CS217643B1 - A method for producing compacts from super-hard materials - Google Patents

Abstract

The invention relates to the field of powder metallurgy and pressing technology. It solves a method of producing compacts from superhard materials based on diamonds, cubic or wurtzite Lion's nitride, or their mutual combinations, in a high-pressure tool with electrical heating at pressures higher than 2 GPa and temperatures corresponding to the equilibrium diagrams of the processed materials. The essence of the invention is that the heating of the charge is carried out by direct passage of current through electrically conductive components of the charge and a sleeve with sintered powder.

Description

BACKGROUND OF THE INVENTION The present invention relates to a process for producing compacts of superhard materials, based on diamonds, cubic or wurzitic boron nitride, or combinations thereof, in a high-pressure tool with electrical heating at pressures greater than 2 GPa and temperatures corresponding to the equilibrium diagrams of materials.

The feedstocks for these compacts are powders of super-hard materials, optionally with additional additions of activators or binding phases, which, under suitably selected conditions (pressure, temperature, time, packing arrangement), are compressed into a compact body. The compacts have a wide range of applications: wire drawing dies, cutting materials, grinding wheel dressers, drill inserts, high abrasion resistant components and others. The material for the chamber suitable for both the manufacture of peas and the compacts of superhard materials is specified in detail in U.S. Patent No. 3,030,662. The presently known compositions and configurations of the compact chamber preparation itself are disclosed in British Patent Nos. 1,240,525 and U.S. Pat. No. 1,466,312 and in the German Patent No. 2,232,225. A spiolefinic feature of all these known arrangements is the indirect heating of the charge itself, which is insulated from the heating elements (graphite tubes and graphite plugs) by an electrically non-conductive material. according to British Patent No. 1 466 312. The heat generated by the passage of electric current through the heating graphite tube gradually heats the entire reaction charge The purpose of the individual components of the charge is described in detail in U.S. Patent No. 3,030,662 and British Patent No. 1,466,312 However, it is evident from the illustration, there is a flannel filling and its arrangement in the chamber is very demanding on the preparation of many components from different materials and their mutual assembly. Another disadvantage is the low spatial utilization of the chamber, since the final product is only a component composed of a cemented carbide sleeve surrounding a cemented compact of superhard material. This small space utilization of the chamber is particularly disadvantageous for high-pressure tools. Any increase in chamber diameter results in a transition to a larger, high-pressure tool, thereby increasing the lifetime of a high-cost material and high-cost tool while at the same time significantly increasing the overall pressing force requirements (eg high-pressure tool with 0 25 mm die) mm, a pressing force of about 5-6 MN) is required to generate a pressure of about 5.5 GPa.

These disadvantages are overcome by a process for producing compacts of superhard diamond-based materials, cubic or wurzitic boron nitride, or combinations thereof, in a high-pressure electric heating tool at pressures greater than 2 GPa and temperatures corresponding to the equilibrium diagrams of the materials of the present invention. characterized in that the charge is heated by direct current flow through the electrically conductive charge components and a sintered powder sleeve.

An essential advantage of the proposed method of manufacturing the compacts according to the invention is that the individual parts of the assembly are simple to construct and manufacture, which makes it easy to assemble the entire filling of the high-pressure tool. Another advantage is better spatial utilization of the high-pressure tool chamber.

In the drawings, FIGS. 1 and 2 show variants of the design of the tools for direct heating of the cartridge.

The tool consists of punches U, a die 10 and an interleaved seal 13. The actual powder filling of the super-hard material 5 'is surrounded by a carbide receiver 5 or possibly an insulating tube 9. The metal foil 7, the heating element B and the metal roller 8. The assembly is housed in a chamber 1 closed by contact 4, insulating insert 3, metal ring 2, and contact 12 against which punches 11 abut.

Example

The high-pressure tool consists of a self-contained chamber 1 made of an insulating hydrostatic material (for example pyrophile) with a filling opening closed on both sides by a shaped metal ring 2 (for example steel), an insulating insert 3 (ceramic) and a metal contact 4 (for example nickel) The shape and proportionality of the ring prevents the occurrence of adverse deformations, which are particularly detrimental when the sintering and loosening in the chamber are completed, and a sleeve 5 of metallic, electrically conductive material (e.g. cemented carbide) is inserted into the chamber opening. Both ends of the sleeve 5 are separated from the heating cylinder 6 (e.g. graphite) by a high-melting metal foil 7 (e.g. Ti, Ta, Mo, Zr). It is filled with a metal roller 8, which is used mainly as a conductor of electric power current (eg steel, nickel), but at the same time also contributing to the overall heating of the chamber 1. After pressing the chamber and switching on the power supply, the electric current is supplied by a punch 11 via a contact 12, metal ring 2, contact 4, metal roller 8, heating element. 6 and a metal foil 7 into a sleeve 5 in which the powder is of a super-hard material. In the same way, the current passes to the second punch. Another variant of the same system in which, in order to reduce the risk of damage to the final product due to contact with the material of the coimulator 1, the sleeve 5 is separated by another insulating insert 9, which can be made of metal and non-metal material. The reduced chamber assembly work and increased spatial utilization ensure this heating by direct current flow by reducing the occurrence of high voltages due to thermal gradients that affect the destruction of the sintered product when heated and cooled in an indirectly heated charge.

Claims (2)

SUBJECT Process for producing compacts of superhard materials based on diamonds, cubic or wurzitic boron nitride, or their combinations, in a high-pressure tool with electric heating at pressures higher than 2 GPa and temperatures corresponding to the invention giving equilibrium diagrams of the materials to be processed, characterized in that the charge is heated by direct current flow through the electrically conductive components of the charge and the sintered powder sleeve.