Cemented carbide, coated cemented carbide, and cutting tools and wear-resistant components made from them

Abstract

To provide a cemented carbide having larger deflective strength than conventional cemented carbide and excellent wear resistance.SOLUTION: A cemented carbide contains a hard phase having WC as a main component by 30.0 to 99.3wt% for the whole cemented carbide, contains a grain growth inhibiting and dispersion phase having solid solution or composite containing Ti (C,N) which is created by carbonitriding an oxide of Ti during sinter and either TaC or NbC as a main component, by 0.2 to 40.0wt% for the whole cemented carbide, and contains a binding phase having at least one kind selected from the group consisting of Co,Ni and Fe as a main component by 0.5 to 30.0wt% for the whole cemented carbide, where the total amount of the hard phase, grain growth inhibiting and dispersion phase, and binding phase is 100wt%.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a cemented carbide, a coated cemented carbide, and a cutting tool and a wear-resistant member using the same. [Background technology]

[0002] Cemented carbide is widely used as a wear-resistant component for cutting tools (e.g., drills, end mills, insert chips), dies, plugs, nozzles, molding dies, etc. for metal materials such as steel, cast iron, manganese steel, and stainless steel. Cemented carbide containing tungsten carbide (hereinafter referred to as "WC") as its main component, which forms a mechanically stable hard phase, is particularly widely used.

[0003] To produce cemented carbide, simply sintering WC with a binder metal such as cobalt (Co) causes grain growth, which reduces the hardness of the resulting cemented carbide. To inhibit the grain growth of WC and prevent a decrease in the hardness of the resulting cemented carbide, various grain growth inhibitors such as vanadium carbide (VC), chromium carbide (Cr3C2), and tantalum carbide (TaC) are used.

[0004] Patent Document 1 discloses a cemented carbide with excellent hardness that contains tungsten carbide (WC), titanium carbonitride (Ti(C,N)), and cobalt (Co). Ti(C,N) contributes to inhibiting the grain growth of WC. By effectively inhibiting the grain growth of WC particles, a cemented carbide with high hardness can be obtained. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-98393 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a cemented carbide alloy having superior transverse rupture strength compared to conventional cemented carbide alloys.

[0007] Another object of the present invention is to provide a cemented carbide having superior wear resistance compared to conventional cemented carbide.

[0008] Another object of the present invention is to provide a cutting tool and a wear-resistant member that are excellent in wear resistance. [Means for solving the problem]

[0009] The cemented carbide of the present invention is characterized in that it contains 30.0 to 99.3 wt% of a hard phase mainly composed of tungsten carbide (WC) based on the entire cemented carbide, 0.2 to 40.0 wt% of a grain growth inhibitor and dispersed phase mainly composed of a solid solution or composite containing titanium carbonitride (Ti(C,N)) produced by carbonitriding titanium (Ti) oxide during sintering and at least one of tantalum carbide (TaC) and niobium carbide (NbC), and 0.5 to 30.0 wt% of a binder phase mainly composed of at least one element selected from the group consisting of cobalt (Co), nickel (Ni) and iron (Fe), with the total of the hard phase, grain growth inhibitor and dispersed phase and binder phase being 100 wt%. It goes without saying that cemented carbide may contain unavoidable impurities, i.e., impurities that are present in raw materials or that are inevitably mixed in during the manufacturing process and are essentially unnecessary, but are tolerated because they are present in trace amounts and do not affect the properties of the product. A "solid solution" is a state in which the entire material is a uniform solid phase, that is, a state in which it is in one phase. A "composite" is a state in which multiple solid phases are bonded to each other, but are not in a uniform solid phase.

[0010] The cemented carbide of this invention contains three types of phases: a "hard phase" (first phase), a "grain growth inhibiting and dispersed phase" (second phase), and a "binding phase" (third phase). The total of these three phases is 100 wt%.

[0011] The cemented carbide according to the present invention contains tungsten carbide (WC) as a hard phase (first phase) in an amount of 30.0 to 99.3 wt% based on the entire cemented carbide, and a binder phase (third phase) containing at least one element selected from the group consisting of cobalt (Co), nickel (Ni), and iron (Fe) as a main component in an amount of 0.5 to 30.0 wt% based on the entire cemented carbide. The binder phase bonds the hard phases together. The tungsten carbide (WC) as the hard phase is preferably fine particles with an average particle size of 2.0 μm or less. Compared to when the average particle size is 2.0 μm or more, the hardness is higher and wear resistance is improved.

[0012] In addition to the "hard phase" and "binder phase," the cemented carbide of this invention also contains a "grain growth inhibitor and dispersed phase." The "grain growth inhibitor and dispersed phase" is a phase that inhibits the grain growth of the above-mentioned hard phase, tungsten carbide (WC), and is dispersed in the cemented carbide so that it does not crystallize or remain in the structure. In this invention, the "grain growth inhibitor and dispersed phase" is a solid solution or complex containing titanium carbonitride (Ti(C,N)) and at least one of tantalum carbide (TaC) and niobium carbide (NbC). That is, it includes a solid solution or complex consisting of Ti(C,N) and TaC, a solid solution or complex consisting of Ti(C,N) and NbC, and a solid solution or complex consisting of Ti(C,N), TaC, and NbC.

[0013] Tantalum carbide (TaC) and niobium carbide (NbC) are both carbides that have been conventionally used to inhibit grain growth of tungsten carbide (WC). Titanium carbonitride (Ti(C,N)) is a carbonitride for inhibiting grain growth that is adopted in place of tantalum carbide (TaC) and niobium carbide (NbC) in the above-mentioned Patent Document 1.

[0014] The inventors discovered that by using (combining) both TaC and / or NbC with Ti(C,N) rather than replacing TaC and NbC with Ti(C,N), WC growth can be suppressed. Furthermore, a cemented carbide can be produced with little or no crystallization or residual TaC, NbC, or Ti(C,N), i.e., without abnormal structures. The TaC, NbC, and Ti(C,N) are well dispersed, resulting in the prevention, elimination, or reduction of abnormal structures that degrade the properties of cemented carbide, thereby improving the properties of the final cemented carbide. In this sense, the combination of TaC and / or NbC with Ti(C,N) is referred to as "grain growth suppression and dispersed phase." Measurements of the transverse rupture strength of the cemented carbide without abnormal structures according to this invention confirmed that it achieved a transverse rupture strength superior to that of cemented carbides produced using either TaC, NbC, or Ti(C,N). It was also confirmed that the hardness could be maintained at least at the same level (in some cases, it was even improved).

[0015] When producing cemented carbide, Ti(C,N) itself is not used as the starting material, but titanium (Ti) oxide (TiO2) is used as the starting material. Fine Ti(C,N) particles are obtained by carbonitriding TiO2 during sintering, and it is thought that the inclusion of this in cemented carbide effectively suppresses the grain growth of WC.

[0016] As with Ti(C,N), TaC and NbC can be produced by carbonizing Ta (tantalum) oxide (Ta2O5) or Nb (niobium) oxide (Nb2O5) during sintering, or TaC or NbC can be used as the starting material. It is also possible to use tantalum oxide (Ta2O5) and NbC (niobium carbide), or tantalum carbide (TaC) and niobium oxide (Nb2O5) as the starting materials. However, it has been confirmed that the flexural strength is higher when Ta2O5 or Nb2O5 (oxides) are used as starting materials than when TaC or NbC (carbides), so when flexural strength is important, it is better to use Ta2O5 or Nb2O5 (oxides).

[0017] This invention can also be defined as follows: The cemented carbide according to this invention comprises a hard phase mainly composed of tungsten carbide (WC), a binder phase mainly composed of at least one element selected from the group consisting of cobalt (Co), nickel (Ni) and iron (Fe), and a grain growth inhibitor and dispersed phase mainly composed of a solid solution or composite containing titanium carbonitride (Ti(C,N)) produced by carbonitriding an oxide of titanium (Ti) during sintering, and at least one of tantalum carbide (TaC) and niobium carbide (NbC), and is characterized in that the grain growth inhibitor and dispersed phase (the solid solution or composite) are uniformly dispersed throughout the structure.

[0018] The present invention can also be further defined as follows: The cemented carbide according to the present invention comprises a hard phase primarily composed of tungsten carbide (WC), a binder phase primarily composed of at least one element selected from the group consisting of cobalt (Co), nickel (Ni) and iron (Fe), and a grain growth inhibitor and dispersed phase primarily composed of a solid solution or composite containing titanium carbonitride (Ti(C,N)) produced by carbonitriding an oxide of titanium (Ti) during sintering, and at least one of tantalum carbide (TaC) and niobium carbide (NbC), and is characterized by the absence of a crystallized texture or residual texture of the grain growth inhibitor and dispersed phase (the solid solution or composite).

[0019] As mentioned above, in cemented carbide containing a solid solution or complex consisting of both TaC and / or NbC and Ti(C,N), the solid solution or complex is uniformly dispersed throughout the structure, and no crystallized structure (patterned structure) or residual structure is observed. When measured for transverse rupture strength, it is superior to cemented carbide containing TaC, NbC, or Ti(C,N) alone, and its hardness is equal to or greater than that of the cemented carbide.

[0020] In one embodiment, chromium carbide (Cr3C2) is contained in an amount of 0.1 to 20.0 wt% relative to the entire binder phase, which can increase the hardness and transverse rupture strength of the cemented carbide.

[0021] In another embodiment, the content of TaC / (Ti(C,N)+TaC) (wt%) is 0.10 to 0.50 relative to the total cemented carbide. It has been confirmed that the transverse rupture strength of cemented carbide can be increased by including Ti(C,N) and TaC in the grain growth inhibiting and dispersed phase containing both Ti(C,N) and TaC at the above content ratio. The same is thought to be true when NbC is used instead of TaC, or when both TaC and NbC are used.

[0022] Preferably, in the above-mentioned content ratio of Ti(C,N) and TaC, the content of Ti(C,N) is 0.90 to 2.60 wt% relative to the entire cemented carbide. It has been confirmed that by keeping the content of Ti(C,N) within this range, the transverse rupture strength of the cemented carbide can be reliably increased.

[0023] The present invention also provides a coated cemented carbide in which a hard coating is coated on the above-mentioned cemented carbide by physical vapor deposition (PVD) or chemical vapor deposition (CVD).

[0024] Specifically, the hard coating uses at least one selected from the group consisting of TiC, TiN, TiAlN, TiSiN, and Ti(C,N). As mentioned above, cemented carbide contains Ti(C,N). Carbide, nitride, carbonitride, or oxide of Ti, which is the same element contained in Ti(C,N), is considered to be suitable for a hard coating that adheres well to the substrate (base material) that constitutes the coated cemented carbide of this invention.

[0025] In one embodiment, an Al-containing carbide, nitride, carbonitride, or oxide, or a composite material thereof, is laminated on the base of the hard coating or on the surface of the hard coating, and these may be laminated in not only two layers but also three or more layers.

[0026] The present invention also provides cutting tools (for example, drills, insert chips) or wear-resistant tools (for example, dies, molds) made of the above-mentioned cemented carbide or coated cemented carbide. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a flowchart showing an example of a manufacturing process for a cemented carbide tool. [Figure 2] 1 is a flowchart showing an example of a manufacturing process for a cemented carbide tool. [Figure 3] 1 is a graph showing the relationship between the TaC content and the average transverse rupture strength for a cemented carbide produced using Ta2O5 as a starting material and a cemented carbide produced using TaC as a starting material. [Figure 4] 1 is a graph showing the relationship between the TaC content and the average transverse strength for a cemented carbide containing Ti(C,N) and a cemented carbide not containing Ti(C,N). [Figure 5] 1 is a graph showing the average transverse rupture strength when the content ratio of Ti(C,N) to TaC is changed in a cemented carbide containing both Ti(C,N) and TaC. [Figure 6] 1 is a graph showing the relationship between the crystallized region and the residual region with increasing or decreasing Co content and TaC content. [Figure 7] 1 is an optical microscope photograph of a conventional cemented carbide containing TaC. [Figure 8] 1 is an optical microscope photograph of a conventional cemented carbide containing TaC and NbC. [Figure 9] 1 is an optical microscope photograph of cemented carbide sample No. 61. [Figure 10] 1 is an optical microscope photograph of cemented carbide sample No. 62. [Figure 11] 1 is an optical microscope photograph of cemented carbide sample No. 63. [Figure 12] 1 is an optical microscope photograph of cemented carbide sample No. 64. [Figure 13] 1 is an optical microscope photograph of Sample No. 63, a cemented carbide experimentally produced by maintaining the Co content and doubling the TaC content. [Figure 14] 1 is an optical microscope photograph of Sample No. 64, a cemented carbide experimentally produced by maintaining the Co content and doubling the TaC content. [Figure 15]1 is a scanning electron microscope photograph of cemented carbide sample No. 61. [Figure 16] 1 is a scanning electron microscope photograph of cemented carbide sample No. 62. [Figure 17] 1 is a scanning electron microscope photograph of cemented carbide sample No. 63. [Figure 18] 1 is a scanning electron microscope photograph of the cemented carbide sample No. 64. [Figure 19] FIG. 2 is an enlarged perspective view of the tip portion of the drill. [Figure 20] FIG. 2 is an enlarged perspective view of an insert chip. [Figure 21] 1 shows the results of a drilling test using a drill made of an uncoated cemented carbide. [Figure 22] 1 shows the results of a drilling test using a drill made of an uncoated cemented carbide. [Figure 23] 1 shows the results of a drilling test using a drill made of an uncoated cemented carbide. [Figure 24] 1 shows test results of a drilling test using a drill made using a coated cemented carbide. [Figure 25] 1 shows test results of a drilling test using a drill made using a coated cemented carbide. [Figure 26] 1 shows test results of a drilling test using a drill made using a coated cemented carbide. [Figure 27] 1 shows the test results of a turning test using an insert tip made of a coated cemented carbide. DETAILED DESCRIPTION OF THE INVENTION

[0028] The cemented carbide according to the embodiment of the present invention is a so-called tungsten carbide-based cemented carbide, which includes a first phase (hereinafter referred to as the "WC phase" or collectively referred to as the "hard phase") whose main component is tungsten carbide (WC), a second phase (hereinafter referred to collectively referred to as the "grain growth inhibiting and dispersed phase") whose main component is a solid solution or complex of titanium carbonitride (Ti(C,N)) and at least one of tantalum carbide (TaC) and niobium carbide (NbC), and a third phase (hereinafter referred to collectively referred to as the "binder phase") whose main component is cobalt (Co), nickel (Ni) or iron (Fe), or an alloy thereof.

[0029] As will be explained in more detail later, titanium carbonitride (Ti(C,N)) is not used as the starting material; instead, titanium oxide (TiO2) is used. Titanium oxide (TiO2) is carbonitrided during the sintering process, which is one of the processes used to manufacture cemented carbide, to produce titanium carbonitride (Ti(C,N)), which becomes one of the components of the final cemented carbide. Tantalum carbide (TaC), niobium carbide (NbC), or tantalum carbide (TaC) and niobium carbide (NbC) can be produced by using tantalum oxide (Ta2O5) or niobium oxide (Nb2O5) as the starting material and carbonizing it during sintering, or tantalum carbide (TaC) or niobium carbide (NbC) can be used as the starting material.

[0030] (1) Content of hard phase (WC phase) The WC phase is contained in an amount of 30.0 to 99.3 wt% of the entire cemented carbide. If the WC phase is less than 30.0 wt%, the proportion of the binder phase increases relatively, which can make it difficult to control the grain growth of the WC phase (grain growth of the WC phase will be described later). By containing 30.0 wt% or more of the WC phase, the grain growth of the WC phase is effectively suppressed, and the average WC grain size after sintering can be maintained fine, for example, at 2.0 μm or less. Furthermore, if the WC phase exceeds 99.3 wt%, the proportion of the binder phase decreases relatively, and the flexural strength of the cemented carbide decreases. By keeping the WC phase at 99.3 wt% or less, the flexural strength of the cemented carbide can be ensured to be above a specified value. The proportion of the WC phase in the entire cemented carbide is adjusted by the amount of WC raw material powder mixed.

[0031] (2) Grain growth inhibition and dispersed phase content As mentioned above, one of the reasons for including grain growth inhibitors and dispersed phases is to inhibit the grain growth of the WC phase and maintain the WC phase at a fine size (less than 2.0 μm). Grain growth of the WC phase is a phenomenon in which the WC phase dissolved in the binder phase during sintering grows into particles with a large diameter by precipitating into other WC phases. By adding Ti(C,N), TaC, and NbC, Ti(C,N), TaC, and NbC are scattered around the WC phase, which is thought to reduce the precipitation of the WC phase and inhibit the grain growth of the WC phase.

[0032] Ti(C,N) has a large effect of inhibiting the grain growth of WC. Like the above-mentioned Ti(C,N), TaC and NbC also exhibit an inhibitory effect on the grain growth of the WC phase, but rather than inhibiting grain growth, when combined with Ti(C,N), they have the effect of normalizing the cemented carbide structure (preventing, eliminating, or reducing the occurrence of abnormal structures). As a result, the hardness of the cemented carbide is improved. Combinations of Ti(C,N) and TaC, Ti(C,N) and NbC, or Ti(C,N), TaC, and NbC form cemented carbide as solid solutions or composites. The results of the structural observations and hardness measurements will be described later.

[0033] The grain growth inhibitors and dispersed phases are adjusted to an amount suitable for effectively inhibiting the grain growth of the WC phase, i.e., 0.2 wt% or more relative to the total cemented carbide, and an amount at which crystallization or residue of the grain growth inhibitors and dispersed phases does not or is unlikely to occur, i.e., 40.0 wt% or less. The proportion of the grain growth inhibitors and dispersed phases relative to the total cemented carbide can also be adjusted by the blending amounts of the starting materials described below.

[0034] As mentioned above, Ti(C,N) is not used as a starting material; instead, TiO2 is used as the starting material and is produced by carbonitriding it during sintering. This is to ensure that the final cemented carbide product contains fine grain growth inhibitors and dispersed phases, effectively inhibiting the grain growth of the WC phase with a small content. The grain growth inhibitors and dispersed phases (e.g., solid solutions or composites of Ti(C,N) and TaC) preferably have an average particle size in the range of 5 to 500 nm. On the other hand, TaC or NbC may be produced during sintering using oxides as starting materials, as with Ti(C,N), or TaC or NbC itself may be used as the starting material.

[0035] (3) Binder phase content The binder phase is used to bond the WC particles together.

[0036] The binder phase can be made of cobalt (Co), nickel (Ni), or iron (Fe), or an alloy made of these metals. The binder phase is a metal whose main component is one of these metal elements (containing 50.0 wt% or more of the entire binder phase).

[0037] If the binder phase is less than 0.5 wt%, the transverse rupture strength of the cemented carbide decreases, and if it exceeds 30.0 wt%, the hardness of the cemented carbide decreases. From these perspectives, the binder phase content of cemented carbide is set at 0.5 to 30.0 wt%. The binder phase firmly bonds the WC particles together, preventing them from falling off the cemented carbide and ensuring the strength of the cemented carbide. The proportion of the binder phase in the entire cemented carbide can also be adjusted by the amount of raw material powder mixed.

[0038] (4) Chromium carbide (Cr3C2) content Cr3C2 is used to inhibit the grain growth of the WC phase and the growth of the carbonitride phase. Cr3C2 is also known to contribute to improving the hardness and oxidation resistance of the binder phase. By setting the Cr3C2 content to between 0.1 wt% and 20.0 wt% of the entire binder phase, Cr3C2 can be sufficiently dissolved in the binder phase.

[0039] (5) Tantalum carbide (TaC) content TaC is used to suppress the grain growth of the WC phase and to disperse the solid solution or complex in the structure by combining it with the above-mentioned titanium carbonitride (Ti(C,N)) to form a solid solution or complex. By setting the content to 0.1 wt% or more and 7.0 wt% or less of the entire binder phase, it is possible to achieve dispersion of the solid solution or complex without significantly reducing the hardness of the cemented carbide.

[0040] (6) Niobium carbide (NbC) content Niobium carbide (NbC), which can be used in place of TaC, also has a suitable content of about 0.1 to 7.0 wt% relative to the entire binder phase, similar to TaC.

[0041] Both TaC and NbC can be used. In this case, the total amount of TaC and NbC is 0.1 to 7.0 wt% of the entire binder phase.

[0042] The manufacturing process of a cemented carbide tool using cemented carbide will be explained briefly below. Fig. 1 is a flowchart showing an example of the manufacturing process of a cemented carbide tool. Here, an example will be explained in which a metal containing cobalt (Co) as the main component is used as the binder phase.

[0043] Predetermined amounts of raw material powders of tungsten carbide (WC) 11, titanium oxide (TiO2) 12, tantalum oxide (Ta2O5) 13 (niobium oxide (Nb2O5) is also acceptable, and the same applies below), cobalt (Co) 14, chromium carbide (Cr3C2) 15, and carbon (C) 16 are placed in a cylindrical container, and a large number of small-diameter balls made of cemented carbide are also placed in the cylindrical container, and the cylindrical container is rotated. The raw material powders are crushed and mixed in the container (step 21) (ball mill). To improve the crushing effect and prevent oxidation of the powder, organic solvents such as acetone, alcohol, and hexane are also placed in the cylindrical container, which turns the raw material powders into a slurry (mud-like) in the cylindrical container.

[0044] The pulverized and mixed raw material powder in a slurry state is then dried by a spray dryer method, a mixer drying method, or the like, thereby removing the organic solvent from the raw material powder (step 22).

[0045] The pulverized and mixed raw material powder from which the organic solvent has been removed is pressed (compacted) by metal molding, rubber molding, extrusion molding, or the like, and formed into a predetermined shape (step 23).

[0046] The molded product is sintered in a heating furnace in which nitrogen gas is controlled at a predetermined partial pressure (step 24). By sintering the molded product at a temperature above the ternary eutectic temperature of W-Co-C (tungsten-cobalt-carbon), a cemented carbide alloy (here, WC-Ti(C,N)-TaC-Cr3C2-Co) with WC11 as the hard phase and Co14 as the binder phase is obtained.

[0047] As described above, carbon (C)16 is blended into the pulverized and mixed raw material powders, and the heating furnace is in a nitrogen atmosphere, so TiO212, one of the raw material powders, is carbonitrided in the heating furnace, producing Ti(C,N) as described above. Tantalum oxide (Ta2O5) has a weak bonding strength with nitrogen (N) in tantalum (Ta), so it bonds with carbon but not with nitrogen. Tantalum carbide (TaC) is produced from tantalum oxide (Ta2O5) by sintering (step 24).

[0048] Cemented carbide can contain tiny pores. To remove these pores, HIP (Hot Isostatic Pressing) is performed (Step 25). For example, argon gas at a pressure of 5 to 100 MPa is applied, which removes the pores.

[0049] Finally, shaping, coating, etc. are carried out to manufacture cemented carbide tools (cutting tools, cutting tools, wear-resistant tools, etc.) using the cemented carbide (step 26).

[0050] Figure 2 shows another example of a manufacturing process for cemented carbide tools using cemented carbide. This differs from the manufacturing process shown in Figure 1 in that tantalum carbide (TaC) 13A is used as the starting material instead of tantalum oxide (TaO) 13. In this case, too, titanium carbonitride (Ti(C,N)) is produced from titanium oxide (TiO) 12 in the sintering process (step 24).

[0051] Table 1 shows the hardness and average transverse rupture strength measurements for cemented carbide samples (i–iv) manufactured using tantalum oxide (Ta2O5)13 as the starting material, i.e., manufactured according to the flowchart shown in Figure 1, and cemented carbide samples (v–viii) manufactured using tantalum carbide (TaC)13A as the starting material, i.e., manufactured according to the flowchart shown in Figure 2. Samples i–iv and v–viii were manufactured with different tantalum carbide (TaC) contents (0.25–1.00 wt%), while the WC grain size (0.4 μm), Ti(C,N) content (1.3 wt%), Cr3C2 content (0.2 wt%), and Co content (10 wt%) were the same for all samples.

[0052] [Table 1]

[0053] Figure 3 shows the measurement results of Table 1 in a graph with the TaC content on the horizontal axis and the average transverse rupture strength on the vertical axis.

[0054] As described above, the cemented carbide shown in this example can be manufactured using either Ta2O513 (Figure 1) or TaCl3A (Figure 2) as the starting material. However, when the hardness and average transverse rupture strength of the manufactured cemented carbide were measured, as is clear from the graph in Figure 3, a large difference in average transverse rupture strength was observed. The cemented carbide manufactured using Ta2O513 as the starting material (samples i-iv) had a higher average transverse rupture strength than the cemented carbide manufactured using TaCl3A as the starting material (samples v-viii). It is known that average transverse rupture strength is affected by the grain size (particle size) of the hard phase that constitutes the cemented carbide and the content of the binder phase in the cemented carbide. However, it was also found that the starting material (addition method) used to incorporate TaC into the cemented carbide also affects the average transverse rupture strength. To manufacture a cemented carbide with a high average transverse rupture strength, it is recommended to use Ta2O513 as the starting material and carbonize it during sintering. This is also believed to be true when NbC is contained in the cemented carbide instead of or in addition to TaC.

[0055] Tables 2 to 4 show the hardness and average transverse rupture strength measurements for a number of cemented carbide alloys (Samples No. 1 to No. 68) fabricated by appropriately varying the contents of titanium carbonitride (Ti(C,N)), tantalum carbide (TaC), niobium carbide (NbC), chromium carbide (Cr3C2), and cobalt (Co). The average grain size (0.4 μm) of tungsten carbide (WC) was the same for all samples. Furthermore, for all samples, Ti(C,N), TaC, and NbC were incorporated into the cemented carbide alloys by using oxides (TiO2, Ta2O5, Nb2O5) as starting materials.

[0056] [Table 2]

[0057] [Table 3]

[0058] [Table 4]

[0059] Hardness (HRA) was measured using a Rockwell hardness tester (scale A). The average transverse rupture strength (GPa) was calculated by averaging the multiple transverse rupture strengths obtained by performing multiple three-point bending tests on one sample.

[0060] In terms of hardness, samples No. 1 to No. 68 all have hardness equivalent to or greater than that of existing cemented carbide alloys (HRA 92.0 or greater). On the other hand, in terms of average transverse rupture strength, samples No. 1 to No. 6 (see Table 2) include some that do not meet the average transverse rupture strength of existing cemented carbide alloys (3.0 GPa or greater). Samples No. 7 to No. 68 all have average transverse rupture strength equivalent to or greater than that of existing cemented carbide alloys. Samples No. 1 to No. 6 do not contain Ti(C,N), while cemented carbide alloys No. 7 to No. 68 all contain Ti(C,N), indicating that the presence or absence of Ti(C,N) has a significant effect on the transverse rupture strength of cemented carbide alloys.

[0061] Groups No. 7 to No. 10, No. 11 to No. 15, No. 16 to No. 24, No. 25 to No. 30, No. 31 to No. 36, No. 37 to No. 41, and No. 42 to No. 46 are all cemented carbide samples prepared with fixed contents of Ti(C,N), Cr3C2, and Co, and with varying contents of TaC. Between each group, the Ti(C,N) content was varied within the range of 0.4 to 3.0 wt%.

[0062] Figure 4 shows a graph plotting the measurement results shown in Tables 1 to 4 for sample No. 1 that does not contain Ti(C,N) and neither TaC nor NbC, samples No. 2 to No. 4 that do not contain Ti(C,N) and contain TaC, sample No. 16 that contains Ti(C,N) and neither TaC nor NbC, and samples No. 17 to No. 22 that contain Ti(C,N) and contain TaC, with the horizontal axis representing the TaC content and the vertical axis representing the average transverse rupture strength.

[0063] It can be seen that samples No. 16 to No. 22 (black circles) containing Ti(C,N) have superior average transverse rupture strength compared to samples No. 1 to No. 4 (white circles) that do not contain Ti(C,N). It can also be seen that the average transverse rupture strength improves when TaC is added in addition to Ti(C,N), but that the average transverse rupture strength decreases as the TaC content increases. The average transverse rupture strength peaks when the TaC content is 0.25 to 1.00 wt%, and decreases when the TaC content is lower or higher than that. Focusing on the average transverse rupture strength, it is most effective to add approximately 0.25 to 1.00 wt% TaC to the cemented carbide together with Ti(C,N).

[0064] For the cemented carbide alloys in each group of Nos. 25 to 30, Nos. 31 to 36, Nos. 37 to 41, and Nos. 42 to 46 in Table 3, as described above, the average transverse rupture strength was improved by adding TaC in addition to Ti(C,N), peaking at a TaC content of 0.25 to 1.00 wt%, and the average transverse rupture strength decreased when the TaC content was higher.

[0065] Groups No. 47 to No. 52 in Table 4 are cemented carbide alloys to which NbC was added instead of TaC, and groups No. 53 to No. 60 are cemented carbide alloys to which both TaC and NbC were added. Whether NbC was added instead of TaC or whether NbC was added in addition to TaC, roughly the same phenomenon was observed.

[0066] Figure 5 is a graph showing how the average transverse rupture strength changes when the proportion of TaC that accounts for the total Ti(C,N) and TaC (i.e., grain growth inhibitor and dispersed phase) is changed in a cemented carbide containing both Ti(C,N) and TaC, i.e., when the content ratio of Ti(C,N) and TaC is changed. The horizontal axis represents the value of TaC / (Ti(C,N) + TaC) (wt%), and the further to the right it is, the greater the TaC content in (Ti(C,N) + TaC). Figure 5 shows representative samples No. 16 to No. 22 (see Table 2), which contain 1.3 wt% Ti(C,N).

[0067] Figure 5 shows that the average transverse rupture strength is high when the value (wt%) of TaC / (Ti(C,N) + TaC) is between 0.10 and 0.50. This means that when both Ti(C,N) and TaC are contained in a cemented carbide, the Ti(C,N) content should be greater than the TaC content. Furthermore, the measurement results shown in Tables 1 to 4 indicate that even when the value of TaC / (Ti(C,N) + TaC) is between 0.10 and 0.50, the average transverse rupture strength tends to be somewhat smaller when the Ti(C,N) content is relatively low (0.4 wt%) (Nos. 7 to 10) or relatively high (3.0 wt%) (Nos. 42 to 46). In the above content ratios, excluding Nos. 7 to 10 and Nos. 42 to 46, it is considered appropriate for cemented carbide to contain approximately 0.9 to 2.6 wt% Ti(C,N).

[0068] Figure 6 is a graph with the cobalt (Co) content (wt%) on the horizontal axis and the tantalum carbide (TaC) content on the vertical axis, plotting the measurement results for cemented carbide samples No. 61 to No. 64 shown in Table 4, as well as two conventional cemented carbide products, A and B. The composition of cemented carbide A is WC-0.9 wt% Cr3C2-0.6 wt% TaC-12 wt% Co, and the composition of cemented carbide B is WC-0.8 wt% TaC-0.2 wt% NbC-6 wt% Co, and neither contains Ti (C, N).

[0069] The graph in Figure 6, which shows the relationship between the crystallized region and the residual region with increasing or decreasing Co content and TaC content, is based on Murakami Yoshizo, Takeda Tsuneo, and Tsuchiya Shinjiro, "On the abnormal structure of TaC in WC-TaC-Co alloys," Powder and Powder Metallurgy, Japan Powder and Powder Metallurgy Association, published January 15, 1968, Vol. 15, No. 1, pp. 14-18.

[0070] TaC dissolves in the binder phase (Co), but adding TaC in an amount below its solubility results in a crystallized structure (mottled structure) after cooling, while adding TaC in an amount above its solubility results in a residual structure after cooling. The dashed lines in Figure 6 separate the region of Co and TaC content that results in a crystallized structure (crystallized region) from the region of Co and TaC content that results in a residual region (residual region).

[0071] Figure 7 is an optical microscope photograph (400x magnification, etched) of cemented carbide A (WC-0.9wt%Cr3C2-0.6wt%TaC-12wt%Co) containing TaC, and the black spotted structure in the photograph is TaC. As shown in the graph in Figure 6, it can be seen that TaC has crystallized in the structure of cemented carbide A. TaC dissolves in Co during sintering, but crystallizes after cooling, causing TaC to appear in spots in the structure. Due to the absence of nuclei, the TaC appears inhomogeneously (in spots) after crystallization. The presence of inhomogeneous TaC reduces the properties (transverse rupture strength and hardness) of the cemented carbide.

[0072] Figure 8 is an optical microscope photograph (400x magnification, etched) of cemented carbide B (WC-0.8wt%TaC-0.2wt%NbC-6wt%Co) containing TaC and NbC, and the black parts in the photograph are TaC and NbC. As shown in the graph in Figure 6, it can be seen that in cemented carbide B, TaC and NbC do not completely dissolve but remain in the structure. Compared to crystallization (Figure 7), the remaining TaC and NbC are homogeneous, but the grain size increases with the remaining TaC and NbC as nuclei, so the properties of the cemented carbide are reduced.

[0073] 9 to 12 are optical microscope photographs (400x magnification, etched) of each of the cemented carbide samples No. 61 to No. 64.

[0074] According to the graph shown in Figure 6, which is based on the above-mentioned literature, TaC should have crystallized in all of the cemented carbide alloys No. 61 to No. 64, as shown in Figure 7. However, for all of the cemented carbide alloys No. 61 to No. 64, the crystallized structure of TaC could not be confirmed using an optical microscope. Neither the crystallization nor the residual Ti(C,N) was confirmed.

[0075] Figures 13 and 14 are optical microscope photographs (400x, etched) of cemented carbide samples No. 63 and No. 64, respectively, which were produced by maintaining the same Co content but doubling the TaC content. According to the graph in Figure 6, TaC should remain as shown in Figure 8, but no residual structure could be confirmed in the optical microscope photographs. No crystallization or residual Ti(C,N) was confirmed.

[0076] Comparing the compositions of conventional cemented carbide A and B, whose optical microscope photographs are shown in Figures 7 and 8, with those of cemented carbide Nos. 61 to 64, the difference is that they contain Ti(C,N) in addition to TaC and NbC. The combination of TaC, NbC, and Ti(C,N) eliminates the crystallization and residue of TaC and NbC. In other words, TaC and NbC large enough to be visible with an optical microscope do not crystallize or remain in the structure, but rather TaC and NbC are finely dispersed throughout the structure. No crystallization or residue of Ti(C,N) was observed, and the combination of Ti(C,N) with TaC and NbC is also considered to finely disperse Ti(C,N). The optical microscope photographs suggest that a solid solution or complex consisting of both Ti(C,N) and TaC and / or NbC is finely dispersed within the cemented carbide.

[0077] 15 to 18 are scanning electron microscope photographs (5,000x magnification) of the cemented carbide samples No. 61 to No. 64, respectively.

[0078] 15 to 18 and the compositions of Nos. 61 to 64 in Table 4, the less Co there is in the binder phase (the Co content decreases from No. 61 to No. 64), the narrower the distance between WC particles and the higher the hardness of the cemented carbide. However, according to the measurement results shown in Table 4, although hardness increases with a decrease in Co content, the average transverse rupture strength gradually decreases. The Co content can be adjusted appropriately, taking into account the balance between hardness (hardness) and transverse rupture strength (strength).

[0079] Referring to cemented carbide samples No. 65 to No. 68 shown in Table 4, cemented carbide samples No. 65 to No. 68 are all cemented carbide containing Ti(C,N) and TaC, with varying amounts of Cr3C2. It can be seen that the inclusion of Cr3C2 also improves the average transverse rupture strength, but the average transverse rupture strength decreases when more Cr3C2 is added, reaching a peak at about 0.50 wt%.

[0080] Cemented carbide containing TaC or NbC in addition to Ti(C,N), and more preferably Cr3C2, has excellent hardness and transverse rupture strength, and when used as cutting tools or wear-resistant components, it is possible to manufacture products with excellent wear resistance. Below, we will explain the results of evaluation tests on drills and insert chips using cemented carbide containing Ti(C,N), TaC, and Cr3C2.

[0081] FIG. 19 shows an enlarged view of the tip portion (cutting edge) of the drill.

[0082] The drill 1 has a chisel 11 at the tip, two cutting edges 12 extending on either side of the chisel 11, a flank 13 continuous with the cutting edges 12, a relief surface 14 continuous with the flank 13, a margin 15 forming the top of the relief surface 14, and a rake surface 16 through which chips of the cutting material flow.

[0083] The tip of the drill 1, which rotates at high speed, is pressed against the workpiece. The workpiece is cut by the chisel 11 and the cutting edge 12 connected to the chisel 11. The workpiece is cut by sending the drill 1 toward the workpiece, and a hole corresponding to the diameter of the drill 1 is made in the workpiece.

[0084] The chisel 11 and cutting edge 12 are in direct contact with the workpiece and therefore gradually wear away. Wear of not only the chisel 11 and cutting edge 12 but also the flank 13 and margin 15 adjacent to the cutting edge 12 is unavoidable.

[0085] FIG. 20 is an enlarged perspective view of the insert chip.

[0086] The insert chip 2 has a cutting edge 21, a flank 22, and a rake face 23. The cutting edge 21 cuts the material, and the cut material flows along the rake face 23. The ridge between the flank 22 and the rake face 23 forms the cutting edge 21. When the cutting edge 21 of the insert chip 2 is pressed against the surface of a workpiece rotating at high speed, the surface of the workpiece is cut away by the insert chip 2. The surface of the workpiece is turned by moving the insert chip 2 along the axial direction of the rotation axis of the workpiece (along the longitudinal direction of the workpiece). With the insert chip 2, not only the cutting edge 21 but also the flank 22 and rake face 23 that are continuous with the cutting edge 21 gradually wear down.

[0087] (Drilling test) Table 5 shows the composition (amount of each component) of the cemented carbide constituting the six types of cemented carbide drills 1 (Example 1 and Comparative Examples 1 to 5) used in the drilling tests, as well as the WC grain size, hardness, and average transverse strength after sintering. "bal." in the amount of WC indicates the remaining amount. The content of Co (10 wt%) as a binder phase was the same in Example 1 and Comparative Examples 1 to 5.

[0088] [Table 5]

[0089] Hardness was measured using a Rockwell hardness tester (scale A). Average transverse strength was measured by a three-point bending test.

[0090] The cemented carbide of Example 1 is the above-mentioned cemented carbide containing WC as a hard phase, Ti(C,N) and TaC as a grain growth inhibiting phase and a dispersed phase, Co as a binder phase, and further containing Cr3C2. In Table 5, the contents of WC, Ti(C,N), Co, and VC, which will be described later, are shown based on the entire cemented carbide. Cr3C2 indicates the content based on the binder phase (Co in this case).

[0091] The cemented carbide of Example 1 contains both Ti(C,N) and TaC, while the cemented carbides of Comparative Examples 1 and 2 contain only Ti(C,N) but no TaC. The cemented carbide of Comparative Example 3 contains neither Ti(C,N) nor TaC, and contains vanadium carbide (VC) as a grain growth inhibitor phase. The cemented carbide of Comparative Example 4 contains none of Ti(C,N), TaC, or VC, resulting in a slightly larger WC grain size (0.81 μm) after sintering. The cemented carbide of Comparative Example 5 also contains no Cr3C2, resulting in an even larger WC grain size (1.72 μm) after sintering.

[0092] In terms of hardness, the cemented carbide of Comparative Example 2 is relatively superior. On the other hand, in terms of the average transverse rupture strength of the cemented carbide of Example 1 and Comparative Example 2, the average transverse rupture strength of the cemented carbide of Example 1 is greater, making the cemented carbide of Example 1 a better balanced cemented carbide than Comparative Example 2.

[0093] 21 to 23 show the results of drilling tests using 6 mm diameter drills 1 (see FIG. 19) made using the six types of cemented carbide alloys shown in Table 5 above. In the graphs shown in FIGS. 21 to 23, the horizontal axis represents the number of holes drilled in the workpiece. On the vertical axis, FIG. 21 shows the wear amount (mm) of the chisel 11, FIG. 22 shows the wear amount (mm) of the flank 13, and FIG. 23 shows the wear amount (mm) of the margin 15. In the graphs of FIGS. 21 to 23, the graph for drill 1 made using the cemented carbide alloy of Example 1 is shown by a solid line, and the graphs for cemented carbide drills made using the cemented carbides of Comparative Examples 1 to 5 are shown by dashed lines. To distinguish from the test results of coated cemented carbide alloys (coated cemented carbide alloys), which will be described later, the words "uncoated" are clearly indicated in the upper left corner of the graphs shown in FIGS. 21 to 23.

[0094] In the drilling test, S50C (HRC34) was used as the workpiece (machined material). The workpiece was drilled in a non-step manner, and blind holes 20 mm deep were drilled one after another in the workpiece. Water-soluble coolant was supplied from the outside during drilling. The rotation speed of Drill 1 was 4700 rpm, and the feed rate was 600 mm / min.

[0095] The end points of the graphs in Figures 21 to 23 indicate that the drilling test was terminated because the drill 1 had reached the end of its life. The life of the drill 1 is determined based on a predetermined amount of wear (for example, when the wear amount of the chisel 11 reaches a predetermined amount), as well as the occurrence of breakage of the drill 1, the occurrence of chips of 0.5 mm or more, the occurrence of abnormally shaped cutting chips, and the occurrence of abnormal noise during cutting.

[0096] The number of holes drilled when the cemented carbide drill 1 of Example 1 reached the end of its life was approximately 460, approximately 420 when using the cemented carbide of Comparative Example 1, approximately 170 when using the cemented carbide of Comparative Example 2, approximately 140 when using the cemented carbide of Comparative Example 3, approximately 140 when using the cemented carbide of Comparative Example 4, and 82 when using the cemented carbide of Comparative Example 5.

[0097] Referring to Figures 21 to 23, it can be seen that the cemented carbide drill 1 of Example 1, i.e., the drill 1 made using a cemented carbide containing both Ti(C,N) and TaC, has superior wear resistance compared to the cemented carbide drills 1 of Comparative Examples 1 to 5.

[0098] Figures 24 to 26 show the results of drilling tests using six types of drills 1, each 6 mm in diameter, fabricated using the six types of cemented carbide alloys shown in Table 5 and coated with TiAlN using physical vapor deposition (PVD). To distinguish from Figures 21 to 23, the words "Coated" are clearly indicated in the upper left corner of the graphs in Figures 24 to 26.

[0099] The number of holes drilled at the end of its life was approximately 2600 for the coated cemented carbide drill 1 in which the cemented carbide was coated with TiAlN in Example 1, approximately 2000 for the coated cemented carbide in which the cemented carbide was coated with TiAlN in Comparative Example 1, approximately 2500 for the coated cemented carbide in which the cemented carbide was coated with TiAlN in Comparative Example 2, approximately 1200 for the coated cemented carbide in which the cemented carbide was coated with TiAlN in Comparative Example 3, approximately 1300 for the coated cemented carbide in which the cemented carbide was coated with TiAlN in Comparative Example 4, and approximately 900 for the coated cemented carbide in which the cemented carbide was coated with TiAlN in Comparative Example 5.

[0100] 24 to 26, it was found that the coated cemented carbide drill in which the cemented carbide of Example 1 was coated with TiAlN was significantly more wear-resistant than the coated cemented carbide drills in which the cemented carbide of Comparative Examples 1 to 5 was coated with TiAlN. It is thought that the adhesiveness between the cemented carbide as the substrate (base material) and the coated TiAlN contains the same element (Ti), which improved the adhesion between the two and extended the lifespan.

[0101] (Turning test) Table 6 shows the composition (amount) of the cemented carbide that makes up the four types of coated cemented carbide insert chips 2 (Example 2, Comparative Examples 6 to 8) used in the turning tests, as well as the WC particle size, hardness and average transverse strength after sintering.

[0102] [Table 6]

[0103] Whereas the cemented carbide of Example 2 contains both Ti(C,N) and TaC, the cemented carbide of Comparative Example 6 contains only Ti(C,N) and no TaC. Conversely, the cemented carbide of Comparative Example 7 contains only TaC and no Ti(C,N). The cemented carbide of Comparative Example 8 contains neither Ti(C,N) nor TaC (nor VC). Furthermore, Example 2 and Comparative Examples 6 and 7 are coated cemented carbides in which cemented carbides having the composition shown in Table 6 are coated with TiAlN using physical vapor deposition (PVD), and Comparative Example 8 is a cemented carbide in which the cemented carbide having the composition shown in Table 6 is coated with multiple layers of TiAlN and CrAlN alternately.

[0104] Figure 27 shows a graph of the test results of a turning test using four types of insert chips 2, each having the shape shown in Figure 20, which were fabricated using the four types of coated cemented carbide shown in Table 6 and coated with TiAlN (Example 2, Comparative Examples 6 and 7) or TiAlN and CrAlN (Comparative Example 8) using physical vapor deposition (PVD). In the graph of Figure 27, the horizontal axis represents the cutting distance, and the vertical axis represents the wear width (mm) of the flank 22. In the graph of Figure 27, the graph for the coated cemented carbide insert chip 2 fabricated using the cemented carbide of Example 2 is shown by a solid line, and the graphs for the coated cemented carbide insert chips fabricated using the cemented carbides of Comparative Examples 6, 7, and 8 are shown by dashed lines.

[0105] In the turning test, a polished round bar made of S45C with a diameter of 80 mm was used as the workpiece (work material). The cutting speed was 160 m / min, the feed rate was 0.2 mm / rev, and the depth of cut was 2.0 mm. Water-soluble cutting oil was supplied appropriately during turning.

[0106] The life of insert tip 2 (end of turning test) was determined when flank wear of 0.2 mm or more occurred.

[0107] The cutting distance when the end of its life was reached was approximately 45,000 m for the coated cemented carbide insert tip 2 in which the cemented carbide of Example 2 was coated with TiAlN, approximately 27,000 m for the cemented carbide of Comparative Example 6, approximately 8,000 m for the cemented carbide of Comparative Example 7, and 8,100 m for the cemented carbide of Comparative Example 8. It can be seen that the coated cemented carbide insert tip 2 in which the cemented carbide of Example 2 was coated with TiAlN is significantly superior in wear resistance to the coated cemented carbide insert tips in which the cemented carbide of Comparative Examples 6 to 8 were coated with TiAlN.

[0108] The above describes the test results for cemented carbide drills, coated cemented carbide drills, and coated cemented carbide insert tips. However, superior wear resistance results compared to conventional methods can also be obtained for cutting tools or wear-resistant components other than drills or insert tips. Furthermore, TiAlN was used as the hard coating in the above studies. Hard coatings containing Ti other than TiAlN, specifically TiC, TiN, TiSiN, and Ti(C,N), are also believed to contribute to improved wear resistance equivalent to that of TiAlN. Scratch tests were conducted under the same conditions on three types of hard coatings: TiAlN, TiN, and Ti(C,N). No peeling occurred in any of the coatings, and no differences in performance were observed among the three types. In any case, if carbides, nitrides, carbonitrides, oxides, or their mutual solid solutions containing at least Ti are used as hard coatings, they are likely to adhere well to the cemented carbides mentioned above, significantly extending the life of cutting tools or wear-resistant components. [Explanation of symbols]

[0109] 11 Tungsten carbide 12 Titanium oxide 13 Tantalum oxide 14 Cobalt 15 Chromium carbide 16 carbon

Claims

1. The hard phase, whose main component is tungsten carbide (WC), contains 30.0 to 99.3 wt% of the entire cemented carbide. The cemented carbide contains 0.2 to 40.0 wt% of a grain growth inhibiting and dispersed phase, the main component of which is a solid solution or composite containing titanium carbonitride (Ti(C,N)), which is produced by carbonitriding titanium (Ti) oxide during sintering, and at least one of tantalum carbide (TaC) and niobium carbide (NbC), with respect to the entire cemented carbide; The cemented carbide alloy contains a binder phase whose main component is at least one selected from the group consisting of cobalt (Co), nickel (Ni), and iron (Fe) in an amount of 0.5 to 30.0 wt% based on the total weight of the cemented carbide alloy, The total of the hard phase, the grain growth inhibiting and dispersed phase, and the binder phase is 100 wt%; When X is TaC, NbC, or TaC and NbC, X / (Ti (C, N) + X) (wt% ratio) is 0.10 to 0.50; Cemented carbide.

2. A hard phase mainly composed of tungsten carbide (WC), a binder phase containing at least one selected from the group consisting of cobalt (Co), nickel (Ni), and iron (Fe) as a main component; and The alloy contains a grain growth inhibiting and dispersed phase mainly composed of a solid solution or composite containing titanium carbonitride (Ti(C,N)) produced by carbonitriding titanium (Ti) oxide during sintering, and at least one of tantalum carbide (TaC) and niobium carbide (NbC), The grain growth inhibitor and dispersed phase are uniformly dispersed in the structure, When X is TaC, NbC, or TaC and NbC, X / (Ti (C, N) + X) (wt% ratio) is 0.10 to 0.50; Cemented carbide.

3. A hard phase mainly composed of tungsten carbide (WC), a binder phase containing at least one selected from the group consisting of cobalt (Co), nickel (Ni), and iron (Fe) as a main component; and The alloy comprises a grain growth inhibiting and dispersed phase mainly composed of a solid solution or composite containing titanium carbonitride (Ti(C,N)) produced by carbonitriding titanium (Ti) oxide during sintering, and at least one of tantalum carbide (TaC) and niobium carbide (NbC), There is no grain growth inhibition, no mottled structure of the dispersed phase, and no residual structure. When X is TaC, NbC, or TaC and NbC, X / (Ti (C, N) + X) (wt% ratio) is 0.10 to 0.50; Cemented carbide.

4. TaC is produced by carbonizing Ta oxide during sintering.

4. The cemented carbide according to any one of claims 1 to 3.

5. NbC is produced by carbonizing Nb oxide during sintering.

5. The cemented carbide according to any one of claims 1 to 4.

6. Chromium carbide (Cr ３ C ２ ) is contained in the binder phase at 0.1 to 20.0 wt% of the total weight of the binder phase.

6. The cemented carbide according to any one of claims 1 to 5.

7. 2. The cemented carbide according to claim 1, wherein the content of Ti(C,N) is 0.90 to 2.60 wt% based on the total amount of the cemented carbide.

8. The cemented carbide according to any one of claims 1 to 7 is coated with a hard coating by PVD or CVD. Coated cemented carbide.

9. The hard coating is at least one selected from the group consisting of TiC, TiN, TiAlN, TiSiN, and Ti(C,N), The coated cemented carbide according to claim 8.

10. an Al-containing carbide, nitride, carbonitride, or oxide, or a composite material thereof, is laminated on the base of the hard coating or on the surface of the hard coating; The coated cemented carbide according to claim 9.

11. A cutting tool comprising a cemented carbide according to any one of claims 1 to 7 or a coated cemented carbide according to any one of claims 8 to 10.

12. A wear-resistant member made of the cemented carbide according to any one of claims 1 to 7 or the coated cemented carbide according to any one of claims 8 to 10.

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