Cutting tool having hard coating consisting of multiple sub-coatings

Abstract

The purpose of the present invention is to provide a cutting tool having a hard coating with excellent wear resistance and adhesion resistance even during heat resistant alloy processing. To this end, the cutting tool according to the present invention comprises: a hard base material; and a hard coating formed on the hard base material, wherein the hard coating includes a plurality of alternately laminated sub-coatings, the sub-coatings have a cubic crystal structure and comprise at least one metal element from among Zr, Nb, Hf, and Ta, and at least one of C, N, and O, an interplanar distance (111) may be 2.49 Å or more, and an interplanar distance (200) may be 2.16 Å or more.

Description

Cutting tool having a hard film composed of multiple sub-films

[0001] This invention was supported by the National Research and Development Program.

[0002] [Project ID] 1415182096

[0003] [Assignment Number] P0021347

[0004] Ministry of Trade, Industry and Energy

[0005] [Name of Project Management (Specialist) Institution] Korea Institute for Advancement of Technology

[0006] [Research Project Name] Mid-Sized Enterprise DNA Convergence Industry-Academic Cooperation Project

[0007] [Research Project Name] Establishment and Demonstration of an Integrated Database for the Development of PVD Thin Films for Machining High-Hardness, Difficult-to-Machine Components

[0008] The present invention relates to a cutting tool including a hard base material and a hard film formed on the hard base material, and more particularly, to a cutting tool in which the hard film has a cubic crystal structure and a structure in which a plurality of sub-films having an interplanar distance greater than a predetermined distance are alternately laminated.

[0009] When machining heat-resistant alloys using cutting tools, the strong cutting resistance and high cutting temperature cause the chips to repeatedly adhere to and detach from the tool edge, which causes the hard film to be torn off, and in severe cases, damage may occur to the surface of the hard base material.

[0010] As a result, the hard film is rapidly removed by wear, damaging the surface of the hard substrate, and significantly reducing tool life when machining heat-resistant alloys compared to general metal materials. To address this issue, various methods have been employed to improve the adhesion and lubricity of the hard film, but these methods are still insufficient to suppress the aforementioned wear mechanism.

[0011] The purpose of the present invention is to provide a cutting tool having a hard film with excellent wear resistance and welding resistance even when processing a heat-resistant alloy.

[0012] In order to achieve the above purpose, a cutting tool for cutting an Fe-based or Ni-based heat-resistant alloy according to the present invention includes a hard base material and a hard film formed on the hard base material, the hard film includes a plurality of alternately laminated sub-films, the sub-films have a cubic crystal structure and include at least one metal element selected from Zr, Nb, Hf, and Ta, and at least one or more of C, N, and O, and the (111) interplanar distance may be 2.49 Å or more, and the (200) interplanar distance may be 2.16 Å or more.

[0013] Additionally, in a cutting tool according to one embodiment of the present invention, the residual stress formed in the sub-film may be in the range of -1.5 to 0 GPa.

[0014] Additionally, in a cutting tool according to one embodiment of the present invention, the difference between the (111) interplanar distance and the (200) interplanar distance between adjacent sub-films among the plurality of sub-films may be 0.03 Å or more, respectively.

[0015] Additionally, in a cutting tool according to one embodiment of the present invention, the residual stress difference between adjacent sub-films among the plurality of sub-films may be 0.2 GPa or more.

[0016] Additionally, in a cutting tool according to one embodiment of the present invention, the sub-film may be a nitride containing one or more of the metal elements.

[0017] Additionally, in a cutting tool according to one embodiment of the present invention, the hard film may be formed by alternately laminating two or more sub-films made of nitrides having different compositions.

[0018] In addition, in a cutting tool according to one embodiment of the present invention, the hard film may be formed by alternately stacking the sub-film formed of a nitride of a single metal element among the metal elements and the sub-film formed of a nitride of two or more metal elements among the metal elements.

[0019] In addition, in a cutting tool according to one embodiment of the present invention, the hard film may be sequentially alternately laminated with the sub-film formed of a nitride of a single metal element among the metal elements, the sub-film formed of a nitride containing two metal elements among the metal elements, and the sub-film formed of a nitride containing three metal elements among the metal elements.

[0020] In addition, in a cutting tool according to one embodiment of the present invention, the hard film may be alternately laminated with the sub-film formed of a nitride containing one or two of the metal elements and the sub-film formed of a nitride containing three of the metal elements.

[0021] In addition, in a cutting tool according to one embodiment of the present invention, at least one layer of a compound layer selected from carbides, nitrides, oxides, carbonitrides, oxynitrides, oxycarbides, oxycarbonitrides, borides, boron nitrides, boron carbonitrides, boron oxynitrides, boron oxocarbides, boron oxocarbonitrides, and boron oxonitrides, including at least one element selected from the group consisting of Ti, Al, Cr, Ta, Hf, Nb, Zr, V, Y, W, Mo, Si, and B, may be formed on the lower portion of the hard film formed of two or more alternately laminated sub-films.

[0022] Additionally, in a cutting tool according to one embodiment of the present invention, the sub-film thickness may be in the range of 50 to 500 nm, and the thickness of the hard film may be in the range of 0.1 to 5 μm.

[0023] Additionally, in a cutting tool according to one embodiment of the present invention, the sub-film may not include Al, Cr, V, Y, and Si.

[0024] According to the present invention, it is possible to provide a cutting tool having excellent wear resistance and service life for processing heat-resistant alloys.

[0025] FIG. 1 is a conceptual diagram showing a cross-section of a cutting tool including a hard film according to one embodiment of the present invention.

[0026] FIG. 2 is a conceptual diagram showing a cross-section of a cutting tool including a hard film according to one embodiment of the present invention.

[0027] Figure 3 is an image of the wear track after the wear test.

[0028] Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0029] In addition, in order to clearly explain the invention in the drawings, parts unrelated to the explanation were omitted, and similar parts were given similar drawing symbols throughout the specification.

[0030] Throughout this specification, when it is said that a member is located “on,” “above,” “upper,” “lower,” “lower” or “lower” another member, this includes not only cases where the member is in contact with the other member, but also cases where another member exists between the two members.

[0031] Throughout this specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0032] The terms "about," "substantially," and the like, as used herein, are used to mean at or near the numerical value when manufacturing and material tolerances inherent to the meanings referred to are presented, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that contain precise or absolute numerical values ​​to aid understanding of the present disclosure. Furthermore, throughout the present disclosure, the terms "step of ~" or "step of ~" do not mean "step for ~."

[0033] Throughout this specification, the term "combination thereof" included in the expressions in the Makushi format means one or more mixtures or combinations selected from the group consisting of the components described in the expressions in the Makushi format, and means including one or more selected from the group consisting of said components.

[0034] Throughout this specification, references to “A and / or B” mean “A or B, or A and B.”

[0035] A cutting tool for cutting an Fe-based or Ni-based heat-resistant alloy according to the present invention comprises a hard base material and a hard film formed on the hard base material, wherein the hard film comprises a plurality of alternately laminated sub-films, wherein the sub-films have a cubic crystal structure and include at least one metal element selected from Zr, Nb, Hf, and Ta, and at least one metal element selected from C, N, and O, and are characterized in that the (111) interplanar distance is 2.49 Å or more and the (200) interplanar distance is 2.16 Å or more.

[0036] The hard film according to the present invention, rather than suppressing the wear mechanism itself during the processing of heat-resistant alloys, sequentially peels off from the outermost layer of the hard film when the process of chip adhesion and peeling occurs, and prevents cracks from rapidly propagating to the inner layer of the hard film and the surface of the hard base material, thereby preventing peeling off of the entire hard film and damage to the surface of the hard base material.

[0037] The adhesion between the workpiece and the cutting tool becomes more severe as the difference in the interplanar distance between the base of the workpiece and the hard film formed on the surface of the cutting tool becomes smaller. The hard film according to the present invention is characterized in that the interplanar distance is made to be significantly different from the interplanar distance of an Fe-based or Ni-based heat-resistant alloy, thereby allowing the hard film to be slowly removed only by frictional resistance as much as possible. In addition, the hard film is composed of a plurality of alternately laminated sub-films, so that the sub-films are peeled off one by one, and the boundary between the sub-films acts as a barrier to crack propagation, thereby slowing down the rate of film peeling off and inducing uniform wear.

[0038] These sub-films are nitrides, oxides, borides, carbides, or combinations thereof, which have a cubic crystal structure and contain at least one metallic element selected from Zr, Nb, Hf, and Ta, and at least one element selected from C, N, and O. The sub-films made of these materials have a cubic crystal structure with excellent wear resistance, and the interplanar distances of the major planes are different from those of the heat-resistant alloy.

[0039] Additionally, the sub-film may not contain Al, Cr, V, Y and Si, as materials with cubic crystal structures containing these elements have difficulty maintaining interplanar spacing effectively.

[0040] Meanwhile, when the outer sub-film falls off, the sub-film right below it can fall off along with it, and this can easily happen if the difference in the interplanar distance between the sub-films is not large. Therefore, in the hard film of the cutting tool according to the present invention, the difference in the interplanar distance between the main surfaces (111) and (200) planes between the sub-films is set to be 0.03 Å or more, thereby preventing damage to the sub-film below as the sub-film exposed on the outer surface is removed.

[0041] Additionally, the residual stress formed in the sub-film can range from -1.5 to 0 GPa. Excessively high compressive stress results in excellent impact resistance, but tends to separate from the surrounding material when torn. Tensile stress, on the other hand, reduces impact resistance and makes cracks easily occur during processing. Maintaining this optimal range of compressive residual stress reduces the phenomenon of biting and separation within the same sub-film while simultaneously maintaining excellent impact resistance.

[0042] In this way, the hard film according to the present invention sacrificially and stably consumes a plurality of included sub-films, thereby preventing crack propagation and accompanying peeling not only between sub-films (Z-axis) but also within the sub-films (X, Y-axis). Therefore, the present invention can provide a cutting tool having a sacrificial type and a three-dimensional crack propagation-inhibiting hard film formed on the surface, which is optimized for machining heat-resistant alloys.

[0043] Meanwhile, in the cutting tool according to the present invention, the hard film may have a structure in which two or more sub-films made of nitrides having different compositions are alternately laminated.

[0044] Nitride is suitable for stably implementing the interplanar distance difference with the above-mentioned heat-resistant alloy and the interplanar distance difference between sub-films.

[0045] The sub-film of the nitride may be a nitride containing one, two or three of the above-mentioned metal elements, specifically, the nitride containing a single metal element may be any one of ZrN, NbN, TaN or HfN, and the nitride containing two metal elements may be Zr x Nb 1-x N, Zr x Hf 1-x N, Zr x Ta 1-x N, Nb x Hf 1-x N, Nb x Ta 1-x N or Hf x Ta 1-xN(0 in chemical formula) <x<1임)중 어느 하나일 수 있으며, 세 개의 금속 원소를 포함하는 질화물은 Zr a Nb b Hf 1-a-b N, Zr a Nb b Ta 1-a-b N or Nb a Hf b Ta 1-a-b N(0 in chemical formula) <a<1, 0<b<1, a+b<1 임) 중 어느 하나일 수 있다.

[0046] By making the metal element composition of the nitride included between the sub-films different, the difference in the interplanar distance between the sub-films can be maintained. To this end, the plurality of sub-films may be formed of nitrides containing a single metal element, but may contain different metal elements. In one embodiment of the present invention, the hard film may have a structure in which sub-films of ZrN and sub-films of NbN are alternately laminated.

[0047] Additionally, sub-films of nitrides containing two metal elements may be alternately laminated, and sub-films of nitrides containing three metal elements may be alternately laminated.

[0048] According to one embodiment of the present invention, a hard film structure may be a structure in which a sub-film formed of a nitride of a single metal element among the above metal elements and a sub-film formed of a nitride of two or more metal elements among the above metal elements are alternately laminated. By controlling the number of these metal elements, the interplanar distance between the sub-films can be controlled.

[0049] In addition, a hard film structure according to one embodiment of the present invention may sequentially and alternately laminate a sub-film formed of a nitride of a single metal element among the metal elements, a sub-film formed of a nitride of two metal elements among the metal elements, and a sub-film formed of a nitride of three metal elements among the metal elements. By gradually increasing the number of metal elements included in the sub-film, the difference in interplanar distance is controlled.

[0050] In addition, a hard film structure according to one embodiment of the present invention may be formed by sequentially and alternately stacking the sub-films formed of nitrides of one or two of the metal elements and the sub-films formed of nitrides of three of the metal elements. Similarly, by varying the number of metal elements included in the alternately stacked sub-films, the difference in interplanar spacing is controlled.

[0051] In addition, the hard film structure according to one embodiment of the present invention may have at least one layer of a compound selected from carbides, nitrides, oxides, carbonitrides, oxynitrides, oxycarbonides, oxycarbonitrides, borides, boron nitrides, boron carbonides, boron carbonitrides, boron oxynitrides, boron oxocarbides, boron oxocarbonitrides, and boron oxonitrides, which contain at least one element selected from the group consisting of Ti, Al, Cr, Ta, Hf, Nb, Zr, V, Y, W, Mo, Si, and B. Through structural combination with other materials, insufficient performance can be improved and supplemented.

[0052] Meanwhile, the hard film of the cutting tool according to the present invention may have a sub-film thickness in the range of 50 to 500 nm and a total hard film thickness of 0.1 to 10 μm.

[0053] The thickness of the entire hard film must be above a certain level to maintain the required wear resistance. However, if it is too thick, it may become delaminated due to internal stress, which is undesirable. Therefore, a thickness in the range of 0.1 to 10 μm is preferable.

[0054] Meanwhile, the thickness of the sub-film is preferably in the range of 50 to 500 nm for removal by gradual wear.

[0055] Figure 1 illustrates a structure of a hard film (20) in which a plurality of sub-films (21, 22) containing different metal element compositions are alternately laminated on the surface of a hard base material (10). The sub-film (21) may be formed of a nitride containing one metal element, and the sub-film (22) may be formed of a nitride containing one, two, or three metal elements.

[0056] Meanwhile, Fig. 2 illustrates a structure of a hard film (20) in which a plurality of sub-films (23, 24, 25) containing different metal element compositions are alternately laminated on the surface of a hard base material (10). The sub-film (23) may be a nitride containing one metal element, the sub-film (24) may be a nitride containing two metal elements, and the sub-film (25) may be a nitride containing three metal elements.

[0057]

[0058] [Example]

[0059] Manufacturing of hard films

[0060] In an embodiment of the present invention, a film having a structure as shown in FIG. 1 or FIG. 2 was formed on a hard base material surface made of a superalloy using arc ion plating, which is a physical vapor deposition (PVD) method.

[0061] After the base material was wet microblasted and washed with ultrapure water, it was mounted along the circumference at a predetermined radial distance from the center axis on the rotary table in a dry state in the coating furnace. The initial vacuum pressure in the coating furnace was 8.5ⅹ10 -5 The pressure was reduced to below 10 Torr, the temperature was heated to 400 to 600°C, and then a pulse bias voltage of -300 to -200 V was applied to the rotating base material on the rotary table under an Ar gas atmosphere to perform ion bombardment for 30 to 60 minutes. The gas pressure for coating was maintained at 50 mTorr or less or 40 mTorr or less, and the substrate bias voltage during coating was applied at -100 to -20 V.

[0062] More specifically, the base material used was a cemented carbide composed of WC with an average particle size of 2 ㎛ and a Co content of 12 wt.%. During coating, the target was a combination of arc targets composed of single metal elements of Zr, Nb, Hf, and Ta, arranged on 2 to 4 sides inside the coating furnace, and the film was formed under the conditions of a bias voltage of -60 to -30 V, an arc current of 75 to 150 A, N2 injected as a reaction gas, and a pressure of 10 to 30 mTorr. The coating conditions may vary depending on the equipment characteristics and conditions. Here, an AlTi arc target was additionally used to form a separate lower layer on the hard film according to the present invention.

[0063] Examples and comparative examples of the present invention were manufactured under the above conditions, and information on the structure and composition of the corresponding hard film, (111) interplanar distance, (200) interplanar distance, residual stress, lamination cycle, number of laminations, and total thickness are shown in Table 1 below.

[0064] Structure and composition of the hard film (111) Interplanar distance (Å) (200) Interplanar distance (Å) Residual stress (GPa) Lamination cycle (㎛) Number of laminations (times) Total thickness (㎛) Example 1 ZrN / NbN 2.5 9 2.24-0.7 0.35 1.5 Example 2 ZrN / TaN 2.5 7 2.22-0.8 0.5 3 1.5 Example 3 ZrN / TaN 2.5 7 2.22-0.6 0.35 1.5 Example 4 ZrN / TaN 2.5 7 2.22-0.6 0.27 1.4 Example 5 Zr x Nb 1-x N / Zr x Ta 1-x N(x=0.5)2.582.23-0.70.351.5Example 6Zr a Nb b Hf 1-a-b N / Zr a Nb b Ta 1-a-b N(a=0.4, b=0.3)2.582.24-0.90.351.5Example 7ZrN / Zr x Ta 1-x N(x=0.5)2.602.25-0.80.351.5Example 8ZrN / Zr a Hf b Ta 1-a-b N(a=0.4, b=0.3)2.612.26-1.00.351.5Example 9ZrN / Zr x Ta 1-x N / Zr a Hf b Ta 1-a-b N(x=0.5, a=0.4, b=0.3)2.602.25-1.10.351.5Example 10AlTiN(lower layer, Al:Ti=6:4)+ZrN / TaN2.40+2.572.09+2.22-1.30.353.5Comparative Example 1TiN2.452.12-1.4--1.5Comparative Example 2ZrN2.642.29-1.2--1.5Comparative Example 3Zr x Nb 1-x N(x=0.5)2.592.24-1.1--1.5Comparative Example 4Zr a Nb b Hf 1-a-bN(a=0.4, b=0.3)2.602.25-1.6--1.5Comparative Example 5AlTiN(Al:Ti=6:4)2.402.09-1.6--3.5Comparative Example 6AlTiN(lower layer, Al:Ti=6:4)+ZrN2.40+2.642.09+2.29-1.5--3.5

[0065] The interplanar distances of the examples shown in Table 1 above are values ​​for the entire hard film, and the (111) interplanar distance of each sub-film is 2.49Å or more, and the (200) interplanar distance is 2.16Å or more. Each interplanar distance can range up to about 0.2Å depending on the composition and coating conditions, and the film was formed so that the interplanar distance difference between adjacent sub-films was 0.03Å or more. The residual stress of the examples is also a value for the entire hard film, and the residual stress of each sub-film is -1.5 to 0GPa, and can be controlled over a wide range depending on the composition and coating conditions. The film was formed so that the residual stress difference between adjacent sub-films was 0.2GPa or more. The examples were set to a lamination cycle of 0.3㎛, a lamination count of 5, and a thickness of 1.4 to 1.5㎛ as basic settings, and examples 2 and 4 were formed with different lamination cycles and counts. In Example 10, an AlTiN lower layer with a thickness of about 2 μm was deposited, and then Example 1 was deposited as an upper layer. In Comparative Example, a single layer was deposited without multiple alternately laminated sub-films, and in Comparative Example 6, an AlTiN lower layer with a thickness of about 2 μm was deposited, and then Comparative Example 2 was deposited as an upper layer.

[0066]

[0067] Wear test evaluation

[0068] In order to evaluate the tear resistance of the hard films manufactured as shown in Table 1 above, Example 1 and Comparative Examples 1 and 2, a ball-on-disk wear test was performed, and the evaluation was conducted under the following conditions.

[0069] (1) Ball-on-disk wear test

[0070] Disc: Hard base material and hard film of the present invention

[0071] Ball: STS304 (6mm diameter)

[0072] Load: 10N

[0073] Speed: 100 / min

[0074] Time: 5 min

[0075] Because ball-on-disk wear testing is performed at lower speeds than cutting operations, the disc, composed of a hard substrate and a hard coating, wears very slowly, while the low-hardness stainless steel ball wears rapidly. Wear debris from the stainless steel ball is generated, and friction causes repeated attachment and detachment of the debris, tearing the hard coating.

[0076] Fig. 3 is an image of the wear track after the wear test, and as can be seen here, the result of Example 1 (Fig. 3(a)) has fewer torn hard films and a smaller area than Comparative Example 1 (Fig. 3(b)) and Comparative Example 2 (Fig. 3(c)). Among Fe-based and Ni-based metal materials, materials having an FCC crystal structure as a matrix structure have a (111) interplanar distance of 2.05 to 2.08 Å, which is very close to the (200) interplanar distance of 2.06 to 2.09 Å of a film having a composition based on the TiAlN, AlTiN, and AlCrN series among hard films coated by a physical vapor deposition method. In an environment where frictional wear occurs between a hard film and a metal, metal wear debris can be physically deformed, adhered, and bonded to the hard film, and there is a tendency for crystal planes with similar interplanar distances to preferentially bond together (facilitate dislocation movement). Therefore, Example 1 and Comparative Example 2 have a large interplanar distance compared to the base structure of the stainless steel compared to Comparative Example 1, so that less attachment and bonding with metal wear debris occurs, and the tear-off property is excellent. On the other hand, the reason why Example 1 has a better tear-off property despite Comparative Example 2 having a large interplanar distance is that when metal wear debris adheres to and falls off the hard film, the boundary between the sub-films (mismatch, difference in interplanar distance) acts as a barrier to crack propagation, thereby slowing down the rate of film detachment and inducing uniform wear.

[0077] Cutting performance evaluation

[0078] In order to evaluate the adhesion and tear resistance of the hard film manufactured as shown in Table 1 above, a milling test was performed and the evaluation was conducted under the following conditions.

[0079] (1) Evaluation of austenitic stainless steel

[0080] Workpiece material: STS316

[0081] Sample Model Number: SNMX1206ANN-MF

[0082] Cutting speed: 90 m / min

[0083] Cutting feed: 0.15mm / tooth

[0084] Axial cutting depth: 1.5 mm

[0085] Radial cutting depth: 50mm

[0086] When machining austenitic stainless steel at low speeds, welding and tearing generally occur frequently, which later leads to cracking and chipping. Therefore, the welding resistance, tearing resistance, heat crack resistance, and chipping resistance of the hard film have a significant impact on the cutting performance.

[0087] (2) Evaluation of Ni-based heat-resistant alloys

[0088] Workpiece material: INCONEL718

[0089] Sample Model Number: ADKT170608PESR-ML

[0090] Cutting speed: 35 m / min

[0091] Cutting feed: 0.2mm / tooth

[0092] Axial cutting depth: 5mm

[0093] Radial cutting depth: 3mm

[0094] When machining Ni-based heat-resistant alloys, adhesion and tearing occur frequently from the beginning, and subsequently, wear and chipping rapidly develop, so the adhesion resistance, tearing resistance, wear resistance, and chipping resistance of the hard film have a significant impact on cutting performance.

[0095] NumberSTS316 Machining ResultINCONEL718 Machining ResultMachine Length (mm)Wear TypeMachine Length (mm)Wear Type Example 13300 Normal wear 800 Excessive wear Example 23000 Normal wear 1200 Excessive wear Example 33600 Normal wear 1000 Excessive wear Example 43600 Normal wear 1000 Excessive wear Example 52700 Normal wear 1800 Normal wear Example 62100 Normal wear 2000 Normal wear Example 73000 Normal wear 1800 Normal wear Example 82400 Normal wear 2000 Normal wear Example 92700 Normal wear 2000 Normal wear Example 102400 Normal wear 2400 Normal wear Comparative example 11200 Tearing, heat crack, chipping 600 Tearing, excessive wear Comparative example 21500 Tearing, 600 degrees of cracking, 31,800 degrees of tearing compared to excessive wear, 1,000 degrees of cracking, 41,200 degrees of tearing compared to excessive wear, 800 degrees of chipping, 5900 degrees of tearing compared to chipping, 1400 degrees of tearing compared to chipping, 6900 degrees of tearing compared to chipping, 1600 degrees of tearing compared to chipping, chipping

[0096] As confirmed in Table 3 above, the hard films of the examples have generally superior cutting performance compared to the hard films of the comparative examples. This is because the examples have a larger interplanar distance than the comparative examples, lower compressive residual stress, or a structure in which the sub-films are alternately laminated. Even if the interplanar distance and residual stress between the hard films are similar, the cutting performance may differ greatly depending on the composition, structure, and workpiece of the hard films. Examples 1 to 4 have a nitride sub-film containing one metal element, so the hardness of the film is low and the compressive residual stress is low, resulting in excellent tear resistance in stainless steel machining and low wear resistance in Inconel machining. Examples 5 to 9 have a nitride sub-film containing one, two, or three metal elements, so the hardness of the film is high due to the solid solution strengthening effect and the compressive residual stress is high, resulting in slightly lower tear resistance in stainless steel machining and excellent wear resistance in Inconel machining compared to Examples 1 to 4. Example 10 uses AlTiN, which has excellent wear resistance and chipping resistance, as a lower layer, and Example 1 as an upper layer, so that it can have good cutting performance in both Fe-based and Ni-based metal materials having an FCC crystal structure as a base structure. Therefore, the hard film according to the present invention sacrificially and stably consumes a plurality of included sub-films, while preventing crack propagation and accompanying peeling not only between sub-films (Z-axis) but also within the sub-films (X, Y-axis). Therefore, the present invention can provide a cutting tool having a sacrificial type and a three-dimensional crack propagation-inhibiting hard film formed on the surface, which is optimized for machining heat-resistant alloys, and can be applied in a wider variety of ways through combination with the lower layer.

Claims

1. Includes a hard base material and a hard film formed on the hard base material, The above hard film comprises a plurality of alternately laminated sub-films, The above sub-film is, It has a cubic crystal structure and contains at least one metallic element among Zr, Nb, Hf, and Ta, and contains at least one of C, N, and O. A cutting tool having a (111) interplanar distance of 2.49Å or more and a (200) interplanar distance of 2.16Å or more.

2. In paragraph 1, A cutting tool in which the residual stress formed in the above sub-film is in the range of -1.5 to 0 GPa.

3. In paragraph 1, A cutting tool, wherein the difference between the (111) interplanar distance and the (200) interplanar distance between adjacent sub-films among the above multiple sub-films is each 0.03 Å or more.

4. In paragraph 1, A cutting tool, wherein the difference in residual stress between adjacent sub-films among the above multiple sub-films is 0.2 GPa or more.

5. In paragraph 1, A cutting tool, wherein the above sub-film is a nitride containing one or more of the above metal elements.

6. In paragraph 1, A cutting tool in which the above hard film is formed by alternately laminating two or more sub-films made of nitrides having different compositions.

7. In paragraph 6, The above hard film is a cutting tool in which the sub-film formed of a nitride of a single metal element among the above metal elements and the sub-film formed of a nitride of two or more metal elements among the above metal elements are alternately laminated.

8. In paragraph 6, A cutting tool in which the hard film is formed by sequentially and alternately laminating a sub-film formed of a nitride of a single metal element among the metal elements, a sub-film formed of a nitride containing two metal elements among the metal elements, and a sub-film formed of a nitride containing three metal elements among the metal elements.

9. In paragraph 6, A cutting tool in which the hard film is formed by alternately laminating the sub-film made of a nitride containing one or two of the metal elements and the sub-film made of a nitride containing three of the metal elements.

10. In paragraph 6, A cutting tool, wherein at least one layer of a compound layer selected from carbides, nitrides, oxides, carbonitrides, oxynitrides, oxycarbides, oxycarbonitrides, borides, boron nitrides, boron carbonitrides, boron oxynitrides, boron oxocarbides, boron oxocarbonitrides, and boron oxonitrides is formed on the lower portion of the hard film, the compound layer containing at least one element selected from the group consisting of Ti, Al, Cr, Ta, Hf, Nb, Zr, V, Y, W, Mo, Si, and B.

11. In paragraph 1, A cutting tool wherein the above sub-film thickness is in the range of 50 to 500 nm and the above hard film thickness is 0.1 to 5 μm.

12. In paragraph 1, The above sub-film is a cutting tool that does not contain Al, Cr, V, Y and Si.

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