Cutting tool comprising cemented carbide as base material

Abstract

The present invention relates to a cutting tool comprising a cemented carbide. The cutting tool, according to the present invention, comprises: a binder including at least one of cobalt (Co), iron (Fe), and nickel (Ni); tungsten carbide (WC); and a compound having a composition of Me (CxNy) (x+y=1, 0≤x≤1, 0≤y≤1), Me comprising at least one metal selected from groups 4, 5, and 6 metals excluding tungsten (W), wherein the cutting tool comprises a cemented carbide as a base material, the cemented carbide comprising the binder in an amount of 2 wt% to 20 wt%, the compound in an amount of 80 wt% to 98 wt%, and an eta phase containing M12C and / or M6C in an amount of 0.5 vol% to 2.5 vol%, and having a decarburization amount (X) of -0.01 wt% to -0.15 wt% and a denitrification amount (Y) of -0.05 wt% to -0.15 wt%.

Description

Cutting tools based on cemented carbide

[0001] The present invention relates to a cutting tool using a superhard alloy as a base material.

[0002]

[0003] Cemented carbide is a composite material manufactured by sintering metal carbides such as tungsten carbide (WC) and ferrous metals such as iron (Fe), nickel (Ni), and cobalt (Co) using powder metallurgy, and is widely used as a material for cutting tools.

[0004] When manufacturing these superalloys, if carbon is insufficient, the eta (η) phase is formed, and if carbon is excessive, free graphite is precipitated. The precipitated eta phase and free graphite are factors that deteriorate the properties of the cutting tool. For this reason, when manufacturing superalloys, the formation of eta phase or free graphite is generally prevented.

[0005] Meanwhile, Korean Patent Publication No. 2018-0095909 discloses a technology for increasing resistance to comb cracks, which have been a problem in cutting tools in the milling field, by increasing the tungsten (W) content in the binder phase included in the superalloy and simultaneously generating a controlled and well-distributed eta phase.

[0006]

[0007] The object of the present invention is to provide a cutting tool using a superalloy as a base material, which has improved resistance to crack formation and growth compared to conventional superalloys that have improved resistance to comb-shaped cracks by generating a controlled eta phase.

[0008] However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0009]

[0010] To solve the above problem, the present invention provides a cutting tool according to the following (1) to (8).

[0011] (1) Me(C) comprising a binder including at least one of cobalt (Co), iron (Fe), and nickel (Ni), tungsten carbide (WC), and at least one metal (Me) selected from among metals of Group 4, Group 5, and Group 6 excluding tungsten (W). x N y )(x+y=1, 0≤x≤1, 0≤y≤1) comprising a compound having a composition, wherein the binder comprises 2 to 20 wt%, the compound comprises 80 to 98 wt%, and M 12 A cutting tool based on a cemented carbide alloy containing 0.5 to 2.5 vol% of an eta phase including C and / or M6C, having a decarburization amount (X) of -0.01 to -0.15 wt%, and a denitrification amount (Y) of -0.05 to -0.15 wt%.

[0012] (2) In (1), the above M 12 A cutting tool, wherein the metal (M) constituting C and / or M6C is at least one selected from tungsten (W), molybdenum (Mo), tantalum (Ta), niobium (Nb), and cobalt (Co).

[0013] (3) A cutting tool comprising 0.05 to 2.0 volume% of the eta phase in (1) or (2).

[0014] (4) In any one of (1) to (3), Me(C) excluding the tungsten carbide (WC) x N y )(x+y=1, 0≤x≤1, 0≤y≤1) A cutting tool having a particle size of 1.0 to 2.0 ㎛ of a compound having a composition.

[0015] (5) A cutting tool in which a CFL (Cubic Phase Free Layer) is formed from the surface of the superalloy for cutting tools to a depth of 10 to 25 ㎛ in any one of (1) to (4).

[0016] (6) A cutting tool in any one of (1) to (5), wherein the nitrogen (N) content of the superalloy is 0.1 to 0.16 wt%.

[0017] (7) A cutting tool in any one of (1) to (6), wherein the sum (X+Y) of the decarbonization amount (X) and the demassification amount (Y) is -0.06 to -0.20 wt%.

[0018] (8) A cutting tool according to any one of (1) to (7), further comprising a hard film formed on the surface of the superalloy by a chemical vapor deposition (CVD) method, wherein the hard film has a thickness of 1 to 25 ㎛, and comprises 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.

[0019]

[0020] The cutting tool according to the present invention controls the formation of eta phases through balance control of the amount of decarburization and denitrification, thereby obtaining a cutting tool having improved resistance to crack formation and growth compared to a conventional cutting tool.

[0021] However, the effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the description below.

[0022]

[0023] Figure 1 schematically illustrates a cross-section of a cutting tool according to one embodiment of the present invention.

[0024] Figure 2 is a microstructure image of a superhard alloy manufactured according to Example 1.

[0025] Figure 3 is a microstructure image of a superhard alloy manufactured according to Comparative Example 1.

[0026] Figure 4 is a microstructure image of a superhard alloy manufactured according to Comparative Example 2.

[0027] Figure 5 is an image after cutting evaluation of a cutting insert manufactured from a superalloy according to Examples 1 to 3, Comparative Example 1, and Comparative Example 2.

[0028] Figure 6 shows the number of machining passes of cutting inserts manufactured from superalloy according to Examples 1 to 3, Comparative Example 1, and Comparative Example 2.

[0029] Figure 7 shows that the eta phase was detected through XRD analysis of the superalloy manufactured according to Example 1.

[0030]

[0031] Below, with reference to the attached drawings, embodiments of the present invention are described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0032] In addition, in order to clearly explain the invention in the drawings, parts unrelated to the explanation were omitted, and similar parts were given similar drawing symbols throughout the specification.

[0033] Throughout this specification, whenever a part is said to "include" a component, this means that it may include other components, but not to the exclusion of other components, unless otherwise specifically stated.

[0034] The terms "about," "substantially," and the like used in this specification are used in a meaning that is at or close to the numerical value when manufacturing and material tolerances inherent in the meanings mentioned are presented, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosure in which exact or absolute values ​​are mentioned to aid understanding of the present application.

[0035] Throughout this specification, the term "a combination of these" in a Markushi format expression means a mixture or combination of one or more selected from the group consisting of the components described in the Markushi format expression, and means including one or more selected from the group consisting of said components. Throughout this specification, the description of "A and / or B" means "A or B, or, A and B."

[0036] As illustrated in FIG. 1, a cutting tool according to one embodiment of the present invention comprises a substrate made of a cemented carbide alloy and a hard film formed on the substrate.

[0037]

[0038] [Superalloy]

[0039] The superalloy according to the present invention comprises a binder including at least one of cobalt (Co), iron (Fe) and nickel (Ni), and at least one metal (Me) selected from among metals of Group 4, Group 5 and Group 6 excluding tungsten carbide (WC) and tungsten (W). x N y )(x+y=1, 0≤x≤1, 0≤y≤1) contains a compound having the composition.

[0040] If the above-mentioned binder is included in an amount of less than 2 wt%, the bonding force for bonding the hard phase is reduced and the toughness of the cemented carbide is excessively reduced. If the amount exceeds 20 wt%, the wear resistance is excessively reduced due to a lack of a wear-resistant hard phase. Therefore, it is preferable to include the binder in an amount of 2 to 20 wt%. More preferable contents of the binder may be 2.5 to 15 wt%, 3 to 10 wt%, or 4 to 8 wt%.

[0041] The binder included in the above superalloy may use all of the iron-based metals cobalt (Co), iron (Fe), and nickel (Ni), but it may be preferable not to include iron (Fe) which has low thermal conductivity, and therefore may preferably be composed of cobalt (Co) or cobalt (Co) and nickel (Ni). Considering the toughness and thermal conductivity of the superalloy, it is more preferable that the binder be composed of cobalt (Co).

[0042] The above compound comprises tungsten carbide (WC) as a main hard phase, and at least one metal (Me) selected from metals of Group 4, Group 5, and Group 6 excluding tungsten (W). Me(C x N y )(x+y=1, 0≤x≤1, 0≤y≤1) compounds (i.e., metal (Me) carbide and / or metal (Me) carbonitride) are further included for the purpose of inhibiting grain growth or improving heat resistance.

[0043] If the above compound is included in an amount of less than 80 wt%, the physical properties required for the cutting tool, such as wear resistance, become excessively low, and if it is included in an amount exceeding 98 wt%, the amount of binder becomes excessively low, resulting in excessively low bonding strength and toughness. Therefore, it is preferable to include the compound in an amount of 80 to 98 wt%.

[0044] Among the above compounds, it is preferable that tungsten carbide (WC), which is included as a main hard phase, be included in an amount of 79 to 97 wt%. If tungsten carbide (WC) is included in an amount of less than 79 wt%, the physical properties required for the cutting tool, such as wear resistance, become excessively low, and if tungsten carbide (WC) exceeds 97 wt%, the ratios of tungsten carbide and eta phases become excessively low, which reduces the effect of inhibiting grain growth or resisting crack generation and growth. Therefore, it is preferable that tungsten carbide (WC) is included in an amount of 79 to 97 wt%.

[0045] In the above superalloy, the average grain size of tungsten carbide (WC) may be 0.1 to 12 ㎛, and is preferably 0.4 to 9 ㎛.

[0046] Except for the above tungsten carbide (WC), Me(C x N y )(x+y=1, 0≤x≤1, 0≤y≤1) The average particle size of the compound may be 1.0 to 2.0㎛.

[0047] In the above superalloy, 'eta phase' means M 12 It means a carbide phase having a composition of C and / or M6C, wherein M includes at least one metal selected from tungsten (W), tantalum (Ta), niobium (Nb) and cobalt (Co), and preferably, the eta phase may include all of tungsten (W), tantalum (Ta), niobium (Nb) and cobalt (Co).

[0048] In the above superalloy, if the eta phase is less than 0.5% in volume fraction, it is not sufficient to obtain resistance to cracks, and if it exceeds 2.5%, wear resistance decreases. Therefore, it may be 0.5 to 2.5%, preferably 1.0 to 2.0%, and more preferably 1.1 to 1.9%.

[0049] The above cemented carbide is characterized by having carbon content and nitrogen content controlled within a predetermined range. In the present invention, the 'decarburization amount (X)' refers to the carbon content defined as the amount of carbon lost after sintering in the powder design, and the 'mass removal amount (Y)' refers to the nitrogen content defined as the amount of nitrogen lost 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, rather than controlling the decarburization amount to exceed a certain value as in the prior art to generate the eta phase, the formation of the eta phase is controlled through simultaneous control of the carbon balance and the nitrogen balance. This can further improve the resistance to crack generation and growth compared to the prior art. For the carbon balance and nitrogen balance for controlling the formation of the eta phase, the decarburization amount (X) is controlled to be -0.01 to -0.15 wt%, and the mass removal amount (Y) is controlled to be -0.05 to -0.15 wt%. If the amount of decarburization (X) and the amount of demassification (Y) are outside the above range, a microstructure having an eta phase sufficient to improve the resistance to crack generation and growth, which is desired in the present invention, is not realized, which is not preferable. In addition, it is more preferable to make the sum of the amount of decarburization (X) and the amount of demassification (Y) (X+Y) = -0.06 to -0.2 wt% for improving the resistance to crack generation and growth.

[0050] In the above cemented carbide, the CFL (Cubic Phase Free Layer) layer is a layer free of carbides, carbonitrides, and nitrides. The CFL layer absorbs external impact during cutting, thereby suppressing chipping. For this purpose, in one embodiment of the present invention, it is preferably formed to a depth of 10 to 25 μm.

[0051] In the above superalloy, it is preferable to maintain the nitrogen (N) content at 0.1 wt% to 0.16 wt%, which allows the CFL layer to be formed to a thickness of 10 to 25 ㎛.

[0052]

[0053] [Hard film]

[0054] The surface of the above superalloy may further include a hard film formed by chemical vapor deposition (CVD). The hard film may be formed as a single layer or a multilayer structure of two or more layers.

[0055] When the hard film has a multilayer structure, it may include a Ti carbonitride layer and an Al2O3 layer, and at this time, the hard film may be formed as a wear-resistant CVD coating layer including 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.

[0056] If the total thickness of the above hard film is less than 1 ㎛ or more than 25 ㎛, it may be difficult to implement the properties required for the hard film, so it is preferably 1 to 25 ㎛, and a more preferable thickness of the hard film is 10 to 20 ㎛.

[0057]

[0058] <Examples and Comparative Examples>

[0059] Co powder, WC powder, Ti(C,N) powder, Ta(C,N) powder, Nb(C,N) powder, and TaNbC powder were prepared and mixed to produce a mixture with the composition shown in Table 1 below.

[0060] Classification W (wt%) Co (wt%) Ti (wt%) Ta (wt%) Nb (wt%) C (wt%) N (wt%) Example 1 Bal. 52116.100.25 Example 2 Bal. 52116.100.25 Example 3 Bal. 52116.100.25 Comparative Example 1 Bal. 52116.100.05 Comparative Example 2 Bal. 52116.100.25

[0061] The mixed powder prepared in Table 1 above was milled for 8 hours, and then the slurry was pan-dried. The agglomerates were then pressed to form a green body, which was then sintered at 1,420°C for 1 hour to form a sintered body.

[0062]

[0063] Microstructure of cemented carbide sintered body

[0064] Figures 2 to 3 are microstructure images of superhard alloys manufactured according to Example 1, Comparative Example 1, and Comparative Example 2, respectively.

[0065] As shown in Fig. 2, it can be seen that the superalloy sintered body according to Example 1 was mostly produced in a state in which the eta phase having a size of 0.5 to 3 μm was evenly dispersed. It was confirmed that Examples 2 and 3 also had similar microstructures.

[0066] Table 2 below shows the results of measuring the size and fraction of the eta phase generated in the microstructure of the superalloy sintered bodies according to Examples 1 to 3 and Comparative Examples 1 and 2.

[0067] Average size of the particles (um) Composition volume fraction (%) Example 12M 12 C and M6C1.3 Example 21.8M 12 C and M6C0.6 Example 32.3M 12 C and M6C1.9 Comparative Example 1---Comparative Example 28M 12 C and M6C4

[0068] As shown in Table 2 and Fig. 7 above, the generated eta phase is M 12 C phase and M6C phase were precipitated simultaneously. Unlike Examples 1 to 3, the superalloy sintered body of Comparative Example 1 did not form an eta phase, and it was confirmed that the superalloy sintered body of Comparative Example 2 formed a coarse eta phase compared to Examples 1 to 3.

[0069] Table 3 below shows the results of measuring the decarbonization amount and denitrification amount of the above sintered body.

[0070] Classification Weight % Powder Carbon Sintering Carbon Decarburization (X) Powder Nitrogen Sintering Nitrogen Decarburization (Y) X+Y Example 16.106.05-0.050.250.15-0.10-0.15 Example 26.106.09-0.010.250.13-0.12-0.13 Example 36.106.00-0.10.250.17-0.08-0.108 Comparative Example 16.106.05-0.050.050-0.05 Comparative Example 26.105.90-0.200.250.14-0.11-0.31

[0071] As shown in Table 3, Examples 1 to 3 all measured the decarbonization amount (X) to be -0.01 to -0.15 wt%, the mass removal amount (Y) to be -0.05 to -0.15 wt%, and X+Y to be -0.06 to -0.2 wt%. In contrast, Comparative Example 1 measured the mass removal amount (Y) to be 0 wt%, and Comparative Example 2 measured the decarbonization amount (X) to be -0.20 wt%, the mass removal amount (Y) to be -0.11 wt%, and X+Y to be -0.31 wt%. That is, it can be seen that Comparative Example 1 and Comparative Example 2 have different ranges of the decarbonization amount (X), mass removal amount (Y), and their sum when compared to the present invention.

[0072]

[0073] Cutting performance evaluation

[0074] A hard film consisting of a four-layer structure of TiN - Ti(C,N) - α-Al2O3 - TiN was formed on the insert manufactured with the above-mentioned superalloy sintered body through a known CVD process. At this time, the TiN layer as the base layer was formed with a thickness of 0.5 μm, the Ti(C,N) layer was formed with a thickness of 8 μm, the α-Al2O3 layer was formed with a thickness of 8 μm, and the TiN layer as the outermost layer was formed with a thickness of 1.2 μm. The cutting performance of the cutting tool having the hard film formed as described above was evaluated under the following two evaluation conditions.

[0075]

[0076] - Evaluation Criteria 1 -

[0077] Vc (cutting speed) = 300 m / min

[0078] F(feed speed)=0.2 mm / rev

[0079] AP(cutting depth)=2.0 mm

[0080] Workpiece material: SCM440 (alloy steel)

[0081]

[0082] - Evaluation Criteria 2 -

[0083] Vc (cutting speed) = 200 m / min

[0084] F(feed speed)=0.2 mm / rev

[0085] AP(cutting depth)=2.0 mm

[0086] Workpiece material: SCR420-3R (alloy steel)

[0087]

[0088] Figure 5 shows the results of evaluating the wear resistance of Examples 1 to 3 and Comparative Examples 1 and 2 under evaluation condition 1. In Figure 5, time is the time required until breakage.

[0089] As confirmed in Fig. 5, the cutting tools according to Examples 1 to 3 had a significantly longer lifespan than the cutting tools according to Comparative Example 2 in which a coarse eta phase was formed, and showed a level equivalent to that of Comparative Example 1 in which an eta phase was not formed.

[0090] Figure 6 shows the results of evaluating the impact resistance of Examples 1 to 3 and Comparative Examples 1 and 2 under evaluation condition 2. The numbers shown in Figure 6 are the passes required until damage due to impact.

[0091] As confirmed in Fig. 6, the cutting tools according to Examples 1 to 3 showed significantly higher impact resistance than Comparative Example 1 in which no eta phase was formed, and showed an equivalent level to Comparative Example 2 in which a coarse eta phase was formed.

[0092] From the above results, it can be seen that the cutting tool according to the embodiment of the present invention can achieve improved cutting tool life by achieving both wear resistance and impact resistance.

Claims

1. Me(C) comprising a binder including at least one of cobalt (Co), iron (Fe) and nickel (Ni), tungsten carbide (WC), and at least one metal (Me) selected from among metals of Group 4, Group 5 and Group 6 excluding tungsten (W). x N y )(x+y=1, 0≤x≤1, 0≤y≤1) containing a compound having a composition, The above binder comprises 2 to 20 wt%, The above compound comprises 80 to 98 wt%, M 12 Containing 0.5 to 2.5 volume % of eta phase containing C and / or M6C, A cutting tool using a cemented carbide as a substrate having a decarburization amount (X) of -0.01 to -0.15 wt% and a mass loss amount (Y) of -0.05 to -0.15 wt%.

2. In paragraph 1, Above M 12 A cutting tool, wherein the metal (M) constituting C and / or M6C is at least one selected from tungsten (W), molybdenum (Mo), tantalum (Ta), niobium (Nb), and cobalt (Co).

3. In paragraph 1, A cutting tool comprising 0.05 to 2.0 volume% of the above eta phase.

4. In paragraph 1, Except for the above tungsten carbide (WC), Me(C x N y )(x+y=1, 0≤x≤1, 0≤y≤1) A cutting tool having a particle size of 1.0 to 2.0 ㎛ of a compound having a composition.

5. In paragraph 1, A cutting tool in which a CFL (Cubic Phase Free Layer) is formed at a depth of 10 to 25 ㎛ on the surface of the cemented carbide for the cutting tool.

6. In paragraph 1, A cutting tool having a nitrogen (N) content of 0.1 to 0.16 wt% of the above cemented carbide.

7. In paragraph 1, A cutting tool, wherein the sum (X+Y) of the above decarburization amount (X) and demassification amount (Y) is -0.06 to -0.20 wt%.

8. In any one of paragraphs 1 to 7, It further includes a hard film formed on the surface of the above superalloy by chemical vapor deposition (CVD), The thickness of the above hard film is 1 to 25 ㎛, 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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