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Institut Sverkhtverdykh Materialov Akademii Nauk Ukrainskoi Ssr

Institut Fizicheskoi Khimii Akademii Nauk

Institut Sverkhtverdykh Materialov Ssr

Valentin N Bakul

Jury I Nikitin

Alexei I Prikhna

Dmitry V Fedoseev

Valentin K Gerasimenko

Boris V Deryagin

Stanislav P Vnukov

Valentin P Varnin

Ivan Fedorovich Vovchanovsky

Vladimir G Poltoratsky

Nekhemian Veniaminovich Tsypin

Anatoly Vasilievich Hochko

Dolores Khaimovna Bronshtein

Nekhemyan Veniaminovich Tsypin

Igor Ivanovich Bilyk

The proposed polycrystalline superhard material comprises sintered particles of cubic boron nitride coated over the whole surface thereof with a layer of a crystalline compound of the chemical formula B.sub.x N.sub.y C.sub.z, where x, y and z can assume any value from 0 to 1, said compound binding together the particles of the cubic boron nitride. According to the present invention the proposed material is produced in the following way: particles of cubic boron nitride are placed in a flow of a gas containing carbon for a carbon layer 1-100 A thick to be built up on the whole surface of said particles. Then the particles of cubic boron nitride with the carbon layer built up over the whole surface of the particles are subjected to sintering at a temperature and under a pressure corresponding to the region of thermodynamic stability of cubic boron nitride. The herein-proposed material is highly uniform and features mechanical properties superior to those of the known cubic boron nitride materials. Thus, for example, under the identical conditions of cutting, durability of cutters made from the proposed material is 2-5 times higher than that of the cutters made from the known material based on cubic boron nitride.

Polycrystalline superhard material and method of producing thereof

The method of preparing superhard articles consists of placing a mixture of powdered hard-alloy matrix material and diamond grains into a hard-alloy envelope formed from a hard-alloy material, preferably of exactly the same composition as the hard-alloy matrix material of the mixture, with the thickness of the hard-alloy envelope over the entire area thereof exceeding by at least 3-4 times the maximum space between any two adjacent diamond grains within the mixture. The mixture in the envelope is then subjected to sintering in a free condition thereof, without any external mechanical loads being applied thereto.

Method of making superhard articles

A method of preparing a polycrystalline diamond member comprising sintering diamond particles having deposited thereon, not only diamond coating, but also diamond-graphite coating In the epitaxial method of coating according to the invention, diamond particles may be the finest ones of a size smaller than one micron. The resulting compact member is characterized in the absence of marked graphite inclusions, and diamond cleavage between the particles results in a considerable improvement of the strength of the compact member.

Polycrystalline diamond member and method of preparing same

A superhard article is produced by heating in two steps a mixture of a hard-alloy matrix material and diamond grains less than 1 mm in size in a graphite press mould. During the first heating step, the mixture is heated to a temperature of 1,200.degree. C at a rate of 1,000.degree.-1,100.degree. C per minute by heating the press mould by high frequency. During the second heating step, the mixture is heated to the sintering temperature, up to 1,800.degree. C at a rate of 3,000.degree.-10,000.degree. C per minute by heating the mixture by the resistance method, i.e. by passing electric current through the mixture while simultaneously heating the press mould by high frequency currents.

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Kyiv, Ukraine

Valentin N Bakul