CN111715489A

CN111715489A - Method for spraying abradable coating on large-size cylindrical part

Info

Publication number: CN111715489A
Application number: CN202010619842.0A
Authority: CN
Inventors: 于月光; 刘建明; 章德铭; 张鑫; 沈婕; 侯伟骜; 刘通; 郭丹
Original assignee: Bgrimm Advanced Materials Science & Technology Co ltd; BGRIMM Technology Group Co Ltd
Current assignee: Bgrimm Advanced Materials Science & Technology Co ltd; BGRIMM Technology Group Co Ltd
Priority date: 2020-07-01
Filing date: 2020-07-01
Publication date: 2020-09-29
Anticipated expiration: 2040-07-01
Also published as: CN111715489B

Abstract

The invention relates to a method for spraying an abradable coating on a large-size cylindrical part. The method comprises the following steps: (1) providing a cylindrical inner wall to be sprayed, and determining a circular plane in a space formed by enclosing the cylindrical inner wall; (2) providing a spray gun combination mechanism, wherein the spray gun combination mechanism comprises a coating spray gun, a first air flow spray gun, a second air flow spray gun and a third air flow spray gun; (3) and arranging relative positions (4) of the paint spray gun, the first air flow spray gun, the second air flow spray gun and the third air flow spray gun and the cylindrical inner wall to enable the cylindrical inner wall and the spray gun to be combined to rotate relatively around the axis, wherein the paint spray gun, the first air flow spray gun, the second air flow spray gun and the third air flow spray gun sweep the surface to be sprayed on the cylindrical inner wall in the rotating process.

Description

Method for spraying abradable coating on large-size cylindrical part

Technical Field

The invention relates to the field of thermal spraying, in particular to a method for spraying an abradable coating of a large-size cylindrical part.

Background

Seal coatings, also known as gap control coatings or seal coatings, are coatings used to control the running clearances of mechanical parts. The abradable seal coating is a soft coating that is sprayed on the stator that mates with the rotating component to allow abrasion. Can be prepared by thermal spraying (such as plasma spraying and flame spraying).

The abradable seal coating generally includes a carcass component and an abradable component. The skeletal component may be a metal or ceramic. The abradable component may be selected from one or more of graphite, boron nitride and polyphenyl esters. The abradable seal coating may be composed of aluminum silicon-polyester, aluminum-boron nitride, aluminum-graphite, aluminum bronze-polyester, copper aluminum-boron nitride, nickel-graphite, nickel copper-boron nitride, nickel copper aluminum-boron nitride, nickel chromium aluminum-bentonite, nickel chromium iron aluminum-boron nitride, nickel-diatomaceous earth, nickel chromium aluminum-diatomaceous earth, and the like.

Disclosure of Invention

The inventor finds that in the spraying construction of the inner wall abradable coating of a large-size (such as the diameter is more than 500mm) cylindrical piece (such as the length-diameter ratio is more than or equal to 0.5), a large number of surface appearances such as bulges, pimples and the like exist on the surface of the coating after spraying, and the defects such as pits and the like are left on the surface of the coating after turning, so that the technical requirements of a precision power device on the abradable coating cannot be met.

In order to solve the above problems, the inventors have carried out a lot of work to study the main causes of the formation of "bulge", "pimple" and the like in the spraying process of large-sized cylindrical parts, and proposed an innovative formation mechanism of the coating defect as follows:

the cylindrical inner wall is enclosed to form a space with closed periphery, and the spraying is carried out in the closed space. The abradable coating material contains large-size abradable component particles (such as polyphenyl ester with the particle size of 100-250 mu m, boron nitride, graphite and the like), and during spraying, rebounded unmelted particles and particles such as smoke dust and the like generated by burning loss of the material exist, and the particles are easy to adhere to the surface to be sprayed, so that pollutants and defects in the coating are caused. In addition, for large cylindrical parts, due to the large diameter of the workpiece revolution, the longer distance and time between two sprays of the same spray surface are required, which exacerbates the contamination and defects in the coating. Meanwhile, the large-size barrel-shaped part is deep and has a large length-diameter ratio (more than or equal to 0.5), and smoke generated in the abradable spraying process floats near the spraying surface to form secondary pollution. In addition, the abradable coating also has the characteristics of thick spraying thickness (generally over 2mm) and long spraying time (more than 10 times of the spraying time of other coatings such as oxidation resistance, wear resistance and the like), and the spraying defects such as bulging, pimples and the like are particularly remarkable on the abradable coating.

Based on the above-described innovative recognition of the defect formation mechanism, the present disclosure provides an innovative method of spraying an abradable coating on a cylindrical inner wall, the method comprising:

(1) providing a cylindrical inner wall to be sprayed, and determining a circular plane in a space formed by enclosing the cylindrical inner wall, wherein the circular plane is vertical to the axis of the cylindrical inner wall, the circle center O of the circular plane is positioned on the axis, and the radius of the circular plane is equal to that of the cylindrical inner wall;

(2) providing a spray gun combination mechanism, wherein the spray gun combination mechanism comprises a coating spray gun, a first air flow spray gun, a second air flow spray gun and a third air flow spray gun, the coating spray gun is used for spraying coating and flame flow, the first air flow spray gun, the second air flow spray gun and the third air flow spray gun are respectively used for spraying purging air flow, and the coating spray gun, the first air flow spray gun, the second air flow spray gun and the third air flow spray gun are fixed in relative positions;

(3) the relative positions of the paint spray gun, the first air flow spray gun, the second air flow spray gun and the third air flow spray gun and the cylindrical inner wall are set to satisfy the following conditions i) to iii):

i) the coating spray gun, the first air flow spray gun, the second air flow spray gun and the third air flow spray gun are all positioned on the circular plane determined in the step (1), and spray drop points are respectively formed on the edges of the circular plane and are respectively marked as a drop point T, a drop point A, a drop point B and a drop point C;

ii) on the edge of the circular plane, the falling point A and the falling point B are respectively positioned AT two sides of the falling point T, an arc AT and an arc BT are formed on the edge of the circular plane, the length of the arc AT is 2-4 flame spot diameters, and the length of the arc BT is 2-4 flame spot diameters; the diameter of the flame spot is the width of a strip-shaped coating mark formed when the coating spray gun sweeps through a region to be sprayed on the cylindrical inner wall; and

iii) the included angle between the line OC and the line OT is 30-180 degrees (for example, 150-180 degrees), and the line OC and the line OT are respectively the connection line between the circle center O and the drop point C and the drop point T;

(4) the cylindrical inner wall and the spray gun combination mechanism rotate relatively around the axis, and in the rotating process, the coating spray gun, the first air flow spray gun, the second air flow spray gun and the third air flow spray gun sweep the surface to be sprayed on the cylindrical inner wall, wherein the coating spray gun sprays flame flow containing coating components to the cylindrical inner wall, and the first air flow spray gun, the second air flow spray gun and the third air flow spray gun spray sweeping air flow to the cylindrical inner wall;

and in the spraying process, a dust suction device is used for sucking and removing dust below a space formed by enclosing the cylindrical inner wall.

In some embodiments, the suction opening of the suction device is located on the central axis of the cylindrical inner wall. In this regard, the gas flow is primarily centered within the cylindrical inner wall and does not adversely affect the temperature and velocity fields of the spray flame stream.

The innovative concept of the present disclosure lies in: the surface to be sprayed is cleaned through a specific air flow blowing process. For example, in a primary spraying process, with the relative rotation of the cylindrical inner wall and the spray gun combination mechanism, the spray guns of the spray gun combination mechanism sequentially perform the following treatment on the cylindrical inner wall:

(1) the first air flow spray gun performs first surface sweeping on the surface to be sprayed, and the main purpose is to provide a clean surface to be sprayed;

(2) the coating spray gun sprays flame flow containing coating to the surface to be sprayed;

(3) the second air flow spray gun performs secondary blowing on the surface which is just sprayed, and the main purpose is to avoid the combination of pollutants and the surface which is just sprayed and has higher temperature;

(4) the third air flow spray gun performs three times of blowing and cooling on the spraying surface treated in the previous step, and mainly aims to remove the adhesion of large-size rebound particles to the surface to be sprayed;

(5) the dust suction device arranged below the cylindrical part forms air flow from top to bottom by sucking dust, and 50-200 mu m spraying pollutants suspended in the inner cavity of the casing are removed in real time.

The experimental data prove that: the falling points of the first air flow spray gun and the second air flow spray gun on the spraying surface are required to be 2-4 flame spot diameters away from the falling point of the coating spray gun on the spraying surface. Too close a distance disturbs the temperature and velocity fields of the spray flame, leading to a decrease in the temperature of the flame and to a disturbance of the trajectory of the sprayed material, whereas too far a distance does not function to clean the surface and still produces a large number of defects in the coating.

The experimental data prove that: the application of only the 1 st and 2 nd air flows is not sufficient to stably remove the spray defects, particularly the large-sized defects, in the coating layer, which are mainly caused by the large-sized rebound particles of 200 μm to 500 μm. The third air flow spray gun is arranged in the range that the included angle between the OC and the connecting line OT is more than 30 degrees, so that the defect caused by the large-size rebound particles can be effectively eliminated.

The characteristics act synergistically to play an unexpected improvement effect on the surface quality of the coating.

In some embodiments, the first air flow lance has a nozzle diameter of 4mm to 5mm, a nozzle distance from the cylindrical inner wall of 50mm to 200mm (e.g., 60 to 100mm), and an air jet pressure of 0.3MPa to 0.7 MPa. The diameter of the nozzle of the second air flow spray gun is 4 mm-5 mm, the distance between the nozzle and the cylindrical inner wall is 50 mm-200 mm (for example, 60-100 mm), and the pressure of the sprayed air flow is 0.3 MPa-0.7 MPa. The diameter of the nozzle of the third air flow spray gun is 10 mm-25 mm, the distance between the nozzle and the cylindrical inner wall is 30 mm-200 mm, and the pressure of the sprayed air flow is 0.9 MPa-1.5 MPa. Experimental data have shown that the above-mentioned specific parameter settings are very advantageous for obtaining a smooth and even coating.

In some embodiments, the rotation is clockwise uniform relative motion or counterclockwise uniform relative motion.

In some embodiments, the first air flow lance, the paint lance, the second air flow lance, and the third air flow lance sequentially sweep the area to be painted on the annular inner wall as the annular inner wall rotates relative to the lance assembly.

In some embodiments, the lance assembly is held stationary and the cylindrical inner wall rotates in comparison to the lance assembly. For example, a cylindrical inner wall may be provided on the turntable.

In some embodiments, the lance assembly mechanism is rotated in comparison to the cylindrical inner wall while the cylindrical inner wall is held stationary.

In some embodiments, a paint spray gun includes a flame gun and a powder delivery device. A flame gun may be used to inject the plasma flame stream. The powder delivery apparatus may be used to provide coating powder to the plasma flame stream.

In some embodiments, the plasma spray system includes a spray power supply, a spray gun, a control device, a gas supply system, a powder feeding device, and a cooling water supply device.

In some embodiments, the spray nozzle of the paint spray gun is spaced from 80 to 120mm from the cylindrical inner wall.

In some embodiments, the flame spot diameter is 6 to 25mm, such as 6 to 10mm, such as 8 mm.

In some embodiments, the cylindrical inner wall and lance combination are moved relative to each other in the axial direction during the spraying process. Based on this, the spray gun can fully cover the surface to be sprayed in the axial direction of the cylindrical inner wall.

In some embodiments, the composition of the gas streams injected by the first gas flow lance, and the third gas flow lance are each independently air, nitrogen, an inert gas, or a combination thereof.

In some embodiments, the coating material sprayed by the paint spray gun is an abradable coating material that includes a backbone component and an abradable component.

In some embodiments, the matrix component may contain a metal powder or a ceramic powder.

In some embodiments, the skeleton component is an aluminum-silicon alloy, and preferably, the weight ratio of the aluminum element to the silicon element is 30-40: 5 to 10.

In some embodiments, the abradable component contains one or more selected from graphite, boron nitride, and polyphenyl esters.

In some embodiments, the abradable component is a resin powder, such as a polyester powder, such as an aromatic polyester powder, such as a polyphenylene ether powder.

In some embodiments, the composition of the abradable coating paint may be aluminum silicon-polyester, aluminum-boron nitride, aluminum-graphite, aluminum bronze-polyester, copper aluminum-boron nitride, nickel-graphite, nickel copper-boron nitride, nickel copper aluminum-boron nitride, nickel chromium aluminum-bentonite, nickel chromium iron aluminum-boron nitride, nickel-diatomaceous earth, or nickel chromium aluminum-diatomaceous earth.

In some embodiments, the composition of the abradable coating paint includes 40 to 60 wt% (e.g., 60 wt%) of the backbone component and 30 to 50 wt% (e.g., 40 wt%) of the abradable component.

In some embodiments, the abradable coating also means a binder, the binder being present in an amount of 10 to 20 wt.%.

In some embodiments, the paint spray gun is a flame spray gun or a plasma spray gun.

In some embodiments, the distance between the inner cylindrical wall of the paint spray gun, the first air flow spray gun, the second air flow spray gun and the third air flow spray gun is less than the radius of the inner cylindrical wall.

In some embodiments, the radius of the cylindrical inner wall is greater than 250mm, such as greater than or equal to 500mm, such as 250-1000 mm.

In some embodiments, the cylindrical inner wall has an aspect ratio greater than or equal to 0.5, such as greater than or equal to 1. The aspect ratio refers to the ratio of the length to the diameter of the cylindrical inner wall. The length of the cylindrical inner wall refers to the dimension parallel to the central axis.

In some embodiments, the cylindrical inner wall is substantially perpendicular to the ground during spraying.

In some embodiments, the central axis of the cylindrical inner wall is substantially perpendicular to the ground surface during spraying.

In some embodiments,% refers to wt%.

In some aspects, a component is provided having a cylindrical inner wall, the surface of the cylindrical inner wall being sprayed with an abradable coating, the abradable coating being sprayed by a method of any of the present disclosure.

In some embodiments, the spray direction of the spray gun is substantially perpendicular to the spray face, e.g., at an angle of 90 ± 10 °, e.g., 90 ± 5 °, e.g., 90 ° to the spray face.

In some embodiments, the spray direction of the first and second air flow spray guns is parallel to the spray direction of the paint spray guns.

In some embodiments, the cylindrical inner wall is made of metal.

In some embodiments, the abradable coating has a thickness of 1 to 3mm, such as 1.5 to 2.5 mm.

In some embodiments, a base coating is sprayed on the cylindrical inner wall surface prior to spraying the abradable coating. The composition of the base coating is primarily metal. The function of the substrate coating may be to improve the corrosion resistance of the substrate, to improve the bonding force of the abradable coating to the substrate, etc.

Description of the terms

"flame blasting" means melting a spray material (wire or powder) by the high temperature of a gas combustion flame and spraying it onto the surface of a workpiece with a compressed air flow to form a coating.

The term "plasma spraying" means that a nozzle is used to spray a plasma flame stream, a carrier gas is used to feed metal or nonmetal powder into the plasma flame stream, the plasma flame stream is heated to a molten or semi-molten state, and the plasma flame stream is sprayed and deposited on the surface of a pretreated substrate along with the high-speed plasma flame stream to form a coating.

By "cylindrical member" is meant a workpiece having a cylindrical inner wall.

The cylindrical inner wall is an inner wall which encloses a cylindrical or truncated cone-shaped cavity, and the central axis of the cylindrical or truncated cone-shaped cavity is the central axis of the cylindrical inner wall.

By spray gun to spray surface distance is understood the distance of the spray gun nozzle to the spray surface.

"flare diameter" refers to the width of the stripe of coating impression formed by the paint spray gun as it sweeps across the area of the cylindrical inner wall to be painted.

The included angle can range from 0 to 180.

"comprising" may mean a content of more than zero, for example more than 10%, for example more than 20%, for example more than 30%, for example more than 40%, for example more than 50%, for example more than 60%, for example more than 70%, for example more than 80%, for example more than 90%, for example 100%. When the content is 100%, the meaning of "containing" is equivalent to "consisting of …".

Advantageous effects

The disclosed methods or products have one or more of the following advantages:

(1) the abradable coating obtained by the spraying method has a smooth and flat surface, has no spraying defects such as ' bulges ', pimples ' and the like, and has the surface roughness of not more than 8 mu m;

(2) the spraying method is relatively simple and has strong operability;

(3) the spraying method has low cost.

Drawings

FIG. 1 shows a titanium alloy cylindrical member;

FIG. 2 is a schematic illustration of a plasma spray process;

FIG. 3 is a photograph of the surface of the coating of example 1;

fig. 4 is a photograph of the surface of the coating of comparative example 1.

Detailed Description

Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Example 1

Fig. 1 shows a titanium alloy cylindrical member 10 of TC4 titanium alloy. The titanium alloy cylindrical member 10 has a top diameter of 810mm, a bottom diameter of 600mm, a height of 620mm, and a thickness of 7.6 mm. The titanium alloy cylindrical member 10 has a cylindrical inner wall 110, the top radius of the cylindrical inner wall 110 being 397.4mm and the bottom radius being 292.4 mm. Cylindrical inner wall 110 has a central axis 15. A spray gun combination mechanism 3 is arranged in a space formed by the surrounding of the cylindrical inner wall 110.

The bucket 10 is mounted on a turntable 40. The turntable 40 is provided with a hollow shaft 41 with the diameter of 250mm, and the lower outlet of the hollow shaft 41 is connected with the dust suction device 50. The dust suction device 50 discharges the smoke by sucking the air. When the vacuum cleaner 50 sucks in, the airflow 60 enters from the upper end opening of the tub 10, exits from the lower end opening, and enters the vacuum cleaner 50 through the hollow shaft 41.

Figure 2 shows a schematic of the present embodiment for spraying an abradable coating on a spray cylindrical inner wall using the spray gun assembly of the present disclosure.

As shown in fig. 2, a circular plane 111 is defined in the space enclosed by the cylindrical inner wall 110, the circular plane 111 is perpendicular to the central axis 15 of the cylindrical inner wall, the center O of the circular plane 111 is located on the central axis 15, and the radius R of the circular plane 111 is equal to the radius of the cylindrical inner wall 110. The spray gun assembly 3 is located in the space enclosed by the cylindrical inner wall 110.

The spray gun assembly 3 includes a paint spray gun 30, a first air flow spray gun 31, a second air flow spray gun 32, and a third air flow spray gun 33. Paint spray gun 30 is used to spray paint and flame streams, first air spray gun 31, second air spray gun 32 and third air spray gun 33 are used to spray purge air streams, respectively, and paint spray gun 30, first air spray gun 31, second air spray gun 32 and third air spray gun 33 are fixed in position relative to each other.

The paint spray gun 30 of the spray gun combination mechanism 3 comprises a plasma flame gun (GTV-F6) and a powder feeding device. The spray direction of the paint spray gun 30 is perpendicular to the annular inner wall 110.

Wherein, the diameter of the nozzle of the first air flow spray gun 31 is 4.5mm, the distance between the nozzle and the spraying surface is 120mm, the spraying direction of the nozzle is basically parallel to the spraying direction of the coating spray gun, and compressed air is used as an air supply source (oil is less than or equal to 0.1 mg/cm)³Water vapor less than or equal to 600mg/cm³The particle size is less than or equal to 5 microns, the temperature is 20-25 ℃, and the air supply pressure is 0.55 MPa.

Wherein the diameter of the nozzle of the second air flow spray gun 32 is 4.5mm, the distance between the nozzle and the spraying surface is 120mm, the spraying direction of the nozzle is basically parallel to the spraying direction of the coating spray gun, and compressed air is used as an air supply source (oil is less than or equal to 0.1 mg/cm)³Water vapor less than or equal to 600mg/cm³The particle size is less than or equal to 5 microns, the temperature is 20-25 ℃, and the air supply pressure is 0.55 MPa.

Wherein the third gasThe nozzle diameter of the flow spray gun 33 is 15mm, the nozzle is 50mm away from the spraying surface, and the spraying direction of the nozzle is basically parallel to that of the coating spray gun; compressed air is used as an air supply source (oil is less than or equal to 0.1 mg/cm)³Water vapor less than or equal to 600mg/cm³The particle size is less than or equal to 5 microns, the temperature is 20-25 ℃, and the air supply pressure is 1.2 MPa.

Further, the relative positions of the paint spray gun 30, the first air flow spray gun 31, the second air flow spray gun 32, and the third air flow spray gun 33 to the cylindrical inner wall 110 satisfy the following conditions i) to iii):

i) the paint spray gun 30, the first air flow spray gun 31, the second air flow spray gun 32 and the third air flow spray gun 33 are all positioned on the circular plane 111, and spray drop points are respectively formed on the edges of the circular plane 111 and are respectively marked as a drop point T, a drop point A, a drop point B and a drop point C;

ii) on the edge of the circular plane, the falling point A and the falling point B are respectively positioned AT two sides of the falling point T, an arc AT and an arc BT are formed on the edge of the circular plane, the length of the arc AT is 3 flame spot diameters, and the length of the arc BT is 3 flame spot diameters; the diameter of the flare spot is the width of a strip-shaped coating mark formed when the coating spray gun 30 sweeps through a region to be sprayed of the cylindrical inner wall 110, and the diameter of the flare spot is 8mm in the example; and

and iii) the included angle between the connecting line OC and the connecting line OT is 180 degrees, and the connecting line OC and the connecting line OT are respectively connecting lines of the circle center O and the drop point C and the drop point T.

The lance combination 3 and the cylindrical inner wall 110 are arranged as described above. During the spraying process, the cylindrical inner wall 110 rotates around the central axis 15 at a rotational speed of 45 rpm. The spray gun combination mechanism 3 also moves up and down along the direction parallel to the central axis 15 in the spraying process, and the moving speed is 4 mm/s.

In the spraying process, the dust collection fan is started, and the air exhaust volume of the dust collection fan is 4500m³/h。

Specifically, the inner wall 110 of the titanium alloy cylindrical member 10 described above is sprayed by the following steps.

(1) Surface preparation

And cleaning the cylindrical inner wall 110 by using alcohol to remove oil, protecting a non-spraying surface by using a high-temperature adhesive tape, and performing sand blowing coarsening on the to-be-sprayed surface of the inner wall of the cylindrical part by using 60-mesh alumina gravel, wherein the sand blowing pressure is 0.2 MPa.

(2) Spray coating of base coat (bottom layer)

Nickel-aluminum powder (produced by Beijing mining and metallurgy science and technology group, the aluminum element content is 5 percent, the nickel element content is 95 percent, and the brand is KF-6) is taken as bottom layer coating powder.

During the spraying process, the parameters of the paint spray gun 30 include: argon flow 45lpm, hydrogen flow 6lpm, current 550A, voltage 67.5kW, powder feeding speed 30g/min, powder feeding gas flow 4.5lpm, distance of a coating spray gun from a spraying surface is 140mm, and bottom layer spraying thickness is 0.12 mm.

The first air flow gun 31, the second air flow gun 32 and the third air flow gun 33 are not turned on during the spraying process.

(3) Spray coating of abradable coatings (surface layer)

The wearable coating is sprayed by using the spray gun combination mechanism and the spraying method disclosed by the invention by taking aluminum silicon boron nitride powder (manufactured by Beijing mining and metallurgy science and technology group, the brand number is KF-121, the content of aluminum element is 63.36%, the content of silicon element is 8.64%, the content of boron nitride is 20% and the binder is 8%) as surface layer coating powder.

During the spraying process, the parameters of the paint spray gun 30 include: the flow rate of argon is 60lpm, the flow rate of hydrogen is 6lpm, the current is 430A, the voltage is 72kW, the powder feeding speed is 57g/min, the flow rate of powder feeding gas is 4.5lpm, and the distance between a paint spray gun and a spraying surface is 170 mm. The spraying thickness of the surface layer is 1.8 mm.

The first air flow lance 31, the second air flow lance 32 and the third air flow lance 33 are opened during the spraying process.

(4) And after spraying is finished, removing the protective adhesive tape in the non-spraying area.

Comparative example 1

Comparative example 1 differs from example 1 in that step (3) does not turn on the first air flow gun 31, the second air flow gun 32 and the third air flow gun 33 during spraying.

Analytical testing

FIG. 3 shows a photograph of the appearance of the spray-coated alumino-silicate polyester coating of example 1, without visually observable spray defects, measured as a coating surface roughness of not more than 8 μm. This significantly improved coating surface quality was unexpected to those skilled in the art.

FIG. 4 shows a photograph of the appearance of the Al-Si-PS coating prepared in comparative example 1, which shows a large number of spraying defects in the form of lumps, and the roughness of the coating surface is measured to be as high as 64 μm.

The above analysis and detection results show that the abradable coating prepared by the method disclosed by the invention has a smooth and flat surface and shows a remarkably improved surface quality.

While specific embodiments of the invention have been described in detail, those skilled in the art will understand that: various modifications may be made in the details within the teachings of the disclosure, and these variations are within the scope of the invention. The full scope of the invention is given by the appended claims and any equivalents thereof.

Claims

1. A method of applying an abradable coating to a cylindrical inner wall, comprising:

(2) providing a spray gun assembly comprising a paint spray gun for spraying paint and flame streams, a first air flow spray gun, a second air flow spray gun and a third air flow spray gun for spraying a purge air stream, respectively, the paint spray gun, the first air flow spray gun, the second air flow spray gun and the third air flow spray gun being fixed in position relative to one another;

ii) on the edge of the circular plane, the falling point A and the falling point B are respectively positioned AT two sides of the falling point T, an arc AT and an arc BT are formed on the edge of the circular plane, the length of the arc AT is 2-4 flame spot diameters, and the length of the arc BT is 2-4 flame spot diameters; the flame spot diameter refers to the width of a strip-shaped coating mark formed when the coating spray gun sweeps across the cylindrical inner wall; and

iii) the included angle between the connecting line OC and the connecting line OT is 30-180 degrees, and the connecting line OC and the connecting line OT are respectively the connecting lines of the circle center O and the drop point C and the drop point T;

(4) rotating the cylindrical inner wall and the spray gun assembly relative to each other about the axis, wherein during the rotation, the paint spray gun, the first air flow spray gun, the second air flow spray gun and the third air flow spray gun sweep a surface to be painted on the cylindrical inner wall, wherein the paint spray gun sprays a flame flow containing paint components to the cylindrical inner wall, and the first air flow spray gun, the second air flow spray gun and the third air flow spray gun spray a purge air flow to the cylindrical inner wall;

2. The method according to claim 1, having the following features:

the nozzle diameter of the first airflow spray gun is 4-5 mm, the distance between the nozzle and the cylindrical inner wall is 50-200 mm, and the pressure of the sprayed airflow is 0.3-0.7 MPa;

the diameter of a nozzle of the second air flow spray gun is 4 mm-5 mm, the distance between the nozzle and the cylindrical inner wall is 50 mm-200 mm, and the pressure of the sprayed air flow is 0.3 MPa-0.7 MPa;

the diameter of the nozzle of the third air flow spray gun is 10 mm-25 mm, the distance between the nozzle and the cylindrical inner wall is 30 mm-200 mm, and the pressure of the sprayed air flow is 0.9 MPa-1.5 MPa.

3. The method of claim 1, having one or more of the following features:

-the paint spray gun comprises a flame gun and a powder feeding means;

the distance between the nozzle of the paint spray gun and the cylindrical inner wall is 80-120 mm.

4. The method of claim 1, wherein the flame spot diameter is 6-25 mm.

5. The method of claim 1, wherein the cylindrical inner wall and lance combination are moved relative to each other in the axial direction during the spraying process.

6. The method of claim 1, the gas streams injected by the first, and third gas flow lances each independently being air, nitrogen, an inert gas, or a combination thereof.

7. The method of claim 1, the paint sprayed by the paint spray gun being an abradable coating paint containing a skeletal component and an abradable component.

8. The method of claim 1, the paint spray gun being a flame spray gun or a plasma spray gun.

9. The method of claim 1, the paint spray gun, first air flow spray gun, second air flow spray gun, and third air flow spray gun each being spaced from the cylindrical inner wall by a distance less than a radius of the cylindrical inner wall.

10. The method of claim 1, the radius of the cylindrical inner wall being greater than or equal to 250 mm.

11. A method according to claim 1, wherein the suction flow of the suction device is 4000m³/h～6000m³/h。

12. A component having a cylindrical inner wall, the surface of the cylindrical inner wall being coated with an abradable coating obtained by spraying the method of any one of claims 1 to 11.