Cutting tool having hard coating

Abstract

The present invention relates to a cutting tool having a hard coating 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. The hard coating includes a first coating made of AlaCrbMe(1-a-b)NxOy (a, b, x, and y are atomic ratios, a+b≤1, 0.5≤x≤1, 0≤y≤0.5, x+y=1, and Me is at least one selected from group 4 elements, group 5 elements, group 6 elements, Si, B, and S). When a point where the clearance surface and the inclined surface of the cutting tool meet is referred to as a lead-in portion R, and an Al atomic ratio of the first coating within a range of 50 μm in the direction of the inclined plane and the clearance surface in the lead-in portion R is referred to as Ra, 0.7<Ra≤0.85 is satisfied, and when the central point of the clearance surface is C and the Al atomic ratio in the first coating within 100 ㎛ around C is Ca, 0.55≤Ca≤0.7 is satisfied.

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] Steel is a material capable of achieving a variety of properties, including carbon content and heat treatment. For cutting tools used to process this steel, not only wear resistance but also lubricity and oxidation resistance are crucial. To achieve this, technologies are being employed to form a hard film made of various ceramics on cutting tools to extend their lifespan.

[0010] Among hard coatings for cutting tools, composite nitride films of aluminum and chromium possess excellent lubricity and heat resistance, as well as excellent wear resistance, demonstrating superior durability in cutting various types of steel. However, in the case of composite nitrides of aluminum and chromium, while toughness improves as the aluminum content increases, wear resistance deteriorates sharply.

[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 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.

[0013] 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 made of Al. a Cr b Me (1-a-b) N x O y (a, b, x, y are atomic ratios, a+b≤1, 0.5≤x≤1, 0≤y≤0.5, x+y=1, Me is at least one selected from group 4 elements, group 5 elements, group 6 elements, Si, B and S), and 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 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. a When , 0.7 <R a ≤0.85, and the center point of the above free surface is C, and the Al atomic ratio of the first film within 50㎛ around C is C a When , 0.55≤C a A cutting tool satisfying ≤0.7 is provided.

[0014] In addition, in the first film, R a / C a ≥1.03 can be satisfied.

[0015] Additionally, the thickness of the hard film may be 0.5 to 10 μm, and the thickness of the first film may be 0.1 μm or more.

[0016] 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-c-d-e) Ti c Cr d Me e N (c, d, e are atomic ratios, 0≤c≤0.8, 0≤d≤0.5, 0≤e≤0.15, c+d>0, c+d+e<1, Me is at least one selected from B, Si, Zr, V, Mn, Nb, Mo, Ta, and W).

[0017] 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.

[0018] Figure 1 is a drawing showing the cutting edge, rake face, clearance face, and center of the clearance face of a cutting tool.

[0019] Figure 2 is a drawing showing the cutting edge and center of a drill and end mill shaped cutting tool.

[0020] Figure 3 is a drawing showing an area within 50 μm from the center of the cutting edge of a cutting tool.

[0021] Figure 4 is a drawing schematically showing a cross-sectional structure of a cutting tool according to an embodiment of the present invention.

[0022] 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.

[0023] The present invention is a cutting tool comprising a hard base material and a hard film formed on the hard base material.

[0024]

[0025] [Hard base material]

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030]

[0031] [Hard film]

[0032] A hard film is a film formed on the hard base material.

[0033] In one embodiment of the present invention, a cutting tool comprising a hard base material and a hard film formed on the hard base material, wherein the hard film is made of Al a Cr b Me (1-a-b) Nx O y (a, b, x, y are atomic ratios, a+b≤1, 0.5≤x≤1, 0≤y≤0.5, x+y=1, Me is at least one selected from group 4 elements, group 5 elements, group 6 elements, Si, B and S), and 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 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. a When , 0.7 <R a ≤0.85, and the center point of the above free surface is C, and the Al atomic ratio of the first film within 50㎛ around C is C a When , 0.55≤C a It is characterized by satisfying ≤0.7.

[0034] 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.

[0035] The present invention comprises Al constituting the first film. a Cr b Me (1-a-b) N x O y In the film, as shown in Fig. 3, the atomic ratio of Al included in the film formed in the edge portion R and the area within 50 μm adjacent to the edge portion R is 0.7. <R a By making it relatively high at ≤0.85, the chipping resistance of the cutting edge is improved by providing toughness that can respond to impact continuously applied to the cutting edge.

[0036] In addition, Al constituting the first film a Cr b Me (1-a-b) N x O yIn the film, the atomic ratio of Al is 0.55≤C for the area within the center point C of the free surface and its surrounding 50㎛. a By improving the wear resistance by making it relatively low at ≤0.7, the wear resistance of the clearance surface where friction with chips continuously occurs is improved.

[0037] That is, by forming the atomic ratio of Al constituting the first film differently in the cutting edge and the clearance surface, the durability of the cutting tool can be improved even when used for cutting various types of steel, thereby obtaining the effect of further extending the lifespan.

[0038] In addition, in the first film, R a / C a It is desirable to satisfy ≥1.03. This is because it is more desirable for the overall cutting tool life to be extended through the local optimization effect of improving the chipping resistance of the cutting edge and the wear resistance of the clearance surface when the difference between the Al atomic ratio of the cutting edge R and the Al atomic ratio of the center point C of the clearance surface is at least greater than the above numerical range.

[0039] 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.

[0040] In addition, it is preferable that the thickness of the first film be 0.1 ㎛ or more, because if the thickness of the first film is less than 0.1 ㎛, the effect of the first film is not sufficient.

[0041] 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.

[0042] The above second film is Al (1-c-d-e) Ti c Crd Me e N (c, d, e are atomic ratios, 0≤c≤0.8, 0≤d≤0.5, 0≤e≤0.15, c+d>0, c+d+e<1, Me is at least one selected from B, Si, Zr, V, Mn, Nb, Mo, Ta, and W).

[0043] 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.

[0044] 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.

[0045] 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≤c≤0.8 and 0≤d≤0.5.

[0046] 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≤e≤0.15.

[0047] 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.

[0048] In addition, in the inclined plane region at least 200 ㎛ away from the guide section in the direction perpendicular to the guide section, Al constituting the first film a Cr b Me (1-a-b) N x O y The film can be formed so that the atomic ratio of Al is 0.55 to 0.7.

[0049]

[0050] <Example>

[0051] 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.

[0052] Specifically, the arc targets used for coating were TiAl, AlCr, and AlCrSi, and the base material was 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.

[0053] 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.

[0054] The second film was formed using TiAl, AlCr, and AlCrSi 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.

[0055] The above first film was formed using AlCr and AlCrSi targets at a bias voltage of -400 to -200 V, an arc current of 100 to 150 A, and a pressure of 20 to 40 mtorr by injecting N2 as a reaction gas.

[0056] 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.

[0057] 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) - 2.5 AlCr (70:30) - 300 1.2 Example 2 TiAl (50:50) - 3.1 AlCrSi (70:20:10) - 400 0.8 Example 3 TiAl (50:50) AlCr (70:30) - 2.5 AlCr (70:30) - 2.5 2.0 Example 4 TiAl (50:50) AlCr (70:30) - 2.1 AlCr (75:35) - 400 1.5 Example 5AlCr(70:30)-2.3AlCr(70:30)-2002.0Example 6AlCr(70:30)-3.4AlCrSi(70:20:10)-2000.5Example 7AlCr(70:30)AlCrSi(60:30:10)3.5AlCr(70:30)-3000.9Comparative Example 1TiAl(50:50)-2.3AlCr(70:30)-301.4Comparative Example 2TiAl(50:50)-2.9AlCrSi(70:20:10)-701.0Comparative Example 3TiAl(50:50)AlCr(70:30)2.1AlCr(70:30)-701.9Comparative Example 4TiAl(50:50)AlCr(70:30)2.3AlCr(75:35)-501.5Comparative example 5AlCr(70:30)-2.3AlCr(70:30)-402.1Comparative example 6AlCr(70:30)-3.5AlCrSi(70:20:10)-400.6Comparative example 7AlCr(70:30)AlCrSi(60:30:10)3.0AlCr(70:30)-501.3

[0058] The Si content of each part was measured for the samples made according to the conditions of Table 1. The cross-sections of the hard films of the examples and comparative examples according to Table 1 were 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 Al atomic ratio of the first film within a range of 50 μm from the edge portion R in the direction of the rake surface and the relief surface is Ra, the central point of the relief surface is C, and the Al atomic ratio of the first film within 50 μm around C is C. a , the Al atomic ratio of the first film 500 ㎛ away from the R part toward the C direction toward the free surface is W a The results when said are shown in Table 2 below (the Al content at this time is the content excluding non-metals).

[0059] Classification R a (at.%)W a (at.%)C a (at.%)R a / C a Example 175.372.568.51.10 Example 282.578.169.31.19 Example 373.469.969.71.05 Example 480.376.474.11.08 Example 573.369.169.91.05 Example 679.375.370.21.13 Example 776.471.869.71.10 Comparative Example 167.268.569.90.96 Comparative Example 268.269.069.50.98 Comparative Example 366.568.969.80.95 Comparative Example 473.574.174.50.99 Comparative Example 568.569.069.30.99Comparison Example 669.169.769.80.99Comparison Example 768.769.170.10.98

[0060] In the case of the example, the analysis result using EDS showed that the Al content of the first film was 0.7 <R a ≤0.85, and W a In C aAs the distance from the lead wire increases, the Al content of the first film gradually increases and 0.55≤C a It can be confirmed that the range of ≤0.7 is satisfied. Also, R a / C a It can be confirmed that ≥1.03 is satisfied, and the wear resistance and chipping resistance of the hard film formed in this way were evaluated under the following conditions.

[0061]

[0062] (1) Wear resistance evaluation

[0063] Workpiece material: Carbon steel SM45C (300mm×200mm×100mm)

[0064] Sample Model Number: SNMX1206ANN-MM

[0065] Cutting speed: 250 m / min

[0066] Cutting feed: 0.2 mm / rev

[0067] Cutting depth: 2.0 mm

[0068] Cutting oil: not used

[0069]

[0070] (2) Chipping resistance evaluation

[0071] Workpiece material: Mold steel NAK80 (300mm×200mm×100mm)

[0072] Sample Model Number: ADKT170608PESR-MM

[0073] Cutting speed: 100 m / min

[0074] Cutting feed: 0.15 mm / tooth

[0075] Cutting depth: 5mm

[0076] Cutting oil: not used

[0077]

[0078] The processing results evaluated under the two conditions as described above are shown in Table 3 below.

[0079] Classification SM45C Machining Results NAK80 Machining Results Machining Length (mm) Wear Type Machining Length (mm) Wear Type Example 17500 Normal Wear 2100 Wear / Chipping Example 27900 Normal Wear 1900 Wear / Chipping Example 36900 Normal Wear 1500 Wear / Chipping Example 47100 Normal Wear 1400 Boundary Chipping Example 57300 Normal Wear 1900 Wear / Chipping Example 67900 Normal Wear 1500 Wear / Chipping Example 78200 Normal Wear 2200 Wear / Chipping Comparative Example 16100 Excessive Wear 1900 Wear / Chipping Comparative Example 26500 Excessive Wear 1400 Wear / Chipping Comparative Example 35900 Excessive wear 1000R chipping comparison example 45300 Excessive wear 1100 Borderline chipping comparison example 55700 Excessive wear 1000 Borderline chipping comparison example 64500 Excessive wear 800R chipping comparison example 76500 Normal wear 1300 Wear / chipping

[0080] As shown in the cutting performance evaluation results above, Examples 1 to 7 exhibited superior tool life compared to Comparative Examples 1 to 7. In particular, as the machining length of the SM45C workpiece increased significantly, the machining length of the NAK80 workpiece also showed improved results. Through this, it was confirmed that the tool life was improved by complementing the wear resistance and chipping resistance through the difference in the Al 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 Al a Cr b Me (1-a-b) N x O y (a, b, x, y are atomic ratios, a+b≤1, 0.5≤x≤1, 0≤y≤0.5, x+y=1, Me is at least one selected from group 4 elements, group 5 elements, group 6 elements, Si, B, and S) including a first film, The point where the clearance surface and the rake surface of the cutting tool meet is called the cutting edge R, and the Al atomic ratio of the first film is R within a range of 50 ㎛ from the cutting edge R in the direction of the rake surface and the rake surface. a When , 0.7 <R a ≤0.85, Let the center point of the above free surface be C, and the Al atomic ratio of the first film within 50㎛ around C be C a When , 0.55≤C a Cutting tool satisfying ≤0.

7.

2. In paragraph 1, In the above first film, R a / C a Cutting tool satisfying ≥1.

03.

3. In paragraph 1, The thickness of the above hard film is 0.5 to 10㎛, A cutting tool, wherein the thickness of the first film is 0.1㎛ 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-c-d-e) Ti c Cr d Me e A cutting tool comprising N (c, d, e are atomic ratios, 0≤c≤0.8, 0≤d≤0.5, 0≤e≤0.15, c+d>0, c+d+e<1, Me is at least one selected from B, Si, Zr, V, Mn, Nb, Mo, Ta, and W).

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