Spraying method of dense vertical crack coating

Abstract

The invention relates to the technical field of blade surface treatment, in particular to a spraying method of a dense vertical crack coating. The method comprises the steps of treatment before spraying, spraying of a lower bonding layer, spraying of an upper bonding layer, detection and confirmation of the surface roughness of a coating, spraying of a heat insulation layer and surface polishing. In the spraying process of the heat insulation layer, stress is generated in the cooled heat insulation layer due to the thermal expansion difference between the heat insulation layer and the bonding layer, the heat insulation layer cracks, and vertical cracks which penetrate through the heat insulation layer and are distributed in the heat insulation layer in a large number are formed. According to the vertical cracks in the heat insulation layer, under the condition that the hardness and strength of the coating are not damaged, enough space can be formed in the coating to accommodate deformation generated by thermal expansion, and the phenomenon that the coating is broken is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of blade surface treatment, in particular to a spraying method for a dense vertical crack coating. Background Art

[0002] In the combustion chamber of aircraft engines and gas turbines, thermal barrier coatings are usually sprayed on the surface of blades to achieve the purpose of heat insulation. Usually, the coating is a zirconium oxide ceramic coating. At the same time, under high temperature environment, the blade itself will produce thermal expansion. Since the thermal expansion coefficient of the metal matrix is ​​usually much larger than the thermal expansion coefficient of the thermal barrier ceramic coating, in order to prevent the coating from cracking under thermal expansion, the porosity of the thermal barrier coating is usually limited to more than 10% to leave enough space for expansion. However, due to the high porosity of the coating, the hardness and strength of the coating are low, and the coating is prone to cracking. Summary of the invention

[0003] In response to the shortcomings of the above-mentioned existing production technology, the present application provides a method for spraying a dense vertical crack coating, which produces vertical cracks that penetrate the coating by artificially controlling the powder temperature of the sprayed coating, so that there is enough space in the coating to accommodate the deformation caused by thermal expansion, thereby preventing the coating from cracking.

[0004] The technical solution adopted by the present invention is as follows: A spraying method for a dense vertical crack coating comprises the following steps: (1) Pre-spraying treatment: Use sand to blast the area of ​​the blade to be sprayed to improve the surface roughness of the area of ​​the blade to be sprayed, and then perform ultrasonic cleaning on the blade to remove the residual sand in the area of ​​the blade to be sprayed; (2) Spraying of lower bonding layer: Use a supersonic flame spray gun to spray metal powder on the blade area to be sprayed to form a lower bonding layer; (3) Spraying of upper bonding layer: Use an atmospheric plasma spray gun to spray metal powder on the surface of the blade in the area to be sprayed, and form an upper bonding layer on the surface of the lower bonding layer. The upper bonding layer and the lower bonding layer are connected to form a bonding layer. The bonding layer is mainly used for bonding between the metal substrate and the thermal insulation layer; (4) Detect and confirm the surface roughness of the coating: Use a surface roughness measuring instrument to measure the surface roughness of the upper bonding layer and confirm that the surface roughness of the upper bonding layer Ra ≥ 9μm; if the surface roughness of the upper bonding layer Ra < 9μm, remove the upper bonding layer by pickling and re-spray the upper bonding layer until the surface roughness of the upper bonding layer meets the requirements; (5) Thermal insulation layer spraying: Use an atmospheric plasma spray gun to spray ceramic powder on the blade area to be sprayed, and spray back and forth along the same path on the surface of the upper bonding layer to form multiple thermal insulation layers of a certain thickness. The thermal insulation layer plays the role of a protective coating. The thermal expansion difference between the thermal insulation layer and the bonding layer causes stress in the thermal insulation layer after cooling, resulting in cracking of the thermal insulation layer, forming vertical cracks that penetrate the thermal insulation layer and are distributed in large numbers in the thermal insulation layer; (6) Surface grinding: Use a grinding device to grind and polish the thermal insulation layer until the surface roughness of the thermal insulation layer reaches Ra < 7μm.

[0005] Furthermore, in the pre-spraying treatment, the sand material used for sandblasting is white corundum or silicon carbide, the mesh number of the sand material used is 20 mesh to 80 mesh, and the surface roughness Ra of the blade area to be sprayed after sandblasting is greater than 5 μm.

[0006] Furthermore, during the spraying of the lower bonding layer, the metal powder sprayed is a nickel-based alloy powder, the particle size of the nickel-based alloy powder is 15 μm-45 μm, and the powder feeding amount of the nickel-based alloy powder is 30 g / min per route.

[0007] Furthermore, during the spraying of the upper bonding layer, the metal powder sprayed is a nickel-based alloy powder, and the particle size of the nickel-based alloy powder is 45 μm to 90 μm.

[0008] Furthermore, during the spraying of the thermal insulation layer, the thickness of a single powder coating layer is increased to more than 60 μm by reducing the moving speed of the atmospheric plasma spray gun, and at the same time, the hydrogen flow rate is increased to raise the powder temperature to more than 500°C, so that after each spraying, the difference in thermal expansion between the thermal insulation layer and the bonding layer causes stress to be generated in the thermal insulation layer after cooling.

[0009] Furthermore, the ceramic powder used in the thermal insulation layer spraying is yttria-stabilized zirconia, the particle size of the ceramic powder is 15 μm-45 μm, and the powder feeding rate of the ceramic powder is 20 g / min.

[0010] Furthermore, the grinding device adopts a diamond hand-wiping disc.

[0011] The beneficial effects of the present invention are as follows: The vertical cracks in the thermal insulation layer of the present invention can allow sufficient space in the coating to accommodate deformation caused by thermal expansion without destroying the hardness and strength of the coating, thereby preventing the coating from cracking. The upper bonding layer and the lower bonding layer of the present invention are connected to form a bonding layer, which can be used for bonding between the metal substrate and the thermal insulation layer to improve the bonding strength of the thermal insulation layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic diagram of the coating structure of the present invention.

[0013] Among them: 1. Adhesive layer; 2. Thermal insulation layer; 3. Vertical cracks. DETAILED DESCRIPTION

[0014] The specific implementation of the present invention will be described below in conjunction with the accompanying drawings.

[0015] like Figure 1 As shown, a spraying method for a dense vertical crack coating includes: (1) Pre-treatment before spraying: Use abrasive materials to sandblast the area of ​​the blade to be sprayed to improve the surface roughness of the area of ​​the blade to be sprayed, and then perform ultrasonic cleaning on the blade to remove the residual abrasive materials in the area of ​​the blade to be sprayed.

[0016] In the pre-spraying treatment, the sand material used for sandblasting is white corundum or silicon carbide, and the mesh number of the sand material used is 20 mesh to 80 mesh. After sandblasting, the surface roughness Ra of the blade area to be sprayed is greater than 5μm.

[0017] (2) Spraying of lower bonding layer: Use a supersonic flame spray gun to spray metal powder on the blade area to be sprayed to form a lower bonding layer.

[0018] When the supersonic flame spray gun is in use, kerosene and oxygen are introduced into the combustion chamber. The spray gun nozzle can spray out a high-speed flame flow. At the same time, nitrogen carrying metal powder is blown into both sides of the spray gun nozzle to send the metal powder into the flame flow. The flame flow blows high-temperature metal droplets to the surface of the blade surface to be sprayed, so that the metal droplets are fully spread to form an upper bonding layer.

[0019] During the spraying of the lower bonding layer, the metal powder sprayed is a nickel-based alloy powder, the particle size of the nickel-based alloy powder is 15 μm-45 μm, and the powder feeding amount of the nickel-based alloy powder is 30 g / min per route.

[0020] (3) Spraying of upper bonding layer: Use an atmospheric plasma spray gun to spray metal powder on the surface of the blade in the area to be sprayed, forming an upper bonding layer on the surface of the lower bonding layer. The upper bonding layer and the lower bonding layer are connected to form a bonding layer. The bonding layer is mainly used for bonding between the metal substrate and the thermal insulation layer.

[0021] When the atmospheric plasma spray gun is in use, a mixture of hydrogen and argon is introduced into the cavity, and an electric current is introduced into the spray gun. The arc heats the mixed gas to a plasma state, and high-speed plasma rushes out of the nozzle. At the same time, argon carrying metal powder is blown into both sides of the spray gun nozzle to send the metal powder into the plasma. The plasma blows high-temperature metal droplets to the surface of the blade area to be sprayed, so that the metal droplets are fully spread and form an upper bonding layer on the surface of the lower bonding layer.

[0022] During the spraying of the upper bonding layer, the metal powder sprayed is a nickel-based alloy powder, and the particle size of the nickel-based alloy powder is 45 μm to 90 μm.

[0023] (4) Test and confirm the surface roughness of the coating: Use a surface roughness measuring instrument to measure the surface roughness of the upper bonding layer and confirm that the surface roughness of the upper bonding layer Ra ≥ 9μm; if the surface roughness of the upper bonding layer Ra < 9μm, remove the upper bonding layer by pickling and re-spray the upper bonding layer until the surface roughness of the upper bonding layer meets the requirements.

[0024] (5) Thermal insulation layer spraying: Use an atmospheric plasma spray gun to spray ceramic powder on the blade area to be sprayed, and spray back and forth along the same path on the surface of the upper bonding layer to form multiple thermal insulation layers of a certain thickness. The thermal insulation layer acts as a protective coating.

[0025] When using the atmospheric plasma spray gun, a mixture of hydrogen and argon is introduced into the cavity, and an electric current is introduced into the spray gun. The arc heats the mixed gas to a plasma state, and high-speed plasma rushes out of the nozzle. At the same time, argon gas carrying ceramic powder is blown into both sides of the spray gun nozzle to send the ceramic powder into the plasma. The plasma blows the melted or semi-melted high-temperature ceramic powder to the surface of the blade to be sprayed, so that the ceramic powder is fully spread and forms a heat insulation layer on the surface of the upper bonding layer. By spraying back and forth on the workpiece along the same path, a multi-layer heat insulation layer structure of a certain thickness can be formed.

[0026] In use, the thickness of a single-pass powder coating is increased to more than 60μm by reducing the moving speed of the atmospheric plasma spray gun, and the temperature of the powder is increased to more than 500℃ by increasing the hydrogen flow rate. After each spraying, the thermal expansion difference between the thermal insulation layer and the bonding layer causes stress in the thermal insulation layer after cooling, resulting in cracks in the thermal insulation layer, forming Figure 1 Vertical cracks are shown penetrating the insulation layer and are widely distributed within the insulation layer.

[0027] The ceramic powder used in the thermal insulation layer spraying is yttria-stabilized zirconia, the particle size of the ceramic powder is 15 μm-45 μm, and the powder feeding amount of the ceramic powder is 20 g / min.

[0028] (6) Surface grinding: Use diamond hand polishing pads to grind and polish the thermal insulation layer. The thermal insulation layer needs to be polished to a surface roughness of Ra < 7μm.

[0029] The present invention controls the powder temperature of the spray coating manually, and the thermal expansion difference between the thermal insulation layer and the bonding layer causes stress to be generated in the thermal insulation layer after cooling, resulting in cracking of the thermal insulation layer, forming vertical cracks that penetrate the thermal insulation layer and are distributed in large quantities in the thermal insulation layer. Vertical cracks that penetrate the coating are formed, so that there is enough space in the coating to accommodate the deformation caused by thermal expansion, so as to avoid the coating from cracking.

[0030] The above description is an explanation of the present invention, not a limitation of the present invention. The scope of the present invention is defined in the claims. Any form of modification may be made within the scope of protection of the present invention.

Claims

1. A spraying method for a dense vertical crack coating, characterized in that: The steps include: (1) Pre-spraying treatment: Use sand to blast the area of ​​the blade to be sprayed to improve the surface roughness of the area of ​​the blade to be sprayed, and then perform ultrasonic cleaning on the blade to remove the residual sand in the area of ​​the blade to be sprayed; (2) Spraying of lower bonding layer: Use a supersonic flame spray gun to spray metal powder on the blade area to be sprayed to form a lower bonding layer; (3) Spraying of upper bonding layer: Use an atmospheric plasma spray gun to spray metal powder on the surface of the blade in the area to be sprayed, and form an upper bonding layer on the surface of the lower bonding layer. The upper bonding layer and the lower bonding layer are connected to form a bonding layer. The bonding layer is mainly used for bonding between the metal substrate and the thermal insulation layer; (4) Detect and confirm the surface roughness of the coating: Use a surface roughness measuring instrument to measure the surface roughness of the upper bonding layer and confirm that the surface roughness of the upper bonding layer Ra ≥ 9μm; if the surface roughness of the upper bonding layer Ra < 9μm, remove the upper bonding layer by pickling and re-spray the upper bonding layer until the surface roughness of the upper bonding layer meets the requirements; (5) Thermal insulation layer spraying: Use an atmospheric plasma spray gun to spray ceramic powder on the blade area to be sprayed, and spray back and forth along the same path on the surface of the upper bonding layer to form multiple thermal insulation layers of a certain thickness. The thermal insulation layer plays the role of a protective coating. The thermal expansion difference between the thermal insulation layer and the bonding layer causes stress in the thermal insulation layer after cooling, resulting in cracking of the thermal insulation layer, forming vertical cracks that penetrate the thermal insulation layer and are distributed in large numbers in the thermal insulation layer; (6) Surface grinding: Use a grinding device to grind and polish the thermal insulation layer until the surface roughness of the thermal insulation layer reaches Ra < 7μm.

2. A method for spraying a dense vertical crack coating as claimed in claim 1, characterized in that: In the pre-spraying treatment, the sand material used for sandblasting is white corundum or silicon carbide, the mesh number of the sand material used is 20 mesh to 80 mesh, and the surface roughness Ra of the blade to be sprayed area after sandblasting is greater than 5 μm.

3. A method for spraying a dense vertical crack coating as claimed in claim 1, characterized in that: In the spraying of the lower bonding layer, the metal powder sprayed is nickel-based alloy powder, the particle size of the nickel-based alloy powder is 15 μm-45 μm, and the powder feeding amount of the nickel-based alloy powder is 30 g / min per route.

4. The spraying method of a dense vertical crack coating according to claim 1, characterized in that: In the spraying of the upper bonding layer, the metal powder sprayed is nickel-based alloy powder, and the particle size of the nickel-based alloy powder is 45 μm to 90 μm.

5. The spraying method of a dense vertical crack coating according to claim 1, characterized in that: During the thermal insulation layer spraying, the thickness of a single powder coating layer is increased to more than 60 μm by reducing the moving speed of the atmospheric plasma spray gun, and the temperature of the powder is increased to more than 500° C. by increasing the hydrogen flow rate, so that after each spraying, the difference in thermal expansion between the thermal insulation layer and the bonding layer causes stress to be generated in the thermal insulation layer after cooling.

6. A method for spraying a dense vertical crack coating as claimed in claim 5, characterized in that: The ceramic powder used in the thermal insulation layer spraying is yttria-stabilized zirconia, the particle size of the ceramic powder is 15 μm-45 μm, and the powder feeding amount of the ceramic powder is 20 g / min.

7. A method for spraying a dense vertical crack coating as claimed in claim 1, characterized in that: The grinding device adopts a diamond hand-wiping disc.

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