Coated tools for machining difficult-to-cut materials

Abstract

This invention provides a coated tool for cutting difficult-to-machine materials that has excellent wear resistance. [Solution] The coated tool for cutting difficult-to-machine materials comprises a tool for cutting difficult-to-machine materials and a hard coating formed on at least a portion of the outer surface of the tool for cutting difficult-to-machine materials, wherein the hard coating contains a nitride of a metallic element or a nitride of a metallic element and a metalloid element, and the cross-section of the hard coating has a continuous 1000 μm 2 The number of droplets within the range is 50 or less, and when the hard coating is observed by STEM at a magnification of 1.5 million times, the dark-field image of the structure of the cross-section of the hard coating has a striped structure that includes a black layer shown relatively as black and a white layer shown relatively as white.

Description

[Technical Field]

[0001] The present invention relates to a tool for cutting difficult-to-machine materials and a coated tool for cutting difficult-to-machine materials having a hard coating. [Background technology]

[0002] Difficult-to-machine materials such as Inconel, titanium, and Hastelloy are known to be difficult to cut using machining equipment. Specifically, when cutting difficult-to-machine materials with coated cutting tools, the materials contain similar materials to the coated cutting tools, causing the coated cutting tools and the chips from the difficult-to-machine material to weld together. As a result, a hard built-up edge is formed at the cutting edge of the tool. When this built-up edge is formed, the shape of the tool's cutting edge changes, worsening the surface roughness of the workpiece when processed with that tool and affecting the quality of the workpiece. Furthermore, the formed built-up edge is hard but brittle, so if the amount of welding increases, the built-up edge will detach, causing the coating to peel off at the interface between the cutting tool and the coating. Therefore, challenges in cutting tools for difficult-to-machine materials include suppressing the welding between the coated cutting tool and the chips from the difficult-to-machine material, and strengthening the adhesion between the cutting tool and the coating. Furthermore, the hard coating formed on cutting tools used to machine such difficult-to-machine materials requires high resistance to adhesion to the workpiece and high adhesion at the interface between the substrate (cutting tool) and the coating, while the cutting tool itself requires high wear resistance.

[0003] Methods for forming hard coatings on cutting tools include arc ion plating and sputtering. Compared to sputtering, arc ion plating has a higher ionization rate and can form a highly adhesive and hard coating, so it is often used as a coating method for cutting tools. However, due to its principle of operation, arc ion plating releases neutral particle droplets (macroparticles) as a byproduct, resulting in a coating with poor surface smoothness and poor adhesion resistance. On the other hand, sputtering, due to its principle of operation, has a low droplet content in the coating, allowing for the formation of a smooth coating. However, sputtering contains argon in the coating, resulting in a coating with many internal defects. Furthermore, sputtering has a lower ionization rate compared to arc ion plating, which presents many challenges as a coating method for cutting tools used in harsh environments.

[0004] Examples of techniques for forming a coating on tools using the coating formation methods described above include the following. For example, Patent Document 1 describes a method for manufacturing a surface-coated tool that combines arc ion plating and sputtering. Specifically, Patent Document 1 describes a method for manufacturing a surface-coated tool that has excellent wear resistance and adhesion resistance, which includes (1) forming a first layer on a substrate by arc ion plating, (2) performing ion bombardment treatment using metal ions on the first layer, and (3) forming a second layer on the first layer after ion bombardment treatment by sputtering.

[0005] Furthermore, for example, Patent Document 2 describes a method for forming a hard coating by the HiPIMS (High Power Impulse Magnetron Sputtering) method (hereinafter also simply referred to as the "HiPIMS method"), which improves film quality by applying higher power than the conventional sputtering method. Specifically, Patent Document 2 describes a coated cutting tool having a hard coating on the surface of a substrate. More specifically, it describes that the hard coating of the coated tool is a nitride made of Ti and Al, containing 40 to 60 atomic percent Al in the atomic ratio of only metallic elements, and that the hardness and elastic recovery rate measured by the nanoindentation method are within a specific range, and that the number of droplets within a specific range and of a specific size or larger is below a predetermined number. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-172656 [Patent Document 2] Patent No. 6034579 [Overview of the project] [Problems that the invention aims to solve]

[0007] According to the manufacturing method described in Patent Document 1, droplets are not present on the surface or within the layer of the second layer formed on the first layer by sputtering. However, because the second layer is formed by sputtering with a low metal ionization rate, the coating has low wear resistance and wear progresses rapidly. Furthermore, if cutting is continued using the surface-coated tool, the second layer formed by sputtering wears away and reaches the first layer, which is formed by arc ion plating and contains droplets. Upon reaching the first layer, the droplets contained within the first layer surface, causing welding with the workpiece, and tool wear due to welding progresses.

[0008] In addition, the HiPIMS method described in Patent Document 2 can improve the metal ionization rate in the film formation process as compared with the conventional sputtering method. However, even in the HiPIMS method, the metal ionization rate is lower than that in the arc ion plating method, so there is room for improvement in the wear resistance of cutting coated tools.

[0009] In view of these circumstances, especially when used in applications that require seizure resistance and high adhesion at the interface between the base material and the film, such as in the cutting of difficult-to-machine materials, further improvement in the physical properties of the cutting tool is required.

[0010] Therefore, an object of the present invention is to provide a coated tool for cutting difficult-to-machine materials having excellent wear resistance.

Means for Solving the Problems

[0011] As a result of intensive studies to solve the above problems, the present inventors have reached the present invention. That is, the present invention includes the following preferred embodiments.

[0012] The coated tool for cutting difficult-to-machine materials according to the first aspect of the present invention has a tool for cutting difficult-to-machine materials and a hard film formed on at least a part of the outer surface of the tool for cutting difficult-to-machine materials. The hard film contains a nitride of a metal element or a nitride of a metal element and a semi-metal element. The number of droplets within a continuous 1000 μm range in the cross section of the hard film is 50 or less. 2 When the cross section of the hard film in the vicinity of 1 μm in the film thickness depth direction from the outermost surface of the hard film is observed by STEM at a magnification of 1.5 million times, the dark field image of the structure of the cross section of the hard film to be observed includes a black layer shown relatively black and a white layer shown relatively white and has a striped pattern structure.

[0013] The coated tool for cutting difficult-to-machine materials according to the second aspect of the present invention is the coated tool for cutting difficult-to-machine materials according to the first aspect, wherein the hard film is a hard film containing a nitride containing Al and Ti as main components. In the total amount of the metal element and the metalloid element contained in the hard film, the Al content is 80 atomic % or less, the Ti content is less than 75 atomic %, and the total content of Al and Ti is 75 atomic % or more.

[0014] The coated tool for cutting difficult-to-machine materials according to the third aspect of the present invention is the coated tool for cutting difficult-to-machine materials according to the first or second aspect, wherein the hard film is a hard film containing a nitride containing Al and Ti as main components. In the total amount of the metal element and the metalloid element contained in the hard film, the Al content is 80 atomic % or less, the Ti content is less than 75 atomic %, the Si content is greater than 0 atomic %, and the total content of Al, Ti, and Si is 100 atomic %.

[0015] The coated tool for cutting difficult-to-machine materials according to the fourth aspect of the present invention is the coated tool for cutting difficult-to-machine materials according to any one of the first to third aspects, wherein the hard film is a hard film containing a nitride containing Al and Ti as main components. In the total amount of the metal element and the metalloid element contained in the hard film, the Al content is 20 atomic % or more and 70 atomic % or less, the Ti content is 20 atomic % or more and 70 atomic % or less, the Si content is greater than 0 atomic %, and the total content of Al, Ti, and Si is 100 atomic %.

[0016] The coated tool for cutting difficult-to-machine materials according to the fifth aspect of the present invention is the coated tool for cutting difficult-to-machine materials according to the first or second aspect, wherein the hard film is a hard film containing a nitride containing Al and Ti as main components. In the total amount of the metal element and the metalloid element contained in the hard film, the Al content is 80 atomic % or less, the Ti content is less than 75 atomic %, the Nb content is greater than 0 atomic %, and the total content of Al, Ti, and Nb is 100 atomic %.

[0017] A coated tool for cutting difficult-to-machine materials according to the sixth aspect of the present invention is a coated tool for cutting difficult-to-machine materials according to any of the first, second, and fifth aspects, wherein the hard coating is a hard coating containing a nitride mainly composed of Al and Ti. In the total amount of the metal elements and metalloid elements contained in the hard coating, the Al content is 20 atomic% or more and 70 atomic% or less, the Ti content is 20 atomic% or more and 70 atomic% or less, the Nb content is greater than 0 atomic%, and the total content of Al, Ti, and Nb is 100 atomic%.

[0018] A coated tool for cutting difficult-to-machine materials according to a seventh aspect of the present invention comprises a tool for cutting difficult-to-machine materials and a laminated film including a first hard coating formed on at least a portion of the outer surface of the tool for cutting difficult-to-machine materials and a second hard coating formed on the first hard coating, The aforementioned laminated film comprises a nitride of a metallic element or a nitride of a metallic element and a metalloid element. A continuous 1000 μm in the cross-section of the aforementioned laminated film 2 The number of droplets within the range is 50 or less. When the cross-section of the laminated film near 1 μm in the film thickness depth direction from the outermost surface of the laminated film is observed by STEM at a magnification of 1.5 million, the dark-field image of the structure of the observed cross-section of the laminated film has a striped structure that includes a black layer shown relatively as black and a white layer shown relatively as white. The first hard coating is a hard coating containing a nitride mainly composed of Al and Ti, and has a composition in the total amount of the metal elements and metalloid elements contained in the hard coating described in any of the second to sixth embodiments. The second hard coating is a hard coating containing a nitride mainly composed of Ti, In the total amount of the metal element and metalloid element contained in the second hard coating, the Ti content is 70 atomic% or more and 95 atomic% or less, the Si content is 5 atomic% or more and 30 atomic% or less, and the total content of Ti and Si is 100 atomic%. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a coated tool for cutting difficult-to-machine materials that has excellent wear resistance. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 shows a portion of the SEM image used to calculate the number of droplets in the cross-section of the hard coating of Example 1-1. [Figure 2] Figure 2 shows a portion of the SEM images used to calculate the number of droplets in the cross-section of the hard coatings of Comparative Examples 1-2. [Figure 3] Figure 3 shows a dark-field image of the microstructure of the cross-section of the hard coating in Example 2-1, as observed by STEM. [Figure 4] Figure 4 shows a dark-field image of the microstructure of the cross-section of the hard coating in Comparative Example 2-1, as observed by STEM (however, the image shown is a 1.5x magnified version of the acquired dark-field image). [Figure 5] Figure 5 shows the results of line analysis by EDX on dark-field images observed by STEM as shown in Figure 3. [Figure 6] Figure 6 shows the results of line analysis by EDX on dark-field images observed by STEM as shown in Figure 4. [Modes for carrying out the invention]

[0021] As a result of diligent research by the present inventors, it has been found that in a coated tool for cutting difficult-to-machine materials, which comprises a tool for cutting difficult-to-machine materials and a hard coating formed on at least a part of the outer surface of the tool, a coated tool for cutting difficult-to-machine materials with excellent wear resistance can be obtained when the number of droplets within a predetermined range in the cross-section of the hard coating is less than or equal to a predetermined number, and the dark-field image at a predetermined magnification of a predetermined position in the cross-section of the hard coating observed by STEM has a striped structure including a black layer shown relatively as black and a white layer shown relatively as white.

[0022] In this specification, "difficult-to-machine material" means any difficult-to-machine material known to those skilled in the art, such as nickel-based alloys (e.g., Inconel, Hastelloy, etc.), titanium alloys, Waspaloy, magnesium, molybdenum, stainless steel, and high-hardness steels (hardened steel, die steel, high-speed tool steel, pre-hardened steel, etc.).

[0023] The embodiments of the present invention will be described in detail below. However, the scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without impairing the spirit of the invention.

[0024] 1. Configuration of coated tools for machining difficult-to-cut materials First, the configuration of the coated tool for cutting difficult-to-machine materials (hereinafter also simply referred to as the "coated tool") in this embodiment will be described. The coated tool comprises a tool for cutting difficult-to-machine materials and a hard coating formed on at least a portion of the outer surface of the tool for cutting difficult-to-machine materials.

[0025] In this specification, "outer surface of a tool for cutting difficult-to-machine materials" means the surface portion (i.e., the functional part) of the tool that comes into contact with the workpiece during use. In other words, the hard coating only needs to be formed on at least a part of the functional part of such a tool for cutting difficult-to-machine materials. These components will be described in detail below.

[0026] 1-1. Tools for cutting difficult-to-cut materials The types of tools used for cutting difficult-to-machine materials are not particularly limited, as long as they are tools for cutting any difficult-to-machine material known to those skilled in the art. For example, examples of tools for cutting difficult-to-machine materials include end mills, drills, taps, cutting tools, dies, inserts, milling cutters, reamers, and the like.

[0027] The material of the cutting tool for difficult-to-machine materials is not particularly limited, as long as it is any material known to those skilled in the art. For example, materials for cutting tools for difficult-to-machine materials include cemented carbide, cermet, ceramic, and CBN sintered body.

[0028] 1-2. Hard coating The hard coating is formed on at least a portion of the outer surface of the aforementioned tool for cutting difficult-to-machine materials, for example, by a method described later. The hard coating in this embodiment will now be described in detail.

[0029] <Composition of the hard coating> The hard coating contains nitrides of metallic elements or nitrides of metallic elements and metalloid elements. When the composition of the hard coating includes nitrides of metallic elements or nitrides of metallic elements and metalloid elements, a hard coating with excellent hardness can be obtained.

[0030] (Al (aluminum) and Ti (titanium)) In this embodiment, the hard coating preferably contains a nitride mainly composed of Al and Ti, and more preferably consists of a nitride mainly composed of Al and Ti. By having the hard coating mainly composed of Al and Ti, a hard coating good for machining difficult-to-cut materials can be reliably obtained.

[0031] In this specification, "the hard coating contains Al and Ti as its main components" means that the combined content of Al and Ti in the total amount of metallic and metalloid elements contained in the hard coating exceeds 50 atomic percent. Furthermore, "the hard coating contains Ti as its main component," as described later, means that the content of Ti in the total amount of metallic and metalloid elements contained in the hard coating exceeds 50 atomic percent.

[0032] When the hard coating contains a nitride mainly composed of Al and Ti, the Al content in the total amount of metallic and metalloid elements contained in the hard coating is preferably 80 atomic percent or less. When the Al content is 80 atomic percent or less, a better hard coating can be reliably obtained for machining applications of difficult-to-machine materials. The Al content is more preferably 70 atomic percent or less, even more preferably 68 atomic percent or less, and particularly preferably less than or equal to a value selected from the group consisting of 65 atomic percent, 63 atomic percent, 60 atomic percent, and 58 atomic percent.

[0033] In this specification, the composition of the total amount of metallic and metalloid elements contained in a hard film, such as Al content and Ti content, refers to the composition (or average composition) of the metallic and metalloid elements contained in the hard film. The composition (or average composition) of the metallic and metalloid elements contained in the hard film can be measured, for example, by energy-dispersive X-ray spectroscopy (EDS analysis) using a scanning electron microscope with an energy-dispersive X-ray microanalyzer, or by using an electron probe microanalyzer, as described in later examples. When the hard film consists of a laminated film comprising a first hard film and a second hard film as described later, the composition of metallic and metalloid elements contained in each layer of the film shall be a value calculated as a converted value of the composition of each layer of the film by a method described in detail in later examples.

[0034] When the hard coating contains a nitride mainly composed of Al and Ti, it is preferable that the Al content in the total amount of metallic and metalloid elements contained in the hard coating is 20 atomic percent or more. An Al content of 20 atomic percent or more can improve the heat resistance of the hard coating. The Al content is more preferably 30 atomic percent or more, even more preferably 35 atomic percent or more, and particularly preferably a value selected from the group consisting of 40 atomic percent, 43 atomic percent, 45 atomic percent, 47 atomic percent, 49 atomic percent, and 50 atomic percent.

[0035] When the hard coating contains a nitride mainly composed of Al and Ti, the Ti content in the total amount of metallic and metalloid elements contained in the hard coating is preferably less than 75 atomic percent. A Ti content of less than 75 atomic percent ensures sufficient Al content in the hard coating, thereby improving the heat resistance of the hard coating. The Ti content is more preferably 60 atomic percent or less, even more preferably 50 atomic percent or less, and particularly preferably less than or equal to a value selected from the group consisting of 45 atomic percent, 42 atomic percent, and 40 atomic percent.

[0036] When the hard coating contains a nitride mainly composed of Al and Ti, the Ti content in the total amount of metallic and metalloid elements contained in the hard coating is preferably 10 atomic percent or more. By setting the Ti content to 10 atomic percent or more, it is possible to prevent the Al content in the hard coating from becoming excessively high, which would result in a hard coating unsuitable for machining difficult-to-machine materials. Furthermore, a Ti content of 10 atomic percent or more ensures the strength and toughness of the hard coating. The Ti content is more preferably 15 atomic percent or more, even more preferably 18 atomic percent or more, and even more preferably a value selected from the group consisting of 20 atomic percent, 22 atomic percent, 25 atomic percent, 30 atomic percent, and 33 atomic percent.

[0037] When the hard coating contains a nitride mainly composed of Al and Ti, the total amount of Al and Ti in the hard coating is preferably 75 atomic percent or more. A total Al and Ti content of 75 atomic percent or more provides excellent wear resistance for machining difficult-to-cut materials, and also offers heat resistance, strength, and toughness. The total Al and Ti content is more preferably 80 atomic percent or more, even more preferably 83 atomic percent or more, and particularly preferably above a value selected from the group consisting of 85 atomic percent, 88 atomic percent, 90 atomic percent, and 91 atomic percent. The upper limit of the total Al and Ti content is not particularly limited, and may be 100 atomic percent or less.

[0038] Specifically, as an example of such a hard coating, it is preferable that the total amount of metallic and metalloid elements contained in the hard coating is such that the Al content is 80 atomic percent or less, the Ti content is less than 75 atomic percent, and the combined content of Al and Ti is 75 atomic percent or more. With this hard coating, it is possible to more reliably obtain coated tools with excellent wear resistance for machining difficult-to-cut materials.

[0039] (Metallic elements and metalloid elements other than Al (aluminum) and Ti (titanium)) If the hard coating contains a nitride mainly composed of Al and Ti, the hard coating may also contain one or more elements from among metallic elements and metalloid elements other than Al and Ti, to the extent that it does not significantly reduce the wear resistance of the coated tool.

[0040] For example, the hard coating may contain one or more metallic elements selected from the group consisting of elements from groups 4a, 5a, and 6a of the periodic table (groups 4, 5, and 6 respectively in the long-period periodic table), as well as Y (yttrium), Yb (ytterbium), and Cu (copper), for the purpose of improving properties such as wear resistance and heat resistance (hereinafter also referred to as "coating properties"). In particular, from the viewpoint of being able to improve wear resistance, it is preferable that the hard coating contains Nb (niobium). Alternatively, for example, the hard coating may contain one or more elements from the metalloid elements Si (silicon) and B (boron). In particular, from the viewpoint of being able to improve the heat resistance of the hard coating, it is preferable that the hard coating contains Si.

[0041] When a hard coating contains a nitride mainly composed of Al and Ti, if the content of one or more elements other than Al and Ti, which are metal elements and metalloid elements, becomes too high, the hardness of the hard coating may decrease. Therefore, when a hard coating contains a nitride mainly composed of Al and Ti, and also contains one or more elements other than Al and Ti, the total content of one or more of these metal elements and metalloid elements other than Al and Ti is preferably 25 atomic% or less, more preferably 20 atomic% or less, even more preferably 18 atomic% or less, and particularly preferably less than or equal to a value selected from the group consisting of 15 atomic%, 13 atomic%, 10 atomic%, and 9 atomic%.

[0042] Furthermore, from the viewpoint of exhibiting the effects of one or more elements from among the metal elements and metalloid elements other than Al and Ti, if the hard coating contains a nitride mainly composed of Al and Ti, and also contains one or more elements from among the metal elements and metalloid elements other than Al and Ti, the total content of one or more elements from among the metal elements and metalloid elements other than Al and Ti is preferably greater than 0 atomic%, more preferably 3 atomic% or more, even more preferably 5 atomic% or more, and particularly preferably 7 atomic% or 8 atomic% or more, as a lower limit of the total amount of metal elements and metalloid elements contained in the hard coating.

[0043] Furthermore, the preferred upper or lower limits for the total content of one or more elements other than Al and Ti, and metalloid elements, as mentioned above, can be the preferred upper or lower limits for the Si content and / or Nb content.

[0044] Specifically, as an example of such a hard coating, it is preferable that the total amount of metallic and metalloid elements contained in the hard coating is such that the Al content is 70 atomic% or less, the Ti content is less than 75 atomic%, the Si content is greater than 0 atomic%, and the combined content of Al, Ti, and Si is 100 atomic%. With this hard coating, it is possible to more reliably obtain coated tools with excellent wear resistance for machining difficult-to-cut materials.

[0045] Alternatively, as an example of such a hard coating, it is more preferable that the total amount of metallic and metalloid elements contained in the hard coating is such that the Al content is 20 to 70 atomic%, the Ti content is 20 to 70 atomic%, the Si content is greater than 0 atomic%, and the total content of Al, Ti, and Si is 100 atomic%. With this hard coating, it is possible to more reliably obtain coated tools with excellent wear resistance for machining difficult-to-cut materials.

[0046] Furthermore, as another example of such a hard coating, it is preferable that the total amount of metallic and metalloid elements contained in the hard coating is such that the Al content is 70 atomic% or less, the Ti content is less than 75 atomic%, the Nb content is greater than 0 atomic%, and the total content of Al, Ti, and Nb is 100 atomic%. With this hard coating, it is ultimately possible to more reliably obtain coated tools with excellent wear resistance for machining difficult-to-cut materials.

[0047] Alternatively, a more specific example of such a hard coating is that, in terms of the total amount of metallic and metalloid elements contained in the hard coating, it is preferable that the Al content is 20 to 70 atomic%, the Ti content is 20 to 70 atomic%, the Nb content is greater than 0 atomic%, and the total content of Al, Ti, and Nb is 100 atomic%. With this hard coating, it is ultimately possible to more reliably obtain coated tools with excellent wear resistance for machining difficult-to-cut materials.

[0048] (Inevitable impurities) The composition of the hard coating may include, in addition to one or more metallic and metalloid elements contained in the hard coating as described above, unavoidable impurities to the extent that they do not impair the excellent wear resistance effect of the coated tool of this embodiment. Specifically, even if the total content of one or more specific metallic and metalloid elements is specified in this specification as 100 atomic percent, the composition of the hard coating may include unavoidable impurities other than those specific one or more elements.

[0049] <Number of droplets in the cross-section of the hard coating> In this embodiment, a continuous 1000 μm in the cross-section of the hard coating 2 The number of droplets within the specified range is 50 or less (hereinafter also referred to as "the condition for the number of droplets in this embodiment"). When the number of droplets within the specified range is 50 or less, the hard coating can have excellent surface smoothness and high adhesion resistance to the workpiece.

[0050] The number of droplets within the range is preferably 45 or less, more preferably 40 or less, still more preferably 35 or less, and particularly preferably a value selected from the group consisting of 33, 31, 29, and 27 or less.

[0051] In this specification, a "droplet" is a metal particle present in the cross-section of the hard film. Specifically, a "droplet" is a virtual rectangle or substantially square circumscribing the metal particle present in the cross-section of the hard film, and the length L a (μm) or the length of one side of the substantially square L a (μm) means a particle satisfying the condition: 0.1 (μm) ≤ L a .

[0052] Furthermore, in this specification, the "number of droplets within a continuous 1000 μm 2 range in the cross-section of the hard film" may be the number of droplets within a continuous 1000 μm 2 range at a specific location in the cross-section of the hard film. Specifically, the "number of droplets within a continuous 1000 μm 2 range in the cross-section of the hard film" is, as will be described in detail in the later examples, the number of droplets within a continuous 1000 μm 2 range in the cross-section of the hard film near the cutting edge tip on the rake face side of the outer peripheral edge of the coated tool.

[0053] Also, in this specification, the "continuous 1000 μm 2 range in the cross-section of the hard film" means, when the thickness (film thickness) of the hard film is about 2 μm, the range in the cross-section of the hard film with a thickness of 2.0 μm and a length of 500 μm parallel to the direction orthogonal to the film thickness depth direction (i.e., a range of 2.0 μm × 500 μm = 1000 μm 2 ).

[0054] Alternatively, in this specification, the "continuous 1000 μm 2The "range" refers to a range where the thickness of the hard coating is less than 2 μm, specifically a thickness of x μm (less than 2.0 μm) and the range is 1000 μm. 2 The range in the cross-section of the hard coating with a length of y μm parallel to the direction perpendicular to the film thickness depth direction, which is set based on the thickness x μm, is such that (i.e., x μm (less than 2.0 μm) × y μm = 1000 μm) 2 It means (the range).

[0055] Furthermore, in this specification, "continuous 1000 μm in the cross-section of the hard coating" 2 The "range" refers to the range in the cross-section of the hard coating at an arbitrarily selected position, where the thickness of the hard coating exceeds 2 μm, and the length in the film thickness direction is 2.0 μm and the length parallel to the direction perpendicular to the film thickness direction is 500 μm (i.e., 2.0 μm × 500 μm = 1000 μm). 2 It means (the range).

[0056] The number of droplets present in a continuous range within a cross-section of such a hard coating can be observed and measured, for example, using a scanning electron microscope (SEM), as will be described in detail in later examples.

[0057] <Structural structure of a cross-section of a hard coating> In this embodiment, when a cross-section of the hard coating near 1 μm in the film thickness depth direction from the outermost surface of the hard coating is observed at a magnification of 1.5 million using a scanning transmission electron microscope (STEM), the dark-field image of the structure of the observed cross-section of the hard coating has a striped structure that includes a black layer shown relatively as black and a white layer shown relatively as white (hereinafter also referred to as "conditions for the cross-section of the hard coating in this embodiment"). In this specification, "cross-section near 1 μm in the film thickness depth direction" specifically means a cross-section parallel to the plane along the film thickness depth direction near 1 μm from the outermost surface of the hard coating. Alternatively, if the thickness of the hard coating is less than 1 μm, it may be a cross-section parallel to the plane along the film thickness depth direction near about half the film thickness from the outermost surface of the hard coating.

[0058] Specifically, in the striped structure observed by STEM, the black layer represents a region where the metallic content is relatively decreased and the nitrogen content is relatively increased. Similarly, in the striped structure, the white layer represents a region where the metallic content is relatively increased and the nitrogen content is relatively decreased. These variations in the nitrogen and metallic content within the film can be confirmed by line analysis using an energy-dispersive X-ray spectrometer (EDX), as will be described in detail in later examples.

[0059] A hard coating with such a striped structure exhibits excellent adhesion and high bonding properties at the interface with the substrate. As a result, a coated tool with excellent wear resistance can be obtained for machining difficult-to-cut materials.

[0060] Furthermore, hard coatings having such a striped pattern can be obtained by forming them using the arc ion plating method. The principle by which such hard coatings having a striped pattern can be obtained using the arc ion plating method is as follows.

[0061] In arc ion plating, the ionization rate of metal components is high during the film formation process. Therefore, during the film formation process, metal ions circulate within the apparatus and form a film not only when the substrate passes in front of the arc evaporation source (a cathode equipped with a target composed of metal components), but also after the substrate has passed in front of the arc evaporation source. In this case, the metal ion content in the formed hard film is higher when the substrate passes in front of the arc evaporation source (a cathode equipped with a target composed of metal components), and decreases as the substrate moves away from the arc evaporation source. On the other hand, nitrogen plasma is present in a constant proportion regardless of the position of the worktable (i.e., the position of the substrate). Therefore, when a film is formed on a substrate at a position far from the arc evaporation source (a cathode equipped with a target composed of metal components), the relative proportion of nitrogen in the formed film increases, and the proportion of metal components decreases.

[0062] The microstructure of such hard coatings as observed by STEM will be described in more detail in later examples.

[0063] <Thickness of the hard coating> The hard coating is not particularly limited, but is preferably 1 μm or thicker. A hard coating thickness of 1 μm or more can further improve the wear resistance of the hard coating to stress, resulting in a coated tool with superior wear resistance.

[0064] The upper limit of the hard coating thickness is not particularly limited, but for example, from the viewpoint of cost and productivity, the hard coating thickness is preferably 10 μm or less, may be 8 μm or less, or 6 μm or less. In this specification, "hard coating thickness" means the film thickness at the point where the distance between the substrate surface and the hard coating surface is greatest in the cross-section of the hard coating thickness, if the substrate surface and / or the surface of the hard coating are not smooth.

[0065] The coated tool for machining difficult-to-cut materials in this embodiment has excellent wear resistance and can therefore be suitably applied even in high-load applications such as machining difficult-to-cut materials.

[0066] 2. Other configurations of coated tools for machining difficult-to-cut materials In this embodiment, the coated tool may, if necessary, have an underlayer between it and the hard coating to further improve adhesion between the tool for cutting difficult-to-machine materials and the hard coating, as long as the wear resistance effect of the coated tool of this embodiment is not impaired. The underlayer can be formed from, for example, one or more layers of metal, nitride, carbonitride, and carbide.

[0067] Furthermore, as long as the conditions for the number of droplets and the cross-section of the hard coating in this embodiment are met and the wear resistance effect of the coated tool in this embodiment is not impaired, an upper layer having a different composition and / or composition ratio from the hard coating may be formed on the hard coating formed on the outer surface of the tool for cutting difficult-to-machine materials.

[0068] Furthermore, a hard coating (hereinafter referred to as the "second hard coating") may be formed on the outer surface of a tool for cutting difficult-to-machine materials (hereinafter referred to as the "first hard coating"), having a different composition and / or composition ratio from the first hard coating, but satisfying the conditions for the number of droplets and the cross-section of the hard coating in this embodiment. Additionally, yet another hard coating (hereinafter referred to as the "third hard coating") may be formed on top of these laminated coatings, satisfying the conditions for the number of droplets and the cross-section of the hard coating in this embodiment.

[0069] Alternatively, the first hard coating and the second hard coating (or the first hard coating, the second hard coating, and the third hard coating) may be laminated together. Furthermore, the first hard coating and the second hard coating (or the first hard coating, the second hard coating, and the third hard coating) may be laminated alternately in two or more layers. Alternatively, as long as the wear resistance of the coated tool of this embodiment is not impaired, one or more layers of hard coatings containing nitrides, carbonitrides, oxides, or oxynitrides of metallic elements, metals, nitrides, carbonitrides, and carbides may be sandwiched between the laminated structures that satisfy the conditions for the number of droplets and the cross-sectional surface of the hard coating in this embodiment.

[0070] In detail, an example of a hard coating having multiple layers of such hard coatings is a laminated film comprising a first hard coating and a second hard coating formed on the first hard coating, wherein the laminated film comprises a nitride of a metallic element or a nitride of a metallic element and a metalloid element. In this configuration, the laminated film itself has a continuous 1000 μm cross-section of the laminated film. 2The aforementioned condition for the number of droplets in this embodiment is met, which states that "the number of droplets within the range is 50 or less." Furthermore, in this configuration, the laminated film itself satisfies the aforementioned condition for the cross-section of the hard coating in this embodiment, which states that "when a cross-section near 1 μm in the film thickness depth direction from the outermost surface of the laminated film is observed by STEM at a magnification of 1.5 million, the dark-field image of the structure of the observed cross-section of the laminated film has a striped structure that includes a black layer shown relatively as black and a white layer shown relatively as white." Below, an example of a configuration in which a laminated film including such a first hard coating and a second hard coating is formed will be described in detail.

[0071] In such a configuration, the first hard coating is preferably a hard coating containing a nitride mainly composed of Al and Ti (more preferably a hard coating consisting of a nitride mainly composed of Al and Ti). Specifically, the composition of the first hard coating is preferably the composition of the hard coating described in 1-2 above (composition in the total amount of metallic and metalloid elements).

[0072] In other words, as an example of the first hard coating in the said configuration, it is preferable that the total amount of metallic and metalloid elements contained in the first hard coating is such that the Al content is 80 atomic% or less, the Ti content is less than 75 atomic%, and the combined content of Al and Ti is 75 atomic% or more.

[0073] Alternatively, as another example of the first hard coating in the said configuration, it is preferable that the total amount of metallic and metalloid elements contained in the first hard coating is such that the Al content is 70 atomic% or less, the Ti content is less than 75 atomic%, the Si content is greater than 0 atomic%, and the total content of Al, Ti, and Si is 100 atomic%. Or, as yet another example of the first hard coating in the said embodiment, it is more preferable that the total amount of metallic and metalloid elements contained in the first hard coating is such that the Al content is 20 atomic% or more and 70 atomic%, the Ti content is 20 atomic% or more and 70 atomic%, the Si content is greater than 0 atomic%, and the total content of Al, Ti, and Si is 100 atomic%.

[0074] Alternatively, as yet another example of the first hard coating in the said configuration, it is preferable that the total amount of metallic and metalloid elements contained in the first hard coating is such that the Al content is 70 atomic% or less, the Ti content is less than 75 atomic%, the Nb content is greater than 0 atomic%, and the total content of Al, Ti, and Nb is 100 atomic%. Or, as yet another example of the first hard coating in the said configuration, it is more preferable that the total amount of metallic and metalloid elements contained in the first hard coating is such that the Al content is 20 atomic% or more and 70 atomic%, the Ti content is 20 atomic% or more and 70 atomic%, the Nb content is greater than 0 atomic%, and the total content of Al, Ti, and Nb is 100 atomic%.

[0075] Furthermore, in such a configuration, the second hard coating is preferably a hard coating containing a nitride mainly composed of Ti (more preferably a hard coating consisting of a nitride mainly composed of Ti).

[0076] In this configuration, the Ti content in the total amount of metallic and metalloid elements contained in the second hard coating is preferably 60 atomic% or more, more preferably 70 atomic% or more, and even more preferably 75 atomic% or more. Furthermore, in this embodiment, the Ti content in the total amount of metallic and metalloid elements contained in the second hard coating is preferably 95 atomic% or less, more preferably 90 atomic% or less, even more preferably 85 atomic% or less, and particularly preferably 80 atomic% or less.

[0077] Furthermore, in this configuration, the Si content in the total amount of metallic and metalloid elements contained in the second hard coating is preferably 5 atomic% or more, more preferably 10 atomic% or more, even more preferably 15 atomic% or more, and particularly preferably 20 atomic% or more. Furthermore, in this embodiment, the Si content in the total amount of metallic and metalloid elements contained in the second hard coating is preferably 30 atomic% or less, more preferably 25 atomic% or less, and even more preferably 20 atomic% or less.

[0078] As a specific example of such a second hard coating, it is preferable that the second hard coating contains, in terms of the total amount of metallic and metalloid elements, a Ti content of 70 atomic% to 95 atomic%, a Si content of 5 atomic% to 30 atomic%, and a total Ti and Si content of 100 atomic%.

[0079] When one or more layers of such underlayer, upper layer, and / or different hard coatings are formed, or when a laminated film with the above configuration is formed, it is preferable, although not particularly limited, that the total thickness of the laminate be 10 μm or less.

[0080] 3. Method for manufacturing coated tools for machining difficult-to-machine materials The coated tool for cutting difficult-to-machine materials in this embodiment can be manufactured by coating (forming) a hard coating on at least a portion of the outer surface of the tool for cutting difficult-to-machine materials. To satisfy the cross-sectional conditions of the hard coating in this embodiment, arc ion plating is applied to coat the hard coating. Furthermore, in the arc ion plating method, it is preferable to use a film deposition apparatus equipped with a cathode that has permanent magnets arranged on the back and outer circumference of the target.

[0081] A film deposition apparatus used in arc ion plating includes, for example, an arc evaporation source equipped with a target made of the hard film material, an anode to which electrons enter during arc discharge, an arc power supply for supplying arc current to the target, a furnace (vacuum vessel) for housing the cutting tool, which is the substrate, a substrate rotation mechanism for rotating the substrate inside the furnace, a bias power supply for applying a bias voltage to the substrate, a heater for heating the inside of the furnace and the substrate, a vacuum pump for creating a vacuum inside the furnace, and a gas inlet for introducing both or either an inert gas (Ar (argon), Kr (krypton), etc.) and a reaction gas into the furnace. Furthermore, it is preferable that the film deposition apparatus is equipped with a filter mechanism that can reduce droplets, which are clumps of the film-forming material, by using a magnetic field.

[0082] The following describes in detail a method for forming thin films using arc ion plating with a cutting tool for difficult-to-machine materials as the substrate.

[0083] First, the furnace is evacuated. At that time, the vacuum pressure is 10 × 10 -3 It is preferable to keep the pressure below Pa. By evacuating the furnace, oxidation of the substrate can be prevented by starting the heating of the substrate while there is a large amount of residual gas in the furnace.

[0084] After vacuuming, the substrate is heated. The heating temperature is preferably 420°C to 550°C. Heating the substrate within this temperature range prevents a decrease in film adhesion due to insufficient diffusion at the substrate-film interface caused by excessively low temperatures, and also prevents the substrate material from softening due to heat.

[0085] Next, the substrate is etched. The etching process can be performed by introducing an inert gas into the furnace, plasma-generating the inert gas, and causing the inert gas ions to collide with the substrate to which a negative bias voltage is applied (for example, if the inert gas is Ar gas, this is called argon bombardment). Alternatively, the mounted arc vaporizer can be discharged together with the inert gas as desired, ionizing the metal target attached to the arc vaporizer and the inert gas, and causing these to collide with the substrate to perform the etching process. If the arc vaporizer is discharged without using an inert gas, etching can be performed using only metal ions (metal bombardment).

[0086] In the manufacturing method of this embodiment, the etching process may be carried out by any of the following methods: etching with argon bombardment alone, etching with metal bombardment alone, or etching using a combination of argon bombardment and metal bombardment. Specifically, unlike argon bombardment, metal bombardment may generate droplets in principle, but from the viewpoint of obtaining high adhesion, it is preferable to perform the etching process with metal bombardment. Even when performing the etching process with metal bombardment, it is preferable to reduce droplets by methods such as using a film deposition apparatus equipped with the filter mechanism described above.

[0087] When performing etching by plasma-generating an inert gas, the furnace pressure is preferably between 0.1 Pa and 3 Pa. If the inert gas pressure is too low, the amount of inert gas ions generated may be insufficient, resulting in an inadequate etching effect. On the other hand, if the inert gas pressure is too high, the ionized inert gas may collide with the unionized inert gas, resulting in an inadequate etching effect.

[0088] When etching a metal target by ionizing it through the discharge of an arc evaporation source, the arc current is preferably 50A to 200A. If the arc current is too low, it becomes difficult to generate an arc discharge, and sufficient etching may not be possible. On the other hand, if the arc current is too high, it is possible to generate many ions and improve the etching effect, but other problems arise. Specifically, if the arc current is too high, many molten droplets (macroparticles) are generated from a part of the target, and these macroparticles adhere to the substrate surface, which can roughen the substrate surface. Such roughness of the substrate surface can ultimately lead to a decrease in the adhesion resistance to the workpiece. Therefore, in order to suppress the generation of macroparticles, it is preferable not to use an excessively high arc current.

[0089] Furthermore, in order to reduce the adhesion of generated macroparticles to the substrate, it is preferable that the arc evaporation source provided in the film deposition apparatus be equipped with a magnetic field filter mechanism.

[0090] During etching, a negative bias voltage is applied to the substrate. From the viewpoint of obtaining a sufficient etching effect, the applied voltage is preferably between -100V and -1000V. If the bias voltage applied to the substrate is too low, a sufficient etching effect may not be obtained. On the other hand, if the voltage is too high, abnormal discharge may occur on the substrate surface, potentially damaging the substrate.

[0091] After etching, a hard film is deposited on the substrate. During film deposition, a reaction gas is introduced into the furnace. To stabilize the discharge, an inert gas such as Ar gas may be mixed with the reaction gas; however, inert gases such as Ar gas may remain in the film without reacting with the evaporated metal material. Therefore, it is preferable to avoid mixing inert gases such as Ar gas as much as possible.

[0092] Examples of reaction gases include nitrogen gas, oxygen gas, and hydrocarbon gases such as methane. These reaction gases should be selected appropriately according to the application.

[0093] To form a dense, high-strength hard film containing nitrides, the pressure inside the furnace during film formation is preferably 1 Pa to 6 Pa. If the pressure is too low, the reaction between the evaporated metal and the reaction gas may be insufficient, and the desired nitride may not be formed. On the other hand, if the pressure is too high, the evaporated metal ions may collide with the reaction gas, causing these ions to reach the substrate in an energy-lost state. As a result, these ions may not be able to diffuse sufficiently on the substrate surface, preventing the formation of a dense film and potentially leading to a decrease in film strength.

[0094] The negative bias voltage applied to the substrate is preferably between -15V and 300V. If the bias voltage is too low, soft hexagonal AlN (aluminum nitride) may precipitate in the film, potentially leading to a decrease in the hardness of the hard film. On the other hand, if the bias voltage is too high, the energy of metal ions and / or gas ions that are pulled by the negative voltage and collide with the substrate may increase, potentially increasing the effect of striking the coating deposited on the substrate (ion peening effect). As a result, the distortion of the film may increase, leading to increased stress. If the stress increases too much, it can cause the film to peel off.

[0095] The arc current supplied to the target is preferably between 50A and 200A.

[0096] As mentioned above, by forming a hard coating using an arc ion plating method with a film deposition apparatus equipped with such permanent magnets and filter mechanisms, the number of droplets can be reduced, and a hard coating with excellent surface smoothness can be easily obtained.

[0097] In other words, by applying this arc ion plating method to form a hard coating on a tool for cutting difficult-to-machine materials, it is possible to more easily manufacture coated tools that satisfy the requirements for the number of droplets and the cross-sectional shape of the hard coating in this embodiment. Furthermore, as mentioned above, the coated tools manufactured in this way have excellent wear resistance and can therefore be suitably applied to high-load and unique applications such as cutting difficult-to-machine materials. [Examples]

[0098] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0099] 1. Formation of a hard coating on tools for cutting difficult-to-machine materials. In Examples 1-1 to 1-13 and Comparative Examples 1-1 to 1-6, coated tools with a hard coating were actually manufactured for cutting difficult-to-machine materials. The composition of metallic and metalloid elements contained in the hard coating was measured, the number of droplets was calculated, and the cutting performance of the coated tools was evaluated.

[0100] Details regarding the cutting tools used for machining difficult-to-cut materials, the method for measuring the composition of metallic and metalloid elements contained in the hard coating, the method for calculating the number of droplets, and the method for evaluating the cutting performance of the coated tools are as follows.

[0101] <Tools for cutting difficult-to-cut materials> For machining difficult-to-cut materials, a 6mm diameter, four-flute carbide square end mill was used.

[0102] <Measurement of the composition of metallic and metalloid elements contained in the hard coating> The composition of metallic and metalloid elements contained in the hard coatings in each example and comparative example was measured by EDS analysis using a scanning electron microscope with an energy-dispersive X-ray microanalyzer (JEOL Ltd., "JSM-6010PLUS / LA"). The EDS conditions were set to an acceleration voltage of 15kV, a live time of 100s, and a process time of 4.

[0103] <Method for calculating the number of droplets in the cross-section of a hard coating> Continuous 1000 μm in the cross-section of the hard coating 2The number of droplets within the specified range was determined by the following method. First, the tip of the cutting edge on the rake face side of the outer cutting edge of the coated tool on which the hard coating was formed in each example and comparative example was observed using a field emission scanning electron microscope (FE-SEM). For observation, either the "JSM-7200F" manufactured by JEOL Ltd. (Examples 1-1, Examples 4 to 1-13 and Comparative Examples 1-3 to 1 to 6, and Examples 3-1 to 3-8 described later) or the "JSM-7800F" manufactured by JEOL Ltd. (Examples 1-2 to 1-3 and Comparative Examples 1-1 to 1-2) was used. Next, on the rake face of the outer cutting edge on which the hard coating was formed, a region including a length of 500 μm in the direction perpendicular to the film thickness depth direction from the tip of the cutting edge was selected, and cross-sectional processing was performed on this region. Specifically, first, using a wire electrical discharge machine ("AQ325L," manufactured by Sodick Co., Ltd.), samples were cut out from the rake face side of the coated tools for each example and comparative example, in an area slightly wider than the area to be machined. Next, the cut samples were polished using a polishing machine ("TegraPol-31" manufactured by Struers (Examples 1-1 to 1-3, 1-6, 1-8, 1-10 to 1-13, Comparative Examples 1-1 to 1-2 and 1-5 to 1-6, as well as Examples 3-2 to 3-4 and 3-6 to 3-8 described later), or "MODEL900" manufactured by South Bay Technology (Examples 1-4 to 1-5, 1-7, 1-9 and Comparative Examples 1-3 to 1-4, as well as Examples 3-1 and 3-5 described later)) to remove the altered layer and reduce surface irregularities. Subsequently, a cross-section polisher ("SM-09010", manufactured by NEC Corporation) was used to perform a finishing process so that the length in the direction perpendicular to the film thickness depth direction was 500 μm.

[0104] Subsequently, the cross-section of the hard coating that had undergone the finishing process was observed again using FE-SEM at a magnification of 20,000x. Specifically, while moving the stage in a direction perpendicular to the film thickness direction, a continuous 1000 μm section of the hard coating cross-section was observed, with a thickness of 2.0 μm in the film thickness direction and a length of 500 μm in the direction perpendicular to the film thickness direction. 2 The number of droplets within the specified range was calculated by visually measuring them. Whether or not a droplet is in the cross-section of the hard coating was determined by the following method: First, the white, roughly circular portions within the cross-sectional area of ​​the hard coating used to calculate the droplets were examined. For each of these white, roughly circular portions, the length of the longer side L of the rectangle or roughly square circumscribing that portion was considered. a (μm) or the length of one side of the approximate square L a (μm) was determined. Here, the rectangle or approximate square was set so that the longer side or one side of the approximate square was parallel to the main surface of the cutting tool for difficult-to-machine materials, which was the base material mentioned above. Finally, the L was determined. a If the following conditions are met, the approximately circular portion shall be considered a droplet, and a continuous 1000 μm section with a thickness of 2.0 μm and a length of 500 μm shall be formed in the cross-section of the hard coating. 2 The number of droplets within the specified range was calculated. Condition: 0.1(μm)≦L a

[0105] <Method for evaluating the cutting performance of coated tools> The cutting performance of the coated tools was evaluated by the following method. Using the coated tools manufactured in each example and comparative example, cutting was performed under the following cutting conditions. At 1m intervals of cutting length, the maximum wear width (μm) of the flank surface of each of the four blades of the coated tool was measured using a digital microscope ("VHX-6000", manufactured by Keyence Corporation), and the average value was calculated. After cutting every 1m, the cutting length (m) was measured when the average value of the maximum wear width of the flank surface exceeded 100μm.

[0106] It should be noted that the cutting length (m) measured in this manner varies depending on the manufacturing lot of the cutting tool and / or workpiece. Therefore, in evaluating the cutting performance of the coated tool in this embodiment, the cutting performance was evaluated based on a benchmark ratio (BM ratio) using the cutting length (m) at which the maximum flank wear width of the coated tool in Comparative Example 1-2 exceeded 100 μm, measured using the same manufacturing lot of cutting tool and workpiece. Specifically, the BM ratio was calculated by dividing the cutting length (m) at which the maximum flank wear width exceeded 100 μm, measured using the coated tool of each embodiment and each comparative example, by the cutting length (m) at which the maximum flank wear width exceeded 100 μm, measured using the same manufacturing lot of cutting tool and workpiece for the coated tool in Comparative Example 1-2. If the calculated BM ratio is greater than 1.0, the coated tool is considered to have excellent wear resistance for machining difficult-to-cut materials, and is evaluated as "A" in Tables 1 and 2 below. If the calculated BM ratio is 1.0 or less, the coated tool is considered to have poor wear resistance for machining difficult-to-cut materials and is rated "B" in Tables 1 and 2 below. (Cutting conditions) Processing method: side cutting Rotation speed: 2100 min⁻¹ -1 Feed rate: 250 mm / min Depth of cut (a p ×a e ): 9mm x 0.3mm Cutting fluids: Water-soluble cutting fluids Machine used: 5-axis machining center ("MU-400VA", manufactured by Okuma Corporation) Workpiece material (difficult to machine): Inconel 718 (Size: 100mm x 100mm x 150mm, manufactured by VDM METALS)

[0107] <Method for manufacturing covered tools> Next, the details of the manufacturing methods for the coated tools of Examples 1-1 to 1-13 and Comparative Examples 1-1 to 1-6 are described below.

[0108] (Example 1-1) In Example 1-1, a hard coating was formed on a cutting tool for difficult-to-machine materials using an arc ion plating apparatus equipped with permanent magnets and a filter mechanism, thereby manufacturing a coated tool. The configuration of the coating apparatus and the specific method for forming the hard coating are described below.

[0109] Specifically, the detailed configuration of the film deposition apparatus used in Example 1-1 is as follows. The film deposition apparatus has multiple cathodes (arc evaporation sources), a vacuum chamber, and a substrate rotation mechanism. The cathode is equipped with an electromagnetic coil that focuses the plasma in front of the target and a permanent magnet on the back of the target. The cathode also has a filter mechanism that can reduce droplets using a magnetic field. The inside of the vacuum chamber can be evacuated by a vacuum pump, and gas can be introduced into the vacuum chamber from a supply port provided in the vacuum chamber. A bias power supply can be connected to the substrate placed inside the vacuum chamber, and a negative bias voltage can be applied independently to multiple substrates. The substrate rotation mechanism has a work table, a plate-shaped jig mounted on the work table, and a pipe-shaped jig mounted on the plate-shaped jig. In the substrate rotation mechanism, the work table rotates at a speed of 3 revolutions per minute. The plate-shaped jig and the pipe-shaped jig are each capable of rotating around and around.

[0110] First, the cutting tool for difficult-to-machine materials, which serves as the substrate, was fixed to a pipe-shaped jig inside the vacuum chamber of the film deposition apparatus, and the pre-deposition process was carried out as follows. Specifically, first, the inside of the vacuum chamber was filled to 5 × 10 -3 The vacuum chamber was evacuated to below Pa. Then, a heater installed inside the vacuum chamber was used to heat the cutting tool for difficult-to-machine materials to 500°C, and the inside of the vacuum chamber was evacuated again to 5 × 10 -3 The system was evacuated to a vacuum level below Pa.

[0111] Arc discharge was performed using a target made of Ti. Furthermore, a negative bias voltage up to 1000V was applied to the cutting tool for difficult-to-machine materials on the substrate side to perform metal bombardment.

[0112] After metal bombardment, nitrogen was introduced into the vacuum chamber, and the pressure inside the vacuum chamber was set to 4 Pa. Then, power was supplied to the cathode, and a negative bias voltage was applied to the cutting tool (substrate) for difficult-to-machine materials to form a hard coating approximately 2 μm thick. In this example, the thickness of the hard coating was measured by cross-sectional observation of images similar to those captured by the field emission scanning electron microscope described later, which was used to calculate the number of droplets. In Example 1-1, a target with a composition of Al content of 50 atomic%, Ti content of 40 atomic%, and Si content of 10 atomic% was used. The bias voltage was set to -60 V, and the arc current to 150 A. The composition of metallic and metalloid elements and the number of droplets in the hard coating of the coated tool of Example 1-1 manufactured in this way were measured and calculated using the method described above. Furthermore, the cutting performance of the coated tool of Example 1-1 was also evaluated using the method described above. These results are summarized in Table 1 below.

[0113] (Examples 1-2) In Example 1-2, a coated tool was manufactured in the same manner as in Example 1-1, except that argon bombardment was performed instead of metal bombardment, and a target with a composition of 60 atomic% Al content, 30 atomic% Ti content, and 10 atomic% Si content was used. Argon bombardment was performed by introducing Ar gas into a vacuum chamber, passing an electric current through a filament to generate Ar ions, and applying a negative bias voltage to the tool (substrate) for cutting difficult-to-machine materials. Similar to Example 1-1, the composition of metallic and metalloid elements in the hard coating and the number of droplets were measured and calculated for the coated tool manufactured in Example 1-2, and the cutting performance of the coated tool was also evaluated. These results are summarized in Table 1 below.

[0114] (Examples 1-3) In Example 1-3, coated tools were manufactured in the same manner as in Example 1-2, except that a target with a composition of 70 atomic% Al, 20 atomic% Ti, and 10 atomic% Si was used. Similar to Example 1-1, the composition of metallic and metalloid elements in the hard coating and the number of droplets were measured and calculated for the coated tools manufactured in Example 1-3, and the cutting performance of the coated tools was also evaluated. These results are summarized in Table 1 below.

[0115] (Examples 1-4 to 1-13) In Examples 1-4, etching was performed using a combination of argon and metal bombardment in addition to metal bombardment, the bias voltage during film formation was set to 120V, and a target having a composition of 30 atomic% Al content, 60 atomic% Ti content, and 10 atomic% Si content was used to manufacture coated tools in the same manner as in Example 1-1.

[0116] In Example 1-5, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 40 atomic% Al, 50 atomic% Ti, and 10 atomic% Si was used. In Example 1-6, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 50 atomic% Al and 50 atomic% Ti was used. In Example 1-7, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 50 atomic% Al, 47 atomic% Ti, and 3 atomic% Si was used. In Example 1-8, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 50 atomic% Al, 45 atomic% Ti, and 5 atomic% Si was used.

[0117] In Example 1-9, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 30 atomic% Al, 60 atomic% Ti, and 10 atomic% Nb was used. In Example 1-10, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 50 atomic% Al, 40 atomic% Ti, and 10 atomic% Nb was used. In Example 1-11, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 60 atomic% Al, 30 atomic% Ti, and 10 atomic% Nb was used. In Example 1-12, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 60 atomic% Al and 40 atomic% Ti was used. In Example 1-13, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 60 atomic% Al, 37 atomic% Ti, and 3 atomic% Nb was used.

[0118] Similar to Example 1-1, the composition of metallic and metalloid elements in the hard coating and the number of droplets were measured and calculated for the coated tools of Examples 1-4 to 1-13 that were manufactured, and the cutting performance of the coated tools was also evaluated. These results are summarized in Table 1 below.

[0119] (Comparative Example 1-1) In Comparative Example 1-1, a coated tool was manufactured in the same manner as in Example 1-1, except that a hard coating was formed using a general arc ion plating apparatus (manufactured by Kobe Steel, Ltd.) equipped with a permanent magnet but without a filter mechanism. Similar to Example 1-1, the composition of metallic and metalloid elements in the hard coating of the coated tool of Comparative Example 1-1, as well as the number of droplets, were measured and calculated, and the cutting performance of the coated tool was also evaluated. These results are summarized in Table 1 below.

[0120] (Comparative Example 1-2) In Comparative Example 1-2, coated tools were manufactured in the same manner as in Comparative Example 1-1, except that a target with a composition of 70 atomic% Al, 20 atomic% Ti, and 10 atomic% Si was used. Similar to Example 1-1, the composition of metallic and metalloid elements in the hard coating of the manufactured Comparative Example 1-2 coated tool, as well as the number of droplets, were measured and calculated, and the cutting performance of the coated tool was also evaluated. These results are summarized in Table 1 below.

[0121] (Comparative Examples 1-3 to 1-6) In Comparative Example 1-3, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 80 atomic% Al, 10 atomic% Ti, and 10 atomic% Si was used. In Comparative Example 1-4, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 50 atomic% Al, 30 atomic% Ti, and 20 atomic% Si was used. In Comparative Example 1-5, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 80 atomic% Al, 10 atomic% Ti, and 10 atomic% Nb was used. In Comparative Example 1-6, coated tools were manufactured in the same manner as in Example 1-4, except that a target with a composition of 60 atomic% Al, 20 atomic% Ti, and 20 atomic% Nb was used. Similar to Example 1-1, the composition of metallic and metalloid elements in the hard coating and the number of droplets were measured and calculated for the coated tools of Comparative Examples 1-3 to 1-6, and the cutting performance of the coated tools was also evaluated. These results are summarized in Table 1 below.

[0122] Table 1 below summarizes the composition of metallic and metalloid elements contained in the hard coating, the number of droplets, and the evaluation results of the cutting performance of the coated tools for each example and comparative example. As shown in Table 1 below, this example includes examples or comparative examples in which the total composition of metallic and metalloid elements contained in the hard coating does not equal 100 atomic percent. This is because the measured values ​​of each element have been rounded to two decimal places. The same applies to the examples shown in Table 2 below. In Table 1 below, "-" means that performance evaluation was not performed. For reference, Figure 1 shows a portion of the SEM image used to calculate the number of droplets in the cross-section of the hard coating of Example 1-1 (hard coating thickness 2.0 μm and length approximately 6 μm). Also, Figure 2 shows a portion of the SEM image used to calculate the number of droplets in the cross-section of the hard coating of Comparative Example 1-2 (hard coating thickness 2.0 μm and length approximately 6 μm). As shown in Figure 1, in Example 1-1, within a hard film thickness of 2.0 μm and a length of approximately 6 μm, there are only a few white, roughly circular areas that appear to be droplets. On the other hand, as shown in Figure 2, in Comparative Example 1-2, within a hard film thickness of 2.0 μm and a length of approximately 6 μm, there are numerous white, roughly circular areas that appear to be droplets.

[0123] [Table 1]

[0124] <Consideration> As shown in Table 1 above, the coated tools of Examples 1-1 to 1-13, in which the number of droplets within the predetermined range was 50 or less, received a tool life evaluation of "A," indicating excellent wear resistance (tool life) for machining difficult-to-cut materials. On the other hand, the coated tools of Comparative Examples 1-1 to 1-2, in which the number of droplets within the predetermined range exceeded 50, received a tool life evaluation of "B," indicating poor wear resistance for machining difficult-to-cut materials. From these results, the 1000 μm cross-section of the hard coating, with a length of 500 μm and a thickness of 2.0 μm, calculated by the method described above, 2When the number of droplets within the range is 50 or less, it was found that the coated tool with the hard film formed thereon has excellent wear resistance for machining difficult-to-cut materials. Furthermore, the number of droplets in the cross-section of such a hard film is easy to achieve by the arc ion plating method, but it is also assumed to vary depending on the composition of the film, the process during film formation by the arc ion plating method, and the like. Note that Comparative Examples 1-3 to Comparative Examples 1-6, for which the performance evaluation of tool life was not conducted, are also assumed to be inferior in wear resistance for machining difficult-to-cut materials because the number of droplets within the said predetermined range is large.

[0125] 2. Observation of the cross-sectional structure of the hard film by STEM and line analysis of the cross-sectional structure by EDX In Example 2-1 and Comparative Example 2-1, a hard film having a composition of predetermined metal elements and semi-metal elements was formed on a test piece by the arc ion plating method or the HiPIMS method to produce a coated test piece. Then, the cross-sectional structure of the hard film was observed by STEM. Furthermore, line analysis was performed on the cross-sectional structure by EDX.

[0126] Details of the test pieces used, the method for observing the cross-sectional structure of the hard film by STEM, and the method for line analysis by EDX are as follows.

[0127] <Test pieces> Test pieces made of a cemented carbide material with a size of 1.3 cm × 1.3 cm × 0.5 cm (thickness) were used as the base material.

[0128] <Method for observing the cross-sectional structure of the hard film by STEM> To observe the structure of the cross-section of the hard film of the manufactured coating test piece, using a focused ion beam apparatus (FIB) ("FB2200", manufactured by Hitachi High-Technologies Corporation), thin film processing was performed on the coating test piece so that the size would be 10 μm × 18 μm × 100 nm (thickness). Then, using a STEM ("JEM-2100F", manufactured by JEOL Ltd.), a dark field image of the structure of the cross-section parallel to the plane along the film thickness depth direction in the vicinity of 1 μm from the outermost surface of the hard film was obtained. Note that the magnification of the STEM was set to 1.5 million times in Example 2-1 and 1 million times in Comparative Example 2-1.

[0129] <Line analysis by EDX> Using an energy dispersive X-ray analyzer (EDX) ("JED-2300T", manufactured by JEOL Ltd.), line analysis was performed on the dark field image observed by STEM of the cross-section of the hard film under the following analysis conditions. (Analysis conditions) Accelerating voltage of electron beam: 200 kV Number of measurement points: 50 points Integration time per point: 20 seconds

[0130] <Manufacturing method of coating tool> Next, the details of the manufacturing methods of the coating test pieces of Example 2-1 and Comparative Example 2-1 will be described below.

[0131] (Example 2-1) In Example 2-1, a coating test piece was manufactured by the same method as in Example 1-1, except that the above-mentioned test piece was used instead of a tool for cutting difficult-to-machine materials as the base material.

[0132] The structure of the cross-section of the hard film of the coating test piece manufactured in this way was observed and analyzed by the method described above.

[0133] (Comparative Example 2-1) In Comparative Example 2-1, the same test piece as in Example 2-1 was used as the base material, and a hard film was formed by the HiPIMS method to manufacture a coating test piece.

[0134] Specifically, using a general HiPIMS deposition apparatus (manufactured by Hauzer), sputtering power (average power 8kW, pulse width 1500μs) was applied to a target having a composition of 60 atomic% Al content and 40 atomic% Ti content, and a coated test specimen with a hard film thickness of 2.55μm was obtained by sputtering the target metal.

[0135] The microstructure of the cross-section of the hard coating of the coated test specimens prepared in this manner was observed and analyzed using the method described above, similar to the method used in Example 2-1.

[0136] <Consideration> Figure 3 shows a dark-field image of the microstructure of the cross-section of the hard coating in Example 2-1, as observed by STEM. As shown in Figure 3, when the hard coating was formed by arc ion plating, the dark-field image of the microstructure of the cross-section of the hard coating, as observed by STEM, showed a striped structure in which black layers (shown relatively in black) and white layers (shown relatively in white) are repeated relative to each other in units of several nanometers in the film thickness depth direction. Figure 4 shows a dark-field image of the microstructure of the cross-section of the hard coating in Comparative Example 2-1, as observed by STEM. However, the dark-field image shown in Figure 4 is a dark-field image acquired at 1,000,000x magnification and then magnified 1.5x for comparison with the dark-field image acquired in Example 2-1. As shown in Figure 4, when the hard coating was formed by HiPIMS, such a striped structure was not observed.

[0137] Figure 5 shows the results of line analysis by EDX on the dark-field image observed by STEM shown in Figure 3. As can be seen from the line analysis in Figure 5, when a hard coating was formed by arc ion plating, the nitrogen content and the metallic components Al and Ti content along the film thickness depth direction showed inverse changes in their increase and decrease. That is, in areas where the nitrogen content in the coating was relatively increased (black layer), the metallic components Al and Ti were relatively decreased. On the other hand, in areas where the nitrogen content in the coating was relatively decreased (white layer), the Al and Ti content were relatively increased.

[0138] As shown in Figure 5, the spacing between the stripes of the black layer (shown relatively as black) and the white layer (shown relatively as white) was approximately 6 nm, and the total film thickness of the white layer (6 nm) and the black layer (6 nm) was approximately 12 nm. During the formation of the hard coating on the coated test piece in Example 2-1, the amount of film deposited per rotation of the work table in the aforementioned apparatus was set to 11.7 nm, and it was observed that the rotation period of the work table and the spacing of the stripes were roughly in agreement.

[0139] Figure 6 shows the results of line analysis by EDX on the dark-field image observed by STEM as shown in Figure 4. As can be seen from the line analysis in Figure 6, when a hard film was formed by the HiPIMS method, there was almost no tendency for the nitrogen content and the content of metal components Al and Ti along the film thickness depth direction to show inverse changes in their increase or decrease. Therefore, as mentioned above, when observed by STEM at a magnification of 1.5 million times, the striped structure of the black layer, which is shown as relatively black, and the white layer, which is shown as relatively white, as shown in Figures 3 and 5, was not observed. This is thought to be because the ionization rate of metal components in the film formation process of the HiPIMS method is lower than that of the arc ion plating method, making it difficult for metal component ions to circulate within the apparatus and form a film.

[0140] These results indicate that arc ion plating achieved better film deposition than HiPIMS, a type of sputtering method. In other words, compared to HiPIMS, the arc ion plating method results in higher adhesion at the interface with the substrate. Therefore, it is expected that this method can ultimately produce coated tools with excellent wear resistance suitable for machining difficult-to-cut materials.

[0141] 3. Formation of hard coatings of other components on tools for cutting difficult-to-machine materials. In Examples 3-1 to 3-8, coated tools were actually manufactured in which a laminated film containing a first hard coating and a second hard coating was formed on a tool for cutting difficult-to-machine materials.

[0142] <Method for manufacturing covered tools> The details of the manufacturing method for the coated tools of Examples 3-1 to 3-8 are described below.

[0143] (Example 3-1) In Example 3-1, a hard coating including a first hard coating and a second hard coating was formed on a tool for cutting difficult-to-machine materials using the same arc ion plating apparatus as used in Examples 1-1 to 1-13, thereby manufacturing a coated tool.

[0144] First, the cutting tool for difficult-to-machine materials, which serves as the substrate, was fixed to a pipe-shaped jig inside the vacuum chamber of the film deposition apparatus, and the pre-deposition process was carried out as follows. Specifically, first, the inside of the vacuum chamber was filled to 5 × 10 -3 The vacuum chamber was evacuated to below Pa. Then, a heater installed inside the vacuum chamber was used to heat the cutting tool for difficult-to-machine materials to 500°C, and the inside of the vacuum chamber was evacuated again to 5 × 10 -3 The system was evacuated to a vacuum level below Pa.

[0145] Next, argon gas, an inert gas, was introduced into the vacuum chamber, and filament discharge was performed. By applying a negative bias voltage of 150V to the cutting tool for difficult-to-machine materials on the substrate side, argon bombardment was carried out.

[0146] Arc discharge was performed using a target made of Ti. Furthermore, a negative bias voltage up to 1000V was applied to the cutting tool for difficult-to-machine materials on the substrate side to perform metal bombardment.

[0147] After metal bombardment, nitrogen was introduced into the vacuum chamber, and the pressure inside the vacuum chamber was set to 3.5 Pa. Then, power was supplied to the cathode, and a negative bias voltage was applied to the cutting tool (base material) for difficult-to-machine materials to deposit a first layer (first hard coating) with a thickness of approximately 1.7 μm. Subsequently, a second layer (second hard coating) with a thickness of approximately 0.3 μm was deposited on the first hard coating, and a coated tool with a laminated film with a total thickness of approximately 2 μm was manufactured. The thickness of the hard coating was measured using the same method as described in Example 1-1.

[0148] In Example 3-1, the first hard film was deposited using a target with a composition of 50 atomic% Al, 45 atomic% Ti, and 5 atomic% Si, and the second hard film was deposited using a target with a composition of 70 atomic% Ti and 30 atomic% Si. For the deposition of the first hard film, the bias voltage was -120V and the arc current was 150A. For the deposition of the second hard film, the bias voltage was initially -50V and then changed to -65V. The arc current was also 150A. The composition of the laminated film and the number of droplets in the laminated film itself of the coated tool manufactured in Example 3-1 were measured and calculated using the same method as described in section 1 above. Specifically, the composition of the laminated film, i.e., the composition of the metallic and metalloid elements in the first and second hard coatings, was calculated using a method that will be described in detail later. Furthermore, the cutting performance of the coated tool in Example 3-1 was also evaluated using the same method described above. These results are summarized in Table 2 below.

[0149] (Examples 3-2 to 3-8) In Example 3-2, a coated tool was manufactured in the same manner as in Example 3-1, except that a second hard coating was formed using a target having a composition with a Ti content of 75 atomic% and a Si content of 25 atomic%. In Example 3-3, a coated tool was manufactured in the same manner as in Example 3-1, except that a second hard coating was formed using a target having a composition with a Ti content of 80 atomic% and a Si content of 20 atomic%. In Example 3-4, a coated tool was manufactured in the same manner as in Example 3-1, except that a second hard coating was formed using a target having a composition with a Ti content of 90 atomic% and a Si content of 10 atomic%.

[0150] In Example 3-5, a coated tool was manufactured in the same manner as in Example 3-1, except that a first hard coating was formed using a target having a composition of 60 atomic% Al, 30 atomic% Ti, and 10 atomic% Nb. In Example 3-6, a coated tool was manufactured in the same manner as in Example 3-5, except that a second hard coating was formed using a target having a composition of 75 atomic% Ti and 25 atomic% Si. In Example 3-7, a coated tool was manufactured in the same manner as in Example 3-5, except that a second hard coating was formed using a target having a composition of 80 atomic% Ti and 20 atomic% Si. In Example 3-8, a coated tool was manufactured in the same manner as in Example 3-5, except that a second hard coating was formed using a target having a composition of 90 atomic% Ti and 10 atomic% Si.

[0151] Similar to Example 3-1, the composition of the laminated film and the number of droplets in the laminated film itself were measured and calculated for the coated tools manufactured in Examples 3-2 to 3-8, and the cutting performance of the coated tools was also evaluated. These results are summarized in Table 2 below.

[0152] <Method for calculating the composition of metallic and metalloid elements in the first and second hard coatings> When the composition of the laminated film in Examples 3-1 to 3-8 is measured by the method described in 1. above, the composition of the laminated film including the first hard film and the second hard film is measured. Therefore, the composition of metallic and metalloid elements of only the second hard film in Examples 3-1 to 3-8, shown in Table 2 below, was calculated by the following method. First, the composition of the laminated film was measured by the method described in 1. above. Next, based on the measurement result of the composition of only the first hard film (see Table 1 above), the converted value of the composition of only the first hard film in the laminated film was calculated, and the converted value of the composition of only the first hard film was calculated by subtracting the converted value of the composition of only the first hard film from the composition of the laminated film.

[0153] For example, the composition (converted values ​​of composition) of the metallic and metalloid elements in the second hard coating of Example 3-1 in Table 2, described later, was determined from the following formulas (i) to (v). (i) Measurement results of the composition of the laminated film in Example 3-1 Al: 13.05 atomic% Ti:67.63 atomic% Si:19.32 atomic% (ii) Measurement results of the composition of only the first hard coating in Example 3-1 (see Examples 1-8 in Table 1 above) Al:44.50 atomic% Ti:52.69 atomic% Si:2.82 atomic% (iii) Calculation of the converted value of the composition of only the first hard coating in the laminated film of Example 3-1 Al: 44.50 × (13.05 / 44.50) = (a1) Atomic % Ti:52.69×(13.05 / 44.50)=(b1) atomic% Si:2.82×(13.05 / 44.50)=(c1) atomic% (iv) Subtract the converted value of the composition of the first hard coating only from the composition of the laminated film of Example 3-1. Al:13.05-(a1)=(a2) atomic%(=0 atomic%) Ti:67.63-(b1)=(b2) atomic% Si:19.32-(c1)=(c2) atomic% (v) Calculate the converted value of the composition of the second hard coating. Ti:[(b2) / ((b2)+(c2))]×100=approx. 73.83 atomic% Si:[(c2) / ((b2)+(c2))]×100=approximately 26.17 atomic%

[0154] The composition of metallic and metalloid elements in the second hard coatings of Examples 3-2 to 3-4 was also determined by the same method as described above.

[0155] Furthermore, for example, the composition (converted values ​​of composition) of the metallic and metalloid elements in the second hard coating of Examples 3-5 in Table 2, described later, was determined from the following calculation formulas (i) to (v). (i) Measurement results of the composition of the laminated films in Examples 3-5 Al: 14.55 atomic% Ti:65.14 atomic% Nb:2.37 atomic% Si:17.94 atomic% (ii) Measurement results of the composition of only the first hard coating in Examples 3-5 (see Examples 1-11 in Table 1 above) Al: 54.45 atomic% Ti:37.02 atomic% Nb:8.53 atomic% Si:0 atomic% (iii) Calculation of the converted value of the composition of only the first hard coating in the laminated film of Examples 3-5 Al+Nb:(54.45+8.53)×[(14.55+2.37) / (54.45+8.53)]=((d1)+(e1)) atomic% Ti:37.02×[(14.55+2.37) / (54.45+8.53)]=(f1) atomic% Si:0×[(14.55+2.37) / (54.45+8.53)]=(g1) atomic%(=0 atomic%) (iv) Subtract the converted value of the composition of the first hard coating only from the composition of the laminated film in Examples 3-5. Al+Nb:16.92-((d1)+(e1))=((d2)+(e2))(=0 atom%) Ti:65.14-(f1)=(f2) atomic% Si:17.94-0=(g2) atomic% (=17.94 atomic%) (v) Calculate the converted value of the composition of the second hard coating. Ti:[(f2) / ((f2)+(g2)(=17.94)]×100=approx. 75.47 atomic% Si:[(g2)(=17.94) / ((f2)+(g2)(=17.94)]×100=approx. 24.53 atomic%

[0156] The composition of metallic and metalloid elements in the second hard coatings of Examples 3-6 to 3-8 was also determined by the same method as described above.

[0157] Table 2 below shows the composition of the first and second hard coatings in the laminated film of the coated tools in Examples 3-1 to 3-8, the number of droplets in the laminated film itself, and the evaluation results of the cutting performance of the coated tools. The measurement results of Comparative Example 1-2, which served as the standard for the cutting performance of the coated tools, are also shown again.

[0158] [Table 2]

[0159] <Consideration> As shown in Table 2 above, the coated tools of Examples 3-1 to 3-8, in which the number of droplets within a predetermined range of the laminated film itself was 50 or less, received an "A" rating for tool life evaluation and exhibited excellent wear resistance (tool life) for machining difficult-to-cut materials. From these results, even when the hard coating has a two-layer structure consisting of a first hard coating and a second hard coating, the 1000 μm cross-section of the hard coating, calculated by the method described above, has a length of 500 μm and a thickness of 2.0 μm. 2 It was found that when the number of droplets within the specified range is 50 or less, the coated tool with the hard coating has excellent wear resistance for machining difficult-to-cut materials.

[0160] This application is based on Japanese Patent Application No. 2024-182577, filed on 18 October 2024, and its contents are included in this application.

[0161] The embodiments and examples disclosed herein should be understood in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than by the foregoing description, and all modifications within the meaning and scope equivalent to the claims are intended.

Claims

1. The invention comprises a tool for cutting difficult-to-machine materials and a hard coating formed on at least a portion of the outer surface of the tool for cutting difficult-to-machine materials. The hard coating comprises a nitride of a metallic element or a nitride of a metallic element and a metalloid element. The cross-section of the hard coating shows a continuous 1000 μm ２ The number of droplets within the range is 50 or less. The hard coating is a coated tool for cutting difficult-to-machine materials, wherein when a cross-section of the hard coating approximately 1 μm in the film thickness depth direction from the outermost surface is observed by STEM at a magnification of 1.5 million times, the dark-field image of the structure of the cross-section of the hard coating shows a striped structure including a black layer shown relatively in black and a white layer shown relatively in white.

2. The hard coating is a hard coating containing a nitride mainly composed of Al and Ti. The coating tool for cutting difficult-to-machine materials according to claim 1, wherein the total amount of the metal element and metalloid element contained in the hard coating is such that the Al content is 80 atomic percent or less, the Ti content is less than 75 atomic percent, and the total content of Al and Ti is 75 atomic percent or more.

3. The hard coating is a hard coating containing a nitride mainly composed of Al and Ti. The coating tool for cutting difficult-to-machine materials according to claim 1, wherein the total amount of the metal elements and metalloid elements contained in the hard coating is such that the Al content is 80 atomic% or less, the Ti content is less than 75 atomic%, the Si content is greater than 0 atomic%, and the total content of Al, Ti, and Si is 100 atomic%.

4. The hard coating is a hard coating containing a nitride mainly composed of Al and Ti. The coating tool for cutting difficult-to-machine materials according to claim 1, wherein the total amount of the metal elements and metalloid elements contained in the hard coating is such that the Al content is 20 atomic% or more and 70 atomic% or less, the Ti content is 20 atomic% or more and 70 atomic% or less, the Si content is greater than 0 atomic%, and the total content of Al, Ti and Si is 100 atomic%.

5. The hard coating is a hard coating containing a nitride mainly composed of Al and Ti. The coating tool for cutting difficult-to-machine materials according to claim 1, wherein the total amount of the metal elements and metalloid elements contained in the hard coating is such that the Al content is 80 atomic% or less, the Ti content is less than 75 atomic%, the Nb content is greater than 0 atomic%, and the total content of Al, Ti, and Nb is 100 atomic%.

6. The hard coating is a hard coating containing a nitride mainly composed of Al and Ti. The coating tool for cutting difficult-to-machine materials according to claim 1, wherein the total amount of the metal element and metalloid element contained in the hard coating is such that the Al content is 20 atomic% or more and 70 atomic% or less, the Ti content is 20 atomic% or more and 70 atomic% or less, the Nb content is greater than 0 atomic%, and the total content of Al, Ti and Nb is 100 atomic%.

7. The invention comprises a tool for cutting difficult-to-machine materials, and a laminated film including a first hard coating formed on at least a portion of the outer surface of the tool for cutting difficult-to-machine materials and a second hard coating formed on the first hard coating. The aforementioned laminated film comprises a nitride of a metallic element or a nitride of a metallic element and a metalloid element. Continuous 1000 μm in the cross-section of the aforementioned laminated film ２ The number of droplets within the range is 50 or less. When the cross-section of the laminated film near 1 μm in the film thickness depth direction from the outermost surface of the laminated film is observed by STEM at a magnification of 1,500,000 times, the dark-field image of the structure of the observed cross-section of the laminated film has a striped structure that includes a black layer shown relatively as black and a white layer shown relatively as white. The first hard coating is a hard coating containing a nitride mainly composed of Al and Ti, and has a composition in the total amount of the metal elements and metalloid elements contained in the hard coating according to any one of claims 2 to 6. The second hard coating is a hard coating containing a nitride mainly composed of Ti, A coated tool for cutting difficult-to-machine materials, wherein the total amount of the metal elements and metalloid elements contained in the second hard coating is such that the Ti content is 70 atomic% or more and 95 atomic% or less, the Si content is 5 atomic% or more and 30 atomic% or less, and the total content of Ti and Si is 100 atomic%.

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