Process method for removing environmental deposits on surface of high-temperature alloy blade

Abstract

The process method for removing the environmental sediments on the surface of the high-temperature alloy blade comprises the following steps: S101, preparing an alkaline mixed solution and a hydrochloric acid weak corrosion mixed solution; s102, a plurality of turbine blades are soaked in the alkaline mixed solution and the hydrochloric acid weak corrosion mixed solution respectively, and the turbine blades do not make contact with one another in the soaking process; s103, the step S102 is repeated until the sediments on the surface of the turbine blade are removed; and S104, the turbine blade subjected to sediment removal is subjected to auxiliary process treatment, and detection is conducted. According to the method, an alkali washing process and a hydrochloric acid weak corrosion process are combined, through test detection and test piece processing verification, the quality of the aluminized layer before and after removal is compared, the quality of a base material, the quality of a solid aluminized layer and the quality of an aluminum-silicon-yttrium coating is not affected by the method, and surface sediments can be efficiently removed.

Description

Technical Field

[0001] The present invention belongs to the technical field of blade surface treatment after service, and particularly relates to a process method for removing environmental deposits on the surface of superalloy blades. Background Art

[0002] K465 cast nickel-based superalloy is comprehensively strengthened by various metals and has comprehensive properties such as high high-temperature strength and certain oxidation resistance at high temperatures of (650-1000)°C. It is widely used in manufacturing aeroengine turbine blades and guide vanes. However, its own heat-resistant corrosion performance is poor. If it is used at high temperatures for a long time, a protective coating needs to be applied. According to the operating conditions of the engine, aluminized layers, aluminum-silicon-yttrium coatings and other aluminum-based antioxidant diffusion coatings are usually applied on the blade surface.

[0003] After the blade is in service, brick-red deposits will form on the surface. The formation of the brick-red deposits is closely related to the structure of the engine, the type of fuel used, the working conditions and operating conditions, etc. Energy dispersive spectroscopy (EDS) was used to analyze the chemical composition of the surface deposits on the turbine blades and guide vanes, and it was found that the surface deposits mainly contain C, O, Ca, Al, Si, Mg, P. It is analyzed that C is the main component of carbon deposition, which is the product of the high-temperature oxidation of fuel. In the combustion chamber, due to insufficient oxygen supply, the fuel cannot be completely burned, generating soot and tar particles, which firmly adhere to the part surface after high-temperature oxidation; O is the main component of oxides at high temperatures; Ca, Al, Si, and Mg are the dust, volcanic ash and various environmental pollutants in the atmosphere during the service of the engine, which are deposited and adhered to the blade surface and sintered to form hard deposits mainly composed of CaO, MgO, Al2O3 and SiO2 after high-temperature oxidation.

[0004] After the engine is in service in the field, according to the design requirements, it is necessary to inspect the quality of the aluminized layer on the blade. If the aluminized layer is unqualified, the aluminized layer needs to be removed by sandblasting - pickling - polishing. At this time, the surface deposits can be removed by sandblasting; if the quality of the aluminized layer is qualified, fluorescence inspection is carried out. After passing the inspection, it can continue to be used. However, due to the firmly adhered brick-red deposits on the blade surface, the fluorescence background is poor, which affects the inspection and determination of defects. The existing removal processes for the brick-red deposits are wet sandblasting, manual grinding and chemical methods, and the disadvantages are as follows:

[0005] Most wet sandblasting operations are manual, and the influence on the thickness of the aluminized layer cannot be accurately controlled, and the process stability is poor; the effect of manual grinding is poor and the efficiency is low;

[0006] Most chemical methods use foreign alkaline solutions, which have a certain influence on the thickness of the aluminized layer.

[0007] Overall, the existing methods for removing deposits have low efficiency. Therefore, to ensure the repair quality of the engine, it is necessary to develop a process method that has no influence on the quality of the aluminized layer and has a good effect on removing surface deposits. Summary of the Invention

[0008] In view of this, the process method for removing environmental deposits on the surface of superalloy blades provided by the present invention solves the technical problem of low efficiency in removing deposits by existing methods.

[0009] A process method for removing environmental deposits on the surface of superalloy blades, which is applicable to the treatment of deposits formed on the surface of cast nickel-based superalloy turbine blades of aeroengines after service. The process method includes:

[0010] S101: Prepare an alkaline mixed solution and a weak hydrochloric acid corrosion mixed solution;

[0011] S102: Immerse multiple turbine blades in the alkaline mixed solution and the weak hydrochloric acid corrosion mixed solution respectively, and ensure that each turbine blade does not come into contact during the immersion process;

[0012] S103: Repeat step S102 in a cycle until the deposits on the surface of the turbine blades are removed;

[0013] S104: Perform auxiliary process treatment on the turbine blades after removing the deposits and conduct inspections.

[0014] Advantageous Effects

[0015] The process method of the present invention combines the processes of alkali washing and weak hydrochloric acid corrosion. Through experimental testing and verification of test piece processing, by comparing the quality of the infiltration layer before and after removal, this process method has no impact on the matrix material, the quality of the solid aluminized layer (thickness, microstructure), and the quality of the aluminum-silicon-yttrium coating (thickness, microstructure, microhardness, aluminum content). Moreover, it can efficiently remove surface deposits. This process method does not require degreasing treatment, is simple to operate, and does not require new equipment. It can be processed using existing equipment, enabling batch processing of products, with high production efficiency and low production costs. In addition, the turbine blades and guide vanes processed by this process method can provide a better background for fluorescence inspection, meeting the requirements of part failure inspection. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0017] Figure 1 It is a flowchart of the process method of the present invention. Detailed Embodiments

[0018] The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0019] The following uses specific specific examples to illustrate the implementation manners of the present disclosure. Those skilled in the art can easily understand other advantages and effects of the present disclosure from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. The present disclosure can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts belong to the scope of protection of the present disclosure.

[0020] It should be noted that the following describes various aspects of the embodiments within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is illustrative only. Based on the present disclosure, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number of aspects described herein can be used to implement the device and / or practice the method. In addition, this device and / or this method can be implemented using other structures and / or functions in addition to one or more of the aspects described herein.

[0021] It should also be noted that the diagrams provided in the following embodiments only schematically illustrate the basic concept of the present disclosure, and only show the components related to the present disclosure, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in its actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0022] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the aspects can be practiced without these specific details.

[0023] As Figure 1 shown, the process method for removing environmental deposits on the surface of a superalloy blade is applicable to the treatment of deposits formed on the surface of a cast nickel-based superalloy turbine blade of an aeroengine after service. The process method includes,

[0024] S101: Configure an alkaline mixed solution and a hydrochloric acid weak corrosion mixed solution. Specifically,

[0025] The alkaline mixture is a mixture of NaOH and NaNO3. Among them, NaOH is 500 g / L to 800 g / L, and NaNO3 is 150 g / L to 300 g / L. NaOH can treat deposits such as carbon deposits on the sediment. NaNO3 can convert low-valent oxides in the sediment into high-valent oxides, dissolve them in the alkaline mixture and treat them with a weakly corrosive hydrochloric acid mixture. Working principle: Sodium hydroxide is a strong alkaline substance and has a certain dissolving effect on deposits such as carbon deposits, which can decompose and convert them into substances that are easy to clean. Sodium nitrite NaNO3 has certain oxidizing properties and can convert low-valent oxides that are insoluble in non-oxidizing acids (such as hydrochloric acid) and alkalis in the surface sediment into high-valent oxides and dissolve them in the alkaline solution. Preferably, the ambient temperature of the alkaline mixture is 135 °C to 145 °C, and the immersion time of the turbine blade is 10 to 30 minutes;

[0026] The weakly corrosive hydrochloric acid mixture is a mixture of hydrochloric acid and hexamethylenetetramine. Among them, hydrochloric acid is 40 g / L to 100 g / L, and hexamethylenetetramine is 30 g / L to 60 g / L. Hydrochloric acid can remove high-valent oxides in the alkaline mixture. Hexamethylenetetramine is used for anti-corrosion protection of the turbine blade. Working principle: After the high-valent oxides are dissolved, they can be weakly corroded by hydrochloric acid as a supplement to alkaline cleaning. Its main function is to remove the remaining oxides and impurities after alkaline cleaning. Hexamethylenetetramine has a corrosion inhibition effect on the blade and forms a protective film on the blade surface to prevent corrosion. Preferably, the ambient temperature of the weakly corrosive hydrochloric acid mixture is room temperature, and the immersion time of the turbine blade is 1 to 2 minutes.

[0027] S102: Multiple turbine blades are respectively immersed in the alkaline mixture and the weakly corrosive hydrochloric acid mixture, and each turbine blade does not come into contact during the immersion process. Specifically,

[0028] After the turbine blade is immersed in the alkaline mixture, it is washed with cold water. After the turbine blade is immersed in the weakly corrosive hydrochloric acid mixture, it is washed with cold water;

[0029] S103: Repeat step S102 until the deposits on the surface of the turbine blade are removed. For example, "alkaline cleaning - weak hydrochloric acid corrosion - alkaline cleaning - weak hydrochloric acid corrosion....." is cycled until the deposits are completely removed. The efficiency is increased by more than 60% compared with directly removing them by alkaline cleaning. It should be noted that: It is possible to only use an alkaline solution for treatment, but it takes at least 6 hours, which is time-consuming, and the impurities are not easy to clean up, and the efficiency is still low. The specific "alkaline cleaning + weak hydrochloric acid corrosion to remove surface deposits" implementation process of the present invention is as follows,

[0030] (1) Alkaline cleaning: Place the blades in batches in a stainless-steel basket, ensuring that the blades do not touch each other. Immerse the blades in the alkaline solution to ensure full contact with the solution. Determine the alkaline cleaning immersion time according to the severity of the deposits on the blade surface. The immersion time is until the surface deposits start to dissolve.

[0031] (2) Cold water washing: Immerse the blades in cold water for (1 - 2) minutes to remove the residual alkaline solution on the surface. The purpose is to avoid subsequent neutralization chemical reactions of the acid solution and improve the removal efficiency of the deposits.

[0032] (3) Weak corrosion: Immerse the blades in a hydrochloric acid weak corrosion solution for (1 - 2) minutes to ensure full contact with the solution and remove the oxides and impurities on the surface of the solution. For example, aluminum oxide reacts with the acid to form soluble precipitates or metal salts.

[0033] (4) Cold water washing: Immerse the blades in cold water for (1 - 2) minutes to remove the residual acid solution on the surface.

[0034] (5) Repeat steps (1) - (4) until the surface deposits are completely dissolved.

[0035] S104: After removing the deposits, the turbine blades are subjected to auxiliary process treatment and then inspected. Specifically,

[0036] High-pressure water cleaning: Use high-pressure water to remove the residual attachments on the surface.

[0037] Drying: Blow dry with compressed air.

[0038] Inspection: There is no residual deposit on the surface, meeting the process requirements. For example, visually inspect the blade surface. After removal, the surface of the substrate is the oxidation color after high-temperature service. Slight deposit traces are allowed to remain, but no protruding attachments are allowed, that is, the removal meets the standard.

[0039] The method of the present invention makes full use of the self-pitting oxidation and corrosion resistance characteristics of cast nickel-based superalloys (such as K465) to chemically treat the deposits on the turbine blades. Through the step-by-step treatment of alkaline and acid solutions, it can efficiently remove deposits with complex components while taking into account material protection. It not only restores the surface performance of the blades but also extends the service life of key components. The technical effects are as follows:

[0040] 1. Through the alkaline cleaning + hydrochloric acid weak corrosion cycle process, remove the deposits on the surface of nickel-based superalloy blades to ensure product performance and engine reliability.

[0041] 2. This process method has no impact on the superalloy substrate, solid aluminized layer, and aluminum-silicon-yttrium coating.

[0042] 3. The operation of removing surface deposits by this process method is simple and convenient, without the need to add new equipment, with high production efficiency and low production cost. The surface quality of the blades processed by the provided method meets the requirements of inspection. The present invention has broad application prospects and can be extended to the removal of serious carbon deposits on steel parts and superalloy parts of other engine models.

[0043] In one embodiment, the hydrochloric acid weak corrosion mixture and / or the alkaline mixture are placed in a vibrating environment for soaking to shorten the treatment time of the deposits. Specifically,

[0044] The lye is placed in a stainless steel container, and the blades are placed in batches in the stainless steel container. The blades are not allowed to contact each other. The blades are soaked in the lye to ensure full contact with the solution. According to the severity of the surface deposits on the blades, the alkali washing soaking time is determined. The soaking time is when the surface deposits start to dissolve. The stainless steel container is then placed in an ultrasonic device to generate vibration during the alkali washing process to accelerate the reaction. The same principle applies to the acid washing.

[0045] In one embodiment, the auxiliary process in step S104 includes high-pressure water cleaning and drying process treatment for the turbine blades.

[0046] Example 1 is a method for removing surface environmental deposits of a certain aeroengine turbine blade. The process steps are as follows:

[0047] (1) Alkali washing: NaOH 500 g / L, NaNO3 150 g / L, use temperature 140 °C, time 30 min;

[0048] (2) Cold water washing: Tap water, 1 min;

[0049] (3) Hydrochloric acid weak corrosion: HCl 40 g / L, hexamethylenetetramine 30 g / L, room temperature, time 2 min;

[0050] (4) Cold water washing: Tap water, 1 min, repeat (1) - (4) for a total of 2 h;

[0051] (5) High-pressure water cleaning: Use high-pressure water to remove the residual attachments on the surface;

[0052] (6) Drying: Use compressed air to blow dry;

[0053] (7) Inspection: There is no deposit residue on the surface, meeting the process requirements.

[0054] Example 2 is for removing surface environmental deposits of a certain guide vane blade. The process steps are as follows:

[0055] (1) Alkali washing: NaOH 800 g / L, NaNO3 300 g / L, use temperature 140 °C, time 10 min;

[0056] (2) Cold water wash: tap water, 1 min;

[0057] (3) Weak hydrochloric acid corrosion: HCl 100 g / L, hexamethylenetetramine 60 g / L, room temperature, time 1 min;

[0058] (4) Cold water wash: tap water, 1 min, repeat (1) - (4) for a total of 1.5 h;

[0059] (5) High - pressure water cleaning: use high - pressure water to remove residual attachments on the surface;

[0060] (6) Drying: use compressed air to blow dry;

[0061] (7) Inspection: no sediment residue on the surface, only slight traces remaining, meeting the process requirements.

[0062] The technology of the present invention adopts a process method combining alkali washing and weak hydrochloric acid corrosion. Through experimental testing and verification by processing test pieces, by comparing the quality of the infiltration layer before and after removal, this process method has no influence on the matrix material, the quality of the solid aluminized layer (thickness, microstructure), and the quality of the aluminum - silicon - yttrium coating (thickness, microstructure, microhardness, aluminum content), and can efficiently remove surface sediments. This process method does not require degreasing treatment, is easy to operate; does not require new equipment and can be processed using existing equipment; can achieve batch processing of products, with high production efficiency and low production cost. The turbine blades and guide vane blades processed by this process method can provide a better background for fluorescence inspection and meet the requirements for defect inspection of parts.

[0063] As described above, it is only the specific implementation manner of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present disclosure should be covered within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. A process method for removing environmental deposits on the surface of superalloy blades, which is applicable to the treatment of deposits formed on the surface of cast nickel-based superalloy turbine blades of aeroengines after service, and is characterized in that, The process method includes S101: Prepare an alkaline mixed solution and a weak hydrochloric acid corrosion mixed solution; S102: Immerse multiple turbine blades in the alkaline mixed solution and the weak hydrochloric acid corrosion mixed solution respectively, and ensure that each turbine blade does not contact during the immersion process; S103: Repeat step S102 in a loop until the deposits on the surface of the turbine blades are removed; S104: Perform auxiliary process treatment on the turbine blades after removing the deposits and conduct inspections.

2. The process method according to claim 1, wherein Step S101 includes The alkaline mixed solution is a mixed solution of NaOH and NaNO3. Among them, NaOH is 500 g / L to 800 g / L, and NaNO3 is 150 g / L to 300 g / L. NaOH can treat deposits such as carbon deposits on the deposits, and NaNO3 can convert low-valent oxides in the deposits into high-valent oxides, dissolve them in the alkaline mixed solution and be treated through the weak hydrochloric acid corrosion mixed solution.

3. The process method according to claim 2, characterized in that, The ambient temperature of the alkaline mixed solution is 135°C to 145°C, and the immersion time of the turbine blades is 10 to 30 minutes.

4. The process method according to claim 2, characterized in that, After the turbine blades are immersed in the alkaline mixed solution, they are washed with cold water.

5. The process method according to claim 4, characterized in that, Step S102 includes The weak hydrochloric acid corrosion mixed solution is a mixed solution of hydrochloric acid and hexamethylenetetramine. Among them, hydrochloric acid is 40 g / L to 100 g / L, and hexamethylenetetramine is 30 g / L to 60 g / L. The hydrochloric acid can remove high-valent oxides in the alkaline mixed solution, and the hexamethylenetetramine is used for anti-corrosion protection of the turbine blades.

6. The process method according to claim 5, wherein The ambient temperature of the weak hydrochloric acid corrosion mixed solution is room temperature, and the immersion time of the turbine blades is 1 to 2 minutes.

7. The process method according to claim 6, characterized in that, After the turbine blades are immersed in the weak hydrochloric acid corrosion mixed solution, they are washed with cold water.

8. The process method according to any one of claims 1 to 7, characterized in that, The weak hydrochloric acid corrosion mixed solution and / or the alkaline mixed solution are placed in a vibrating environment for immersion to shorten the treatment time of the deposits.

9. The process method according to claim 8, characterized in that, The auxiliary process in step S104 includes The turbine blades are subjected to high-pressure water washing and drying process treatment.

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