Cutting tool having hard coating

Abstract

The present invention relates to a cutting tool in which a hard coating is formed on a hard base material such as cemented carbide, cermet, or CBN. 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 first coating consisting of Ti(1-x)SixN (x is an atomic ratio), satisfies 0<Rx≤0.10 wherein R refers to a cutting edge portion where the flank face and rake face of the cutting tool intersect, and Rx refers to the Si atomic ratio of the first coating within a range of 50 μm from the cutting edge portion R to the rake face and the flank face, and satisfies 0.15≤Cx≤0.30 wherein C refers to the central point of the flank face, and Cx refers to the Si atomic ratio of the first coating within 50 μm around C.

Description

Cutting tools with hard film formation

[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 in which a hard film is formed on a hard base material such as a cemented carbide, cermet, or CBN.

[0009] When machining high-hardness workpieces, such as steel with a hardness of HRC 50 or higher, a technology is being adopted to form a hard film made of various ceramics on the surface of the cutting tool to improve the life of the cutting tool.

[0010] Among these hard films, TiSiN films, which are composite nitrides of Ti and Si, exhibit excellent wear resistance and heat resistance, and thus exhibit excellent durability in cutting processing of high-hardness steels. However, TiSiN films have the problem that when the Si content is high, their wear resistance is excellent, but their chipping resistance is low, and when the Si content is low, their wear resistance is low.

[0011] Depending on the area of ​​the cutting tool, for example, the characteristics of the hard film required for the cutting edge, which is subject to continuous impact, and the rake face or flank face, which is subject to continuous friction with the chip, may vary.

[0012] The following patent document describes the content of Si on an atomic basis on the flank surface within 500 ㎛ from the center of the edge. Si , the content of Si on an atomic basis in the rake surface within 500 ㎛ from the center of the line is R Si When 0.5<F Si / (F Si +R Si )≤0.6, thereby improving the wear resistance of a cutting tool and enhancing chipping resistance by differently controlling the Si content of the rake face and the clearance face with the cutting edge as the boundary.

[0013] The object of the present invention is to provide a hard film for a cutting tool having improved wear resistance while maintaining chipping resistance at a certain level or higher.

[0014] 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 Ti. (1-x) Si x The first film is made of N (x is an atomic ratio), and the point where the clearance surface and the rake surface of the cutting tool meet is called the edge portion R, and the Si atomic ratio of the first film is R within a range of 50 μm from the edge portion R in the direction of the rake surface and the clearance surface. x When , 0 <R x ≤0.10, and the center point of the above free surface is C, and the Si atomic ratio of the first film within 50㎛ around C is C x When , 0.15≤C x A cutting tool satisfying ≤0.30 is provided.

[0015] In addition, in the first film, R x / C x <0.67 can be satisfied.

[0016] Additionally, the thickness of the first film may be 0.1 to 3 μm, and the hardness of the first film may be 40 GPa or more.

[0017] In addition, the hard film further includes a second film formed on the lower portion of the first film, and the second film is made of Al. (1-a-b-c) Ti a Cr b Me c N (Me is one selected from B, Si, Zr, V, Mn, Nb, Mo, Ta, W, and 0≤a≤0.8, 0≤b≤0.5, 0≤c≤0.15, 0<a+b, a+b+c<1, a, b, c are atomic ratios) can be formed.

[0018] Additionally, the thickness of the second film may be 0.1 to 10 μm.

[0019] The cutting tool according to the present invention maintains the chipping resistance of the cutting edge portion to which continuous impact is applied, while improving the wear resistance of the clearance surface where friction with chips continuously occurs, thereby locally exhibiting optimal cutting performance according to the location area of ​​the hard film, thereby extending the life of the cutting tool when processing a workpiece with high hardness, such as high-hardness steel.

[0020] Figure 1 is a drawing showing the cutting edge, rake face, clearance face, and center of the clearance face of a cutting tool.

[0021] Figure 2 is a drawing showing the cutting edge and center of a drill and end mill shaped cutting tool.

[0022] Figure 3 is a drawing showing an area within 50 μm from the center of the cutting edge of a cutting tool.

[0023] Figure 4 is a drawing schematically showing a cross-sectional structure of a cutting tool according to an embodiment of the present invention.

[0024] 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.

[0025] The present invention is a cutting tool comprising a hard base material and a hard film formed on the hard base material.

[0026] [Hard base material]

[0027] 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, a drill shape, and an endmill shape.

[0028] 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.

[0029] 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.

[0030] 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.

[0031]

[0032] [Hard film]

[0033] A hard film is a film formed on the hard base material.

[0034] In one embodiment of the present invention, the hard film is Ti (1-x) Si x The first film is made of N (x is an atomic ratio), and the point where the clearance surface and the rake surface of the cutting tool meet is called the edge portion R, and the Si atomic ratio of the first film is R within a range of 50 μm in the direction of the rake surface and the clearance surface from the edge portion R. x When , 0 <R x ≤0.10, and the center point of the above free surface is C, and the Si atomic ratio of the first film within 50㎛ around C is C x When , 0.15≤C x It is characterized by satisfying ≤0.30.

[0035] The above first film may preferably be positioned on the upper surface (top surface) of the hard film. In addition, the above first film may be formed of one layer or may be formed of a multilayer structure in which two or more layers are laminated.

[0036] The present invention comprises Ti constituting the first film. (1-x) Si x In the N film, as shown in Fig. 3, the atomic ratio of Si included in the film formed in the leading part R and the area within 50 μm adjacent to the leading part R is 0. <R x By setting it relatively low to ≤0.10, the chipping resistance of the cutting edge is improved by providing toughness that can respond to continuous impact applied to the cutting edge.

[0037] Additionally, Ti, which constitutes the first film (1-x) Si x In the N film, the atomic ratio of Si is 0.15≤C for the area within the center point C of the free surface and its surrounding 50㎛. xBy increasing the wear resistance relatively to ≤0.30, the wear resistance of the free surface where friction with chips continuously occurs is improved.

[0038] That is, by making the atomic ratio of Si constituting the first film different between the cutting edge and the clearance surface, it is possible to obtain an effect of further extending the life of the cutting tool, especially when machining a workpiece with high hardness, such as high-hardness steel of HRC 50 or higher.

[0039] In addition, in the first film, R x / C x It is desirable to satisfy <0.67. This is because it is more desirable for the difference between the Si atomic ratio of the cutting edge R and the Si atomic ratio of the central point C of the clearance surface to be at least within the above numerical range to improve the chipping resistance of the cutting edge and extend the overall cutting tool life through improved wear resistance of the clearance surface.

[0040] In addition, it is preferable that the first film has a thickness of 0.1 to 3 μm. This is because, if the thickness of the first film is less than 0.1 μm, the wear resistance of the first film cannot be sufficiently realized, and if it exceeds 3 μm, the internal stress increases, which may actually reduce the chipping resistance. A more preferable thickness of the first film is 0.2 to 1.5 μm.

[0041] Additionally, the hardness of the first film may preferably be 40 GPa or more.

[0042] In addition, the hard film may further include a second film formed on the lower portion of the first film and having a multilayer structure consisting of one layer or two or more layers, as illustrated in FIG. 4.

[0043] The above second film is Al (1-a-b-c) Ti a Cr b Me cN (Me is one selected from B, Si, Zr, V, Mn, Nb, Mo, Ta, W, and 0≤a≤0.8, 0≤b≤0.5, 0≤c≤0.15, 0<a+b, a+b+c<1, a, b, c are atomic ratios) can be formed.

[0044] The second film, which is a nitride thin film containing Al and Ti or Cr, is known to have excellent wear resistance, heat resistance, and chipping resistance. By placing the second film with this composition between the first film, which has excellent wear resistance, and the hard base material, the chipping resistance of the first film, which has excellent wear resistance but relatively poor chipping resistance, can be supplemented.

[0045] The second film may have any one of the metal elements B, Si, Zr, V, Mn, Nb, Mo, Ta, and W in addition to Al, Ti, and Cr. By controlling these metal elements, the wear resistance, chipping resistance, heat resistance, etc. of the second film can be significantly improved.

[0046] In the second film, a, b, and c determine the composition ratio of the metal elements Al, Ti, Cr, and Me. When the composition of Al is large, the wear resistance, oxidation resistance, and lubrication are better, but when the Al content is too high, there is a problem of increased chipping, so it is preferable that the contents of Ti and Cr be 0≤a≤0.8 and 0≤b≤0.5.

[0047] Other elements can improve the chipping resistance, heat resistance, and wear resistance of the second film by adding Zr, B, etc., but if the content is high, it can cause an increase in residual stress due to an increase in the amorphous phase. Therefore, it is preferable that the content of Me, which is an other element, be 0≤c≤0.15.

[0048] The thickness of the second film is preferably 0.1 to 10 ㎛, and a more preferable thickness is 1 to 8 ㎛, because if it is less than 1 ㎛, it is difficult to sufficiently compensate for wear resistance, and if it exceeds 10 ㎛, internal stress increases, which may actually increase chipping.

[0049] In addition, in the inclined plane region at a distance of 200 ㎛ or more from the guide section in the direction perpendicular to the guide section, Ti constituting the first film (1-x) Si x The atomic ratio of Si in the N film can be formed to be 0.10 to 0.30.

[0050]

[0051] <Example>

[0052] In an embodiment of the present invention, a hard film composed of a second film and a first film was formed on a surface of a base material made of a superalloy using two types of surface treatments (ion bombardment) and an arc ion plating method, which is a physical vapor deposition (PVD) method, as shown in FIG. 4.

[0053] Specifically, the arc targets used for coating were TiAl, AlCr, and TiSi, and the base materials were wet microblasted and washed with 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.

[0054] 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. The gas pressure for coating was maintained at 50 mTorr or less, preferably 40 mTorr or less, to form the second film as the lower layer and the first film as the upper layer.

[0055] The second film was formed using TiAl, AlCr, and TiSi 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.

[0056] The above first film was formed using a TiSi target by applying a bias voltage of -400 to -200 V, an arc current of 100 to 150 A, and injecting N2 as a reaction gas under conditions of a pressure of 20 to 40 mtorr.

[0057] 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.

[0058] Classification 2 Film 1 Film Target 1 (Composition ratio) Target 2 (Composition ratio) Thickness (㎛) Target (Composition ratio) Bias voltage (V) Thickness (㎛) Example 1 TiAl (50:50) - 2.2 TiSi (80:20) - 300 1.0 Example 2 TiAl (50:50) - 2.5 TiSi (75:25) - 300 1.2 Example 3 TiAl (50:50) AlCr (70:30) 2.5 TiSi (80:20) - 250 0.8 Example 4 TiAl (50:50) AlCr (70:30) 2.6 TiSi (75:25) - 400 1.3 Example 5AlCr(70:30)-2.8TiSi(80:20)-2001.5Example 6AlCr(70:30)-2.0TiSi(75:25)-2001.3Example 7AlCr(70:30)TiSi(90:10)1.9TiSi(80:20)-3001.2Comparative Example 1TiAl(50:50)-2.3TiSi(80:20)-301.2Comparative Example 2TiAl(50:50)-2.6TiSi(75:25)-701.0Comparative Example 3TiAl(50:50)AlCr(70:30)2.5TiSi(80:20)-701.0Comparative Example 4TiAl(50:50)AlCr(70:30)2.8TiSi(75:25)-501.5Comparative example 5AlCr(70:30)-2.6TiSi(80:20)-401.6Comparative example 6AlCr(70:30)-2.0TiSi(75:25)-401.2Comparative example 7AlCr(70:30)TiSi(90:10)2.0TiSi(80:20)-501.3

[0059] The Si 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 relief surface and the rake surface of the cutting tool meet is called the edge portion R, and the Si atomic ratio of the first film within a range of 50 μm from the edge portion R toward the rake surface and the relief surface is R. x, the central point of the above free surface is C, and the Si atomic ratio of the first film within 50㎛ around C is C x , the Si atomic ratio of the first film, which is 500 ㎛ away from the R part toward the C side toward the free surface, is W x The results when said are shown in Table 2 below (the Si content at this time is the content excluding non-metals).

[0060] Classification R x (at.%)W x (at.%)C x (at.%)Rx / CxExample 17.214.819.20.38Example 29.218.624.30.38Example 38.515.719.70.43Example 46.717.423.90.28Example 59.814.619.50.50Example 69.519.124.40.39Example 77.614.519.60.39Comparative Example 117.719.119.80.89Comparative Example 220.123.924.70.81Comparative Example 315.618.919.50.80Comparative Example 421.924.324.70.89Comparative Example 517.219.420.10.86Comparative example 622.324.024.70.90Comparative example 717.119.019.90.86

[0061] In the case of the example, the Si content of the first film was 0 as a result of analysis using EDS. <R x ≤0.10, and W x In C x As the distance from the lead wire increases, the Si content of the first film gradually decreases and 0.15≤C x It can be confirmed that the range of ≤0.30 is satisfied. Also, R x / C x It can be confirmed that <0.67 is satisfied, and the wear resistance and chipping resistance of the hard film formed in this way were evaluated under the following conditions.

[0062]

[0063] (1) Wear resistance evaluation

[0064] Workpiece material: Heat-treated SKD61 (diameter: 100 mm)

[0065] Sample Model Number: CNNMG120408-VP3

[0066] Cutting speed: 80 m / min

[0067] Cutting feed: 0.15 mm / rev

[0068] Cutting depth: 1.5mm

[0069] Cutting oil: Use

[0070]

[0071] (2) Chipping resistance evaluation

[0072] Workpiece material: Mold steel NAK80 (300mm×200mm×100mm)

[0073] Sample Model Number: ADKT170608PESR-MM

[0074] Cutting speed: 100 m / min

[0075] Cutting feed: 0.15 mm / tooth

[0076] Cutting depth: 5mm

[0077] Cutting oil: not used

[0078]

[0079] The processing results evaluated under the two conditions as described above are shown in Table 3 below.

[0080] Heat treatment SKD61 processing results NAK80 processing results Chip removal amount (cm3) Wear type Processing length (mm) Wear type Example 1250 Normal wear 2600 Wear / chipping Example 2258 Normal wear 2000 Wear / chipping Example 3238 Normal wear 1800 Wear / chipping Example 4250 Normal wear 1400 Boundary chipping Example 5238 Normal wear 1200 R-shaped damage Example 6229 Normal wear 1000 Boundary chipping Example 7267 Normal wear 1800 Wear / chipping Comparative example 1188 Excessive wear 2200 Wear / chipping Comparative example 2217 Normal wear 1500 Wear / chipping Comparative example 3208 Normal wear 1000 boundary chipping comparison example 4204 Excessive wear 1100 boundary chipping comparison example 5188 Excessive wear 900R boundary damage comparison example 6196 Excessive wear 800R boundary damage comparison example 7213 Normal wear 1500 boundary chipping

[0081] 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, the chip removal amount for machining heat-treated SKD61 workpieces significantly increased, and the machining length for NAK80 workpieces also improved. Through this, it was confirmed that the tool life was improved by complementing wear resistance and chipping resistance through the difference in Si content between the cutting edge and the clearance surface.

Claims

1. Hard base material and A cutting tool including a hard film formed on the hard base material, The above hard film is Ti (1-x) Si x It comprises a first film composed of N (x is an atomic ratio), The point where the clearance surface and the rake surface of the cutting tool meet is called the cutting edge R, and the Si atomic ratio of the first film is set to R within a range of 50 μm from the cutting edge R in the direction of the rake surface and the rake surface. x When , 0 <R x ≤0.10 is satisfied, Let the center point of the above free surface be C, and the Si atomic ratio of the first film within 50㎛ around C be C x When , 0.15≤C x Cutting tool satisfying ≤0.

30.

2. In paragraph 1, In the above first film, R x / C x Cutting tool satisfying <0.

67.

3. In paragraph 1, The thickness of the above first film is 0.1 to 3 μm, A cutting tool, wherein the hardness of the first film is 40 GPa or more.

4. In paragraph 1, The above hard film further includes a second film formed on the lower portion of the first film, The above second film is Al (1-a-b-c) Ti a Cr b Me c A cutting tool composed of N (Me is one selected from B, Si, Zr, V, Mn, Nb, Mo, Ta, and W, 0≤a≤0.8, 0≤b≤0.5, 0≤c≤0.15, 0<a+b, a+b+c<1, a, b, and c are atomic ratios).

5. In paragraph 4, A cutting tool, wherein the thickness of the second film is 0.1 to 10㎛.

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