Coated tool for cutting hard-to-cut materials

Abstract

The present invention provides a coated tool for cutting hard-to-cut materials that has excellent wear resistance. This coated tool for cutting hard-to-cut materials comprises a tool for cutting hard-to-cut materials and a hard film that is formed on at least a portion of the outer surface of the tool for cutting hard-to-cut materials. The hard film includes a nitride of a metal element or a nitride of a metal element and a metalloid element. In a cross-section of the hard film, the number of droplets in a continuous range of 1000 μm2 is 50 or less. The hard film has a stripe pattern structure in which, when a cross-section in the vicinity of 1 μm from the outermost surface of the hard film in the film thickness depth direction is observed using a STEM at a magnification of 1,500,000 times, a dark-field image of the structure of the observed cross-section of the hard film includes a black layer that shows as relatively black and a white layer that shows as relatively white.

Description

Coated tools for machining difficult-to-cut materials

[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.

[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, 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 the hardness and elastic recovery rate measured by the nanoindentation method are within a specific range, and the number of droplets within a specific range and of a specific size or larger is below a predetermined number.

[0006] Japanese Patent Publication No. 2023-172656, Japanese Patent Publication No. 6034579

[0007] The present invention aims to provide a coated tool for cutting difficult-to-machine materials that has excellent wear resistance.

[0008] The inventors of this invention have diligently studied and researched the above problems, and as a result have arrived at the present invention.

[0009] A coated tool for cutting difficult-to-machine materials according to a first aspect of the present 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, wherein the hard coating comprises 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 observed has a striped structure that includes a black layer shown relatively as black and a white layer shown relatively as white.

[0010] Figure 1 is a portion of the SEM image used to calculate the number of droplets in the cross-section of the hard coating in Example 1-1. Figure 2 is a portion of the SEM image used to calculate the number of droplets in the cross-section of the hard coating in Comparative Example 1-2. Figure 3 is a dark-field image of the microstructure of the cross-section of the hard coating in Example 2-1 observed by STEM. Figure 4 is a dark-field image of the microstructure of the cross-section of the hard coating in Comparative Example 2-1 observed by STEM (however, the acquired dark-field image is shown magnified 1.5 times). Figure 5 is the result of line analysis by EDX on the dark-field image observed by STEM shown in Figure 3. Figure 6 is the result of line analysis by EDX on the dark-field image observed by STEM shown in Figure 4.

[0011] According to the manufacturing method described in Patent Document 1, droplets are not present on the surface or within the layer II formed on the layer I by sputtering. However, because the layer II 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 layer II formed by sputtering wears away and reaches the layer I formed by arc ion plating, which contains droplets. Upon reaching the layer I, droplets contained within the layer I surface, causing welding with the workpiece, and tool wear due to welding progresses.

[0012] Furthermore, the HiPIMS method described in Patent Document 2 can improve the metal ionization rate in the film deposition process compared to the conventional sputtering method. However, even with the HiPIMS method, the metal ionization rate is lower than that of the arc ion plating method, so there is room for improvement in the wear resistance of the cutting coated tool.

[0013] In light of these circumstances, cutting tools require further improvements in their physical properties, especially when used in applications that demand high adhesion resistance and strong bonding at the interface between the substrate and the coating, such as in machining difficult-to-cut materials.

[0014] 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.

[0015] Thus, according to the present invention, it is possible to provide a coated tool for cutting difficult-to-machine materials that has excellent wear resistance.

[0016] 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.).

[0017] 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.

[0018] 1. Configuration of a coated tool for machining difficult-to-machine materials First, the configuration of the coated tool for machining 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 machining difficult-to-machine materials and a hard coating formed on at least a part of the outer surface of the tool for machining difficult-to-machine materials.

[0019] 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.

[0020] 1-1. Tools for Cutting Difficult-to-Machine Materials The types of tools 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, etc.

[0021] 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, CBN sintered body, and the like.

[0022] 1-2. Hard coating The hard coating is formed on at least a portion of the outer surface of the tool for cutting difficult-to-machine materials, as described above, by, for example, the method described later. The hard coating in this embodiment will be described in detail below.

[0023] <Composition of 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 contains nitrides of metallic elements or nitrides of metallic elements and metalloid elements, a hard coating with excellent hardness can be obtained.

[0024] (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 containing Al and Ti as the main components of the hard coating, a hard coating good for machining difficult-to-machine materials can be reliably obtained.

[0025] 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.

[0026] When the hard film contains a nitride containing Al and Ti as main components, in the total amount of metal elements and metalloid elements contained in the hard film, the Al content is preferably 80 atomic% or less. When the Al content is 80 atomic% or less, a good hard film can be surely obtained for the cutting application of difficult-to-machine materials. The Al content is more preferably 70 atomic% or less, further preferably 68 atomic% or less, and particularly preferably a value selected from the group consisting of 65 atomic%, 63 atomic%, 60 atomic% and 58 atomic% or less.

[0027] In this specification, the composition in the total amount of metal elements and metalloid elements contained in the hard film such as the Al content and the Ti content means the composition (or average composition) of the metal elements and metalloid elements contained in the hard film. The composition (or average composition) of the metal elements 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 as described in the later examples, or by analysis using an electron probe microanalyzer device or the like. When the hard film is composed of a laminated film including a first hard film and a second hard film as described later, the composition of the metal elements and metalloid elements contained in the film of each layer is a value calculated as a converted value of the composition of the film of each layer by the method described in detail in the later examples.

[0028] When the hard film contains a nitride containing Al and Ti as main components, in the total amount of metal elements and metalloid elements contained in the hard film, the Al content is preferably 20 atomic% or more. When the Al content is 20 atomic% or more, the heat resistance of the hard film can be improved. The Al content is more preferably 30 atomic% or more, further preferably 35 atomic% or more, and particularly preferably a value selected from the group consisting of 40 atomic%, 43 atomic%, 45 atomic%, 47 atomic%, 49 atomic% and 50 atomic% or more.

[0029] When the hard film contains a nitride containing Al and Ti as main components, in the total amount of metal elements and metalloid elements contained in the hard film, the Ti content is preferably less than 75 atomic %. When the Ti content is less than 75 atomic %, the Al content in the hard film can be sufficiently ensured, so that the heat resistance of the hard film can be improved. The Ti content is more preferably 60 atomic % or less, further preferably 50 atomic % or less, and particularly preferably a value selected from the group consisting of 45 atomic %, 42 atomic %, and 40 atomic % or less.

[0030] When the hard film contains a nitride containing Al and Ti as main components, in the total amount of metal elements and metalloid elements contained in the hard film, the Ti content is preferably 10 atomic % or more. By setting the Ti content to 10 atomic % or more, it is possible to prevent the Al content in the hard film from becoming excessively large and becoming an inappropriate hard film for cutting applications of difficult-to-machine materials. Also, when the Ti component is 10 atomic % or more, the strength and toughness of the hard film can be ensured. The Ti content is more preferably 15 atomic % or more, further preferably 18 atomic % or more, and even more preferably a value selected from the group consisting of 20 atomic %, 22 atomic %, 25 atomic %, 30 atomic %, and 33 atomic % or more.

[0031] When the hard film contains a nitride containing Al and Ti as main components, in the total amount of metal elements and metalloid elements contained in the hard film, the total content of Al and Ti is preferably 75 atomic % or more. When the total content of Al and Ti is 75 atomic % or more, a hard film having excellent wear resistance for cutting applications of difficult-to-machine materials, and in addition to heat resistance, also having strength and toughness can be obtained. The total content of Al and Ti is more preferably 80 atomic % or more, further preferably 83 atomic % or more, and particularly preferably a value selected from the group consisting of 85 atomic %, 88 atomic %, 90 atomic %, and 91 atomic % or more. The upper limit value of the total content of Al and Ti is not particularly limited and may be 100 atomic % or less.

[0032] 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.

[0033] (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 contain one or more elements from among the 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.

[0034] 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.

[0035] 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 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%.

[0036] 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.

[0037] As mentioned above, the hard coating may also contain one or more elements from among the metalloid elements Si and the metal element Nb. Therefore, the preferred upper or lower limits for the Si content and / or Nb content in the hard coating are the same as the preferred upper or lower limits for the total content of one or more elements from among the metal elements other than Al and Ti and the metalloid elements mentioned above.

[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 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%. With this hard coating, it is possible to more reliably obtain coated tools with excellent wear resistance for machining difficult-to-cut materials.

[0039] 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 atomic% to 70 atomic%, the Ti content is 20 atomic% 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.

[0040] 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.

[0041] 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, the Al content is preferably 20 atomic% to 70 atomic%, the Ti content is preferably 20 atomic% to 70 atomic%, the Nb content is preferably greater than 0 atomic%, and the total content of Al, Ti, and Nb is preferably 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.

[0042] (Unavoidable Impurities) In addition to one or more elements from the metallic and metalloid elements contained in the hard coating as described above, the composition of the hard coating may also include 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 elements from the 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 the specific one or more elements.

[0043] <Number of droplets in the cross-section of the hard coating> In this embodiment, the number of continuous droplets in the cross-section of the hard coating is 1000 μm. 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.

[0044] The number of droplets within that range is preferably 45 or less, more preferably 40 or less, even more preferably 35 or less, and particularly preferably less than or equal to a value selected from the group consisting of 33, 31, 29, and 27.

[0045] In this specification, "droplet" refers to a metal particle present in the cross-section of a hard coating. Specifically, a "droplet" is defined as the length L of the longer side of a hypothetical rectangle or approximate square that circumscribes the metal particle present in the cross-section of the hard coating. ａ (μm) or the length of one side of the approximate square L ａ (μm), condition: 0.1 (μm)≦L ａ It refers to particles that satisfy the condition.

[0046] Furthermore, in this specification, "continuous 1000 μm in the cross-section of the hard coating" ２ The number of droplets within the range refers to a predetermined continuous 1000 μm in the cross-section of the hard coating. ２ This refers to the number of droplets within a certain range. Specifically, it refers to "a continuous 1000 μm in the cross-section of the hard coating."２ The "number of droplets within the range" refers to, as will be described in detail in the later examples, the number of droplets within a continuous 1000 μm in the cross-section of the hard film near the tip end portion of the cutting edge on the rake face side of the outer peripheral cutting edge of the coating tool. ２ That is, it is the number of droplets within the range.

[0047] Also, in this specification, the "continuous 1000 μm range in the cross-section of the hard film" ２ When the thickness (film thickness) of the hard film is about 2 μm, it means 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 (that is, 2.0 μm × 500 μm = 1000 μm ２ range).

[0048] Alternatively, in this specification, the "continuous 1000 μm range in the cross-section of the hard film" ２ When the thickness of the hard film is less than 2 μm, it means the range in the cross-section of the hard film with a thickness of x μm (less than 2.0 μm) and a length of y μm parallel to the direction orthogonal to the film thickness depth direction set based on the thickness x μm so that the range is 1000 μm ２ [[ID=十七]] That is, the range of x μm (less than 2.0 μm) × y μm = 1000 μm ２ range).

[0049] Further, in this specification, the "continuous 1000 μm range in the cross-section of the hard film" ２ When the thickness of the hard film is more than 2 μm, it means the range in the cross-section of the hard film with a length of 2.0 μm in the film thickness depth direction at an arbitrarily selected position and a length of 500 μm parallel to the direction orthogonal to the film thickness depth direction (that is, 2.0 μm × 500 μm = 1000 μm ２ range).

[0050] The number of droplets present in such a continuous predetermined range in the cross-section of the hard film can be observed and measured, for example, using a scanning electron microscope (SEM), as will be described in detail in the later examples.

[0051] <Structural Structure of the Hard Coating Cross-Section> In this embodiment, when the 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 structural structure of the cross-section of the hard coating observed 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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 on 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.

[0056] The microstructure of such hard coatings as observed by STEM will be described in more detail in later examples.

[0057] <Thickness of the hard coating> The thickness of the hard coating is not particularly limited, but it is preferably 1 μm or more. When the thickness of the hard coating is 1 μm or more, the wear resistance of the hard coating to stress can be further improved, and a coated tool with superior wear resistance can be obtained.

[0058] 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.

[0059] 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.

[0060] 2. Other configurations of coated tools for machining difficult-to-machine materials In this embodiment, a base layer may be provided between the tool for machining difficult-to-machine materials and the hard coating, as necessary, in order to further improve the adhesion between the tool for machining difficult-to-machine materials and the hard coating, provided that the wear resistance effect of the coated tool of this embodiment is not impaired. The base layer can be formed from one or more layers of metal, nitride, carbonitride, and carbide, for example.

[0061] 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.

[0062] Furthermore, on top of the hard coating formed on the outer surface of the tool for cutting difficult-to-machine materials (hereinafter referred to as the "first hard coating"), another hard coating (hereinafter referred to as the "second hard coating") may be formed, 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. Furthermore, on top of the laminated coatings, yet another hard coating (hereinafter referred to as the "third hard coating") may be formed, satisfying the conditions for the number of droplets and the cross-section of the hard coating in this embodiment.

[0063] 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 area of ​​the hard coating in this embodiment.

[0064] 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. ２ The 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 of the laminated film near 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 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.

[0065] 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).

[0066] 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.

[0067] 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%. Alternatively, 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%.

[0068] 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%.

[0069] 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).

[0070] 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.

[0071] 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 percent or more, more preferably 10 atomic percent or more, even more preferably 15 atomic percent or more, and particularly preferably 20 atomic percent 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 percent or less, more preferably 25 atomic percent or less, and even more preferably 20 atomic percent or less.

[0072] 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%.

[0073] 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.

[0074] 3. Method for Manufacturing Coated Tools for Machining Difficult-to-Machine Materials The coated tool for machining 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. In order to satisfy the cross-sectional conditions of the hard coating in this embodiment, the arc ion plating method 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.

[0075] A film deposition apparatus used in arc ion plating includes, for example, an arc evaporation source equipped with a target which is the material for the hard film, an anode which is the destination for electrons during arc discharge, an arc power supply for supplying arc current to the target, a furnace (vacuum vessel) which houses 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.

[0076] 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.

[0077] First, the furnace is evacuated. At that time, the vacuum pressure is 10 x 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.

[0078] 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.

[0079] 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 then 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).

[0080] 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.

[0081] 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.

[0082] 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 a large amount of ions and improve the etching effect, but other problems arise. Specifically, if the arc current is too high, a large amount of 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 set the arc current too high.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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 increases, 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.

[0089] The arc current supplied to the target is preferably 50A to 200A.

[0090] As mentioned above, by forming a hard coating using an arc ion plating method with a film deposition apparatus equipped with permanent magnets, a filter mechanism, etc., the number of droplets can be reduced, and a hard coating with excellent surface smoothness can be easily obtained.

[0091] In other words, by applying such an arc ion plating method to form a hard coating on a tool for cutting difficult-to-machine materials, coated tools that satisfy the conditions for the number of droplets and the cross-section of the hard coating in this embodiment can be manufactured more easily. However, as can be seen from the results of the examples described later, even when a hard coating is formed by applying the same arc ion plating method, depending on the composition of the target (or the composition of metallic and metalloid elements contained in the hard coating that is ultimately formed), the coated tool may not satisfy the condition for the number of droplets in this embodiment. Therefore, by selecting an appropriate composition for the target and forming a hard coating using the arc ion plating method described above, it is possible to obtain a coated tool that satisfies both the conditions for the number of droplets and the cross-section of the hard coating in this embodiment. Since the coated tools manufactured in this way have excellent wear resistance, they can be suitably applied even in high-load and unique applications such as cutting difficult-to-machine materials.

[0092] As described above, this specification discloses various aspects of technology, the main technologies among them are summarized below.

[0093] A coated tool for cutting difficult-to-machine materials according to a first aspect of the present 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, wherein the hard coating comprises 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 observed has a striped structure that includes a black layer shown relatively as black and a white layer shown relatively as white.

[0094] A coated tool for cutting difficult-to-machine materials according to a second aspect of the present invention is a coated tool for cutting difficult-to-machine materials according to a first aspect, wherein the hard coating is a hard coating containing a nitride mainly composed of Al and Ti, and in the total amount of the metal elements and metalloid elements contained in the hard coating, 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.

[0095] A coated tool for cutting difficult-to-machine materials according to a third aspect of the present invention is a coated tool for cutting difficult-to-machine materials according to a first or second aspect, wherein the hard coating is a hard coating containing a nitride mainly composed of Al and Ti, and in the total amount of the metal elements and metalloid elements contained in the hard coating, 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%.

[0096] A coated tool for cutting difficult-to-machine materials according to a fourth aspect of the present invention is a coated tool for cutting difficult-to-machine materials according to any one of the first to third aspects, wherein the hard coating is a hard coating containing a nitride mainly composed of Al and Ti, and 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 Si content is greater than 0 atomic%, and the total content of Al, Ti and Si is 100 atomic%.

[0097] A coated tool for cutting difficult-to-machine materials according to a fifth aspect of the present invention is a coated tool for cutting difficult-to-machine materials according to a first or second aspect, wherein the hard coating is a hard coating containing a nitride mainly composed of Al and Ti, and in the total amount of the metal elements and metalloid elements contained in the hard coating, 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%.

[0098] A coated tool for cutting difficult-to-machine materials according to a sixth aspect of the present invention is a coated tool for cutting difficult-to-machine materials according to any one of the first, second, and fifth aspects, wherein the hard coating is a hard coating containing a nitride mainly composed of Al and Ti, and 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%.

[0099] 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, wherein the laminated film includes a nitride of a metallic element or a nitride of a metallic element and a metalloid element, and the cross-section of the laminated film has a continuous 1000 μm ２ The number of droplets within the range is 50 or less, and 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 including a black layer shown relatively as black and a white layer shown relatively as white, the first hard film is a hard film containing a nitride mainly composed of Al and Ti, and has the composition of the total amount of the metal elements and metalloid elements contained in the hard film described in any of the second to sixth embodiments, the second hard film is a hard film containing a nitride mainly composed of Ti, and in the total amount of the metal elements and metalloid elements contained in the second hard film, 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%.

[0100] 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.

[0101] 1. Formation of hard coatings 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 hard coatings formed on them were actually manufactured, the composition of metallic and metalloid elements contained in the hard coatings was measured, the number of droplets was calculated, and the cutting performance of the coated tools was evaluated.

[0102] Details regarding the cutting tools used for difficult-to-machine 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.

[0103] <Tools for cutting difficult-to-machine materials> For cutting difficult-to-machine materials, a 6mm diameter, four-flute carbide square end mill was used.

[0104] <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 coating 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 15 kV, a live time of 100 s, and a process time of 4.

[0105] <Method for calculating the number of droplets in the cross-section of the 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 (Struers' "TegraPol-31" (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 South Bay Technology's "MODEL900" (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. After that, 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.

[0106] Subsequently, the cross-section of the hard coating that had undergone the finishing process was observed again using an 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 was 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 L of the longer side 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 range was calculated. Condition: 0.1 (μm) ≤ L ａ

[0107] <Evaluation Method of Cutting Performance of Coated Tools> The cutting performance of 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, and 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) every 1m of cutting length, 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 100 μm.

[0108] 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 the 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 Examples 1-2 exceeded 100 μm, measured using the same manufacturing lot of the 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 the cutting tool and workpiece of the coated tool in Comparative Examples 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) Machining method: Side cutting Rotation speed: 2100 min －１ Feed rate: 250 mm / min Cutting depth (a p ×a e Dimensions: 9mm x 0.3mm Cutting fluid: Water-soluble cutting fluid 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)

[0109] <Method for Manufacturing Coated Tools> Next, the details of the method for manufacturing coated tools for Examples 1-1 to 1-13 and Comparative Examples 1-1 to 1-6 are described below.

[0110] (Example 1-1) In Example 1-1, a hard coating was formed on a tool for cutting difficult-to-machine materials using an arc ion plating apparatus equipped with a permanent magnet 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.

[0111] 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.

[0112] First, the cutting tool for difficult-to-machine materials, which serves as the base material, 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 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 below Pa.

[0113] 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.

[0114] 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 an image similar to the image 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 50 atomic% Al content, 40 atomic% Ti content, and 10 atomic% Si content 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.

[0115] (Example 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 of Example 1-2, and the cutting performance of the coated tool was also evaluated. These results are summarized in Table 1 below.

[0116] (Examples 1-3) In Example 1-3, a coated tool was manufactured in the same manner as in Example 1-2, except that a target with a composition of 70 atomic% Al content, 20 atomic% Ti content, and 10 atomic% Si content 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 tool of Example 1-3, and the cutting performance of the coated tool was also evaluated. These results are summarized in Table 1 below.

[0117] (Examples 1-4 to 1-13) In Example 1-4, etching was performed using a combination of argon bombardment 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 a coated tool in the same manner as in Example 1-1.

[0118] 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.

[0119] 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, a coated tool was manufactured in the same manner as in Example 1-4, except that a target having a composition of 60 atomic percent Al, 37 atomic percent Ti, and 3 atomic percent Nb was used.

[0120] 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.

[0121] (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.

[0122] (Comparative Example 1-2) In Comparative Example 1-2, a coated tool was manufactured in the same manner as in Comparative Example 1-1, except that a target with a composition of Al content of 70 atomic%, Ti content of 20 atomic%, and Si content of 10 atomic% was used. Similar to Example 1-1, the composition of metallic and metalloid elements in the hard coating and the number of droplets of the coated tool of Comparative Example 1-2 were measured and calculated, and the cutting performance of the coated tool was also evaluated. These results are summarized in Table 1 below.

[0123] (Comparative Examples 1-3 to 1-6) In Comparative Example 1-3, a coated tool was 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, a coated tool was 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, a coated tool was 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, a coated tool was 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.

[0124] 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.

[0125]

[0126] <Discussion> 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 ２It was found that when the number of droplets within a given range is 50 or less, the coated tool with the hard coating has excellent wear resistance for machining difficult-to-cut materials. Furthermore, it was found that the number of droplets in the cross-section of such a hard coating is easily achieved by the arc ion plating method, but it also varies depending on the composition of the target (or the composition of metallic and metalloid elements contained in the final hard coating), the process conditions during film formation by the arc ion plating method, etc. It should be noted that Comparative Examples 1-3 to 1-6, for which tool life performance evaluation was not performed, have a large number of droplets within the given range, and are therefore expected to have poor wear resistance for machining difficult-to-cut materials.

[0127] 2. Observation of the microstructure of the cross-section of the hard coating by STEM and line analysis of the microstructure of the said cross-section by EDX In Example 2-1 and Comparative Example 2-1, a hard coating having a predetermined composition of metallic and metalloid elements was formed on a test specimen by arc ion plating or HiPIMS, and coated test specimens were manufactured. Subsequently, the microstructure of the cross-section of the hard coating was observed by STEM. Furthermore, line analysis of the microstructure of the said cross-section was performed by EDX.

[0128] Details of the test specimens used, the method for observing the microstructure of the cross-section of the hard coating using STEM, and the line analysis method using EDX are as follows.

[0129] <Test Specimen> A test specimen made of cemented carbide, with dimensions of 1.3 cm x 1.3 cm x 0.5 cm (thickness), was used as the base material.

[0130] <Method for Observing the Structure of the Cross-Section of a Hard Coating Using STEM> To observe the cross-sectional structure of the hard coating of the manufactured coated test specimen, a thin film was applied to the coated test specimen using a focused ion beam (FIB) ("FB2200", manufactured by Hitachi High-Technologies Corporation) to a size of 10 μm × 18 μm × 100 nm (thickness). Subsequently, a dark-field image of the structure of the cross-section parallel to the plane along the film thickness direction, near 1 μm from the outermost surface of the hard coating, was obtained using a STEM ("JEM-2100F", manufactured by JEOL Ltd.). The magnification of the STEM was set to 1.5 million times in Example 2-1 and to 1 million times in Comparative Example 2-1.

[0131] <Line Analysis by EDX> Line analysis was performed on dark-field images observed by STEM of the cross-section of the hard coating using an energy-dispersive X-ray spectrometer (EDX) ("JED-2300T", manufactured by JEOL Ltd.) under the following analysis conditions. (Analysis conditions) Electron beam acceleration voltage: 200 kV Number of measurement points: 50 points Integration time per point: 20 seconds

[0132] <Method for Manufacturing Coated Tools> Next, the details of the method for manufacturing the coated test specimens of Example 2-1 and Comparative Example 2-1 are described below.

[0133] (Example 2-1) In Example 2-1, the coated test piece was manufactured in the same manner as in Example 1-1, except that the test piece described above was used as the base material instead of a tool for cutting difficult-to-machine materials.

[0134] The microstructure of the cross-section of the hard coating of the coated test specimen of Example 2-1, which was manufactured in this manner, was observed and analyzed using the method described above.

[0135] (Comparative Example 2-1) In Comparative Example 2-1, the same test specimen as in Example 2-1 was used as the base material, and a hard coating was formed by the HiPIMS method to produce a coated test specimen.

[0136] Specifically, using a general HiPIMS deposition apparatus (manufactured by Hauzer), sputtering power (average power 8 kW, pulse width 1500 μs) 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 2.55 μm was obtained by sputtering the target metal.

[0137] The coated test specimens prepared in this manner were observed and analyzed in the same manner as in Example 2-1, using the method described above to examine the microstructure of the cross-section of the hard coating.

[0138] <Discussion> 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 observed by STEM showed a striped structure in which black layers, shown relatively in black, and white layers, shown relatively in white, are repeated on a scale 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 a setting of 1,000,000x and magnified 1.5 times 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.

[0139] Figure 5 shows the results of EDX line analysis of dark-field images observed by STEM as 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 content of the metallic components Al and Ti 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 content of the metallic components Al and Ti was relatively decreased. On the other hand, in areas where the nitrogen content in the coating was relatively decreased (white layer), the content of Al and Ti was relatively increased.

[0140] 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.

[0141] 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 the metal components Al and Ti along the film thickness depth direction to show opposite changes in terms of 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 the 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 the ions of the metal components to circulate within the apparatus and form a film.

[0142] 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 film formed by arc ion plating exhibits higher adhesion at the interface with the substrate. Therefore, it is expected that coated tools with excellent wear resistance can be obtained for machining difficult-to-cut materials.

[0143] 3. Formation of hard coatings of other configurations 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 including a first hard coating and a second hard coating was formed on the tool for cutting difficult-to-machine materials.

[0144] <Method of manufacturing coated tools> Details of the method of manufacturing coated tools in Examples 3-1 to 3-8 are described below.

[0145] (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 apparatus as the arc ion plating apparatus used in Examples 1-1 to 1-13, thereby manufacturing a coated tool.

[0146] First, the cutting tool for difficult-to-machine materials, which serves as the base material, 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 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 below Pa.

[0147] 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.

[0148] 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.

[0149] 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 having 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.

[0150] 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. The conditions for depositing the first hard film were a bias voltage of -120V and an arc current of 150A. The conditions for depositing the second hard film were a bias voltage of -50V initially, which was then changed to -65V, and an arc current of 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.

[0151] (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%.

[0152] 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.

[0153] 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.

[0154] <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 and second hard coatings is measured. Therefore, the composition of metallic and metalloid elements of only the second hard coating 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 coating (see Table 1 above), the converted value of the composition of only the first hard coating in the laminated film was calculated, and the converted value of the composition of the second hard coating was calculated by subtracting the converted value of the composition of only the first hard coating from the composition of the laminated film.

[0155] 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 calculation 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 Example 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 = approximately 73.83 atomic % Si: [(c2) / ((b2) + (c2))] × 100 = approximately 26.17 atomic %

[0156] 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.

[0157] Furthermore, for example, the composition (converted values ​​of composition) of the metallic and metalloid elements in the second hard coating of Example 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 film in Example 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 Example 3-5 (see Example 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 Example 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 of Example 3-5 Al + Nb: 16.92 - ((d1) + (e1)) = ((d2) + (e2)) (= 0 atomic %) 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=approximately 75.47 atomic% Si: [(g2)(=17.94) / ((f2)+(g2)(=17.94)]×100=approximately 24.53 atomic%

[0158] 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.

[0159] 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.

[0160]

[0161] <Discussion> 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 is 50 or less, received an "A" rating for tool life evaluation and possessed 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.

[0162] This application is based on Japanese Patent Application No. 2024-182577, filed on 18 October 2024, and Japanese Patent Application No. 2025-163704, filed on 30 September 2025, the contents of which are included in this application.

[0163] 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.

[0164] According to the embodiment of the present invention, the tool for cutting difficult-to-machine materials has excellent wear resistance and can be suitably used for cutting applications where the workpiece is a difficult-to-machine material such as a nickel-based alloy or a titanium alloy.

Claims

1. A cutting tool for difficult-to-machine materials, and a hard coating formed on at least a portion of the outer surface of the cutting tool for difficult-to-machine materials, wherein the hard coating comprises 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 A coated tool for cutting difficult-to-machine materials, wherein the number of droplets within a certain 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.

2. The hard coating is a hard coating containing a nitride mainly composed of Al and Ti, 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 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, according to claim 1.

3. The hard coating is a hard coating containing a nitride mainly composed of Al and Ti, 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, 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, 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, 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 Nb content is greater than 0 atomic%, and the total content of Al, Ti and Nb is 100 atomic%.

7. A tool for cutting difficult-to-machine materials, and a laminated film comprising 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, wherein the laminated film comprises a nitride of a metallic element or a nitride of a metallic element and a metalloid element, and the cross-section of the laminated film has a continuous 1000 μm ２ The number of droplets within a certain range is 50 or less, and 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 including a black layer shown relatively as black and a white layer shown relatively as white, and the first hard coating is a hard coating containing a nitride mainly composed of Al and Ti, and has the composition of the total amount of the metal elements and metalloid elements contained in the hard coating according to any one of claims 2 to 6, and the second hard coating is a hard coating containing a nitride mainly composed of Ti, and in the total amount of the metal elements and metalloid elements 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%, a coated tool for cutting difficult-to-machine materials.

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