JP-2026074579-A - Manufacturing method for composite diamond sintered bodies

Abstract

【assignment】 In particular, the objective is to provide a diamond sintered body that can be applied to the processing of all materials, including iron, does not accelerate the graphitization phase transition by binders, and can be manufactured under the same pressure and temperature conditions as currently common cobalt-based diamond sintered bodies (PCDs). [Solution] A method for producing a w-BN-based boron nitride bonded composite diamond sintered body, characterized by densely mixing diamond particles and wurtzite-type boron nitride (w-BN) powder, distributing the w-BN between the diamond particles to form a binary starting composition, and simultaneously subjecting the starting composition to a pressure of 4.5 GPa or more and less than 8 GPa and a temperature of 1200°C or more and less than 2000°C to bond adjacent diamond particles together via the interparticle w-BN phase present between the particles, thereby integrating them. [Selection Diagram] None

Inventors

• 荒木 正任
• 藤野 聡

Assignees

• トーメイダイヤ株式会社
• 荒木 正任

Dates

Publication Date

20260507

Application Date

20241021

Claims (9)

1. A method for producing a w-BN-based boron nitride bonded composite diamond sintered body, characterized by densely mixing diamond particles and wurtzite-type boron nitride (w-BN) powder, distributing the w-BN between the diamond particles to form a binary starting composition, and simultaneously subjecting this starting composition to a pressure of 4.5 GPa or more and less than 8 GPa and a temperature of 1200°C or more and less than 2000°C, thereby bonding adjacent diamond particles together via the w-BN phase present between the diamond particles and integrating them.
2. The method according to claim 1, wherein the binary starting composition contains, by mass ratio of 60-90% diamond particles and 40-10% wurtzite-type boron nitride (w-BN) relative to the total amount of the mixture.
3. The method according to claim 1, wherein the w-BN phase present between the diamond particles contains cubic boron nitride (c-BN) generated by a transition of a portion of the w-BN phase.
4. The method according to claim 1, wherein the w-BN phase present between the diamond particles is composed solely of w-BN and unavoidable impurities.
5. The method according to claim 1, wherein the average particle size of the diamond particles is 1 to 20 μm.
6. The method according to claim 1 or 5, wherein the diamond particles constituting the starting composition are a mixture of main diamond particles having a large average particle diameter and gap-filling diamond particles having a smaller particle diameter.
7. The method according to claim 6, wherein the main diamond particles and gap-filling diamond particles are each composed of multiple sized particles with different average particle sizes.
8. The method according to claim 6, wherein the main diamond particles and gap-filling diamond particles are each composed of multiple sized particles with different average particle sizes, and the average particle size of the gap-filling diamond particles is 1/4 or less of the average particle size of the main diamond particles.
9. (1) First, the gap-filling diamond particles and w-BN are mixed to make a preliminary mixture, and then (2) The method according to claim 1, wherein the starting composition is formed by mixing the premixture with main diamond particles.

Description

This invention relates to a method for manufacturing a composite diamond sintered body in which diamond particles are solidified and integrated via a mixed phase of wurtzite-type boron nitride (w-BN), or a mixture of wurtzite-type boron nitride and a relatively small amount of cubic boron nitride (c-BN). This invention particularly relates to a diamond sintered body and a method for manufacturing the same, which can be applied to the processing of various materials, including ferrous metals, as a cutting tool element with excellent hardness and heat resistance, and can be used in cutting processes in a wide range of fields. Sintered bodies, which combine powdered diamond—an abrasive material with high hardness and excellent wear resistance—have been widely used as suitable cutting tool materials for the manufacture of chips and other components. Such sintered bodies are also called polycrystalline diamond (PCD), and are generally produced by infusing molten sintering aid metals (such as cobalt (Co)) between diamond powder particles under ultra-high pressure and high temperature, thereby integrating the diamond powder through the molten phase. They are widely used as tool materials. However, the cobalt used as a binder acts as a catalyst that causes diamond to graphite at around 700°C. This effect becomes more pronounced due to the heat generated during machining, resulting in a heat resistance problem that makes it difficult to use under high-temperature conditions. While diamond sintered bodies using transition metals or ceramics such as carbides and nitrides of transition metals as binders instead of sintering aid metals are also in practical use, the thermal expansion coefficients of metals and ceramics are orders of magnitude larger than those of diamond. Therefore, the loss of diamond particles due to strain at the interface between diamond and the binder at high temperatures has been a factor in shortening tool life. On the other hand, the high reactivity of diamond itself with iron at high temperatures is a significant drawback that cannot be ignored. Therefore, there is a need to develop a diamond-based mass that overcomes these problems inherent in diamond sintered bodies, allowing it to exhibit the extremely hard properties of diamond as a cutting tip material, and also be applicable to cutting iron-based materials. Methods for preparing polycrystalline diamond (masses) without using cobalt are known. For example, methods using alkaline earth carbonates (Patent Document 1) or boron carbide (Patent Document 2) as binders instead of cobalt, methods using metal carbides (Patent Document 3), and methods for creating a single, directly bonded diamond without using a binder (Patent Document 4) are known. In the method described in Patent Document 1, 0.5 to 15 wt% of boron (B) powder is added to diamond powder as a doping agent to impart conductivity, and alkaline earth carbonate powders such as Mg and Ca are added as components to form the binder phase of the sintered body. In the first stage, conductivity is imparted to the diamond powder by the diffusion of B, and in the second stage, a conductive diamond sintered body is obtained by dissolving and filling the gaps between the diamond powder particles with the binder phase. These processes require ultra-high pressure and high temperature, and the second stage in particular is carried out at 6.0 to 9.0 GPa and 1600 to 2500°C. In the method described in Patent Document 2, it is necessary to infuse boron carbide, which has a melting point of 2450°C, into the spaces between diamond particles in a molten or semi-molten state. Even considering the decrease in sintering temperature due to fine powdering, heating to approximately 2000°C is required. To maintain the diamond in a thermodynamically stable state at this temperature, it is necessary to maintain an ultra-high pressure of 7 GPa or more, further increasing the burden on the sintering apparatus. In the method described in Patent Document 3, a reaction is performed in which a starting material containing diamond particles and transition metal powder is subjected to a reaction temperature of 2000°C or higher, forming a ceramic phase containing transition metal carbides through a reaction between the components of the starting material, and bonding the diamond particles together via this ceramic phase to form a diamond-based sintered composite material. This method discloses a technique that uses a combustion synthesis reaction in the ceramic formation reaction to partially melt and densely integrate the entire material. The method described in Patent Document 4 involves the simultaneous direct conversion of graphite to diamond and sintering, resulting in a tough sintered body composed solely of diamond. However, to ensure the thermodynamic stability of diamond during the high-temperature reaction, it is necessary to maintain an even higher pressure of 8 GPa or more. Japanese Patent Publication No. 2008-