Cermet and coated cermet

Abstract

To provide a cermet and a coated cermet having improved wear resistance and chipping resistance and a long tool life.SOLUTION: Provided is a cermet comprising a hard phase and a binder phase, the content ratio of the hard phase being 80.0 volume% or more and 94.0 volume% or less and the content ratio of the binder phase being 6.0 volume% or more and 20.0 volume% or less, wherein the hard phase is a phase containing a carbonitride containing Ti and at least one element selected from the group consisting of W, Mo, Cr, Ta, Nb, V, Hf, and Zr, the hard phase contains a cubic crystal, the binder phase is a phase containing at least one element selected from the group consisting of Co, Ni, and Fe, the hard phase is composed of hard grains, and when the region that is more than 100 μm away from the surface of the cermet toward the inside is defined as the internal region, and the ratio of the length of the corresponding grain boundary to the total length of the grain boundaries between adjacent hard particles in the internal region (100%) is defined as ratio A, the ratio A is 12% or more and 50% or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to cermets and coated cermets.

Background Art

[0002] Conventionally, as cutting tools, there are carbide cutting tools mainly composed of tungsten carbide (WC) as a main hard phase, TiCN-based cermet cutting tools mainly composed of titanium carbonitride (TiCN) as a main hard phase, cBN sintered body cutting tools mainly composed of cubic boron nitride, and the like. Among these, cermet cutting tools are mainly used for cutting steel because they have low affinity for steel and are excellent in wear resistance and finish surface roughness. By the way, in recent years, cutting has tended to be more efficient, with a tendency towards higher cutting speeds, deeper cuts, and higher feed rates. Under such circumstances, there is a demand for TiCN-based cermet cutting tools that are even more excellent in wear resistance and chipping resistance and have a long tool life.

[0003] In response to such demands, various cermet cutting tools have been proposed so far. For example, Patent Document 1 discloses a surface-coated cermet composed of hard particles and a binder phase, in which the average crystal grain size of the hard particles in the surface layer portion is larger than the average crystal grain size in the interior, and at least 20% of the hard particles having a particle size of 2 μm or more are present in the surface layer portion, and the average crystal grain size of the hard particles in the interior is 3 μm or less. By forming a surface coating layer composed of at least one layer or two or more layers of carbides, nitrides, carbonitrides, and oxides of Group 4a elements and Al in the periodic table on the surface of the cermet, it is possible to greatly improve wear resistance, chipping resistance, and thermal shock resistance, and it is also disclosed that the thermal shock resistance is improved during wet cutting.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As described above, in recent years, on the surface of a surface-coated cermet, the average crystal grain size of the hard particles in the surface layer is larger than the average crystal grain size inside, and the hard particles having a particle size of 2 μm or more in the surface layer account for 20% or more, and the average crystal grain size of the hard particles inside is made 3 μm or less. However, the binding force between adjacent hard particles is not sufficient, and from the viewpoint of preventing the progress of wear due to the dropout of hard particles, the performance is still insufficient and there is room for improvement.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a cermet and a coated cermet that can extend the tool life when used as a tool material by having excellent wear resistance and defect resistance.

Means for Solving the Problems

[0007] The present inventors have repeatedly studied the extension of the tool life of cermets, and as a result of making the cermet have a specific structure, it has been found that the wear resistance and defect resistance can be improved, and as a result, the tool life of the cermet can be extended, and the present invention has been completed.

[0008] That is, the gist of the present invention is as follows. [1] A cermet containing a hard phase and a binder phase, The content ratio of the hard phase is 80.0% by volume or more and 94.0% by volume or less, The content ratio of the binder phase is 6.0% by volume or more and 20.0% by volume or less, The hard phase is a phase containing a carbonitride containing Ti and at least one element selected from the group consisting of W, Mo, Cr, Ta, Nb, V, Hf, and Zr, The hard phase contains a cubic crystal, The bonding phase is a phase containing at least one element selected from the group consisting of Co, Ni, and Fe; The hard phase consists of hard particles; Taking the region more than 100 μm away from the surface of the cermet toward the inside as the internal region, when the ratio of the length of the corresponding grain boundary to the total length of the grain boundaries between adjacent hard particles in the internal region is defined as ratio A, the ratio A is 12% or more and 50% or less; Cermet. [2] In the hard phase, the content ratio (atomic ratio) of Ti to the total content ratio of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is 0.65 or more and 0.90 or less; The cermet according to [1]. [3] In the internal region, when the ratio of the length of the Σ3 grain boundary to the length of the corresponding grain boundary with respect to 100% of the length of the corresponding grain boundary is defined as ratio X, the ratio X is 20% or more and 50% or less; The cermet according to [1] or [2]. [4] Taking the region up to 100 μm from the surface of the cermet toward the inside as the surface region, when the ratio of the length of the corresponding grain boundary to the total length of the grain boundaries between adjacent hard particles in the surface region is defined as ratio B, the ratio B is 15% or more and 55% or less; The cermet according to any one of [1] to [3]. [5] The ratio of the ratio B to the ratio A (B / A) is 1.1 or more and 2.0 or less; The cermet according to [4]. [6] In the surface region, when the ratio of the length of the Σ3 grain boundary to the length of the corresponding grain boundary with respect to 100% of the length of the corresponding grain boundary is defined as ratio Y, the ratio Y is 30% or more and 60% or less; The cermet according to [4] or [5]. [7] In the internal region, when the ratio of the length of the Σ3 grain boundary to the length of the corresponding grain boundary is defined as ratio X, the ratio (Y / X) of the ratio Y to the ratio X is 1.2 or more and 2.5 or less. The cermet according to [6]. [8] A coated cermet comprising the cermet according to any one of [1] to [7] and a coating layer formed on the surface of the cermet. [9] The average thickness of the entire coating layer is 0.5 μm or more and 20.0 μm or less. The coated cermet according to [8].

[10] The coating layer is a single layer or a laminate of two or more layers containing at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si and at least one element selected from the group consisting of C, N, O, and B. The coated cermet according to [8] or [9]. [Advantages of the Invention]

[0009] According to the present invention, it is possible to provide a cermet and a coated cermet that can extend the tool life by having excellent wear resistance and chipping resistance. [Embodiments for Carrying Out the Invention]

[0010] Hereinafter, embodiments for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail, but the present invention is not limited to the following present embodiment. The present invention can be variously modified without departing from the gist thereof.

[0011] [Cermet] The cermet of the present embodiment is a cermet containing a hard phase and a binder phase, The content ratio of the hard phase is 80.0% by volume or more and 94.0% by volume or less, The content ratio of the binder phase is 6.0% by volume or more and 20.0% by volume or less, The hard phase is a phase containing a carbonitride containing Ti and at least one element selected from the group consisting of W, Mo, Cr, Ta, Nb, V, Hf, and Zr. The hard phase contains a cubic crystal structure. The binding phase is a phase containing at least one element selected from the group consisting of Co, Ni, and Fe. The hard phase consists of hard particles. Taking the region more than 100 μm away from the surface of the cermet toward the inside as the internal region, when the ratio of the length of the corresponding grain boundary to the total length of the grain boundaries between adjacent hard particles in the internal region is defined as ratio A, ratio A is 12% or more and 50% or less.

[0012] The factors that improve the wear resistance, plastic deformation resistance, and defect resistance of such a cermet are not clear in detail but are presumed as follows. However, the factors are not limited to the following. When the content ratio of the hard phase is 80.0% by volume or more with respect to 100% by volume of the cermet, the hardness and plastic deformation resistance of the cermet are improved, and it has excellent wear resistance. When the content ratio of the hard phase is 94% by volume or less, the ratio of the binding phase relatively increases, so the toughness of the cermet is improved, and it has excellent defect resistance. When the content ratio of the binding phase is 6.0% by volume or more with respect to 100% by volume of the cermet, the toughness of the cermet is improved, and it has excellent defect resistance. When the content ratio of the binding phase is 20.0% by volume or less, the ratio of the hard phase relatively increases, so the hardness and plastic deformation resistance of the cermet are improved, and it has excellent wear resistance. The hard phase contains a carbonitride containing Ti and at least one element selected from the group consisting of W, Mo, Cr, Ta, Nb, V, Hf, and Zr, so it has excellent wear resistance and defect resistance. Since the hard phase contains a cubic crystal structure, the hardness is improved, so it has excellent wear resistance. The binding phase contains at least one element selected from the group consisting of Co, Ni, and Fe, so it has excellent wear resistance and defect resistance. In the internal region of the cermet, when the ratio A of the length of the corresponding grain boundary to the total length of the grain boundaries between adjacent hard particles is 12% or more with respect to 100%, the bonding force between adjacent hard particles increases, suppressing the progress of wear due to particle detachment, so it has excellent wear resistance. Also, since the generation and progress of cracks are suppressed, it is also excellent in chipping resistance and defect resistance. Further, in the internal region of the cermet, when the ratio A of the length of the corresponding grain boundary to the total length of the grain boundaries between adjacent hard particles is 50% or less with respect to 100%, stress concentration on grain boundaries other than the corresponding grain boundary is alleviated, so the chipping resistance is improved and it is excellent in defect resistance. Also, since the size of the detachment mark due to particle detachment tends to be small, the occurrence of uneven wear starting from this is suppressed, and it is also excellent in wear resistance. Combined with these effects, the cermet of the present embodiment has improved wear resistance, plastic deformation resistance, and defect resistance.

[0013] In the present embodiment, the "surface region of the cermet" refers to the region within 100 μm from the surface of the cermet toward the inside, and the "internal region of the cermet" refers to the region more than 100 μm away from the surface of the cermet toward the inside. Also, "hard particles" means crystal grains constituting the hard phase, and the hard phase is composed of hard particles. Also, the corresponding grain boundary refers to all the corresponding grain boundaries indicated by Σn grain boundaries (n is an odd number from 3 to 29) among the corresponding grain boundaries indicated by the combination of Σ and numbers.

[0014] [Hard phase] In the cermet of the present embodiment, the hard phase is a phase containing a carbonitride containing Ti and at least one element selected from the group consisting of W, Mo, Cr, Ta, Nb, V, Hf, and Zr. By the hard phase being a phase containing the carbonitride, the wear resistance and chipping resistance of the cermet are improved. From the same viewpoint, the hard phase preferably contains at least Ti, more preferably contains Ti and W, still more preferably contains Ti, W, and Mo, and even more preferably contains Ti, W, Mo, Nb, and Zr. The hard phase is preferably a phase composed of a carbonitride containing Ti and at least one element selected from the group consisting of W, Mo, Cr, Ta, Nb, V, Hf, and Zr, more preferably a phase composed of a carbonitride of at least one element selected from the group consisting of Ti and W, Mo, Cr, Ta, Nb, V, Hf, and Zr, still more preferably a phase composed of a carbonitride of at least one element selected from the group consisting of Ti and W, Mo, Cr, Ta, Nb, V, and Zr, and even more preferably a phase composed of a carbonitride of at least one element selected from the group consisting of Ti and W, Mo, Nb, and Zr.

[0015] In the hard phase, the content ratio (atomic ratio) of Ti to the total content ratio of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is preferably 0.65 or more and 0.90 or less. When the content ratio of Ti is 0.65 or more, the reactivity with the workpiece to be machined is lowered, and the wear resistance tends to be improved. Further, when the content ratio of Ti is 0.90 or less, the toughness of the cermet is improved, and the chipping resistance tends to be improved. From the same viewpoint, the content ratio of Ti is more preferably 0.68 or more and 0.88 or less, and still more preferably 0.70 or more and 0.86 or less.

[0016] In the hard phase, when the content ratio (atomic ratio) of W to the total content ratio of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is 0.03 or more and 0.30 or less, it is preferable because the wear resistance and defect resistance of the cermet tend to improve. When the content ratio of W is 0.03 or more, the toughness of the cermet improves, so the defect resistance tends to further improve. Further, when the content ratio of W is 0.30 or less, the thermal conductivity of the cermet improves, so the wear resistance tends to further improve. From the same viewpoint, the content ratio of W is more preferably 0.04 or more and 0.22 or less, and even more preferably 0.05 or more and 0.14 or less.

[0017] In the hard phase, when the content ratio (atomic ratio) of Mo to the total content ratio of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is 0.00 or more and 0.05 or less, it is preferable because the wear resistance and defect resistance of the cermet tend to improve. When the content ratio of Mo exceeds 0.00, the heat resistance of the cermet improves, so the wear resistance and defect resistance tend to further improve. Further, when the content ratio of Mo is 0.10 or less, the thermal conductivity of the cermet improves, so the wear resistance tends to further improve. From the same viewpoint, the content ratio of Mo is more preferably 0.01 or more and 0.02 or less.

[0018] In the hard phase, when the content ratio (atomic ratio) of Ta to the total content ratio of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is 0.00 or more and 0.20 or less, it is preferable because the wear resistance and defect resistance of the cermet tend to improve. When the content ratio of Ta exceeds 0.00, the heat resistance of the cermet improves, so the wear resistance and defect resistance tend to further improve. Further, when the content ratio of Ta is 0.20 or less, the thermal conductivity of the cermet improves, so the wear resistance tends to further improve. From the same viewpoint, the content ratio of Ta is more preferably more than 0.00 and 0.15 or less, and even more preferably more than 0.00 and 0.09 or less.

[0019] In the hard phase, when the content ratio (atomic ratio) of Nb to the total content ratio of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is 0.00 or more and 0.20 or less, it is preferable because the wear resistance and defect resistance of the cermet tend to improve. When the content ratio of Nb exceeds 0.00, the heat resistance of the cermet improves, so the wear resistance and defect resistance tend to further improve. Also, when the content ratio of Nb is 0.20 or less, the thermal conductivity of the cermet improves, so the wear resistance tends to further improve. From the same perspective, the content ratio of Nb is more preferably 0.06 or more and 0.16 or less, and even more preferably 0.06 or more and 0.15 or less.

[0020] In the hard phase, when the content ratio (atomic ratio) of Cr to the total content ratio of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is 0.00 or more and 0.05 or less, it is preferable because the wear resistance and defect resistance of the cermet tend to improve. When the content ratio of Cr exceeds 0.00, the heat resistance of the cermet improves, so the wear resistance and defect resistance tend to further improve. Also, when the content ratio of Cr is 0.05 or less, the sinterability of the cermet improves, so the wear resistance and defect resistance tend to further improve. From the same perspective, the content ratio of Cr is more preferably more than 0.00 and 0.02 or less, and even more preferably more than 0.00 and 0.01 or less.

[0021] In the hard phase, when the content ratio (atomic ratio) of V to the total content ratio of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is 0.00 or more and 0.05 or less, it is preferable because the wear resistance and defect resistance of the cermet tend to improve. When the content ratio of V exceeds 0.00, the heat resistance of the cermet improves, so the wear resistance and defect resistance tend to further improve. Also, when the content ratio of V is 0.05 or less, the sinterability of the cermet improves, so the wear resistance and defect resistance tend to further improve. From the same perspective, the content ratio of V is more preferably 0.01 or more and 0.02 or less.

[0022] In the hard phase, when the content ratio (atomic ratio) of Zr to the total content ratio of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is 0.00 or more and 0.03 or less, the wear resistance and / or defect resistance of the cermet tend to improve, which is preferable. When the content ratio of Zr exceeds 0.00, the plastic deformation resistance of the cermet improves, so the wear resistance tends to further improve. Further, when the content ratio of Zr is 0.03 or less, the sinterability of the cermet improves, so the wear resistance and defect resistance tend to further improve. From the same viewpoint, the content ratio of Zr is more preferably 0.01 or more and 0.02 or less.

[0023] In the hard phase, the atomic ratio of the content ratio of the C element to the total content ratio of the C element and the N element (C / (C + N)) is preferably 0.40 or more and 0.75 or less. When the atomic ratio (C / (C + N)) is 0.40 or more, the hardness of the cermet improves, so the wear resistance tends to further improve. Further, when the atomic ratio (C / (C + N)) is 0.75 or less, the reactivity of the cermet with the workpiece to be machined decreases, so the wear resistance tends to further improve. From the same viewpoint, the content ratio of W is more preferably 0.41 or more and 0.69 or less, further preferably 0.43 or more and 0.67 or less, and even more preferably 0.49 or more and 0.66 or less.

[0024] In the hard phase, the atomic ratio of the total content ratio of the W element and the Mo element to the content ratio of the Ti element ((W + Mo) / Ti) is preferably 0.03 or more and 0.40 or less. When the atomic ratio ((W + Mo) / Ti) is 0.03 or more, the ratio X described below tends to increase. Further, when the atomic ratio ((W + Mo) / Ti) is 0.40 or less, the thermal conductivity of the cermet improves, so the wear resistance tends to further improve. From the same viewpoint, the content ratio of W is more preferably 0.06 or more and 0.35 or less, further preferably 0.10 or more and 0.24 or less, and even more preferably 0.12 or more and 0.21 or less.

[0025] The hard phase of this embodiment preferably consists of cubic crystals. Since the hard phase consists of cubic crystals, the hardness is improved and the wear resistance tends to be further excellent. The crystal structure of the hard phase can be confirmed by performing X-ray diffraction measurement.

[0026] The hard phase in this embodiment has crystal grain boundaries with relatively high grain boundary energy and crystal grain boundaries with relatively low grain boundary energy. Usually, since the atomic arrangement in the crystal grain boundary is irregularly disordered and randomly arranged, there are many gaps and it has a relatively high grain boundary energy. On the other hand, among the crystal grain boundaries, there are grain boundaries with regular atomic arrangements and few gaps, and such crystal grain boundaries have relatively low grain boundary energy. A representative example of such a crystal grain boundary with relatively low grain boundary energy is a coincidence site lattice (CSL) grain boundary, which is also called a coincidence grain boundary. As an index indicating the degree of the distribution of the coincidence grain boundary, the Σ value is known, and it is defined as the ratio of the crystal lattice point density of two crystal grains in contact at the crystal grain boundary and the density of lattice points that coincide when both crystal lattices are overlapped. In the case of a simple structure, it is generally recognized that grain boundaries with a low Σ value tend to have low interface energy and special properties. Therefore, controlling the ratio of the coincidence grain boundary and the distribution of the crystal grain orientation difference is considered important for the properties of the hard phase and its improvement.

[0027] The coincidence grain boundaries between adjacent hard particles consist of Σ3 grain boundaries, Σ5 grain boundaries, Σ7 grain boundaries, Σ9 grain boundaries, Σ11 grain boundaries, Σ13 grain boundaries, Σ15 grain boundaries, Σ17 grain boundaries, Σ19 grain boundaries, Σ21 grain boundaries, Σ23 grain boundaries, Σ25 grain boundaries, Σ27 grain boundaries, and Σ29 grain boundaries, etc. Among them, the Σ3 grain boundary is considered to have the lowest grain boundary energy among the coincidence grain boundaries. The length of the Σ3 grain boundary indicates the total length of the Σ3 grain boundaries in the field of view observed by SEM equipped with EBSD. Also, the total length of the grain boundaries between adjacent hard particles is the sum of the total length of the crystal grain boundaries other than the coincidence grain boundaries and the total length of the coincidence grain boundaries.

[0028] In the internal region of the cermet, the ratio A of the length of the corresponding grain boundary to the total length of the grain boundaries between adjacent hard particles is 12% or more and 50% or less. When the ratio A is 12% or more, the bonding force between adjacent hard particles increases, suppressing the progress of wear due to particle detachment, resulting in excellent wear resistance. Also, since the generation and progress of cracks are suppressed, it is excellent in chipping resistance and defect resistance. Furthermore, when the ratio A is 50% or less, stress concentration on grain boundaries other than the corresponding grain boundary is alleviated, improving chipping resistance and making it excellent in defect resistance. Also, since the size of the detachment marks due to particle detachment tends to be small, the occurrence of uneven wear starting from this is suppressed, making it excellent in wear resistance. From the same perspective, the ratio A is more preferably 18% or more and 48% or less, even more preferably 20% or more and 42% or less, and still more preferably 21% or more and 34% or less. In this embodiment, the grain boundaries between adjacent hard particles and the corresponding grain boundaries of each Σ value can be measured, for example, by the method described in the examples below.

[0029] In the surface region of the cermet, the ratio B of the length of the corresponding grain boundary to the total length of the grain boundaries between adjacent hard particles is preferably 15% or more and 55% or less. When the ratio B is 15% or more, the bonding force between adjacent hard particles increases, suppressing the progress of wear due to particle detachment, resulting in a tendency towards excellent wear resistance. Also, since the generation and progress of cracks are suppressed, it has a tendency to be excellent in chipping resistance and defect resistance. Furthermore, when the ratio B is 55% or less, stress concentration on grain boundaries other than the corresponding grain boundary is alleviated, improving chipping resistance and making it excellent in defect resistance. Also, since the size of the detachment marks due to particle detachment tends to be small, the occurrence of uneven wear starting from this is suppressed, making it excellent in wear resistance. From the same perspective, the ratio B is more preferably 16% or more and 54% or less, and even more preferably 23% or more and 42% or less.

[0030] Preferably, the ratio (B / A) of the ratio B of the length of the corresponding grain boundary to 100% of the total length of the grain boundaries between adjacent hard particles in the surface region of the cermet to the ratio A of the length of the corresponding grain boundary to 100% of the total length of the grain boundaries between adjacent hard particles in the internal region of the cermet is 1.1 or more and 2.0 or less. When the ratio (B / A) is 1.1 or more, the thermal conductivity of the surface region is relatively improved, and the temperature rise in the internal region of the cermet during cutting is suppressed, so that the cermet tends to be excellent in plastic deformation resistance and wear resistance. Further, when the ratio (B / A) is 2.0 or less, the progress of cracks generated in the surface region of the cermet into the internal region is suppressed, so that the cermet tends to be excellent in defect resistance. From the same viewpoint, the ratio (B / A) is more preferably 1.2 or more and 1.9 or less, and even more preferably 1.2 or more and 1.6 or less.

[0031] In the internal region of the cermet, the ratio X of the length of the Σ3 grain boundary to 100% of the length of the corresponding grain boundary is preferably 20% or more and 50% or less. When the ratio X is 20% or more, plastic deformation due to grain boundary sliding is suppressed, so that the cermet tends to be excellent in wear resistance. Further, when the ratio X is 50% or less, the toughness is improved, and the cermet tends to be excellent in defect resistance. From the same viewpoint, the ratio X is more preferably 21% or more and 46% or less, even more preferably 22% or more and 46% or less, and still more preferably 23% or more and 36% or less.

[0032] In the surface region of the cermet, the ratio Y of the length of the Σ3 grain boundary to 100% of the length of the corresponding grain boundary is preferably 30% or more and 60% or less. When the ratio Y is 30% or more, plastic deformation due to grain boundary sliding is suppressed, so that the cermet tends to be excellent in wear resistance. Further, when the ratio Y is 60% or less, the toughness is improved, so that the cermet tends to be excellent in defect resistance. From the same viewpoint, the ratio Y is more preferably 31% or more and 58% or less, and even more preferably 33% or more and 57% or less.

[0033] In the surface region of the cermet, it is preferable that the ratio (Y / X) of the ratio Y of the length of the Σ3 grain boundary to 100% of the length of the corresponding grain boundary to the ratio X of the length of the Σ3 grain boundary to 100% of the length of the corresponding grain boundary in the internal region of the cermet is 1.2 or more and 2.5 or less. When the ratio (Y / X) is 1.2 or more, the thermal conductivity of the surface region is relatively improved, and the temperature rise in the internal region of the cermet during cutting is suppressed, so that it tends to be excellent in plastic deformation resistance and wear resistance. Further, when the ratio (Y / X) is 2.5 or less, the propagation of cracks generated in the surface region of the cermet to the internal region is suppressed, so that it tends to be excellent in defect resistance. From the same viewpoint, the ratio (Y / X) is more preferably 1.3 or more and 2.4 or less, and even more preferably 1.4 or more and 2.0 or less.

[0034] In the cermet of the present embodiment, the content ratio of the hard phase is 80.0% by volume or more and 94.0% by volume or less. When the content ratio of the hard phase is 80.0% by volume or more with respect to 100% by volume of the cermet, the hardness and plastic deformation resistance of the cermet are improved, and it is excellent in wear resistance. Further, when the content ratio of the hard phase is 94.0% by volume or less, the ratio of the binder phase relatively increases, so that the toughness of the cermet is improved and it is excellent in defect resistance. From the same viewpoint, the content ratio of the hard phase is preferably 80.8% by volume or more and 93.5% by volume or less, and more preferably 85.5% by volume or more and 91.2% by volume or less. The content ratios (volume %) of the hard phase and the binder phase in the cermet can be measured by the method described in the examples below.

[0035] [Binder phase] The binder phase of the present embodiment preferably contains at least one element selected from the group consisting of Co, Ni, and Fe, and is more preferably a phase containing at least one selected from the group consisting of Co and Ni, and even more preferably a phase consisting of Co and Ni.

[0036] In this embodiment, the content ratio of the bonding phase is 6.0% by volume or more and 20.0% by volume or less with respect to 100% by volume of the cermet. When the content ratio of the bonding phase is 6.0% by volume or more, the toughness of the cermet is improved and it has excellent defect resistance. When the content ratio of the bonding phase is 20.0% by volume or less, the ratio of the hard phase relatively increases, so the hardness and plastic deformation resistance of the cermet are improved and it has excellent wear resistance. From the same viewpoint, the content ratio of the bonding phase is preferably 6.5% by volume or more and 19.2% by volume or less, and more preferably 8.8% by volume or more and 14.5% by volume or less.

[0037] [Coated Cermet] The cermet of this embodiment is preferably a coated cermet further provided with a coating layer formed on the surface. By providing the coating layer, it tends to be even more excellent in wear resistance and defect resistance.

[0038] In the coated cermet of this embodiment, it is preferable that the average thickness of the entire coating layer is 0.5 μm or more and 20.0 μm or less. When the average thickness of the entire coating layer is 0.5 μm or more, the wear resistance tends to be further improved. When it is 20.0 μm or less, peeling of the coating layer is suppressed and the defect resistance tends to be further improved. From the same viewpoint, the average thickness of the entire coating layer is preferably 1.2 μm or more and 17.0 μm or less, and more preferably 3.0 μm or more and 9.5 μm or less.

[0039] In the coated cermet of this embodiment, it is preferable that the coating layer is a single layer or a laminate of two or more layers containing at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si and at least one element selected from the group consisting of C, N, O, and B. By making the coating layer contain the above elements, it tends to be even more excellent in wear resistance and defect resistance.

[0040] In the coating layer, when a plurality of layers are laminated, the average thickness of each layer is not particularly limited as long as the effects of the present invention are not inhibited. As the average thickness of each layer, for example, it may be 0.1 μm or more and 15.0 μm or less, it may be 0.2 μm or more and 10.0 μm or less, or it may be 0.5 μm or more and 5.0 μm or less.

[0041] The coating layer used in this embodiment is a single layer or a laminate of two or more layers containing at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si, and at least one element selected from the group consisting of C, N, O, and B. From the viewpoint of more effectively and surely achieving the effects of the present invention, as the compound layer in the coating layer, it is more preferable that it is a single layer or a laminate of two or more layers containing at least one element selected from the group consisting of Ti, V, Nb, Ta, Cr, W, Al, and Si, and at least one element selected from the group consisting of C, N, and B. It is even more preferable that it is a single layer or a laminate of two or more layers containing at least one element selected from the group consisting of Ti, Cr, Al, and Si, and at least one element selected from the group consisting of C and N. Specific examples of the compound layer in the coating layer are not particularly limited. For example, TiN layer, TiC layer, TiCN layer, TiCNO layer, TiCO layer, (Al 0.6 Ti 0.4 )N layer, (Al 0.5 Ti 0.5 )N layer, (Al 0.67 Ti 0.33 )N layer, (Ti 0.9 Si 0.1 )N layer, (Ti 0.5 Al 0.5 )N layer, (Ti 0.6 Al 0.3 W 0.1 )N layer, (Ti 0.9 Mo 0.1 )N layer, (Al 0.5 Cr 0.5 )N layer, (Al 0.7 Cr 0.3 )N layer, (Al 0.7 Cr 0.2 Ti 0.1)Examples include an N layer, a CrN layer, a NbN layer, and an (Al,Cr)2O3 layer.

[0042] The average thickness of each layer constituting the coating layer and the average thickness of the entire coating layer used in this embodiment can be measured from the cross-sectional structure of the coated cermet using an optical microscope, SEM, transmission electron microscope (TEM), etc. Note that the average thickness of each layer and the average thickness of the entire coating layer in the coated cermet of this embodiment can be obtained, for example, by measuring the thickness of each layer and the thickness of the entire coating layer from at least three or more cross-sections and calculating the average value.

[0043] Also, in the coated cermet of this embodiment, the composition of each layer constituting the coating layer can be determined by measurement using EDS, a wavelength dispersive X-ray analyzer (WDS), etc. from the cross-sectional structure of the coated cermet.

[0044] [Method for manufacturing cermet] The method for manufacturing the cermet of this embodiment includes, for example, the following steps 1 to 9.

[0045] Step 1 is a step of pulverizing each raw material powder to adjust the average particle size (pulverization step). In the pulverization step, for example, the raw material powders of Ti(C,N), TiC, and TiN may be pulverized until the average particle size becomes 0.5 to 4.0 μm, the raw material powders of WC, Mo2C, TaC, NbC, Cr3C2, VC, ZrC, and HfC may be pulverized until the average particle size becomes 0.10 to 0.25 μm, and Co, Ni, and Fe may be pulverized until the average particle size becomes 0.5 to 1.5 μm. The apparatus used in the pulverization step is not particularly limited, and examples include a bead mill. The time of the pulverization step using a bead mill is preferably, for example, 5 to 40 hours.

[0046] In the pulverization process, the particle size of the raw material powder can be adjusted. In the present embodiment, by making the average particle size of the raw material powder other than titanium carbide, nitride, and carbonitride smaller than the average particle size of the raw material powder of titanium carbide, nitride, and carbonitride, titanium carbide, nitride, and / or carbonitride are likely to be arranged in a specific orientation relationship during sintering, and the corresponding grain boundaries tend to be formed easily. Also, the distance between the particles of titanium carbide, nitride, and carbonitride in the molded article after molding can be reduced, and coarsening of the hard phase starting from the particles of titanium carbide, nitride, and carbonitride in the sintering process tends to be suppressed.

[0047] By appropriately adjusting the average particle size of each raw material powder, the above-mentioned ratio A can be controlled in the obtained cermet. For example, by reducing the average particle size of the raw material powder of the hard phase other than Ti(C,N), TiC, and TiN, and increasing the ratio of the average particle size of the raw material powder of Ti(C,N), TiC, and TiN to the average particle size of the raw material powder of the hard phase other than Ti(C,N), TiC, and TiN, the above-mentioned ratio A tends to increase.

[0048] Step 2 is a step (mixing step) of weighing and mixing an appropriate amount of the raw material powder obtained in Step 1.

[0049] Note that the average particle size of the raw material powder used in Step 1 and Step 2 can be measured by the Fisher method (Fisher Sub-Sieve Sizer (FSSS)) described in the American Society for Testing and Materials (ASTM) standard B330.

[0050] In the mixing step, by adjusting the mixing ratio of the raw material powder, it can be controlled to have the composition of the target cermet.

[0051] In the compounding process, when increasing the ratio of the compounding ratios of WC and Mo2C to the compounding ratios of Ti(C, N), TiC, and TiN, the total content ratio of W element and Mo element to the content ratio of Ti element in the hard phase can be increased. When increasing the total content ratio of W element and Mo element to the content ratio of Ti element in the hard phase, the above ratio X tends to increase.

[0052] Step 3 is a step (mixing step) of mixing the compounded raw material powder with a solvent by a wet ball mill. The time for performing the mixing step is not particularly limited, but for example, it is preferably 10 to 40 hours.

[0053] In the mixing step, the structure in the cermet can be made uniform.

[0054] Step 4 is a step (drying step) of drying the mixed powder. In the drying step, it is preferably heated and dried at a temperature of 100°C or lower, for example.

[0055] By the drying step, the solvent in the mixed powder can be evaporated.

[0056] Step 5 is a step (forming step) of forming the dried mixed powder. The obtained formed body is sintered in the following sintering step. In the forming step, specifically, for example, it is preferable to press and form the mixed powder using a mold having a predetermined tool shape. Further, in the forming step, for example, by adding paraffin, the formability tends to be improved.

[0057] By the forming step, a formed body having a predetermined tool shape is obtained.

[0058] Step 6 is a step (first heating step) of heating the formed body obtained in the forming step from room temperature to a predetermined temperature in a vacuum atmosphere. The reaching temperature of the first heating step is the starting temperature of the second heating step, and for example, it is preferably 1200 to 1400°C. In the first heating step, the pressure is preferably 70 Pa or lower.

[0059] The first heating step can promote degassing before the appearance of the liquid phase and immediately after the appearance of the liquid phase, and can improve the sinterability in the following sintering step.

[0060] Step 7 is a step (second heating step) of heating the green compact to a predetermined temperature (the reaching temperature) in an N2 gas atmosphere after the first heating step. The starting temperature of the second heating step is preferably, for example, 1200 to 1400 °C. The reaching temperature of the second heating step is the temperature of the sintering step and is preferably 1450 to 1550 °C. In the second heating step, the pressure is preferably 0.5 to 1.5 kPa. The heating rate is preferably in the range of 5 to 30 °C / min.

[0061] The second heating step can heat the green compact to the sintering temperature while suppressing denitrification from the green compact.

[0062] When the starting temperature of heating in the second heating step is increased, the ratio (Y / X) tends to increase. Also, when the ratio X and the ratio (Y / X) are increased, the ratio Y also increases.

[0063] Step 8 is a step (sintering step) of holding the green compact at a predetermined temperature in an N2 gas atmosphere after the second heating step. The sintering temperature is preferably 1450 to 1550 °C. In the sintering step, the pressure is preferably 24 to 40 kPa. The sintering time is preferably 240 to 420 minutes.

[0064] In the sintering step, a sintered body can be obtained by holding the green compact at a predetermined temperature. Also, by setting an N2 gas atmosphere of 24 kPa or more, deformation of the sintered body due to denitrification can be suppressed, and long-term holding becomes possible, and corresponding grain boundaries are likely to be formed. Also, if the pressure in the sintering step is lowered, the ratio (B / A) of the above ratio tends to increase. Furthermore, when controlling so that the above ratio A and the ratio (B / A) of the ratio increase, the above ratio B increases. Also, when the time of the sintering step is lengthened, the above ratio A tends to increase.

[0065] Step 9 is a step (cooling step) of cooling the obtained cermet to room temperature in an inert gas atmosphere after the sintering step. The cooling start temperature is the sintering temperature, and for example, it is preferably 1450 to 1550 °C. As the inert gas to be used, for example, He, Ne, or Ar is preferable. The pressure is preferably 133 Pa to 300 kPa.

[0066] By the cooling step, the obtained cermet can be cooled to room temperature.

[0067] [Method for forming the coating layer] In the coated cermet of the present embodiment, the coating layer may be formed by chemical vapor deposition or physical vapor deposition. Among them, it is preferable to form the coating layer by physical vapor deposition. Specifically, examples of the physical vapor deposition method include an arc ion plating method, an ion plating method, a sputtering method, and an ion mixing method. Among them, the arc ion plating method is preferable because the adhesion between the cermet and the coating layer is further excellent.

[0068] (Physical vapor deposition method) The cermet of the present embodiment processed into a predetermined shape such as a tool is accommodated in a reaction vessel of a physical vapor deposition apparatus, and the inside of the reaction vessel is evacuated until its pressure becomes a vacuum of 1.0×10− 2 Pa or less. After evacuation, the cermet is heated by a heater in the reaction vessel until its temperature becomes 200 °C or higher and 800 °C or lower. After heating, Ar gas is introduced into the reaction vessel to adjust the pressure in the reaction vessel to 0.5 Pa or higher and 5.0 Pa or lower. Under an Ar gas atmosphere with a pressure of 0.5 Pa or higher and 5.0 Pa or lower, a bias voltage of -1000 V or higher and -200 V or lower is applied to the cermet, and a current of 10 A or higher and 60 A or lower is passed through a tungsten filament in the reaction vessel to perform ion bombardment treatment on the surface of the cermet with Ar gas. After the ion bombardment treatment is performed on the surface of the cermet, the inside of the reaction vessel is evacuated until its pressure becomes a vacuum of 1.0×10− 2 Pa or less.

[0069] Next, control the cermet until its temperature reaches 200°C or higher and 600°C or lower. Then, introduce a reaction gas such as nitrogen gas into the reaction vessel together with Ar gas as required, and adjust the pressure in the reaction vessel to 0.5 Pa or higher and 5.0 Pa or lower. Then, apply a bias voltage of -150 V or higher and -10 V or lower to the cermet, and evaporate a metal evaporation source corresponding to the metal component of the coating layer by arc discharge of 80 A or higher and 180 A or lower to form a coating layer on the surface of the cermet. In this way, a coated cermet is obtained.

[0070] (Chemical vapor deposition method) A layer composed of compounds of each element constituting the coating layer may be formed on the surface of the cermet of the present embodiment processed into a tool shape by chemical vapor deposition.

[0071] For example, a Ti compound layer composed of a Ti nitride layer (TiN layer) may be formed by a chemical vapor deposition method with a raw material composition of TiCl4: 5.0 to 10.0 mol%, N2: 20 to 60 mol%, H2: the balance, a temperature of 850 to 950°C, and a pressure of 300 to 400 hPa.

[0072] Also, for example, a Ti compound layer composed of a Ti carbonitride layer (TiCN layer) may be formed by a chemical vapor deposition method with a raw material composition of TiCl4: 5.0 to 7.0 mol%, CH3CN: 0.5 to 1.5 mol%, H2: the balance, a temperature of 800 to 900°C, and a pressure of 60 to 80 hPa.

[0073] By sequentially laminating the above-described compound layers, a coating layer composed of a plurality of compound layers may be formed.

[0074] The cermet and coated cermet of this embodiment have excellent machining performance, especially in the cutting of steel, and thus can be suitably used as a constituent material of a tool. When the cermet and coated cermet of this embodiment are used as a constituent material of, for example, a cutting tool, they have excellent performance particularly in the cutting of steel. Further, when the cermet and coated cermet of this embodiment are used as a material of a tool (e.g., a cutting tool) for machining steel, the cermet and coated cermet have excellent wear resistance, plastic deformation resistance, and chipping resistance, and are thus particularly useful in terms of extending the tool life.

Examples

[0075] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

[0076] (Example 1: Invention Products 1 to 29 and Comparative Products 1 to 15) [Manufacture of Cermet Sintered Body] As raw material powders, commercially available Ti(C, N), TiC powder, TiN powder, WC powder, Mo2C powder, TaC powder, NbC powder, Cr3C2 powder, VC powder, ZrC powder, Co powder, and Ni powder were prepared.

[0077] Each of the prepared raw material powders was pulverized by a bead mill until it had an average particle size shown in Table 1 below. The average particle size of the raw material powder was measured by the Fisher method (Fisher Sub-Sieve Sizer (FSSS)) described in the American Society for Testing and Materials (ASTM) standard B330.

[0078] The obtained pulverized raw material powders were weighed so as to have the composition shown in Table 2 below, and each of the weighed raw material powders was put into a stainless steel pot together with an acetone solvent and cemented carbide balls and mixed by a wet ball mill. The mixing time by the wet ball mill was 15 hours.

[0079] After mixing by the wet ball mill, the mixture was dried at 80°C for 30 minutes to evaporate the acetone solvent and obtain a mixed powder.

[0080] After adding 5.0% by mass of paraffin to the obtained mixed powder, it was press-molded at a pressure of 100 MPa using a mold in which the shape after sintering was an insert of CNMG120408-TSF (manufactured by Tungaloy Corporation) to obtain a molded body.

[0081] The obtained molded body was heated from room temperature to the starting temperature of the second heating step shown in Table 3 in a vacuum atmosphere of 70 Pa or less (first heating step).

[0082] Thereafter, the molded body was heated in an N2 gas atmosphere from the starting temperature of the second heating step shown in Table 3 to 1500°C at a heating rate of 10°C per minute (second heating step). In the second heating step, the pressure was set to 1.0 kPa.

[0083] Thereafter, the molded body was held and sintered at 1500°C in an N2 gas atmosphere (sintering step). In the sintering step, the pressure and sintering time were as shown in Table 3.

[0084] The obtained cermet was cooled from 1500°C to room temperature in an Ar gas atmosphere of 250 kPa (cooling step).

[0085] The inventive articles 1 to 29 and comparative articles 1 to 15 were produced as described above.

Table 1

[0086]

Table 2

[0087]

Table 3

[0088] For the cermets of Invention Articles 1 to 29 and Comparative Articles 1 to 15, cross-sections perpendicular to the cermet surface were polished, and using SEM, the polished surface at a position 500 μm inside from the cermet surface was observed with a backscattered electron image. After identifying the hard phase and the binder phase using EDS attached to the SEM, a micrograph was taken. The magnification at this time was set to 4000 times, and a micrograph of a field of view containing a region of 20 μm × 20 μm was obtained. By analyzing the obtained micrograph using commercially available image analysis software, the ratio of the area occupied by the hard phase and the binder phase in the micrograph was determined. The same analysis was performed on micrographs of five different fields of view, and the arithmetic mean of the calculated ratios of the areas occupied by the hard phase and the binder phase was taken as the content ratio (volume %) of the hard phase and the binder phase in the cermet.

[0089] Furthermore, the average composition (atomic ratio) of the hard phase in the cermets of Invention Articles 1 to 29 and Comparative Articles 1 to 15 was determined by surface analysis using EDS. The analysis was performed in five fields of view where the micrographs used to determine the content ratio (volume %) of the hard phase and the binder phase were obtained. Based on the arithmetic mean of the content ratios of each element in the five obtained fields of view, the content ratio (atomic ratio) of each element to the total content ratio of Ti element and M element (M element represents W, Mo, Ta, Nb, Cr, V, and Zr elements), the content ratio (atomic ratio) of C element to the total content ratio of C element and N element, and the content ratio (atomic ratio) of the total content ratio of W element and Mo element to the content ratio of Ti element were calculated.

[0090] The crystal system of the hard phase in the cermets of Invention Articles 1 to 29 and Comparative Articles 1 to 15 was confirmed by performing X-ray diffraction measurement. Specifically, XRD measurement was performed, and it was confirmed that a hard phase having a cubic crystal having a diffraction peak derived from the (422) plane was present at a position of 121.0° or more and 125.0° or less. The above XRD measurement was carried out in the following manner in detail. Using an X-ray diffractometer SmartLab (product name) manufactured by Rigaku Corporation, X-ray diffraction with a 2θ / θ focusing method optical system using Cu-Kα rays was performed under the following conditions, and the peak intensities of the respective plane indices were measured. Here, the measurement conditions were: output: 45 kV, 200 mA, incident-side solar slit: 5°, divergence vertical slit: 2 / 3°, divergence vertical limiting slit: 5 mm, scattering slit 2 / 3°, receiving-side solar slit: 5°, receiving slit: 0.3 mm, sampling width: 0.02°, scan speed: 4° / min, 2θ measurement range: 20° to 140°.

[0091] The results obtained above are shown in Table 4.

[0092]

Table 4

[0093] [Length of grain boundary between adjacent hard particles and length of corresponding grain boundary] In the surface region and the internal region of the cermet, the length of the grain boundary between adjacent hard particles was measured as follows. A sample of the cermet was polished in a direction perpendicular to its surface to expose a cross-section. Further, the obtained cross-section was polished using colloidal silica to obtain a mirror-polished observation surface. This observation surface was observed using an SEM of SU6600 (manufactured by Hitachi High-Technologies Corporation) equipped with EBSD (manufactured by TexSEM Laboratories). The normal of the observation surface was inclined at 70° with respect to the incident beam, and the analysis was performed by irradiating an electron beam at an acceleration voltage of 15 kV and an irradiation current of 1.0 nA. Data collection was carried out at a step size of 0.1 μm / step for 1000×1000 measurement points in a measurement field corresponding to a 100 μm×100 μm surface area of the cermet on the observation surface. Data was collected such that the positions at 50 μm and 500 μm from the surface of the cermet towards the inside were the centers of the measurement fields, and they were used as data for the surface region and the internal region, respectively. The data processing was performed using commercially available software. When analyzing the crystal orientation of the hard particles, if the orientation difference between two adjacent measurement points is 5° or more, the boundary between these two points was defined as the grain boundary between adjacent hard particles, and the total length of the grain boundaries between adjacent hard particles and the length of the corresponding grain boundaries corresponding to any Σ value were determined. In each of the internal region and the surface region, the ratio of the length of the corresponding grain boundary to the total length of the grain boundaries between adjacent hard particles was calculated and designated as ratio A and ratio B. Furthermore, in each of the internal region and the surface region, the ratio of the length of the Σ3 grain boundary to the length of the corresponding grain boundary was calculated and designated as ratio X and ratio Y. The results are shown in Table 5.

[0094]

Table 5

[0095] Using the obtained Invention Products 1 to 29 and Comparative Products 1 to 15, Cutting Test 1 and Cutting Test 2 were conducted under the following conditions. The results are shown in Table 6.

[0096] [Cutting Test 1 (Wear Resistance Test)] · Workpiece material: S45C, · Workpiece material shape: round bar, · Cutting speed: 300 m / min, · Depth of cut: 1.0 mm, · Feed: 0.2 mm / rev, · Coolant: Wet, · Insert: CNMG120408 - TSF (manufactured by Tungaloy Corporation) · Evaluation item (wear resistance test): When the flank wear width of the tool reached 0.2 mm or the cutting edge of the tool became chipped, the tool life was defined as such, and the machining time until the tool life was measured.

[0097] [Cutting Test 2 (Chipping Resistance Test)] · Workpiece material: SCM415, · Workpiece material shape: round bar with two grooves equally spaced on the side, · Cutting speed: 150 m / min, · Depth of cut: 1.0 mm, · Feed: 0.10 mm / rev, · Coolant: Wet, · Insert: CNMG120408 - TSF (manufactured by Tungaloy Corporation) · Evaluation item (chipping resistance test): The tool life was defined as the time when the cutting edge of the tool reached chipping, and the number of impacts until the tool life was measured.

[0098] Regarding the machining time until the tool life of cutting test 1 (wear resistance test), if it was 30 minutes or more, it was evaluated as "A", if it was 20 minutes or more and less than 30 minutes, it was evaluated as "B", and if it was less than 20 minutes, it was evaluated as "C". Also, regarding the number of times until the tool life of cutting test 2 (chipping resistance test), if it was 13,000 times or more, it was evaluated as "A", if it was 9,000 times or more and less than 13,000 times, it was evaluated as "B", and if it was less than 9,000 times, it was evaluated as "C". In these evaluations, "A" is the most excellent, followed by "B", meaning that "C" is the most inferior. That the evaluation of the machining time of cutting test 1 is "A" or "B" and the evaluation of the number of times of cutting test 2 is "A" or "B" means that the cutting performance is excellent. The evaluation results are shown in Table 6.

[0099]

Table 6

[0100] From the results shown in Table 6, it was found that both the evaluation of the machining time and the evaluation of the number of machining times of the invention product were "A" or "B", indicating that it was excellent in both wear resistance and chipping resistance. On the other hand, for the comparative product, either one or both of the evaluation of the machining time and the evaluation of the number of machining times were "C", indicating that it was inferior in wear resistance and / or chipping resistance compared to the invention product. From the above results, it was found that the invention product had a long tool life as a result of being excellent in both wear resistance and chipping resistance.

[0101] (Example 2: Invention products 30 - 48) As a base material, a cermet prepared in the same manner as Invention Articles 1, 2, 5, 6, and 9 of Example 1 above was prepared. After subjecting the surface of the base material to ion bombardment treatment, a coating layer was formed by the arc ion plating method. The coating layer was formed to have the composition and average thickness shown in Table 7. Also, when forming a plurality of layers, they were formed on the surface of the cermet in the order of the first layer, the second layer, and the third layer. The method of forming the coating layer was as follows.

[0102] The cermets of Invention Articles 1, 2, 5, 6, and 9 were attached to a holder in a reaction vessel of an arc ion plating apparatus. The pressure in the reaction vessel was made a vacuum of 1.0×10 -2 Pa or less. The cermet was heated to 500 °C with a furnace heater. After heating, Ar gas was introduced into the reaction vessel so that the pressure became 3.0 Pa. After the introduction of the gas, while applying a bias voltage of -400 V to the base material, a current of 40 A was passed through a tungsten filament in the reaction vessel, and ion bombardment treatment with Ar gas was performed on the surface of the base material for 30 minutes. After the completion of the ion bombardment treatment, the inside of the reaction vessel was evacuated until the pressure became a vacuum of 5.0×10 -3 Pa or less.

[0103] After evacuation, the temperature of the cermet was controlled to 450 °C, and N2 gas was introduced into the reaction vessel to make the inside of the reaction vessel a nitrogen atmosphere with a pressure of 3.0 Pa. Here, only when forming the second layer of Invention Articles 30, 37, 40, 43, and 46, a mixed gas of N2 gas and acetylene (C2H2) gas with a volume ratio of 90:10 was introduced to make the pressure in the reaction vessel 2.7 Pa. Also, here, only when forming the coating layer of Invention Articles 35 and 36, the cermet temperature was controlled to 600 °C, and further, only when forming the coating layer of Invention Article 36, the pressure in the reaction vessel was made 5.0 Pa. Thereafter, a bias voltage of -60 V was applied to the cermet, and a metal evaporation source was evaporated by a 150 A arc discharge to form a coating layer on the surface of the cermet. Also, here, only when forming the coating layer of Invention Article 36, the applied bias voltage was made -30 V. As the metal evaporation source, one corresponding to the metal components of each layer shown in Table 7 was used. After forming the coating layer, the sample was cooled. After the sample temperature reached 100°C or lower, the sample was taken out from the reaction vessel.

[0104] Here, Invention Products 30 to 36 are those with a coating treatment on the surface of Invention Product 1, Invention Products 37 to 39 are those with a coating treatment on the surface of Invention Product 2, Invention Products 40 to 42 are those with a coating treatment on the surface of Invention Product 5, Invention Products 43 to 45 are those with a coating treatment on the surface of Invention Product 6, and Invention Products 46 to 48 are those with a coating treatment on the surface of Invention Product 9.

[0105] The composition of each layer of the coating layer was measured using EDS attached to the SEM in the cross-section near the position 50 μm from the cutting edge ridge line portion of the surface facing the metal evaporation source of the coated cermet toward the center. Also, the average thickness of each layer of the coating layer and the average thickness of the entire coating layer were obtained by observing at least three cross-sections in the above cross-section with SEM, measuring the thickness of each layer, and calculating the average value (arithmetic mean value). The results are shown in Table 7.

[0106] Also, using the obtained samples, a cutting test was conducted in the same manner as in Example 1, and Invention Products 30 to 45 were evaluated. The results are shown in Table 8.

[0107]

Table 7

[0108]

Table 8

[0109] From the results shown in Table 8, a coated cermet comprising the cermet of the present invention and a coating layer formed on the surface of the cermet, wherein the average thickness of the entire coating layer is 0.5 μm or more and 20.0 μm or less, and the coating layer is a single layer or a laminate of two or more layers containing at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al and Si and at least one element selected from the group consisting of C, N, O, and B. The coated cermet was found to be even more excellent in wear resistance and chipping resistance and to have a longer tool life.

Industrial Applicability

[0110] Since the cermet and the coated cermet of the present invention are excellent in wear resistance and chipping resistance, the tool life can be extended compared to the conventional ones, and thus they have high industrial applicability in this regard.

Claims

1. A cermet comprising a hard phase and a binder phase, wherein the content ratio of the hard phase is 80.0% by volume or more and 94.0% by volume or less, the content ratio of the binder phase is 6.0% by volume or more and 20.0% by volume or less, the hard phase is a phase containing a carbonitride containing Ti and at least one element selected from the group consisting of W, Mo, Cr, Ta, Nb, V, Hf, and Zr, the hard phase contains a cubic crystal structure, the binder phase is a phase containing at least one element selected from the group consisting of Co, Ni, and Fe, the hard phase consists of hard particles, a region more than 100 μm away from the surface of the cermet toward the inside is defined as the internal region, and in the internal region, when the ratio of the length of the corresponding grain boundary to the total length of the grain boundaries between adjacent hard particles is defined as ratio A, the ratio A is 12% or more and 50% or less, Cermet.

2. In the hard phase, the content ratio (atomic ratio) of Ti to the total content ratio of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is 0.65 or more and 0.90 or less, The cermet according to Claim 1.

3. In the internal region, when the ratio of the length of the Σ3 grain boundary to the length of the corresponding grain boundary with respect to 100% of the length of the corresponding grain boundary is defined as ratio X, the ratio X is 20% or more and 50% or less, The cermet according to Claim 1.

4. A region up to 100 μm from the surface of the cermet toward the inside is defined as the surface region, and in the surface region, when the ratio of the length of the corresponding grain boundary to the total length of the grain boundaries between adjacent hard particles is defined as ratio B, the ratio B is 15% or more and 55% or less, The cermet according to Claim 1.

5. The ratio (B / A) of the ratio B to the ratio A is 1.1 or more and 2.0 or less, The cermet according to Claim 4.

6. In the surface region, when the ratio of the length of the Σ3 grain boundary to the length of the corresponding grain boundary with respect to 100% of the length of the corresponding grain boundary is defined as ratio Y, the ratio Y is 30% or more and 60% or less, The cermet according to Claim 4.

7. In the internal region, when the ratio of the length of the Σ3 grain boundary to the length of the corresponding grain boundary with respect to 100% of the length of the corresponding grain boundary is defined as ratio X, the ratio (Y / X) of the ratio Y to the ratio X is 1.2 or more and 2.5 or less, The cermet according to Claim 6.

8. A coated cermet comprising the cermet according to Claim 1 and a coating layer formed on the surface of the cermet.

9. The average thickness of the entire coating layer is 0.5 μm or more and 20.0 μm or less, The coated cermet according to claim 8.

10. The coating layer is a single layer or a laminate of two or more layers containing at least one element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Al, and Si, and at least one element selected from the group consisting of C, N, O, and B. The coated cermet according to claim 8.

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