JP2948945B2 - Particle-dispersed ceramics and cutting tools using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example, iron, nickel,
The present invention relates to a material useful for cutting an alloy such as cobalt or various materials, and a cutting tool using the same.

[0002]

2. Description Related Art Conventionally, aluminum oxide ceramic tool (Al ₂ O ₃₎ is a mainstream, Al ₂ O ₃
Although itself is excellent in abrasion resistance, it is inferior in strength and toughness, and various improvements have been made to eliminate these drawbacks. A typical material is zirconium oxide (Zr) in a matrix composed of Al ₂ O _3.
O ₂ ), silicon carbide (SiC) or titanium carbide (Ti
The material itself has been toughened by dispersing hard particles such as C), but the cutting conditions and the like as tools have become more severe, and the materials for tools have higher strength, higher toughness, and higher wear resistance. Is required.

[0003]

However, even when these hard particle dispersion materials are used, the cutting life of difficult-to-cut materials has a significantly shorter tool life than the case of cutting other materials. May cause destructive wear, and there is a demand for further improvement in wear resistance and fracture resistance as tool performance. In particular, in the hard particle dispersion system, from the viewpoint that the presence of the agglomerated portion of the hard particles themselves is a starting point of destruction and the strength is reduced, it is technically necessary to uniformly disperse the hard particles themselves in the matrix. The point is that various uniform dispersion methods have been proposed, but at present the characteristics have not been improved. Further, a third additive capable of improving the sinterability and the properties has been searched for, but is not a definitive measure.

Accordingly, the present invention provides a hard particle-dispersed ceramic having improved properties such as hardness and toughness, and by using the same, a tool having excellent wear resistance and chipping resistance in cutting hard-to-cut materials. The purpose is to provide.

[0005]

[Means for Solving the Problems] The present inventors have investigated the strengthening mechanism of the hard particle reinforced material, and have repeatedly studied methods for further improving various properties. In-depth examination from the viewpoint that the arrangement in the steel affects the strength and toughness, contrary to the conventional idea of dispersing the hard particles uniformly in the matrix, the hard particles are densely present in the matrix When the areas are scattered, the hardness and toughness are remarkably improved while maintaining a certain level of strength, and when cutting difficult-to-cut materials using this sintered body, destructive wear is prevented and excellent cutting performance Was found to be able to demonstrate.

That is, the particle-dispersed ceramics of the present invention comprises:
A matrix comprising ceramic hard particles dispersedly contained in a matrix, wherein there are a plurality of regions where the hard particles are locally densely present, and these regions are uniformly scattered throughout the matrix. In particular, the matrix component is mainly aluminum oxide, and the ceramic hard particles are at least one selected from carbides, nitrides and carbonitrides of any of silicon and titanium, or oxides of zirconium. Further, a region where the hard particles are densely present exists as a region having a size of 20 μm to 150 μm, and the region has a size of 0.5 μm to 40 μm.
It is characterized by being scattered at intervals of μm.

Hereinafter, the present invention will be described in detail. The particle-dispersed ceramic of the present invention is roughly classified into a matrix component and a hard particle component in terms of composition. When the hard particles are dispersed and contained in the matrix at a ratio of 10 to 50% by volume, particularly 15 to 40% by volume, the hardness and the toughness can be effectively improved. If the content is more than the above, the sinterability of the entire system is reduced, and desired characteristics cannot be obtained. If the content is less than 10% by volume, the strengthening action is reduced due to the addition of the hard particles, and no improvement in the characteristics is observed.

[0008] In such a matrix-ceramic hard particle dispersion system, the toughness and strength are improved as compared with the hard particle-free system because hard particles deflect the crack progression with respect to the crack progression, and the matrix particle It is considered that internal stress is generated in the matrix, thereby suppressing the growth of cracks. In order to exert the above-described effect on the growth of cracks from all directions, hard particles are added to the matrix as shown in FIG. It is important to disperse the particles uniformly and randomly.

On the other hand, the present invention intentionally disperses hard particles unevenly in a matrix, and more specifically, as shown in the schematic diagram of the structure of the particle-dispersed ceramic of the present invention in FIG. In addition, a region A where hard particles are locally and densely present in the matrix is formed, and such regions are scattered in the matrix. The area A where the ceramic hard particles are densely present has an average diameter of 2
It is preferably from 0 μm to 150 μm, particularly preferably from 40 to 100 μm. The areas A are uniformly scattered in the matrix, and the thickness between the areas A is 0.1 mm.
The layers B are arranged so that there is a layer B in which whiskers are sparsely present in an amount of 5 μm to 40 μm, particularly 2 to 30 μm. As a result, a particle-dispersed ceramic tool having less chipping than conventional and having excellent wear resistance can be obtained.

As the matrix component in the particle-dispersed ceramics of the present invention, besides ceramics such as aluminum oxide, silicon nitride, silicon carbide and zirconium oxide, alloys and the like can be used, but from the viewpoint of tool materials, ceramics can be used. Materials are preferred, especially aluminum oxide. In this case, the aluminum oxide has an average crystal grain size of 0.1.
It is desirable to form the matrix as particles having a size of 2 to 10 μm from the viewpoint of enhancing strength and abrasion resistance. On the other hand, the hard particle component is preferably at least one selected from carbides, nitrides, carbonitrides, and oxides of Zr, such as Si and Ti.
It is desirable that the particles are dispersed as particles of 2 to 5.0 μm.

Further, according to the particle-dispersed ceramics of the present invention, oxides, carbides, and the like of the elements of Group 3a of the periodic table such as Y, Yb, Er, Dy, Sc, and Ce for such a system.
In addition to nitrides and borides, MgO, CaO, SiO ₂ , Ti
By adding an oxide such as O ₂ or Al ₁₈ B ₄ O _{33, the} sinterability of the system can be improved, and B ₄ C, carbides of elements of groups 4a, 5a and 6a of the periodic table, and nitrides can be improved. It is of course possible to improve properties such as strength and toughness by adding materials, carbonitrides, borides and the like. It is desirable that these additives be added at a ratio of 5 to 30% by weight based on the total amount.

According to a conventional method, a matrix material such as Al ₂ O ₃ and hard particles are thoroughly mixed in a liquid, dried, and then hot-pressed. Baking, relative density 95%
The above-described method for obtaining a high-density body is employed. On the other hand, according to the method of the present invention, the raw material of Al ₂ O _{3 and the} raw material of hard particles, and other additives as necessary, are prepared at a desired mixing ratio, and this is thoroughly mixed with a solvent by a known method. After preparing the slurry, the slurry is dried by spray drying to prepare a powder having an average particle size of about 20 to 150 μm.

According to the present invention, by controlling various conditions in the spray drying, an agglomerated portion in which hard particles are densely formed is formed at the center of the powder, and the hard particles are sparsely formed around the agglomerated portion. To form a powder having a surface layer portion in which a large amount of matrix components are present.

Specifically, the slurry viscosity after blending is set to 1.
It is necessary to control the pressure to 0 poise or less, particularly 0.8 poise or less. If it is higher than 1.0 poise, it becomes difficult to form an agglomerated portion where hard particles are densely present and a surface layer portion where hard particles are sparsely present. The hot air temperature in the spray-dry is 80 ° C ~
The temperature is 200 ° C., preferably 100 ° C. to 180 ° C. In this case, if the inlet temperature is higher than the outlet temperature, the above-described desirable structure is likely to be formed. Atomizer-rotation speed is 5
5,000 rpm to 15,000 rpm, preferably 8,000 rpm to 10,000 rpm, and the diameter of the aggregated portion is 2
It tends to be 0 μm to 150 μm. If it is lower than 5000 rpm, the diameter of the aggregated portion tends to be large, and if it is higher than 15000 rpm, the diameter tends to be small. As described above, the diameter of the agglomerated portion and the thickness of the surface portion can be controlled by the conditions of the composition, the amount of the hard particles, the slurry concentration, and the spray-dry condition.

Next, after removing coarse particles from the powder obtained as described above by a mesh pass, the powder is directly hot-pressed or formed into a predetermined shape by a known molding method. Then, hot press firing is performed. The firing is performed at 350 kg / cm ² in a reducing atmosphere containing vacuum, an inert gas such as Ar or N _2, or carbon.
By applying the above pressure and firing at a temperature of 1400 ° C. to 1800 ° C. for about 0.5 to 12 hours, a relative density of 99 is obtained.
% Or more. As another firing method, a relative density of 9 to 1400 ° C. to 1800 ° C. in the above vacuum or inert gas or a reducing atmosphere is used.
After firing to 5% or more, 1350 ° C in an inert atmosphere
Hot densification at 1750 ° C. can further increase the density.

[0016]

According to the conventional particle-dispersed ceramics, when the tip of the crack reaches hard particles uniformly dispersed in the matrix, the crack is deflected, and the energy of the crack gradually disappears due to the repetition, so that the progress of the crack is stopped. In addition, according to the ceramics of the present invention, the hard particles are non-uniformly dispersed with respect to the uniform dispersion type as described above. The structure in which regions where hard particles are densely present in the ceramics are scattered in the matrix can dramatically increase strength and toughness.

Considering the reason for this, the crack tip easily progresses in the matrix, but when it reaches a region where the hard particles dispersed in the matrix are densely located, the crack is hardly affected by the action of the high-density hard particles. It can be considered that the energy of the cracks can be abruptly eliminated as compared with the uniform dispersion type, so that the cracks cannot further develop in the region A.

Thus, for example, when the ceramic of the present invention is used as a cutting tool, it is possible to effectively prevent destructive wear and chipping accompanying crack propagation in cutting of difficult-to-cut materials.

[0019]

EXAMPLE An Al ₂ O ₃ powder (average particle size 0.2 μm),
Hard particles (average particle size: 0.3 to 1.0 μm) of SiC, TiCN, TiN, TiC, and ZrO ₂ were weighed in the proportions shown in Table 1, and thoroughly mixed with a nylon ball using water as a solvent. A slurry was prepared. Next, the slurry was adjusted to have a viscosity of 1.0 poise or less, and the inlet temperature was adjusted to 150 poise.
° C, outlet temperature 120 ° C and atomizer rotation speed 1000
Spray-drying was performed at 0 rpm to produce a granulated powder having an average particle size of 60 μm.

Thereafter, the compact obtained by press-molding into a tool shape RNGN120416 was hot-pressed at 1400 to 1800 ° C. under a pressure of 350 kg / cm ² to produce a sintered body having a relative density of 99% or more. Further, as a comparative example, a mixture obtained by uniformly mixing a mixture in a ball mill with the same composition system was press-molded in the same manner, and a pressure of 35%.
It was baked at 1400-1800 ° C. for 1 hour at 0 kg / cm ² and baked to prepare a comparative sintered body.

With respect to each of the obtained sintered bodies, the size of the hard particle aggregation region and the thickness of the layer where the hard particles were sparse were measured at several points by an electron microscope photograph, and the average value was obtained. Further, the sintered body was measured for flexural strength and toughness by the IF method based on JISR1601, respectively, and Vickers hardness was measured. Furthermore, using Inconel 718 as a work material, a cutting speed of 300 m / min, and a cutting depth of 1.0 mm /
A cutting test was performed under cutting conditions of rev and feed of 0.1 mm, and the time until chipping of the tool and the amount of flank wear after cutting for 2 minutes were measured. The results are shown in Table 2.

[0022]

[Table 1]

[0023]

[Table 2]

As apparent from the results in Tables 1 and 2, Sample N in which hard particles were uniformly dispersed in a matrix was used.
In contrast to o, 9 to 16, samples No. 1 to 8 in which hard particles were partially agglomerated showed improved hardness and toughness, and the present invention was applied to the cutting of difficult-to-cut materials as tools. The product has a longer life than the conventional product.

[0025]

As described in detail above, the particle-dispersed ceramic of the present invention has high hardness and high toughness, and can prevent chipping during cutting even in difficult-to-cut materials such as Inconel. Therefore, cutting stability with respect to the tool life can be provided, and the tool life can be extended.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the structure of a particle-dispersed ceramic of the present invention.

FIG. 2 is a schematic view showing a composition structure of a conventional particle-dispersed ceramic.

[Explanation of symbols]

 A Region where particles are densely present B Region where particles are sparsely present

Claims (5)

(57) [Claims] 1. A particle-dispersed ceramic in which ceramic hard particles are dispersed and contained in a matrix, wherein an agglomerated region in which the hard particles are densely present is scattered in the matrix. . 2. The particle dispersion according to claim 1, wherein the matrix component is mainly composed of aluminum oxide, and the ceramic hard particles are at least one selected from carbides, nitrides, carbonitrides and oxides of Zr and Ti. Ceramics. 3. The method according to claim 2, wherein the aggregation region is in the matrix.
The particle-dispersed ceramic according to claim 1, which is present in a size of 0 µm to 150 µm. 4. The method according to claim 1, wherein the aggregation region has a thickness of 0.5 μm to 40 μm.
The particle-dispersed ceramic according to claim 1, which is scattered in the matrix at intervals of m. 5. A cutting tool comprising a particle-dispersed ceramic in which ceramic hard particles are dispersedly contained in a matrix, wherein regions in which the hard particles are densely scattered are scattered in the matrix.