RU2503745C2 - Device for gas dynamic deposition of coating on part inner cylindrical surface - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed device comprises feeder-proportioner, system to feed working gas and powder particles into prechamber, replaceable radial supersonic nozzle, device drive and isolating chamber with suction system. Nozzle edge diameter is selected on the basis of the following relationship: d_ex=d_in-21_ns., where d_in is part hole diameter, l_ns is distance from nozzle edge to spayed surface making (1-10)δ_ex; δ_ex is transverse size of radial nozzle supersonic channel part at the edge. Nozzle ID is selected proceeding from:

where δ_cr is transverse size of radial nozzle supersonic channel part at nozzle throat. Note here that note here that said device allows feeding the working gas into prechamber via tangential or radial channels and powder via radial channels.

EFFECT: higher quality of coating, simplified design, expanded applications.

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Description

The invention relates to equipment for coating by the method of cold gas-dynamic spraying on the inner cylindrical surfaces of products and can be used in mechanical engineering, aerospace engineering, in the automotive industry, energy, construction, oil and gas industry and other fields of economy.

A known installation for coating inside a pipe (RF patent No. 2075535, IPC C23C 4/16, 1997), in which the spraying unit, consisting of a supersonic nozzle, a prechamber and a gas heater is mounted in a movable hollow rod, is connected by a pneumatic conduit to the powder feeder and remote control mounted on the carriage of the moving device. The gripping and rotating mechanism connecting the sprayed pipe to the insulating chamber and the suction system forms a dust-proof channel, which allows collecting and reusing excess powder.

The disadvantage of this device is that to obtain a continuous coating layer inside the pipe, it must be rotated. In this case, a spiral-shaped spraying path is obtained, and in order to obtain a continuous coating, overlapping of the spraying paths is necessary. This leads to the fact that it is difficult to obtain a uniform coating thickness along the axis of the pipe.

A device for applying onto the inner surfaces of products is also known (RF patent No. 2222639, IPC B05B 7/14, 1999). The device comprises a powder hopper with a metering feeder, a mixing chamber, a working gas supply system to the mixing chamber and a metering feeder in communication with the working gas source, as well as a spray head with an annular collector, an annular supersonic nozzle, and a rotary device that is made annular axisymmetric with respect to the central axis of the spray head, while it is located in the housing of the spray head, is interfaced and communicated with the annular supersonic nozzle, and the axis of the annular rotation of the other device, being a continuation of the axis of the annular supersonic nozzle, is located relative to it at an angle of 90 ± 5 °, and the output section of the annular rotary device is turned to the side opposite to the central axis of the spray head.

The disadvantage of this device is that the sprayed particles acquire the necessary speed and temperature in the annular supersonic nozzle, and then in the annular rotary device rotate 90 ± 5 °. In this case, the particles inevitably collide with the surface of the rotary device, which leads to a loss of their speed. In addition, the surface of the rotary device in the area of collision with particles will wear out erosively and, accordingly, the shape of the channel will change, which will lead to a change in the flow parameters and, as a consequence, the spraying conditions. The reverse erosion process can also lead to the same consequences - deposition of sprayed particles on the surface of a rotary device. In addition, the disadvantage of this device can be attributed to the fact that it is not unified - the spray head is designed for coating only a narrow range of the inner diameter of the pipe. With its significant change, another spray head is needed.

The prototype of the selected device for coating of powder materials containing a feeder-dispenser, a gas and particle supply system, a supersonic nozzle and an intermediate nozzle, characterized in that it is provided with a profiled central body located at the supersonic part of the nozzles at the outlet along their axis, and an intermediate the nozzle is placed along the axis of the supersonic nozzle in the region of the critical section of the latter (RF patent No. 2087207, IPC B05B 7/14, 1997).

The disadvantage of this device is that, as well as in the previous device, the sprayed particles must be rotated 90 ± 5 °. The turn takes place in the supersonic part of the nozzle, where the particles have already acquired high speed. Therefore, particles inevitably collide with the surface of the central body, which leads to a loss of their speed. In addition, the surface of the central body in the area of collision with particles will wear out erosively and, accordingly, the shape of the supersonic part of the nozzle will change, which will lead to a change in the outflow parameters and, as a consequence, the spraying conditions. The reverse erosion process can also lead to the same consequences - the deposition of sprayed particles on the surface of the central body. This device, as well as the previous one, is not unified - with a significant change in the inner diameter of the pipe, it is necessary to manufacture a new device.

The objective of the invention is to improve the quality of coatings on the inner cylindrical surface of products, simplifying (manufacturing) a device for gas-dynamic spraying of coatings, unification for various sizes of processed products.

The problem is solved due to the fact that the device for gas-dynamic coating on the inner cylindrical surfaces of products contains a feeder-dispenser, a system for supplying working gas and powder particles to the prechamber, a supersonic nozzle and means for moving the device inside the product, as well as an insulating chamber with a suction system, according to According to the invention, the radial supersonic nozzle is made replaceable, the dimensions of which depend on the inner diameter of the workpiece, while the diameter of the nozzle at the cut from the relation: d _ex = d _in -2l _ns ,

Where

d _in - inner diameter of the sprayed pipe;

l _ns is the distance from the nozzle exit to the sprayed surface, selected in the range (1-10) δ _ex ;

δ _ex - the transverse channel size of the supersonic part of the radial nozzle at the cut, selected from the required performance of the device,

, причем поперечный размер канала сверхзвуковой части выполнен регулируемым и может быть постоянным или переменным по радиусу, а поверхность, равноотстоящая от внутренних стенок радиального сопла расположена под углом α_n=60-90° к внутренней цилиндрической поверхности изделия. Система подачи рабочего газа в форкамеру осуществляется через тангенциальные или радиальные каналы, а подача порошка через радиальные каналы, расположенные на расстоянии l_p=(0-10)d_pr от поверхности, равноотстоящей от внутренних стенок радиального сопла.and the inner diameter of the radial supersonic nozzle, which determines the critical section area of the nozzle, from the ratio:

moreover, the transverse size of the channel of the supersonic part is made adjustable and can be constant or variable in radius, and the surface equally spaced from the inner walls of the radial nozzle is located at an angle α _n = 60-90 ° to the inner cylindrical surface of the product. The system for supplying working gas to the prechamber is carried out through tangential or radial channels, and the powder is fed through radial channels located at a distance l _p = (0-10) d _pr from the surface equally spaced from the inner walls of the radial nozzle.

Figure 1 shows a gas-dynamic spraying device with a constant transverse channel size of the supersonic part of the radial nozzle δ _n , figure 2a - tangential flow generator, 2b - radial flow generator; figure 3 shows the gas-dynamic spraying device in the context with a variable transverse channel size of the supersonic part of the radial nozzle is expanding; figure 4 shows a gas-dynamic spraying device in the context with a variable transverse channel size of the supersonic part of the radial nozzle - tapering; figure 5 - nozzle, with a surface equally spaced from the inner walls of the radial nozzle, located at an angle to the inner cylindrical surface of the product other than 90 °; Fig.6 is a graph of the region of allowed values of the transverse channel size of the supersonic part of the radial nozzle in the critical section δ _cr is the shaded area; 7 - shows a sample obtained using a radial nozzle.

The device for gas-dynamic coating on the inner cylindrical surfaces of products, comprises a housing 1, a system for supplying a working gas 2 and powder particles 3 to a housing 1, a generator 4 of swirling (I) or radial (II) flows with tangential (a) or radial (b) holes 5 working gas supply, radial holes 6 of the powder supply, prechamber 7, a radial supersonic nozzle, consisting of a fixed 8 and a moving 9 parts, means for longitudinal movement of the device inside the product (not shown). An isolation chamber with a suction system is also not shown. The radial supersonic nozzle is made replaceable, the dimensions of which depend on the inner diameter of the workpiece 10 (pipe). The diameter of the nozzle at the cut is chosen from the ratio:

d _ex = d _in -2l _ns ,

Where

d _in - inner diameter of the sprayed pipe;

l _ns is the distance from the nozzle exit to the sprayed surface, selected in the range (1-10) δ _ex ;

δ _ex - the transverse channel size of the supersonic part of the radial nozzle at the cut, selected from the required performance of the device.

The inner diameter of the radial supersonic nozzle, which determines the critical section area of the nozzle, is determined from the relation:

.

.

The radial nozzle is configured to control the transverse channel size of the supersonic part of the radial nozzle, selected from the required performance, by moving the movable part 9 of the nozzle along the thread 14, and can be constant or variable in radius, this ensures unification of the device in a wider range of sizes of sprayed products (pipes). The surface equidistant from the inner walls of the radial nozzle is located at an angle α _n = 60-90 ° to the inner cylindrical surface of the product. The change in the angle of inclination α _n due to the expansion of the functionality of the device, namely, allows you to apply coatings to the entire cylindrical surface of the blind holes (see figure 5).

The system for supplying working gas to the prechamber can be carried out through tangential or radial channels, which ensures variation of the spraying parameters. In particular, with tangential injection, the uniformity of mixing of the gas-powder mixture is improved, the trajectories of the sprayed particles inside the supersonic nozzle change, which can lead to an improvement in the quality of the sprayed coatings.

The powder is supplied through radial channels located at a distance l _p = (0-10) d _pr from the surface equally spaced from the inner walls of the radial nozzle, which ensures a variation in the temperature of the sprayed particles. In particular, particles with a low melting point must be introduced in the vicinity of the critical section of the nozzle, and with a higher one, at a considerable distance, so that when moving in the prechamber they can warm up to the temperature necessary for optimal spraying.

The gas-dynamic spraying device on the inner surface of the product operates as follows.

The working gas having a predetermined temperature and pressure is supplied from the gas heater to the nozzle assembly 1 body, then to the generator 4 of swirling (I) or radial (II) flows and through tangential (a) or radial (b) holes 5 in the fixed chamber 7 parts 8 of the radial nozzle. The gas-powder mixture from the powder dispenser through the radial holes 6 also enters the prechamber 7 of the fixed part 8 of the nozzle. Further, the entire mixture, before the critical section of the movable part 9 of the supersonic nozzle, unfolds and accelerates in the supersonic part of the nozzle moving relative to the article 10 (pipe) with a given speed ν _s , acquires the parameters necessary for spraying and forms a coating when it flows high-speed onto the inner surface of the article (pipe) eleven.

To change the nozzle, it is necessary to unscrew the lock nut 12, remove the movable part of the nozzle and unscrew the fixed part 8 of the nozzle by thread 13. Then, in the reverse order by threading, the fixed nozzle part 8 is mounted on the casing, with the necessary clearance providing the required thickness of the supersonic nozzle part, the movable nozzle part 9 is installed and fixed with a lock nut.

меньше производительности источника сжатого газа, выражением (для воздуха):The transverse channel size of the supersonic part of the radial nozzle at the cut is selected from the existing capacity of the compressed gas source and the required coating thickness in one pass. If we have a source of compressed gas providing its flow rate G _com with pressure p ₀ , the transverse channel size of the supersonic part of the radial nozzle in the critical section δ _cr is determined from the condition that the gas flow through the nozzle

less than the productivity of the source of compressed gas, the expression (for air):

where T ₀ is the gas temperature in the prechamber, p ₀ is the gas pressure in the prechamber.

For example, with a compressed gas source capacity of 2 m ³ / min, which corresponds to approximately 0.04 kg / s, a gas temperature in the prechamber of 500 K and a pressure of 1.5 MPa, the transverse channel size of the supersonic part of the nozzle in the critical section should be no more than 0, 5 mm with a critical section diameter of 10 mm and not more than 0.25 mm at 20 mm, respectively.

In addition, the critical sectional area of the nozzle should be less than the sectional area of the prechamber (at least twice). This condition can be written as:

Naturally, limiting from above the transverse size of the nozzle channel in the critical section will be more “rigid” from conditions (1) and (2).

On the other hand, the requirement to spray a coating of thickness δ _c1 in one pass leads us to the condition

where δ _c1 is the coating thickness in one pass of the nozzle assembly, ρ _c is the coating density, and k _d is the deposition coefficient.

показаны на фиг.6. Они рассчитаны при следующих значениях входящих в них параметров: G_com=0,04 кг/с, T₀=500 K, p₀=1,5·10⁶ МПа, d_cr=20·10^-3 м, d_cr=5·10^-3 м, ν_s=5·10^-2 м/с, d_in=80·10^-3 м, δ_c1=100·10^-6 м, ρ_с=2700 кг/м³, k_d=0,5. Область разрешенных значений δ_cr лежит между кривыми 3 и 1 или 2 (в рассматриваемом примере между 3 и 2).Dependencies

shown in Fig.6. They are calculated at the following values of the parameters included in them: G _com = 0.04 kg / s, T ₀ = 500 K, p ₀ = 1.5 · 10 ⁶ MPa, d _cr = 20 · 10 ^-3 m, d _cr = 5 · 10 ^-3 m, ν _s = 5 · 10 ^-2 m / s, d _in = 80 · 10 ^-3 m, δ _c1 = 100 · 10 ^-6 m, ρ _с = 2700 kg / m ³ , k _d = 0.5. The range of allowed values of δ _cr lies between curves 3 and 1 or 2 (in the considered example, between 3 and 2).

Example 1

Figure 7 shows a sample obtained using a radial nozzle with a critical section diameter of 18 mm, an outlet section diameter of 72 mm, a supersonic section length of 27 mm, and a constant transverse channel size δ _n = 0.5 mm. Aluminum powder (10-40 μm) was sprayed onto the inner surface of the pipe during a swirling flow at l _ns = 4 mm. A sample of a pipe with an inner diameter of 80 mm with an aluminum coating, p ₀ = 1.5 MPa, T ₀ = 200 ° C, a swirl generator with 32 tangential holes with a diameter of 1.5 mm.

Example 2

длина сверхзвуковой части сопла L_n может быть записана как

Меняя отношение

(

- сужающееся сопло;

- расширяющееся сопло) мы можем для выбранного диаметра трубы в определенных пределах менять длину сверхзвуковой части сопла и, тем самым, подбирать ее оптимальную конфигурацию для ускорения частиц напыляемого порошка.Subject to conditions

the length of the supersonic part of the nozzle L _n can be written as

Changing attitude

(

- tapering nozzle;

- an expanding nozzle) we can change the length of the supersonic part of the nozzle for certain pipe diameters within certain limits and, thereby, select its optimal configuration to accelerate the particles of the sprayed powder.

The positive effect of using the proposed device is ensured by the constructive solution of a replaceable nozzle with an adjustable thickness and variable nozzle geometry. Reduces the changeover time of the device when processing the inner surfaces of pipes with different diameters. Adjustable transverse channel size of the supersonic nozzle allows to unify the spraying process of a wide range of powders with different particle sizes.

Information sources

1. Patent RU No. 2075535, IPC C23C 4/16, 1997

2. Patent RU No. 2222639, IPC B05B 7/4, 1999

3. Patent RU No. 2087207, IPC B05B 7/14, 1997

Claims (1)

A device for gas-dynamic coating on the inner cylindrical surface of the product, containing a feeder-dispenser, a system for supplying working gas and powder particles to the prechamber, a supersonic nozzle and means for moving the device inside the product, as well as an insulating chamber with a suction system, characterized in that a replaceable radial supersonic nozzle, the dimensions of which are selected depending on the internal diameter of the workpiece, the diameter of the nozzle on a section selected from the _{relation: d ex = d in -2l ns} , rD d _in - diameter of the holes in the article; l _ns is the distance from the nozzle exit to the sprayed surface of the product, selected in the range (1-10) δ _ex ; δ _ex is the transverse channel size of the supersonic part of the radial nozzle in the section, and the inner diameter of the radial supersonic nozzle, which determines the critical section area of the nozzle, is selected from the relation

where δ _cr is the transverse channel size of the supersonic part of the radial nozzle in the critical section, which can be adjusted and can be constant or variable in radius, while the surface equally spaced from the inner walls of the radial nozzle is located at an angle α _n = 60-90 ° to the inner cylindrical surface of the product, and the device is configured to supply working gas to the prechamber through tangential or radial channels and to supply powder through radial channels.

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