KR101253853B1 - Cermet - Google Patents

Abstract

Provided are a cermet and a coated cermet tool suitable for the material of a cutting tool which are excellent in fracture resistance and capable of cutting with excellent quality of the workpiece surface. It is a cermet in which the hard phase which consists of compounds, such as carbonitrides of a periodic table 4, 5, and 6 metals, is couple | bonded by the bonding phase which has an iron group metal as a main component. By providing four kinds of particles having different compositions and shapes as the hard phase, this cermet has high wear resistance, is excellent in defect resistance and welding resistance, and a good processing surface quality is obtained. The 1st hard phase 1 is a single phase particle of Ti (C, N), the 2nd hard phase 2 is the core part 2a which consists of Ti (C, N), The core particles having the periphery 2b covering the entire core 2a and the third hard phase 3 are composed of a composite carbonitride solid solution containing Ti and W, and the W concentration of the core 3a is determined by the periphery ( The core particles higher than 3b) and the fourth hard phase 4 are single phase particles composed of a composite carbonitride solid solution containing Ti.

Description

Cermet {CERMET}

The present invention relates to a cermet suitable for the constituent material of the cutting tool, and a coated cermet tool based on the cermet. In particular, it is related with the cermet from which the cutting tool which is excellent in defect resistance and excellent in the quality of the processing surface of a workpiece is possible.

Conventionally, as a base material of a cutting tool, titanium carbide (TiC) or titanium carbonitride (Ti (C, N)) is used as the main hard phase, and iron group elements such as cobalt (Co) and nickel (Ni). Combined cermet is used. Patent Document 1 discloses a cermet in which particles having a single phase structure and particles having a core-rim structure covered with a core portion are surrounded by a peripheral portion. In patent documents 2 and 3, the cermet which makes a particle | grain of the core structure which has a core part and the periphery part which covers a core part as a hard phase is disclosed.

[Patent Literature]

Patent Document 1: Japanese Patent Application Laid-Open No. 02-190438

Patent Document 2: Japanese Patent Application Laid-Open No. 2004-292842

Patent Document 3: Japanese Patent Laid-Open No. 2006-131975

Cermet tools based on cermets generally have excellent abrasion resistance and have a beautiful surface (finished surface) in comparison with a tool made of a cemented carbide containing tungsten carbide (WC) as the main hard phase. Toughness is low and defect resistance is inferior. For this reason, sudden defects tend to occur and the tool life is not stable. In recent years, in cutting, it is required to further improve the quality of the workpiece surface of the workpiece, to improve the fracture resistance, which is a weak point of the cermet tool, and to stabilize the tool life.

In a conventional cermet in which the hard phase is composed of particles of a single phase structure having no periphery, the wettability with the bonded phase is poor and the fracture resistance is inferior.

In the conventional cermet, in which the hard phase is composed of particles having a core structure, cracks tend to propagate past the boundary between the core portion and the peripheral portion, and this cracking causes a decrease in fracture resistance. Particularly, when the core portion is fine, it is difficult to suppress the progress of cracking and it is difficult to improve the 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 defect resistance and excellent in the quality of a process surface. Moreover, another object of this invention is to provide the covering cermet tool provided with the base material which consists of said cermet.

MEANS TO SOLVE THE PROBLEM The present inventors have high abrasion resistance, when a hard phase exists in a specific range in a cermet, and when four types of particle | grains which differ in a composition and a form exist as particle | grains which comprise this hard phase, It has been found that significant improvement can be expected. Moreover, the surface quality of a workpiece can also be improved by improving weldability and the like. This invention defines content of a hard phase and four types of hard phases based on the said knowledge.

Cermet of the present invention is a hard phase comprising at least one compound selected from the group consisting of carbides, nitrides, carbonitrides and solid solutions thereof of the Periodic Tables 4, 5, and 6 metals by a binding phase composed mainly of iron group metals. It is a cermet that is combined. This cermet contains 70 mass% or more and 97 mass% or less of the said hard phase, and the remainder contains a coupling phase substantially. Moreover, this cermet contains the following 1st hard phase, 2nd hard phase, 3rd hard phase, and 4th hard phase as said hard phase.

1st hard phase: It contains only the single phase of titanium carbonitride (Ti (C, N)), or the part around Ti (C, N) is titanium (Ti), and periodic table 4, 5, 6 It is a hard phase covered with a complex carbonitride solid solution with at least one metal selected from the group metals (except Ti).

2nd hard phase: It is a hard phase of a core structure which has a core part and the peripheral part which covers the whole periphery of this core part. The core part is made of Ti (C, N), and the peripheral part is made of a complex carbonitride solid solution of Ti and at least one metal selected from the group 4, 5, and 6 metals (except Ti) of the periodic table. It is.

3rd hard phase: It is a hard phase of a core structure which has a core part and the peripheral part which covers the whole periphery of this 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 at least Ti and W. As shown in FIG. Further, the W concentration of the core portion is greater than the W concentration of the peripheral portion.

4th hard phase: It is a hard phase of single phase structure containing the composite carbonitride solid solution of Ti and 1 or more types of metals chosen from the periodic table group 4, 5, 6 metals except Ti.

The cermet of the present invention contains a specific amount of a hard phase, and the hard phase includes the first hard phase, the second hard phase, the third hard phase, and the fourth hard phase. Each of the fourth hard phases may have a function to perform. Specifically, the cermet of the present invention is excellent in wear resistance due to the presence of a hard phase having a high hardness, and has a hard phase having excellent wettability with the binding phase, thereby maintaining good wettability with the binding phase or uniformly present the binding phase. It can be set as the structure to be made, and the improvement of abrasion resistance and defect resistance by expectation of this structure can be expected. 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 to improve welding resistance. Thus, the cermet of the present invention has excellent wear resistance, and can significantly improve defect resistance and welding resistance. Therefore, since the cutting tool comprised by the cermet of this invention hardly produces abrasion and a defect, it can aim at stabilization and extension of tool life, and welding hardly arises, and it is easy to produce a beautiful process surface. It can obtain and the improvement of the quality of the process surface of a workpiece can be expected. Hereinafter, the present invention will be described in more detail.

<Cermet>

<< whole composition >>

In the cermet of the present invention, the hard phase of 70 mass% or more and 97 mass% or less, and the remaining part are composed of a bonding phase and unavoidable impurities. Unavoidable impurities include oxygen or a metal element on the order of ppm contained in the raw material or mixed in the manufacturing process.

<< hard phase >>

[Furtherance]

The hard phase is a compound of at least one metal element selected from Group 4, 5, 6 metals of the periodic table with at least one element of carbon (C) and nitrogen (N), that is, carbides, nitrides, At least one selected from carbonitrides and solid solutions thereof. In particular, the cermet of the present invention is a Ti (C, N) group 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 lowered because the binding phase is too small. When the content of the hard phase is less than 70% by mass, the hardness is remarkably lowered because the binding phase is too large, and wear resistance is deteriorated. More preferable content of a hard phase is 80 mass% or more and 90 mass% or less.

In addition, the hard phase contains four kinds of compositions and shapes different from the above-mentioned first hard phase, second hard phase, third hard phase, and fourth hard phase. Specifically, the hard phase of the Ti (C, N) system and the other composition containing Ti, the hard phase of the single phase structure, and the hard phase of the core structure are contained. The presence state of the 4 types of hard phases can be easily distinguished by the light and shade of the micrograph by a scanning electron microscope (SEM).

(First hard phase)

Particles constituting the first hard phase are particles having a single phase structure consisting substantially of Ti (C, N), or a part of the periphery of Ti (C, N) is Ti and Groups 4, 5, and 6 of the periodic table other than Ti Particles covered with a composite carbonitride solid solution of at least one metal selected from metals, ie, particles around Ti (C, N) are particles not completely covered by the composite carbonitride solid solution. The first hard phase contains more Ti than the third hard phase and the fourth hard phase described later, so that the hardness is high and the reactivity with steel commonly used for the workpiece is low. Therefore, the presence of the first hard phase in the cermet can, in particular, improve the wear resistance and the weldability.

(Second hard phase)

Particles constituting the second hard phase are composed of a core substantially composed of Ti (C, N) (at least 95% of the entire core in atomic ratio occupies Ti (C, N)) and covering the entirety around the core. The peripheral portion is a particle of a core structure composed of a composite carbonitride solid solution of Ti and at least one metal selected from periodic table 4, 5, and 6 metals other than Ti. Specific compositions of the periphery are, 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) etc. are mentioned. Unlike the first hard phase, since the second hard phase has a periphery having a good wettability with the binding phase throughout the periphery of the core, it is possible to reduce the occurrence of pores in the cermet and to homogenize the tissue. As a result, the hardness can be stabilized. In addition, the homogenization of the tissue can be expected to further improve toughness such as fracture resistance. Therefore, the presence of the second hard phase in the cermet makes it possible to stabilize the effects of wear resistance and defect resistance, in particular.

(Third hard phase)

The particles constituting the third hard phase are particles having a core structure composed of the same element in the core and the peripheral portion, and are composed of a complex carbonitride solid solution containing at least Ti and W. Moreover, this particle | grain has W density | concentration of core part larger than W density | concentration of peripheral part. Specific compositions are, for example, (Ti, W) (C, N), (Ti, W, Mo) (C, N), (Ti, W, Nb) (C, N), (Ti, W, Mo, Nb) (C, N) etc. are mentioned. The third hard phase contains more W than the first hard phase and the second hard phase, so that the thermal conductivity can be improved while maintaining high hardness. Therefore, thermal strength, thermal crack resistance, defect resistance and plastic deformation resistance can be improved.

(Fourth hard phase)

Particles constituting the fourth hard phase are particles having a single-phase structure composed of a composite carbonitride solid solution of Ti and at least one metal selected from periodic table 4, 5, and 6 metals other than Ti. Unlike the third hard phase, these particles do not have a clear boundary between the core and the periphery and have the same composition as the whole particle. Examples of metals other than Ti constituting the fourth hard phase include W.

Specific compositions of the fourth hard phase include, for example, (Ti, W) (C, N), (Ti, W, Mo) (C, N), (Ti, W, Nb) (C, N), (Ti, W, Mo, Nb) (C, N) is mentioned. In particular, in the case where the fourth hard phase contains W, no significant change in W concentration is observed (the distribution of W is not seen) as in the third hard phase, and W is uniformly distributed throughout the fourth hard phase. exist. Therefore, when a 4th hard phase exists in a cermet, although hardness falls slightly, hardness becomes the same and it becomes difficult to produce crack propagation in a hard phase. In addition, since the improvement of thermal conductivity can be expected, thermal crack resistance and defect resistance can be improved.

When the hard phase consists essentially 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 of only the first hard phase and the third hard phase, the wettability with the bonded phase deteriorates, so that pores tend to occur and the defect resistance is poor. Even when the hard phase is substantially composed of only the first hard phase and the fourth hard phase, pores tend to occur because of poor wettability with the bonding phase, and sufficient hardness is not obtained, resulting in poor defect resistance.

In the case where the hard phase is substantially composed of only the second hard phase and the third hard phase, it is difficult to suppress the progress of the crack passing through the boundary between the core and the periphery, which is a conventional problem, and thus, the expected defect resistance is not obtained. When the hard phase is substantially composed of only the second hard phase and the fourth hard phase, improvement in defect resistance cannot be expected.

If the hard phase consists substantially of the first hard phase and 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 increases relatively. When much W exists, it will react with a workpiece (especially steel) easily during cutting, and welding will occur easily. This causes deterioration of the processed surface of the workpiece. That is, in addition to the first hard phase, the second hard phase, and the third hard phase, the presence of the fourth hard phase allows the quality (gloss) of the processed surface of the workpiece to be excellent, and this excellent quality can be stably maintained. have.

When the hard phase is substantially composed of the first hard phase and the second hard phase and the fourth hard phase, and does not contain the third hard phase, an improvement in thermal conductivity can be expected, but it causes a decrease in hardness and causes cracks to develop. Since it becomes easy, the incidence of defects increases. That is, 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, reduces thermal cracking and the development of the crack, and effectively prevents the fracture. Can be improved.

When the hard phase is substantially composed of the second hard phase and the third hard phase and the fourth hard phase, and does not contain the first hard phase, the effect of improving the wear resistance and weldability that can be expected by the presence of the first hard phase is It is difficult to obtain, and in particular, the glossiness of the processed surface of the workpiece is inferior.

When the hard phase is substantially composed of the first hard phase and the third hard phase and the fourth hard phase and does not contain the second hard phase, that is, the hard phase of the Ti (C, N) system, which is the main component of the hard phase in the cermet, In the case of only the first hard phase, as described above, the wettability with the bonded phase is extremely bad, and pores are likely to occur, resulting in deterioration of mechanical properties.

In addition to the first hard phase and the second hard phase, the cermet of the present invention, in particular, simultaneously exists with the third hard phase and the fourth hard phase, thereby making it possible to suppress the reaction with steel while maintaining the thermal strength. Therefore, since the cutting tool based on the cermet of the present invention can be expected to improve the resistance to thermal plastic deformation, the improvement of the thermal crack resistance, and the improvement of the weldability, the properties of the processed surface of the workpiece are Is expected to improve.

[Particle diameter]

The hard phase is preferably a mixture of coarse particles and fine particles, particularly fine particles having a particle diameter of 1 m or less, and granulated particles having a particle diameter of more than 1 m and 3 m or less. In addition, it is preferable that the hard phase of 60% or more and 90% or less of the hard phase include the granulation, and the remainder of the hard phase contains the fine particles with respect to the total area of the hard phase. In addition, the granulation is 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.

In such a mixed structure, fine particles exist so as to fill gaps formed between coarse particles, whereby hardness and fracture toughness can be improved. Since the particle diameter of coarse particle | grains exceeds 1 micrometer and the particle diameter of fine particle | grains is 1 micrometer or less, sufficient clearance gap can be formed between coarse particle | grains, and fine particle may interpose in this clearance gap, The effect of improving the hardness and improving the fracture toughness is obtained. Moreover, when the particle diameter of coarse particle | grains is 3 micrometers or less, the binding phase which exists between particle | grains does not become excess, and the fall of hardness and deterioration of fracture toughness by the presence of a large pool of binding phases can be reduced. Can be. The particle diameter of the fine particles is particularly preferably 0.1 µm or more and 0.8 µm or less.

Moreover, since the granulation exists suitably when the area ratio of the said granulation is 60% or more, the effect which suppresses the progress of a crack is large, and toughness can be improved. In addition, when the area ratio of the granulation is 90% or less, fine particles are sufficiently present in the gaps formed between the coarse particles, thereby improving the hardness and suppressing the progress of cracking. In addition, when the fine particles are appropriately present, the surface roughness of the outermost surface of the cermet can be reduced, and excellent cutting performance is obtained. The range with the more preferable area ratio of the said granulation is 70% or more and 85% or less. In addition, with respect to the total area of the fine particles, 80% or more, preferably 90% or more, and more preferably almost all are composed of the first hard phase and the second hard phase, whereby high hardness and fine Ti (C, N) It exists sufficiently and can improve abrasion resistance. The method of obtaining the particle diameter, area, and area ratio prescribed | regulated by this invention is mentioned later.

Adjustment of the particle diameter and area ratio of hard particle | grains can be performed by adjusting the magnitude | size of the raw material powder, the addition amount, and manufacturing conditions (grinding time, sintering conditions, etc.). When the grinding time is lengthened, the hard particles in the cermet tend to be fine, and when the sintering temperature is high, the hard particles in the cermet tend to be coarse. In addition, even when the powder is made fine by lengthening the grinding time, when the sintering temperature is increased, the particles may grow and coarse hard particles may be present.

Regarding the total area of the hard phase, the area ratio of the first hard phase having a particle diameter of more than 1 μm and 3 μm or less (assembly) is S1, and the area of the second hard phase having a particle diameter of more than 1 μm and 3 μm or less (assembly). When the rate is S2, it is preferable that (S1 + S2) satisfies 0.1 or more and 0.5 or less. When (S1 + S2) is 0.1 or more, it is difficult to weld with the workpiece, and it is possible to reduce the occurrence of minute tearing on the surface of the workpiece, to improve the properties of the workpiece surface, and to improve the welding resistance. By abrasion by this, the wear resistance of the tool can be improved. Moreover, when (S1 + S2) is 0.5 or less, the fall of toughness by high hardness can be suppressed and it becomes difficult to produce a crack and chipping. The more preferable range of (S1 + S2) is 0.3 or more and 0.5 or less.

Further, the area ratio of the third hard phase having a particle diameter of more than 1 μm and 3 μm or less (assembly) 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 (assembly) is S4. In this case, when S1 / (S1 + S2) is 0.1 or more and 0.4 or less, and S3 / (S3 + S4) satisfies 0.4 or more and 0.9 or less, both abrasion resistance and fracture resistance are further promoted, and the surface gloss of the workpiece Can be further improved. At this time, the more preferable range of S1 / (S1 + S2) is 0.3 or more and 0.4 or less, and the more preferable range of S3 / (S3 + S4) is 0.7 or more and 0.9 or less.

SS1 / (SS1 + SS2) is 0.5 or more 0.9 when the area of the 1st hard phase whose particle diameter is 1 micrometer or less (particulate) is SS1, and the area of the 2nd hard phase whose particle diameter is 1 micrometer or less (particulate) is SS2. It is preferable that it is the following. If SS1 / (SS1 + SS2) is 0.5 or more, since a little 1st hard phase exists more than a 2nd hard phase, a marked improvement in abrasion resistance can be expected. In addition, when SS1 / (SS1 + SS2) is 0.9 or less, the ratio which a 1st hard phase occupies among the fine hard phases does not become excess, and the wettability falls by the excessive presence of a fine 1st hard phase, and this wettability falls By the generation of minute pores, the possibility of causing deterioration of hardness can be suppressed. The more preferable range of SS1 / (SS1 + SS2) is 0.55 or more and 0.7 or less.

It is preferable that the area ratio of the sum of the area of a 3rd hard phase and the area of a 4th hard phase is larger than 40% with respect to the total area of a cermet (hard phase + bonded phase). In this case, since the thermal characteristics are stabilized, the thermal crack resistance can be improved, and further, the fracture resistance can be improved. In particular, it is preferable that most of these 3rd hard phase and 4th hard phase are granulated as mentioned above.

`` Combination phase ''

The bonding phase has at least one metal selected from iron group metals such as cobalt (Co), iron (Fe), and nickel (Ni) as a main component. The "main component" means that the hard phase constituent elements described above in the case where the bonding phase is substantially composed of only one or more metals selected from the iron group metals, or in the one or more metals selected from the iron group metals, are 0.1 to the total mass of the bonding phase. It is assumed that an alloy in which a solid solution is not less than 20% by mass, that is, not less than 80% by mass of the binder phase is composed of an iron group metal. In the case where the bonded phase employs a hard phase constituent element, toughness can be improved to improve toughness, thereby increasing the fracture resistance. In addition, since at least one of Co and Ni is a main component (80 mass% or more of the total mass of a bonding phase), a binding phase has a high wettability with a hard phase, and is excellent in corrosion resistance, Therefore, a more preferable cermet is used for the constituent material of a cutting tool. do.

In the case where both of Ni and Co are contained in the bonding phase, Ni / Co is 0.7 or more, particularly when the existence mass ratio of Ni and Co (the ratio of the mass of Ni to the mass of Co) in the bonding phase is Ni / Co. It is preferable that it is 1.5 or less. When Ni / Co satisfy | fills 0.7 or more and 1.5 or less, the fall of wettability can be reduced and high toughness can be maintained, the fall of hardness can be reduced, and high intensity | strength can be maintained. Ni / Co is particularly preferably 0.8 or more and 1.2 or less. Adjustment of Ni / Co can be performed by adjusting the addition amount of Co powder and Ni powder used for a raw material, for example.

[Other containing elements]

The cermet of the present invention may contain molybdenum (Mo). In the case of containing Mo, the second hard phase tends to be particularly easy to form. Therefore, since the wettability of a hard phase and a binding phase can be improved, a binding phase can fully exist around the particle which comprises a hard phase, and toughness can be improved. As for content of Mo, 0.01 mass% or more and 2.0 mass% or less are preferable. When the content of Mo is 0.01% by mass or more, as described above, the wettability can be improved as a whole of the cermet, and hardness and toughness can be improved. When the content of Mo is set to 2.0% by mass or less, the first hard phase is less likely to be formed and the second is relatively second. It can suppress that hard phase and 3rd hard phase increase. Therefore, the progress of the crack passing through the boundary between the hard core part and the peripheral part which is a conventional subject can be suppressed, and the expected fracture resistance can be obtained. More preferable content of Mo is 0.5 mass% or more and 1.5 mass% or less. It does not need to contain Mo.

<Cermet Tool>

"materials"

The cermet of the present invention having the above-described structure is provided with four types of hard phases as described above, so that not only wear resistance but also fracture resistance and welding resistance are excellent, and a cutting tool (cermet tool) where a good finish surface is desired. It can use suitably for the base material of the.

<< hard membrane >>

The said base material may be equipped with the hard membrane coated on at least one part of the surface. The hard film is preferably provided at least at the blade edge and its vicinity, and may be provided over the entire surface of the substrate surface. One layer or a multilayer may be sufficient as a hard film, and 1 micrometer-20 micrometers of total thickness are preferable. As the hard film forming method, both a chemical vapor deposition method (CVD method) such as thermal CVD method and a physical vapor deposition method (PVD method) such as arc ion plating 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 and 6 of the periodic table, aluminum (Al) and silicon (Si), carbon (C), nitrogen (N) and oxygen (O). ) And a compound with at least one element selected from the group consisting of boron (B), that is, compounds consisting of carbides, nitrides, oxides, borides, and solid solutions thereof of elements such as the above metals, cubic boron nitride (cBN ), Diamond, and one or more selected from the group consisting of diamond-like carbon (DLC). Specific film quality may include Ti (C, N), Al ₂ O ₃ , (Ti, Al) N, TiN, TiC, (Al, Cr) N, and the like.

<Method of manufacturing cermet>

Cermet is generally produced by a process called preparation of raw materials-grinding of raw materials and mixing-molding-sintering. The cermet of the present invention can be produced by adjusting the pulverization and mixing time and the sintering conditions using the raw material powder described later.

<< preparation of raw materials >>

The raw material includes a compound powder composed of a compound of at least one metal selected from the periodic table 4, 5 and 6 metals, a compound of at least one element of carbon (C) and nitrogen (N), and a binding phase. Powder, typically iron group metal powder, is used. As these powders, by using a fine powder and a relatively coarse powder, a cermet having a hard phase in which granulation and fine particles as described above are mixed is easy to be obtained. The size of the powder may be appropriately selected in consideration of the size of the hard particles.

In order to produce the first hard phase and the second hard phase, for example, Ti (C, N) powder is used. Although Ti (C, N) powder is conventionally produced using sponge Ti as a starting material, in particular, when the Ti (C, N) powder produced using TiO ₂ is used as a starting material, the fine first hard particles are produced. There is a tendency to form an image easily. Moreover, when using compound powder containing Mo as mentioned above, there exists a tendency which is easy to form a 2nd hard phase. To produce the third hard phase, a powder containing W, such as WC powder, is used. In order to produce the fourth hard phase, a compound powder containing a Group 4, 5, 6 metal of the periodic table excluding Ti and Ti, for example, (Ti, W) (C, N) powder is used. By using such a compound powder, it is easy to obtain the 4th hard phase particle | grains, ie, the particle | grains of the single-phase structure in which the periodic table group 4, 5, 6 metals except Ti and Ti were solid-dissolved.

Grinding and mixing

If the pulverization time is lengthened, the powder can be made fine and tends to produce fine hard particles in the cermet. However, when grinding time is too long, there exists a possibility that it may become difficult to form the compound which reaggregates or becomes too fine and becomes a nucleus. Preferable grinding and mixing time is 12 hours or more and 36 hours or less.

Sinter

When the sintering temperature is made too high, the particles constituting the hard phase grow, whereby coarse particles are likely to be present in the cermet, and in particular, there is a fear that it is difficult to produce the fourth hard phase particles. Therefore, as for sintering temperature, 1400 degreeC or more and 1600 degrees C or less are preferable. In the sintering step, when cooling the molded body heated by 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, it is particularly preferable to set it as relatively low pressure of 665 Pa or more and 6650 Pa or less. In addition, when the cooling rate is increased, specifically, 10 ° C / min or more, the fourth hard phase tends to be easily produced.

The coated cermet tool of the present invention is excellent in abrasion resistance and defect resistance and can be cut excellent in the quality of the processed surface of the workpiece. The cermet of the present invention can be suitably used for a constituent material of such a tool.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows typically four hard phases which exist in the cermet of this invention.

<Test Example>

The cutting tool which consists of a cermet was produced, 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 a raw material powder.

(1) Ti (C, N) powder with an average particle diameter 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 having an average particle diameter of 0.8 μm, and Ti (C, N) powder having an average particle diameter of 3.0 μm

All of these Ti (C, N) powders are powders produced using sponge Ti as a starting material, and have 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 having an average particle diameter of 2.8 μm

This (Ti, W) (C, N) powder is a powder in which W is dissolved in Ti (C, N) powder in advance, and the C / N ratio is 1/1.

(4) WC powder, NbC powder, TaC powder, Mo ₂ C powder, Ni powder, Co powder with an average particle diameter of 0.5 µm to 3.0 µm

These powders are all commercially available powders.

The prepared raw material powder was weighed and blended so as to have a blending ratio (mass%) shown in Table 1, and powders No. 1 to 12 were prepared.

Each powder was prepared together with an acetone solvent and a cemented carbide ball into a stainless steel pot, and ground and mixed (wet). Table 2 shows the raw material powder numbers used for the preparation of each sample and the pulverization and mixing time (hours). After grinding | pulverizing and mixing, a small amount of paraffin was added to the mixed powder obtained by drying, and it press-molded at the pressure of 98 Mpa using the metal mold | die, and the molded object of CNMG120408 shape was produced.

After heating each obtained molded object at 450 degreeC, removing paraffin, it heated up from room temperature to 1250 degreeC in vacuum, and further sintered (including a cooling process) on the conditions shown in Table 3, and obtained the sintered compact.

Arbitrary cross sections were taken about each obtained sintered compact, and the cross section was magnified 5000 times with the scanning electron microscope (SEM), and it observed. As a result, in the observation field of each sintered compact, black particles, particles in which part of the black particles are covered with gray areas (hereinafter, these two particles are collectively called black single particles), and the whole black particles are surrounded. Particles covered with a gray area (hereafter referred to as black-core double grain), particles covered with a gray area as a whole around white particles (hereafter referred to as white-center double grain) (white-core double grain)) and gray particles (hereinafter referred to as gray particles), at least one particle was identified. In the sintered compacts of samples No. 1 to 19, as shown in FIG. 1, black single particles (first hard phase 1), black core double particles (second hard phase 2), and white core double particles (third hard) Four kinds of particles of phase (3)) and gray particles (fourth hard phase (4)) were observed. The 1st hard phase 1 consists only of black particle, and the one part of black particle is covered by the gray area | region (peripheral part 1b), and the 2nd hard phase 2 is core part 2a. Black is black, the peripheral part 2b is gray, and the 3rd hard phase 3 has the core part 3a white, and the peripheral part 3b looks gray. Between the particles, there is a bonding phase 10. On the other hand, in the sintered compact of sample Nos. 100-105, at least one of black single particle, black core double particle, white core double particle, and gray particle was not observed.

As a result of investigating the composition of each particle by TEM-EDX analysis, as for black single particle, Ti (C, N), the core part of a black core double particle, Ti (C, N), the peripheral part which covers a core part, Ti, W, Nb, The composite carbonitride solid solution containing at least one metal of Ta and Mo, the white core double particle is a composite carbonitride solid solution containing at least one metal of Ti and W and Nb, Ta and Mo, and the W concentration at the core is The gray particles, which were higher than the periphery covering the core, were composed of a composite carbonitride solid solution containing at least one metal of Ti, W, Nb, Ta, and Mo. In addition, the gray particles had no clear boundary between the core and the periphery. In addition to the TEM-EDX analysis, the hard phase component analysis can be performed using EPMA, fluorescent X-rays, ICP-AES, or the like.

There existed a binding phase between the said particles, As a result of irradiation by TEM-EDX analysis, the binding phase was comprised substantially from Co and Ni. In the sample, there existed about several mass% of solid constituent elements dissolved in the bonding phase. As a result of the analysis, the content of Co in the sintered compact was almost the same as the amount of Co powder added to the raw material, and the content of Ni in the sintered compact tended to decrease by 0.2% to 0.3% compared to the amount of Ni powder added to the raw material. there was. In this regard, the content of the hard phase in each sample (sintered body) can be said to be almost the same as the amount (about 86% by mass) except for the addition amount of Co powder and Ni powder used for the raw material. In addition, the mass ratio Ni / Co of Ni and Co present in the bonded phase was determined. The results are shown in Table 2. Moreover, content (mass%) of Mo of each sample (sintered compact) was investigated by ICP analysis. The results are also shown in Table 2.

The particle diameter was calculated | required about all the particles which exist in the observation visual field of each sample (sintered compact) using the cross-sectional observation image (5000 times) of the said SEM. The particle diameter was made into the Martin diameter (the length of the line segment which bisects the projected area of particle | grains at the time of projecting particle | grains to a plane from a fixed direction). Specifically, the photomicrograph which observed the cross section of the sintered compact was used, and the length of the line segment which bisects the area of the particle which exists in the photomicrograph was made into the particle diameter. The particle diameter of the core structure was calculated | required the particle diameter in the state containing the peripheral part. As a result, almost no particle | grains whose particle diameter exceeded 3 micrometers were observed in any sample, and the hard phase was comprised by the particle | grains whose particle diameter is 3 micrometers or less substantially.

The area of each particle was calculated | required using the particle diameter (Martin diameter mentioned above) obtained about the cross-sectional observation image (5000 times). In addition, with respect to 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 diameter exceeding 1 μm and not more than 3 μm (hereinafter, these total areas are respectively , The total area of the particles having a particle diameter of 1 μm or less with respect to the granulated area (1), the assembled area (2), the assembled area (3), the assembled area (4), and the first hard phase (hereinafter, the total area) The total area of the particle | grains whose particle diameter is 1 micrometer or less (henceforth this total area is called a particulate area (2)) with respect to a 2nd hard phase was calculated, respectively. The sum of the assembled area (1), the assembled area (2), the assembled area (3), the assembled area (4), the particulate area (1), and the particulate area (2) is taken as the total area of the hard phase and the total area of the hard phase is determined. Table 4 shows the total ratio of the granulated areas (1) to (4), that is, the granulated area ratio "total granulated / hard phase whole" (%). In addition, the area ratio (%) of each of the assembly area (1), assembly area (2), assembly area (3), assembly area (4), particulate area (1), and particulate area (2) with respect to the total area of the hard phase. ) Is shown in Table 4. The area ratio of the assembly area (1) to the total area of the hard phase is S1, the area ratio of the assembly area (2) is S2, the area ratio of the assembly area (3) is S3, and the area ratio of the assembly area (4) is S4. At this time, (S1 + S2), S1 / (S1 + S2), and S3 / (S3 + S4) were obtained. The results are shown in Table 4. In addition, when the particulate area (1) is SS1 and the particulate area (2) is SS2: the size of the area of SS1 / (SS1 + SS2) and the entire cermet (hard phase + bonded phase) (here, the viewing field of view). Area ratio of the total area of the area of the third hard phase and the area of the fourth hard phase: (third + fourth) / (the whole cermet) was obtained. The results are also shown in Table 4. In addition, in the sample in which the 3rd hard phase and the 4th hard phase existed, the 3rd hard phase particle | grains or agent whose particle diameter of the 3rd hard phase particle | grains or the 4th hard phase particle | grains exceed about 1 micrometer, and whose particle diameter is 1 micrometer or less 4 Hard particles were hardly observed.

The surface of each obtained sintered compact was subjected to the surface grinding | polishing process, and the blade edge | tip processing, respectively, and the cutting tip (cutting tool) which has the breaker of CNMG120408 shape was produced. Using each obtained cutting tip, the cutting test (all turning) was performed on the conditions shown in following Table 5, respectively, and the wear resistance, the fracture resistance, and the surface roughness of the process surface were investigated. The results are shown in Table 6. Surface roughness Ra was measured according to JISB0601 (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 are present are sample Nos in which any one of the four kinds is not present. Compared with .100-105, it turns out that it is excellent in abrasion resistance and also excellent in fracture resistance. Moreover, these sample Nos. 1-19 show that the surface roughness Ra of the processed surface of a workpiece is small, and the surface quality of a processed surface is high.

In Samples Nos. 1 to 19, in particular, when the area ratio of the granulated particles satisfies 60% or more and 90% or less, it is found that the wear resistance and the fracture resistance tend to be more excellent due to the improvement in hardness and the fracture toughness. Can be. Further, among samples Nos. 1 to 19, in particular, a sample in which (S1 + S2) satisfies 0.1 or more and 0.5 or less, S1 / (S1 + S2) is 0.1 or more and 0.4 or less, and S3 / (S3 + S4) is 0.4 The sample which satisfies the above 0.9 or less tends to become smaller surface roughness Ra, and it turns out that it is excellent in surface quality. It turns out that the sample in which SS1 / (SS1 + SS2) satisfy | fills 0.5 or more and 0.9 or less among sample Nos. 1-19 especially tends to be more excellent in abrasion resistance. Moreover, it turns out that the sample in which (3rd + 4th) / (the whole cermet) exceeds 40% is especially excellent in toughness among sample No.1-19.

On the surface of the cutting tips of Sample Nos. 1 to 19, a coating tip having a (Ti, Al) N film (thickness 4 µm) formed by arc ion plating was formed, and the abrasion resistance test was carried out under the test conditions shown in Table 5. It was done. As a result, any of the samples had better abrasion resistance as compared with the case where there was no hard film.

Moreover, embodiment mentioned above can be changed suitably, without deviating from the summary of this invention, It is not limited to the structure mentioned above. For example, the composition and average particle diameter of a raw material powder, the presence state of each particle of a hard phase, and the composition and thickness of a hard film can be changed suitably.

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

1: 1st hard phase 1b: peripheral part
2: second hard phase 2a, 3a: deep
2b, 3b: Peripheral 3: third hard phase
4: fourth hard phase 10: binding phase

Claims (17)

Bond phase in which the hard phase comprising an iron group metal comprises at least one compound selected from the group consisting of carbides, nitrides, carbonitrides and solid solutions thereof of the Group 4, 5, and 6 metals of the periodic table As a cermet formed by combining,
Containing 70 mass% or more and 97 mass% or less of the hard phase, and the remaining part contains a binding phase,
The hard phase contains the following first hard phase, second hard phase, third hard phase, and fourth hard phase:
1st hard phase: containing only the single phase of titanium carbonitride, or the one part around titanium carbonitride is selected from titanium and group 4, 5, and 6 metals of a periodic table (except titanium) Hard phase of single-phase structure covered with complex carbonitride solid solution with the above metal
2nd hard phase: It is a hard phase of a core-rim structure which has a core part and the peripheral part which covers the whole periphery of this core part, The said core part consists of titanium carbonitride, The said peripheral part is titanium And a hard phase composed of a complex carbonitride solid solution with at least one metal selected from the Group 4, 5, and 6 metals (except titanium) of the periodic table.
3rd hard phase: It is a hard phase of a core structure which has a core part and the periphery part which covers the whole periphery of this core part, The said core part and the said peripheral part consist of the same element, and are a composite carbonitride solid solution containing titanium and tungsten And a hard phase in which the tungsten concentration of the core is greater than the tungsten concentration of the peripheral portion.
Fourth hard phase: A hard phase of a single phase structure comprising a composite carbonitride solid solution of titanium and at least one metal selected from the Group 4, 5, and 6 metals of the periodic table (except titanium). The hard phase according to claim 1, wherein the hard phase of 60% or more and 90% or less with respect to the total area of the hard phase includes granules having a particle diameter of more than 1 µm and 3 µm or less, and the hard phase of the remaining portion has a particle diameter of 1.0. Containing fine particles having a thickness of less than or equal to
The granulation is composed of the first hard phase, the second hard phase, the third hard phase, and the fourth hard phase,
The said granules are comprised from the said 1st hard phase and the said 2nd hard phase. (S1 + S2) is 0.1 or more and 0.5 or less, when the area ratio of the 1st hard phase of the granulation is S1 and the area ratio of the second hard phase of the granulation is S2 with respect to the total area of the hard phase. Cermet, characterized in that. 3. The area ratio of the first hard phase of the granulation is S1, the area ratio of the second hard phase of the granulation is S2, and the area ratio of the third hard phase of the granulation is S3, with respect to the total area of the hard phase. When the area ratio of the fourth hard phase of the granulation is S4, 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. The area ratio of the first hard phase of the granulation is S1, the area ratio of the second hard phase of the granulation is S2, and the area ratio of the third hard phase of the granulation is S3, with respect to the total area of the hard phase. When the area ratio of the fourth hard phase of the granulation is S4, 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. The area of the first hard phase having a particle diameter of 1.0 μm or less is SS1, and the area of the second hard phase having the particle diameter of 1.0 μm or less is SS2, wherein SS1 / (SS1 + SS2) is 0.5 or more and 0.9. The cermet characterized by the following. The area of the first hard phase having the particle diameter of 1.0 m or less is SS1, and the area of the second hard phase having the particle diameter of 1.0 m or less is SS2, wherein SS1 / (SS1 + SS2) is 0.5 or more and 0.9 The cermet characterized by the following. The area of the first hard phase having the particle diameter of 1.0 m or less is SS1, and the area of the second hard phase having the particle diameter of 1.0 m or less is SS2, wherein SS1 / (SS1 + SS2) is 0.5 or more and 0.9 The cermet characterized by the following. The area of the first hard phase having the particle diameter of 1.0 μm or less is SS1, and the area of the second hard phase having the particle diameter of 1.0 μm or less is SS2, and SS1 / (SS1 + SS2) is 0.5 or more and 0.9. The cermet characterized by the following. The cermet according to any one of claims 1 to 9, wherein an area ratio of the sum of the area of the third hard phase and the area of the fourth hard phase is greater than 40% and less than 100% with respect to the total area of the cermet. The cermet according to any one of claims 1 to 9, wherein the cermet contains nickel (Ni) and cobalt (Co) on a bond,
Ni / Co is 0.7 or more and 1.5 or less, when the mass ratio of Ni and Co in the said bonded phase is Ni / Co, The cermet characterized by the above-mentioned. 11. The cermet according to claim 10, wherein the cermet contains nickel (Ni) and cobalt (Co) on a bond.
Ni / Co is 0.7 or more and 1.5 or less, when the mass ratio of Ni and Co in the said bonded phase is Ni / Co, The cermet characterized by the above-mentioned. The cermet according to any one of claims 1 to 9, wherein the cermet contains 0.01% by mass or more and 2.0% by mass or less of molybdenum. The cermet according to claim 10, wherein the cermet contains 0.01% by mass or more and 2.0% by mass or less of molybdenum. The cermet according to claim 11, wherein the cermet contains 0.01% by mass or more and 2.0% by mass or less of molybdenum. The cermet according to claim 12, wherein the cermet contains 0.01% by mass or more and 2.0% by mass or less of molybdenum. A coated cermet tool comprising a substrate comprising the cermet according to claim 1 and a hard film coated on part or the entire surface of the substrate.

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