Cermets and coated cermets

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] This invention relates to cermets and coated cermets. [Background technology]

[0002] Conventionally, cutting tools have included cemented carbide tools with tungsten carbide (WC) as the main hard phase, TiCN-based cermet tools with titanium carbonitride (TiCN) as the main hard phase, and cBN sintered tools with cubic boron nitride as the main hard phase. Of these, cermet cutting tools have low affinity for steel and excellent wear resistance and surface finish, so they are mainly used in the cutting of steel. However, in recent years, there has been a trend towards higher efficiency in cutting processes, with a tendency towards higher cutting speeds, deeper cuts, and higher feed rates. Against this backdrop, there is a demand for TiCN-based cermet cutting tools that offer even better wear resistance and fracture resistance, and longer tool life.

[0003] In response to such demands, various cermet cutting tools have been proposed. For example, Patent Document 1 discloses a surface-coated cermet consisting of hard particles and a binder phase, wherein the average grain size of the hard particles in the surface layer is larger than the average grain size of the internal particles, and at least 20% of the hard particles in the surface layer have a grain size of 2 μm or larger, and the average grain size of the internal hard particles is 3 μm or less. By forming a surface coating layer consisting of at least one of the elements of Group 4a of the periodic table and Al carbides, nitrides, carbonitrides, or oxides on the surface of the cermet, wear resistance, chipping resistance, and thermal shock resistance can be greatly improved, and thermal shock resistance can also be improved during wet cutting. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 06-336634 [Overview of the project] [Problems that the invention aims to solve]

[0005] Thus, in recent years, attempts have been made to ensure that the average grain size of hard particles in the surface layer of surface-coated cermets is larger than the average grain size of hard particles in the interior, and that at least 20% of the hard particles in the surface layer have a grain size of 2 μm or larger, while the average grain size of hard particles in the interior is 3 μm or smaller. However, the bonding force between adjacent hard particles is not sufficient, and from the standpoint of preventing wear progression due to the detachment 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 aims to provide a cermet and a coated cermet that have excellent wear resistance and fracture resistance, thereby extending tool life when used as a tool material. [Means for solving the problem]

[0007] The inventors of this invention conducted extensive research on extending the tool life of cermets and discovered that by configuring cermets in a specific way, it is possible to improve their wear resistance and fracture resistance, thereby extending the tool life of cermets. This led to the completion of the present invention.

[0008] In other words, the gist of this invention is as follows: [1] A cermet comprising a hard phase and a binder phase, The content of the hard phase is 80.0% by volume or more and 94.0% by volume or less. The content of the aforementioned binding 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 includes cubic crystals, The bonding 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 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 is defined as ratio X with respect to 100% of the length of the corresponding grain boundary, the ratio X is from 20% to 50%. 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 is defined as ratio Y with respect to 100% of the length of the corresponding grain boundary, the ratio Y is 30% or more and 60% or less. The cermet according to [4] or [B]. [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 cubic crystals, 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. The region beyond 100 μm from the surface of the cermet is defined as the internal region. In the internal region, when the ratio of the length of a corresponding grain boundary to 100% of the total length of grain boundaries between adjacent hard particles is defined as ratio A, then ratio A is between 12% and 50%.

[0012] The factors that contribute to the improved wear resistance, plastic deformation resistance, and fracture resistance of such cermets are not fully understood, but are presumed to be as follows. However, the factors are not limited to those listed below. When the hard phase content is 80.0% by volume or more relative to 100% by volume of cermet, the hardness and resistance to plastic deformation of the cermet are improved, resulting in excellent wear resistance. When the hard phase content is 94% by volume or less, the proportion of the binding phase increases relatively, improving the toughness of the cermet and resulting in excellent chipping resistance. When the binder phase content is 6.0 volume% or more relative to 100 volume% of the cermet, the toughness of the cermet improves, and its fracture resistance is excellent. When the binder phase content is 20.0 volume% or less, the proportion of the hard phase increases relatively, so the hardness and resistance to plastic deformation of the cermet improve, and its wear resistance is excellent. 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, resulting in excellent wear resistance and chipping resistance. The hard phase contains cubic crystals, which improves its hardness and thus its wear resistance. The bonding phase contains at least one element selected from the group consisting of Co, Ni, and Fe, resulting in excellent wear resistance and fracture 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% of the total length of the grain boundaries between adjacent hard particles, 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 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% of the total length of the grain boundaries between adjacent hard particles, 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, resulting in excellent wear resistance. Combined with these effects, the cermet of this embodiment has improved wear resistance, plastic deformation resistance, and defect resistance.

[0013] In this 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 consists 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 this 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. The hard phase being a phase containing the carbonitride improves the wear resistance and fracture resistance of the cermet. From a similar viewpoint, the hard phase contains at least Ti, preferably contains Ti and W, more preferably contains Ti, W, and Mo, and even more preferably contains Ti, W, Mo, Nb, and Zr. The hard phase is preferably 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 carbonitride of Ti and at least one element selected from the group consisting of W, Mo, Cr, Ta, Nb, V, Hf, and Zr; even more preferably a carbonitride of Ti and at least one element selected from the group consisting of W, Mo, Cr, Ta, Nb, V, and Zr; and even more preferably a carbonitride of Ti and at least one element selected from the group consisting of W, Mo, Nb, and Zr.

[0015] In the hard phase, the proportion of Ti (atomic ratio) relative to the total proportion of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is preferably 0.65 or more and 0.90 or less. When the Ti content is 0.65 or more, the reactivity with the workpiece decreases, and wear resistance tends to improve. Furthermore, when the Ti content is 0.90 or less, the toughness of the cermet improves, and fracture resistance tends to improve. From a similar viewpoint, the Ti content is more preferably 0.68 or more and 0.88 or less, and even more preferably 0.70 or more and 0.86 or less.

[0016] In the hard phase, a W content (atomic ratio) relative to the total content of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is preferably 0.03 to 0.30, as this tends to improve the wear resistance and fracture resistance of the cermet. A W content of 0.03 or higher improves the toughness of the cermet, thus further improving its fracture resistance. Furthermore, a W content of 0.30 or lower improves the thermal conductivity of the cermet, thus further improving its wear resistance. From a similar viewpoint, a W content of 0.04 to 0.22 is more preferable, and 0.05 to 0.14 is even more preferable.

[0017] In the hard phase, a Mo content (atomic ratio) relative to the total content of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is preferably 0.00 to 0.05, as this tends to improve the wear resistance and fracture resistance of the cermet. When the Mo content is greater than 0.00, the heat resistance of the cermet improves, and therefore the wear resistance and fracture resistance tend to improve even further. Furthermore, when the Mo content is 0.10 or less, the thermal conductivity of the cermet improves, and therefore the wear resistance tends to improve even further. From a similar viewpoint, a Mo content of 0.01 to 0.02 is more preferable.

[0018] In the hard phase, a ratio of Ta content (atomic ratio) to the total content of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is preferably 0.00 or more and 0.20 or less, as this tends to improve the wear resistance and fracture resistance of the cermet. When the above Ta content is greater than 0.00, the heat resistance of the cermet improves, and therefore the wear resistance and fracture resistance tend to improve even further. Furthermore, when the above Ta content is 0.20 or less, the thermal conductivity of the cermet improves, and therefore the wear resistance tends to improve even further. From a similar viewpoint, it is more preferable that the above Ta content is greater than 0.00 and 0.15 or less, and even more preferable that it is greater than 0.00 and 0.09 or less.

[0019] In the hard phase, a ratio of Nb content (atomic ratio) to the total content of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is preferably 0.00 to 0.20, as this tends to improve the wear resistance and fracture resistance of the cermet. When the Nb content is greater than 0.00, the heat resistance of the cermet improves, and therefore the wear resistance and fracture resistance tend to improve even further. Furthermore, when the Nb content is 0.20 or less, the thermal conductivity of the cermet improves, and therefore the wear resistance tends to improve even further. From a similar viewpoint, a Nb content of 0.06 to 0.16 is more preferable, and 0.06 to 0.15 is even more preferable.

[0020] In the hard phase, a Cr content (atomic ratio) relative to the total content of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is preferably 0.00 to 0.05, as this tends to improve the wear resistance and fracture resistance of the cermet. A Cr content greater than 0.00 improves the heat resistance of the cermet, thus further improving wear resistance and fracture resistance. Furthermore, a Cr content of 0.05 or less improves the sinterability of the cermet, thus further improving wear resistance and fracture resistance. From a similar viewpoint, a Cr content greater than 0.00 and less than or equal to 0.02 is more preferable, and even more preferable than 0.00 and less than or equal to 0.01.

[0021] In the hard phase, a V content ratio (atomic ratio) relative to the total content ratio of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is preferably 0.00 to 0.05, as this tends to improve the wear resistance and fracture resistance of the cermet. When the V content ratio is greater than 0.00, the heat resistance of the cermet improves, and therefore the wear resistance and fracture resistance tend to improve even further. Furthermore, when the V content ratio is 0.05 or less, the sinterability of the cermet improves, and therefore the wear resistance and fracture resistance tend to improve even further. From a similar viewpoint, a V content ratio of 0.01 to 0.02 is more preferable.

[0022] In the hard phase, a Zr content (atomic ratio) relative to the total content of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is preferably 0.00 to 0.03, as this tends to improve the wear resistance and / or fracture resistance of the cermet. When the Zr content is greater than 0.00, the plastic deformation resistance of the cermet improves, and therefore the wear resistance tends to improve even further. Furthermore, when the Zr content is 0.03 or less, the sinterability of the cermet improves, and therefore the wear resistance and fracture resistance tend to improve even further. From a similar viewpoint, a Zr content of 0.01 to 0.02 is more preferable.

[0023] In the hard phase, the atomic ratio (C / (C+N)) of the content of element C to the total content of elements C and N is preferably 0.40 or more and 0.75 or less. When the above atomic ratio (C / (C+N)) is 0.40 or more, the hardness of the cermet is improved, and the wear resistance tends to be further improved. Also, when the above atomic ratio (C / (C+N)) is 0.75 or less, the reactivity of the cermet with the workpiece is reduced, and the wear resistance tends to be further improved. From a similar viewpoint, the content of W is more preferably 0.41 or more and 0.69 or less, even more 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 ((W+Mo) / Ti) of the total content of W and Mo elements to the content of Ti is preferably 0.03 or more and 0.40 or less. When the above atomic ratio ((W+Mo) / Ti) is 0.03 or more, the proportion X described later tends to be larger. Furthermore, when the above atomic ratio ((W+Mo) / Ti) is 0.40 or less, the thermal conductivity of the cermet is improved, and thus the wear resistance tends to be further improved. From a similar viewpoint, the content of W is more preferably 0.06 or more and 0.35 or less, even more preferably 0.10 or more and 0.24 or less, and even more preferably 0.12 or more and 0.21 or less.

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

[0026] The hard phase in this embodiment has grain boundaries with relatively high grain boundary energy and grain boundaries with relatively low grain boundary energy. Normally, grain boundaries have many gaps and relatively high grain boundary energy because the arrangement of atoms is irregular and randomly arranged. On the other hand, some grain boundaries have regular arrangements of atoms and few gaps, and such grain boundaries have relatively low grain boundary energy. A typical example of such a grain boundary with relatively low grain boundary energy is the coincidence site lattice grain boundary, also called a corresponding grain boundary. The Σ value is known as an index that indicates the degree of distribution of corresponding grain boundaries, and it is defined as the ratio of the density of lattice points of two crystal grains touching at a grain boundary to the density of lattice points that coincide when both crystal lattices are superimposed. In the case of simple structures, it is generally observed that grain boundaries with low Σ values ​​tend to have low interface energy and special properties. Therefore, controlling the proportion of corresponding grain boundaries and the distribution of grain orientation differences is considered important for the properties of the hard phase and for improving them.

[0027] Corresponding grain boundaries between adjacent hard particles include 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. Among these, the Σ3 grain boundary is considered to have the lowest grain boundary energy among the corresponding grain boundaries. The length of the Σ3 grain boundary refers to the total length of the Σ3 grain boundaries in the field of view observed by a SEM equipped with EBSD. Furthermore, the total length of grain boundaries between adjacent hard particles is the sum of the total length of grain boundaries other than corresponding grain boundaries and the total length of corresponding grain boundaries.

[0028] In the interior region of the cermet, the ratio A of the length of a corresponding grain boundary to 100% of the total length of grain boundaries between adjacent hard particles is 12% or more and 50% or less. When ratio A is 12% or more, the bonding force between adjacent hard particles is increased, suppressing the progression of wear due to particle detachment, thus providing excellent wear resistance. Furthermore, crack initiation and propagation are suppressed, resulting in excellent chipping and fracture resistance. Moreover, when ratio A is 50% or less, stress concentration at grain boundaries other than the corresponding grain boundary is reduced, improving chipping resistance and providing excellent fracture resistance. In addition, the size of detachment marks due to particle detachment tends to be smaller, suppressing the occurrence of uneven wear originating from these marks, resulting in excellent wear resistance. From a similar viewpoint, ratio A is more preferably 18% or more and 48%, even more preferably 20% or more and 42%, and even more preferably 21% or more and 34%. In this embodiment, the grain boundaries between adjacent hard particles and the corresponding grain boundaries for each Σ value can be measured, for example, by the method described in the later examples.

[0029] In the surface region of the cermet, the ratio B of the length of a corresponding grain boundary to 100% of the total length of grain boundaries between adjacent hard particles is preferably 15% to 55%. When the ratio B is 15% or more, the bonding force between adjacent hard particles is increased, which suppresses the progression of wear due to particle detachment, and thus tends to result in excellent wear resistance. Furthermore, since the occurrence and propagation of cracks are suppressed, it also tends to result in excellent chipping resistance and fracture resistance. Moreover, when the ratio B is 55% or less, stress concentration at grain boundaries other than the corresponding grain boundary is reduced, which improves chipping resistance and results in excellent fracture resistance. Furthermore, since the size of detachment marks due to particle detachment tends to be smaller, the occurrence of uneven wear starting from these marks is suppressed, and wear resistance is also excellent. From a similar viewpoint, the ratio B is more preferably 16% to 54%, and even more preferably 23% to 42%.

[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 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 grain boundaries between adjacent hard particles in the internal region of the cermet is between 1.1 and 2.0. When the above ratio (B / A) is 1.1 or higher, the thermal conductivity of the surface region is relatively improved, and the temperature rise of the internal region of the cermet during cutting is suppressed, so it tends to have excellent resistance to plastic deformation and wear resistance. Furthermore, when the above ratio (B / A) is 2.0 or lower, the propagation of cracks that occur in the surface region of the cermet into the internal region is suppressed, so it tends to have excellent resistance to chipping. From a similar viewpoint, it is more preferable that the above ratio (B / A) is between 1.2 and 1.9, and even more preferable that it is between 1.2 and 1.6.

[0031] In the internal region of the cermet, the ratio X of the length of the Σ3 grain boundaries to 100% of the length of the corresponding grain boundaries is preferably 20% or more and 50% or less. When the above ratio X is 20% or more, plastic deformation due to grain boundary sliding is suppressed, and the material tends to have excellent wear resistance. Furthermore, when the above ratio X is 50% or less, toughness is improved, and the material tends to have excellent fracture resistance. From a similar viewpoint, the above ratio X is more preferably 21% or more and 46%, even more preferably 22% or more and 46%, and even more preferably 23% or more and 36%.

[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 above ratio Y is 30% or more, plastic deformation due to grain boundary sliding is suppressed, and the material tends to have excellent wear resistance. Furthermore, when the above ratio Y is 60% or less, toughness is improved, and the material tends to have excellent chipping resistance. From a similar viewpoint, the above ratio Y is more preferably 31% or more and 58%, and even more preferably 33% or more and 57%.

[0033] Preferably, the ratio (Y / X) of the ratio Y of the length of the Σ3 grain boundaries to 100% of the length of the corresponding grain boundaries in the surface region of the cermet to the ratio X of the length of the Σ3 grain boundaries to 100% of the length of the corresponding grain boundaries in the internal region of the cermet is between 1.2 and 2.5. When the above ratio (Y / X) is 1.2 or higher, 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 it tends to have excellent resistance to plastic deformation and wear resistance. Furthermore, when the above ratio (Y / X) is 2.5 or lower, the propagation of cracks that occur in the surface region of the cermet into the internal region is suppressed, so it tends to have excellent resistance to chipping. From a similar viewpoint, it is more preferable that the above ratio (Y / X) is between 1.3 and 2.4, and even more preferable that it is between 1.4 and 2.0.

[0034] In the cermet of this embodiment, the hard phase content is 80.0% by volume or more and 94.0% by volume or less. When the hard phase content is 80.0% by volume or more relative to 100% by volume of cermet, the hardness and plastic deformation resistance of the cermet are improved, and it exhibits excellent wear resistance. Furthermore, when the hard phase content is 94.0% by volume or less, the proportion of the binder phase increases relatively, so the toughness of the cermet is improved, and it exhibits excellent fracture resistance. From a similar viewpoint, the hard phase content 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 hard phase and binder phase content (by volume %) in the cermet can be measured by the method described in the examples below.

[0035] [Binded phase] The bonding phase of this embodiment contains at least one element selected from the group consisting of Co, Ni, and Fe, preferably a phase containing at least one element selected from the group consisting of Co and Ni, and more preferably a phase consisting of Co and Ni.

[0036] The binder phase content in this embodiment is 6.0% to 20.0% by volume relative to 100% by volume of cermet. When the binder phase content is 6.0% by volume or more, the toughness of the cermet is improved and it exhibits excellent fracture resistance. When the binder phase content is 20.0% by volume or less, the proportion of the hard phase is relatively increased, so the hardness and resistance to plastic deformation of the cermet are improved and it exhibits excellent wear resistance. From a similar viewpoint, the binder phase content is preferably 6.5% to 19.2% by volume, and more preferably 8.8% to 14.5% by volume.

[0037] [Coated cermet] The cermet of this embodiment is preferably a coated cermet further comprising a coating layer formed on its surface. By including the coating layer, the abrasion resistance and fracture resistance tend to be even better.

[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. An average thickness of 0.5 μm or more of the entire coating layer tends to further improve abrasion resistance, and an average thickness of 20.0 μm or less tends to suppress peeling of the coating layer and further improve fracture resistance. From a similar viewpoint, it is preferable that the average thickness of the entire coating layer be 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 using a coating layer containing the above elements, the wear resistance and fracture resistance tend to be further improved.

[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 it does not inhibit the effects of the present invention. 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, and 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 0.1Examples include the N layer, CrN layer, NbN layer, and (Al,Cr)2O3 layer.

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

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

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

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

[0046] In the grinding process, the particle size of the raw material powder can be adjusted. In this embodiment, by making the average particle size of the raw material powders other than Ti carbides, nitrides, and carbonitrides smaller than the average particle size of the raw material powders of Ti carbides, nitrides, and carbonitrides, the Ti carbides, nitrides, and / or carbonitrides tend to arrange in specific orientation relationships during sintering, and corresponding grain boundaries tend to form more easily. In addition, the distance between Ti carbides, nitrides, and carbonitride particles in the molded product after molding can be reduced, and the coarsening of the hard phase starting from the Ti carbides, nitrides, and carbonitride particles during the sintering process tends to be suppressed.

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

[0048] Step 2 is the process of weighing an appropriate amount of the raw material powder obtained in Step 1 and blending it (blending process).

[0049] The average particle size of the raw material powders used in steps 1 and 2 can be measured using the Fisher Sub-Sieve Sizer (FSSS) method described in ASTM standard B330.

[0050] In the compounding process, the composition of the cermet can be controlled to achieve the desired result by adjusting the mixing ratio of the raw material powders.

[0051] In the compounding process, increasing the proportion of WC and Mo2C relative to the proportions of Ti(C,N), TiC, and TiN increases the total proportion of W and Mo relative to the Ti content in the hard phase. Increasing the total proportion of W and Mo relative to the Ti content in the hard phase tends to increase the above-mentioned ratio X.

[0052] Step 3 is a mixing step in which the blended raw material powder is mixed with a solvent using a wet ball mill. The time required for the mixing step is not particularly limited, but it is preferably 10 to 40 hours.

[0053] The mixing process allows for a homogenization of the structure in the cermet.

[0054] Step 4 is a drying step (drying step) of the mixed powder. The drying step is preferably carried out by heating and drying at a temperature of 100°C or lower.

[0055] The drying process allows the solvent in the mixed powder to be evaporated.

[0056] Step 5 is the process of molding the dried mixed powder (molding process). The resulting molded body is sintered in the following sintering process. Specifically in the molding process, it is preferable to press and mold the mixed powder using a mold that has a predetermined tool shape. Furthermore, in the molding process, adding paraffin, for example, tends to improve moldability.

[0057] A molded body having a predetermined tool shape is obtained through the molding process.

[0058] Step 6 is a step (first heating step) in which the molded body obtained in the molding step is heated from room temperature to a predetermined temperature in a vacuum atmosphere. The temperature reached in the first heating step is the starting temperature of the second heating step, and is preferably 1200 to 1400°C. In the first heating step, the pressure is preferably 70 Pa or less.

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

[0060] Step 7 is a step (second heating step) in which the molded body is heated to a predetermined temperature (target temperature) in an N2 gas atmosphere after the first heating step. The starting temperature of the second heating step is preferably 1200 to 1400°C. The target 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 allows the temperature to be raised to the sintering temperature while suppressing denitrification from the molded product.

[0062] Increasing the starting temperature for the second heating process tends to increase the above ratio (Y / X). Also, increasing both the proportion X and the ratio (Y / X) increases the proportion Y.

[0063] Step 8 is a step (sintering step) in which the molded body is held at a predetermined temperature in an N2 gas atmosphere after the second heating step. The sintering temperature is preferably 1450 to 1550°C. The pressure during the sintering step is preferably 24 to 40 kPa. The sintering time is preferably 240 to 420 minutes.

[0064] In the sintering process, a sintered body can be obtained by holding the molded body at a predetermined temperature. Furthermore, by using an N2 gas atmosphere of 24 kPa or higher, deformation of the sintered body due to denitrification can be suppressed, allowing for longer holding times and facilitating the formation of corresponding grain boundaries. In addition, lowering the pressure in the sintering process tends to increase the ratio (B / A) of the above proportions. Moreover, when controlling the process to increase both the above proportion A and the ratio (B / A), the above proportion B increases. Furthermore, increasing the sintering time also tends to increase the above proportion A.

[0065] Step 9 is a cooling step in which the cermet obtained after the sintering step is cooled to room temperature in an inert gas atmosphere. The starting temperature for cooling is the sintering temperature, which is preferably 1450 to 1550°C. The inert gas used is preferably He, Ne, or Ar. The pressure is preferably 133 Pa to 300 kPa.

[0066] The resulting cermet can be cooled to room temperature through the cooling process.

[0067] [Method for forming a coating layer] In the coated cermet of this embodiment, the coating layer may be formed by chemical vapor deposition or by physical vapor deposition. Among these, it is preferable to form the coating layer by physical vapor deposition. Specific examples of physical vapor deposition methods include arc ion plating, ion plating, sputtering, and ion mixing. Among these, arc ion plating is preferred because it provides superior adhesion between the cermet and the coating layer.

[0068] (Physical vapor deposition method) The cermet of this embodiment, processed into a predetermined shape such as a tool, is placed inside the reaction vessel of a physical vapor deposition apparatus, and the pressure inside the reaction vessel is 1.0 × 10⁻⁶ 2 The system is evacuated until a vacuum of less than Pa is achieved. After evacuating, the cermet is heated using a heater in the reaction vessel until its temperature is between 200°C and 800°C. After heating, Ar gas is introduced into the reaction vessel to adjust the pressure inside the vessel to between 0.5 Pa and 5.0 Pa. Under an Ar gas atmosphere with a pressure of between 0.5 Pa and 5.0 Pa, a bias voltage of between -1000V and -200V is applied to the cermet, and a current of between 10A and 60A is passed through the tungsten filament in the reaction vessel to perform ion bombardment treatment on the surface of the cermet with Ar gas. After ion bombardment treatment on the surface of the cermet, the pressure inside the reaction vessel is reduced to 1.0 × 10⁻⁶. 2 Vacuum is drawn until a vacuum of less than Pa is achieved.

[0069] Next, the cermet's temperature is controlled to between 200°C and 600°C. Then, a reaction gas such as nitrogen gas is introduced into the reaction vessel along with Ar gas as needed, and the pressure inside the reaction vessel is adjusted to between 0.5 Pa and 5.0 Pa. A bias voltage of between -150 V and -10 V is then applied to the cermet, and a metal evaporation source corresponding to the metal component of the coating layer is evaporated by an arc discharge of between 80 A and 180 A to form a coating layer on the surface of the cermet. In this way, a coated cermet is obtained.

[0070] (Chemical vapor deposition) On the surface of the cermet of this embodiment, which has been machined into a tool shape, a layer consisting of compounds of each element constituting the coating layer may be formed by chemical vapor deposition.

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

[0072] Furthermore, for example, a Ti compound layer consisting of a Ti carbonitride layer (TiCN layer) may be formed by chemical vapor deposition using a raw material composition of TiCl4: 5.0-7.0 mol%, CH3CN: 0.5-1.5 mol%, H2: the remainder, at a temperature of 800-900°C and a pressure of 60-80 hPa.

[0073] A coating layer composed of multiple compound layers may be formed by sequentially stacking the compound layers described above.

[0074] The cermet and coated cermet of this embodiment have excellent machining performance, particularly in the cutting of steel, and are therefore suitable for use as component materials for tools. When the cermet and coated cermet of this embodiment are used, for example, as component materials for cutting tools, they exhibit particularly excellent performance in the cutting of steel. Furthermore, when the cermet and coated cermet of this embodiment are used as materials for tools for processing steel (e.g., cutting tools), the cermet and coated cermet have excellent wear resistance, plastic deformation resistance, and chipping resistance, making them particularly useful in extending tool life. [Examples]

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

[0076] (Example 1: Inventions 1-29 and Comparative Products 1-15) [Manufacturing of cermet sintered bodies] As raw material powders, we prepared 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.

[0077] Each of the prepared raw material powders was ground using a bead mill until it reached the average particle size shown in Table 1 below. The average particle size of the raw material powders was measured using the Fisher Sub-Sieve Sizer (FSSS) method as described in ASTM standard B330.

[0078] The obtained pulverized raw material powders were weighed to achieve the blending composition shown in Table 2 below. Each weighed raw material powder was then placed in a stainless steel pot with acetone solvent and cemented carbide balls and mixed using a wet ball mill. The mixing time in the wet ball mill was 15 hours.

[0079] After mixing using a 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, the mixture was press-molded at a pressure of 100 MPa using a mold that would produce an insert with the shape of CNMG120408-TSF (manufactured by Tungaloy Corporation) after sintering, to obtain a molded body.

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

[0082] Subsequently, 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). The pressure during the second heating step was 1.0 kPa.

[0083] Subsequently, the molded body was sintered in an N2 gas atmosphere at 1500°C (sintering process). The pressure and sintering time during the sintering process were as shown in Table 3.

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

[0085] Inventions 1-29 and comparative products 1-15 were prepared in the manner described above. [Table 1]

[0086] [Table 2]

[0087] [Table 3]

[0088] For the cermets of Inventions 1-29 and Comparatives 1-15, a cross section perpendicular to the cermet surface was polished, and the polished surface at a position 500 μm inward from the cermet surface was observed using a backscattered electron image with a scanning electron microscope (SEM). After identifying the hard phase and binder phase using an EDS attached to the SEM, micrographs were taken. The magnification was set to 4000x, and micrographs were obtained with a field of view that included an area of ​​20 μm × 20 μm. The obtained micrographs were analyzed using commercially available image analysis software to determine the proportion of area occupied by the hard phase and binder phase in the micrograph. The same analysis was performed on micrographs of five different fields of view, and the arithmetic mean of the calculated proportions of area occupied by the hard phase and binder phase was taken as the content (volume %) of the hard phase and binder phase in the cermet.

[0089] Furthermore, the average composition (atomic ratio) of the hard phase in the cermets of Inventions 1-29 and Comparative Products 1-15 was determined by surface analysis using EDS. The analysis was performed on five fields from which microstructure photographs used to determine the content percentage (volume %) of the hard phase and binder phase were obtained. Based on the arithmetic mean of the content percentages of each element in the five obtained fields, the content percentage (atomic ratio) of each element relative to the total content percentage of Ti and M elements (M elements represent W, Mo, Ta, Nb, Cr, V, and Zr elements), the content percentage (atomic ratio) of C element relative to the total content percentage of C and N elements, and the content percentage (atomic ratio) of W and Mo elements relative to the content percentage of Ti element were calculated.

[0090] The crystalline structure of the hard phase in the cermets of Inventions 1-29 and Comparatives 1-15 was confirmed by X-ray diffraction measurements. Specifically, XRD measurements were performed to confirm the presence of a hard phase with cubic crystals exhibiting diffraction peaks originating from the (422) plane at positions between 121.0° and 125.0°. The above XRD measurements were performed in detail as follows. Using an X-ray diffractometer SmartLab (product name) manufactured by Rigaku Corporation, X-ray diffraction of a 2θ / θ focusing optical system using Cu-Kα rays was performed under the following conditions, and the peak intensity of each of the above-mentioned plane indices was measured. The measurement conditions were as follows: output: 45kV, 200mA, incident solar slit: 5°, diverging longitudinal slit: 2 / 3°, diverging longitudinal limiting slit: 5mm, scattering slit: 2 / 3°, receiving solar slit: 5°, receiving slit: 0.3mm, sampling width: 0.02°, scan speed: 4° / min, 2θ measurement range: 20°~140°.

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

[0092] [Table 4]

[0093] [Length of grain boundaries between adjacent hard particles and length of corresponding grain boundaries] The length of grain boundaries between adjacent hard particles in the surface and interior regions of the cermet was measured as follows: A cermet sample was polished perpendicular to its surface to expose the cross-section. The obtained cross-section was then polished with colloidal silica to obtain a mirror-polished observation surface. This observation surface was observed using a SEM (Scanning Enzyme Microscope) SU6600 (Hitachi High-Technologies Corporation) equipped with an EBSD (TexSEM Laboratories). The normal to the observation surface was tilted at 70° to the incident beam, and the analysis was performed by irradiating the electron beam with an accelerating voltage of 15kV and an irradiation current of 1.0nA. Data was collected at 1000×1000 measurement points in the measurement field of view corresponding to a 100μm×100μm surface area of ​​the cermet on the observation surface, with a step size of 0.1μm / step. Data was collected so that the measurement field of view was centered at positions 50μm and 500μm from the surface of the cermet toward the interior, and these were designated as data for the surface region and the interior region, respectively. Data processing was performed using commercially available software. When analyzing the crystal orientation of hard particles, if the orientation difference between two adjacent measurement points was 5° or more, the boundary between those two points was defined as a grain boundary between adjacent hard particles, and the total length of the grain boundary between adjacent hard particles and the length of the corresponding grain boundary for an arbitrary Σ value were determined. In both the internal and surface regions, the ratio of the length of the corresponding grain boundary to 100% of the total length of the grain boundaries between adjacent hard particles was calculated and designated as ratio A and ratio B. Furthermore, in both the internal and surface regions, the ratio of the length of the Σ3 grain boundary to 100% of 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 inventions 1-29 and comparative products 1-15, cutting tests 1 and 2 were conducted under the following conditions. The results are shown in Table 6.

[0096] [Cutting Test 1 (Abrasion Resistance Test)] ·Work material: S45C, • Workpiece shape: round bar, ·Cutting speed: 300m / min, • Cutting depth: 1.0 mm, Feed rate: 0.2mm / rev, • Coolant: Wet, • Insert: CNMG120408-TSF (manufactured by Tungaloy Corporation) • Evaluation item (wear resistance test): Tool life was defined as the point at which the wear width of the tool's flank surface reached 0.2 mm, or when the cutting edge of the tool broke off. The machining time until tool life was measured.

[0097] [Cutting Test 2 (Fracture Resistance Test)] ·Work material: SCM415, • Workpiece shape: A round bar with two grooves spaced evenly apart on its side. ·Cutting speed: 150m / min, • Cutting depth: 1.0 mm, Feed rate: 0.10mm / rev, • Coolant: Wet, • Insert: CNMG120408-TSF (manufactured by Tungaloy Corporation) • Evaluation item (fracture resistance test): Tool life was defined as the point at which the cutting edge of the tool broke, and the number of impacts until tool life was measured.

[0098] For Cutting Test 1 (wear resistance test), the machining time until tool life was reached was evaluated as follows: 30 minutes or more was rated "A", 20 minutes or more but less than 30 minutes was rated "B", and less than 20 minutes was rated "C". Similarly, for Cutting Test 2 (fracture resistance test), the number of cycles until tool life was reached was evaluated as follows: 13,000 or more was rated "A", 9,000 or more but less than 13,000 cycles was rated "B", and less than 9,000 cycles was rated "C". In these evaluations, "A" is the best, followed by "B", and "C" is the worst. An evaluation of "A" or "B" for the machining time in Cutting Test 1 and an evaluation of "A" or "B" for the number of cycles in Cutting Test 2 indicate excellent cutting performance. The evaluation results are shown in Table 6.

[0099] [Table 6]

[0100] As shown in Table 6, the processing time and number of processing cycles of the inventive product were both rated "A" or "B," indicating superior wear resistance and fracture resistance. On the other hand, the processing time and number of processing cycles of the comparative product were both rated "C," indicating inferior wear resistance and / or fracture resistance compared to the inventive product. Based on these results, it was found that the invention exhibits superior wear resistance and fracture resistance, resulting in a longer tool life.

[0101] (Example 2: Inventions 30-48) As a substrate, a cermet prepared in the same manner as inventions 1, 2, 5, 6, and 9 of Example 1 above was prepared. After ion bombardment treatment was applied to the surface of the substrate, a coating layer was formed by arc ion plating. The coating layer was formed to have the composition and average thickness described in Table 7. When multiple layers were formed, the first layer, second layer, and third layer were formed on the surface of the cermet in that order. The method for forming the coating layer was as follows.

[0102] The cermets of inventions 1, 2, 5, 6, and 9 were mounted in holders inside the reaction vessel of an arc ion plating apparatus. The pressure inside the reaction vessel was set to 1.0 × 10⁻⁶ -2 A vacuum of less than Pa was created. The cermet was heated to 500°C using a furnace heater. After heating, Ar gas was introduced into the reaction vessel to bring the pressure to 3.0 Pa. After the gas was introduced, a bias voltage of -400V was applied to the substrate, and a current of 40A was passed through the tungsten filament in the reaction vessel to perform ion bombardment treatment with Ar gas on the surface of the substrate for 30 minutes. After the ion bombardment treatment was completed, the pressure inside the reaction vessel was reduced to 5.0 × 10⁻⁶. -3 The system was evacuated until a vacuum of less than Pa was achieved.

[0103] After vacuuming, the cermet temperature was controlled to 450°C, and N2 gas was introduced into the reaction vessel to create a nitrogen atmosphere with a pressure of 3.0 Pa. Then, only during the formation of the second layer of inventions 30, 37, 40, 43, and 46, a mixed gas of N2 gas and acetylene (C2H2) gas in a volume ratio of 90:10 was introduced, and the pressure inside the reaction vessel was increased to 2.7 Pa. Furthermore, only during the formation of the coating layer of inventions 35 and 36, the cermet temperature was controlled to 600°C, and only during the formation of the coating layer of invention 36, the pressure inside the reaction vessel was increased to 5.0 Pa. Subsequently, a bias voltage of -60V was applied to the cermet, and the metal evaporation source was evaporated by a 150A arc discharge, forming a coating layer on the surface of the cermet. However, only during the formation of the coating layer in invention 36, the applied bias voltage was changed to -30V. As the metal evaporation source, one corresponding to the metal component of each layer, as shown in Table 7, was used. After forming the coating layer, the sample was cooled. After the sample temperature fell below 100°C, the sample was removed from the reaction vessel.

[0104] Here, inventions 30-36 are coated surfaces of invention 1, inventions 37-39 are coated surfaces of invention 2, inventions 40-42 are coated surfaces of invention 5, inventions 43-45 are coated surfaces of invention 6, and inventions 46-48 are coated surfaces of invention 9.

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

[0106] Furthermore, using the obtained samples, cutting tests were performed in the same manner as in Example 1, and inventions 30-45 were evaluated. The results are shown in Table 8.

[0107] [Table 7]

[0108] [Table 8]

[0109] The results shown in Table 8 indicate that 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, exhibits superior wear resistance and fracture resistance, and also has a longer tool life. [Industrial applicability]

[0110] The cermets and coated cermets of the present invention have excellent wear resistance and fracture resistance, which extends tool life compared to conventional tools, and therefore have high potential for industrial application.

Claims

1. A cermet comprising a hard phase and a binder phase, The content of the hard phase is 80.0% by volume or more and 94.0% by volume or less. The content of the aforementioned binding phase is 6.0% by volume or more and 20.0% by volume or less. The total content of the hard phase and the binding phase is 100% by volume. 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. In the hard phase, the proportion of Ti (atomic ratio) relative to the total proportion of Ti, W, Mo, Cr, Ta, Nb, V, Hf, and Zr is 0.65 or more and 0.90 or less. The hard phase includes cubic crystals, The bonded phase is a phase containing at least one element selected from the group consisting of Co, Ni, and Fe. The aforementioned hard phase consists of hard particles, The region of the cermet that is more than 100 μm away from the surface inward is defined as the internal region, and within the internal region, when the ratio of the length of a corresponding grain boundary to 100% of the total length of grain boundaries between adjacent hard particles is defined as ratio A, then ratio A is 12% or more and 50% or less. cermet.

2. In the internal region, when the ratio of the length of the Σ3 grain boundary to 100% of the length of the corresponding grain boundary is denoted as ratio X, the ratio X is 20% or more and 50% or less. The cermet according to claim 1.

3. The surface region of the cermet is defined as the region extending 100 μm inward from the surface, and within this surface region, the ratio B is defined as the ratio of the length of a corresponding grain boundary to 100% of the total length of grain boundaries between adjacent hard particles. In this ratio B, the ratio B is between 15% and 55%. The cermet according to claim 1.

4. The ratio of proportion B to proportion A (B / A) is 1.1 or more and 2.0 or less. The cermet according to claim 3.

5. In the aforementioned surface region, when the ratio Y is the ratio of the length of the Σ3 grain boundaries to 100% of the length of the corresponding grain boundary, the ratio Y is 30% or more and 60% or less. The cermet according to claim 3.

6. In the aforementioned internal region, when the ratio of the length of the Σ3 grain boundaries to 100% of the length of the corresponding grain boundary is denoted as ratio X, the ratio of ratio Y to ratio X (Y / X) is 1.2 or more and 2.5 or less. The cermet according to claim 5.

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

8. 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 7.

9. The coating layer is a single layer or a laminate of two or more layers, comprising 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 7.

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