RU2586170C1 - Device for application of coats on diamond powders - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to powder metallurgy, particularly to devices for abrasive grains, and can be used in tool making. Device consists of vacuum chamber with pumping system. Vacuum chamber accommodates rotary loading doser. Magnetron coating material sputtering system is placed in drum. Drum consists of arc-shaped plates in form of inclined cylinder. Plates partially overlap each other in one direction. In covering sections between plates gaps are maintained forming drops between surfaces of arc-shaped plates. Drops intensify mixing powder at its metallization and simplify discharging metalized powder through gaps in direction of drum rotation.

EFFECT: device allows to intensify process of diamond powders mixing, which improves quality of metal coating, as well as prevents aggregation of particles of powder and process loss of expensive diamond particles.

1 cl, 2 dwg

Description

The present invention relates to the field of vacuum coating of bulk materials: abrasive grains, granules and micropowders. The present invention can be used in tool production for metallization of diamond grains used to equip drill bits, straightening tools, tools for the construction industry and grinding wheels on metal bundles. It can also be used for metallization of diamond micropowders intended for the manufacture of grinding wheels on an organic bond.

A device for coating powder materials by spraying in vacuum, which uses a cone-shaped drum with a vertical axis of rotation to stir the powder particles (Roich N.L., Novikov N.N. Metal coating of powders by spraying in vacuum // Powder metallurgy, 1975, No. 8, Fig. 2, p. 1 ... 9). The movement of particles in this device occurs in the direction of vapor distribution along the walls of a conical vertical drum under the action of centrifugal forces. The uniformity of the coating on the particles is ensured with a sufficiently high coefficient of friction between the abrasive particles and the surface of the drum wall. It is assumed that due to high friction, the particles during the movement roll over rather than slip.

The disadvantages of this device for metallization of diamond powders are:

- low efficiency of mixing particles of diamond powder, since diamond has the lowest coefficient of friction of all known materials;

- low utilization of vapor sprayed metal;

- the complexity of the system for feeding powder particles into the deposition zone of the coating.

The invention is known according to patent RU No. 2426623, IPC B22F 1/02; B02C 17/20; C23C 14/34. According to the description of the invention, in a device for coating powder materials by spraying in vacuum, the process of mixing the powder particles is carried out in a conical drum with an inclined axis of rotation.

The conical drum is assembled from arcuate conical segments partially overlapping each other in the same direction with a soaking gap between them, creating differences between the surfaces of the segments to intensify the process of mixing the powder during rotation of the drum in one direction and providing unloading of the metallized powder when changing the direction of rotation. To enhance the intensification of the mixing process, an additional movement is reported to the powder particles - periodic reciprocating movement along the surfaces of the conical segments. For this purpose, during rotation, producing straight lines of arched conical segments alternately form different angles in the lower part of the drum relative to the horizontal plane: + α; 0; -α; 0.

The disadvantage of this device is that increasing the dispersion of the processed powder causes the spread of a certain mass of particles beyond the wide open conical drum having an inclined axis of rotation.

Closest to the proposed invention is a device for coating powder particles by vapor deposition of molten metal in a vacuum, in which a rotating cylindrical drum with a horizontal axis of rotation is used to mix the powder material. (Roikh NL, Novikov NN The deposition of metal coatings on powders by spraying in vacuum // Powder Metallurgy, 1975, No. 8, Fig. 1, p. 1 ... 9).

The device consists of a vacuum chamber, pumping means and an evaporator located inside a cylindrical drum. In a rotating cylindrical drum, the process of mixing the powder occurs in the lower part. To intensify the process of mixing the powder particles, blades are used.

The disadvantages of this device for the metallization of diamond powders include:

- uneven coating on the powder grains, since the density of the deposited vapor of molten metal from the evaporator in different directions is different (especially along the axis of the drum);

- a decrease in the quality of metallization of the powder with increasing dispersion of its particles, due to the aggregation (sticking) of small grains during the formation of a metal coating in a vacuum;

- the absence of mechanisms for replacing the treated mass of powder in the drum with the next portion without depressurization of the vacuum chamber.

Metallization of diamond powders in a vacuum has its own characteristics. The refractory carbide-forming metals used for coating activate phase changes in diamond in the manufacture of a tool on a metal bond. Therefore, on the one hand, their presence has a very negative effect on the thermal stability of diamond during the manufacturing and operation of the tool. On the other hand, their presence in the form of small additives helps to increase the reliability of diamond fixing in the tool matrix. Based on this, the coating on all diamond grains should have a strictly defined thickness (within the acceptable range).

The basis for ensuring uniform coating uniformity on all diamond grains is the method and quality of mixing the powder. The degree of intensification of the mixing process is determined by many conditions, the main of which are:

- physical and mechanical properties, mass and shape of powder particles;

- design features of the installation;

- vibration parameters.

Among superhard materials, diamond has the highest hardness and the highest normal elastic modulus (Young's modulus), therefore, its particles are more responsive to changes in the design of the vibration device and vibration parameters than particles from other powder materials. In addition, diamond powder, like others, consists of different fractions, which significantly enhances the dispersion of its particles in shape, size and weight. It is necessary to add that the particles (grains) of industrial diamonds have irregular geometric shapes. Therefore, to control the mixing process and ensure uniform coating on the particles, it is preferable to limit the weight of the diamond powder in order to optimize (minimize) the thickness of its layer in the coating zone and to ensure a uniform state of the particles during metallization. Due to the strict restriction of the weight of the processed diamond powder in vacuum, it is advisable to use a device for periodically supplying the dosed diamond powder to the drum and making it possible to discharge the processed powder from it without depressurizing the vacuum chamber.

The objectives of the invention are:

- increasing the uniformity and uniformity of a strictly dosed coating on powder particles in order to improve the operational characteristics of diamond tools;

- the exclusion of aggregation of powder particles by increasing the intensity of mixing;

- ensuring the loading of diamond powder into the drum and its unloading without depressurization of the vacuum chamber.

Improving the uniformity of the coating in the proposed device is provided:

- periodic circulation of all powder particles through metal vapor deposition zones having different coating formation rates due to the inhomogeneous density of the deposited particles;

- forced rotation of the powder particles due to their movement simultaneously along the generatrix of the inclined cylinder (drum) and along the circumference of its rotation.

An exception to the process of particle aggregation is achieved by a combination of the effects of two movements: forced rotation and their frequent periodic collision with the surface of a rotating drum, due to the presence of drops on its surface. The variety of geometric shapes and sizes of diamond grains (hence, masses) causes different trajectories of their motion upon impact with a spherical surface, since the resulting interaction forces are different in magnitude and direction.

Periodic dosed loading of samples of diamond powder into a device for mixing its particles is provided by a rotary batcher with cells.

The device (Fig. 1) contains a working chamber 1 with a pumping system.

A loading rotor batcher 2 and a magnetron coating material spraying system are placed in the chamber. The dispenser is made in the form of a disk with cells 3. The bases of 4 cells are spring-loaded with leaf springs 5, which open when the disk rotates under the influence of rollers (cams) 6 on the bracket installed at the unloading position. The magnetron system, consisting of a magnetron 7 with atomized material 8 and the anode 9, is placed inside the drum 10, made in the form of an inclined cylinder. The magnetron and anode are cooled by running water. The drum 10 is assembled from arcuate plates 11 overlapping each other in the same direction (Fig. 2). In places of overlap between the plates, gaps are created A. Arcuate plates are made of coating material. Under the drum 10 is a collection 12.

The device operates as follows. Strictly metered weights of diamond powder are loaded into the cells 3 of the rotary dispenser 2 and a vacuum is created in the chamber 1 in the range from 5 · 10-4 to 10-4 Pa. Then, by discharging argon through a needle leakage, a working vacuum of 0.01 Pa is established and kept constant.

The inclined drum 10 is driven in rotation from a DC motor 13 through a bevel gear. At low speeds of the drum 10, the handle 14 displays one of the cells 3 of the rotary dispenser 2 at the unloading position. The roller of the bracket 6, overcoming the force of the leaf spring 13, opens the base 4 of the cell 3 and the powder enters the drum 10. The optimal frequency of rotation of the drum is established by observing the mixing process through the viewing window 15. A high negative voltage is applied to the magnetron 7 relative to the anode 9.

The process of mixing the powder occurs at the bottom of the drum. When the inclined drum 10 rotates, its generatrix lines periodically create various tilt angles with respect to the horizontal plane in the range from + α to -α. This design solution contributes to the periodic reciprocating movement of the powder along the generatrix lines of the inclined drum. Different sections of the magnetron (cathode) have different spraying intensities of the coating material. The circulation of all powder particles through these zones contributes to the formation of uniform coatings on them. In addition, the simultaneous movement of polyhedral diamond particles (having irregular geometric shapes) around the circumference and along the generatrix lines of the rotating inclined drum contributes to their rolling over the surface of the arcuate plates. This significantly increases the uniformity of the coating on different faces of the particles and enhances the process of intensification of their mixing.

The mixing process is intensified by the differences between the working surfaces of the plates. The combined effect of the rotational movement of the particles and their frequent periodic collision with the spherical surface of the rotating drum excludes the possibility of aggregation.

After completion of the metallization process, the direction of rotation of the drum is changed and the powder is poured through the gaps Δ between the arcuate plates into the collector 12.

Testing of diamond cutting wheels equipped with metallized polycrystalline diamonds of the ARS-4 grade with a grit of 250/200 when processing marble showed a decrease in specific consumption of diamond (in carats) per 1 m ² of cutting area by 23.8%, and an increase in specific productivity by 37.4 %

Claims (1)

A device for coating diamond powders containing a magnetron system for spraying the coating material located inside the drum for mixing the powder, and a pumping system, characterized in that it is equipped with a loading rotary dispenser made in the form of a disk with cells for periodically loading hanging diamond powders, and the drum is made in the form of an inclined cylinder, providing periodic circulation of powder particles through the deposition zone of the coating collected from the arcuate plates, partially rekryvayuschih each other in one direction and having gaps in the areas of overlap, creating differences between their surfaces.

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