Diffusion treatment method for aluminum coating of inner cavity of turbine blade

Abstract

The invention relates to the technical field of surface treatment of turbine blades, in particular to a diffusion treatment method for an aluminum coating of an inner cavity of a turbine blade. The diffusion treatment method for the aluminum coating of the inner cavity of the turbine blade comprises the following steps that (a) the surface of the inner cavity of the turbine blade is pretreated, and impurities and rust on the surface of the turbine blade are removed; (b) spraying an aluminum powder permeating agent on the surface of the inner cavity of the pretreated turbine blade to prepare an aluminum coating; (c) performing diffusion treatment on the aluminum coating on the turbine blade; (d) carrying out micro-pore sealing treatment on the aluminum coating on the turbine blade subjected to diffusion treatment; and (e) carrying out heat treatment on the aluminum coating on the turbine blade subjected to micro-pore sealing treatment. According to the method, the oxidation resistance of the turbine blade can be remarkably improved. In a high-temperature environment, the aluminum oxide layer can effectively prevent the surface of the blade from being oxidized, and material loss is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of surface treatment of turbine blades, and in particular to a diffusion treatment method for an aluminum coating in an inner cavity of a turbine blade. Background Art

[0002] As key components of aircraft engines and gas turbines, turbine blades are exposed to high temperature, high pressure and high corrosion environments for a long time, so the high temperature resistance, oxidation resistance and corrosion resistance of their surface materials are crucial. Although traditional coating technologies (such as aluminum plating, spraying titanium alloy coatings, etc.) can improve the heat resistance of turbine blades, there are still problems such as coating shedding and oxidation reactions, which can lead to blade failure or performance degradation.

[0003] At present, aluminum coating and diffusion treatment technology are widely used for high temperature protection of metal surfaces, but their application in the inner cavity of turbine blades is not yet mature. How to enhance the antioxidant capacity and improve the service life of turbine blades while maintaining their performance is still a difficult problem in the development of technology in this field. Therefore, it is urgent to solve it.

[0004] The above contents are only used to assist in understanding the technical solution of the present invention, and do not constitute an admission that the above contents are the closest prior art. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a diffusion treatment method for the aluminum coating of the inner cavity of a turbine blade, which can significantly improve the anti-oxidation performance of the turbine blade. In a high temperature environment, the aluminum oxide layer can effectively prevent the blade surface from oxidation and reduce material loss.

[0006] To achieve the above object, the technical solution of the present invention is implemented as follows: a diffusion treatment method for an aluminum coating in the inner cavity of a turbine blade, the diffusion treatment method for an aluminum coating in the inner cavity of a turbine blade comprises the following steps:

[0007] (a) Pre-treating the inner cavity surface of the turbine blade to remove impurities and rust on the surface of the turbine blade;

[0008] (b) spraying aluminum powder penetrant on the inner cavity surface of the pretreated turbine blade to prepare an aluminum coating;

[0009] (c) Diffusion treatment of aluminum coating on turbine blades;

[0010] (d) performing micro-pore sealing treatment on the aluminum coating on the turbine blades after the diffusion treatment;

[0011] (e) Optimization of heat treatment of aluminum coating on turbine blades after micropore sealing.

[0012] Preferably, the thickness of the aluminum coating in step b is 50-100 μm.

[0013] Preferably, the preparation process of the aluminum coating in step b comprises the following steps:

[0014] b1) preparing a corresponding amount of aluminum powder infiltrant according to the inner cavity surface area of ​​the pretreated turbine blade;

[0015] b2) using a vapor deposition technique or an arc spraying method to evenly coat the prepared aluminum powder infiltrant on the inner surface of the turbine blade;

[0016] b3) After natural drying for 1 hour, repeat step b2 to evenly coat the inner cavity surface of the turbine blade at least three times to form an aluminum coating that completely covers the inner cavity surface of the turbine blade.

[0017] Preferably, the process of diffusion treatment of the aluminum coating in step c comprises:

[0018] c1) installing the turbine blades with aluminum coating on a bracket, and hanging the bracket into a metal infiltration furnace;

[0019] c2) pre-evacuating the metal infiltration furnace;

[0020] c3) Start the vacuum metal infiltration furnace to heat the turbine blades on the bracket at a temperature of 800-1100°C for 4-10 hours, until the aluminum element in the aluminum coating fully penetrates into the surface of the base metal to form an aluminum alloy compound.

[0021] Preferably, in step d, the micro-pore sealing process of the aluminum coating comprises:

[0022] d1) spraying a layer of aluminum powder evenly on the aluminum coating of the turbine blade after the diffusion treatment;

[0023] d2) placing the turbine blades with aluminum coating sprayed with aluminum powder in a hot heating furnace at a temperature of 800-1100° C. until a dense aluminum oxide protective layer is formed on the aluminum coating surface of the turbine blades.

[0024] Preferably, the process of heat treatment optimization of the aluminum coating in step e comprises:

[0025] e1) Use alcohol with a purity greater than 99.7% to wipe the surface of the turbine blades, and use an alcohol pot to rinse the inner cavity of the turbine blades at least three times until the alcohol flows out cleanly without impurities;

[0026] e2) After cleaning the turbine blades, use an air gun to blow and dry the surface and inner cavity of the turbine blades; the drying temperature is 60-80℃, and the drying time is ≥30 minutes;

[0027] e3) After purging and drying, the turbine blades are placed in a heat treatment furnace and heated to 1120°C-1140°C. After keeping the temperature for 2.25-2.5 hours, the heat treatment furnace is closed and filled with argon gas. The turbine blades are cooled to below 480-500°C at a cooling rate of not less than 40°C / minute. The turbine blades are then cooled to room temperature along with the furnace;

[0028] e4) Open the heat treatment furnace again, heat the turbine blades to 850-870 degrees Celsius, keep them warm for 4.5-4.75 hours, then fill them with argon gas, cool the turbine blades to below 480-500 degrees Celsius, and the cooling rate is not less than 15 degrees Celsius per minute. The turbine blades are then cooled to room temperature along with the furnace.

[0029] Preferably, the aluminum powder penetrant in step b is composed of 3-8wt% aluminum powder, 0.5-3% ammonium chloride, 40-70wt% aluminum oxide I, and 25-45wt% aluminum oxide II, calculated by weight percentage.

[0030] Preferably, the particle size of the aluminum powder is 40 to 90 microns; the particle size of the ammonium chloride is 75 to 150 microns; the particle size of the aluminum oxide I is 16 to 36 microns, and the particle size of the aluminum oxide II is 60 to 160 microns.

[0031] The beneficial effects of the present invention are embodied in:

[0032] (1) The method provided by the present invention forms a dense aluminum oxide protective layer through aluminum coating and diffusion treatment, which significantly improves the anti-oxidation performance of turbine blades. In a high temperature environment, the aluminum oxide layer can effectively prevent the blade surface from oxidation and reduce material loss.

[0033] (2) The aluminum alloy compound formed by the aluminum coating and the base metal during the diffusion process provided by the present invention has strong corrosion resistance and can effectively prevent the blade surface from being corroded in a high temperature and high humidity environment.

[0034] (3) The method provided by the present invention enables the turbine blades to work stably for a long time under a high temperature and high pressure environment through coating and diffusion treatment schemes, thereby extending the service life of the blades and reducing maintenance costs.

[0035] (4) The method provided by the present invention forms a strong chemical bonding force between the aluminum coating and the base metal through diffusion treatment, ensuring that the coating is not easy to fall off or peel off, thereby ensuring the long-term reliability of the coating.

[0036] (5) The method provided by the present invention adopts mature technologies such as vapor deposition or arc spraying, has strong process controllability, and can be widely used in the production and maintenance of turbine blades. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention and the comparative examples. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. In the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0038] Example

[0039] A diffusion treatment method for an aluminum coating in the inner cavity of a turbine blade, the diffusion treatment method for an aluminum coating in the inner cavity of a turbine blade comprising the following steps:

[0040] (a) Pre-treat the inner surface of the turbine blade to remove impurities and rust on the surface of the turbine blade.

[0041] (b) Spraying aluminum powder penetrant on the inner cavity surface of the pretreated turbine blade to prepare an aluminum coating. In step b, the aluminum powder penetrant is composed of 3-8wt% aluminum powder, 0.5-3% ammonium chloride, 40-70wt% aluminum oxide I, and 25-45wt% aluminum oxide II by weight. The particle size of the aluminum powder is 40-90 microns; the particle size of the ammonium chloride is 75-150 microns; the particle size of the aluminum oxide I is 16-36 microns, and the particle size of the aluminum oxide II is 60-160 microns.

[0042] The preparation process of the aluminum coating in step b comprises the following steps:

[0043] b1) preparing a corresponding amount of aluminum powder infiltrant according to the inner cavity surface area of ​​the pretreated turbine blade;

[0044] b2) using a vapor deposition technique or an arc spraying method to evenly coat the prepared aluminum powder infiltrant on the inner surface of the turbine blade;

[0045] b3) After natural drying for 1 hour, repeat step b2 to evenly coat the inner cavity surface of the turbine blade at least three times to form an aluminum coating that completely covers the inner cavity surface of the turbine blade. The thickness of the aluminum coating in step b is 50-100 μm.

[0046] Through the above method, a layer of aluminum coating is evenly coated on the inner surface of the turbine blade, ensuring good bonding between the coating and the base metal and effectively protecting the blade surface from high-temperature oxidation.

[0047] (c) Diffusion treatment of aluminum coating on turbine blades;

[0048] The process of diffusion treatment of the aluminum coating in step c includes:

[0049] c1) installing the turbine blades with aluminum coating on a bracket, and hanging the bracket into a metal infiltration furnace;

[0050] c2) pre-evacuating the metal infiltration furnace;

[0051] c3) Start the vacuum metal infiltration furnace to heat the turbine blades on the bracket at a temperature of 800-1100°C for 4-10 hours, until the aluminum element in the aluminum coating fully penetrates into the surface of the base metal to form an aluminum alloy compound.

[0052] Through the above method, after the aluminum coating is applied, a diffusion treatment is performed to ensure that the aluminum element fully penetrates into the surface of the base metal. The diffusion treatment allows the aluminum element to form a stable aluminum alloy compound with the base metal, thereby enhancing the adhesion and durability of the coating.

[0053] (d) performing micro-pore sealing treatment on the aluminum coating on the turbine blades after the diffusion treatment;

[0054] In step d, the micro-pore sealing process of the aluminum coating includes:

[0055] d1) Evenly spray a layer of aluminum powder on the aluminum coating of the turbine blade that has completed the diffusion treatment, and the particle size of the aluminum powder is 40 microns.

[0056] d2) placing the turbine blades with aluminum coating sprayed with aluminum powder in a hot heating furnace at a temperature of 800-1100° C. until a dense aluminum oxide protective layer is formed on the aluminum coating surface of the turbine blades.

[0057] Through the above method, during the high-temperature oxidation process, the aluminum powder on the aluminum coating reacts with oxygen in the air to form a dense aluminum oxide (Al2O3) protective layer, further improving the oxidation resistance of the turbine blade surface. The aluminum oxide layer remains stable at high temperatures, can seal the micropores of the aluminum coating, and prevent the aluminum element in the coating cavity from migrating or decomposing, thereby ensuring the long-term stability of the coating and preventing the base metal from oxidizing.

[0058] (e) Optimization of heat treatment of aluminum coating on turbine blades after micropore sealing.

[0059] The process of heat treatment optimization of the aluminum coating in step e includes:

[0060] e1) Use alcohol with a purity greater than 99.7% to wipe the surface of the turbine blades, and use an alcohol pot to rinse the inner cavity of the turbine blades at least three times until the alcohol flows out cleanly without impurities;

[0061] e2) After cleaning the turbine blades, use an air gun to blow and dry the surface and inner cavity of the turbine blades; the drying temperature is 60-80℃, and the drying time is ≥30 minutes;

[0062] e3) After purging and drying, the turbine blades are placed in a heat treatment furnace and heated to 1120°C-1140°C. After keeping the temperature for 2.25-2.5 hours, the heat treatment furnace is closed and filled with argon gas. The turbine blades are cooled to below 480-500°C at a cooling rate of not less than 40°C / minute. The turbine blades are then cooled to room temperature along with the furnace;

[0063] e4) Open the heat treatment furnace again, heat the turbine blades to 850-870 degrees Celsius, keep them warm for 4.5-4.75 hours, then fill them with argon gas, cool the turbine blades to below 480-500 degrees Celsius, and the cooling rate is not less than 15 degrees Celsius per minute. The turbine blades are then cooled to room temperature along with the furnace.

[0064] Through the above method, the turbine blades can be further heat treated to optimize the grain structure of the material and improve the overall mechanical properties of the blades, so as to improve the high temperature strength and corrosion resistance of the blades.

[0065] Embodiment 1:

[0066] Using the above method, the aircraft engine turbine blade is selected as the base material. First, the vapor deposition technology is used to coat the inner surface of the blade three times to form an aluminum coating with a thickness of 80μm. Then the coated blade is placed in a vacuum furnace and diffused at 1000℃ for 6 hours. The aluminum coating of the turbine blade that has completed the diffusion treatment is optimized by aging heat treatment at 850℃ for 12 hours. After the treatment, a dense aluminum oxide protective layer is formed on the surface of the blade. The surface is smooth and uniform, and no obvious oxidation marks are observed.

[0067] Through the high temperature oxidation resistance test, the turbine blades in Example 1 were heated to 1100°C, kept warm for 15 hours after reaching the temperature, and cooled to below 100°C to room temperature with the furnace. The coating surface was uniformly gray, and no oxidation corrosion or peeling problems were found. However, when the traditional coating material was heated to 1100°C, kept warm for 15 hours after reaching the temperature, and cooled to below 100°C to room temperature with the furnace, the coating surface showed coating peeling.

[0068] Therefore, the coating on the turbine blade of Example 1 prepared by the method of the present invention has improved high-temperature oxidation resistance compared with traditional coatings in terms of high-temperature resistance, and significantly enhances its ability to adapt to high-temperature environments.

[0069] Embodiment 2:

[0070] Using the above method, an aluminum coating is uniformly coated on the inner cavity of a gas turbine blade by arc spraying, with a coating thickness of 60 μm. The coated blade is then diffused in a high-temperature furnace, with a heating temperature of 950°C and a treatment time of 8 hours, and finally an oxidation-resistant aluminum alloy compound is formed on the surface of the blade.

[0071] Referring to the requirements of the navigation mark HB5258-2000, the weight gain method was used to test the oxidation resistance of the aluminum alloy compound coating on the turbine blade in Example 2. Four cylindrical specimens were selected for coating tests. The specimens were in the state of infiltration layer + diffusion and aging heat treatment. The oxidation weight gain, unit area oxidation weight gain, and oxidation rate of the four specimens were statistically analyzed. As shown in Table 1 below:

[0072] Table 1 Statistics of the oxidation resistance test of aluminum alloy compound coating

[0073]

[0074] As can be seen from the table above, the aluminum alloy compound coatings of the four samples were prepared in the manner of Example 2. The average weight gain per unit area of ​​the four samples after oxidation was calculated to be 7.3186 g / m 2 , the average oxidation rate is 0.0366g / m 2 *h. That is, the oxidation resistance of the aluminum alloy compound coating on the turbine blade is rated as completely oxidation-resistant. This proves that the aluminum alloy compound on the turbine blade significantly improves the high temperature resistance, oxidation resistance and corrosion resistance of the turbine blade.

[0075] The present invention provides an effective surface protection solution by applying and diffusing an aluminum coating to the inner cavity of the turbine blade, which can not only significantly improve the oxidation resistance and corrosion resistance of the turbine blade, but also extend its service life, and has important industrial application value.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A diffusion treatment method for the aluminum coating in the inner cavity of a turbine blade, characterized in that: The diffusion treatment method of the aluminum coating in the inner cavity of the turbine blade comprises the following steps: (a) Pre-treating the inner cavity surface of the turbine blade to remove impurities and rust on the surface of the turbine blade; (b) spraying aluminum powder penetrant on the inner cavity surface of the pretreated turbine blade to prepare an aluminum coating; (c) Diffusion treatment of aluminum coating on turbine blades; (d) performing micro-pore sealing treatment on the aluminum coating on the turbine blades after the diffusion treatment; (e) Optimization of heat treatment of aluminum coating on turbine blades after micropore sealing.

2. The diffusion treatment method for the inner cavity aluminum coating of a turbine blade according to claim 1, characterized in that: The thickness of the aluminum coating in step b is 50-100 μm.

3. The diffusion treatment method for the inner cavity aluminum coating of a turbine blade according to claim 2, characterized in that: The preparation process of the aluminum coating in step b comprises the following steps: b1) preparing a corresponding amount of aluminum powder infiltrant according to the inner cavity surface area of ​​the pretreated turbine blade; b2) using a vapor deposition technique or an arc spraying method to evenly coat the prepared aluminum powder infiltrant on the inner surface of the turbine blade; b3) After natural drying for 1 hour, repeat step b2 to evenly coat the inner cavity surface of the turbine blade at least three times to form an aluminum coating that completely covers the inner cavity surface of the turbine blade.

4. The diffusion treatment method for the inner cavity aluminum coating of a turbine blade according to claim 1, characterized in that: The process of diffusion treatment of the aluminum coating in step c includes: c1) installing the turbine blades with aluminum coating on a bracket, and hanging the bracket into a metal infiltration furnace; c2) pre-evacuating the metal infiltration furnace; c3) Start the vacuum metal infiltration furnace to heat the turbine blades on the bracket at a temperature of 800-1100°C for 4-10 hours, until the aluminum element in the aluminum coating fully penetrates into the surface of the base metal to form an aluminum alloy compound.

5. The diffusion treatment method for the inner cavity aluminum coating of a turbine blade according to claim 1, characterized in that: In step d, the micro-pore sealing process of the aluminum coating includes: d1) spraying a layer of aluminum powder evenly on the aluminum coating of the turbine blade after the diffusion treatment; d2) placing the turbine blades with aluminum coating sprayed with aluminum powder in a hot heating furnace at a temperature of 800-1100° C. until a dense aluminum oxide protective layer is formed on the aluminum coating surface of the turbine blades.

6. The diffusion treatment method for the inner cavity aluminum coating of a turbine blade according to claim 5, characterized in that: The process of heat treatment optimization of the aluminum coating in step e includes: e1) Use alcohol with a purity greater than 99.7% to wipe the surface of the turbine blades, and use an alcohol pot to rinse the inner cavity of the turbine blades at least three times until the alcohol flows out cleanly without impurities; e2) After cleaning the turbine blades, use an air gun to blow and dry the surface and inner cavity of the turbine blades; the drying temperature is 60-80℃, and the drying time is ≥30 minutes; e3) After purging and drying, the turbine blades are placed in a heat treatment furnace and heated to 1120°C-1140°C. After keeping the temperature for 2.25-2.5 hours, the heat treatment furnace is closed and filled with argon gas. The turbine blades are cooled to below 480-500°C at a cooling rate of not less than 40°C / minute. The turbine blades are then cooled to room temperature along with the furnace; e4) Open the heat treatment furnace again, heat the turbine blades to 850-870 degrees Celsius, keep them warm for 4.5-4.75 hours, then fill them with argon gas, cool the turbine blades to below 480-500 degrees Celsius, and the cooling rate is not less than 15 degrees Celsius per minute. The turbine blades are then cooled to room temperature along with the furnace.

7. The diffusion treatment method for the inner cavity aluminum coating of a turbine blade according to claim 1, characterized in that: The aluminum powder penetrant in step b is composed of 3-8wt% aluminum powder, 0.5-3% ammonium chloride, 40-70wt% aluminum oxide I, and 25-45wt% aluminum oxide II, calculated by weight percentage.

8. The diffusion treatment method for the inner cavity aluminum coating of a turbine blade according to claim 7, characterized in that: The particle size of the aluminum powder is 40 to 90 microns; the particle size of the ammonium chloride is 75 to 150 microns; the particle size of the aluminum oxide I is 16 to 36 microns, and the particle size of the aluminum oxide II is 60 to 160 microns.

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