Coated cutting tools

Abstract

The present invention relates to a coated cutting tool in which the surface of a substrate is coated with a hard film. The hard film includes an A layer of a face-centered cubic lattice structure and a B layer of a face-centered cubic lattice structure, wherein the A layer is arranged on the surface of the substrate and contains the most W among metal (including semi-metal) elements, followed by the most Ti, and the total content ratio of W and Ti is 85 atomic % or more, and the B layer is arranged on the A layer and is composed of a nitride or carbonitride containing Al, Cr and Si, wherein the content ratio (atomic %) of Al among metal (including semi-metal) elements is 50% or more, the total content ratio (atomic %) of Al and Cr is 85% or more, and the content ratio (atomic %) of Si is 4% or more and 15% or less.

Description

Technical Field

[0001] The present invention relates to a covered cutting tool such as an end mill.

[0002] This application claims priority based on patent application No. 2019-233353 filed in Japan on December 24, 2019, and the contents are incorporated herein by reference. Background Art

[0003] AlCrSi nitride or carbonitride is a type of film with excellent heat resistance and wear resistance, and is suitable for coating cutting tools. As a tool suitable for milling of high-hardness steel, the inventors have proposed the following coated cutting tool (Patent Document 1): the coated cutting tool has an intermediate film containing W and Ti with an hcp structure formed directly above the substrate by Ti bombardment, and an AlCrSi nitride or carbonitride is provided directly above the intermediate film to increase the Si content ratio and refine the film structure.

[0004] Patent Document 1: International Publication No. 2014 / 156699

[0005] The coated cutting tool described in Patent Document 1 is a tool with excellent durability in cutting high-hardness steel. On the other hand, the inventors have confirmed that the composition of the intermediate film formed by Ti bombardment is prone to variation. If the composition of the intermediate film varies greatly, the durability of the hard film is likely to vary depending on the processing conditions or tool shape, and there is also the possibility that the tool performance is unstable. Summary of the invention

[0006] The present inventors found the following findings and completed the present invention.

[0007] The inventors set the composition of the intermediate film formed by Ti bombardment to a composition mainly composed of W and Ti, in which the amount of the component of the hard film provided directly above the intermediate film is small. The inventors confirmed that by setting the intermediate film to the above composition, the composition deviation of the intermediate film is small, and the crystal structure becomes a face-centered cubic lattice structure. In addition, the inventors confirmed that by forming a hard film composed of AlCrSi-based nitride or carbonitride with adjusted Si content on the intermediate film of the face-centered cubic lattice structure, a coated cutting tool with excellent durability can be obtained.

[0008] That is, the present invention is a coated cutting tool in which the surface of a substrate is coated with a hard film. The hard film includes an A layer of a face-centered cubic lattice structure and a B layer of a face-centered cubic lattice structure, wherein the A layer is arranged on the surface of the substrate and contains the most W among metal (including semi-metal) elements, followed by the largest content of Ti, and the total content ratio of W and Ti is 85 atomic % or more, and the B layer is arranged on the A layer and is composed of a nitride or carbonitride containing Al, Cr and Si, wherein the content ratio (atomic %) of Al among metal (including semi-metal) elements of the nitride or carbonitride containing Al, Cr and Si is 50% or more, the total content ratio (atomic %) of Al and Cr is 85% or more, and the content ratio (atomic %) of Si is 4% or more and 15% or less.

[0009] It is preferred that the total content of W and Ti in the metal (including semi-metal) elements of the A layer is 85 atomic % or more.

[0010] It is preferred that the total content of Al and Si in the metal (including semi-metal) elements of the A layer be 10 atomic % or less.

[0011] A C layer may be further provided on the B layer, wherein the C layer is composed of a nitride or a carbonitride of a metal (including a semimetal).

[0012] The C layer is preferably a nitride or carbonitride in which the content ratio (atomic %) of Ti in metal (including semimetal) elements is 50% or more and the content ratio (atomic %) of Si is 1% or more and 30% or less.

[0013] According to the present invention, a coated cutting tool having excellent durability can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a transmission electron micrograph of the blade of the tool of Example 1. In the figure, the point 1 is the substrate, the point 2 is the A layer, and the point 3 is the B layer.

[0015] Figure 2 This is a diagram showing the restricted field diffraction pattern of the substrate of Example 1.

[0016] Figure 3 This is a diagram showing the results of composition analysis of the substrate of Example 1.

[0017] Figure 4 This is a diagram showing the limited field diffraction pattern of the A layer in Example 1.

[0018] Figure 5 This is a diagram showing the composition analysis results of the A layer in Example 1.

[0019] Figure 6This is a diagram showing the limited field diffraction pattern of the B layer in Example 1.

[0020] Figure 7 This is a diagram showing the composition analysis results of the B layer in Example 1. DETAILED DESCRIPTION

[0021] The inventors have studied the damage factors of coated cutting tools in high-efficiency processing of high-hardness steel, and confirmed that film damage is likely to occur starting from the columnar grain boundary that forms the hard film. In addition, it was found that it is very effective to reduce the grain boundary that becomes the starting point of damage by refining the film structure on the basis of nitrides or carbonitrides mainly composed of Al and Cr, wherein the nitrides or carbonitrides mainly composed of Al and Cr are types of films with excellent heat resistance and wear resistance. In addition, it was found that in order to further improve the adhesion between the substrate and the hard film caused by refining the structure of the hard film, an intermediate film with a face-centered cubic lattice structure (fcc structure) was provided, thereby completing the present invention. The present invention is described in detail below.

[0022] The coated cutting tool of this embodiment comprises a substrate, an A layer disposed on the surface of the substrate, and a B layer disposed on the A layer. In the coated cutting tool of this embodiment, the B layer is a hard film that imparts durability to the tool. The A layer is an intermediate film that improves the adhesion between the B layer and the substrate.

[0023] As the substrate, a WC-based cemented carbide substrate for cutting tools can be used. The substrate can be a tool with a cutter head and a shank integrated, a cutter head of a head-exchangeable tool, or a cutting insert mounted on a tool holder.

[0024] First, the B layer which is the hard film of the present invention will be described.

[0025] The B layer is a hard film composed of nitride or carbonitride mainly composed of Al and Cr, which is provided on the A layer described later. Nitrides or carbonitrides mainly composed of Al and Cr are the types of films that can exert excellent wear resistance and heat resistance as a coating on cutting tools. A more preferred material for the B layer is a nitride with excellent heat resistance.

[0026] Al is an element that imparts heat resistance to the hard film. In order to impart better heat resistance to the hard film, the content of Al in the content ratio of metal (including semi-metal, the same below) elements in the B layer (atomic %, the same below) is set to 50% or more. Furthermore, it is preferred to set the Al content ratio of the B layer to 55% or more. On the other hand, when the Al content ratio is too much, the B layer is mainly composed of a close-packed hexagonal structure (hcp structure), and there is a tendency for the durability of the coated cutting tool to decrease. Therefore, it is preferred to set the Al content ratio of the B layer to 70% or less. Regarding the B layer, in order to take into account both heat resistance and wear resistance at a high level, the total content ratio of Al and Cr is set to 85% or more. Furthermore, it is preferred to set the total content ratio of Al and Cr in the B layer to 90% or more.

[0027] Cr is an element that sets the crystal structure of the B layer to a face-centered cubic lattice structure (fcc structure) and improves the wear resistance and heat resistance of the coated cutting tool. When the Cr content is too low, the B layer is mainly composed of a hexagonal close-packed structure (hcp structure), and there is a tendency for the durability of the coated cutting tool to decrease. Therefore, the Cr content of the B layer is preferably 20% or more. In addition, the semi-metal in the present invention is Si and B (boron).

[0028] Si is an important element for refining the structure of nitrides or carbonitrides mainly composed of Al and Cr. The columnar particles of AlCrN without Si and AlCrSiN with a low Si content are coarse. The hard film with this organizational morphology has a tendency to increase the back-tool wear because there are many grain boundaries that become the starting point of film destruction. On the other hand, the structure of AlCrSiN containing a certain amount of Si becomes finer, for example, it is difficult to observe clear columnar particles in the cross-sectional observation using an electron microscope (20,000 times). For the hard film with this organizational morphology, there are fewer columnar grain boundaries that become the starting point of destruction, which can suppress the back-tool wear. However, when the Si content ratio increases, the B layer tends to be amorphous and hexagonal close-packed structure (hcp structure) as the main body, and the durability of the coated cutting tool is reduced. In order to fully refine the film structure without reducing the durability of the coated cutting tool, it is important to set the Si content ratio of the B layer to more than 4% and less than 15%. The Si content ratio of the B layer is preferably more than 5%. The Si content of the B layer is preferably 10% or less.

[0029] In the coated cutting tool of the present embodiment, it is important that the B layer is a face-centered cubic lattice structure (fcc structure). In the present embodiment, the so-called face-centered cubic lattice structure (fcc structure) means that the diffraction intensity caused by the face-centered cubic lattice structure (fcc structure) indicates the maximum intensity in X-ray diffraction. Since the hard film whose diffraction intensity caused by the close-packed hexagonal structure (hcp structure) indicates the maximum intensity is very fragile, it lacks durability as a coated cutting tool. In particular, there is a tendency for durability to decrease in wet processing.

[0030] It is preferable that no diffraction intensity due to the ZnS type crystal structure is confirmed in X-ray diffraction for the B layer. However, if the diffraction intensity due to the NaCl type crystal structure shows the maximum intensity, the B layer may partially contain a hexagonal close-packed structure (hcp structure) and an amorphous phase.

[0031] However, when the inspection area of ​​the membrane is small, or when other membranes described later are coated on the B layer, it is sometimes difficult to determine the face-centered cubic lattice structure (fcc structure) by the above-mentioned X-ray diffraction. Even in this case, for example, the crystal structure can be determined by the restricted field diffraction method using a transmission electron microscope (TEM).

[0032] The microstructure of the B layer in this embodiment is a microstructure in which a crystal phase with a relatively small Si content relative to the total Si content is dispersed in a crystal phase with a relatively large Si content relative to the total Si content. By making the B layer such a microstructure, a higher residual compressive stress is imparted to the hard film, and the development of cracks is also suppressed at the microscopic level. Therefore, it is believed that excellent durability can be exerted. In general, when the Si content ratio increases, nitrides or carbonitrides mainly composed of Al and Cr tend to become microstructures mainly composed of amorphous phases, and there is a tendency for toughness to decrease.

[0033] The B layer of the present embodiment is a layer having a crystal structure of a crystalline phase. In order to improve the crystallinity of the B layer, the magnetic flux density near the substrate is increased in the film forming device for coating. Specifically, in the film forming device, the average magnetic flux density near the center of the target is above 14mT. In addition, permanent magnets are provided on the back and periphery of the target, and a cathode adjusted to reach the vicinity of the substrate is used to coat the B layer. In addition, when the absolute value of the negative bias voltage applied to the substrate becomes smaller, there is a tendency for the amorphous phase to increase. In the coating of the B layer, it is preferably coated with a bias voltage of more than -250V and less than -100V. In order to make the crystalline phase more stable, it is more preferably coated with a bias voltage of more than -220V and less than -150V.

[0034] If the B layer is within the range where the diffraction intensity caused by the face-centered cubic lattice structure (fcc structure) represents the maximum intensity, other metal elements may be contained in consideration of the content of Al, Cr, and Si. For example, in order to improve the wear resistance, heat resistance, lubricity, etc. of the hard film, one or more elements selected from the 4a group, 5a group, and 6a group of the periodic table and B, Y, and Cu may be contained. These elements are elements that are usually added to the AlTiN-based or AlCrN-based hard films in order to improve the characteristics of the hard film. If the content ratio is not too large, the durability of the coated cutting tool will not be significantly reduced.

[0035] However, if the B layer contains a large amount of metal elements other than Al, Cr and Si, the above basic characteristics are impaired and the durability of the coated cutting tool may be reduced. Therefore, even if the B layer contains additional elements other than Al, Cr and Si, it is preferred that the total content of the additional elements is set to 10% or less. Furthermore, even if the B layer contains metal elements other than Al, Cr and Si, it is preferred that the total content of the additional elements is set to 5% or less.

[0036] If the film thickness of the B layer is too thin, the excellent durability may not be fully exerted. In addition, if the film thickness is too thick, film peeling may occur. Regarding the thickness of the B layer, for example, an appropriate value may be selected from a range of 0.5 μm or more and 10 μm or less. The thickness of the B layer is more preferably 1 μm or more. In addition, the thickness of the B layer is more preferably 5 μm or less.

[0037] In this embodiment, even if other layers are further coated on the B layer, the effect of this embodiment is also exerted. Therefore, regarding the film structure composed of the A layer and the B layer in this embodiment, in addition to the structure in which the B layer is the outermost surface of the tool, a structure coated with other layers can also be adopted. In this case, it is preferred to coat the C layer composed of a nitride or carbonitride with excellent heat resistance and wear resistance on the B layer as a protective film. The C layer is more preferably a layer composed of a nitride. The C layer is preferably a hard film with excellent heat shock resistance and residual compressive stress. The composition of the C layer can be appropriately selected according to the workpiece or processing conditions. In particular, since the hard film is easily peeled off due to the cycle of heating and cooling in wet processing, it is preferred to set a hard film with high residual compressive stress as a protective film.

[0038] The C layer preferably includes a nitride or carbonitride film having a Ti content of 50% or more and a Si content of 1% or more and 30% or less, in view of the type of film having high residual compressive stress.

[0039] Next, the A layer will be described.

[0040] Since the B layer as the hard film in the present embodiment is a fine structure, it lacks adhesion to the substrate. The inventors have confirmed that by providing an A layer of a face-centered cubic lattice structure (fcc structure) in which W is the largest content among metal elements and Ti is the second largest content, and the total content ratio of W and Ti is 85% or more on the substrate, the adhesion to the B layer as a fine structure is improved, and the durability of the coated cutting tool is improved. That is, the coated cutting tool of the present embodiment improves the adhesion between the B layer as a fine structure and the substrate by forming an A layer of a face-centered cubic lattice structure (fcc structure) mainly composed of W and Ti between the substrate and the B layer.

[0041] By making the A layer formed between the substrate and the B layer a face-centered cubic lattice structure (fcc structure), the B layer with a fine structure located above the A layer can easily maintain the face-centered cubic lattice structure (fcc structure). Moreover, it can be considered that the crystallinity of the B layer located near the A layer is further improved, and the adhesion between the substrate and the B layer is further improved. In addition, since the total content ratio of W and Ti in the metal (including semi-metal) elements of the A layer is more than 85%, the composition and crystal structure are stable. As a result, the unevenness of the composition and crystal structure of the B layer caused by the deviation of the composition and crystal structure of the A layer is reduced. Since the B layer as a whole can easily obtain uniform durability, the risk of deviation in tool performance due to cutting conditions or tool shape can be reduced. It is preferred that the total content ratio of W and Ti in the metal (including semi-metal) elements of the A layer is more than 90%.

[0042] Regarding the A layer, in addition to W and Ti, it may also contain a hard film component and a base material component. However, in order to stabilize the composition and crystal structure of the A layer, it is preferred that the total content ratio of Al and Si in the metal (including semi-metal) elements of the A layer is 10% or less. By reducing the Al and Si contained in the A layer, the composition and crystal structure of the A layer are more likely to become more stable.

[0043] The A layer easily contains Co and Cr contained in the binder phase of the substrate. Even if the A layer contains Co and Cr, the total content of Co and Cr in the metal (including semimetal) elements of the A layer is preferably 10% or less.

[0044] The A layer can be confirmed by cross-sectional observation using a transmission electron microscope, composition analysis, or nanobeam diffraction pattern.

[0045] Regarding the A layer, carbon, which is a non-metallic element, is contained the most, followed by nitrogen. In addition, regarding the A layer, in addition to carbon and nitrogen, oxygen is sometimes contained. When the total content ratio of carbon, nitrogen and oxygen in the A layer is set to 100%, the A layer contains more than 50% of carbon. Furthermore, the A layer preferably contains more than 60% of carbon. In addition, the A layer preferably contains less than 30% of nitrogen. The A layer preferably contains less than 10% of oxygen.

[0046] If the thickness of layer A is too thin, the adhesion to the substrate is reduced. In addition, even if the thickness of layer A is too thick, there is a tendency to reduce the adhesion to the substrate. Therefore, the thickness of layer A is preferably more than 1nm and less than 30nm. The thickness of layer A is preferably more than 2nm and less than 10nm.

[0047] In order to form the A layer of the present embodiment on the substrate, Ti bombardment is performed on the substrate. The film forming device for Ti bombardment preferably has a cathode as a magnetic field structure, and the magnetic field structure is a structure such as a coil magnet is arranged on the periphery of the target and the arc point is enclosed inside the target. By using such a cathode, Ti, which is an element species that easily forms carbides, is bombarded, so that the oxide on the surface of the substrate is removed and cleaning is achieved. In addition, not only this cleaning is performed, but also the bombarded Ti ions diffuse to the WC on the surface of the substrate to easily form a layer containing W and Ti.

[0048] In the present embodiment, by forming the A layer containing W and Ti on the cutting edge as the functional portion, the adhesion between the substrate and the hard film on the cutting edge is improved, thereby achieving an effect of improving the durability of the coated cutting tool.

[0049] In order to make the A layer a face-centered cubic lattice structure (fcc structure), the substrate temperature at the start of Ti bombardment is preferably high. Therefore, the furnace temperature at the start of Ti bombardment is preferably set to 530°C or more.

[0050] In addition, when the absolute value of the bias voltage of the negative pressure applied to the substrate during Ti bombardment is small and the current input to the target is low, it is difficult to form a layer containing W and Ti on the substrate surface. Therefore, the bias voltage of the negative pressure applied to the substrate is preferably not less than -1000 V and not more than -700 V. In addition, the current input to the target is preferably not less than 80 A and not more than 150 A.

[0051] Although Ti bombardment can be carried out while introducing argon, nitrogen, hydrogen, hydrocarbon gases, etc., it is preferred because it is carried out in a vacuum furnace atmosphere of about 0.1 Pa. Therefore, not only is the substrate surface cleaned, but the arc discharge is also stable, making it easy to form the A layer.

[0052] Furthermore, according to the research conducted by the present inventors, it has been confirmed that the thickness of the A layer formed on the tool blade is affected by differences in tool diameter, blade shape, and the like.

[0053] Example

[0054] The coated cutting tools of Examples 1 and 2 and Comparative Examples 1 and 2, when coated under the same conditions, were evaluated for the variation of the intermediate films. Then, the tool performance of the coated cutting tools of Examples 1 and 2 and Comparative Examples 1 and 2 was evaluated.

[0055] <Film forming device>

[0056] When forming the film, an arc ion plating film forming device is used. The device includes a plurality of cathodes (arc evaporation sources), a vacuum container, and a substrate rotating mechanism.

[0057] As cathodes, there are one cathode (hereinafter referred to as "C1") and two cathodes (hereinafter referred to as "C2" and "C3"), wherein the one cathode is a cathode equipped with a coil magnet on the periphery of the target, and the two cathodes are cathodes equipped with permanent magnets on the back and periphery of the target and having a magnetic field with a magnetic flux density in a vertical direction of the target being greater than 14 mT near the center of the target.

[0058] The inside of the vacuum container is evacuated by a vacuum pump, and gas is introduced from a supply port.

[0059] A bias power supply is connected to each substrate placed in the vacuum container, and a negative DC bias voltage is independently applied to each substrate.

[0060] A planetary rotating member, a plate-shaped fixture on the planetary rotating member, and a tubular fixture on the plate-shaped fixture are installed in the substrate rotating mechanism. The planetary rotating member rotates at a speed of three revolutions per minute, and the plate-shaped fixture and the tubular fixture rotate and revolve respectively. A titanium target is set on C1, an AlCrSi alloy target is set on C2, and a TiSi alloy target is set on C3.

[0061] <Base Material>

[0062] As a substrate, a double-edged ball-end mill (manufactured by MOLDINO Co., Ltd.) made of cemented carbide having a composition of WC (bal.)-Co (8 mass%)-Cr (0.5 mass%)-VC (0.3 mass%), a WC average grain size of 0.6 μm, and a hardness of 93.9 HRA was prepared. In addition, WC represents tungsten carbide, Co represents cobalt, Cr represents chromium, and VC represents vanadium carbide.

[0063] <Heating and Vacuum Exhaust Process>

[0064] In the manufacturing processes of Examples 1 and 2, the substrates were respectively fixed to the tubular fixtures in the vacuum chamber, and the pre-film processes were carried out as follows. First, the inside of the vacuum chamber was evacuated to 8×10 -3 Pa or less. Then, through the heater provided in the vacuum chamber, it was heated until the substrate temperature reached 550°C, and vacuum evacuation was carried out. Thus, the substrate temperature was set to 550°C, and the pressure inside the vacuum chamber was set to 8×10 -3 Pa or less.

[0065] <Ar Bombardment Process>

[0066] Then, Ar gas was introduced into the vacuum chamber, and the pressure inside the chamber was set to 0.67 Pa. Then, a current of 20 A was supplied to the filament electrode, a negative bias voltage of -200 V was applied to the substrate, and Ar bombardment was carried out for 4 minutes.

[0067] <Ti Bombardment Process>

[0068] Then, vacuum evacuation was carried out to make the pressure inside the vacuum chamber reach 8×10 -3 Pa or less. Next, Ar gas was introduced, the pressure inside the vacuum chamber was set to 0.1 Pa, a bias voltage was applied to the substrate, an arc current of 150 A was supplied to C1, and Ti bombardment treatment was carried out.

[0069] <Film Deposition Process>

[0070] After Ti bombardment, the power supply to C1 was immediately interrupted. Then, the gas inside the vacuum chamber was replaced with nitrogen, the pressure inside the vacuum chamber was set to 5 Pa, and the set temperature of the substrate was set to 520°C. A power of 150 A was supplied to C2, the negative bias voltage applied to the substrate was set to -200 V, the cathode voltage was set to 25 V, and a nitride of about 2 μm of Al 56 Cr 37 Si 6 (the values are atomic ratios, the same below) was coated. Next, a power of 150 A was supplied to C3, the negative bias voltage applied to the substrate was set to -100 V, the cathode voltage was set to 25 V, and a nitride of about 1 μm of Ti 75 Si 25 was coated. Then, the substrate was cooled to about 250°C or less and taken out from the vacuum chamber. Examples 1 and 2 were coated under the same conditions respectively.

[0071] In the manufacturing processes of Comparative Examples 1 and 2, Ti bombardment was carried out under the following conditions: that is, before Ti bombardment in the manufacturing processes of Examples 1 and 2 above, Ar was not introduced into the furnace, and the pressure inside the vacuum chamber was 8×10 -3Pa or less. In addition, the temperature of the Ti bombardment process was changed from 550° C. to 520° C. The films of Comparative Examples 1 and 2 were respectively coated under the same conditions.

[0072] In order to confirm the film structure, a field emission transmission electron microscope (JEM-2010F manufactured by JEOL Ltd.) was used to observe the blade of a ball-end mill in cross section. The sample was cut and bonded to a pseudo substrate using epoxy resin. Then, cutting, Mo reinforcement ring bonding, grinding, indentation, and Ar ion milling were performed to prepare the sample for measurement. Carbon evaporation was performed before measurement. Observation, composition analysis, and nanobeam diffraction were performed at an accelerating voltage of 200 kV.

[0073] Composition analysis was performed at a beam diameter of 1 nm using a UTW-type Si(Li) semiconductor detector attached to the microscope.

[0074] In the composition analysis, small peaks are determined to be caused by background fluctuations, so only those with an intensity three times or more of the standard deviation of the intensity relative to the background are considered as detection peaks of the element. Regarding nanobeam diffraction, the analysis was performed under the conditions of a camera length of 50 cm and a beam diameter of 2 nm or less.

[0075] Figure 1 This is a transmission electron micrograph of the blade of the tool of Example 1. In the figure, the point 1 is the substrate, the point 2 is the A layer, and the point 3 is the B layer. Figure 2 to Figure 7 The analysis results of the coated cutting tool of Example 1 are shown.

[0076] Table 1 shows the analysis results of the intermediate film (layer A).

[0077] [Table 1]

[0078]

[0079] The A layers of Examples 1 and 2 have a low content of elements other than W and Ti, and have a face-centered cubic lattice structure (fcc structure). On the other hand, the A layers of Comparative Examples 1 and 2 contain a large amount of Al or Si as a component of the hard film, and have a close-packed hexagonal structure (hcp structure). In the A layers of Comparative Examples 1 and 2, it was confirmed that the composition difference within the film was large.

[0080] The coated cutting tools of Examples 1 and 2 were evaluated for cutting performance under the following machining conditions.

[0081] <Cutting conditions>

[0082] Tool: Double-edged hard ball end mill

[0083] Model: EPDBE2010-6, tool radius 0.5mm

[0084] Dry processing

[0085] Cutting method: bottom cutting

[0086] Workpiece: STAVAX (52HRC) (manufactured by Uddeholm)

[0087] Cutting depth: axial 0.04mm, radial 0.04mm

[0088] Cutting speed: 75.4m / min

[0089] Single-edge feed rate: 0.0179mm / edge

[0090] Cutting distance: 15m

[0091] The coated cutting tools of Examples 1 and 2 had a small maximum wear width of the flank less than 20 μm, showing a uniform and stable wear morphology, and confirmed excellent durability. On the other hand, the coated cutting tools of Comparative Examples 1 and 2 had a slightly non-uniform wear state of the hard film compared to the coated cutting tools of Examples 1 and 2. According to the coated cutting tool of the present invention, since the composition deviation of the intermediate film is small, the film quality of the hard film can be improved, and stable tool performance can be expected under various processing conditions.

Claims

1. A coated cutting tool, wherein the surface of the substrate is coated with a hard film, in, The hard film includes an A layer of a face-centered cubic lattice structure and a B layer of a face-centered cubic lattice structure, wherein the A layer is arranged on the surface of the substrate, and contains the most W among metal elements including semi-metals, followed by a large content of Ti, and the total content ratio of W and Ti is 90 atomic % or more, and as a non-metal element, carbon is contained the most, followed by a large content of nitrogen, and the B layer is arranged on the A layer, and is composed of a nitride or carbonitride containing Al, Cr and Si, and the nitride or carbonitride containing Al, Cr and Si has an Al content ratio of 50% or more in atomic %, an Al and Cr content ratio of 85% or more in atomic %, and a Si content ratio of 4% or more and 15% or less in atomic % among metal elements including semi-metals, The A layer does not contain Al and Si.

2. The coated cutting tool according to claim 1, in, A C layer is further provided on the B layer, and the C layer is composed of a nitride or a carbonitride of a metal including a semimetal.

3. The coated cutting tool according to claim 2, in, The C layer is composed of a nitride or a carbonitride in which the content ratio of Ti is 50 atomic % or more and the content ratio of Si is 1 atomic % or more and 30 atomic % or less among metal elements including semimetals.

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