagonal crystals, which can degrade the film properties and reduce the durability of the coated tool. In view of the above circumstances, the present invention aims to provide a coated tool provided with an Al-rich AlCr nitride or carbonitride that exhibits excellent durability.

[0005] The present invention relates to a coating tool comprising a substrate and a hard coating on the substrate, wherein the hard coating is a sputtering coating, and comprises an intermediate coating with a cubic crystal structure made of nitride or carbonitride formed on the substrate, and a laminated coating formed on the intermediate coating, wherein the laminated coating is alternately laminated with an a1 layer which is a nitride or carbonitride in which, in terms of atomic ratio of the total amount of metal elements including metalloids, Al is 65% or more and 85% or less, Cr is 15% or more and 35% or less, and the sum of Al and Cr is 90% or more and 100% or less, and an a2 layer which is a nitride or carbonitride in which Al is 50% or more and 70% or less, the sum of either Cr or Ti or both is 30% or more and 50% or less, and the sum of Al and either Cr or Ti or both is 90% or more and 100% or less, and the a1 layer has a higher Al content than the a2 layer. The coating tool is characterized in that the a1 layer has an average film thickness of 0.08 μm or more and 0.5 μm or less, and is thicker than the average film thickness of the a2 layer, the intermediate film has a film thickness thicker than the average film thickness of the a1 layer, and the laminated film is thicker than the intermediate film. In this specification, the cubic intermediate film is also simply referred to as the "intermediate film". In this specification, the laminated film is formed by alternately stacking a1 and a2 layers, with each a1 layer being deposited on top of an a2 layer, and vice versa, forming a laminate of multiple a1 and a2 layers.

[0006] The average thickness of layer a1 is preferably 1.1 to 3 times the average thickness of layer a2. The laminated film preferably has a higher Al content near the surface than near the intermediate film. The laminated film preferably contains Ar at an atomic ratio of 0.2% or less relative to the total amount of metallic and nonmetallic elements, including metalloids. The "total amount of metallic and nonmetallic elements, including metalloids" refers to the total amount of all chemical elements present in the corresponding film, i.e., the total amount of all metals, metalloids, and nonmetals contained in the film. An upper layer may be provided on the laminated film.

[0007] According to the present invention, a coating tool with excellent durability can be provided.

[0008] This is an example of a cross-sectional observation photograph (magnification 30,000x) of this embodiment 1.

[0009] The inventors have confirmed that, with respect to Al-rich AlCr nitrides or carbonitrides produced by high-power sputtering, controlling the design of the film structure according to the present invention prevents an excessive amount of hexagonal crystals from forming in the film, thereby suppressing a decrease in film properties. This will be explained in detail below.

[0010] The coated tool of this embodiment has a sputtering coating, which is a hard coating applied to the surface of a substrate using a sputtering method. Specifically, the coated tool of this embodiment is a coated tool having a substrate, an intermediate coating formed on the surface of the substrate, and a laminated coating formed on the intermediate coating. An upper layer may be provided on the laminated coating as needed. The coated tool of this embodiment can be applied to molds and cutting tools. In particular, it is preferable to apply it to small-diameter end mills with a tool diameter of 6 mm or less, and more preferably 3 mm or less.

[0011] In this embodiment, the base material is not particularly limited. Cold work tool steel, hot work tool steel, high-speed steel, cemented carbide, etc., may be used as appropriate depending on the application. The base material may also be pre-treated with nitriding or metal bombardment.

[0012] The coating tool of this embodiment has a cubic crystal structure intermediate film (hereinafter simply referred to as "intermediate film") made of nitride or carbonitride formed on the substrate. This improves the adhesion between the substrate and the laminated film and suppresses the deterioration of film properties due to an excess of hexagonal crystals in the laminated film. The intermediate film is preferably a nitride or carbonitride containing one or more of Al, Cr, and Ti in an atomic ratio of 90% to 100% or less relative to the total amount of metal elements including metalloids. For example, AlCrN, AlTiN, AlCrTiN, CrN, TiN, etc. can be selected. If the crystal structure of the intermediate film is cubic, it may contain metal elements including metalloids other than Al, Cr, and Ti as needed. The intermediate film may be a single layer or a multilayer. In addition, a metal layer, alloy layer, carbide layer, etc. may be provided separately between the substrate and the intermediate film. To improve adhesion with the laminated film, the intermediate film is preferably a nitride or carbonitride in which, in terms of atomic ratio of the total amount of metal elements including metalloids, Al is 50% to 70%, Cr is 30% to 50%, and the sum of Al and Cr is 90% to 100%.

[0013] The coated tool of this embodiment has a laminated coating on an intermediate coating. In this embodiment, the laminated coating consists of alternating layers a1 and a2. Layer a1 is a nitride or carbonitride in which, in terms of atomic ratio of metal elements including metalloids, Al is 65% to 85%, Cr is 15% to 35%, and the sum of Al and Cr is 90% to 100%. Layer a1 has a higher Al content than layer a2. By using layer a1, which has a higher Al content, in the laminated coating, the Al content of the laminated coating can be increased. Preferably, layer a1 is a nitride or carbonitride in which, in terms of atomic ratio of metal elements including metalloids, Al is 70% to 82%, Cr is 18% to 30%, and the sum of Al and Cr is 90% to 100%.

[0014] The a2 layer is a nitride or carbonitride with an Al content of 50% to 70%, a total of Cr, Ti, or both of them of 30% to 50%, and a total of Al and either Cr, Ti, or both of them of 90% to 100%. Having the a2 layer within this composition range allows the crystal structure of the a2 layer to be cubic throughout the entire laminated film. That is, all a2 layers included in the laminated film can be made into films with a cubic crystal structure. By alternately laminating cubic a2 layers with Al-rich a1 layers, it is possible to suppress the excessive hexagonal crystal structure in the overall laminated film, which would degrade the film properties. Preferably, the a2 layer is a nitride or carbonitride with an Al content of 50% to 63%, a total of either Cr, Ti, or both of them of 47% to 50%, and a total of Al and either Cr, Ti, or both of them of 90% to 100%. The a2 layer is preferably a nitride or carbonitride having an Al content of 50% to 63%, a Cr content of 47% to 50%, and a total Al and Cr content of 90% to 100%.

[0015] To achieve a high level of both heat resistance and wear resistance in coated tools, it is preferable that the a1 layer has a higher Al content (10% to 30% more) than the a2 layer. The compositions of the a1 and a2 layers described above are the average compositions of each layer. The average composition of the a1 and a2 layers can be measured from the cross-sectional structure of a mirror-finished surface. It can be determined by analyzing the area near the center of each layer and taking the average.

[0016] In this embodiment, the laminated film tends to have a higher Al content near the surface than near the intermediate film. The a2 layer, which has a relatively low Al content, can be cubic throughout the entire thickness range of the laminated film (all a2 layers in the laminated film can have a cubic structure), but the a1 layer, which has a high Al content, may have a mixture of cubic and hexagonal structures near the surface. Even if some of the multiple a1 layers are layers with a mixture of cubic and hexagonal structures, it is sufficient that the peak intensity attributable to the cubic structure of the entire laminated film shows the maximum intensity in X-ray diffraction. The a1 layer near the surface may have a higher Al content in the range of 3% to 15% than the a1 layer near the intermediate film. Preferably, the number of layers of a1 and a2 is 4 to 15. In this embodiment, the vicinity of the intermediate film is the range of up to 4 layers of a1 and a2 combined in the film thickness direction from the interface between the intermediate film and the laminated film. In this embodiment, the vicinity of the surface refers to the area within four layers (a1 and a2 combined) from the surface of the laminated film.

[0017] If the average thickness of layer a1 becomes too small, the overall Al content of the laminated film decreases, reducing its heat resistance. Conversely, if the average thickness of layer a1 becomes too large, the adhesion of the laminated film decreases, and the hexagonal crystal structure becomes excessive, degrading the film's properties. Therefore, the average thickness of layer a1 should be between 0.08 μm and 0.5 μm. Preferably, the average thickness of layer a1 should be between 0.1 μm and 0.3 μm. Furthermore, the average thickness of layer a1 should be thicker than the average thickness of layer a2. Making layer a1, which has a higher Al content, thicker can improve the heat resistance of the laminated film. Preferably, the average thickness of layer a1 is between 1.1 and 3 times the average thickness of layer a2. The thickness of layers a1 and a2 may vary from the substrate side to the surface side. The thickness of the hard film can be measured from a mirror-finished cross-sectional observation photograph. The average thickness of layers a1 and a2 can be determined by measuring the thickness of three or more layers and averaging them.

[0018] In this embodiment, the coating tool has an intermediate film that is thicker than the average film thickness of the a1 layer. This improves the adhesion between the substrate and the laminated film, and also suppresses the excess of hexagonal crystals in the laminated film that is placed on top of the intermediate film. Furthermore, the laminated film is made thicker than the intermediate film. This results in a thicker Al-rich laminated film, which improves the heat resistance and wear resistance of the coating tool. The film thickness of the laminated film is preferably 1.2 μm or more and 5 μm or less.

[0019] The a1 layer may contain metal elements including metalloids other than Al and Cr. For example, the a1 layer may contain one or more elements selected from groups 4a, 5a, and 6a of the periodic table and Si, B, Y, Yb, and Cu, for the purpose of improving wear resistance and heat resistance. These elements are generally included to improve the coating properties of coated tools and can be added in a range that does not significantly reduce the durability of the coated tool. However, if the content of metal elements including metalloids other than Al and Cr becomes too high, the durability of the coated tool may decrease. Therefore, when the a1 layer contains metal elements including metalloids other than Al and Cr, it is preferable that the atomic ratio of these elements to the total amount of metal elements including metalloids is 10% or less. Furthermore, it is preferable that it be 5% or less.

[0020] The a2 layer may contain metal elements including metalloids other than Al, Cr, and Ti. For example, the a2 layer may contain one or more elements selected from groups 4a, 5a, and 6a of the periodic table, and Si, B, Y, Yb, and Cu, for the purpose of improving wear resistance and heat resistance. These elements are generally included to improve the coating properties of coated tools and can be added in a range that does not significantly reduce the durability of the coated tool. However, if the content of metal elements including metalloids other than Al, Cr, and Ti becomes too high, the durability of the coated tool may decrease. Therefore, when the a2 layer contains metal elements including metalloids other than Al, Cr, and Ti, it is preferable that the atomic ratio of these metal elements to the total amount of metal elements including metalloids is 10% or less. Furthermore, it is preferable that it be 5% or less.

[0021] In this embodiment, the laminated film preferably contains Ar at an atomic ratio of 0.2% or less relative to the total amount of metallic elements, including metalloids, and nonmetallic elements. Although the hard film according to the present invention contains Ar because it is a sputtering film, excessive Ar in the laminated film reduces its durability. The durability of the coated tool can be further improved by ensuring that the laminated film, which is the main layer of the hard film, contains Ar at an atomic ratio of 0.2% or less relative to the total amount of metallic elements, including metalloids, and nonmetallic elements. The laminated film according to the present invention may contain Ar at an atomic ratio of 0.02% or more relative to the total amount of metallic elements, including metalloids, and nonmetallic elements. "Total amount of metallic elements, including metalloids, and nonmetallic elements" means all elements present in the film whose Ar content is being measured.

[0022] In this embodiment, the laminated film preferably contains N at an atomic ratio of 51% to 53% of the total amount of metallic and nonmetallic elements, including metalloids. A higher N content in the laminated film tends to reduce the amount of hexagonal crystals in Al-rich layers.

[0023] The coated tool of this embodiment may have an upper layer on top of the laminated film. By providing an upper layer, the wear resistance of the coated tool can be improved. For example, an AlCr-based nitride or carbonitride with the same composition as layers a1 and a2, but thicker than layers a1 and a2, may be used as the upper layer. Alternatively, an AlCr-based nitride or carbonitride with a different composition from layers a1 and a2 may be used as the upper layer. Furthermore, a TiSi-based nitride or carbonitride, which is a film type with excellent wear resistance, may be used as the upper layer.

[0024] <Manufacturing Method> In the coating of the hard film according to this embodiment, a sputtering method is used. Among sputtering methods, it is preferable to apply a high-power sputtering method in which three or more alloy targets are used, power is applied sequentially to the targets, and when the target to which power is applied switches, power is applied simultaneously to both the target to which power application has ended and the target to which power application has started for a period of time. With such a sputtering method, a state of high ionization rate of the targets is maintained during coating, a dense hard film at the micro level is obtained, and the inevitably contained argon and oxygen tend to be low. Furthermore, the furnace temperature of the sputtering apparatus (temperature inside the coating chamber) is set to 200°C to 500°C, the negative pressure bias voltage applied to the substrate is set to -200V to -40V, and Ar gas and N ２ It is preferable to introduce gas to set the furnace pressure (pressure inside the coating chamber) to 0.1 Pa to 1.0 Pa. When coating with carbonitride, a small amount of carbon can be added to the target, or a portion of the reaction gas can be replaced with methane gas.

[0025] The maximum power density of a power pulse is 0.1 kW / cm². ２ The above is preferable. In this specification, the power density of a power pulse always refers to the power density input to the target. Furthermore, 0.3 kW / cm² ２ The above is preferable. Furthermore, in this composition system, if the energy of the film-forming ions becomes too high, a hexagonal crystal structure is more likely to form. Therefore, the maximum power density of the power pulse is 0.7 kW / cm². ２ The following is preferable. Furthermore, 0.6 kW / cm² ２ The following is preferable: The duration of the power pulse applied to each target is preferably 5 milliseconds or less. Furthermore, the time during which power is simultaneously applied to both the alloy target where power application ends and the alloy target where power application begins is preferably 10 microseconds or more and 100 microseconds or less.

[0026] <Substrate>As the substrate, a two-flute ball end mill made of cemented carbide with a composition of WC (bal.) - Co (8 mass%) - TaC (0.3 mass%) and a hardness of 93.5 HRA (Rockwell hardness, value measured according to JIS G 0202) was prepared.

[0027] The film forming apparatus used was the HIPIMS apparatus INLENIA manufactured by CemeCon. The tool as the substrate was fixed to the sample holder in the sputtering apparatus, and a bias power supply was connected to the tool. The bias power supply is structured to apply a negative bias voltage to the tool independently of the target. The tool rotates at 2 revolutions per minute and revolves through the fixing jig and the sample holder. The distance between the tool and the target surface was set to 100 mm. The introduced gas was Ar and N ２ and was introduced from the gas supply port provided in the sputtering apparatus.

[0028] <Bombardment treatment>First, before coating the tool with the hard film, the tool was bombarded in the following procedure. Heating was performed for 30 minutes with the furnace temperature in the sputtering apparatus reaching 400 °C by the heater. Then, the inside of the sputtering apparatus was evacuated, and the furnace pressure was set to 5.0×10 －３ Pa or less. Then, Ar gas was introduced into the furnace of the sputtering apparatus, and the furnace pressure was adjusted to 0.8 Pa. Then, a DC bias voltage of -170 V was applied to the tool, and cleaning of the tool with Ar ions (bombardment treatment) was performed for 20 minutes or more.

[0029] In the coating of Example 1, the furnace temperature was set to 300 °C, and Ar gas (0.43 Pa) and N ２ gas (0.31 Pa) were introduced into the furnace of the sputtering apparatus to set the furnace pressure to 0.74 Pa. A DC bias voltage was applied to the substrate, the time when the power applied to the target overlapped was set to 50 microseconds, and the discharge time per cycle of the power applied to each target was set to 1 millisecond. Then, the maximum bias voltage of the negative pressure applied to the substrate was -120 V, and the maximum power was 0.4 kW / cm ２In this method, an electric current was continuously applied to an AlCr-based alloy target to coat the surface of the substrate with an intermediate film, and then a laminated film was applied on top of the intermediate film.

[0030] In contrast to Example 1, Examples 2, 3, and 5 varied the composition of the laminated film. In Example 4, the laminated film was formed with a furnace pressure of 0.85 Pa during film formation. In Comparative Examples 1 and 2, a single layer of Al-rich AlCrN was coated on top of the intermediate film.

[0031] An X-ray diffractometer (EMPYREAN, manufactured by PaNallytical Co., Ltd.) was used to confirm the properties of the X-ray structure under the following measurement conditions: tube voltage 45 kV, tube current 40 mA, X-ray source Cukα (λ = 0.15405 nm), and 2θ 20 to 80 degrees. For each sample, no diffraction peaks clearly attributable to a hexagonal crystal structure were observed, and it was confirmed that diffraction peaks attributable to a cubic crystal structure showed the highest intensity.

[0032] To confirm the film structure, cross-sectional observation was performed using a field emission transmission electron microscope (JEM-2010F, JEOL Ltd.). The sample was cut and bonded to a dummy substrate using epoxy resin. Subsequently, cutting, bonding of a molybdenum reinforcement ring, polishing, dimpling, and Ar ion milling were performed to prepare the sample for measurement. Carbon deposition was performed before measurement. Observation, compositional analysis, and nanobeam diffraction were performed at an accelerating voltage of 200 kV. The composition of the laminated film was determined by energy-dispersive X-ray spectroscopy (EDS). Measurements were taken near the center of each layer, and the average values ​​were taken as the compositions of layers a1 and a2.

[0033] The hardness and elastic modulus of the hard coating were measured using a nanoindentation tester (ENT-2100, manufactured by Elionix Co., Ltd.).

[0034] The film composition of the laminated film was measured using the wavelength-dispersive electron probe microanalysis (WDS-EPMA) attached to the electron probe microanalyzer (JXA-8500F, manufactured by JEOL Ltd.). The measurement conditions were: acceleration voltage 10 kV, irradiation current 5 × 10⁻¹⁰ －８A. With an acquisition time of 10 seconds, five measurements were taken within a 1 μm diameter area, and the amounts of Ar and N were determined from the average value to represent the atomic ratio of the total amount of metallic and nonmetallic elements, including metalloids. For each sample, the Ar content was 0.1% or less. The N content was 51% to 53%.

[0035]

[0036] Figure 1 shows an example of a cross-sectional observation photograph of Example 1. It can be confirmed that there is an intermediate film on the surface of the substrate, and a laminated film on top of the intermediate film. In all samples, the Al content of the laminated film was approximately 5% higher in atomic ratio near the surface than near the intermediate film. In Example 1, all layers had a cubic crystal structure, resulting in high hardness and elastic modulus. In Example 2, the Al content of layer a1 is higher than that of layer a2. In the laminated film, layer a1 located near the intermediate film had a cubic crystal structure, but near the surface of the laminated film, layer a1 had both cubic and hexagonal crystal structures. Therefore, it is presumed that the hardness was lower compared to Example 1. In Example 3, the Al content of layer a2 is higher than that of layer a1. In the laminated film, both layers a1 and a2 had a cubic crystal structure near the intermediate film, but near the surface, layer a1 had both cubic and hexagonal crystal structures. Therefore, it is presumed that the hardness was lower compared to Example 1. This embodiment 4 involves coating with a high nitrogen pressure inside the furnace during film formation. All layers in this embodiment 4 have a cubic crystal structure and exhibit higher hardness than this embodiment 1. It is presumed that increasing the nitrogen pressure during coating reduced the amount of hexagonal crystal structure present at the micro level, resulting in higher hardness and elastic modulus. This embodiment 5 involves making part of the laminated film AlTiN. Compared to this embodiment 1, the hardness and elastic modulus were lower, but compared to comparative examples 1 and 2 of the single-layer film, the elastic modulus was higher.

[0037] The adhesion of Comparative Example 1 was extremely low. It is presumed that the Al-rich single-layer film became thicker, resulting in a greater proportion of hexagonal crystal structures and thus a weaker film. In Comparative Example 2, the Al-rich single-layer film was thinner compared to Comparative Example 1, and the adhesion was improved, but the hardness and elastic modulus were lower compared to Example 1.

[0038] Cutting evaluation was performed under the following conditions. Table 2 shows the cutting test results. Dry machining tool: Two-flute carbide ball end mill Model number: EPDBE2060-12, ball radius 6 mm Cutting method: Face milling Workpiece material: S50C (220 HB) Depth of cut: Axial direction, 0.24 mm; radial direction, 0.24 mm Cutting speed: 141 m / min Feed per tooth: 0.13 mm / tooth Evaluation method: Evaluate the machining time until tool life is reached

[0039]

[0040] It was confirmed that all of these examples were superior in durability to the single-layer comparative examples. Among them, Example 1 had an optimized film structure and showed excellent durability.

[0041] In the context of this specification, particularly with regard to the determination of the concentration of chemical elements in the described films, the following terms are used: "Metal element" refers to metals such as aluminum (Al), as well as transition metals such as chromium (Cr) and titanium (Ti). "Metalloid" refers to one or more metalloids such as boron, silicon, or germanium, if present in the corresponding layer. "Non-metal element" refers to any element present in the corresponding layer that is neither a metal nor a metalloid.

Claims

1. A coating tool comprising a substrate and a hard coating on the substrate, wherein the hard coating is a sputtering coating, and comprises an intermediate coating with a cubic crystal structure made of nitride or carbonitride formed on the substrate, and a laminated coating formed on the intermediate coating, wherein the laminated coating consists of alternating layers: an a1 layer which is a nitride or carbonitride with an atomic ratio of Al to the total amount of metal elements including metalloids of 65% to 85%, Cr to 15% to 35%, and the sum of Al and Cr to 90% to 100%, and an a2 layer which is a nitride or carbonitride with an Al content of 50% to 70%, the sum of either Cr or Ti or both to 30% to 50%, and the sum of Al and either Cr or Ti or both to 90% to 100%, and the a1 layer has a higher Al content than the a2 layer. A coating tool characterized in that the a1 layer has an average film thickness of 0.08 μm or more and 0.5 μm or less, and is thicker than the average film thickness of the a2 layer, the intermediate film is thicker than the average film thickness of the a1 layer, and the laminated film is thicker than the intermediate film.

2. The coating tool according to claim 1, characterized in that the average film thickness of the a1 layer is 1.1 times or more and 3 times or less the average film thickness of the a2 layer.

3. The coating tool according to claim 1, characterized in that the laminated film has a higher Al content near the surface than near the intermediate film.

4. The coated tool according to any one of claims 1 to 3, characterized in that the laminated film contains Ar in an atomic ratio of 0.2% or less relative to the total amount of metallic elements including metalloids and nonmetallic elements.

5. The coating tool according to claim 1, characterized in that it has an upper layer on top of the laminated film.

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