RU1792928C - Method of diamond polycrystalline-elements manufacturing - Google Patents

Description

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The invention relates to the production of noi and crystalline diamond sintering materials under conditions of high pressures of the temperature of diamond powder, intended primarily to support drilling and cutting tools, can also be used to equip drawing tools.

Closest to the proposed technical solution is a method for producing a diamond-non-diamond carbon gyulic crystalline composite, consisting mainly of 50-99% by weight of diamond and 50-1% of graphite and sintering activating agents, according to US patent No. 3913280, class In 24 D 3/02, published 21 / 0.79. The method consists in sintering initially individual diamond particles

by acting on a mixture of diamond particles and a sinter activating agent, pressures and temperatures at which the diamond is simultaneously: a) thermodynamically unstable with respect to graphite and b) capable of sintering in a shorter period of time than is required for the transformation of diamond into polycrystalline composition below 50 may. %

Moreover, said sintering activating agent includes at least one element selected from the group consisting of aluminum, magnesium, beryllium, boron, hafnium, molybdenum, niobium, nitrogen, rhenium, consisting of refractory borides, carbides, nitrides, oxides and silicides. A method of combining diamond with diamond to produce said composite comprises: - atX |

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preparing a homogeneous mixture of diamond particles and means; activating sintering, Y effect on 1 mixture of temperature and dy; laziness; in which the diamond is unstable, b until then, almost half the pc. A homogeneous composite beyond a certain configuration, moreover, the specified homogeneous composite ylketshet directly, the only connection of diamond with / diamond, combining the diamond particles, a: the gaps between them are filled graphite and special activating agent;: l l; ; .//.- ::: ..- :: v. ;; ..; : - :; ..

 - :::, When sintering a diamond powder, FAC; TRO; M, which counteracts the formation of strong bonding diamond. - diamond and the production of a densely-baked polycrystal, is the interaction of diamond grains with oxygen and; its compounds located in the pores of the diamond layer and the adsorbed surfaces of diamond particles

::. The use of magnesium as an activating, sintering additive (agent), which is active: interacting with oxygen and forming a stable compound with it, allows one to improve the diamond – diamond bond, since during sintering, oxygen primarily interacts with that part The surface of the diamond grain, which undergoes the greatest degree of plastic deformation, has an increased value of surface energy, and this area is the area of formation of the contact isthmus between the sintering diamond particles. A decrease in the intensity of this process leads to an increase in the strength of the resulting polycrystal. However, along with the formation

; of stable magnesium oxides, there is a rather active interaction of magnesium with diamond, and according to the state diagram of magnesium-carbon (state diagram of the magnesium-carbon system at a pressure of 7.7 GPa (A.A. Shulzhenkr, I.Yu. Ignatiev, N .KB.elvina, I.S.Belorusov). Superhard materials - 1988 - N ° 6, pp. 3-5) at high pressure, magnesium carbides M.dC and MDSa are formed, which are high pressure phases, and at atmospheric pressure they are unstable

compounds. Partially, these carbides are located in closed pores inside the polycrystal.; But if they form bound chains there that have an exit to the surface, then they decompose upon contact with air moisture. And in fact, and in

 in another case, there is a loss of mass of diamond grains constituting the polycrystal, which leads to a deterioration in its wear resistance, -;

If magnesium - carbon is present in the mixture in addition to diamond particles and graphite, then a smaller part of the diamond powder will be spent on the formation of magnesium carbides.

since a certain amount of carbides will be formed due to the interaction of magnesium with graphite. However, it is obvious that the introduction of graphite into a mixture of magnesium carbon by recrystallization of part of the diamond powder into graphite at a pressure

. temperature corresponding to the region of thermodynamic stability of graphite, such a loss reduction, diamonds cannot be achieved. .. -

An object of the invention is to increase the wear resistance of elements. This goal is achieved by the dem that in the method of manufacturing diamond polycrystalline elements to equip the drilling and

blade tools by sintering diamond powder in the presence of magnesium under the influence of pressure and temperature, the layers of diamond powder are placed in series with disks pressed from

a mixture containing magnesium and trafite, the graphite content of the mixture being May 7-90.%, the mass of the disks being at least 3.8% or the mass of diamond powder, and the process is carried out in the field of thermodynamic stability of diamond.

In order to increase the crack resistance of a diamond polycrystalline element, the disks are pressed from a mixture of graphite and a magnesium - zinc alloy with the following content of components in the disks, wt.%: Magnesium 15-35; dink 10-25; graphite 40-65.

In addition, to improve the bonding strength of diamond particles in the polycrystalline cell before sintering, diamond

the powder is purified from silicon dioxide.

Placement of a slurry of diamond powder in series with disks pressed from a mixture of magnesium and graphite with its content in the mixture on May 7-90. % allows

significantly reduce the formation of carbides due to the interaction of diamond particles with magnesium and thereby increase the wear resistance of the diamond polycrystalline element. This is due to the fact that magnesium located in a compressed disk placed between the layers of diamond powder, when heated, starting from 450 ° C (150-200 ° Ј lower than diamond) interacts with oxygen, which is located in the pores of the diamond

frame and deorbits from the surface of diamond particles. In this case, stable magnesium oxides are formed. Such a binding of oxygen, with a further increase in temperature, promotes the growth of isthmuses between grains and increases

strength of sintered polycrystal. In parallel with the sintering of diamond particles, the process of forming a liquid of magnesium - carbon and / or magnesium carbides with the proposed method of placement of the elements of the equipment of the reaction volume of the high-pressure apparatus (AED) is carried out | mainly in the disk due to the interaction of magnesium with graphite. Moreover, since the sintering process in the inventive cg is carried out in the region of thermodynamic stability of diamond, the graphite EL is a metastable compound and its dissolution rate in magnesium is higher compared to diamond. In this case, the migration of the melt of other unreacted magnesium to the diamond powder is substantially reduced, and the migration of the liquid occurs, and magnesium is carbon, which behaves less aggressively with respect to diamond. In this case, one should keep in mind the following circumstance. In the part of the diamond layer that is farthest from the disk before the fluid fades there, the sintering process. t of diamond powder is in the solid phase. Moreover, as is known; graphitization of diamond particles occurs, caused by the fact that the sintered diamond particles, caused by the fact that the sintered diamond particle in contact with both other particles and pores, is in a difficult stress state under the influence of high pressure and temperature, and part of it volume corresponds to the thermodynamic stability region of diamond, and part corresponds to the stability region of graphite. When the pores are filled with liquid, the pressure in the particle and around it is equalized, the barothermal conditions correspond to the stability region of diamond; therefore, graphite will dissolve with the magnesium-carbon liquid, while for diamond the speed of this process is much lower. According to the state diagram, a moment comes when further dissolution of graphite in a magnesium-carbon liquid leads to crystallization of the diamond from the Mg-C solution. When the Mg-C liquid is cooled to room temperature, depending on the concentration of carbon, it turns into a mixture of MDCa and MDC carbides, or a peritectic liquid-MgCa + diamond reaction is carried out. Thus, the wear resistance of the sintered diamond element in the claimed method is increased both due to a decrease in the dissolution of diamond and its consumption for carbide formation, and due to the process of reverse recrystallization of graphite formed on non-contact rotated xHJocTflx diamond particles into diamond.

It has been experimentally established that if the mixture is magnesium - graphite, from which the usable disks are pressed, the carbon content is less than May 7. %, then 5 there is no increase in the wear resistance of the sintered element compared to the use of pure magnesium (a comparative sample was made according to the prototype). This is due to the fact that Mg-C liquid formed in the disk migrates into the diamond layer 0 with a low carbon content, which is close in its properties to pure molten magnesium, and therefore significant losses of diamond mass are avoided

5 particles fail:

If the graphite content in the mixture exceeds 90 may. %, the amount of Mg-C liquid formed is not sufficient to fill the entire pore volume in the diamond powder layers and to increase the wear resistance in a part of the volume of the sintered semi-crystalline element not filled with liquid. : The same picture is observed in the case

.5 if the mass of the disks is less than 3.8% of the mass of the diamond powder.

Sintering parameters (temperature and pressure) are in the region of diamond stability above the graphite equilibrium line

0. - diamond in the phase diagram. The lower and upper temperature limits are determined by the region of conversion of graphite to diamond in the magnesium-carbon system. So, at a pressure of 7.7 GPa, according to the state diagram, the lower temperature limit is 1720 ° C, and the upper one is 1910 ° C. The lower limit of the sintering time is determined by the polymorphic graphite - diamond transformation time in this system and is, for example, 0 , at 1800 ° С about 15 s. The upper limit of the sintering time is governed by the structural features of the used AED and economic considerations, since the properties of diamond 5mm crystalline elements sintered in this region are practically the same. The recommended upper limit for sintering time is 1 minute. Significant diamond growth rate

0 crystals from a magnesium - carbon melt leads to the formation of sinter diamond particles of relatively large secondary irregular shape in the skeleton, which contributes to a decrease in crack resistance of diamond elements. Therefore, instead of magnesium, a magnesium-zinc alloy was used to prepare the disks, which would reduce the growth rate of diamond crystals and increase the crack resistance of the obtained polycrystalline elements if the content of the components in the disks was May.%: Magnesium 15-35; zinc 10-25; graphite 40-65%.

Both diamond and synthetic diamonds with a grain size of 0.3 to 60 microns, for example, AFM grade, can be used as diamond powders. ;

Spectral analysis studies have shown that about sixty-five percent of silica can be found in commercially available dyes of synthetic diamonds, AFM. At c) temperatures, this compound interacts with sintered diamond particles, which prevents the growth of isthmuses between them and an increase in the strength of the diamond-diamond bond. Therefore, to improve the bonding strength of diamond particles in a polycrystalline element, before sintering, the diamond powder was purified from silicon dioxide by treatment in a melt of sodium and potassium hydroxides taken in a ratio of 1: 1 for 30 minutes;

In FIG. Figures 1 and 2 show diagrams of equipping the reaction volume of an AED when sequentially placed inside a tubular graphite heater (layers of diamond powder (2) and one (Fig. 1) or two (Fig. 2) disks (3) pressed from / mixture containing magnesium and graphite At the ends of the heater, the reaction volume was closed with molybdenum gaskets (4) and sodium chloride plugs (5).

PRI me R. Magnesium powder with a particle size of about 250-500 μm and GSM-1 graphite powder were mixed in the ratio of 45 wt.% Magnesium and 55 wt.% Graphite. Weighed portions weighing 50 mg were prepared from the mixture. After that, disks with a diameter of 9 mm and a thickness of 0.5 mm were pressed at room temperature, and weighed samples weighing 450. m g were prepared from ASM diamond powder with a grain size of 40/28.

In the tubular graphite heater, which is inside the container made of liter-graph stone K, a plug was placed, which was pressure-tested from sodium chloride, the punch was pressed, and then a molybdenum gasket was placed on the plug. Then, a prepared sample of diamond powder was poured on top of the gasket. The punch made prepressing and leveling the surface of the diamond layer. On top of the diamond layer, a disk of mixtures of magnesium-graphite was placed; another sample of diamond powder was poured onto the disk. On top of the resulting diamond layer was closed with a molybdenum pad and a plug of sodium chloride. The container so equipped was placed in a toroid type pressure vessel, after which a pressure of 8.0 GPa was created in it. Then produced heating at a speed of 250 deg / s to a temperature of 180: 0 ° C. Moreover, in the temperature range 450-700 ° C

the oxygen in the pores of the diamond layer was bound to stable MgO oxide. Sintering at a temperature of 1800 ° C was carried out for 30 s. The MD-C liquid formed in the disk migrated into the diamond layer and contributed to the compaction of the diamond powder, preservation of diamond grains, and recrystallization of the formed graphite into diamond. After cooling dr room temperature

the pressure was reduced and two sintered diamond polycrystalline elements were removed from the reaction volume.

To measure the wear resistance of the elements, they were made by grinding a free abrasive plate

with a diameter of 8 mm and a thickness of 2.5 mm. For

evaluation of the wear resistance of the products proposed in the prototype, we were made

samples, according to the recommendations given in the description of US patent No. 3913280. The wear resistance of the obtained diamond polycrystalline elements for equipping the drilling and blade tools and was subsequently determined

made according to the prototype, Wear resistance of the plates was determined during the planing of a block of quartz sandstone of the Torez open pit in the Donetsk region according to the linear size (height) of the control part

areas of diamond plate wear. The plates were mechanically mounted in the tool holder. The parameters of the cutting mode when working on a cross-planing machine are as follows:

: cutting speed. 0.55m / s; cutting depth 0.5 mm; lateral feed 1.4 mm / stroke. All plate samples were tested at a cutting path length of 50 ± 1 m. Measurement of the height of the wear area was carried out using an instrumental microscope with an error of ± 0.03 mm.

The measurements showed that the wear value of the plates obtained

according to the proposed method, it is 0.20 mm, and the products obtained by the method, which is hard-pressed in the prototype — 0.44 mm. Thus, the wear resistance of diamond polycrystalline elements to equip

drilling and blade tools according to the proposed method is 2.2 times higher than products obtained by the method described in the prototype. In addition, repeated testing of plates and wear resistance after heating in hydrogen for 7 min

at a temperature of 100Q ° C showed that the wear resistance of the plates did not decrease. According to the technology described in the example, a series of experiments were carried out, the results of which are tabulated.

As can be seen from the above data, the wear resistance of elements obtained with parameters falling within the claimed ranges of values higher than the wear resistance

0

elements manufactured according to the prototype, as well as manufactured industrial stne currently. s The use of this method of manufacturing diamond semi-crystalline elements to equip drilling and blade tools by increasing their wear resistance will reduce the consumption of diamond powders by .55%.

For m; l a and b

Claims (2)

1. A method of manufacturing diamond polycrystalline elements primarily for equipping drilling and blade tools, including sintering diamond legs) of a powder in the presence of magnesium under the influence of high pressure and temperature, and the fact that, with In order to increase the wear resistance of the elements, diamond powder is placed in layers with Comparative data on the wear resistance of diamond polycrystalline elements for drilling equipment,.:;, -; ;: and blade tools . ; -, - - “Ј s PSiif K. Ј,:;; - V: cams pressed from the mixture; containing 10-93 wt.% magnesium and 7-90 wt.% graphite or from a mixture containing May 15-35. % magnesium, 10-25 wt.% zinc and 40-65 wt.% graphite, and the mass of the disks is not less than 3.8% of the mass of diamond powder, and the process is carried out in the field of thermodynamic stability of diamond. 2. The method of claim 1, wherein the diamond powder is purified from silicon dioxide before sintering.