Cutting tool comprising cemented carbide as base material

Abstract

The present invention relates to a cutting tool comprising cemented carbide as a base material. The present invention provides a cutting tool comprising a cemented carbide base material, the cutting tool comprising: 2-20 wt% of a binder containing at least one of cobalt (Co), iron (Fe), and nickel (Ni); and 80-98 wt% of tungsten (W) carbide, wherein the tungsten (W) carbide comprises 0.5-2.5 vol% of a composite eta phase consisting of (W,Me)xCoyC (where x and y are 3-12, and Me is two or more selected from Ta, Nb, Cr, Zn, Mo, Ti, and Al).

Description

Cutting tool based on cemented carbide

[0001] The present invention relates to a cutting tool based on a cemented carbide.

[0002] Cemented carbide is a composite material manufactured by sintering metal carbides such as tungsten carbide (WC) and iron-based bonding metals such as iron (Fe), nickel (Ni), and cobalt (Co) using powder metallurgy, and is widely used as a material for cutting tools.

[0003] When manufacturing such cemented carbides, if there is a lack of carbon, the eta (η) phase is formed, and if there is an excess of carbon, free graphite is precipitated; the eta phase and free graphite are factors that degrade the physical properties of cutting tools. For this reason, generally, when manufacturing cemented carbides, measures are taken to prevent the formation of the eta phase or free graphite.

[0004] Meanwhile, Korean Patent Publication No. 2018-0095909 discloses a technology that increases resistance to comb cracks, which have been a problem in cutting tools for milling, by increasing the tungsten (W) content in the binder phase included in the cemented carbide and simultaneously generating a controlled and well-distributed eta phase.

[0005] The objective of the present invention is to provide a cutting tool based on a cemented carbide that can achieve characteristics of improved resistance to crack formation and plastic deformation compared to conventional cemented carbides, which have improved resistance to comb cracks by intentionally introducing an eta phase.

[0006] The problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0007] To solve the above problem, the present invention provides a cutting tool according to (1) to (8) below.

[0008] (1) A cutting tool comprising a cemented carbide substrate comprising 2 to 20 weight% of a binder comprising one or more of cobalt (Co), iron (Fe) and nickel (Ni), and 80 to 98 weight% of tungsten (W) carbide, wherein the tungsten (W) carbide is (W,Me) x Co y A cutting tool based on a cemented carbide, containing 0.5 to 2.5 volume% of a composite eta phase composed of C (where x and y are 3 to 12, and Me is at least two selected from Ta, Nb, Cr, Zn, Mo, Ti, and Al).

[0009] (2) A cutting tool based on a cemented carbide, wherein the amount of decarburization (X) of the cemented carbide base in (1) is -0.01 to -0.15 weight%.

[0010] (3) A cutting tool based on a cemented carbide, wherein the amount of demass (Y) of the cemented carbide base in (1) or (2) is -0.05 to -0.15 weight%.

[0011] (4) A cutting tool based on a cemented carbide, wherein in any one of (1) to (3), the amount of decarburization (X) + amount of demassification (Y) of the cemented carbide base is -0.06 to -0.20 weight%.

[0012] (5) A cutting tool based on a cemented carbide alloy, wherein in any one of (1) to (4), the average particle size of the tungsten carbide (WC) is 0.5 to 2.1 μm.

[0013] (6) A cutting tool based on a cemented carbide alloy, wherein in any one of (1) to (5), Me is two or more types selected from Ta, Nb, and Ti.

[0014] (7) A cutting tool based on a cemented carbide, wherein in any one of (1) to (6), a CFL layer is formed in the cemented carbide to a depth of 5 to 30 μm, and there is no composite eta phase in the CFL layer.

[0015] (8) A cutting tool comprising, in any one of (1) to (7), a hard film formed by chemical vapor deposition (CVD) on the surface of the cemented carbide, wherein the thickness of the hard film is 1 to 25 μm, and comprising at least one Ti(C,N) layer, an α-Al2O3 layer formed on the Ti(C,N) layer, and a TiN layer formed on the α-Al2O3 layer.

[0016] The cutting tool according to the present invention controls the formation of a composite eta phase by controlling the balance of decarburization amount and demass amount, thereby obtaining a cutting tool with improved resistance to crack formation and growth compared to conventional tools.

[0017] However, 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.

[0018] FIG. 1 schematically shows a cross-section of a cutting tool according to one embodiment of the present invention.

[0019] Figure 2 is a microstructure image of a cemented carbide prepared according to Comparative Example 1.

[0020] Figure 3 is a microstructure image of a cemented carbide prepared according to Comparative Example 3.

[0021] Figure 4 is a microstructure image of a cemented carbide prepared according to Example 1.

[0022] Figure 5 is a microstructure image of a cemented carbide prepared according to Example 3.

[0023] Figure 6 shows the results of the wear resistance evaluation of cutting tools manufactured according to Comparative Example 1 and Example 1.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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”.

[0029]

[0030] As illustrated in FIG. 1, a cutting tool according to one embodiment of the present invention comprises a substrate made of cemented carbide and a hard film formed on the substrate.

[0031] [Cemented Carbide]

[0032] The cemented carbide according to the present invention is a cutting tool comprising a cemented carbide substrate comprising 2 to 20 weight% of a binder comprising one or more of cobalt (Co), iron (Fe), and nickel (Ni), and 80 to 98 weight% of tungsten (W) carbide, wherein the tungsten (W) carbide is (W,Me) x Co y It is characterized by containing 0.5 to 2.5 volume% of a complex eta phase composed of C (where x, y are 3 to 12, and Me is two or more selected from Ta, Nb, Cr, Zn, Mo, Ti, and Al).

[0033] If the above binder is less than 2 weight%, the bonding strength for bonding the hard phase decreases and the toughness of the cemented carbide becomes excessively low, and if it exceeds 20 weight%, the wear resistance becomes excessively low due to a lack of wear-resistant hard phase, so it is preferable to include it in an amount of 2 to 20 weight%. More preferable content of the binder may be 2.5 to 15 weight%, 3 to 10 weight%, or 4 to 8 weight%.

[0034] The binder included in the above cemented carbide may be any of the iron-based metals cobalt (Co), iron (Fe), and nickel (Ni); however, since it may be preferable not to include iron (Fe) due to its low thermal conductivity, it may preferably be composed of cobalt (Co) or a combination of cobalt (Co) and nickel (Ni); and considering the toughness and thermal conductivity of the cemented carbide, it is more preferable for the binder to be composed of cobalt (Co).

[0035] If the above tungsten (W) carbide is included in an amount of less than 80 weight%, physical properties such as wear resistance required for cutting tools become excessively low, and if it is included in an amount exceeding 98 weight%, the amount of binder becomes excessively low, resulting in excessively low bonding strength and toughness, so it is desirable to include it in an amount of 80 to 98 weight%.

[0036] Among the above tungsten (W) carbides, it is preferable that tungsten carbide (WC), which is included as the main hard phase, be included in an amount of 79 to 97 weight percent. If tungsten carbide (WC) is included in an amount of less than 79 weight percent, physical properties such as wear resistance required for cutting tools become excessively low, and if tungsten carbide (WC) exceeds 97 weight percent, the proportion of other carbides and eta phases decreases excessively, thereby reducing the effect of inhibiting grain growth or resistance to crack formation and growth, so it is preferable that it be included in an amount of 79 to 97 weight percent.

[0037] The above tungsten (W) carbide is (W,Me) x Co y When the volume ratio of the composite eta phase composed of C (where x, y are 3 to 12, and Me is at least two selected from Ta, Nb, Cr, Zn, Mo, Ti, and Al) is less than 0.5% as a volume fraction, it is not sufficient to obtain resistance to cracking, and when it exceeds 2.5%, wear resistance decreases, so it may be 0.5 to 2.5%, preferably 1.0 to 2.0%, and more preferably 1.1 to 1.9%.

[0038] The above cemented carbide is characterized by having carbon (C) content and nitrogen (N) content controlled within a predetermined range. In the present invention, 'decarburization amount (X)' refers to the carbon content defined as the amount of carbon removed after sintering in the powder design, and 'demass amount (Y)' refers to the nitrogen content defined as the amount of nitrogen removed after sintering in the powder design. Carbon balance is an important factor for controlling the formation of the eta phase. However, in the present invention, the formation of the eta phase is controlled not by controlling the decarburization amount to exceed a certain value as in the prior art, but by simultaneously controlling the carbon balance and nitrogen balance. Through this, resistance to crack formation and growth can be further improved compared to the prior art. To control the carbon balance and nitrogen balance for the formation of the eta phase, the decarburization amount (X) is controlled to be -0.01 to -0.15 wt%, and the demass amount (Y) is controlled to be -0.05 to -0.15 wt%. If the decarburization amount (X) and demass amount (Y) fall outside the above range, it is undesirable because a microstructure having an eta phase sufficient to enhance resistance to crack formation and growth, which is the objective of the present invention, is not realized. Furthermore, it is more desirable for enhancing resistance to crack formation and growth to have the sum of the decarburization amount (X) and demass amount (Y) (X+Y) = -0.06 to -0.2 wt%. Additionally, it is preferable that the sum of the decarburization amount (X) and demass amount (Y) (X+Y) be -0.10 to -0.18 wt%, more preferable that it be -0.11 to -0.17 wt%, and most preferable that it be -0.12 to -0.16 wt%.

[0039] The particle size of the tungsten carbide (WC) included in the above cemented carbide may be 0.5 to 2.1 μm, and the EBSD WC particle size variation may be 1 μm. When the particle size and variation of the tungsten carbide are managed in this way, the size of the binder pocket formed in the cemented carbide becomes uniform, and the chipping resistance of the cutting tool can be improved.

[0040] (W,Me) formed in the above cemented carbide x Co y A composite eta phase composed of C (where x and y are 3 to 12, and Me is two or more selected from Ta, Nb, Cr, Zn, Mo, Ti, and Al) may include three or more metals including W and may have a higher hardness than the matrix phase, and preferably, Me may be two or more selected from Ta, Nb, and Ti. For example, the composite eta phase may include phases such as (W,Ta,Nb)3Co3C and (W,Ta,Ti,Nb)6Co6C.

[0041] In cemented carbide, the CFL (Cubic Phase Free Layer) layer is a layer in which no carbides, carbonitrides, or nitrides are present, and it serves to absorb external shocks during machining to suppress chipping. For this purpose, in one embodiment of the present invention, it is preferable to form it at a depth of 5 to 30 μm from the surface, and the composite eta phase may not be present within the CFL layer.

[0042]

[0043] [Hard film]

[0044] The above cemented carbide may further include a hard film formed by chemical vapor deposition (CVD) on its surface. The hard film may be formed as a single layer or a multilayer structure of two or more layers.

[0045] When the hard film has a multilayer structure, it may include a Ti carbonitride layer and an Al2O3 layer, and in this case, the hard film may be formed as a wear-resistant CVD coating layer comprising at least one Ti(C,N) layer, an α-Al2O3 layer formed on the Ti(C,N) layer, and a TiN layer formed on the α-Al2O3 layer.

[0046] If the total thickness of the hard film is less than 1㎛ or greater than 25㎛, it may be difficult to achieve the physical properties required for the hard film, so it is preferable that the thickness be 1 to 25㎛, and more preferable that the thickness of the hard film be 10 to 20㎛.

[0047]

[0048] <Example>

[0049] Co powder, WC powder, Ti(C,N) powder, Ta(C,N) powder, Nb(C,N) powder, and TaNbC powder (compound powder) were prepared, and a mixture was made according to the ratio of raw materials in Table 1 below.

[0050] Classification Raw Material Mixture (Weight%) W Co Ti Ta Cr N b CN Example 1 Bal.6 21 - 16.10 0.25 Example 2 Bal.6 21 - 16.10 0.25 Example 3 Bal.6 21 0.5 16.10 0.25 Example 4 Bal.7.5 21 - 16.00 0.25 Comparative Example 1 Bal.6 6.10 0.05 Comparative Example 2 Bal.6 21 - 16.10 0.10 Comparative Example 3 Bal.6 21 - 6.10 0.25

[0051] Manufacturing process of cemented carbide and hard coatings

[0052] The raw material powder prepared in the ratio of Table 1 above was milled for 8 hours to make a mixture, and then the slurry was pan-dried. Subsequently, the aggregate was pressurized to form a molded body, and this was sintered at 1420°C for 1 hour to manufacture a cemented carbide insert (substrate).

[0053] The phase that appears as the darkest color in the microstructure of the cemented carbide inserts shown in FIGS. 2 to 5 is the eta phase. The analysis results regarding the presence or absence of CFL and eta phase formation according to the amount of decarburization and demassification of the manufactured cemented carbide inserts are as shown in Table 2 below.

[0054] Classification Weight % CFL (㎛) Eta Phase Classification Powdered Carbon Sintered Carbon Decarburization Amount Powdered Nitrogen Sintered Body Nitrogen Demassage Amount Composition Volume % Example 16.10 6.05 -0.05 0.25 0.15 -0.1018 (W,Ti TaNb)6Co6C 1.3% Example 26.10 6.09 -0.01 0.25 0.13 -0.1220 (W,Ti TaNb)6Co6C 1% Example 36.10 6.00 -0.1 0.25 0.17 -0.0815 (W,Ti TaNbCr)6Co6C 2% Example 46.00 5.95 -0.05 0.25 0.15 -0.1022 (W,Ti TaNb)6Co6C 1.5% Comparative Example 16.106.00-0.10.050.050-W6Co6C0.3%Comparative Example 26.106.05-0.050.100.05018-Comparative Example 36.105.90-0.200.250.14-0.115W6Co6C5%

[0055] As shown in Table 2, the cemented carbide inserts according to Examples 1 to 4 of the present invention have a decarburization amount (X) of -0.01 to -0.1 wt%, a demass amount (Y) of -0.08 to -0.12 wt%, and X+Y maintained in the range of -0.15 to -0.18 wt%, the depth of the CFL layer is 15 to 22 μm, and the eta phase contains various metal components such as W, Ti, Ta, Nb or W, Ti, Ta, Nb and Cr in addition to Co and C, and contains 1 to 2 volume%.

[0056] In contrast, the cemented carbide inserts according to Comparative Examples 1 to 3 have a different amount of decarburization (X) or demassification (Y) compared to the embodiments of the present invention, and X+Y showed values ​​that were smaller or significantly larger than those of the embodiments of the present invention. In addition, in the case of Comparative Examples 1 to 3, there is no CFL layer or the depth of the CFL layer is 5 μm and 18 μm, and the eta phase contains only W in addition to Co and C, and contains 0.3 volume% and 5 volume%.

[0057] The results of measuring the hardness of the eta phase and basal phase formed in the manufactured cemented carbide insert using a microhardness tester are shown in Table 3 below.

[0058] Classification Ti (wg%) Ta (wg%) Cr (wg%) Nb (wg%) Eta phase volume Bi-eta phase Hardness (GPa) Base phase (Wc-Co phase) Hardness (GPa) Example 1 21-11 21.320 Example 3 210.5 11.5 21.920 Comparative Example 1 ----118.320 Comparative Example 2 21-1--20

[0059] As shown in Table 3, the hardness of the composite eta phase produced according to Examples 1 and 3 of the present invention is higher than that of the base phase, and the hardness of the eta phase produced according to Comparative Example 1 is lower than that of the base phase, and the higher hardness of the composite eta phase according to the embodiments of the present invention compared to the base phase affects the cutting performance of the cutting insert.

[0060] A hard film layer was formed on a cemented carbide substrate prepared according to Examples 1 to 4 and Comparative Examples 1 to 3 using a known CVD coating method. Specifically, a CVD coating layer including a thin TiN layer was formed by depositing a 10 μm thick Ti(C,N) layer at 800 to 1200°C, followed by depositing an 8 μm thick α-Al2O3 layer and a 1.2 μm thick TiN layer as the outermost layer.

[0061]

[0062] Cutting performance analysis

[0063] According to the examples and comparative examples, the wear resistance and impact resistance of a cutting tool having a hard film formed on a cemented carbide cutting insert were evaluated under the following two conditions.

[0064] [Wear Resistance Evaluation]

[0065] - vc=200

[0066] - F(feed rate, mm / rev)=0.4

[0067] - AP(cutting depth, mm)=2.0

[0068] - Workpiece: SCM440 (alloy steel)

[0069] [Impact Resistance Evaluation]

[0070] - vc=200

[0071] - F(feed rate, mm / rev)=0.2

[0072] - AP(Cutting depth, mm) 1.5

[0073] - Workpiece: SCR420-3R (alloy steel)

[0074]

[0075] Table 4 below shows the results of the wear resistance and impact resistance evaluations conducted under the above conditions.

[0076] Classification Wear Resistance (Wear amount, um) Impact Resistance (Number of passes until breakage) Example 1 1 20 15 Example 2 1 15 15 Example 3 1 10 14 Example 4 1 50 20 Comparative Example 1 20 10 Comparative Example 2 1 20 6 Comparative Example 3 2 50 3

[0077] As shown in Table 4 above, it can be seen that the cutting tools according to Examples 1 to 4 have significantly improved overall characteristics of wear resistance or impact resistance compared to the cutting tools according to Comparative Examples 1 to 3.

Claims

1. A cutting tool comprising a cemented carbide substrate comprising 2 to 20 weight% of a binder comprising one or more of cobalt (Co), iron (Fe), and nickel (Ni), and 80 to 98 weight% of tungsten (W) carbide, The above tungsten (W) carbide is (W,Me) x Co y A cutting tool based on a cemented carbide, containing 0.5 to 2.5 volume% of a composite eta phase composed of C (where x and y are 3 to 12, and Me is at least two selected from Ta, Nb, Cr, Zn, Mo, Ti, and Al).

2. In Paragraph 1, A cutting tool based on a cemented carbide, wherein the amount of decarburization (X) of the cemented carbide base is -0.01 to -0.15 weight%.

3. In Paragraph 1, A cutting tool based on a cemented carbide, wherein the demass (Y) of the cemented carbide base is -0.05 to -0.15 weight%.

4. In Paragraph 1, A cutting tool based on a cemented carbide, wherein the amount of decarburization (X) + amount of demassification (Y) of the cemented carbide base is -0.06 to -0.20 weight%.

5. In Paragraph 1, A cutting tool based on a cemented carbide alloy, wherein the average particle size of the tungsten carbide (WC) is 0.5 to 2.1 μm.

6. In Paragraph 1, A cutting tool based on a cemented carbide alloy, wherein the above Me is two or more types selected from Ta, Nb, and Ti.

7. In Paragraph 1, A cutting tool based on a cemented carbide, wherein a CFL layer is formed to a depth of 5 to 30 μm in the cemented carbide, and the composite eta phase is not present in the CFL layer.

8. In any one of paragraphs 1 through 7, The above cemented carbide further comprises a hard film formed by chemical vapor deposition (CVD) on its surface, and The thickness of the hard film is 1 to 25 μm, and A cutting tool comprising at least one Ti(C,N) layer, an α-Al2O3 layer formed on the Ti(C,N) layer, and a TiN layer formed on the α-Al2O3 layer.

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