A method of producing coatings of powder materials

 

(57) Abstract:

A method of producing coatings from powder materials includes forming a stream of carrier gas, the introduction of particles of the powder coating material, mix with the carrier gas, the feed gas-powder mixture obtained in accelerating supersonic nozzle and applying the powder material on the surface of the product gas stream, and before the introduction of the particles of the powder coating material of the carrier gas is heated and subjected to pulsed exposure, the particles of the powder coating material is mixed with a pulsating flow of carrier gas, and the application of powder coating material on the surface of the product produced in pulsed mode at a frequency of pulsation of the supersonic gas-powder jet 2-50 Hz. The method allows to reduce energy consumption, to obtain coatings with excellent physical and chemical properties, provides high utilization of the coating material. 1 C.p. f-crystals.

The invention relates to the field of coatings from powder materials, mainly from fine powders, and can be used in engineering, ship repair, electronic ority spraying of powder materials on the surface of products [1, 2].

The disadvantages of the methods are:

the presence of physico-chemical reactions between the carrier gas and particles of the coating material;

reduced adhesion of particles between themselves and the material of the product;

relatively high porosity of the coating;

small performance;

low coefficient of use of the coating material;

relatively high energy intensity;

increased risk of production;

the use of complex and expensive equipment.

A known method of producing coatings from powder materials, including the formation of flow of carrier gas, the introduction of particles of the powder coating material, mix with the carrier gas, the feed gas-powder mixture obtained in accelerating supersonic nozzle and application of powder coating material on the surface of the product gas stream [3]. The method involves the use of unheated gas, which requires a high energy consumption for the creation of high-speed gas jet for the formation of the coating.

This method is the closest analogue of the proposed method to the technical essence and the achieved result. The disadvantages with which Raskovoy mixture of 2,5 M), insufficient density, adhesion and cohesion of the formed coating, which depends on the speed of collision of the particles of the coating with the surface of workpiece.

When implementing this method is substantial loss of kinetic energy of the particles of the coating material in the parietal layer of the compressed gas at the moment of collision with the surface. This caused a significant inhibition of the particles of the coating material in a compressed parietal layer of gas formed continuously notcause on the surface supersonic flow of a carrier gas. The number of lost particles of energy when braking in a compressed parietal layer of gas depends on the density and thickness of this layer, as well as on the density, size and shape of the particles [4].

The method described in the source of information [3], is the closest analogue of the proposed method.

The essence of the proposed method lies in the fact that when it receives a coating of powder materials comprising forming a stream of carrier gas, the introduction of particles of the powder coating material, mix with the carrier gas, the feed gas-powder mixture obtained in accelerating supersonic coppered the introduction of the particles of the powder coating material of the carrier gas is heated and subjected to pulsed exposure, particles of the powder coating is mixed with a pulsating flow of carrier gas, and the application of powder coating material on the surface of the product produced in pulsed mode at a frequency of pulsations of the gas-powder jet 2 - 50 Hz. Heating the carrier gas to produce temperature determined thermophysical and mechanical properties of powder coating material, and material products.

The technical result from implementation of the proposed method is to reduce energy consumption, ensuring a high utilization rate of the coating material, the coatings with higher physico-chemical properties, in expanding the technological capabilities of the coating.

The method is as follows.

Powders of various materials with dispersion particles 5 to 50 μm is poured into the feeder-hopper particles. Gas under pressure from a source of pressure gas enters the device control parameters, where the pressure is reduced to the required level, and throttled through pipelines in the gas heater. The pulsator gas at this time is out in the open, free flowing carrier gas from the gas heater in the chamber of smashingly, temperature, speed of expiration) actuate the pulser gas supply and feeder-dispenser particles. Under the action of an alternating pulsating pressure of the heated stream of carrier gas enters the mixing chamber components where it mixes with the incoming of the feeder-dispenser powder coating material of the coating. Thus prepared mixture of particles of the coating material and the pulsating heated to a certain temperature, the carrier gas is directed into the supersonic nozzle to accelerate to the speeds required to Deposit and form a coating on the surface of workpiece.

Example 1 (metals).

Powder of aluminum (Al) dispersion of less than 30 μm is supplied from the feeder-dispenser in pulsed with a frequency of 40 Hz carrier gas, air, heated to a temperature of 450 K. In the mixing chamber to produce a mixed powder of Al with coming from the pulsator carrier gas. Pulsating gas-powder mixture is accelerated in a supersonic spreader nozzle to a velocity determined by the number Maxa M = 1,2. The supply pressure of carrier gas (air) corresponds to 5 to 105N/m2. Pulsating with a frequency of 40 Hz gas-powder mixture is sent to the surface, forming port cover H 550 MPa,

- closed porosity less than 2%,

- adhesion to the surface of the St3 more than 0.8,

- utilization of the coating material > 60%.

Example 2 (intermetallic).

A mechanical mixture of powders of iron (Fe) and aluminum (Al) in the ratio of 60% Fe + 40% Al.

The carrier gas (air) with temperature T = 520 K

The pressure of the carrier gas supply P = 6 105N/m2.

The speed of the outflow gas-powder mixture M = 1,3.

The formed coating of intermetallic Fe-Al.

The microhardness of the coating H = 1800 MPa.

Closed porosity less than 1.5%.

The adhesion of the coating to St3 higher than 0.9.

The utilization of the coating material 80%.

Example 3 (composites).

A mixture of powders of iron (Fe), aluminum (Al) and aluminum oxide (Fe2O3) in a ratio of 40% Fe + 30% Al + 30% Al2O3.

The carrier gas (air) with temperature T = 580 K

The supply pressure of carrier gas P = 6 105N/m2.

The speed of the outflow gas-powder mixture M = 1.5.

Formed composite coating of Fe-Al-Al2O3.

The microhardness of the coating H = 2100 MPa.

Closed porosity less than 1.5%.

The adhesion of the coating E. interaction of the pulsed two-phase flow with surface causes pulse abrupt increase of pressure on its surface and the formation of a shock wave. When it is reflected from the surface of the reverse movement of gas accompanied by changes of pressure and as a consequence the destruction of the shock wave. As a result of this subsequent pulse two-phase supersonic flow upon reaching the surface of workpiece is not inhibited in the compressed shock layer gas and reaches the surface of the product with a higher speed. Thus, the application of the particles of the coating material is virtually no change in their kinetic energy, which they acquired when interacting with accelerating their carrier gas.

The characteristic relaxation time parameters carrier gas and particles of the coating material, as well as the decay time of unsteady waves are of the order of 20 milliseconds. This fact predetermines the choice of operating frequencies of the carrier gas supply. When the frequency of the pulsed two-phase flow 2 f Hz 50 the braking effect of the particles of the coating material into the parietal layer is virtually absent, which allows the particles to reach the surface of the product with higher speeds. High levels of kinetic energy and shock wave loading on the material particles and the material surface causes activation of physico-chemical is Thus the proposed method of producing coatings from powder materials can reduce energy consumption, to intensify the process of applying and forming coatings and materials from a variety of powders and their mixtures at lower gas-dynamic parameters of two-phase flow, ensures a high utilization of the coating material, as a working body (accelerating gas) to use cheaper and more available gas, to improve the structure, quality and properties of the coating material, to enhance the technical and functional capabilities of the application of coatings and materials.

Sources of information taken into account:

1. Kulik, A. J., Borisov, Y. S. and other gas-dynamic spraying of composite coatings. -Leningrad: Mashinostroenie, 1985.

2. Kretschmar E. Deposition of metals, ceramics and plastics. -M.: Mashinostroenie, Moscow (1966).

3. USSR author's certificate N 1618778, class C 23 C 4/00, 1991.

4. The alchemy A. P. and other gas-dynamic spraying. Investigation of planar supersonic two-phase jet. Journal of applied mechanics and technical physics. So 38, No. 2, 1997.

5. Shormanov M. H., Kharlamov Y. A. Physico-chemical fundamentals of detonation-gas spraying. -M.: Nauka, 1978,media, the introduction of particles of the powder coating material, mix with the carrier gas, the feed gas-powder mixture obtained in accelerating supersonic nozzle and applying the powder material on the surface of the product gas stream, characterized in that before the introduction of the particles of the powder coating material of the carrier gas is heated and subjected to pulsed exposure, the particles of the powder coating material is mixed with a pulsating flow of carrier gas, and the application of powder coating material on the surface of the product produced in pulsed mode at a frequency of pulsation of the supersonic gas-powder jet 2 - 50 Hz.

2. The method according to p. 1, characterized in that the heated carrier gas to produce temperature determined thermophysical and mechanical properties of powder coating material, and material products.

 

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SUBSTANCE: apparatus includes compressed gas source, powder meter, deposition unit in the form of portable manual tool with remote control having supersonic nozzle and gas heater rigidly connected with it. Gas heater includes metallic body inside which electric and heat insulation having through mutually parallel pneumatic ducts with inserted in them heating members. Apparatus also includes pneumatic duct for feeding powder from powder meter to supersonic nozzle, locking devices and unit for controlling deposition process, said units are mutually connected through flexible pneumatic ducts and electric connection wires. According to invention electric and heat insulation of gas heater includes inner and outer cylinders coaxially arranged one inside other. Inner cylinder has central through passage for placing pneumatic duct for feeding powder from meter to supersonic nozzle. Pneumatic ducts along its periphery are in the form of grooves. Inner and outer cylinders of electric heat insulation of gas heater are made of heat resistant material having electric and heat insulated coating on surfaces restricting pneumatic ducts.

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