JP6819018B2 - TiCN-based cermet cutting tool - Google Patents

Description

The present invention relates to a TiCN-based cermet cutting tool that exhibits excellent fracture resistance in cutting of carbon steel, alloy steel, etc., and exhibits excellent cutting performance over a long period of use.

Conventionally, as a cutting tool, a WC-based cemented carbide cutting tool, a TiCN-based cermet cutting tool, a cBN-based cutting tool, and the like are known.
Of these, TiCN-based cermet cutting tools are used as steel finishing tools because they have low affinity for steel and are excellent in finished surface roughness. However, their tool characteristics, such as plastic deformation resistance, are used. Several proposals have been made to further improve impact resistance, fracture resistance, heat crack resistance, welding resistance, wear resistance, and the like.

For example, in Patent Document 1,
"As a binding phase forming component
W: 2 to 15% by weight (hereinafter, simply indicated by "%"),
One or two of Co and Ni: 5-25%,
As a hard phase forming component,
Titanium nitride: 10-40%,
Tantalum Carbide: 3-30%,
Tungsten carbide: 5-25%,
Niobium Carbide: 1-25%,
Zirconium carbide: 0.1-5%,
A cermet having a composition containing titanium carbide as a hard phase forming component and unavoidable impurities, and a cutting tool made of this cermet. "
Has been proposed.
The TiC-based cermet is excellent in plastic deformation resistance and impact resistance. Moreover, since it has high hardness, the cutting tool composed of this cermet can be used for various cutting operations such as high-speed cutting, high-feed and high-cut heavy-duty cutting, or milling with a large load and thermal impact. It is said that it exhibits excellent fracture resistance and abrasion resistance in intermittent cutting such as.

Further, in Patent Document 2,
"70% by mass or more and 97% by mass or less of a hard phase composed of one or more compounds selected from the group consisting of carbides, nitrides, carbonitrides and solid solutions of these groups 4 and 5 and 6 metals of the Periodic Table. In a coated cermet tool whose base material is a cermet whose balance is a bonding phase containing an iron group metal as a main component and an unavoidable impurity.
The hard phase contains four types of hard phases (first hard phase, second hard phase, third hard phase, fourth hard phase) having different compositions and forms.
In the microstructure photograph of an arbitrary cross section of the cermet by a scanning electron microscope (SEM), the hard phase having a particle size of 60% or more and 90% or less with respect to the total area of the hard phase consists of coarse particles having a particle size of more than 1 μm and less than 3 μm. The remaining hard phase consists of fine particles with a particle size of 1.0 μm or less.
The coarse grain is composed of at least one of the first hard phase and the second hard phase, the third hard phase, and the fourth hard phase.
It has been proposed that the fine particles are composed of the first hard phase and the second hard phase.
Here, the first hard phase: consists of only a single phase of titanium nitride, or a part around titanium nitride is selected from titanium and metals of groups 4, 5 and 6 of the periodic table (excluding titanium). A hard phase with a single-phase structure, which is covered with a composite carbonitride solid solution with one or more metals.
Second hard phase: A hard phase having a core structure including a core portion and a peripheral portion that covers the entire circumference of the core portion. The core portion is made of titanium carbonitride, and the peripheral portion is titanium. And a hard phase composed of a composite carbonitride solid solution with one or more metals selected from the Group 4, 5 and 6 metals (excluding titanium) of the Periodic Table.
Third hard phase: A hard phase having a core structure including a core portion and a peripheral portion that covers the entire circumference of the core portion, and the core portion and the peripheral portion are composed of the same element. A hard phase composed of a composite carbonitride solid solution containing at least titanium and tungsten, wherein the tungsten concentration in the core portion is higher than the tungsten concentration in the peripheral portion.
Fourth hard phase: A simple composite of a solid carbon nitride solution of titanium and tungsten or tungsten and one or more metals selected from the metals of Groups 4, 5 and 6 of the Periodic Table (excluding titanium and tungsten). Hard phase of phase structure,
Is.
According to this coated cermet tool, it is said that it is possible to perform cutting with excellent fracture resistance and glossiness of the machined surface of the work material.

Further, in Patent Document 3,
"It has a structure composed of a hard phase and a bonded phase, and has Ti, Nb and / or Ta, and W as a sintered body composition, and the value obtained by converting the Ti into a carbide and the Nb and / or Ta. Is a total of the value obtained by converting the amount of water into carbide and the value obtained by converting W into carbide, which is 70 to 95% by weight based on the whole structure (of which W is the value converted into carbide and is based on the whole structure). 15-35% by weight),
A cermet insert containing Co and / or Ni.
As the hard phase, one or more of the following (1) to (3) is provided (however, the following (2) alone is excluded).
(1) A first hard phase having a core structure containing a titanium nitride phase in the core and a CN phase (Ti, W, Ta / Nb) in the periphery.
(2) A second hard phase having a core structure in which both the core portion and the peripheral portion include a (Ti, W, Ta / Nb) CN phase.
(3) A third hard phase having a single-phase structure composed of a titanium carbonitride phase,
Further, a cermet insert characterized by uneven distribution of a W wealthy phase containing more W than the surroundings in the titanium nitride phase and a cutting tool provided with the cermet insert have been proposed.
Further, in at least one structure of the surface and the cross section of the insert, the W wealthy phase is unevenly distributed in the titanium nitride phase in at least one of linear and mesh-like states, and the charcoal. A cermet insert in which the W wealthy phase is unevenly distributed in at least one of layered, columnar, and prismatic in the titanium nitride phase has been proposed.
Then, according to the cutting tool provided with this cermet insert, in particular, the W wealthy phase containing more W than the surroundings is unevenly distributed in the titanium carbonitride phase (linear in FIGS. 8 to 10 of Patent Document 3). It is said that excellent fracture resistance and abrasion resistance are exhibited by (observed as a mesh-like white line or a layered white spot).

Japanese Unexamined Patent Publication No. 64-39343 Japanese Patent No. 4690475 Japanese Patent No. 4659682

In recent years, there have been strong demands for labor saving, energy saving, high speed, high efficiency, and low cost in the technical field of cutting, and there are remarkable improvements in the performance of cutting equipment, but on the other hand, for cutting tools. The usage conditions are becoming more and more severe, and it is required to improve the performance of the TiCN-based cermet itself and further extend the service life of the TiCN-based cermet cutting tool.
TiCN-based cermets generally have insufficient hardness and toughness compared to WC-based cemented carbides. Therefore, in order to extend the life of TiCN-based cermet cutting tools, fracture resistance is required. Further improvement is needed.

The cutting tools shown in Patent Documents 1 to 3 have been proposed for the purpose of improving the above-mentioned characteristics, but in recent years, the cutting tools having a complicated shape as shown in FIG. 1 (a). Is being used.
When a cutting tool having such a complicated shape is manufactured with a TiCN-based cermet, the TiCN-based cermet has insufficient moldability and sinterability as compared with a WC-based cemented carbide, and therefore cracks occur in the sintered body. (See FIG. 1 (b)), and the TiCN-based cermet cutting tool produced has a problem that the tool life is short because the fracture resistance is not sufficient.
Therefore, there is a demand for a TiCN-based cermet cutting tool that has excellent formability and sinterability, and exhibits excellent cutting performance over a long period of time without causing abnormal damage such as defects during cutting.

From the above viewpoint, the present inventor has provided a TiCN-based cermet cutting tool that has excellent moldability and sinterability, suppresses the occurrence of abnormal damage such as defects, and exhibits excellent cutting performance over a long period of use. As a result of diligent research to provide it, the following findings were obtained.

The present inventor first studied the causes of abnormal damage such as chipping in TiCN-based cermet cutting tools, and found that the fracture resistance was determined by the aspect ratio of the hard phase consisting of the TiCN single phase generated in the cermet. It was found that the fracture resistance is remarkably improved in the cutting process of carbon steel, alloy steel, etc., when the aspect ratio of the hard phase is maintained in an appropriate numerical range.
Then, in order to suppress the occurrence of defects and improve the abnormal damage resistance, further studies are made on the manufacturing means for maintaining the aspect ratio of the hard phase consisting of a single phase of TiCN in the TiCN-based cermet within an appropriate range. We proceeded and obtained the following findings.

In general, TiCN-based cermets are composed of at least one of TiCN powder for forming a hard phase, Co powder or Ni powder for forming a bonded phase, and other powder for forming a hard phase such as WC powder. It is produced by blending so as to prepare raw material powders, crushing and mixing these raw material powders, press-molding the raw material powders, and then sintering the molded body.
Then, sponge Ti is usually used as a starting material for the TiCN powder, but since the step of producing TiCN powder from sponge Ti includes a pulverization step, the obtained TiCN for forming a hard phase is included. A powder having a large aspect ratio will be mixed in the powder.
Further, when crushing and mixing the raw material powder, a ball mill or attritor mixing using a cemented carbide ball is usually performed, but even in this step, a hard cemented carbide ball having a large crushing energy is used. , TiCN powder for forming a hard phase is pulverized to form TiCN powder having a large aspect ratio.
In this way, when a TiCN-based cermet is produced using TiCN powder for forming a hard phase in which a large amount of TiCN powder having a large aspect ratio is present, when a compact compact compact having a complicated shape is press-molded, compact molding is performed. Cracks occur in the body, which also causes sintered cracks.

Therefore, the present inventor has used TiO ₂ instead of sponge Ti as a starting material for TiCN powder in the production of TiCN-based cermet as a means for maintaining the aspect ratio of the first hard phase in the TiCN-based cermet within an appropriate range. (Titanium oxide) was used, and in the crushing / mixing step of the raw material powder, crushing / mixing was performed using a cermet ball having a small crushing energy, and a powder compact having a complicated shape was formed by press molding. Further, in the TiCN-based cermet obtained by sintering this powder compact, the average aspect ratio of the hard phase composed of a single phase of TiCN is 1.5 to 1.8. Being kept within range,
Further, TiO ₂ (titanium oxide) is used as a starting material for the TiCN powder, and the raw material powder is crushed and mixed with a cermet ball. The TiCN-based cermet is before the crushing and mixing treatment represented by a jet mill or the like. It has been found that since the production of fine particles is reduced as compared with the treated powder, it is excellent in moldability and sinterability, and even a TiCN-based cermet having a complicated shape can be easily produced.
The cutting tool made of TiCN-based cermet produced above has excellent wear resistance over a long period of use without causing abnormal damage such as chipping in cutting of carbon steel, alloy steel, etc., for example. I found that it would work.

The present invention has been made based on the above findings.
"In a TiCN-based cermet cutting tool made of a TiCN-based cermet sintered body,
(A) The TiCN-based cermet sintered body is ZrC: 0.5 to 2.0%, WC: 15 to 25%, and the total of one or two of TaC and NbC: 5 to 5% by mass. 20%, total of 1 or 2 of Co and Ni: 12-25%, the balance is an average composition of unavoidable impurities and TiCN (however, Zr, W, Ta and Nb are all carbides. Shows the composition value converted as)
(B) When the cross section of the TiCN-based cermet sintered body is observed with a scanning electron microscope, it has a sintered body structure in which a bonded phase, a first hard phase and a second hard phase are present.
(C) The binding phase is mainly composed of one or two of Co and Ni.
(D) The first hard phase is composed of a single phase of TiCN, and the average contact interface length between the first hard phase and the bonded phase is 50% or more of the grain boundary length of the first hard phase. Yes, the average aspect ratio of the first hard phase is 1.5 or more and 1.8 or less.
(E) The second hard phase is composed of a composite carbonitride of Ti, Zr, W, and one or two of Ta and Nb.
(F) A cutting tool made of TiCN-based cermet, wherein the porosity of the TiCN-based cermet sintered body is A04 or less and B00 defined by the Cemented Carbide Tool Association standard CIS006C-2007. "
It has the characteristics of.

The TiCN-based cermet cutting tool of the present invention is composed of the TiCN-based cermet sintered body having the above-mentioned average composition, sintered body structure and porosity, but has an average component composition, sintered body structure and perforations. The reason for determining the degree as described above will be explained below.
In the following, a TiCN-based cermet cutting tool may be simply referred to as a "cermet tool", and a TiCN-based cermet sintered body may be simply referred to as a "cermet sintered body".

The reason for determining the average component composition of the TiCN-based cermet sintered body is as follows.

ZrC:
Zr is a hard phase-forming component that forms carbides and carbonitrides like Ti, or a composite carbonitride of Ti, Zr, Ta, Nb, and W, and improves the wear resistance of cermet tools. However, when the ZrC content (the content of Zr converted to carbide) is less than 0.5% by mass, the effect is small, while when the content exceeds 2.0% by mass, the sinterability is impaired. The average composition of ZrC is 0.5 to 2.0% by mass because it causes residual cavities and lowers the strength.
Regarding W, Ta, and Nb, which are the components of the cermet sintered body, the reasons for limiting the component composition of those converted into carbides will be described as in the case of Zr.

WC:
When the WC content in the cermet sintered body is less than 15% by mass, the W content ratio dissolved mainly in the bonded phase is insufficient, and the desired high-temperature hardness cannot be maintained, while the WC content. If it exceeds 25% by mass, the content ratio of the W component in the bonded phase becomes too high, and the high temperature strength of the bonded phase itself drops sharply, which causes defects and chipping to easily occur. The average composition of WC in the tool is 15-25% by mass.

One or two of TaC and NbC:
Like WC, TaC and NbC dissolve in the Co and Ni components that form the bonded phase during sintering and precipitate during cooling to form the second hard phase, improving the high temperature strength of the second hard phase. Although it has an action, if the total of one or two types of TaC and NbC is less than 5% by mass, the desired improving effect cannot be obtained for the action, while if the content ratio exceeds 20% by mass, the second hard phase Since the content ratio in the content becomes too high, which causes a decrease in the hardness of the second hard phase, the total content of one or two types of TaC and NbC is set to 5 to 20% by mass.

One or two of Co and Ni:
One or two of Co and Ni form the main body of the bonding phase to give the cermet tool the desired strength and toughness, but if the total content is less than 12% by mass, sinterability can be ensured. On the other hand, if the total content exceeds 20% by mass, wear will rapidly progress. Therefore, the total content of one or two types of Co and Ni is set to 12 to 20% by mass.
Although W, Ta, Nb, Zr, and Ti are actually dissolved in the bonded phase, 80% or more of the total mass of the bonded phase is one or two of Co and Ni. Since it is composed of, it is described that the main body of the bonding phase is composed of one or two kinds of Co and Ni.

TiCN:
The cermet tool of the present invention contains the above-mentioned components (one or two of ZrC, WC, TaC and NbC, Co and Ni, excluding impurities inevitably mixed in from the manufacturing raw material or in the manufacturing process. The rest of one or two of them) is substantially composed of TiCN.
TiCN forms a first hard phase at the time of sintering and also forms a second hard phase together with Zr, W, Ta, and Nb to improve the hardness of the cermet tool, thereby contributing to the improvement of wear resistance. However, if the content ratio is less than 40% by mass, the desired hardness cannot be secured, while if the content ratio exceeds 60% by mass, the strength of the cermet tool drops sharply. Since chipping and chipping are likely to occur during cutting, it is desirable to set the content ratio to 40 to 60% by mass.

Next, the sintered body structure of the cermet sintered body of the present invention will be described.
As shown in FIG. 2, when the cross section of the cermet sintered body of the present invention is observed with a scanning electron microscope, a sintered body structure in which a bonded phase, a first hard phase and a second hard phase are present is formed. You can see that.
Of the sintered body structure, the bonded phase is substantially composed of one or two of Co and Ni, but W, Ta, Nb, Ti, and Zr are partially dissolved.
The first hard phase is a hard phase composed of a single phase of TiCN, and the second hard phase is a composite of Ti, Zr, W, and one or two of Ta and Nb. It is a hard phase composed of carbonitride.

The first hard phase is a single phase of TiCN, and the average contact interface between the first hard phase and the bonded phase in a predetermined observation range (for example, an observation region of 100 μm ² ) using a scanning electron microscope. When the length is measured, the average contact interface length is 50% or more of the grain boundary length of the first hard phase.
This is because when the average contact interface length between the first hard phase and the bonded phase is less than 50%, the first hard phase is shed due to the decrease in adhesion between the bonded phase and the first hard phase. This is because it causes chipping and defects.

Further, for example, when the aspect ratios of the individual first hard phases existing in the observation region of 100 μm ² are obtained and the average aspect ratio obtained by averaging these values is calculated, the average aspect ratio is 1.5 or more. The range is 1.8 or less.
The reason why the average aspect ratio is set to the range of 1.5 or more and 1.8 or less is as follows.
That is, if the average aspect ratio is less than 1.5, the shape of the first hard phase becomes close to a spherical shape, so that the contact interface between the coupling phase and the first hard phase decreases, and therefore, when cracks occur during cutting. , The growth of cracks cannot be suppressed, and as a result, the fracture resistance is lowered.
On the other hand, if the average aspect ratio exceeds 1.8, the moldability is lowered and cracks are generated in the powder compact when press-molded into the powder compact, and these cracks are reduced in sinterability ( For example, it causes sintering cracks), and also causes abnormal damage such as defects during cutting.

Manufacture of TiCN-based cermet sintered body:
One of the manufacturing features of the cermet sintered body of the present invention is that the TiCN powder produced using TIO ₂ as a starting material is used without using the TiCN powder using sponge Ti as a starting material. Another feature is that when the raw material powder is crushed and mixed, cermet balls or titania balls are used instead of cemented carbide balls for crushing and mixing.
The cermet sintered body of the present invention can be produced, for example, by the following steps.
(A) First, using TiO ₂ as a starting material, a TiCN powder having an average particle size of 0.5 to 2.0 μm is prepared without performing a pulverization step.
The production of TiCN powder using TiO ₂ as a starting material has already been known before the application of the present application (for example, JP-A-8-333107, JP-A-2003-27114, JP-A-2003-137654). Etc.), and the manufacturing method itself is not particularly limited.
(B) Next, the TiCN powder produced in (a) above, ZrC powder, WC powder, Ta powder, Nb powder, Co powder, and Ni powder are charged into an attritor, and a cermet ball is used as a mixed medium. , The rotation speed of the agitator is reduced, and the raw material powder is prepared by crushing and mixing in a state where the crushing force is reduced.
Since the cermet balls have a weaker crushing power than the WC-based cemented carbide balls, they are mainly mixed in the attritor.
(C) Next, the raw material powder is press-molded at a pressure of 50 to 80 MPa to prepare a powder compact having a predetermined shape.
Since the raw material powder has excellent moldability, cracks and the like do not occur in the molded product even when a compact compact molded product having a complicated shape is produced.
(D) Next, the powder compact
(A) The temperature was raised from room temperature to 1350 in a vacuum atmosphere of 10 Pa or less at 2 ° C./min. The temperature rises at the rate of
(B) From the above temperature to a predetermined sintering temperature within the range of 1550 ° C. in an argon atmosphere of 67 Pa, 2 ° C./min. The temperature rises at the rate of
(C) Hold for a predetermined time in a nitrogen atmosphere of 200 Pa at the sintering temperature.
(E) After that, cool from the above sintering temperature to room temperature.
By the steps (a) to (e) above, the cermet sintered body of the present invention having excellent moldability and sinterability can be produced.
Further, after that, the cermet tool of the present invention having excellent fracture resistance can be produced by machining into a predetermined shape.

The average component composition, sintered body structure, and manufacturing method of the cermet tool of the present invention are as described above, but the cermet sintered body of the present invention is excellent in moldability and sinterability, and the density of the sintered body is improved. Since it can be increased, the strength and toughness of the cermet tool can be further improved.
The density of the cermet sintered body of the present invention is A04 or less and B00 when expressed in the Cemented Carbide Tool Association standard CIS006C-2007 regarding the size of residual cavities, which are structural defects of the sintered body.
Here, type A means a residual nest having a size of less than 10 μm, and type B means a residual nest having a size of 10 μm or more and less than 25 μm. In the present invention, the size of the residual nest of type A is A04 or less and is coarse. By setting the B-type residual nest, which is a large residual nest, to B00, the strength and toughness of the cermet tool can be increased without forming a coarse residual nest in the cermet sintered body.

The cermet tool of the present invention defines the composition, the structure of the sintered body and the porosity within an appropriate range, and in particular, the structure of the cermet sintered body is composed of a bonded phase, a first hard phase and a second hard phase. As for the first hard phase, by setting the aspect ratio in the range of 1.5 or more and 1.8 or less, abnormal damage such as chipping may occur in cutting of carbon steel, alloy steel, etc., for example. It exhibits excellent cutting performance over a long period of use.

(A) shows a perspective view of an example of a cutting tool having a complicated shape, and (b) shows a schematic vertical cross-sectional view of (a). An example of a scanning electron microscope image about the cross section of the cermet sintered body of this invention is shown. An example of a scanning electron microscope image of a cross section of a conventional cermet sintered body is shown.

Next, milling will be specifically described as an example of the present invention.
The cutting tool of the present invention is not limited to the milling cutter described in the examples, and can naturally be applied as a cutting tool for turning and drilling.

Using TiO ₂ as a starting material for TiCN powder and using a cermet ball as a mixed medium in an attritor, the cermet cutting tool of the present invention was produced in the following steps (A) to (E). ..

(A) As the powder for producing the cermet sintered body, TiCN powder having an average particle size of 1.5 μm, ZrC powder having an average particle size of 2.0 μm, WC powder having an average particle size of 6.0 μm, and an average particle size of 1. A TaC powder having an average particle size of 0 μm, an NbC powder having an average particle size of 1.0 μm, a Co powder having an average particle size of 0.9 μm, and a Ni powder having an average particle size of 0.8 μm were prepared, and each of these powders was designated as shown in Table 1. Raw material powders A to F were prepared by blending so as to have a blending composition.
Here, the TiCN powder is a TiCN powder produced using TiO ₂ as a starting material, and the production method thereof is as follows.
TiO ₂ and a predetermined amount of graphite are wet-mixed, dried, and then heat-treated in a mixed gas of nitrogen and argon at a temperature of 1700 to 2000 ° C., cooled to room temperature, and then crushed and sieved. TiCN powder.

(B) Next, the raw material powders A to F are filled in an attritor, and at the same time, a cermet ball as a mixed medium is put into the attritor, and the conditions shown in Table 2, that is, the agitator Wet mixing was performed at a rotation speed of 25 rpm for 16 to 20 hours to prepare mixed powders 1 to 6.
The ratio of the amount of cermet balls charged (kg) to the amount of raw material powder charged (kg) into the attritor (= (the amount of cermet balls charged) / (the amount of raw material powder filled)) is shown in Table 2. As shown in, it is 5.0 to 7.0.
The cermet ball used here is made by pressing a cermet raw material having the same composition as that of the tool 1 of the present invention into an 8 mm ball, sintering the ball, and then polishing the ball.

(C) Next, the mixed powders 1 to 6 prepared above were dried and then press-molded at a pressure of 50 to 80 MPa shown in Table 2 to prepare powder compacts 1 to 6.

(D) Next, the powder compacts 1 to 6 are
(A) The temperature was raised from room temperature to 1350 in a vacuum atmosphere of 10 Pa or less at 2 ° C./min. The temperature rises at the rate of
(B) From the above temperature to the sintering temperature shown in Table 2 in an argon atmosphere of 67 Pa, 2 ° C./min. The temperature rises at the rate of
(C) After holding for a predetermined time shown in Table 2 in a nitrogen atmosphere of 200 Pa at the sintering temperature,
Cermet sintered bodies 1 to 6 shown in Table 2 were prepared by cooling to room temperature.

(E) Next, the TiCN-based cermet of the present invention shown in Table 3 having the insert shape SNMU140812ANER-M shown in FIGS. 1 (a) and 1 (b) by grinding from the above cermet sintered bodies 1 to 6 Tools 1 to 6 (referred to as "tools 1 to 6 of the present invention") were manufactured respectively.

The average composition, the structure of the sintered body, and the porosity of the cermet sintered bodies 1 to 6 constituting the tools 1 to 6 of the present invention prepared above were determined.
Each observation / measurement method is as follows.

≪Average composition≫
The cross section of the cermet was observed with a scanning electron microscope (SEM) equipped with an energy dispersive X-ray analyzer (EDS), the content of elements was measured in a region of 100 mm ² , and TiCN, WC, ZrC, NbC, Calculated by converting as TaC, Co, and Ni.

≪Sintered body structure≫
First hard phase:
The darkest colored particles (see FIG. 2) on the image observed with a scanning electron microscope (SEM) and mainly composed of a single phase of TiCN can be determined by using an Auger electron spectrometer (AES). It can be confirmed by performing element mapping of the portion observed by the SEM.
The aspect ratio of each particle was calculated from the lengths of the long side and the short side by extracting individual crystals from the crystal orientation analysis by electron backscatter diffraction (EBSD) and performing elliptical approximation by image analysis. At the time of crystal identification by EBSD, when the particles were in contact with each other and the crystal orientation was deviated by 5 ° or more, the grain boundary was calculated as another particle.
Regarding the average contact interface length with the bonded phase, the total grain boundary length of the first hard phase and the grain boundary length of the contact portion between the first hard phase and the bonded phase were obtained from the crystal orientation analysis by the EBSD. Was calculated.
Second hard phase:
Dark brown particles (see FIG. 2) on an image observed with a scanning electron microscope (SEM)), and element mapping of the portion observed with the SEM is performed using an Auger electron spectrometer (AES). It was confirmed that it was a composite carbide nitride of Ti, Zr, W and one or two of Ta and Nb.

Perforation:
The surface-polished cermet cross section was observed with an optical microscope at 100 times, and the porosity was examined from the classification and grade based on the Carbide Tool Association standard CIS006C-2007.
Tables 3 and 5 show the average composition, sintered body structure, and porosity obtained above.
The cermet sintered bodies 1 to 6 and 11 to 16 constituting the tools 1 to 6 and 11 to 16 of the present invention have cracks in the sintered body in order to judge the quality of the sinterability and moldability. The appearance and cross section were confirmed with an optical microscope.
The results are also shown in Table 3.

[Comparison example]
Further, for the purpose of comparison, a cermet cutting tool of a comparative example was produced in the following steps.
First, TiCN powder having an average particle size of 1.5 μm is prepared from TiO ₂ or sponge Ti, and this TiCN powder, ZrC powder having an average particle size of 2.0 μm, WC powder having an average particle size of 6.0 μm, and average particle size 1 .0 μm TaC powder, NbC powder with an average particle size of 1.0 μm, Co powder with an average particle size of 0.9 μm, and Ni powder with an average particle size of 0.8 μm were blended so as to have a predetermined blending composition, and Table 4 The raw material powders a to f shown in the above were prepared.
Then, the raw material powders a to f are filled in the attritor, and at the same time, either the WC-based cemented carbide balls or the cermet balls as the mixed media are charged into the attritor, and the conditions shown in Table 5 are as follows. That is, the mixed powders 11 to 16 shown in Table 5 were prepared by wet mixing for 16 to 20 hours at a rotation speed of the agitator of 20 to 30 rpm.
The ratio of the input amount (kg) of the mixed media to the filling amount (kg) of the raw material powder into the attritor (= (input amount of the mixed media) / (filling amount of the raw material powder)) is shown in Table 5. As such, it is 5.0 to 14.0.
Then, the mixed powders 21 to 26 were dried and then press-molded at a pressure of 60 to 120 MPa shown in Table 5 to prepare powder compacts 11 to 16 and sintered under the conditions shown in Table 5. After that, the cermet sintered bodies 11 to 16 shown in Table 5 were prepared by cooling to room temperature.
Next, from the above cermet sintered bodies 11 to 16, TiCN-based cermet tools 11 to 16 (referred to as "comparative example tools 11 to 16") of the comparative example shown in Table 6 having the same shape SNMU140812ANER-M as in the examples were used. Each was manufactured.

With respect to the cermet sintered body constituting the comparative example tools 11 to 16 produced above, the average component composition, the sintered body structure and the porosity were obtained as in the case of the example, and further, cracks were obtained in the sintered body. The appearance and cross section were confirmed with an optical microscope to see if there was any.
The results are shown in Table 6.

Next, with the tools 1 to 6 of the present invention and the tools 11 to 16 of the comparative examples both clamped to the tip of a tool steel cutter having a cutter diameter of 125 mm with a fixing jig, high-speed intermittent cutting of the alloy steel shown below is performed. A dry face milling cutter, which is a type of center cut, was tested.

Cutting test: Dry face milling, center cut cutting,
Cutter diameter: 125 mm,
Work material: JIS / SCM440 Hole material with a width of 100 mm and a length of 400 mm,
Rotation speed: 509 min ^-1 ,
Cutting speed: 200 m / min,
Notch: ae 98mm, ap 2.0mm,
Feed rate (per blade): 0.20 mm / tooth,
In the above-mentioned cutting test, the cutting time until fracture (life) was measured.
The results are shown in Table 7.

As shown in Table 7, the tools 1 to 6 of the present invention have excellent resistance to abnormal damage such as defects, and exhibit excellent wear resistance over a long period of use.
On the other hand, Comparative Examples Tools 11 to 16 are made of a cermet sintered body having insufficient moldability and sinterability, or the aspect ratio of the TiCN hard phase is out of the range specified in the present invention. Therefore, it is clear that the tool life is shortened due to abnormal damage such as chipping.

The TiCN-based cermet cutting tool of the present invention has excellent formability, sinterability, and fracture resistance, and exhibits excellent cutting performance over a long period of use. Therefore, labor saving and energy saving in cutting are further reduced. It is sufficient to cope with the cost reduction.

Claims (1)

In a TiCN-based cermet cutting tool made of a TiCN-based cermet sintered body,
(A) The TiCN-based cermet sintered body is ZrC: 0.5 to 2.0%, WC: 15 to 25%, and the total of one or two of TaC and NbC: 5 to 5% by mass. 20%, total of 1 or 2 of Co and Ni: 12-25%, the balance is an average composition of unavoidable impurities and TiCN (however, Zr, W, Ta and Nb are all carbides. Shows the composition value converted as)
(B) When the cross section of the TiCN-based cermet sintered body is observed with a scanning electron microscope, it has a sintered body structure in which a bonded phase, a first hard phase and a second hard phase are present.
(C) The binding phase is mainly composed of one or two of Co and Ni.
(D) The first hard phase is composed of a single phase of TiCN, and the average contact interface length between the first hard phase and the bonded phase is 50% or more of the grain boundary length of the first hard phase. Yes, the average aspect ratio of the first hard phase is 1.5 or more and 1.8 or less.
(E) The second hard phase is composed of a composite carbonitride of Ti, Zr, W, and one or two of Ta and Nb.
(F) A cutting tool made of TiCN-based cermet, wherein the porosity of the TiCN-based cermet sintered body is A04 or less and B00 defined by the Cemented Carbide Tool Association standard CIS006C-2007.