Hard coating for cutting tool

Abstract

The present invention relates to a hard coating for a cutting tool having low chemical reactivity with a workpiece at a high temperature, excellent heat shielding properties, and surface lubricity. The hard coating according to the present invention is formed on the surface of a hard substrate by a PVD method, wherein the hard coating includes an A layer, a B layer, a C layer, a D layer, and an E layer, which are sequentially stacked on the surface of the hard substrate, wherein the A layer is formed of Ti1-aMe1aCxNy (0.2≤a≤0.7, x+y=1, 0≤y≤1, Me1 is at least one selected from elements of Groups 3 to 16), the C layer is formed of Ti1-x-ySiyMe2xCwNz (0≤x≤0.4, 0.005≤y≤0.35, w+z=1, 0≤z≤1, and Me2 is at least one selected from Al, Cr, V, Zr, Nb, Mo, Hf, Ta, W, and Y), the E layer is formed of Cr1-xMe3xN (0.1≤x≤0.7, and Me3 is at least one selected from elements of Groups 3 to 16), the B layer includes an alternating repeating layer in which nanolayers composed of an A layer and a C layer having a thickness of 10 to 30 nm are alternately and repeatedly stacked twice or more, and the D layer includes an alternating repeating layer in which nanolayers composed of a C layer and an E layer having a thickness of 10 to 30 nm are alternately and repeatedly stacked twice or more.

Description

Hard coating for cutting tools

[0001] The present invention relates to a hard film for cutting tools formed on a hard substrate such as cemented carbide, cermet, or cBN, which has low chemical reactivity at high temperatures, excellent thermal barrier properties, and surface lubricity.

[0002]

[0003] As industry becomes increasingly precise, high-speed, and mass-produced, there is a demand for improved cutting performance and extended lifespan of cutting tools.

[0004] During cutting operations, high heat of approximately 900°C or higher is locally generated at the tip of the tool that comes into contact with the workpiece. If a hard coating with excellent oxidation resistance and wear resistance is formed on the cutting surface of the cutting tool, the life of the cutting tool can be significantly extended.

[0005] To this end, a multilayer hard film is formed on a base material such as cemented carbide, cermet, end mill, drill, etc., in which one or more layers of a material having properties such as wear resistance, oxidation resistance, or impact resistance, such as TiN, TiAlN, AlTiN, AlCrN, and Al2O3 are laminated.

[0006] However, as workpieces are becoming increasingly hard and difficult to machine, hard-to-machine materials such as titanium alloys like Ti-6Al-4V and nickel-based superalloys exhibit high hardness or strong heat resistance, leading to rapid wear of cutting tools and shortening tool life due to the high heat generated during machining. Furthermore, during the machining of hard-to-machine materials, repeated adsorption and detachment of the built-up edge occur, transferring heat from the chip to the coating and base material. This causes coating delamination and impairs the bonding strength with the base material, ultimately leading to the detachment of the edge; therefore, surface lubricity is crucial to suppress this adsorption and detachment.

[0007] Therefore, it is desirable for hard coatings for cutting tools used for machining difficult-to-machine materials to have low chemical reactivity with the workpiece in high-temperature environments, which are problematic during machining, as well as excellent thermal barrier properties, wear resistance, and good surface lubricity with the workpiece. To achieve these characteristics, hard coatings with various layered structures are being developed.

[0008]

[0009] The objective of the present invention is to provide a hard coating for a cutting tool that has low chemical reactivity with the workpiece at high temperatures, excellent thermal shielding properties, and surface lubricity along with high-temperature wear resistance, making it particularly suitable for machining difficult-to-machine materials such as titanium alloys and Inconel.

[0010]

[0011] To achieve the above objective, the present invention provides a hard coating for a cutting tool according to the following (1) to (5).

[0012] (1) A hard film formed by PVD method on the surface of a hard gas, wherein the hard film comprises layers A, B, C, D, and E that are sequentially stacked on the surface of the hard gas, and

[0013] The above A layer is Ti 1-a Me1 a C x N y It consists of (0.2≤a≤0.7, x+y=1, 0≤y≤1, Me1 being one or more elements selected from groups 3 to 16), and

[0014] The above C layer is Ti 1-x-y Si y Me2 x C w N z (0≤x≤0.4, 0.005≤y≤0.35, w+z=1, 0≤z≤1, Me2 is composed of one or more selected from Al, Cr, V, Zr, Nb, Mo, Hf, Ta, W, Y), and

[0015] The above E layer is Cr 1-x Me3x It is composed of N (0.1≤x≤0.7, where Me3 is one or more elements selected from groups 3 to 16), and

[0016] The above B layer comprises an alternating repeating layer in which a nanolayer composed of an A layer and a C layer, each having a thickness of 10 to 30 nm, is alternately stacked two or more times.

[0017] A hard coating for a cutting tool, wherein the above D layer comprises an alternating repeating layer in which a nanolayer consisting of a C layer and an E layer having a thickness of 10 to 30 nm is alternately stacked two or more times.

[0018] (2) In (1), the thickness ratio (T) of the E layer and the C layer is given. E / T C A hard coating for cutting tools having a value of 0.24 to 0.61.

[0019] (3) In (1) or (2), the hard coating for a cutting tool, wherein Me1, Me2 and Me3 contain Al.

[0020] (4) A hard coating for a cutting tool, wherein in any one of (1) to (3), the thickness of the B layer and the D layer is 300 nm or less.

[0021] (5) A hard coating for a cutting tool, wherein in any one of (1) to (4), the thickness of the hard coating is 0.5 to 9.0 μm.

[0022]

[0023] The hard coating for a cutting tool according to the present invention has a laminated structure comprising layers A, B, C, D, and E formed by the aforementioned composition, and includes layers B and D formed alternately and repeatedly, thereby having low chemical reactivity with the workpiece (especially titanium alloy) at high temperatures required for machining difficult-to-machine materials, excellent thermal shielding properties, and surface lubricity along with high-temperature wear resistance, thereby improving the life of the cutting tool for machining difficult-to-machine materials.

[0024] The effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description below.

[0025]

[0026] FIG. 1 is a schematic diagram of a laminated structure of a hard film according to one embodiment of the present invention.

[0027] Figure 2 shows the influence of the k value constituting the hard film when machining an Inconel alloy as a workpiece.

[0028] Figure 3 shows the influence of the k value constituting the hard film when machining a titanium alloy as a workpiece.

[0029]

[0030] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0031] In addition, to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification have been given similar reference numerals.

[0032] Throughout this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0033] Terms of degree used in this specification, such as “about,” “substantially,” etc., are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the stated meaning, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosure in which precise or absolute values ​​are mentioned to aid in understanding the invention.

[0034] Throughout this specification, the term “combination thereof” included in a Markush-style expression means one or more mixtures or combinations selected from the group consisting of components described in the Markush-style expression, and means including one or more selected from the group consisting of said components. Throughout this specification, the description “A and / or B” means “A or B, or A and B”.

[0035] The hard coating for a cutting tool according to the present invention comprises layers A, B, C, D, and E that are sequentially formed and laminated on the surface of a hard substrate through a PVD method, wherein layer A is Ti 1-a Me1 a C x N y It is composed of (0.2≤a≤0.7, x+y=1, 0≤y≤1, Me1 is one or more elements selected from groups 3 to 16), and the C layer is Ti 1-x-y Si y Me2 x C w N z It is composed of (0≤x≤0.4, 0.005≤y≤0.35, w+z=1, 0≤z≤1, Me2 is one or more selected from Al, Cr, V, Zr, Nb, Mo, Hf, Ta, W, Y), and the E layer is Cr 1-x Me3 xThe structure is characterized by being composed of N (0.1≤x≤0.7, Me3 being one or more selected from elements of groups 3 to 16), wherein the B layer comprises an alternating repeating layer in which a nanolayer consisting of an A layer and a C layer having a thickness of 10 to 30 nm is alternately stacked two or more times, and the D layer comprises an alternating repeating layer in which a nanolayer consisting of a C layer and an E layer having a thickness of 10 to 30 nm is alternately stacked two or more times.

[0036] The hard film according to the present invention is composed of a five-layer structure including layers A, B, C, D, and E having the composition as described above, and Ti in the intermediate layer (layer C). 1-x-y Si y Me2 x C w N z By providing a layer to impart thermal shielding properties, and by ensuring that the surface layer (E layer) in contact with the workpiece does not contain titanium but contains chromium, chemical reactivity with the workpiece is reduced and surface lubricity is increased, and by placing alternating repeating layers (B layer and D layer) between the A layer and the C layer and between the C layer and the E layer, overall excellent high-temperature wear resistance and high-temperature peel resistance are improved, thereby enabling overall excellent cutting performance when machining difficult-to-machine materials.

[0037] In the above hard film, the thickness ratio k(T of the E layer and the C layer) E / T C Maintaining ) to 0.24 to 0.61 is desirable for improving the machinability of Inconel alloys or titanium alloys, and a more desirable thickness ratio k(T of the E layer and C layer) is E / T C ) is 0.35 ~ 0.55.

[0038] In the above hard film, Me1, Me2, and Me3 may preferably include Al.

[0039] In the above hard film, the thickness of the B layer and the D layer is preferably 40 nm or more and 1000 nm or less. If it is less than 40 nm, the effect of maintaining the bonding strength of the B layer or the D layer is insufficient, and even if it exceeds 1000 nm, the adhesion does not increase, so it is preferable that it be 1000 nm or less, and more preferable that it be 500 nm or less.

[0040] If the thickness of the hard film is less than 0.5㎛, thermal shielding is not properly achieved, and if it exceeds 9.0㎛, peeling occurs, which is likely to reduce the tool life, so it is preferable that the thickness be 0.5 to 9.0㎛.

[0041]

[0042] [Example]

[0043] After applying a polishing process to a hard substrate made of cemented carbide through a microblast honing process or a diabrush honing process, a hard film was formed using an arc ion plating method, which is a physical vapor deposition (PVD) method.

[0044] In the polishing process performed before forming a hard film on a hard gas, a paste containing diamond particles of 1 to 5 μm size was used, and arc targets of TiAl, AlCr, TiAlSi, and AlCrSi were used as targets for coating the hard film.

[0045] After the hard gas undergoing the polishing process is washed with wet microblasting and ultrapure water and dried, it is mounted along the circumference at a position radially spaced from the central axis on a rotary table inside the coating furnace, and the initial vacuum pressure inside the coating furnace is 8.5 × 10⁻⁶ -5 The pressure was reduced to below Torr.

[0046] After heating to a temperature of 400 to 600°C, an Ar ion bombardment was performed for 30 to 90 minutes by applying a bias voltage of -400 to -200V under an Ar gas atmosphere to a hard gas rotating on the rotary table under an Ar gas atmosphere. At this time, the gas pressure was maintained at 50 mTorr or less, preferably 40 mTorr or less, to form a film.

[0047] Films were deposited using TiAl, AlCr, TiSi, and TiAlSi targets with a bias voltage of -100 to -30V, an arc current of 100 to 150A, and nitrogen (N2) as the reaction gas at a pressure of 20 to 40 mtorr, and the coating conditions may vary depending on the equipment characteristics and conditions.

[0048] Hard films according to the comparative examples and embodiments of the present invention were deposited under the above conditions; hard films with a thickness range of 4.1 to 4.5 μm were deposited in Comparative Examples 1 to 3 using target TiAl (composition ratio 50:50), AlCr (composition ratio 70:30), and TiAlSi (composition ratio 30:60:10), and hard films with a thickness range of 4.4 to 4.6 μm were deposited in Examples 1 to 11 using target TiAl (composition ratio 50:50), AlCr (composition ratio 70:30), and TiSi (composition ratio 80:20). The corresponding K value [thickness ratio of the E layer and the C layer (T E / T C The information is shown in Table 1 below.

[0049] Composition of each layer, thin film thickness (um) K [Ratio of thickness between E layer and C layer (T E / T CLayer A Layer C Layer E Comparative Example 1 AlCrN--4.1 - Comparative Example 2 TiAlN--4.2 - Comparative Example 3 AlTiSiN--4.5 - Example 1 TiAlNTiSiNAlCrN 4.50 Example 2 TiAlNTiSiNAlCrN 4.40.1 Example 3 TiAlNTiSiNAlCrN 4.50.2 Example 4 TiAlNTiSiNAlCrN 4.60.25 Example 5 TiAlNTi SiNAlCrN 4.50.3 Example 6 TiAlNTiSiNAlCrN 4.60.4 Example 7 TiAlNTiSiNAlCrN 4.60.5 Example 8 TiAlNTiSiNAlCrN 4.60.6 Example 9 TiAlNTiSiNAlCrN 4.50.7 Example 10 TiAlNTiSiNAlCrN 4.50.8 Example 11 TiAlNTiSiNAlCrN 4.50.9

[0050]

[0051] Cutting tools according to Examples 1 to 11 and Comparative Examples 1 to 3, in which a hard film was formed as described above, were subjected to machining tests on two types of difficult-to-machine materials under the following conditions.

[0052] 1) Ti alloy machining: VC50, VF 240, Φ12 diameter flat end mill, surface machining

[0053] - Machining with a 4-flute flat endmill

[0054] - Workpiece: Ti-6Al-4V alloy (Diameter: 300mm × 200mm × 100mm)

[0055] - Workpiece hardness: HRC 40 ~ 45

[0056] - Sample Model Number: SFE4120

[0057] - RPM: 1350 revolutions / min

[0058] - Cutting feed: 0.045 mm / tooth

[0059] - Cutting depth (axial): 15mm

[0060] - Cutting depth (radial): 6mm

[0061] - Cutting fluid: Use

[0062] 2) Inconel Machining: VC40, VF 170, Φ12 diameter flat end mill, surface machining

[0063] - Machining with a 5-flute flat endmill

[0064] - Workpiece: INCONEL718 (Diameter: 300mm × 200mm × 100mm)

[0065] - Workpiece Hardness: HRC40 ~ 45

[0066] - Sample Model Number: SFES5120

[0067] - RPM: 1050 revolutions / min

[0068] - Cutting feed: 0.04 mm / tooth

[0069] - Cutting depth (axial): 12mm

[0070] - Cutting depth (radial): 0.6mm

[0071] - Cutting fluid: Use

[0072]

[0073] The results of the cutting test were evaluated according to the following evaluation criteria, and the results are shown in Table 2 below.

[0074] 1) Ti alloy

[0075] - Planar machining, with a single machining distance of 0.3m from entry to exit and a lifespan of 14.4m, 14.4(m) / 0.3(m / rotation) = 48 machining cycles

[0076] - End of life criteria: Test terminates when tip chipping size is 0.2mm or larger.

[0077] 2) Inconel

[0078] - Planar machining, with a single machining distance of 0.2m from entry to exit and a lifespan of 2m, 2(m) / 0.2(m / rotation) = 10 machining passes.

[0079] - End of life criterion: Test terminates when edge wear exceeds 0.15mm.

[0080] Classification KTi-6Al-4V Alloy INCONEL718 Machining Length (m) Wear Type Machining Length (m) Wear Type Comparative Example 1-1 2.6-edge chipping 2-edge section wear Comparative Example 2-6.6-edge chipping 6-edge section wear Comparative Example 3-9.6-edge chipping 6-edge section wear Example 10 14.4-edge chipping 10-edge section wear Example 20 11 4.4-edge chipping 10-edge section wear Example 30 22 4-edge chipping 12-edge section wear Example 40 25 33.6-edge chipping 12-edge section wear Example 50 33 3.6-edge chipping 12-edge section wear Example 60 4 38.4-edge chipping 14-edge section wear Example 70 5 38.4-edge chipping 14-edge section wear Example 80 6 33.6-edge Chipping 12-edge blade wear Example 90.7 14. 4-edge tip Chipping 4-edge blade wear Example 100.8 14. 4-edge tip Chipping 2-edge blade wear Example 110.9 14. 4-edge tip Chipping 2-edge blade wear

[0081]

[0082] As shown in Table 2 above, Examples 1 to 11 of the present invention exhibited improved cutting performance when machining titanium alloys compared to Comparative Examples 1 to 3. In addition, Examples 1 to 8 of the present invention exhibited improved cutting performance when machining Ti alloys and Inconel alloys compared to Comparative Examples 1 to 3.

[0083] Table 3 below shows the thickness ratio k(T of layer E and layer C). E / T C Figures 2 and 3 (horizontal axis is k, vertical axis is life (m)) show the results of the cutting test evaluation of the workpiece, Inconel alloy and titanium alloy, according to the method.

[0084] K00.10.20.250.30.40.50.60.70.80.9 Inconel life (m) 1010121212141412422 Ti alloy life (m) 14.414.42433.633.638.438.433.614.414.414.4

[0085]

[0086] As shown in Table 3 and Figures 2 and 3 above, the machining performance of Inconel alloy and titanium alloy, which are difficult-to-machine materials, is significantly affected by the thickness ratio of the E layer and the C layer, and in particular, excellent machining performance was exhibited when maintained at 0.24 to 0.61 (Examples 4 to 8), and even better characteristics were exhibited when maintained at 0.35 to 0.55 (Examples 6 and 7).

Claims

1. A hard film formed on the surface of a hard gas by the PVD method, The hard film comprises layers A, B, C, D, and E that are sequentially deposited on the surface of the hard gas, and The above A layer is Ti 1-a Me1 a C x N y It consists of (0.2≤a≤0.7, x+y=1, 0≤y≤1, Me1 being one or more elements selected from groups 3 to 16), and The above C layer is Ti 1-x-y Si y Me2 x C w N z (0≤x≤0.4, 0.005≤y≤0.35, w+z=1, 0≤z≤1, Me2 is composed of one or more selected from Al, Cr, V, Zr, Nb, Mo, Hf, Ta, W, Y), and The above E layer is Cr 1-x Me3 x It is composed of N (0.1≤x≤0.7, where Me3 is one or more elements selected from groups 3 to 16), and The above B layer comprises an alternating repeating layer in which a nanolayer composed of an A layer and a C layer, each having a thickness of 10 to 30 nm, is alternately stacked two or more times. A hard coating for a cutting tool, wherein the above D layer comprises an alternating repeating layer in which a nanolayer consisting of a C layer and an E layer having a thickness of 10 to 30 nm is alternately stacked two or more times.

2. In Paragraph 1, The thickness ratio K(T of the above E layer and C layer) E / T C A hard coating for cutting tools having a value of 0.24 to 0.

61.

3. In Paragraph 1, The above Me1, Me2, and Me3 are hard coatings for cutting tools containing Al.

4. In Paragraph 1, A hard coating for a cutting tool, wherein the thickness of the above B layer and D layer is 300 nm or less.

5. In Paragraph 1, A hard coating for a cutting tool, wherein the thickness of the hard coating is 0.5 to 9.0 μm.

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