JP2003200307A - Titanium carbide group ceramics tool and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem wherein titanium carbide group sintered body making a grain boundary phase of Al<SB>2</SB>O<SB>3</SB>, etc., exist in a conventional TiC grain boundary and aluminium oxide group sintered body making a dispersion phase of TiC, etc., within conventional Al<SB>2</SB>O<SB>3</SB>have insufficient wear resistance, fracture resistance and chipping resistance at the time of a cutting. <P>SOLUTION: Hardness, strength and toughness are improved by uniformly/ finely dispersing fine particles of oxide and boride, etc., within crystal grain of a main phase mainly made of titanium carbide in the titanium carbide group sintered body. As a result, an effect in which wear resistance, fracture resistance and chipping resistance at the time of the cutting are remarkably excellent and a tool service life is improved by twice to five times can be obtained. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium carbide based ceramics tool in which fine particles of alumina, rare earth oxide, titanium boride and the like are dispersed in crystal grains of a titanium carbide sintered body.

[0002]

2. Description of the Related Art Alumina type, alumina-titanium carbide type,
Ceramic tools typified by silicon nitride are effective in high-speed cutting, but are low in strength and toughness, so they are easily damaged and lack reliability. As one method for simultaneously improving hardness and toughness, there is a nanocomposite material in which ultrafine particles of another component are dispersed and strengthened in matrix particles. This is because the dispersion strengthening improves the hardness, and the addition of a stress field in the matrix particles suppresses the development of fracture cracks, thereby improving the toughness.

Although many proposals have been made regarding nanocomposite materials, as typical examples of prior art relating to cutting tools, JP-A-02-229756 and JP-A-02-229757 disclose titanium-based boride-based alumina-based materials. JP-A-07-89765 and JP-A-07-1091
No. 74 publication and the like. The form of dispersed particles is described in JP-A-07-82047.

[0004]

Among typical examples of alumina-based materials, Japanese Unexamined Patent Publication No. 2-229757 discloses 0.5.
A ceramic composite material in which TiN fine particles having a particle diameter of 20 μm or less are dispersed in the crystal grains of an Al ₂ O ₃ matrix having crystal grains of ˜100 μm is also disclosed in JP-A-2-229.
No. 757, a grain size of 20 μm is contained in a grain of an Al ₂ O ₃ matrix having crystal grains of 0.5 to 100 μm.
The following describes a ceramic composite material in which TiC fine particles are dispersed.

In the ceramic composite materials described in these publications, the strength is not improved as compared with the conventional aluminum oxide based sintered body in which TiN or TiC is present as the grain boundary phase of the Al ₂ O ₃ matrix. However, when used for intermittent cutting of steel, high speed cutting of castings, heat resistant alloys, etc., there is a problem that chipping, chipping and boundary wear easily occur due to insufficient strength and toughness. Especially in high-speed turning of ductile cast iron, inoculant components of ductile cast iron and Al ₂ O ₃
There is a problem that the flank wear due to the reaction with the matrix becomes remarkable.

Among the typical examples of titanium boride-based materials, Japanese Unexamined Patent Publication (Kokai) No. 07-089765 discloses a boride of Group 4a having a crystal grain of 0.3 to 5 μm. A ceramic material for a cutting tool, in which 3 to 30% by volume of SiC fine particles of 500 nm or less are dispersed, and similarly, Japanese Patent Laid-Open No. 07-109174 discloses a particle size of 50.
A boride-based ceramic composite material in which 3 to 20% by volume of Group 6a metal fine particles having a size of 0 nm or less are dispersed is described.

The boride-based ceramics described in these publications are effective in cutting aluminum alloys because they are excellent in welding resistance to aluminum and high-temperature characteristics, but they easily react with iron-based materials, so steels and castings. However, there is a problem that wear is remarkable in high-speed cutting of heat-resistant alloys.

The morphology of dispersed particles is disclosed in Japanese Patent Application Laid-Open No. 07-107
-82047 discloses that spherical particles of a nanometer size different from the matrix are contained in the particles of the crystal particles of the matrix, and plate-like particles (having a diameter of 5 to 30 μm and a thickness of 5 to 30 μm, different from the matrix, at the crystal grain boundaries. Is 6 μm or less), and a ceramic composite in which 0.5 to 20% by volume of the whole is dispersed is described. Matrix, spherical particles, plate-shaped particles are A
_{l 3 O 3, ZrO 2,} Si 3 N 4, SiC, a combination of AlN.

The ceramic composite described in the publication has improved toughness and high temperature characteristics due to the synergistic effect of dispersion of nanoparticles in matrix particles and dispersion of plate-like particles at grain boundaries. When used, there is a problem that the abrasion resistance is insufficient in any matrix.

The present invention has solved the above-mentioned problems. Specifically, in a sintered body containing titanium carbide as a main component, which is superior in hardness and toughness to alumina, titanium carbide crystal particles are present. Disclosed are dispersed phase particles such as alumina, rare earth oxides, titanium boride and the like in and inside grain boundaries to provide a ceramic for a cutting tool that exhibits a long life in high speed cutting of various work materials.

[0011]

The inventors of the present invention have studied the improvement of tool life and reliability when using titanium carbide based ceramics as a cutting tool. By dispersing the substance, the hardness, strength and toughness are improved, and by adjusting the type, content and particle size of different substances, when used as a cutting tool, crater wear resistance, flank wear resistance and toughness can be improved. The present invention has been completed based on the finding that it can be increased, and that the performance improving effect is remarkable particularly in high-speed cutting of ductile cast iron.

That is, the titanium carbide based ceramics tool of the present invention comprises titanium carbide as a main phase and magnesium, aluminum, titanium, zirconium, hafnium, yttrium, oxides of rare earth metal elements, borides and titanium boron. Compound, an iron group metal, and at least one disperse phase selected from these solid solutions, and the disperse phase is present in the crystal grains of the main phase and at the crystal grain boundaries.
It is characterized by being contained in an amount of up to 30% by volume.

Carbonization in the ceramic tool of the present invention
The main phase whose main component is tongue is (Ti _1-AM_A) (C_1-xy
N_xO_y)_z[However, M is 4 in the periodic table excluding titanium
a, 5a, 6a group element, 0 ≦ A ≦ 0.3, 0 ≦ X
≦ 0.3, 0 ≦ Y ≦ 0.1, 0.8 ≦ Z ≦ 1.1]
To be done. For titanium carbide, part of titanium is replaced with M
Then the hardness and strength are improved and the abrasion resistance and chip resistance are improved.
Pinging property is improved, which is preferable.
Alternatively, substituting with oxygen increases chemical stability and
It is preferable because it improves the starting property.

The average crystal grain size of the main phase is 1 μm.
When it is less than 10, the crystal grains of the dispersed phase are less likely to be taken into the crystal grains of the main phase due to grain growth during sintering, so that the dispersion effect is small, and when it exceeds 10 μm, the strength of the sintered body remarkably decreases.

The dispersed phase in the ceramic tool of the present invention is specifically MgO, Al ₂ O ₃ , ZrO ₂ , Hf.
_{O 2, Y 2 O 3,} La 2 O 3, CeO 2, Yb 2 O 3, Al
B ₁₂ , TiB ₂ , ZrB ₂ , HfB ₂ , LaB _{5 and the} like can be mentioned, and among these, MgO, Al ₂ O ₃ , Y ₂
It is preferable to use at least one of O ₃ , CeO ₂ , TiB ₂ , ZrB ₂ , and HfB ₂ because it is easily available and has high temperature stability and excellent wear resistance during cutting.

The average crystal grain size of the dispersed phase particles is
If it is less than 0.01 μm, it is difficult to manufacture because it grows during sintering, and if it exceeds 5 μm, it is difficult to be incorporated into the crystal grains of the main phase.

When the added amount of the dispersed phase in the ceramics tool of the present invention is less than 1% by volume, hardness, strength, toughness, crater wear resistance, and flank resistance are obtained even if all the particles are dispersed in the crystal grains of the main phase. The effect of improving the wear resistance and toughness is small, and when it exceeds 30% by volume, the amount of the main phase relatively decreases and the wear in cutting steel and ductile cast iron increases conversely.

Further, the dispersed form of the dispersed phase is such that it is dispersed in both the crystal grains of the main phase and the crystal grain boundaries, and the fine particles of the dispersed phase are dispersed in the crystal grains of the main phase. Coarse grains exist in the grain boundaries of the main phase.
When 10 to 95% by volume of the dispersed phase is uniformly dispersed in the crystal grains of the main phase, the effect of improving various properties can be exhibited. Here, the added amount of the dispersed phase is 5 with respect to the entire ceramic tool.
10 to 10% by volume, and most preferably 30 to 95% by volume of the dispersed phase is dispersed in the crystal grains of the main phase.

In the ceramic tool of the present invention, if 5% by volume or less of the iron group metal exists as a dispersed phase in the crystal grains of the main phase and in the crystal grain boundaries, the toughness of the sintered body is further enhanced, and the fracture resistance and the resistance to fracture are improved. It is preferable because the chipping property is improved. However, when the iron group metal is present in an amount exceeding 5% by volume, plastic deformation and abnormal wear of the cutting edge occur during high speed cutting. In addition, when the sintering temperature is low, there is little solid solution of the main phase in the iron group metal,
When the sintering temperature is high, the solid solution of the main phase in the iron group metal increases, but the effect is the same.

In the ceramic tool of the present invention, it is sometimes preferable that the material near the surface is a graded material because the wear resistance or the chipping resistance is improved depending on the cutting conditions. Specifically, the graded structure in which the average crystal grain size of the main phase gradually increases or decreases from the surface of the sintered body toward the inside of 0.01 to 1.0 mm, and the iron group metal is the surface of the sintered body From 0.01 to 1.0 mm, a graded composition gradually increasing toward the inside can be mentioned.

The method of manufacturing a ceramics tool of the present invention comprises:
The method is the same as that for a normal ceramics sintered body. That is, various raw material powders are mixed and pulverized, and a green compact obtained by pressure molding is sintered at a temperature of 1400 to 2000 ° C. in a non-oxidizing atmosphere. The average particle diameter of the powder of the main phase used is 2 μm from the viewpoint of sinterability, dispersibility, and dispersion effect.
The average particle size of the dispersed phase powder to be added is 0.5 μm.
The following are preferred: Also, 4a, 5 added as the case may be
It is also preferable that the carbide, nitride and oxide powders of the a and 6a group elements or the metal and oxide powders of the iron group element are 1 μm or less.
Further, as the sintering atmosphere, for example, if argon is used, a sinterability is good and a uniform sintered body is used. If nitrogen or carbon monoxide is used, the surface is nitrided or carburized to obtain a sintered body having a gradient structure / composition. can get.

The method of manufacturing a ceramic tool according to the present invention comprises:
Generally, titanium carbide powder is mixed with ultrafine dispersed particles and sintered, but MgO, Al ₂ O ₃ , Y
_When oxide-based compound particles such as ₂ O ₃ are dispersed, use of a composite oxide powder composed of TiO ₂ and these oxides causes a large amount of uniform and fine compound particles in the titanium carbide crystal particles. It is preferable because it is incorporated. Specifically, MgTiO ₃ , Al ₂ TiO ₅ , Y ₂ TiO ₅ , CeT
A composite oxide powder such as i ₂ O ₆ , Nd ₂ TiO ₅ , and NiTiO ₃ and a carbon powder (TiC conversion by reduction / carbonization of TiO ₂ ) are used. Since titanium is produced at the same time, it is easily incorporated into the titanium carbide crystal without grain growth.

[0023]

Example 1 First, Al having an average particle size of 0.05 μm
₂ O ₃ , 0.02 μm MgO, 0.15 μm Y ₂ O ₃ ,
0.2 μm CeO ₂ , 0.12 μm NiO, 0.0
Each powder of ₂ μm TiO ₂ was added to the composition shown in Table 1,
After wet mixing for 24 hours using an ethyl alcohol solvent, a urethane-lined pot, and an alumina crushing ball and drying, the mixed powder was put in an alumina crucible and heated at 1000 ° C. for 30 minutes in an atmospheric furnace. Heat treatment was performed.
Furthermore, crushing was performed for 72 hours with the balls of the above method.
Table 1 shows the results of identification of the obtained composite oxide powder by X-ray diffraction and the measurement results of the average particle diameter by a scanning electron microscope.

[0024]

[Table 1]

Next, the obtained AT, MT, YT, CT,
Each composite oxide of NT and the above Al ₂O₃, NiO and flat
TiC with an average particle size of 0.5 μm, ZrB of 0.2 μm₂，
0.02 μm carbon black (hereinafter referred to as C), 1.
0 μm Mo₂C, 0.5 μm TiN, 0.5 μm
Powder of WC, 1.0 μm NbC, 1.1 μm VC
Was added to the composition shown in Table 2 to obtain ethyl alcohol.
Solvent, urethane lined pot, alumina crush
Wet the mixture for 48 hours with a ball and dry it.
While adding 0.2 wt% paraffin wax
A mixed powder was obtained. The mold is filled with these powders, and 196
Powder compact of about 5.5 x 17 x 43 mm with a pressure of MPa
Create a compact and place it on a boron nitride setter
After heating up to 1400 ° C. in a vacuum of about 50 Pa, Table 2
Heated and maintained for 1 hour at the specified temperature in the atmosphere described in
As a result, the products of the present invention products 1 to 10 and comparative products 1 to 7
A mixed sintered body was obtained. In addition, all ceramics sintering
For the body, 1650 ° C in argon at 150 MPa for 1 hour
A HIP treatment in between was applied after sintering.

[0026]

[Table 2]

The ceramics sintered body thus obtained was cut into a rod shape with a diamond cutter, and wet-ground with a # 230 diamond grindstone to obtain 3.0 × 4.0 × 35.0 m.
After making the JIS test piece of m, the bending strength was measured. The results are shown in Table 3. In addition, one surface of the sample is 0.3 μm
After lapping with the diamond paste of No. 1, the hardness and fracture toughness value K1C (IM method) at a load of 9.8 N using a Vickers indenter were measured, and the results are also shown in Table 3.

[0028]

[Table 3]

Further, a photograph of the structure of the lapped surface of each sample was taken with an electron microscope, the average grain size of the main phase (denoted as TiC phase) was determined using an image processing apparatus, and the results are also shown in Table 3. . Further, the components of the dispersed phase particles existing in the crystal grains of the main phase and in the crystal grain boundaries, the average particle diameter, the volume ratio,
The ratio of the dispersed phase existing within the crystal grains of the main phase was determined.
The results are shown in Table 4.

[0030]

[Table 4] * Proportion in particles in Table 4 = A / (A + B) x 100 (%)

[0031]

[Example 2] Using the mixed powders of the present invention 1 to 10 and Comparatives 1 to 7 obtained in Example 1, SN described in the ISO standard
With a mold for GN120408 shape, SNGN120408 shape (0.1 × −25 °) was obtained by press molding, heat sintering and wet grinding under the same method and conditions as in Example 1.
Of the cutting tool) was produced.

Work material: FCD600, cutting speed: 300 m / min, depth of cut: 1.0 mm, feed:
A 0.2 mm / rev dry type outer circumference continuous turning test was performed, and the time until the end of the life was obtained, and the results are shown in Table 5. The average flank wear amount (V
The life was defined as when B) was 0.3 mm or more, or when chipping or chipping occurred.

Work Material: Chilled Roll (HRC = 6
0), cutting speed: 100m / min, depth of cut: 0.5m
m, feed: a dry turning test was conducted under the condition of 0.1 mm / rev, and the life time until the defect width or the average flank wear width became 0.25 mm was similarly obtained. The results are also shown in Table 5.

[0034]

[Table 5]

[0035]

EFFECTS OF THE INVENTION The titanium carbide based ceramics tool of the present invention has an action of improving wear resistance during high speed cutting of titanium, cast iron (especially ductile cast iron), heat-resistant alloys, etc. whose main phase is titanium carbide. The particles of the dispersed phase, such as oxides and borides, which are uniformly and finely dispersed in the crystal grains of the main phase, act to improve hardness, strength, and toughness by the nano-dispersion effect. The particles of the dispersed phase dispersed in the boundary serve to disperse and strengthen the entire ceramic tool. Due to such an action, the titanium carbide based ceramics tool of the present invention exerts an excellent effect in improving wear resistance, chipping resistance and chipping resistance during cutting.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3C046 FF33 FF42 FF49 FF51                 4G001 BA01 BA03 BA06 BA14 BA24                       BA25 BA41 BA44 BA53 BA60                       BA61 BB03 BB05 BB08 BB14                       BB24 BB25 BB41 BB44 BB53                       BB61 BD12 BD13 BD18 BE22                       BE26

Claims (6)

[Claims] 1. At least one selected from magnesium, aluminum, zirconium, hafnium, yttrium, lanthanum rare earth oxides, borides, titanium borides, iron group metals, and solid solutions thereof. 1 to 30% by volume of the dispersed phase and the balance (Ti _1-A M _A )
(C _1-xy N _x O _y ) _z [where M is a 4a, 5a, 6a group element of the periodic table excluding titanium, 0 ≦ A ≦ 0.3, 0 ≦ X
≦ 0.3, 0 ≦ Y ≦ 0.1, 0.8 ≦ Z ≦ 1.1] in the sintered body, the particles of the dispersed phase are It exists in the crystal grains and in the crystal grain boundaries, and the ratio of the existence in the crystal grains is 10 to 9 of the dispersed phase.
Titanium carbide based ceramics tool characterized by being 5%. 2. The titanium carbide based ceramics tool according to claim 1, wherein the iron group metal is 5% by volume or less of the sintered body. 3. The average crystal grain size of the main phase is 1 to 10.
The titanium carbide based ceramics tool according to any one of claims 1 to 2, wherein the titanium carbide based ceramics tool has a thickness of µm. 4. The average crystal grain size of the dispersed phase is 0.01
The titanium carbide based ceramics tool according to any one of claims 1 to 3, characterized in that 5. The dispersed phase comprises at least one selected from magnesium oxide, aluminum oxide, yttrium oxide, cerium oxide, titanium boride, zirconium boride, hafnium boride, and solid solutions thereof. The titanium carbide based ceramics tool according to any one of claims 1 to 4. 6. A titanium carbide powder, a composite oxide powder consisting of titanium oxide and at least one oxide selected from magnesium, aluminum, zirconium, hafnium, yttrium and lanthanum rare earth metal elements, and a carbon powder. , 4a, 5a, 6 excluding titanium in some cases
Mixing and crushing carbide, nitride, oxide, boride powder of group a element or metal, oxide powder of group iron element,
1400 the green compact obtained by pressure molding in a non-oxidizing atmosphere
A method for manufacturing a titanium carbide based ceramics tool, which comprises sintering at a temperature of up to 2000 ° C.