A turbine disk gullet repair method

Abstract

This invention discloses a method for repairing turbine disk grates. The method includes: calculating the restored dimension based on the difference between the current dimension and the design dimension of the turbine disk; spraying the turbine disk grates with a repair coating according to the restored dimension, until the current dimension of the turbine disk equals the design dimension; the working gas temperature during spraying is 700℃. After spraying, the coating is vacuum remelted in a vacuum environment. After vacuum remelting, burrs from the repair process are removed by machining. This method not only enables rapid repair of turbine disk grates but also reduces the internal stress between the repair material and the substrate during the repair process, thereby reducing the risk of stress cracking of the coating.

Description

Technical Field

[0001] This invention relates to the field of aircraft engine maintenance, and in particular to a method for repairing turbine disk ferrules. Background Technology

[0002] The clearance between the rotor and stator of an aero-engine plays a crucial role in reducing internal airflow losses and improving engine performance. To minimize engine leakage, numerous sealing structures are used between the rotor and stator. Grate seals, due to their simple structure, low cost, and high reliability at high temperatures and speeds, are widely used in aero-engines.

[0003] During the operation of an aero-engine, the tips of the turbine disk grates made of high-temperature alloys will rub against the stator components, resulting in a reduction in the size of the grates and an increase in the turbine-stator clearance after service. This makes it impossible to meet the clearance control requirements of subsequent assembly, so the worn turbine disk grates need to be repaired.

[0004] Existing technologies primarily involve additive repair of turbine disk grates using laser cladding. Laser cladding repair comprises two steps: substrate pre-melting and powder cladding. During substrate pre-melting, a laser is used to irradiate the turbine disk grates, melting the grate substrate, followed by powder cladding. During powder cladding, alloy powder identical to the turbine disk body material is sprayed onto the molten grate substrate and irradiated with a laser to complete the grate repair.

[0005] While laser cladding can repair sieve teeth, it requires melting the sieve substrate, essentially a welding repair method. This leaves residual stress inside the sieve teeth, making them prone to cracking during operation. Furthermore, after repair, the laser-clad repaired area of ​​the turbine disk sieve needs to be inspected using fluorescent flaw detection, followed by stress relief heat treatment and shot peening. The process is complex and has a long repair cycle.

[0006] Therefore, there is an urgent need to find a new repair method to quickly restore the turbine disk tooth size. Summary of the Invention

[0007] The purpose of this invention is to provide a method for repairing turbine disk grates, which can quickly repair turbine disk grates and avoid stress inside the grates, in order to address the problems mentioned above.

[0008] The technical solution adopted in this invention is as follows:

[0009] A method for repairing turbine disk ferrules, the method comprising:

[0010] Restoration dimension calculation: Determine the restoration dimension based on the difference between the current dimension and the design dimension of the turbine disk;

[0011] Turbine disk cleavage spraying: Based on the restoration dimensions, spray the area to be repaired on the turbine disk cleavage to form a repair coating until the current dimensions of the turbine disk are equal to the design dimensions;

[0012] Vacuum remelting: The sprayed turbine disk is remelted in a vacuum heat treatment furnace;

[0013] Repair coating finishing: After vacuum remelting, the repair coating is finished by machining to remove burrs.

[0014] Furthermore, before spraying, the powder is preheated to 300~400℃ in an inert gas protective atmosphere; during spraying, the working gas is an inert gas, the temperature of the working gas is 650~700℃, the pressure of the working gas is 2.2~2.8MPa, and the spraying distance is 40~70 mm.

[0015] Furthermore, the method for preparing the spraying powder is as follows:

[0016] After mixing 25-30%wt of nickel-chromium-borosilicate powder and 70-75%wt of nickel-chromium-chromium-carbide powder, the mixture is placed in a ball mill jar at a ball-to-powder ratio of 2:1, and anhydrous ethanol is added. After ball milling for 18-24 hours, the mixture is dried in a vacuum drying oven and then sieved through 400-mesh and 800-mesh screens to obtain a spray powder with a diameter of 15μm-37μm.

[0017] Furthermore, before spraying, the non-repair area is protected to prevent the spray powder from being sprayed onto the non-repair area.

[0018] Furthermore, the area to be repaired includes the tooth crests, the first side surface, and the second side surface of the pylon;

[0019] The first and second side surfaces are located on either side of the tooth tip;

[0020] The non-repair area is the bottom surface of the tooth groove;

[0021] When protecting the non-repair area, an elastic high-temperature plastic ring is used to cover the bottom surface of the tooth groove.

[0022] Furthermore, after the non-repair area is protected, the area to be repaired is sandblasted, and then the area to be repaired is sprayed with paint.

[0023] Furthermore, during sandblasting, the sandblasting pressure is 0.25 MPa, the sand particle size is 60 mesh, and the sandblasting distance is 150 mm.

[0024] Furthermore, during the spraying process, the turbine disk rotates; first, the first side of the relative teeth is sprayed, and after one round, the tooth tips of the teeth are sprayed, and after one round, the second side of the teeth is sprayed, and after one round, the tooth tips of the teeth are sprayed, and after one round, the first side of the teeth is sprayed again; this process is repeated until the current size of the turbine disk equals the design size.

[0025] Furthermore, when spraying the first side of the comb teeth, the angle between the central axis of the powder bundle formed by the sprayed powder and the first side of the comb teeth is 40~60°.

[0026] When spraying the top of the teeth of the comb, the central axis of the powder beam formed by the sprayed powder is perpendicular to the tooth top.

[0027] When spraying the second side of the comb teeth, the angle between the central axis of the powder beam formed by the sprayed powder and the second side of the comb teeth is 40~60°.

[0028] Furthermore, during vacuum remelting, the temperature of the turbine disk upon entering the furnace is ≤200℃; the vacuum heat treatment furnace is pre-evacuated to 1.33×10⁻⁶. -2 Pa;

[0029] After the turbine disk is placed in the vacuum heat treatment furnace, it is kept at 900~1020℃ for 20~30 minutes, then cooled to 500℃ with the furnace, and then inert gas is introduced into the vacuum heat treatment furnace to cool it to below 200℃ before it is taken out of the furnace.

[0030] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0031] The present invention has one of the following beneficial effects:

[0032] 1. After laser cladding, a series of processes such as fluorescence detection, magnetic detection, stress relief, and shot peening are required, which increases repair costs and time. This method eliminates the need for fluorescence detection, magnetic detection, and stress relief, further reducing repair time and enabling rapid repair.

[0033] 2. Cold spraying can produce an initial repair coating with low porosity, low oxidation, and high bonding strength. Then, vacuum remelting allows the low-melting-point elements in the repair coating to fill the pores and form an interdiffusion layer between the repair coating elements and the substrate, increasing the metallurgical bond between the repair coating and the substrate, thereby giving the repaired ferrules high bonding strength.

[0034] 3. The hard chromium carbide in the sprayed powder plays a wear-resistant role in the repair coating, increasing the wear resistance of the repair coating and extending the service life of the grates. The nickel-chromium-boron-silicon in the sprayed powder not only provides matrix support for chromium carbide and improves the coating bonding strength, but also provides low-melting-point elements, creating conditions for subsequent vacuum remelting.

[0035] 4. The method provided by this invention enables rapid repair of ferrules with wear dimensions ranging from 0.3 to 1.2 mm, overcoming the shortcomings of traditional spraying methods, such as slow powder application at the ferrule tips, poor adhesion, and thin coating thickness (below 0.3 mm). While traditional laser repair methods can achieve a large thickness buildup at the ferrule tips, the powder temperature during laser cladding is higher than the powder's melting point (above 1300℃). The spraying temperature of this invention (below 700℃) is much lower than that of laser cladding. Through low-temperature spraying and vacuum remelting, the ferrule substrate is not melted, avoiding the risk of internal stress cracking within the repair coating.

[0036] 5. The turbine disk operates at high temperatures, with instantaneous peak temperatures exceeding 800°C. Under such high temperatures, the tips of the ferrules repaired using traditional methods are prone to wear. This invention, through the rational design of powder composition, spraying process parameters, spraying method, and post-treatment process, enables the ferrule tips to operate stably for extended periods even at high operating temperatures, thereby extending the service life of the components. Attached Figure Description

[0037] Figure 1 This is a view of the end face of the turbine disk teeth;

[0038] Figure 2 and Figure 3 This is a diagram showing the positional relationship between the spraying device and the turbine disk;

[0039] In the figure, 1-first side surface, 2-tooth top, 3-second side surface, 4-tooth groove bottom surface, 5-spraying device. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0043] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0044] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0045] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0046] like Figures 1-3 As shown, this invention discloses a method for repairing turbine disk ferrules, the method comprising:

[0047] Step 1, Calculate the restored dimensions: Determine the restored dimensions based on the difference between the current dimensions and the design dimensions of the turbine disk;

[0048] Step 2, Turbine disk cleavage spraying: Based on the restored dimensions, spray the area to be repaired on the turbine disk cleavage to form a repair coating until the current dimensions of the turbine disk are equal to the design dimensions; the spraying powder used is nickel-chromium-boron-silicon nickel-chromium-chromium carbide powder; in this embodiment, the spraying powder used includes 25~30%wt of nickel-chromium-boron-silicon powder and 70~75%wt of nickel-chromium-chromium carbide powder; the temperature of the spraying working gas is less than or equal to 700°C during spraying.

[0049] Step 3, Vacuum remelting: The sprayed turbine disk is remelted in a vacuum heat treatment furnace;

[0050] Step 4, Repairing the coating: After vacuum remelting, the repair coating is repaired by machining.

[0051] Compared with laser cladding, the repair method of the present invention has a spraying temperature that is much lower than that of laser cladding. Through low-temperature spraying and vacuum remelting, the base material of the toothed tooth will not be melted, thus avoiding the risk of internal stress cracking in the repair coating.

[0052] Laser cladding requires a series of procedures, including fluorescence and magnetic detection, stress relief heat treatment, and shot peening, which increases repair costs and time. This method, however, eliminates the need for fluorescence and magnetic detection, further reducing repair time.

[0053] In the repair method of this invention, the spraying temperature is much lower than that of laser cladding. This low-temperature spraying method results in a repair coating with less oxidation, lower porosity, and higher bonding strength. After vacuum remelting, the low-melting-point elements B and Si in the sprayed powder, along with the wear-resistant Cr3C2, fill the pores in the coating and facilitate interdiffusion between the coating elements and the substrate, enabling a metallurgical bond between the repair coating and the tooth matrix, thus enhancing the bonding force between the repair coating and the tooth matrix.

[0054] In the repair method of the invention, since the sprayed powder contains Cr3C2 with good wear resistance, the hard phase Cr3C2 is diffusely distributed in the coating after low temperature spraying and vacuum remelting treatment, which increases the wear resistance of the tooth tip of the comb, and there is no need to spray a separate wear-resistant coating.

[0055] Furthermore, before spraying, the powder is preheated to 300-400°C in an inert gas protective atmosphere; during spraying, the working gas is inert gas, the temperature of the working gas is 650-700°C, the pressure of the working gas is 2.2-2.8 MPa, and the spraying distance is 40-70 mm. The spraying distance refers to the distance from the outlet of the spraying device to the area to be repaired.

[0056] In practice, the inert gas can be helium, the powder is preheated to 350°C, the working gas temperature is 700°C, the working gas pressure is 2.6 MPa, and the spraying distance is 60 mm.

[0057] Its beneficial technical effects are as follows: the coating obtained by spraying in this way has low porosity, is dense, has less oxidation and high bonding strength, which provides conditions for subsequent vacuum remelting; at the same time, since the powder particles do not melt, the temperature rise of the tooth matrix is ​​small and the internal stress is small.

[0058] Furthermore, the method for preparing the spraying powder is as follows:

[0059] After mixing 25-30%wt of nickel-chromium-borosilicate powder and 70-75%wt of nickel-chromium-chromium-carbide powder, the mixture is placed in a ball mill jar at a ball-to-powder ratio of 2:1, and anhydrous ethanol is added. After ball milling for 18-24 hours, the mixture is dried in a vacuum drying oven and then sieved through 400-mesh and 800-mesh screens to obtain a spray powder with a diameter of 15μm-37μm.

[0060] In practice, 30%wt of nickel-chromium-borosilicate powder and 70%wt of nickel-chromium-chromium-carbide powder can be mixed and ball-milled for 24 hours.

[0061] The nickel-chromium-boron-silicon in the sprayed powder not only provides matrix support for chromium carbide and improves coating adhesion strength, but also provides low-melting-point elements, creating conditions for subsequent vacuum remelting. After spraying, the chromium carbide is dispersed throughout the coating matrix, improving the coating's wear resistance. Ball milling and sieving not only make the sprayed powder more uniform but also obtain powder with a suitable particle size.

[0062] Before spraying, protect the non-repair area to prevent the spray powder from being sprayed onto the non-repair area.

[0063] like Figure 1 As shown, the area to be repaired includes the tooth crest 2, the first side surface 1, and the second side surface 3 of the tooth; the first side surface 1 and the second side surface 3 are located on both sides of the tooth crest 2; the non-repair area is the bottom surface 4 of the tooth groove.

[0064] When protecting the non-repair area, an elastic high-temperature plastic ring is used to cover the bottom surface of the tooth groove 4.

[0065] Furthermore, after the non-repair area is protected, the area to be repaired is sandblasted, and then coated. During sandblasting, the sandblasting pressure is 0.25 MPa, the abrasive particle size is 60 mesh, and the sandblasting distance is 150 mm.

[0066] The sandblasting distance refers to the distance from the outlet of the sandblasting device to the area to be repaired.

[0067] Using this spraying method and technique, a thicker coating can be obtained on the tips of the comb teeth. After remelting, a thicker repair coating with a thickness of 0.3~1.2 mm can be obtained.

[0068] Furthermore, such as Figure 2 , 3 As shown, during spraying, the turbine disk rotates; first, the first side 1 of the relative grating teeth is sprayed, and after one round, the tooth tip 2 of the grating teeth is sprayed, and after one round, the second side 3 of the grating teeth is sprayed, and after one round, the tooth tip 2 of the grating teeth is sprayed, and after one round, the first side 1 of the grating teeth is sprayed again; this process is repeated until the current size of the turbine disk is equal to the design size.

[0069] In practice, the turbine disk is placed horizontally on the rotating device, which drives the turbine disk to rotate horizontally at a speed of 30 revolutions per minute.

[0070] When spraying the first side surface 1 of the comb teeth, the angle between the central axis of the powder beam formed by the sprayed powder and the first side surface 1 of the comb teeth is 40~60°. In specific implementation, the angle can be 45°, such as... Figure 2 As shown.

[0071] When spraying the tooth tip 2 of the comb, the central axis of the powder beam formed by the sprayed powder is perpendicular to the tooth tip 2.

[0072] When spraying the second side surface 3 of the comb teeth, the angle between the central axis of the powder beam formed by the sprayed powder and the second side surface 3 of the comb teeth is 40~60°. In specific implementation, the angle can be 45°, such as... Figure 3 As shown.

[0073] The spraying device 5 sprays the powder in a cyclical manner around the turbine disk, which ensures that the powder is evenly and gradually transitioned from the tooth side to the tooth tip 2, thus increasing the adhesion of the sprayed coating.

[0074] Furthermore, during vacuum remelting, the temperature of the turbine disk upon entering the furnace is ≤200℃; the vacuum heat treatment furnace is pre-evacuated to 1.33×10⁻⁶. -2 Pa; After the turbine disk is placed in the vacuum heat treatment furnace, it is kept at 900~1020℃ for 20~30 min, then cooled to 500℃ with the furnace, and then inert gas is introduced into the vacuum heat treatment furnace to cool it to below 200℃ before it is taken out of the furnace.

[0075] In practice, the turbine disk is placed horizontally in a vacuum heat treatment furnace. It can be held at 980°C for 25 minutes, then cooled to 500°C with the furnace, and finally cooled to 180°C by 0.15MPa argon gas before being removed from the furnace.

[0076] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for repairing turbine disk ferrules, characterized in that: The method includes: Restoration dimension calculation: Determine the restoration dimension based on the difference between the current dimension and the design dimension of the turbine disk; Turbine disk grating spraying: According to the restoration size, the area to be repaired of the turbine disk grating is sprayed to form a repair coating until the current size of the turbine disk is equal to the design size; the preparation method of the spraying powder is as follows: 25~30%wt of nickel-chromium-borosilicate powder and 70~75%wt of nickel-chromium-chromium carbide powder are mixed and then milled in a ball mill jar at a ball-to-powder ratio of 2:1, with the addition of anhydrous ethanol. After milling for 18~24 hours, the powder is dried in a vacuum drying oven and then sieved through 400-mesh and 800-mesh screens to obtain a spraying powder with a diameter of 15μm~37μm; Vacuum remelting: The coated turbine disk is remelted in a vacuum heat treatment furnace; during vacuum remelting, the temperature of the turbine disk upon entering the furnace is ≤200℃; the vacuum heat treatment furnace is pre-evacuated to 1.33×10⁻⁶. -2 Pa; After the turbine disk is placed in the vacuum heat treatment furnace, it is kept at 900~1020℃ for 20~30 min, then cooled to 500℃ with the furnace, and then inert gas is introduced into the vacuum heat treatment furnace to cool it to below 200℃ before it is taken out of the furnace. Repair coating finishing: After vacuum remelting, the repair coating is finished by machining to remove burrs; Before spraying, the powder is preheated to 300~400℃ in an inert gas protective atmosphere; during spraying, the working gas is an inert gas, the temperature of the working gas is 650~700℃, the pressure of the working gas is 2.2~2.8MPa, and the spraying distance is 40~70 mm.

2. The turbine disk tooth repair method according to claim 1, characterized in that: Before spraying, protect the non-repair area to prevent the spray powder from being sprayed onto the non-repair area.

3. The turbine disk tooth repair method according to claim 2, characterized in that: The area to be repaired includes the tooth crest, a first side surface, and a second side surface of the apex; the first side surface and the second side surface are located on both sides of the tooth crest. The non-repair area is the bottom surface of the tooth groove; When protecting the non-repair area, an elastic high-temperature plastic ring is used to cover the bottom surface of the tooth groove.

4. The turbine disk tooth repair method according to claim 3, characterized in that: After the non-repair area is protected, the area to be repaired is sandblasted, and then the area to be repaired is coated.

5. The turbine disk gullet repair method of claim 4, wherein: During sandblasting, the sandblasting pressure is 0.25 MPa, the sand particle size is 60 mesh, and the sandblasting distance is 150 mm.

6. The turbine disk tooth repair method according to claim 1, characterized in that: During spraying, the turbine disk rotates; first, the first side of the tooth is sprayed, and after one round, the tooth tip is sprayed. After one round, the second side of the tooth is sprayed, and after one round, the tooth tip is sprayed. After one round, the first side of the tooth is sprayed again. This process is repeated until the current size of the turbine disk equals the design size.

7. The turbine disk tooth repair method according to claim 6, characterized in that: When spraying the first side of the comb teeth, the angle between the central axis of the powder beam formed by the sprayed powder and the first side of the comb teeth is 40~60°. When spraying the top of the teeth of the comb, the central axis of the powder beam formed by the sprayed powder is perpendicular to the tooth top. When spraying the second side of the comb teeth, the angle between the central axis of the powder beam formed by the sprayed powder and the second side of the comb teeth is 40~60°.

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