Cutting tool having hard film

Abstract

The present invention relates to a cutting tool in which a hard film is formed on a hard base material such as cemented carbide, cermet, and CBN. The cutting tool according to the present invention comprises: a hard base material; and a hard film formed on the hard base material, and is characterized in that the hard film is composed of a single layer or a multilayer structure of two or more layers, a surface layer is composed of TiaAlbMecC1-xNxOy (wherein 0.5≤x≤1, 0≤y≤0.5, a, b, c, x, y are atomic ratios, and Me is at least one selected from group 4 elements, group 5 elements, group 6 elements, Si, B, and S of the periodic table), the composition of the cutting edge portion of the cutting tool is 0.6≤a≤0.9, 0.1≤b≤0.3, 0≤c≤0.1, and the composition of the central portion of the flank face of the cutting tool is 0.2≤a≤0.55, 0.45≤b≤0.7, 0≤c≤0.1.

Description

Cutting tools with hard film formation

[0001] This study was conducted as a part of the Ministry of Trade, Industry and Energy's DNA Convergence Industry-Academic Cooperation Project for SMEs (Project Identification Number: 1415182096, Project Number: P0021347, Project Management (Specialist) Organization: Korea Institute for Advancement of Technology, Research Project Title: Establishment and Demonstration of an Integrated Database for the Development of PVD Thin Films for Machining High-Hardness, Difficult-to-Machine Parts).

[0002] The present invention relates to a hard film formed on a hard base material such as a superalloy, cermet, ceramic, or cubic boron nitride used in a cutting tool, and more specifically, to a cutting tool having an improved lifespan by differently controlling the composition of each part of the hard film formed on the cutting tool.

[0003]

[0004] Cutting tools require a variety of properties, including wear resistance against friction with the workpiece, lubricity, impact resistance, and oxidation resistance. To achieve this, technologies are being employed to form a hard film made of various ceramics on cutting tools to extend their lifespan.

[0005] TiAlN thin films composed of nitrides of Ti and Al show a tendency for the Pugh's coefficient to decrease as the Al content decreases, and have a value of 0.7 or less when the Al content is 30 at% or less. On the other hand, the hardness of TiAlN thin films tends to increase as the Al content increases, and especially when the Al content is 45% or more, it shows characteristics close to the hardness saturation point.

[0006] Meanwhile, in the case of cutting tools, the properties of the hard film required for, for example, the cutting edge, which is subjected to continuous impact, and the rake face and / or flank face, which are subjected to continuous friction with chips, may vary.

[0007]

[0008] The object of the present invention is to provide a hard film for cutting tools having improved wear resistance and chipping resistance compared to conventional hard films.

[0009]

[0010] The present invention is a cutting tool comprising a hard base material and a hard film formed on the hard base material, wherein the hard film is formed as a single layer or a multilayer structure of two or more layers, and the surface layer is made of Ti. a Al b Me c C 1-x N x O y (0.5≤x≤1, 0≤y≤0.5, a, b, c, x, y are atomic ratios, Me is at least one selected from group 4 elements, group 5 elements, group 6 elements, Si, B, and S of the periodic table), and a cutting tool having a composition of a cutting edge portion of the cutting tool of 0.6≤a≤0.9, 0.1≤b≤0.3, 0≤c≤0.1, and a composition of a central portion of a clearance surface of the cutting tool of 0.2≤a≤0.55, 0.45≤b≤0.7, 0≤c≤0.1 is provided.

[0011] Additionally, the total thickness of the hard film may be 0.5 to 10 μm, and the thickness of the surface layer may be 0.1 to 3 μm.

[0012] In addition, in the surface layer, the Al atomic ratio (R) of the lead part Al ) for the central part of the free surface Al atomic ratio (C Al ) is the ratio of C Al / R Al This can be 1.5 to 7 days.

[0013] Additionally, in the surface layer, the composition of the inclined surface 500 μm away from the cutting edge may be 0.2≤a≤0.55, 0.45≤b≤0.7, 0≤c≤0.1.

[0014]

[0015] The cutting tool according to the present invention can extend the life of the cutting tool by improving the chipping resistance of the cutting edge portion to which continuous impact is applied during cutting and by improving the wear resistance of the clearance surface where continuous friction with chips occurs, thereby locally exhibiting optimal cutting performance according to the location area of ​​the hard film.

[0016]

[0017] Figure 1 is a drawing showing the cutting edge, rake face, clearance face, and center of the clearance face of an insert-shaped cutting tool.

[0018] Figure 2 is a drawing showing the cutting edge and the center of the clearance surface of a drill-shaped cutting tool.

[0019] Figure 3 schematically shows the state of the Al content of a hard film according to one embodiment of the present invention.

[0020]

[0021] Hereinafter, in describing the present invention, if it is determined that a specific description of a related known function or configuration may unnecessarily obscure the gist of the present invention, such detailed description will be omitted. In addition, when it is said that a part "includes" a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless specifically stated otherwise.

[0022] The present invention is a cutting tool comprising a hard base material and a hard film formed on the hard base material.

[0023] [Hard base material]

[0024] Hard substrates can be made of a variety of materials used in cutting tools, including cemented carbides, cermets, ceramics, and cubic boron nitride.

[0025] The above hard substrate can be formed into a shape required for a cutting tool, for example, it can be formed into an insert shape or a drill shape.

[0026] A cutting tool formed into an insert shape is formed into a roughly rectangular parallelepiped shape, as illustrated in Fig. 1, and has a fastening hole formed in the center. In the drawing, the upper surface forms a rake face, the side surface in the drawing forms a flank face, the boundary between the rake face and the flank face forms a cutting edge, and the four corners form a nose.

[0027] In the case of a cutting tool having an insert shape, the “center” of the clearance surface means the point where the diagonals of the four corners constituting the clearance surface intersect, as illustrated in Fig. 1.

[0028] The 'center' of a cutting tool formed in the shape of a drill or endmill means the center of the distance between the cutting edges of the cutting edge that is 2 mm or more away from the bottom edge and the next cutting edge that meets in the vertical direction, as illustrated in Fig. 2.

[0029]

[0030] [Hard film]

[0031] A hard film is a film formed on the hard base material.

[0032] In one embodiment of the present invention, the hard film is formed of a single layer or a multilayer structure of two or more layers, and the surface layer is made of Ti. a Al b Me c C 1-x N x O y(0.5≤x≤1, 0≤y≤0.5, a, b, c, x, y are atomic ratios, Me is at least one selected from group 4 elements, group 5 elements, group 6 elements, Si, B, and S of the periodic table), and the cutting tool has a composition of a cutting edge portion of 0.6≤a≤0.9, 0.1≤b≤0.3, 0≤c≤0.1, and the central portion of a clearance surface of the cutting tool has a composition of 0.2≤a≤0.55, 0.45≤b≤0.7, 0≤c≤0.1.

[0033] In the present invention, the edge portion refers to a range within 50 μm of the inclined surface and the clearance surface direction in a direction perpendicular to the edge portion based on the edge, and the center of the clearance surface refers to a range within a radius of 50 μm from the center point of the clearance surface.

[0034] The present invention comprises Ti constituting a surface layer a Al b Me c C 1-x N x O y In the film, the atomic ratio of Al in the surface layer formed on the cutting edge is kept low at 0.1 to 0.3 to provide toughness that can withstand continuous impact on the cutting edge, thereby improving the chipping resistance of the cutting edge. In addition, Ti constituting the surface layer a Al b Me c C 1-x N x O y In the film, the wear resistance is improved by increasing the atomic ratio of Al to 0.45 to 0.70 in the central part of the clearance surface, thereby improving the wear resistance of the clearance surface where friction with chips continuously occurs. That is, the present invention achieves the effect of further extending the life of the cutting tool by responding to the film properties that are locally preferentially required by adjusting the atomic ratio of Al in the TiAlN film constituting the surface layer differently in the cutting edge part and the clearance surface.

[0035] In addition, in the surface layer, the Al atomic ratio (R) of the lead partAl ) for the central part of the free surface Al atomic ratio (C Al ) is the ratio of C Al / R Al It is desirable that this be 1.5 to 7. This is because the difference between the Al atomic ratio of the cutting edge and the Al atomic ratio of the central part of the clearance surface is at least greater than the above numerical range, which is more desirable for extending the overall cutting tool life through the local optimization effect of improving the chipping resistance of the cutting edge and the wear resistance of the clearance surface.

[0036] In addition, it is preferable that the thickness of the hard film be 0.5 to 10 ㎛. If the thickness of the hard film is less than 0.5 ㎛, the effect of the hard film is not sufficient, and if it exceeds 10 ㎛, the internal stress increases, which may actually lower the chipping resistance.

[0037] In addition, it is preferable that the thickness of the surface layer be 0.5 to 10 ㎛. If the thickness of the surface layer, which is a TiAlN film, is less than 0.5 ㎛, the effect of the surface layer is not sufficient, and if it exceeds 10 ㎛, the internal stress increases, which may actually lower the chipping resistance.

[0038] In addition, in the inclined plane area located at a distance of 500 ㎛ or more from the above-mentioned part, the composition of the surface layer can be formed with a composition of 0.2≤a≤0.55, 0.45≤b≤0.7, 0≤c≤0.1.

[0039]

[0040] <Example>

[0041] In an embodiment of the present invention, a hard film having a single layer or a multilayer structure of two or more layers was formed on the surface of a base material made of a superalloy by using two types of surface treatments (ion bombardment and arc ion plating, which is a physical vapor deposition (PVD) method).

[0042] Specifically, the arc targets used for coating were Ti, Al, TiAl, AlTi, TiAlSi, and AlTiSi, and the above-mentioned base materials were washed with wet microblasting and ultrapure water, and then mounted along the circumference at a predetermined distance in the radial direction from the central axis on the rotary table in the coating furnace in a dry state, and the initial vacuum pressure in the coating furnace was 8.5×10 -5 Depressurized to below 10 Torr

[0043] After heating the temperature to 400 to 600°C, the base material was rotated on the rotary table in an Ar gas atmosphere, and a bias voltage of -400 to -200 V was applied to the base material for 30 to 90 minutes to perform Ar ion bombardment. Thereafter, a bias voltage of -1000 to -600 V was applied, and an arc current of 70 to 150 A was supplied to the arc target (one of Ti and Cr) to perform metal (including semimetal) ion bombardment for 1 to 20 minutes. The metal ion bombardment may be performed before performing the Ar ion bombardment. The gas pressure for coating was maintained at 50 mTorr or less, preferably 40 mTorr or less, to form a thin film having a single layer or a multilayer structure of two or more layers.

[0044] The above thin film was formed using TiAl, AlCr, and TiAlSi targets under conditions of a bias voltage of -100 to -30 V, an arc current of 100 to 150 A, and a pressure of 20 to 40 mtorr by injecting N2 as a reaction gas.

[0045] The second film was formed using TiAl, AlCr, and TiAlSi targets under conditions of a bias voltage of -100 to -30 V, an arc current of 100 to 150 A, and a pressure of 20 to 40 mtorr with N2 injected as a reaction gas.

[0046] The examples and comparative examples of the present invention were manufactured under the above conditions, and basic information on the conditions and thickness of the corresponding hard film is shown in Table 1 below. The coating conditions may vary depending on the equipment characteristics and conditions.

[0047] ClassificationInner layerSurface layerTarget 1(composition ratio, atomic ratio)Target 2(composition ratio)Thickness(um)Target(composition ratio, atomic ratio)Bias voltage(V)Thickness(um)Example 1--0TiAl(50:50)-4003Example 2TiAl(50:50)AlCr(3:7)5.7TiAl(40:60)-4501Example 3AlCr(5:5)TiAl(67:33)3.2TiAlSi(5:4:1)-5001.2Example 4--0TiAl(50:50)-2002.5Example 5TiAl(7:3)TiAlSi(7:2:1)6.1TiAl(33:67)-3501.5Example 6--0TiAl(2:8)-5002.7Example 7AlCr(5:5)TiAlSi(5:4:1)3.5TIAl(3:7)-1502.3Comparative Example 1TiAlSi(7:2:1)TiAl(7:3)3.8TiAl(2:8)-1002.1Comparative Example 2TiAl(5:5)TiAl(6:4)3TiAlSi(5:4:1)-801Comparative Example 3TiAl(50:50)AlCr(3:7)4.6TiAl(5:5)-601.8Comparative Example 4--0TiAl(6:4)-502Comparative Example 5TiAl(8:2)TiAlSi(7:2:1)4.4TiAl(5:5)-1201.3Comparative Example 6TiAl(5:5)-2.5TiAl(3:7)-803 Comparative Example 7--0TiAl(2:8)-402.1

[0048] The Al content of each part was measured for the samples made according to the conditions of Table 1. The cross-section of the hard film of the examples and comparative examples according to Table 1 was analyzed with a SEM (Scanning Electron Microscope) at 15,000x magnification, and the composition was analyzed with an EDS (Energy Dispersive Spectrometer). As shown in Fig. 1, the point where the clearance surface and the rake surface of the cutting tool meet is called the edge portion R, and the Al atomic ratio of the surface layer film of the edge portion is R. Al, the center point of the above free surface is C Al And, the Al atomic ratio of the surface layer within 50㎛ around C is C a The results when said are shown in Table 2 below. (The Al content at this time is the content excluding non-metals.)

[0049] Classification R Al (atomic ratio) C Al (Atomic ratio) Example 10.20 0.45 Example 20.28 0.62 Example 30.15 0.57 Example 40.25 0.40 Example 50.23 0.68 Example 60.12 0.57 Example 70.26 0.61 Comparative Example 10.58 0.70 Comparative Example 20.37 0.41 Comparative Example 30.43 0.62 Comparative Example 40.48 0.55 Comparative Example 50.25 0.37 Comparative Example 60.60 0.62 Comparative Example 70.25 0.85

[0050] In the case of the example, the result of analysis using EDS showed that the Al content (atomic ratio) of the surface layer was 0.1 <R a ≤0.3, and the Al content (atomic ratio) of the central part of the free surface of the surface layer is 0.45≤C. a It can be confirmed that the range of ≤0.7 is satisfied. The wear resistance and chipping resistance of the hard film formed in this way were evaluated under the following conditions.

[0051] (1) Wear resistance evaluation

[0052] Workpiece material: Carbon steel SM45C (300mm*200mm*100mm)

[0053] Sample Model Number: SNMX1206ANN-MM

[0054] Cutting speed: 250 m / min

[0055] Cutting feed: 0.2 mm / rev

[0056] Cutting depth: 2.0 mm

[0057] Cutting oil: Use

[0058]

[0059] (2) Chipping resistance evaluation

[0060] Workpiece material: Stainless steel SUS316 (300mm*200mm*100mm)

[0061] Sample Model Number: ADKT170608PESR-MF

[0062] Cutting speed: 90 m / min

[0063] Cutting feed: 0.25 mm / tooth

[0064] Cutting depth: 4mm

[0065] Cutting oil: not used

[0066] The processing results evaluated under the two conditions as above are shown in Table 3 below.

[0067] Classification SM45C machining results SUS316 machining results Machining length (mm) Wear type Machining length (mm) Wear type Example 14500 Normal wear 2100 Wear / chipping Example 27500 Normal wear 1800 Boundary chipping Example 35200 Normal wear 2500 Wear / chipping Example 44200 Normal wear 2200 Wear / chipping Example 58100 Normal wear 1800 Boundary chipping Example 64200 Normal wear 2400 Wear / chipping Example 76700 Normal wear 2200 Wear / chipping Comparative example 14500 Excessive wear 1300 Boundary chipping Comparative example 23900 Excessive wear 1500 Wear / chipping Comparative example 34800 Excessive wear 900 Chipping / breakage comparison example 42500 Excessive wear 1300 Wear / chipping comparison example 54700 Excessive wear 1100 Border chipping comparison example 64600 Excessive wear 1100 Border chipping comparison example 72100 Normal wear 800 Wear / chipping

[0068] As shown in the cutting performance evaluation results above, Examples 1 to 7 exhibited superior tool life to Comparative Examples 1 to 7. In particular, as the machining length of the SM45C workpiece increased significantly, the machining length of the SUS316 workpiece also showed improved results. Through this, it was confirmed that the wear resistance and chipping resistance were improved through the difference in the Al content of the cutting edge, rake face, and clearance face.

Claims

1. Hard base material and A cutting tool including a hard film formed on the hard base material, The above hard film is formed of a single layer or a multilayer structure of two or more layers, The surface layer is Ti a Al b Me c C 1-x N x O y (0.5≤x≤1, 0≤y≤0.5, a, b, c, x, y are atomic ratios, Me is at least one selected from group 4 elements, group 5 elements, group 6 elements, Si, B, and S of the periodic table), A cutting tool having a composition of the cutting edge of the cutting tool of 0.6≤a≤0.9, 0.1≤b≤0.3, 0≤c≤0.1, and a composition of the central portion of the clearance surface of the cutting tool of 0.2≤a≤0.55, 0.45≤b≤0.7, 0≤c≤0.

1.

2. In paragraph 1, The total thickness of the above hard film is 0.5 to 10㎛, A cutting tool having a thickness of the surface layer of 0.1 to 3㎛.

3. In paragraph 1, In the above surface layer, the Al atomic ratio (R) of the guide part Al ) for the central part of the free surface Al atomic ratio (C Al ) is the ratio of C Al / R Al This 1.5 to 7 person, cutting tool.

4. In paragraph 1, A cutting tool, wherein the composition of the inclined surface 500㎛ away from the cutting edge is 0.2≤a≤0.55, 0.45≤b≤0.7, 0≤c≤0.1 in the above surface layer.

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