JP2010222650A - cermet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cermet which has excellent chipping resistance, and is suitable for the material of a cutting tool capable of cutting with which the excellent working face quality of the material to be cut is obtained, and to provide a coated cermet tool. <P>SOLUTION: The cermet is obtained in such a manner that a hard phase composed of a compound of the carbonitride of the group 4, 5, 6 metals in the periodic table is bound by a binder phase essentially consisting of an iron group metal. The cermet provided with four kinds of grains with different compositions and forms as a hard phase has excellent chipping resistance and welding resistance while having high wear resistance, and with which satisfactory working face quality can be obtained. The hard phase 1 is constituted of the single phase grains of Ti(C, N); the second hard phase 2 is constituted of cored grains having a core part 2a constituted of Ti(C, N) and a peripheral part 2b covering the whole of the core part 2a; the third hard phase 3 is constituted of a composite carbonitride solid solution including Ti, W, cored grains having the W concentration at a core part 3a higher than that of a peripheral part 3b, and the fourth hard phase 4 is constituted of single phase grains composed of a composite carbonitride solid solution including Ti. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a cermet suitable for a constituent material of a cutting tool, and a coated cermet tool based on this cermet. In particular, the present invention relates to a cermet that provides a cutting tool that is excellent in fracture resistance and capable of performing cutting with excellent quality of the work surface of a work material.

  Conventionally, as a base material for cutting tools, titanium carbide (TiC) or titanium carbonitride (Ti (C, N)) is the main hard phase, and cermet bonded with iron group elements such as cobalt (Co) and nickel (Ni). Is being used. Patent Document 1 discloses a cermet having a hard phase composed of a single-phase particle and a core-structured particle whose core is covered by the periphery. Patent Documents 2 and 3 disclose cermets in which cored particles having a core part and a peripheral part covering the core part are used as a hard phase.

Japanese Patent Laid-Open No. 02-190438 JP 2004-292842 A Japanese Unexamined Patent Publication No. 2006-131975

  Cermet tools based on cermets are generally superior in wear resistance and have a machined surface (finished surface) of the work material compared to tools made of cemented carbide with tungsten carbide (WC) as the main hard phase. Although it is beautiful, it has low toughness and inferior fracture resistance. Therefore, sudden breakage is likely to occur and the tool life is not stable. In recent years, it has been demanded to further improve the quality of the work surface of a work material in cutting and to improve the fracture resistance, which is a weak point of a cermet tool, and to stabilize the tool life.

  In the conventional cermet in which the hard phase is composed of particles having a single-phase structure having no peripheral portion, the wettability with the binder phase is poor and the fracture resistance is poor.

  In conventional cermets in which the hard phase is composed of cored structure particles, cracks tend to propagate through the boundary between the core and the peripheral part, and this cracking leads to a reduction in fracture resistance. In particular, if the core is fine, it is difficult to suppress the progress of cracks, and it is difficult to improve fracture resistance.

  Then, one of the objectives of this invention is providing the cermet suitable for the constituent material of the cutting tool which is excellent in a fracture resistance, and can perform the cutting process excellent in the quality of the processing surface. Another object of the present invention is to provide a coated cermet tool comprising a substrate made of the cermet.

  The present inventors have a high wear resistance when a hard phase exists in a specific range in the cermet and four kinds of particles having different compositions and forms exist as the particles constituting the hard phase. In addition, the inventors have found that remarkable improvement in fracture resistance and welding resistance can be expected. Further, the surface quality of the work material can be improved by improving the welding resistance. Based on the above findings, the present invention defines the content of the hard phase and the four hard phases.

In the cermet of the present invention, the hard phase composed of one or more compounds selected from the group consisting of carbides, nitrides, carbonitrides, and their solid solutions of the Group 4, 5, 6 metals of the Periodic Table contains an iron group metal. It is a cermet bonded by a binder phase as a main component. This cermet contains 70% by mass or more and 97% by mass or less of the hard phase, with the balance being substantially composed of a binder phase. The cermet contains the following first hard phase, second hard phase, third hard phase, and fourth hard phase as the hard phase.
First hard phase: consists of a single phase of titanium carbonitride (Ti (C, N)), or part of the periphery of Ti (C, N) is titanium (Ti), periodic table 4, 5, 6 It is a hard phase covered with a composite carbonitride solid solution with one or more metals selected from group metals (excluding Ti).
Second hard phase: a hard phase having a core structure including a core portion and a peripheral portion covering the entire periphery of the core portion. The core is composed of Ti (C, N), and the peripheral portion is composed of Ti and one or more metals selected from Group 4, 5, 6 metals (excluding Ti) of the periodic table. It is composed of a composite carbonitride solid solution.
Third hard phase: a hard phase having a core structure including a core part and a peripheral part covering the entire periphery of the core part. The said core part and the said peripheral part are comprised from the same element, and are comprised from the composite carbonitride solid solution containing Ti and W at least. Further, the W concentration in the core portion is larger than the W concentration in the peripheral portion.
Fourth hard phase: A hard phase having a single-phase structure composed of a composite carbonitride solid solution of Ti and one or more metals selected from Group 4, 5, 6 metals (excluding Ti) of the periodic table. is there.

  The cermet of the present invention contains a specific amount of a hard phase, and the first hard phase, the second hard phase, the third hard phase, and the fourth hard phase coexist as the hard phase. Each of the functions of the hard phase to the fourth hard phase can be performed. Specifically, the cermet of the present invention has excellent wear resistance due to the presence of a hard phase having a high hardness, and good wetting with the binding phase due to the presence of a hard phase excellent in wettability with the binding phase. The structure can be maintained, and the structure in which the binder phase exists uniformly can be obtained, and improvement of wear resistance and defect resistance can be expected by homogenizing the structure. In addition, the cermet of the present invention can improve thermal conductivity due to the presence of a hard phase having excellent thermal characteristics, and can also be expected to suppress thermal cracking and improve welding resistance. As described above, the cermet of the present invention has excellent wear resistance and can significantly improve the fracture resistance and welding resistance. For this reason, the cutting tool constituted by the cermet of the present invention is less likely to be worn or chipped, so that the tool life can be stabilized and the life can be extended. The quality of the machined surface of the work material can be improved. Hereinafter, the present invention will be described in more detail.

<Cermet>
<Overall composition>
The cermet of the present invention is composed of a hard phase of 70% by mass or more and 97% by mass or less, and the balance is composed of a binder phase and inevitable impurities. Inevitable impurities include oxygen and metal elements in the order of ppm, which are contained in the raw material or mixed in the manufacturing process.

《Hard phase》
[composition]
The hard phase is a compound of at least one metal element selected from Group 4, 5, 6 metals of the periodic table and at least one element of carbon (C) and nitrogen (N), that is, a carbide of the above metal element. , Nitride, carbonitride, and at least one selected from these solid solutions. In particular, the cermet of the present invention is a Ti (C, N) -based cermet containing at least a carbonitride solid solution containing titanium carbonitride (Ti (C, N)) and titanium (Ti). When the content of the hard phase exceeds 97% by mass, the fracture resistance is remarkably reduced because the binder phase is too small, and when it is less than 70% by mass, the hardness is significantly reduced because the binder phase is excessive. Abrasion deteriorates. A more preferable content of the hard phase is 80% by mass or more and 90% by mass or less.

  Further, the hard phase contains four kinds of different compositions and forms, such as the first hard phase, the second hard phase, the third hard phase, and the fourth hard phase. Specifically, it contains a Ti (C, N) -based hard phase and a hard phase having other composition including Ti, a single-phase hard phase, and a hard phase with a core structure. The presence state of the four hard phases can be easily discriminated by the density of micrographs taken with a scanning electron microscope (SEM).

(First hard phase)
The particles constituting the first hard phase are particles having a single phase structure substantially consisting of only Ti (C, N), or a part of the periphery of Ti (C, N) is Ti and a periodic table other than Ti. Particles covered with a composite carbonitride solid solution of one or more metals selected from Group 4,5,6 metals, that is, the periphery of Ti (C, N) is completely covered with the composite carbonitride solid solution. The particles are not. The first hard phase contains a large amount of Ti as compared with the third hard phase and the fourth hard phase, which will be described later, so that the hardness is high and the reactivity with steel that is widely used for work materials is low. Therefore, the presence of the first hard phase in the cermet makes it possible to achieve particularly improved wear resistance and welding resistance.

(Second hard phase)
The particles constituting the second hard phase are substantially composed of Ti (C, N) in the core (Ti (C, N) occupies 95% or more of the entire core by atomic ratio). Particles with a core structure in which the periphery covering the entire periphery is composed of a composite carbonitride solid solution of Ti and at least one kind of metal selected from Group 4, 5, 6 metals of the periodic table other than Ti It is. The specific composition of the peripheral part is, for example, (Ti, W, Mo) (C, N), (Ti, W, Nb) (C, N), (Ti, W, Mo, Nb) (C, N ), (Ti, W, Mo, Nb, Zr) (C, N). Unlike the first hard phase, the second hard phase has a peripheral part that has good wettability with the binder phase over the entire periphery of the core part, reducing the occurrence of nests in the cermet By homogenizing, hardness can be stabilized. Further, the homogenization of the structure can be expected to further improve toughness such as fracture resistance. Therefore, the presence of the second hard phase in the cermet can stabilize the effects of wear resistance and fracture resistance, in particular.

(3rd hard phase)
The particles constituting the third hard phase are core-structured particles in which the core portion and the peripheral portion are composed of the same element, and are composed of a composite carbonitride solid solution containing at least Ti and W. In addition, the W concentration in the core portion of this particle is larger than the W concentration in the peripheral portion. Specific compositions include, for example, (Ti, W) (C, N), (Ti, W, Mo) (C, N), (Ti, W, Nb) (C, N), (Ti, W, Mo, Nb) (C, N) and the like. The third hard phase contains more W than the first hard phase and the second hard phase, and it can be expected to improve thermal conductivity while maintaining high hardness. , Fracture resistance, and plastic deformation resistance can be improved.

(4th hard phase)
The particles constituting the fourth hard phase have a single-phase structure composed of a composite carbonitride solid solution of Ti and at least one metal selected from Group 4, 5, 6 metals of the periodic table other than Ti. Particles. Unlike the third hard phase, this particle does not have a clear boundary between the core part and the peripheral part, and the entire particle has a uniform composition. A typical example of the metal other than Ti constituting the fourth hard phase is W. The specific composition of the fourth hard phase is, for example, (Ti, W) (C, N), (Ti, W, Mo) (C, N), (Ti, W, Nb) (C, N), (Ti, W, Mo, Nb) (C, N). In particular, when the fourth hard phase contains W, there is no significant change in the W concentration as in the third hard phase (the W distribution is not seen), and the entire fourth hard phase is uniform. W exists. For this reason, the presence of the fourth hard phase in the cermet reduces the hardness slightly, but the hardness becomes uniform and crack propagation does not easily occur in the hard phase, and an improvement in thermal conductivity can be expected. Therefore, heat crack resistance and fracture resistance can be improved.

  When the hard phase is substantially composed of only the first hard phase and the second hard phase, it is difficult to improve the fracture resistance. When the hard phase is substantially composed only of the first hard phase and the third hard phase, the wettability with the binder phase is deteriorated, so that nests are likely to be generated and the fracture resistance is poor. Even when the hard phase is substantially composed only of the first hard phase and the fourth hard phase, the wettability with the binder phase is poor, so nests are likely to occur, and sufficient hardness cannot be obtained and fracture resistance is obtained. Is bad.

  When the hard phase is substantially composed only of the second hard phase and the third hard phase, it is difficult to suppress the progress of cracks that pass through the boundary between the core and the peripheral part, which is a conventional problem, The expected fracture resistance cannot be obtained. When the hard phase is substantially composed only of the second hard phase and the fourth hard phase, improvement in fracture resistance cannot be expected.

  When the hard phase is substantially composed of the first hard phase, the second hard phase, and the third hard phase, and does not contain the fourth hard phase, the proportion of the third hard phase containing W is relatively increased. . When a large amount of W is present, it tends to react with the work material (particularly steel) during cutting, and welding tends to occur. Therefore, the work surface of the work material is deteriorated. In other words, in addition to the first hard phase, the second hard phase, and the third hard phase, the presence of the fourth hard phase improves the quality (glossiness) of the work surface of the work material, and this excellent Can maintain stable quality.

  When the hard phase is substantially composed of the first hard phase, the second hard phase, and the fourth hard phase and does not contain the third hard phase, although it can be expected to improve the thermal conductivity, it causes a decrease in hardness and cracks occur. Since it progresses easily, the defect occurrence rate increases. In other words, in addition to the first hard phase, the second hard phase, and the fourth hard phase, the presence of the third hard phase further improves the thermal conductivity, thereby preventing thermal cracks and the progress of these cracks. It is possible to reduce and effectively improve the fracture resistance.

  When the hard phase is substantially composed of the second hard phase, the third hard phase, and the fourth hard phase and does not contain the first hard phase, the wear resistance and welding resistance that can be expected by the presence of the first hard phase. It is difficult to obtain the effect of improvement, and particularly the gloss of the processed surface of the work material is inferior.

  When the hard phase is substantially composed of the first hard phase, the third hard phase, and the fourth hard phase and does not contain the second hard phase, that is, Ti (C, N, which is the main component of the hard phase in the cermet When the hard phase of the) system is only the first hard phase, the wettability with the binder phase becomes extremely poor as described above, and nests are likely to be generated, resulting in deterioration of mechanical properties.

  The cermet of the present invention, in addition to the first hard phase and the second hard phase, in particular, due to the simultaneous presence of the third hard phase and the fourth hard phase, the reaction with the steel while maintaining the thermal strength. It can be suppressed. Therefore, the cutting tool based on the cermet of the present invention can be expected to improve the resistance to thermal plastic deformation, improve the thermal crack resistance, and improve the welding resistance. It is expected that the properties can be improved.

[Particle size]
The hard phase is preferably a mixture of coarse particles and fine particles, particularly fine particles having a particle size of 1 μm or less and coarse particles having a particle size of more than 1 μm and 3 μm or less. Furthermore, it is preferable that a hard phase of 60% or more and 90% or less with respect to the total area of the hard phase is made of the coarse particles, and the remainder of the hard phase is made of the fine particles. The coarse particles are composed of the first hard phase, the second hard phase, the third hard phase, and the fourth hard phase, and the fine particles are substantially composed of the first hard phase and the second hard phase. It is preferable that

  In such a mixed grain structure, the presence of fine particles so as to fill a gap formed between coarse particles can improve hardness and fracture toughness. Since the particle size of the coarse particles is more than 1 μm and the particle size of the fine particles is 1 μm or less, a sufficient gap is provided between the coarse particles, and the fine particles can intervene in the gap. The effect of improving hardness and fracture toughness can be obtained. Further, when the particle size of coarse particles is 3 μm or less, the binder phase existing between the particles does not become excessive, and the decrease in hardness and the deterioration of fracture toughness due to the presence of a large binder phase pool can be reduced. The particle size of the fine particles is particularly preferably 0.1 μm or more and 0.8 μm or less.

  In addition, since the area ratio of the coarse grains is 60% or more, the coarse grains are present appropriately, so that the effect of suppressing the progress of cracks is large, and the toughness is enhanced. Fine particles are sufficiently present in the gaps formed between the fine particles, so that the improvement in hardness and the progress of cracks can be suppressed. Furthermore, since fine particles are present appropriately, the surface roughness of the outermost surface of the cermet can be reduced, and excellent cutting performance can be obtained. A more preferable range of the area ratio of the coarse particles is 70% or more and 85% or less. Further, the total area of the fine particles is 80% or more, preferably 90% or more, and more preferably almost all of them are composed of the first hard phase and the second hard phase. (C, N) is sufficiently present to improve wear resistance. The method for obtaining the particle size, area, and area ratio defined in the present invention will be described later.

  The particle size and area ratio of the hard phase particles can be adjusted, for example, by adjusting the size and amount of the raw material powder and the production conditions (such as grinding time and sintering conditions). When the pulverization time is lengthened, the hard phase particles in the cermet tend to be fine, and when the sintering temperature is high, the hard phase particles in the cermet tend to be coarse. Even if the pulverization time is lengthened and the powder is made fine, if the sintering temperature is increased, the particles may grow and coarse hard phase particles may be present.

  The area ratio of the first hard phase with a particle size of more than 1μm and 3μm or less (coarse) is S1, and the area ratio of the second hard phase with a particle size of more than 1μm and 3μm or less (coarse) with respect to the total area of the hard phase When S is S2, (S1 + S2) preferably satisfies 0.1 or more and 0.5 or less. When (S1 + S2) is 0.1 or more, it is difficult to weld to the work material, and it is possible to reduce the occurrence of minute rashes on the work material surface, and to improve the properties of the work surface of the work material. In addition, the wear resistance of the tool can be improved by reducing the wear due to welding by improving the welding resistance. In addition, when (S1 + S2) is 0.5 or less, a decrease in toughness due to the increase in hardness can be suppressed, and chipping and chipping can hardly occur. A more preferable range of (S1 + S2) is 0.3 or more and 0.5 or less.

  In addition, when the area ratio of the third hard phase having a particle size of more than 1 μm and 3 μm or less (coarse) is S3, and the area ratio of the fourth hard phase having a particle diameter of more than 1 μm and 3 μm or less (coarse) is S4, When S1 / (S1 + S2) is 0.1 or more and 0.4 or less and S3 / (S3 + S4) is 0.4 or more and 0.9 or less, both wear resistance and fracture resistance can be further achieved, and the surface gloss of the work material can be improved. It can be improved. At this time, a more preferable range of S1 / (S1 + S2) is 0.3 or more and 0.4 or less, and a more preferable range of S3 / (S3 + S4) is 0.7 or more and 0.9 or less.

  When the area of the first hard phase with a particle size of 1 μm or less (fine particles) is SS1, and the area of the second hard phase with a particle size of 1 μm or less (fine particles) is SS2, SS1 / (SS1 + SS2) is 0.5 or more and 0.9 The following is preferable. When SS1 / (SS1 + SS2) is 0.5 or more, the minute first hard phase is present more than the second hard phase, so that it is possible to significantly improve the wear resistance. Also, if SS1 / (SS1 + SS2) is 0.9 or less, the proportion of the first hard phase in the fine hard phase does not become excessive, and wetting due to the presence of the fine first hard phase in excess The possibility of causing the deterioration of hardness can be suppressed by the generation of minute nests accompanying the decrease in the wettability and the decrease in the wettability. A more preferable range of SS1 / (SS1 + SS2) is 0.55 or more and 0.7 or less.

  It is preferable that the total area ratio of the area of the third hard phase and the area of the fourth hard phase is larger than 40% with respect to the total area of the cermet (hard phase + binding phase). In this case, since the thermal characteristics are stabilized, the thermal cracking resistance is improved, and thus the fracture resistance can be improved. In particular, the third hard phase and the fourth hard phase are preferably roughly coarse as described above.

<< Binder Phase >>
The binder phase is mainly composed of at least one metal selected from iron group metals such as cobalt (Co), iron (Fe), and nickel (Ni). “Main component” means that the binder phase is substantially composed of only one or more metals selected from the above iron group metals, or one or more selected from the above iron group metals. An alloy in which the constituent elements of the hard phase described above are dissolved in 0.1% by mass to 20% by mass with respect to the total mass of the binder phase, that is, 80% by mass or more of the binder phase is composed of iron group metal. Suppose. When the binder phase is a solid solution of the constituent elements of the hard phase, the toughness can be improved and the fracture resistance tends to be increased by solid solution strengthening. In addition, since at least one of Co and Ni is a main component (80 mass% or more of the total mass of the binder phase), the binder phase has high wettability with the hard phase and excellent corrosion resistance. It becomes a preferable cermet by a constituent material.

  In the case where the binder phase contains both Ni and Co, particularly when the mass ratio of Ni and Co in the binder phase (the ratio of the mass of Ni to the mass of Co) is Ni / Co, Ni / Co is It is preferably 0.7 or more and 1.5 or less. When Ni / Co satisfies 0.7 or more and 1.5 or less, a decrease in wettability can be reduced and high toughness can be maintained, and a decrease in hardness can be reduced and high strength can be maintained. Particularly preferable Ni / Co is 0.8 or more and 1.2 or less. Ni / Co can be adjusted, for example, by adjusting the amount of Co powder or Ni powder added to the raw material.

[Other elements]
The cermet of the present invention may contain molybdenum (Mo). When Mo is contained, the second hard phase tends to be formed particularly easily. Therefore, since the wettability between the hard phase and the binder phase can be improved, the binder phase can sufficiently exist around the particles constituting the hard phase, and the toughness can be improved. The Mo content is preferably 0.01% by mass or more and 2.0% by mass or less. When the Mo content is 0.01% by mass or more, as described above, the cermet as a whole can improve the wettability and improve the hardness and toughness. By setting the content to 2.0% by mass or less, the first hard phase is formed. It can be suppressed that the second hard phase and the third hard phase are relatively increased. Therefore, it is possible to obtain the expected fracture resistance by suppressing the progress of cracks passing through the boundary between the core portion and the peripheral portion of the hard phase, which is a conventional problem. A more preferable content of Mo is 0.5% by mass or more and 1.5% by mass or less. It may not contain Mo.

<Cermet tool>
"Base material"
The cermet of the present invention having the above-described configuration is excellent not only in wear resistance but also in chipping resistance and welding resistance by providing the four hard phases as described above, and a good finished surface is desired. It can be suitably used as a base material for a cutting tool (cermet tool).

《Hard film》
The base material may include a hard film coated on at least a part of its surface. The hard film is preferably provided at least at the blade edge and in the vicinity thereof, and may be provided over the entire surface of the substrate. The hard film may be a single layer or multiple layers, and the total thickness is preferably 1 to 20 μm. As a method for forming the hard film, either a chemical vapor deposition method such as a thermal CVD method (CVD method) or a physical vapor deposition method such as an arc ion plating method (PVD method) can be used.

The composition of the hard film is one or more elements selected from the group consisting of metals of Groups 4, 5, 6 of the periodic table, aluminum (Al), and silicon (Si), carbon (C), nitrogen (N ), Oxygen (O) and boron (B) selected from the group consisting of one or more elements, that is, carbides, nitrides, oxides, borides, and solid solutions of elements such as the above metals 1 or more selected from the group consisting of a compound consisting of: cubic boron nitride (cBN), diamond, and diamond-like carbon (DLC). Specific film quality includes Ti (C, N), Al ₂ O ₃ , (Ti, Al) N, TiN, TiC, (Al, Cr) N and the like.

<Method for producing cermet>
The cermet is generally produced by a process of raw material preparation → grinding and mixing of raw materials → molding → sintering. The cermet of the present invention can be produced by using the raw material powder described later and adjusting the grinding and mixing time and sintering conditions.

<Preparation of raw materials>
The raw material includes a compound powder comprising a compound of at least one metal selected from Group 4, 5, 6 metals of the periodic table and at least one element of carbon (C) and nitrogen (N), and a binder phase. Is used, typically an iron group metal powder. By using a fine powder and a relatively coarse powder as these powders, it is easy to obtain a cermet having a hard phase in which the coarse particles and the fine particles are mixed. The size of the powder may be appropriately selected in consideration of the size of the hard phase particles.

In order to generate the first hard phase and the second hard phase, for example, Ti (C, N) powder is used. Some Ti (C, N) powders are conventionally produced using sponge Ti as a starting material.In particular, when Ti (C, N) powder produced using TiO ₂ as a starting material is used, fine particles 1 It tends to form a hard phase. Moreover, when the compound powder containing Mo is used together as described above, the second hard phase tends to be easily formed. In order to produce the third hard phase, a powder containing W, for example, a WC powder is used. In order to produce the fourth hard phase, a compound powder containing Ti and Group 4, 5, 6 metals excluding Ti, for example, (Ti, W) (C, N) powder is used. By using such a compound powder, particles of the fourth hard phase, that is, particles having a single phase structure in which Ti and Group 4, 5, and 6 metals excluding Ti are uniformly dissolved are obtained. easy.

<Crushing and mixing>
When the pulverization time is lengthened, the powder can be made fine, and fine hard phase particles tend to be easily generated in the cermet. However, if the pulverization time is too long, re-aggregation may occur, or it may become too fine to form a core compound. A preferable grinding and mixing time is 12 hours or more and 36 hours or less.

<Sintering>
If the sintering temperature is too high, the particles constituting the hard phase may grow, making it easy for many coarse particles to be present in the cermet, and in particular, making it difficult to form the fourth hard phase particles. is there. Therefore, the sintering temperature is preferably 1400 ° C. or higher and 1600 ° C. or lower. Further, in the sintering step, when cooling the heated compact while maintaining the sintering temperature for a predetermined time, it is preferable to cool in a vacuum or an inert gas atmosphere such as argon (Ar). In the case of an inert gas atmosphere, a relatively low pressure of 665 Pa or more and 6650 Pa or less is particularly preferable. Further, when the cooling rate is increased, specifically, 10 ° C./min or more, the fourth hard phase tends to be easily generated.

  The coated cermet tool of the present invention is excellent in wear resistance and fracture resistance, and in addition, can perform cutting with excellent quality of the work surface of the work material. The cermet of the present invention can be suitably used as a constituent material for such a tool.

FIG. 1 is an explanatory view schematically showing four types of hard phases present in the cermet of the present invention.

<Test example>
A cutting tool made of cermet was prepared, and the composition, structure, and cutting performance of the cutting tool were examined.

The cutting tool was produced as follows. First, the following were prepared as raw material powder.
(1) Ti (C, N) powder having an average particle size of 0.7 μm This Ti (C, N) powder is a powder produced using TiO ₂ as a starting material and has a C / N ratio of 1/1.
(2) Ti (C, N) powder with an average particle size of 0.8 μm and Ti (C, N) powder with an average particle size of 3.0 μm These Ti (C, N) powders all use sponge Ti as a starting material. The produced powder has a C / N ratio of 1/1. In Table 1, these Ti (C, N) powders are described as “s-TiCN”.
(3) (Ti, W) (C, N) powder with an average particle size of 2.8 μm This (Ti, W) (C, N) powder is a powder obtained by previously dissolving W in Ti (C, N) powder. And the C / N ratio is 1/1.
(4) WC powder, NbC powder, TaC powder, Mo ₂ C powder, Ni powder, Co powder having an average particle size of 0.5 to 3.0 μm These powders are all commercially available powders.
The prepared raw material powders were weighed and blended so as to have the blending ratio (mass%) shown in Table 1, and powder Nos. 1 to 12 were prepared.

  Each prepared powder was charged into a stainless steel pot together with an acetone solvent and a cemented carbide ball, and pulverized and mixed (wet). Table 2 shows the raw material powder No. used for the preparation of each sample and the pulverization / mixing time (hours). A small amount of paraffin was added to the mixed powder obtained by pulverization and mixing and then dried, and then press molded at a pressure of 98 MPa using a mold to produce a CNMG120408 shaped compact.

  Each molded body obtained was heated to 450 ° C. to remove paraffin, then heated from room temperature to 1250 ° C. in a vacuum, and then sintered (including the cooling step) under the conditions shown in Table 3. A sintered body was obtained.

  An arbitrary cross section was taken for each of the obtained sintered bodies, and the cross section was observed with a scanning electron microscope (SEM) magnified 5000 times. As a result, in the observation field of each sintered body, black particles, particles in which a part of the periphery of the black particles is covered with a gray region (hereinafter, these two particles are combined into a black single particle). ), Particles that are entirely covered with a gray area around the black particles (hereinafter referred to as black core double particles), and those around the white particles are covered with a gray area. At least one kind of particles (hereinafter referred to as white core double particles) and gray particles (hereinafter referred to as gray particles) was confirmed. In the sintered bodies of sample Nos. 1 to 19, as shown in FIG. 1, black single particles (first hard phase 1), black core double particles (second hard phase 2), white core double particles (third Four types of particles, hard phase 3) and gray particles (fourth hard phase 4), were observed. The first hard phase 1 is composed of only black particles, and the one part of the black particles is covered with a gray region (peripheral part 1b), the second hard phase 2 is the core part 2a Is black, the peripheral part 2b is gray, and the third hard phase 3 appears that the core part 3a is white and the peripheral part 3b is gray. There is a binder phase 10 between the particles. On the other hand, in the sintered bodies of sample Nos. 100 to 105, at least one of black single particles, black core double particles, white core double particles, and gray particles was not observed.

  When the composition of each particle was examined by TEM-EDX analysis, the black single particle was Ti (C, N), the core part of the black core double particle was Ti (C, N), and the peripheral part covering the core part was Composite carbonitride solid solution containing Ti and one or more metals of W, Nb, Ta and Mo, white core double particle is a composite containing Ti and W and one or more metals of Nb, Ta and Mo Carbonitride solid solution having a core W concentration higher than that surrounding the core, gray particles are composite carbon containing Ti, W and one or more metals of Nb, Ta, and Mo It was composed of a nitride solid solution. The gray particles did not show a clear boundary between the core and the peripheral part. The component analysis of the hard phase can be performed using EPMA, fluorescent X-ray, ICP-AES, etc. in addition to TEM-EDX analysis.

  A bonded phase was present between the particles, and as a result of investigation by TEM-EDX analysis, the bonded phase was substantially composed of Co and Ni. In some samples, constituent elements of the hard phase were dissolved in the binder phase by about several mass%. Also, as a result of analysis, the Co content in the sintered body is almost the same as the additive amount of the raw material Co powder, and the Ni content in the sintered body is compared with the additive amount of the raw material Ni powder. And tended to decrease by about 0.2 to 0.3%. From this, it can be said that the content of the hard phase in each sample (sintered body) is almost equal to the amount (about 86 mass%) excluding the added amount of Co powder and Ni powder used as raw materials. Furthermore, the mass ratio Ni / Co of Ni and Co present in the binder phase was determined. The results are shown in Table 2. Further, the Mo content (% by mass) of each sample (sintered body) was examined by ICP analysis. The results are also shown in Table 2.

  Using the SEM cross-sectional observation image (5000 times), the particle size was determined for all particles present in the observation field of each sample (sintered body). The particle diameter was defined as the Martin diameter (the length of a line segment that bisects the projected area of the particle when the particle is projected onto a plane from a certain direction). Specifically, a micrograph obtained by observing a cross section of the sintered body was used, and the length of a line segment that bisects the area of the particles present in the micrograph was defined as the particle size. The particle diameter of the cored structure particles was determined in a state including the peripheral portion. As a result, in each sample, particles having a particle size of more than 3 μm were hardly observed, and the hard phase was composed of particles having a particle size of substantially 3 μm or less.

  The area of each particle was determined using the particle diameter (the above-mentioned Martin diameter) obtained for the cross-sectional observation image (5000 times). In addition, for each of the first hard phase, the second hard phase, the third hard phase, and the fourth hard phase, the total area of the particles having a particle size of more than 1 μm and 3 μm or less (hereinafter, these total areas are respectively rough. (Referred to as grain area (1), coarse grain area (2), coarse grain area (3), coarse grain area (4)), the total area of grains having a grain size of 1 μm or less for the first hard phase (hereinafter referred to as this The total area was referred to as the fine particle area (1)), and the total area of the particles having a particle diameter of 1 μm or less for the second hard phase (hereinafter, this total area is referred to as the fine particle area (2)). The total of the coarse phase area (1), coarse grain area (2), coarse grain area (3), coarse grain area (4), fine grain area (1), and fine grain area (2) is the total area of the hard phase, Table 4 shows the total ratio of the coarse grain areas (1) to (4) with respect to the total area of the hard phase, that is, the coarse grain area ratio “coarse grains / total hard phase” (%). Also, the coarse area (1), coarse area (2), coarse area (3), coarse area (4), fine area (1), and fine area (2) with respect to the total area of the hard phase Table 4 shows the area ratio (%). The area ratio of the coarse grain area (1) to the total area of the hard phase is S1, the area ratio of the coarse grain area (2) is S2, the area ratio of the coarse grain area (3) is S3, and the coarse grain area (4) area. The rate was S4, and (S1 + S2), S1 / (S1 + S2), and S3 / (S3 + S4) at this time were determined. The results are shown in Table 4. Furthermore, when the fine particle area (1) is SS1 and the fine particle area (2) is SS2, it corresponds to the area of SS1 / (SS1 + SS2) and the entire cermet (hard phase + binder phase) (here, the field of view of the observed image) The area ratio of the total area of the area of the third hard phase and the area of the fourth hard phase: (third + fourth) / (whole cermet) was obtained. The results are also shown in Table 4. Note that in any of the samples in which the third hard phase and the fourth hard phase existed, the particle diameters of the particles of the third hard phase and the particles of the fourth hard phase are generally more than 1 μm and the particle diameter is 1 μm or less. 3 hard phase particles and 4th hard phase particles were hardly observed.

  The surface of each of the obtained sintered bodies was subjected to planar polishing treatment and blade edge treatment, respectively, to produce a cutting tip (cutting tool) with a breaker having a shape of CNMG120408. Each of the obtained cutting tips was subjected to a cutting test (all turned) under the conditions shown in Table 5 below, and the wear resistance, fracture resistance, and surface roughness of the processed surface were examined. The results are shown in Table 6. The surface roughness Ra was measured according to JIS B 0601 (2001).

  As shown in Table 6, sample Nos. 1 to 19 in which all of the first hard phase, the second hard phase, the third hard phase, and the fourth hard phase exist, any one of the above four types exists. It can be seen that it is excellent in wear resistance as well as in chipping resistance as compared with sample Nos. Moreover, it can be seen that these sample Nos. 1 to 19 have a small surface roughness Ra of the processed surface of the work material and a high surface quality of the processed surface.

  Among sample Nos. 1 to 19, especially when the area ratio of coarse particles satisfies 60% or more and 90% or less, it tends to be more excellent in wear resistance and fracture resistance due to improved hardness and fracture toughness. I understand that there is. Samples Nos. 1 to 19 that satisfy (S1 + S2) in the range of 0.1 to 0.5, or samples that satisfy S1 / (S1 + S2) in the range of 0.1 to 0.4 and S3 / (S3 + S4) in the range of 0.4 to 0.9. It can be seen that the surface roughness Ra tends to be further reduced and the surface quality is excellent. It can be seen that among samples Nos. 1 to 19, in particular, samples satisfying SS1 / (SS1 + SS2) of 0.5 or more and 0.9 or less tend to be more excellent in wear resistance. Moreover, it turns out that the sample whose (3 + 4) / (whole cermet) exceeds 40% among samples No. 1-19 is excellent in toughness.

  A coated tip with a (Ti, Al) N film (thickness 4 μm) formed by arc ion plating on the surface of the cutting tip of sample Nos. 1 to 19 and wear resistance under the test conditions shown in Table 5 A test was conducted. As a result, all the samples were more excellent in wear resistance than the case where there was no hard film.

  The above-described embodiment can be appropriately changed without departing from the gist of the present invention, and is not limited to the above-described configuration. For example, the composition and average particle diameter of the raw material powder, the presence state of each particle of the hard phase, and the composition and thickness of the hard film can be appropriately changed.

  The cermet of the present invention can be suitably used as a cutting tool material. The coated cermet tool of the present invention can be suitably used for turning, milling, particularly steel cutting.

1 1st hard phase 1b peripheral part 2 2nd hard phase 2a, 3a core part 2b, 3b peripheral part
3 3rd hard phase 4 4th hard phase 10 bonded phase

Claims (9)

A hard phase composed of one or more compounds selected from the group consisting of carbides, nitrides, carbonitrides and solid solutions of Group 4, 5, 6 metals of the periodic table, and a bonded phase whose main component is an iron group metal A cermet combined by
The hard phase is contained in an amount of 70% by mass or more and 97% by mass or less, and the balance substantially consists of a binder phase.
The cermet characterized in that the hard phase contains the following first hard phase, second hard phase, third hard phase, and fourth hard phase.
1st hard phase: consists of only a single phase of titanium carbonitride, or a part around the titanium carbonitride is selected from titanium and metals in groups 4, 5, and 6 of the periodic table (excluding titanium) Hard phase with a single-phase structure covered with a composite carbonitride solid solution with more than one kind of metal.Second hard phase: Core structure with a core part and a peripheral part covering the entire periphery of the core part. It is a hard phase, the core part is composed of titanium carbonitride, and the peripheral part is one or more metals selected from titanium and Group 4, 5, 6 metals (excluding titanium) of the periodic table A hard phase composed of a composite carbonitride solid solution with a third hard phase: a hard phase having a core structure including a core portion and a peripheral portion covering the entire periphery of the core portion, the core portion And the peripheral portion is composed of the same element, and is composed of a composite carbonitride solid solution containing at least titanium and tungsten, Hard phase in which the tungsten concentration in the part is larger than the tungsten concentration in the peripheral part. Fourth hard phase: one or more metals selected from titanium and Group 4, 5, 6 metals (excluding titanium) in the periodic table Hard phase with single-phase structure consisting of composite carbonitride solid solution The hard phase of 60% or more and 90% or less with respect to the total area of the hard phase is composed of coarse particles having a particle size of more than 1 μm and 3 μm or less, and the remaining hard phase is composed of fine particles having a particle size of 1.0 μm or less,
The coarse particles are composed of the first hard phase, the second hard phase, the third hard phase, and the fourth hard phase,
2. The cermet according to claim 1, wherein the fine particles are substantially composed of the first hard phase and the second hard phase.   When the area ratio of the first hard phase of the coarse grains is S1 and the area ratio of the second hard phase of the coarse grains is S2 with respect to the total area of the hard phases, (S1 + S2) is 0.1 or more and 0.5 or less. The cermet according to claim 2, wherein the cermet is present.   The area ratio of the first hard phase of the coarse grain is S1, the area ratio of the second hard phase of the coarse grain is S2, and the area ratio of the third hard phase of the coarse grain is the total area of the hard phase. S1 / (S1 + S2) is 0.1 or more and 0.4 or less, and S3 / (S3 + S4) is 0.4 or more and 0.9 or less, when S3 and the area ratio of the fourth hard phase of the coarse particles are S4 The cermet according to claim 2 or 3.   When the area of the first hard phase having a particle size of 1.0 μm or less is SS1, and the area of the second hard phase having a particle size of 1.0 μm or less is SS2, SS1 / (SS1 + SS2) is 0.5 or more and 0.9. The cermet according to any one of claims 2 to 4, wherein the cermet is as follows.   The total area ratio of the area of the third hard phase and the area of the fourth hard phase with respect to the total area of the cermet is more than 40%, according to any one of claims 1 to 5, The stated cermet. The cermet contains nickel (Ni) and cobalt (Co) in the binder phase,
The cermet according to any one of claims 1 to 6, wherein Ni / Co is 0.7 or more and 1.5 or less when the mass ratio of Ni and Co in the binder phase is Ni / Co. .   The cermet according to any one of claims 1 to 7, wherein the cermet contains 0.01 mass% or more and 2.0 mass% or less of molybdenum.   A coated cermet tool comprising: a base material comprising the cermet according to any one of claims 1 to 8; and a hard film coated on at least a part of the surface of the base material.

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