JP2782524B2 - High density phase boron nitride based reaction sintered body and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high-density phase boron nitride-based reaction sintered body obtained by high pressure and high temperature, specifically, for example, hardened steel,
Cubic boron nitride and / or a material suitable for cutting tools used for drills, milling tools, turning tools, etc. for machining hard-to-cut materials such as high-hardness cast iron or heat-resistant alloys, or for wear-resistant tools such as slitters and dies. Also, the present invention relates to a high-density phase boron nitride-based reaction sintered body containing wurtzite boron nitride and a method for producing the same.

(Prior Art) Many proposals have been made for a high-density phase boron nitride-based sintered body composed of a hard phase of cubic boron nitride and / or wurtzite-type boron nitride and a binder phase. The high-density phase boron nitride-based sintered body can be roughly classified by a binder phase component. First, a so-called metal-based binder phase in which the binder phase is made of a metal or an alloy, and secondly, the binder phase is composed of a ceramic and a metal or an alloy. Thirdly, there is a so-called cermet-based binder phase, and thirdly, a so-called ceramic-based binder phase in which the binder phase comprises only ceramics. Among these, the high-density phase boron nitride-based sintered body composed of the first metal-based binder phase has a problem that the binder phase is softened under conditions where it is exposed to a high temperature, and the wear resistance is significantly reduced. . Further, the high-density phase boron nitride-based sintered body composed of the third ceramic-based binder phase is remarkably excellent in the softening resistance of the binder phase at a high temperature, but when used for an application in which an impact is applied, chipping or There is a problem that the life is shortened due to the loss. A second binder phase having both advantages of the first binder phase and the third binder phase is a second binder phase.
Although there is a high-density phase boron nitride-based sintered body composed of a cermet-based binder phase, there is a problem that both the wear resistance and the fracture resistance have not yet been improved.

A representative example of the binder phase in this high-density phase boron nitride-based sintered body has been examined.
49031, JP-B-57-3631, and JP-B-58-575.
There is 02 publication.

(Problems to be Solved by the Invention) Japanese Patent Publication No. 55-49031 discloses that high pressure phase boron nitride powder is added with aluminum powder or niobium or its alloy powder, molded or granulated, and subjected to a nitrogen or ammonia atmosphere in a nitrogen or ammonia atmosphere. A method for producing a high-pressure phase boron nitride sintered body heated at 1500 ° C. is disclosed. 55-49
No. 031 discloses that niobium or its alloy powder is used as a starting material, and is nitrided in a nitrogen or ammonia atmosphere.
Although a method for producing niobium nitride and producing a high-pressure phase boron nitride sintered body of a binder phase containing the niobium nitride is disclosed, when using an ultrahigh-pressure high-temperature apparatus, it is necessary to maintain the nitrogen or ammonia atmosphere. However, there is a problem that chipping and chipping are apt to occur due to low adhesion between the bonding phase of niobium nitride nitrided in a nitrogen or ammonia atmosphere and the high-pressure phase boron nitride.

Japanese Patent Publication No. 57-3631 discloses cubic boron nitride by volume.
80 to 20%, with the balance consisting of carbides, nitrides, borides, silicides or their mixtures or mutual solid solution compounds of metals of groups 4a, 5a and 6a of the periodic table, and this mixture or compound is a sintered body There is disclosed a sintered body for a high-hardness tool in which a continuous bonded phase is formed. This Japanese Patent Publication No. 57-3631 discloses a periodic table 4a, 5a, 6a group metal carbide, nitride,
A powder of a boride, a silicide, a mixture thereof, or a mutual solid solution compound is used as a starting material. A cubic boron nitride-based sintered body of a binder phase composed of the starting material is disclosed, but a dense sintered body is obtained. It is very difficult. Therefore, Japanese Patent Publication No. 57-3631 discloses MC ₁ ± _X , MN ₁ ± _X , M (C,
N) ₁ ± _X , (M indicates a metal of Ti, Zr, Hf, and ₁ ± _X is 0.97
Below 0.40 is shown. Although it is disclosed that the difficulty of sintering is solved by using a non-stoichiometric composition represented by the formula (1) as a starting material, cubic boron nitride and a binder phase in the obtained sintered body are disclosed. However, there is a problem that chipping resistance or chipping resistance is apt to deteriorate.

JP-B-58-57502 discloses cubic boron nitride 40-97v.
ol%, a sintered material comprising one or more refractory metals of W, Mo, Ta, Ti and Nb and 3 to 60 vol% of unavoidable impurities is disclosed. Japanese Patent Publication No. 58-57502 discloses a cubic nitride comprising one or more of W, Mo, Ta, Ti and Nb as a starting material and a binding phase of the high melting metal. Although a boron-based sintered body is disclosed,
There is a problem that the binder phase easily softens at a high temperature, and is therefore easily damaged even when used as a tool.

The present invention has solved the above-mentioned problems. Specifically, the grain boundaries of the hard phase of cubic boron nitride and / or wurtzite-type boron nitride are formed in the periodic table 4a, 5a, 6a group metal. A high-density phase boron nitride-based reaction sintered body, which is made denser by being surrounded by a binder phase containing nitride and boride, thereby improving both wear resistance and fracture resistance, and An object of the present invention is to provide a manufacturing method thereof.

(Means for Solving the Problems) The present inventors have developed a high-density phase boron nitride-based sintered body containing cubic boron nitride and / or wurtzite-type boron nitride, which has wear resistance and chipping resistance. For the purpose of improving both, the cermet-based binder phase was studied, and among the cermet-based binder phases composed of ceramics and metals or alloys, metals of the periodic table 4a, 5a, and 6a as metals or alloys were used. or its alloy as the starting material, the sintering conditions at high pressure and temperature, is reacted sintering the metal or alloy and boron nitride (e.g., reaction of _{3Ti + 2BN → 2TiN + TiB 2} ), and a nitride of the metal or alloy A boron nitride-based sintered body consisting of a binder phase containing boride is obtained, and the sintered body has boron nitride as a core, and a peripheral portion surrounding the core is formed by reaction sintering. Between nitride and boride To become possible, the performance of a tool of the sintered body also thus obtained, and in particular wear resistance and breakage resistance was obtained a finding that will significantly superior as. Based on this finding, the present invention has been completed.

That is, the high-density phase boron nitride-based reaction sintered body of the present invention comprises a boron nitride having a hard phase of cubic boron nitride and / or wurtzite-type boron nitride of 20 to 90 vol%, and a balance of a binder phase and unavoidable impurities. A base sintered body, wherein the binder phase comprises at least one first binder phase in a periodic table 4a, 5a, 6a group metal nitride and a mutual solid solution thereof, and a periodic table 4a, 5a,
A boride of a Group 6a metal and at least one second binder phase in a mutual solid solution thereof, wherein the atomic ratio of nitrogen to boron contained in the binder phase is 10: 1 to 1:10. Wherein the core portion is the hard phase and the peripheral portion surrounding the core portion contains particles having a cored structure composed of the first binding phase and / or the second binding phase. It is a sintered body.

When the amount of the hard phase in the high-density phase boron nitride-based reaction sintered body of the present invention is less than 20 vol% in the sintered body, the hardness of the sintered body becomes too low, and the wear resistance and the fracture resistance are deteriorated. Becomes Conversely, when the amount of the hard phase exceeds 90 vol% in the sintered body, the contact ratio between the hard phase particles increases, and the metal is relatively formed in the sintered body by the metal that has contributed to the reaction sintering. The amount of the binder phase is less than 10 vol%, and as a result, the adhesion strength between the hard phase and the binder phase at the grain boundary is reduced, and the wear resistance and the fracture resistance are deteriorated. For this reason, the amount of the hard phase in the sintered body is 20
9090 vol%. The particle size of this hard phase is
There is no particular limitation, and those having a particle size of conventional cubic boron nitride or wurtzite boron nitride can be used.

The binder phase in the high-density phase boron nitride-based reaction sintered body of the present invention is at least one type of first binder phase in the periodic table 4a, 5a, 6a group metal nitride and their mutual solid solution, for example,
TiN, ZrN, HfN, VN, NbN, TaN, CrN, (Ti, Zr) N, (Ti, Cr) N,
The first bonded phase consisting of (Ti, Nb) N and (Ti, V) N and the periodic table 4
at least one second binder phase in borides of group a, 5a, 6a metals and their mutual solid solutions, for example, TiB ₂ , ZrB ₂ , Hf
_{B 2, VB 2, NbB 2} , TaB 2, CrB 2, MoB 2, WB 2, W 2 B 5, (Ti, Zr) B 2,
A second binder phase consisting of (Ti, Cr) B ₂ , (Ti, Mo) B ₂ , (Ti, V) B ₂ , and the atoms of nitrogen and boron contained in this binder phase The ratio is comprised between 10: 1 and 1:10. The atomic ratio of nitrogen to boron contained in this bonded phase is 1
When the ratio deviates from 0: 1 to 1:10, the total amount of the nitride as the first binder phase and the boride as the second binder phase obtained by the reaction sintering decreases, and as a result, the wear resistance of the sintered body is reduced. And deterioration of the fracture resistance. For this reason, the atomic ratio between nitrogen and boron contained in the binder phase is determined to be 10: 1 to 1:10. Then, the hard phase is used as a core, and a peripheral part surrounding the core is formed of a first binder phase and / or
Alternatively, by containing cored particles composed of the second binder phase, the grain boundaries between the hard phase and the binder phase become denser, and a sintered body having excellent strength can be obtained.

In the high-density phase boron nitride-based reaction sintered body of the present invention, in addition to the first binder phase and the second binder phase, 3% or less of Cr, Mo, W, Fe, Ni, Co and Replaced by at least one third binder phase in two or more alloys of
A sintered body having excellent abrasion resistance and fracture resistance is also formed of the binder phase, the second binder phase, and the third binder phase. Of the third binder phase, Cr, Mo, W correspond to the allowable value when remaining in the sintered body as unreacted, and Fe, Ni, Co, remain in the sintered body as unavoidable impurities. This corresponds to a permissible value including both the case where it is included and the case where it is contained as a sintering accelerator without reducing the wear resistance. Further, the binder phase in the high-density phase boron nitride-based reaction sintered body of the present invention comprises a first binder phase and a second binder phase.
In addition to the binder phase, less than 85% of the binder phase accounts for 4a, 5a, 6a of the periodic table.
Group metal carbides, carbonitrides and their mutual solid solutions, and aluminum oxides, aluminum nitrides, aluminum borides, silicon carbide, silicon nitrides and at least one of these mutual solid solutions substituted by a fourth binder phase The first and second binder phases, or the first and second binder phases, the third and third binder phases, and the fourth and fourth binder phases also have wear resistance and resistance to wear. It becomes a sintered body with excellent deficiency. Among the binder phases, the fourth binder phase is, for example, TiC, ZrC, HfC, VC, NbC, TaC, Cr ₃ C ₂ , Mo ₂ C, WC, Ti (C,
N), Zr (C, N), Hf (C, N), V (C, N), Nb (C, N), Ta (C,
N), (Ti, Zr) C, (Ti, Hf) C, (Ti, V) C, (Ti, Ta) C,
(Ti, Nb) C, (Ti, Ta, Nb) C, (Ti, W) C, (Ti, Mo, W) C,
(Ti, Ta, W) C, (Ti, Zr) (C, N), (Ti, Ta) (C, N),
(Ti, W) (C, N), (Ti, Ta, W) (C, N), Al ₂ O ₃ , AlN, Al
B ₂ , SiC, Si ₃ N ₄ , (Si, Al) (O, N) can be mentioned. The fourth bonded phase, the second bonded phase and the first bonded phase described above have a non-stoichiometric composition or a stoichiometric composition, and the fourth bonded phase, the second bonded phase, and the first bonded phase. Are, for example, a mutual solid solution of a fourth binder phase and a second binder phase, a mutual solid solution of a fourth binder phase and a first binder phase, a mutual solid solution of a second binder phase and a first binder phase, or a fourth binder phase and a second binder phase. It may be present as a mutual solid solution of the binder phase and the first binder phase.

The binder phase in the high-density phase boron nitride-based reaction sintered body of the present invention, the atomic ratio of nitrogen and boron contained in the binder phase is particularly preferably 2: 1 to 1: 2, When a large amount of the first bonded phase, the second bonded phase or the fourth bonded phase is contained as a starting material in the production method described below,
The atomic ratio of nitrogen to boron contained in the binder phase is 2: 1
Even if it is out of the range of 〜1: 2, if it is in the range of 4: 1 to 1: 7, almost the same effect can be exerted, so that it is a particularly preferable range.

The high-density phase boron nitride-based reaction sintered body of the present invention comprises a high-density phase boron nitride, cubic boron nitride and / or wurtzite-type boron nitride, and a group 4a, 5a, or 6a metal of the periodic table under high pressure and high temperature. This is obtained by reaction sintering.

That is, the method for producing a high-density phase boron nitride-based reaction sintered body of the present invention comprises the first starting material of cubic boron nitride powder and / or wurtzite-type boron nitride powder and the periodic table 4a, 5a,
A mixed powder consisting of the 6a group metal powder and at least one of the two or more alloy powders as the second starting material or the mixed powder is formed into a compact, and then placed in an ultrahigh-pressure high-temperature apparatus, Sintered body obtained by sintering under pressure and high temperature is cubic boron nitride and / or wurtzite boron nitride 20 to 90 vo
l%, the remaining binder phase and unavoidable impurities, wherein the binder phase comprises at least one first binder phase of a nitride of a metal of Group 4a, 5a, or 6a of the periodic table and their mutual solid solution; Law table
The at least one second binder phase in the boride of a group 4a, 5a, or 6a metal and their mutual solid solution has an atomic ratio of nitrogen to boron contained in the binder phase of 10: 1 to 1: 1. : 10,
A method of obtaining a sintered body in which a core portion is the hard phase and a peripheral portion surrounding the core portion contains particles having a cored structure composed of the first binder phase and / or the second binder phase. It is.

The method for producing a high-density phase boron nitride-based reaction sintered body of the present invention is a method of forming a sintered body while reacting a first starting material and a second starting material during sintering at high pressure and high temperature. This is a method in which a nitride of the second starting material and a boride of the second starting material, which are formed by the reaction between the first and second starting materials, are present as a binder phase in the aggregate.

As the first starting material and the second starting material in the production method of the present invention, those having commercially available particle sizes may be used,
In particular, the smaller the particle size of the second starting material is, the higher the activation is. Therefore, it is preferable to carry out the reaction sintering.
When the second starting material becomes finer, it is preferable that the second starting material is subjected to a reduction treatment because oxidation or adhesion of oxygen easily occurs on the surface of the powder. Further, a hydrogen compound of a metal of Group 4a, 5a, or 6a of the periodic table and It is preferable that a powder obtained by reducing at least one of these two or more hydrogen compounds is used as the second starting material.

The second starting material in the production method of the present invention only needs to have an amount for reacting with the first starting material at the time of sintering to form a dense sintered body. The optimum amount of the starting material depends on the sintering conditions at high pressure and high temperature, but it is preferable that the starting material contains at least 10 vol% of the whole starting material. When the second starting material contains a large amount of the second starting material, the unreacted second
A large amount of the starting material remains, resulting in a decrease in wear resistance and fracture resistance. To this end, less than 85% of the second starting material is made of carbides, nitrides, borides and their mutual solid solutions of metals of groups 4a, 5a and 6a of the periodic table, as well as aluminum oxide, aluminum nitride, aluminum, silicon carbide and nitride. It is preferred to substitute the fourth starting material consisting of at least one powder of silicon, silicon and their mutual solid solution, especially for a combination having a small amount of the first starting material and a large amount of the second starting material. If so, the addition of a fourth starting material is preferred.

The sintering conditions at high pressure and high temperature in the production method of the present invention are as follows:
Although the conditions for a conventional high-density phase boron nitride-based reaction sintered body may be sufficient, a pressure of 2 GPa or more and a temperature of
The condition of 1500 ° C. or higher is preferable, and in particular, the condition of a pressure of 2 GPa or higher and a temperature of 1600 ° C. or higher is preferable in order that almost no second starting material remains in the sintered body.

Instead of the powdered second starting material, a composite powder obtained by coating the surface of the first starting material with the second starting material by, for example, a physical vapor deposition method can be used as the starting material.

The high-density phase boron nitride-based reaction sintered body of the present invention thus obtained is directly bonded to, for example, a cemented carbide substrate, or on the surface of a cemented carbide substrate, for example, the periodic table 4a, 5a An intermediate layer of a metal such as group 6a or 6a is applied, and the sintered body of the present invention is joined to the surface of the intermediate layer to form a composite sintered body. This is preferable because a reaction between the material and the second starting material and a reaction between the intermediate layer and the second starting material also occur to obtain a composite sintered body having excellent bonding strength.

(Function) The high-density phase boron nitride-based reaction sintered body of the present invention acts to enhance the densification while the first binder phase and the second binder phase surround the grain boundary of the hard phase. The hard phase also has a function of strongly retaining the hard phase. As a result, the hard phase has a function of increasing the fracture resistance of the tool, and the hard phase has a function of enhancing the wear resistance of the tool.

Further, in the method for producing a high-density phase boron nitride-based reaction sintered body of the present invention, the second starting material, which is easily plastically deformed, surrounds the grain boundary of the first starting material. In addition to acting to prevent back-conversion to phase boron nitride, it also acts to increase the reactivity between the second starting material and the first starting material, resulting in bridging of the first starting material (voids in the powder particles). It has the function of preventing the occurrence.

(Example) Example 1 Cubic boron nitride (CBN) powder having a particle size of 5 μm or less;
A wurtzite-type boron nitride (WBN) powder having a particle size of 1 μm or less, and various metal powders and various hydrogen compound powders having an average particle size of 5 μm or less are compounded as shown in Table 1, and each compounded powder is A cemented carbide ball and ethanol were placed in a stainless steel container, mixed for 30 minutes, and then dried to obtain a mixed powder.

Among these mixed powders, those containing a hydrogen compound powder are subjected to reduction treatment at 10 ^-6 torr, 600 ° C., and held for 1 hour.
Others are degassed by holding at 10 ^-6 torr, 600 ° C, 1 hour, then 2
The molded body was molded into a predetermined shape at a pressure of t / cm ² , and the molded body was placed in an ultrahigh-pressure high-temperature apparatus comprising a pressure medium and a graphite heater. The pressure was 5 GPa and the temperature was 3 g at each temperature shown in Table 1.
Hold for 0 minutes and sinter. Each of the samples thus obtained was subjected to X-ray diffraction to analyze the constituent components of the sintered body, and the results are shown in Table 1. Inventive products 1 to 1 shown in Table 1
7, when the microstructures of the respective sintered bodies of the comparative product 1 with the binder phase content deviated and the comparative products 2 and 3 having different binder phase components were observed with a scanning electron microscope, the products 1 to 7 of the present invention showed that Comparative products 1 to 1 mainly contained cored particles
No. 3, especially Comparative product 3, had no cored particles. The hardness of these samples was measured by Myloc Vickers, and the results are shown in Table 2. Each of the samples shown in Table 1 was 1 m on the surface of the WC-6% Co cemented carbide substrate.
m and joined together at the same time as sintering to form a composite sintered body, finished in the shape of SNGN160408, and then performed a cutting test under the following conditions (A) and (B). Also shown in the table.

(A) Cutting Test Workpiece _{SKH 9 (H R C 60~65)} 150φ outer peripheral continuous cutting Cutting speed of: 100 m / min Depth of cut: 0.5mm feed Ri: 0.1 mm / rev Evaluation: average flank wear ( Time until V _B ) reaches 0.2 mm, or reaches the end of its life due to chipping or chipping.

(B) Cutting Test Workpiece FC 35 (H _S 28~33) 200φ interrupted cutting cutting speed in the groove 4 pieces of 15mm wide × 20 mm depth in the work material: 500 meters / min Depth of cut: 0.5mm feed : 0.2mm / rev Evaluation: Time until chipping or breakage.

Example 2 In addition to the starting materials used in Example 1, the average particle size was 3 μm.
The following various ceramic powders were blended as shown in Table 3, the sintering temperature at high pressure and high temperature was as shown in Table 3, and other conditions were the same as in Example 1 to prepare respective samples. Each sample thus obtained was subjected to X-ray diffraction to analyze the constituent components of the sintered body, and the results are shown in Table 3. As in Example 1, the microstructures of the sintered bodies of the inventive products 13 to 20 and the comparative products 7 and 8 were observed with a scanning electron microscope. As a result, the inventive products 13 to 20 had a cored structure. While the particles mainly contained particles, Comparative Examples 7 and 8 did not have particles having a cored structure. Further, the hardness of these samples was measured with a micro Vickers, and the results are shown in Table 4. Further, after preparing a composite sintered body in the same manner as in Example 1, the following (C) and (D) A cutting test was performed under the conditions, and the results are shown in Table 4.

(C) cutting test workpiece _{SKD 11 (H R C 60~63)} 150φ outer peripheral continuous cutting Cutting speed of: 100 m / min Depth of cut: 0.5mm feed Ri: 0.1 mm / rev Evaluation: average flank wear ( The time until V _B ) reaches 0.15 mm, or until the end of life due to chipping or chipping.

(D) cutting test workpiece _{SKD 11 (H R C 60~63)} 15mm wide × 20 mm deep grooves four to work material 150φ entered was interrupted cutting Cutting speed: 100 m / min Depth of cut: 0.5mm feed : 0.1mm / rev Evaluation: Time until chipping or breakage.

(Effect of the Invention) The high-density phase boron nitride-based reaction sintered body of the present invention has a higher abrasion resistance than a comparative boron nitride-based sintered body outside the scope of the present invention or a conventional boron nitride-based sintered body. and chipping resistance is excellent significantly, there is an effect that even about 1.7 to 8 times when cutting high hardness material of about H _R C60 becomes long life, 4-9 times when cutting cast iron Also has the effect of extending the life.

Claims (7)

(57) [Claims] 1. A boron nitride-based sintered body comprising 20 to 90 vol% of a hard phase of cubic boron nitride and / or wurtzite-type boron nitride and the balance being a binder phase and unavoidable impurities, wherein the binder phase is periodic. Table 4a, 5a, 6a At least one first binder phase in the metal nitride and their mutual solid solution, and the periodic table 4a, 5a, 6a boride of the metal and their mutual solid solution It comprises at least one kind of second binder phase, and the atomic ratio of nitrogen to boron contained in the binder phase is 10: 1 to 1:10
Wherein the core portion is the hard phase and the peripheral portion surrounding the core portion contains particles having a cored structure composed of the first binding phase and / or the second binding phase. High density phase boron nitride based reaction sintered body. 2. The binder phase according to claim 1, wherein 3% or less of said binder phase is Cr, M.
2. The high-density phase according to claim 1, wherein the high-density phase is replaced by at least one third binder phase among o, W, Fe, Ni, Co and two or more of these alloys. Boron nitride-based reaction sintered body. 3. The binder phase according to claim 1, wherein 85% or less of the binder phase comprises carbides, carbonitrides and mutual solid solutions of metals belonging to groups 4a, 5a and 6a of the periodic table, and aluminum oxide, aluminum boride, and nitride. 2. The method according to claim 1, wherein said at least one fourth binder phase is substituted among aluminum, silicon carbide, silicon nitride, and a mutual solid solution thereof.
Item 3. The high-density phase boron nitride-based reaction sintered body according to item 2 or 2. 4. A cubic boron nitride powder and / or a wurtzite-type boron nitride powder as a first starting material, a powder of a Group 4a, 5a, or 6a metal of the periodic table, and at least one of these two or more alloy powders. A mixed powder of one kind of the second starting material or the mixed powder is formed into a compact, and then placed in an ultra-high pressure and high temperature apparatus. Then, the first starting material and the second
By reacting and sintering the starting material, cubic boron nitride and / or wurtzite-type boron nitride 20 to 90 vol%,
The remaining binder phase and unavoidable impurities, wherein the binder phase comprises at least one first binder phase of a nitride of a group 4a metal, a group 6a metal and their mutual solid solution, and a periodic table 4a, 5a, 6a
A boride of a group metal and at least one second binder phase in a mutual solid solution thereof, wherein the atomic ratio of nitrogen to boron contained in the binder phase is from 10: 1 to 1:10. Become
Obtaining a sintered body in which a core portion is the hard phase and a peripheral portion surrounding the core portion contains particles having a cored structure composed of the first binder phase and / or the second binder phase. A method for producing a high-density phase boron nitride-based reaction sintered body, characterized in that: 5. The second starting material is a powder obtained by subjecting at least one of metals belonging to groups 4a, 5a, and 6a of the periodic table and a hydrogen compound comprising an alloy of two or more thereof to a reduction treatment. The method for producing a high-density phase boron nitride-based reaction sintered body according to claim 4, characterized in that: 6. The second starting material is 3% of the second starting material.
% Of Fe, Ni, Co and at least one of the three or more alloys thereof is replaced by a third starting material, and 3% of the sintered body obtained by reaction sintering is used in the above-mentioned binder phase. Less than%
6. The method according to claim 4, wherein said at least one third binder phase is substituted with at least one of Cr, Mo, W, Fe, Ni, Co and two or more of these alloys. 4. The method for producing a high-density phase boron nitride-based reaction sintered body according to claim 1. 7. The second starting material comprises 85% of the second starting material.
% Or less of carbides, nitrides, borides and their mutual solid solutions of metals of Groups 4a, 5a and 6a of the periodic table, as well as aluminum oxide, aluminum boride, aluminum nitride, aluminum, silicon carbide, silicon nitride and their silicon 85% or less of the binder phase of the sintered body obtained by reaction sintering, which is replaced by a fourth starting material consisting of at least one kind of powder in the solid solution, is a carbide of a metal of Group 4a, 5a, 6a of the periodic table; Carbonitrides and their mutual solid solutions, aluminum oxide,
Aluminum nitride, aluminum boride, silicon carbide,
At least one of silicon nitride and their mutual solid solution;
7. The method for producing a high-density phase boron nitride-based reaction sintered body according to claim 4, characterized in that the sintered body is substituted with a kind of a fourth bonded phase.