JPH10182230A - High strength sintered compact and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high strength sintered compact having heat and wear resistances and a fine homogeneous texture and useful as stock for a cutting or grinding tool by blending diamond particles with a prescribed amt. of a sintering aid made of a compd. contg. yttrium, an iron family metal and oxygen. SOLUTION: Diamond particles having <=10μm average particle diameter are blended with 0.1-30vol.% sintering aid based on the total amt. A mixture of yttrium oxide such as y2 O3 with oxide of an iron family metal such as Fe2 O3 or a multiple oxide such as Fe2 Y2 O6 is used as the sintering aid and the particle diameter of the sintering aid is preferably 0.01-10μm. For example, 95vol.% natural diamond powder having 3-8μm particle diameter is blended with 5vol.% YFeO having about 1μm particle diameter as a sintering aid and the resultant mixture is filled into an Mo capsule and sintered by holding at 1,750 deg.C under 6.5GPa pressure for 15min with a belt type ultrahigh pressure and high temp. generator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a diamond sintered body and a method for producing the same. The diamond sintered body of the present invention can be effectively used as a material for cutting and grinding tools for non-ferrous metals and ceramics.

[0002]

2. Description of the Related Art As conventional diamond sintered bodies, there have been known those using iron group metals such as Co, Ni and Fe as sintering aids or binders, and those using ceramics such as SiC. It is used for cutting tools. Further, those using a carbonate as a sintering aid are also known (JP-A-4-74766, JP-A-4-11).
No. 4966). In addition, there is a natural diamond sintered body (carbonado), but the material varies greatly,
Also, since the amount of production is very small, it is hardly used industrially.

[0003]

A diamond sintered body using an iron group metal such as Co as a sintering aid has poor heat resistance because the iron group metal such as Co acts as a catalyst for promoting the graphitization of diamond. . That is, in an inert gas atmosphere,
It is graphitized at about 700 ° C. In addition, since a metal such as Co exists as a continuous phase at the grain boundaries of diamond grains, the strength of the sintered body is not very high, and when used as a cutting tool, the cutting edge is likely to be broken. And, when used as a cutting tool due to the difference in thermal expansion between this metal and diamond,
There is also a problem that the cutting edge is thermally deteriorated, and chipping and wear are likely to occur. It is also known that the above-mentioned metal at the grain boundary is removed by an acid treatment in order to increase heat resistance. As a result, the heat resistance temperature is increased to about 1200 ° C., but the strength is greatly reduced (about 30%) because the sintered body becomes porous.

Further, when a metal catalyst such as Co is used as a sintering aid, diamond particles are liable to grow abnormally when sintering fine diamond powder, and are required for cutting tools requiring a fine and homogeneous structure. As a big problem. Further, although a diamond sintered body using SiC as a binder is excellent in heat resistance, the strength is low because diamond particles do not bond with each other. On the other hand, a diamond sintered body using a carbonate as a sintering aid has better heat resistance than a sintered body made of a Co binder, but the decomposition of the carbonate starts at about 1000 ° C. and the strength of the sintered body is reduced. descend. Further, in the method using a carbonate as a sintering aid, the production of a diamond sintered body requires extremely severe pressure and temperature conditions of 7.7 GPa and 2000 ° C. or higher, so that the cost becomes considerably high,
Industrial production is difficult. The present invention solves the above problems,
Provided is a fine and uniform diamond sintered body having chipping resistance, wear resistance, and heat resistance, which is effective as a cutting tool, and a method for producing the diamond sintered body at low cost under conditions that enable industrial production. The purpose is to:

[0005]

Means for Solving the Problems As means for solving the above-mentioned problems, (1) a substance comprising a compound containing yttrium, an iron group metal and oxygen is contained in an amount of 0.1 to 30% by volume, and the balance is average particle size. A high-strength sintered body composed of diamond particles having a diameter of 10 μm or less,

(2) The high-strength sintered body according to the above (1), wherein the compound containing yttrium, iron group metal and oxygen is a complex oxide or solid solution comprising yttrium oxide and iron group metal oxide. ,

(3) A mixture or a composite oxide of yttrium oxide and an iron group metal oxide is used as a sintering aid, and this powder and diamond powder having an average particle size of 10 μm or less, or an average particle size of 10 μm The following (1) or (2), wherein the following diamond powder and a mixed powder of non-diamond carbon are mixed, and the mixture is held under pressure and temperature conditions in a thermodynamically stable region of diamond and sintered. Method for producing a high-strength sintered body according to

(4) A mixture of yttrium oxide and an oxide of an iron group metal or a complex oxide is used as a sintering aid, and a compact of this powder and a compact of diamond powder having an average particle diameter of 10 μm or less or an average of A diamond powder having a particle size of 10 μm or less is laminated with a molded product of a mixed powder of non-diamond carbon, and this is subjected to pressure in a thermodynamically stable region of diamond,
The method for producing a high-strength sintered body according to the above (1) or (2), wherein the method is held at a temperature condition and sintered.

(5) A composite oxide or a mixture of yttrium oxide and an iron group metal is formed on the surface of diamond powder having an average particle diameter of 10 μm, and this is held under the pressure and temperature conditions in the thermodynamically stable region of diamond. The method for producing a high-strength sintered body according to the above (1) or (2), wherein the method comprises sintering.

(6) A molded body of diamond powder in which yttrium oxide is formed on the surface of diamond powder having an average particle diameter of 10 μm and a molded body of oxide of iron group metal are laminated.
The method for producing a high-strength sintered body according to the above (1) or (2), wherein the method is held and sintered under the pressure and temperature conditions of the thermodynamically stable region of diamond. (7) A compact of diamond powder in which an oxide of an iron group metal is formed on the surface of diamond powder having an average particle diameter of 10 μm or less and a compact of yttrium oxide are laminated, and this is formed into a thermodynamically stable region of diamond. The method for producing a high-strength sintered body according to the above (1) or (2), wherein the method is held under pressure and temperature conditions and sintered. In the above production methods (3) to (7), the sintering aid is blended so as to be 0.1 to 30% by volume in the mixture.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Heretofore, there has been no example in which a composite oxide of yttrium oxide and an oxide of an iron group metal or a mixture thereof has been used as an effective sintering aid for a diamond sintered body. Now, the present inventors use these composite oxides and mixtures as sintering aids and sinter diamond powder having an average particle size of 10 μm or less, thereby achieving unprecedented high strength, abrasion resistance, It has been newly found that diamond sinters for cutting tools excellent in chipping properties and heat resistance can be obtained under lower pressure and temperature conditions than when a conventional non-metallic catalyst is used as a sintering aid. .

That is, a feature of the present invention is that yttrium oxide (Y ₂ O ₃ ) is used as a sintering aid for a diamond sintered body.
And oxides of iron group metals (FeO, Fe ₂ O ₃ , CoO, C
o ₃ O ₄ , NiO, CoFe ₂ O ₄ ) or a mixture thereof, and diamond having an average particle diameter of 10 μm or less is used as a raw material. These composite oxides or mixtures of yttrium oxide and iron group metal oxides show a strong catalytic action on diamond, and when they are used as sintering aids, a matrix is formed in which diamond particles are very strongly bonded. . Further, even if a very fine diamond powder of about 1 μm is used as a raw material, abnormal grain growth hardly occurs, and a sintered body having a uniform structure can be obtained. Such a sintering aid preferably has a particle size range of 0.01 to 10 μm. Further, the catalysis of these composite oxides and mixtures occurs at a temperature about 500 ° C. lower than that of the carbonate catalyst.
For this reason, when these composite oxides and mixtures are used as sintering aids, they have a low temperature catalytic action (sintering is possible).
Under such mild conditions as 5 GPa and 1700 ° C., a sintered body having the above-mentioned strength and excellent heat resistance can be obtained. That is, an unprecedented high-strength diamond sintered compact for cutting tools having excellent wear resistance and heat resistance can be obtained under conditions that facilitate industrial production.

The diamond sintered body thus obtained is
It is characterized by having a fine and homogeneous structure, including a substance composed of a compound containing yttrium, an iron group metal and oxygen. Examples of the compound containing yttrium, an iron group metal, and oxygen include a composite oxide of an oxide of yttrium and an iron group metal (eg, Fe ₂ Y ₂ O ₆ , Y ₃ Fe ₅ O ₁₂ ).
Is mentioned. Such a substance is stable even at a high temperature exceeding 1000 ° C., and therefore, the diamond sintered body of the present invention exhibits excellent heat resistance. In addition, since it is a sintered body with a fine and homogeneous structure, an extremely sharp cutting edge is obtained,
It is particularly effective as a cutting tool.

In the diamond sintered body of the present invention, the content of a substance comprising a compound containing yttrium, an iron group metal and oxygen is preferably 0.1 to 30% by volume, particularly preferably 1 to 20% by volume. If less than 0.1% by volume, the bonding between diamond particles, that is, the sinterability is reduced,
If the content exceeds 30% by volume, the strength and the abrasion resistance decrease due to the influence of the excess compound. Further, the diamond constituting the sintered body preferably has an average particle diameter of 10 μm or less. When the average particle size exceeds 10 μm, a sharp edge cannot be obtained, and the edge is liable to be broken.

As a raw material of diamond, synthetic diamond powder, natural diamond powder, polycrystalline diamond powder and the like can be used. The particle size of the powder is 0.01
Depending on the application, a particle having a particle size of about 20 μm or fine or coarse, or a mixture of fine and coarse particles is used. Also,
Raw materials obtained by adding non-diamonds such as graphite, glassy carbon, and pyrolytic graphite to these diamonds in an appropriate amount can also be used. Also, a mixture of diamond and these non-diamond graphites can be used.

In the method for producing a diamond sintered body of the present invention, a diamond powder and a composite oxide or a mixture of yttrium and an iron group metal oxide are prepared under the conditions of pressure and temperature under which diamond is thermodynamically stable. There is a method in which a molded body of diamond powder and a molded body of a composite oxide or a mixture of an oxide of yttrium and an iron-group metal or a molded body of a mixture are stacked as raw materials under the above-described pressure and temperature conditions. . Further, by forming a complex oxide or a mixture of an oxide of yttrium and an iron group metal on the surface of the raw material diamond powder in advance by a thermal plasma method or the like, and sintering the mixture under the above pressure and temperature conditions, A more homogeneous sintered body is obtained. Also, it is possible to form yttrium oxide on the surface of the raw material diamond powder, and to sinter the compact of the powder and the compact of the oxide of iron group metal under the above pressure and temperature conditions. Conversely, a compact obtained by forming an oxide of an iron group metal on the surface of diamond powder and laminating a compact of yttrium oxide may be sintered under the above-described pressure and temperature conditions.

[0017]

【Example】

Example 1 Y ₃ Fe _{5 having a} particle size of about 1 μm was used as a sintering aid.
O ₁₂ was used. Natural diamond powder having a particle size of 3 to 8 μm (average 5 μm) and Y ₃ Fe ₅ O ₁₂
The mixture was sufficiently mixed at a ratio of 5% by volume to 5% by volume, and the mixture was placed in a Mo capsule.
Hold for 5 minutes and sinter. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 5% by volume of a composite oxide of yttrium and iron was detected in addition to diamond. Further, when the structure was observed with a scanning microscope, it was found that the structure had a dense structure in which diamond particles having a uniform particle diameter of 5 μm were combined, and no abnormal grain growth was observed. When the hardness of this sintered body was evaluated using a Knoop indenter, it was as high as 8300 Kg / mm ² . After the sintered body was heated to 1200 ° C. in a vacuum, the hardness was measured. When a cutting edge for a cutting tool was prepared from this diamond sintered body, an extremely sharp cutting edge was obtained. This was vacuum brazed to a hard metal base using an active brazing material to produce a cutting tool, and the Al-Si alloy was intermittently cut. As a comparative material, a cutting performance was compared under the same conditions using a diamond sintered body having a mean particle size of 5 μm using a conventional Co binder. The wear amount of the flank was 1/5 of that of the conventional diamond sintered body made of the Co binder, and almost no cutting edge was found, indicating excellent cutting performance.

Example 2 5% by volume of Y ₂ F was added to the sintering aid.
A diamond sintered body was produced in the same manner as in Example 1 except that e ₂ O ₆ was used. The obtained sintered body contained a composite oxide of yttrium and iron, and had the same hardness, heat resistance, and cutting performance as in Example 1.

Example 3 A sintering aid was prepared in the same manner as in Example 1 except that a mixture of Y ₂ O ₃ and Fe ₂ O ₃ at a molar ratio of 1: 1 was used as the sintering aid. To produce a diamond sintered body. The obtained sintered body contained a composite oxide of yttrium and iron, and had the same hardness, heat resistance, and cutting performance as in Example 1.

Example 4 The procedure of Example 1 was repeated except that a mixture of Y ₂ O ₃ and Fe ₂ O ₃ at a molar ratio of 3: 5 was used as the sintering aid. To produce a diamond sintered body. The obtained sintered body contained a composite oxide of yttrium and iron, and had the same hardness, heat resistance, and cutting performance as in Example 1.

Example 5 Diamond sintering was carried out in the same manner as in Example 1 except that a mixture of Y ₂ O ₃ and CoO at a molar ratio of 1: 1 was used as a sintering aid. A body was produced. The obtained sintered body contained a composite oxide of yttrium and cobalt, and the hardness, heat resistance, and cutting performance were the same as in Example 1.

Example 6 A sintering aid was prepared in the same manner as in Example 1 except that a mixture of Y ₂ O ₃ and CoFe ₂ O ₄ at a molar ratio of 1: 1 was used as the sintering aid. To produce a diamond sintered body. The obtained sintered body contained a composite oxide of yttrium, iron, and cobalt, and had the same hardness, heat resistance, and cutting performance as in Example 1.

Example 7 As a sintering aid, Y ₃ Fe ₅ O ₁₂ having a particle size of 1 μm was used. Fine synthetic diamond powder having a particle size of 1 μm or less,
mm are alternately laminated and placed in a Mo capsule.
It was kept under a pressure and temperature condition of Pa and 1700 ° C. for 15 minutes and sintered. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 2% by volume of a composite oxide of yttrium and iron was detected in addition to diamond. Further, when the structure was observed with a scanning microscope, it was found that the structure had a dense structure in which fine diamond particles having a uniform particle size (average particle size: 0.5 μm) were bonded, and no abnormal grain growth was observed. When the hardness of this sintered body was evaluated using a Knoop indenter, it was as high as about 7500 Kg / mm ² ,
The hardness hardly changed even after the heat treatment at 1200 ° C. in a vacuum. When a cutting edge for a cutting tool was prepared from this diamond sintered body, an extremely sharp cutting edge was obtained. This was vacuum brazed to a hard metal base using an active brazing material to produce a cutting tool, and the Al-Si alloy was intermittently cut. As a comparative material, a cutting performance was compared under the same conditions using a diamond sintered body having a mean particle size of 0.5 μm using a conventional Co binder. The wear amount of the flank is the same as that of the conventional Co.
With less than 1/3 of the diamond sintered body due to the binder, almost no chipping of the cutting edge was observed, and it was found that it had excellent cutting performance.

Example 8 The procedure of Example 7 was repeated except that a mixture of Y ₂ O ₃ and Fe ₂ O ₃ at a molar ratio of 1: 1 was used as the sintering aid. To produce a diamond sintered body. The obtained sintered body contained a composite oxide of yttrium and iron, and the hardness, toughness, and heat resistance were the same as in Example 7.

Example 9 Diamond having a particle size of 1 to 3 microns
About 10% by volume of Y_ThreeFe_FiveO ₁₂The heat
Coated by plasma method and put into Mo capsule
6.5 GP using a belt-type ultra-high pressure and high temperature generator
a, Hold at 1700 ° C pressure and temperature for 15 minutes and sinter
I let it. X-ray diffraction
When the composition was identified by folding, in addition to diamond, about
10% by volume of complex oxide of yttrium and iron is detected
Was. Observation of the structure shows no abnormal grain growth and uniform
It was found to have a dense structure. The hardness of this sintered body
When the degree was evaluated with a Knoop indenter, it was about 7800 Kg /
mm^TwoHeat treatment at 1200 ° C in vacuum with high hardness
After that there was little change. This diamond sintered body
Made a cutting edge for cutting tools from
A sharp edge was obtained. Using an activated brazing filler metal
Vacuum brazing to hard metal to produce cutting tool, Al-Si alloy
Gold was intermittently cut. Conventional Co binder as comparison material
Using a diamond sintered body with a particle size of 1 to 3 μm.
The cutting performance was compared under one condition. Conventional flank wear
Less than 1/5 of the diamond sintered body with Co binder
Excellent cutting performance with almost no chipping
I found out.

Example 10 A powder obtained by coating about 3% by volume of Y ₃ O ₃ on the surface of a diamond powder having a particle diameter of 1 to 3 μm by a thermal plasma method and a powder of FeO were formed to a thickness of 2 mm and 1 mm, respectively. The layers were alternately laminated and placed in a Mo capsule, and the pressure was adjusted to 6.5 GPa and 1700 ° C. using a belt-type ultrahigh-pressure high-temperature generator.
Hold for 5 minutes and sinter. When the composition of the obtained diamond sintered body was identified by X-ray diffraction, about 6% by volume of a composite oxide of yttrium and iron was detected in addition to diamond. When the structure was observed, no abnormal grain growth was observed at all, indicating that the structure had a homogeneous and dense structure. When the hardness of this sintered body was evaluated using a Knoop indenter, it was found to be about 81
High hardness of 00Kg / mm ² , 1200 ° C in vacuum
After heat treatment, there was almost no change. When a cutting edge for a cutting tool was prepared from this diamond sintered body, an extremely sharp cutting edge was obtained. This was vacuum brazed to a hard metal base using an active brazing material to produce a cutting tool, and the Al-Si alloy was intermittently cut. As a comparative material, a cutting performance was compared under the same conditions using a diamond sintered body having a particle size of 1 to 3 μm using a conventional Co binder. The amount of wear on the flank was 1/5 or less of that of a conventional diamond sintered body made of a Co binder, and there was almost no chipping of the cutting edge, indicating that the material had excellent cutting performance.

(Comparative Example 1) As a sintering aid, Y ₃ Fe ₅
O ₁₂ was used. A small amount of the above powder (about 0.05% by volume) is added to a natural diamond powder having a particle size of 3 to 8 μm,
An attempt was made to produce a diamond sintered body in the same manner as in Example 1 except that a sufficiently mixed material was used as a raw material. However, many unsintered portions remained in the obtained sintered body.

Comparative Example 2 As a sintering aid, Y ₃ Fe ₅
O ₁₂ was used. Production of a diamond sintered body was attempted in the same manner as in Example 1 except that 60 vol% of synthetic diamond powder having a particle size of 3 to 8 μm and 40 vol% of the above powder were added and mixed sufficiently as a raw material. Was. However, the obtained sintered body has insufficient bonding between particles, and has a hardness of 4000K.
g / mm ² .

Comparative Example 3 Y ₃ Fe ₅ was used as a sintering aid.
O ₁₂ was used. Production of a diamond sintered body was attempted in the same manner as in Example 1, except that 10% by volume of this sintering aid was added to a synthetic diamond powder having an average particle diameter of 30 μm, and the mixture was sufficiently mixed as a raw material. A cutting tool was prepared from the obtained sintered body, but it was difficult to obtain a sharp cutting edge, and the cutting edge was noticeable in a cutting test.

[0030]

As described above, the diamond sintered body of the present invention has an unprecedented high strength, heat resistance and abrasion resistance, and has a fine and homogeneous structure. It is very effective as a material for cutting and grinding tools such as ceramics.

Claims (7)

[Claims] 1. A high-strength sintered body comprising 0.1 to 30% by volume of a substance comprising a compound containing yttrium, an iron group metal and oxygen and the balance being diamond particles having an average particle diameter of 10 μm or less. 2. The high-strength sintered body according to claim 1, wherein the compound containing yttrium, iron group metal and oxygen is a composite oxide or solid solution comprising yttrium oxide and iron group metal oxide. 3. A mixture of yttrium oxide and an oxide of an iron group metal or a composite oxide as a sintering aid, and using this powder and diamond powder having an average particle size of 10 μm or less, or an average particle size of 10 μm or less. 3. The method according to claim 1, wherein a diamond powder and a mixed powder of non-diamond carbon are mixed, and the mixture is held under pressure and temperature conditions in a thermodynamically stable region of diamond and sintered. Manufacturing method of strength sintered body. 4. A mixture of yttrium oxide and an oxide of an iron group metal or a composite oxide as a sintering aid, and a compact of this powder and a compact or an average particle of diamond powder having an average particle diameter of 10 μm or less. 2. A method comprising laminating a compact of a mixed powder of diamond powder and non-diamond carbon having a diameter of 10 .mu.m or less, holding the compact under the pressure and temperature conditions in a thermodynamically stable region of diamond, and sintering the compact. Or the method for producing a high-strength sintered body according to 2. 5. A composite oxide or a mixture of yttrium oxide and an iron group metal is formed on the surface of diamond powder having an average particle diameter of 10 μm or less, and this is maintained under pressure and temperature conditions in a thermodynamically stable region of diamond. The method for producing a high-strength sintered body according to claim 1, wherein sintering is performed. 6. A diamond powder compact in which yttrium oxide is formed on the surface of a diamond powder having an average particle diameter of 10 μm or less, and a compact of an iron group metal oxide are laminated. The method for producing a high-strength sintered body according to claim 1, wherein the sintering is performed while maintaining the pressure and temperature conditions in the region. 7. A diamond powder having an iron group metal oxide formed on the surface of a diamond powder having an average particle diameter of 10 μm or less, and a yttrium oxide compact are laminated on each other. The method for producing a high-strength sintered body according to claim 1, wherein the sintering is performed while maintaining the pressure and temperature conditions in the region.