A nickel-based superalloy aluminizing agent of aluminum-silicon solid powder and aluminizing method

Abstract

The present invention discloses a nickel-based superalloy aluminizing agent of aluminum-silicon solid powder and an aluminizing method. The aluminizing agent is uniformly mixed by a metal source A, an activator B, and a catalyst C. Among them, by mass percentage, the metal source A includes 60-70% pure aluminum, 30-40% aluminum-silicon alloy, and 1-2% pure chromium; the activator B includes 1-2% sodium chloride and 0.5-1.5% ammonium chloride; the catalyst C includes 0-2% molybdenum powder, 0-1.5% cerium oxide, and 0-1% lanthanum oxide. The rare earth elements in the aluminizing agent of the present invention can improve the adsorption energy of aluminum atoms during the aluminizing process and catalyze the aluminizing process, and the obtained coating has a uniform and dense structure. And a three-stage high-temperature powder-pack aluminizing method is used to prepare the aluminized layer of the nickel-based superalloy, which can significantly improve the atomic diffusion rate during the aluminizing process, and the uniformity of the coating can be improved by subsequent diffusion annealing.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal surface coatings, and particularly relates to an aluminum-silicon solid powder aluminizing agent for nickel-based superalloys and an aluminizing method. Background Art

[0002] With the rapid development of the aviation industry, modern aero-engines have increasingly higher requirements for the thrust-to-weight ratio, making the service conditions of the materials of their hot-end components more and more harsh. Nickel-based superalloys are widely used in hot-end components such as the blades of aero-engines due to their excellent high-temperature mechanical properties, but simply using nickel-based superalloys is far from enough. Nowadays, the gas inlet temperature of advanced aero-engines can reach as high as 1600 °C, and the working temperature of engine blades can reach above 1000 °C. Since the degree that the material's own properties can reach is relatively limited, and the blades are more prone to oxidation and corrosion in a high-temperature environment, it is necessary to improve their oxidation and corrosion resistance in a high-temperature environment through surface treatment technology without affecting their high-temperature strength.

[0003] Currently, the commonly used aluminizing processes mainly include solid pack aluminizing, gas aluminizing, slurry coating aluminizing, and vacuum coating diffusion aluminizing, etc. Among them, solid pack aluminizing is a method of aluminizing the surface by loading the workpiece and the powdered aluminizing agent into a sealed aluminizing box together and going through processes such as heating, heat preservation, and diffusion annealing. The non-aluminized surface of the workpiece can be protected by applying a protective coating. This method is the most widely used so far, and it is a kind of aluminizing process with simple operation and easy control of the aluminized layer depth and composition. However, traditional solid aluminizing agents and aluminizing methods have problems such as insufficiently dense coatings, many inclusions, spalling, nodulation, insufficient corrosion resistance, and relatively slow aluminizing speed. At the same time, general aluminizing agents are not suitable for nickel-based alloys with low chromium and high molybdenum, and it is difficult for aluminized coatings to protect the alloys from corrosion effects. Summary of the Invention

[0004] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title. However, such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0006] One of the purposes of the present invention is to provide an aluminum-silicon solid powder aluminizing agent for nickel-based superalloys.

[0007] To solve the above technical problems, the present invention provides the following technical solution: An aluminum-silicon solid powder aluminizing agent for nickel-based superalloys, wherein the aluminizing agent is uniformly mixed by a metal source A, an activator B, and a catalyst C;

[0008] Among them, by mass percentage, the metal source A includes 60-70% pure aluminum, 30-40% aluminum-silicon alloy, and 1-2% pure chromium; the activator B includes 1-2% sodium chloride and 0.5-1.5% ammonium chloride; the catalyst C includes 0-2% molybdenum powder, 0-1.5% cerium oxide, and 0-1% lanthanum oxide.

[0009] As a preferred embodiment of the aluminizing agent of the nickel-based superalloy aluminum-silicon solid powder of the present invention, wherein: the ratio of cerium oxide to lanthanum oxide in the catalyst C does not exceed 4:1.

[0010] Another object of the present invention is to provide an aluminizing method, including,

[0011] Configuring the aluminizing agent according to the above-mentioned mass percentage;

[0012] Adopting the method of powder-pack high-temperature diffusion, embedding the nickel-based superalloy with the aluminizing agent, and treating it at three temperature stages of 600-700 °C, 800-900 °C, and 500-700 °C;

[0013] Performing diffusion annealing treatment.

[0014] As a preferred embodiment of the aluminizing method of the present invention, wherein: for the configuration of the aluminizing agent, pure aluminum, aluminum-silicon alloy, and pure chromium are mixed and melted, and then atomized by gas to obtain the metal source A; sodium chloride and ammonium chloride are mixed to obtain the activator B; the molybdenum powder, cerium oxide, and lanthanum oxide are mixed to obtain the catalyst C;

[0015] The metal source A, activator B, and catalyst C are ball-milled and mixed evenly and then dried.

[0016] As a preferred embodiment of the aluminizing method of the present invention, wherein: for the treatment at the three temperature stages, after embedding the nickel-based superalloy with the aluminizing agent, it is kept warm at 600-700 °C for 0.5-1 h, then heated to 800-900 °C and kept warm for 2-3 h, and finally cooled to 500-700 °C, kept warm for 0.5-1 h, and then taken out.

[0017] As a preferred embodiment of the aluminizing method of the present invention, wherein: for the embedding of the nickel-based superalloy with the aluminizing agent, it is embedded in a soaking pit, and the soaking pit is made of high-purity corundum.

[0018] As a preferred embodiment of the aluminizing method of the present invention, wherein: for the diffusion annealing treatment, the annealing temperature is 800-1000 °C, the annealing time is 4-8 h, and the cooling method is furnace cooling.

[0019] As a preferred embodiment of the aluminizing method of the present invention, it further includes pre-treating the nickel-based superalloy before aluminizing. After grinding the nickel-based superalloy, it is polished, then ultrasonically cleaned and dried.

[0020] As a preferred embodiment of the aluminizing method of the present invention, in the pre-treatment, the nickel-based superalloy is successively ground with 600-mesh and 1000-mesh sandpapers, polished with 0.5-μm diamond, ultrasonically cleaned with acetone and alcohol solution respectively, and dried.

[0021] As a preferred embodiment of the aluminizing method of the present invention, 200 g of the aluminizing agent is used for each nickel-based superalloy with a size of 10 mm * 10 mm * 2 mm.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The rare earth elements in the aluminizing agent of the present invention can increase the adsorption energy of aluminum atoms during aluminizing, catalyze the aluminizing process, and the obtained coating has a uniform and dense structure. The aluminized layer of the nickel-based superalloy is prepared by the three-stage high-temperature powder-pack aluminizing method, which can significantly increase the atomic diffusion rate during aluminizing, and the uniformity of the coating can be improved by subsequent diffusion annealing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. Among them:

[0025] Figure 1 It is the powder diagram of the embodiment of the present invention;

[0026] Figure 2 It is the optical microscope diagram of Embodiments 1-3 of the present invention;

[0027] Figure 3 It is the scanning electron microscope diagram of Embodiments 1-3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below in conjunction with the embodiments of the specification.

[0029] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways different from those described herein. Persons skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0030] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it an individual or alternative embodiment that is mutually exclusive with other embodiments.

[0031] Unless otherwise specified, the raw materials used in the embodiments are all commercially purchased.

[0032] Example 1

[0033] (1) A nickel-based alloy plate with dimensions of 10 mm × 10 mm × 2 mm was obtained by wire cutting, polished successively with 600-mesh and 1000-mesh sandpapers, and then polished with 0.5-μm diamond. Subsequently, the nickel-based alloy sheet was ultrasonically cleaned in acetone solution and alcohol for 5 min each, and then placed in a vacuum drying oven at 100 °C for drying for 30 min.

[0034] (2) The aluminizing agent metal source A was prepared with an electronic balance with a precision of 0.1 mg: 120 g of pure aluminum, 60 g of aluminum-silicon alloy, and 3 g of pure chromium were melted and then atomized by gas to form powder; the activator B: 3 g of sodium chloride and 1.5 g of ammonium chloride; the catalyst C: 2.5 g of molybdenum powder, 2.5 g of cerium oxide powder, and 1.5 g of lanthanum oxide powder. The three components were mixed evenly by a ball mill and placed in an oven at 120 °C for drying for 2 h for standby.

[0035] (3) 200 g of the aluminizing agent and the nickel-based alloy plate were successively loaded into a crucible, and the upper part of the crucible was filled with ceramic fiber cotton. The muffle furnace was heated to 700 °C, and then the crucible containing the embedded sample was placed in the furnace and the timing was started. After 0.5 h, the temperature was raised to 850 °C and held for 2 h, and finally the temperature was lowered to 700 °C and held for 0.5 h. The heating-up time was 15 min for each stage. Subsequently, the crucible was taken out, air-cooled to room temperature, the sample was taken out, ultrasonically cleaned in distilled water for 5 min, then dried, and blasted with corundum.

[0036] (4) The obtained aluminized sample was placed in a resistance box for diffusion annealing. The annealing temperature was 800 °C, the annealing time was 5 h, and the cooling method was furnace cooling.

[0037] Example 2

[0038] (1) A nickel-based alloy plate with dimensions of 10 mm * 10 mm * 2 mm was obtained by wire cutting, polished successively with 600-mesh and 1000-mesh sandpapers, and then polished with 0.5-μm diamond. Subsequently, the nickel-based alloy sheet was ultrasonically cleaned in acetone solution and alcohol for 5 minutes each, and then dried in a vacuum drying oven at 100 °C for 30 minutes.

[0039] (2) An aluminizing agent metal source A was prepared using an electronic balance with a precision of 0.1 mg: 120 g of pure aluminum, 66 g of aluminum-silicon alloy, and 2.6 g of pure chromium were melted and atomized into powder by gas atomization; an activator B: 2.4 g of sodium chloride and 2 g of ammonium chloride were taken; a catalyst C: 3 g of molybdenum powder, 2.4 g of cerium oxide powder, and 1.6 g of lanthanum oxide powder were taken. The three components were mixed evenly using a ball mill and dried in an oven at 120 °C for 2 hours for standby.

[0040] (3) 200 g of the aluminizing agent and the nickel-based alloy plate were successively loaded into a crucible, and the upper part of the crucible was filled with ceramic fiber cotton. The muffle furnace was heated to 600 °C, and then the crucible containing the embedded sample was placed in the furnace and the timing was started. After 1 hour, the temperature was raised to 900 °C and held for 1 hour, and finally cooled to 600 °C and held for 1 hour. The heating-up time was 15 minutes each. Subsequently, the crucible was taken out, air-cooled to room temperature, the sample was taken out, ultrasonically cleaned in distilled water for 5 minutes, then dried, and blasted with corundum.

[0041] (4) The obtained aluminized sample was placed in a resistance box for diffusion annealing. The annealing temperature was 800 °C, the annealing time was 5 hours, and the cooling method was furnace cooling.

[0042] Example 3

[0043] (1) A nickel-based alloy plate with dimensions of 10 mm * 10 mm * 2 mm was obtained by wire cutting, polished successively with 600-mesh and 1000-mesh sandpapers, and then polished with 0.5-μm diamond. Subsequently, the nickel-based alloy sheet was ultrasonically cleaned in acetone solution and alcohol for 5 minutes each, and then dried in a vacuum drying oven at 100 °C for 30 minutes.

[0044] (2) An aluminizing agent metal source A was prepared using an electronic balance with a precision of 0.1 mg: 120 g of pure aluminum, 66 g of aluminum-silicon alloy, and 2.6 g of pure chromium were melted and atomized into powder by gas atomization; an activator B: 2.4 g of sodium chloride and 2 g of ammonium chloride were taken; a catalyst C: 3 g of molybdenum powder, 2.4 g of cerium oxide powder, and 1.6 g of lanthanum oxide powder were taken. The three components were mixed evenly using a ball mill and dried in an oven at 120 °C for 2 hours for standby.

[0045] (3) Put 200 g of aluminizing agent and nickel-based alloy plates into the crucible in sequence, and stuff ceramic fiber cotton at the upper part of the crucible. Heat the muffle furnace to 700 °C, then put the crucible containing the embedded sample into the furnace and start timing. After 0.5 h, heat it up to 850 °C and keep it warm for 2 h. Finally, cool it down to 600 °C and keep it warm for 0.5 h. The heating-up time is 15 min for each. Then take out the crucible, air-cool it to room temperature, take out the sample, clean it in distilled water with ultrasonic for 5 min, then dry it, and blast it with corundum sand.

[0046] (4) Put the obtained aluminized sample into a resistance box for diffusion annealing. The annealing temperature is 900 °C, the annealing time is 4 h, and the cooling method is furnace cooling.

[0047] The optical microscope images of Examples 1 to 3 are as Figure 2 shown, and the scanning electron microscope images of Examples 1 to 3 are as Figure 3 shown. It can be seen from Figure 2 , Figure 3 that after aluminizing the surface of the specimen by using the nickel-based superalloy aluminizing agent and aluminizing method of aluminum-silicon solid powder of the present invention, the aluminized layer on the surface of the specimen is uniform, dense, has good continuity, and the oxide particle inclusions at the matrix interface are significantly reduced. When the three-stage aluminizing temperature is 700 °C / 0.5 h, 850 °C / 2 h and 600 °C / 0.5 h, and the diffusion annealing temperature is 900 °C and the annealing time is 4 h, the aluminized layer has the best effect, the thickness of the aluminized layer is uniform, about 20 - 25 μm.

[0048] Comparative Example 1

[0049] (1) Obtain a nickel-based alloy plate with dimensions of 10 mm * 10 mm * 2 mm by wire cutting, polish it successively with 600-mesh and 1000-mesh sandpapers, and then polish it with 0.5-μm diamond; then ultrasonically clean the nickel-based alloy sheet in acetone solution and alcohol for 5 min each, and then put it into a vacuum drying oven at 100 °C for drying for 30 min;

[0050] (2) Configure the aluminizing agent metal source A with an electronic balance with an accuracy of 0.1 mg: Take 120 g of pure aluminum, 66 g of aluminum-silicon alloy, and 2.6 g of pure chromium, melt them and make powder by gas atomization; Activator B: Take 2.4 g of sodium chloride and 2 g of ammonium chloride. Mix the two components evenly with a ball mill, put them into an oven at 120 °C for drying for 2 h for standby;

[0051] (3) Load 200 g of aluminizing agent and nickel-based alloy plates into a crucible in sequence, and stuff ceramic fiber cotton at the upper part of the crucible. Heat the muffle furnace to 700 °C, then put the crucible embedded with the sample into the furnace and start timing. After 0.5 h, heat it up to 850 °C and hold for 2 h. Finally, cool it down to 600 °C and hold for 0.5 h. The heating-up time is 15 min for each. Then take out the crucible, air-cool it to room temperature, take out the sample, clean it in distilled water by ultrasonic for 5 min, then dry it, and blast it with corundum sand.

[0052] (4) Put the obtained aluminized sample into a resistance box for diffusion annealing. The annealing temperature is 900 °C, the annealing time is 4 h, and the cooling method is furnace cooling.

[0053] Comparative Example 2

[0054] (1) Obtain nickel-based alloy plates of 10 mm×10 mm×2 mm by wire cutting, polish them successively with 600-mesh and 1000-mesh sandpapers, and then polish them with 0.5-μm diamond; then ultrasonically clean the nickel-based alloy sheets in acetone solution and alcohol for 5 min each, and then put them into a vacuum drying oven at 100 °C for drying for 30 min;

[0055] (2) Configure the aluminizing agent metal source A with an electronic balance accurate to 0.1 mg: Take 120 g of pure aluminum, 66 g of aluminum-silicon alloy, and 2.6 g of pure chromium, melt them and make powder by gas atomization; activator B: Take 2.4 g of sodium chloride and 2 g of ammonium chloride; catalyst C: Take 3 g of molybdenum powder, 2.4 g of cerium oxide powder, and 1.6 g of lanthanum oxide powder. Mix the three components evenly with a ball mill, and put them into an oven at 120 °C for drying for 2 h for standby;

[0056] (3) Load 200 g of aluminizing agent and nickel-based alloy plates into a crucible in sequence, and stuff ceramic fiber cotton at the upper part of the crucible. Heat the muffle furnace to 700 °C, then put the crucible embedded with the sample into the furnace and start timing. After 0.5 h, heat it up to 850 °C and hold for 2 h. Finally, cool it down to 600 °C and hold for 0.5 h. The heating-up time is 15 min for each. Then take out the crucible, air-cool it to room temperature, take out the sample, clean it in distilled water by ultrasonic for 5 min, then dry it, and blast it with corundum sand.

[0057] Comparative Example 3

[0058] (1) Obtain nickel-based alloy plates of 10 mm×10 mm×2 mm by wire cutting, polish them successively with 600-mesh and 1000-mesh sandpapers, and then polish them with 0.5-μm diamond; then ultrasonically clean the nickel-based alloy sheets in acetone solution and alcohol for 5 min each, and then put them into a vacuum drying oven at 100 °C for drying for 30 min;

[0059] (2) Use an electronic balance with a precision of 0.1 mg to prepare the aluminized agent metal source A: Take 120 g of pure aluminum, 66 g of aluminum-silicon alloy, and 2.6 g of pure chromium, melt them, and make powder by gas atomization; Activator B: Take 2.4 g of sodium chloride and 2 g of ammonium chloride; Catalyst C: Take 3 g of molybdenum powder, 2.4 g of cerium oxide powder, and 1.6 g of lanthanum oxide powder. Use a ball mill to mix the three components evenly, place them in an oven at 120 °C and dry for 2 h for standby;

[0060] (3) Load 200 g of the aluminized agent and the nickel-based alloy plate into the crucible in sequence, and stuff ceramic fiber cotton at the upper part of the crucible. Heat the muffle furnace to 850 °C and keep it warm for 3 h, then take out the crucible, air-cool it to room temperature, take out the sample, clean it in distilled water with ultrasonic for 5 min, then dry it, and blast it with corundum.

[0061] (4) Put the obtained aluminized sample into the resistance box for diffusion annealing, the annealing temperature is 900 °C, the annealing time is 4 h, and the cooling method is furnace cooling.

[0062] The average corrosion rate of the specimens obtained in Examples 1 to 3 and Comparative Examples 1 to 3 was tested. A polarization test was carried out in 3.5% NaCl solution using an electrochemical tester to characterize the corrosion resistance of the samples. The corrosion rate (CR) was calculated from the Faraday equation:

[0063]

[0064] In the formula, EW is the equivalent weight, Icorr is the corrosion current density, and ρ is the alloy density. The test results are shown in Table 1.

[0065] Table 1

[0066] specimen CR (mm / y) Example 1 0.083 Example 2 0.075 Example 3 0.052 Comparative Example 1 4.099 Comparative Example 2 1.254 Comparative Example 3 1.782

[0067] It can be seen from the data in Table 1 that after aluminizing the surface of the specimen by the nickel-based superalloy aluminized agent and aluminizing method of the present invention, the corrosion rate of the specimen surface is significantly reduced, indicating that the corrosion resistance is improved after aluminizing. When the three-stage aluminizing temperature is 700 °C / 0.5 h, 850 °C / 2 h and 600 °C / 0.5 h, and the diffusion annealing temperature is 900 °C and the annealing time is 4 h, the effect of the aluminized layer is the best and the average corrosion rate is the lowest.

[0068] The aluminized layer of nickel-based superalloy is prepared by the method of three-stage high-temperature powder pack aluminizing in this invention, which can significantly improve the atomic diffusion rate during aluminizing, and the uniformity of the coating can be improved by subsequent diffusion annealing. The rare earth elements in the aluminizing agent can increase the adsorption energy of aluminum atoms during aluminizing and catalyze the aluminizing process, and the obtained coating has a uniform and dense structure. At the same time, the addition of molybdenum powder results in the presence of a large number of silicides such as MoSi2, Ti5Si3, and (Cr, Ni)3Si in the aluminum-silicon coating based on the β(NiAl) phase, greatly improving the corrosion resistance of the coating. In addition, the addition of sodium chloride inhibits the content of impurity elements, making the coating more dense, reducing the inclusion of oxide particles at the interface with the substrate, and thus obtaining an ideal aluminized layer, greatly enhancing the corrosion resistance of the specimen.

[0069] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. An aluminizing method, characterized in that: Including, Preparing an aluminizing agent according to mass percentages; Adopting the method of powder-pack high-temperature diffusion, embedding a nickel-based superalloy with the aluminizing agent, and treating it at three temperature ranges: 600 - 700 °C, 800 - 900 °C, and 500 - 700 °C; Performing diffusion annealing treatment; Among them, the aluminizing agent is uniformly mixed by a metal source A, an activator B, and a catalyst C; Among them, by mass percentage, the metal source A includes 60 - 62% pure aluminum, 31 - 33% aluminum-silicon alloy, and 1 - 2% pure chromium; the activator B includes 1 - 2% sodium chloride and 0.8 - 1.0% ammonium chloride; the catalyst C includes 1.3 - 1.5% molybdenum powder, 1.2 - 1.3% cerium oxide, and 0.8% lanthanum oxide; The ratio of cerium oxide to lanthanum oxide in the catalyst C does not exceed 4:

1.

2. The aluminizing method according to claim 1, characterized in that: For preparing the aluminizing agent, the pure aluminum, aluminum-silicon alloy, and pure chromium are mixed and melted, and then atomized by gas to obtain the metal source A; the sodium chloride and ammonium chloride are mixed to obtain the activator B; the molybdenum powder, cerium oxide, and lanthanum oxide are mixed to obtain the catalyst C; The metal source A, activator B, and catalyst C are ball-milled and mixed evenly and then dried.

3. The aluminizing method according to claim 1 or 2, characterized in that: For the treatment at the three temperature ranges, after embedding the nickel-based superalloy with the aluminizing agent, keep it at 600 - 700 °C for 0.5 - 1 h, then raise the temperature to 800 - 900 °C and keep it for 2 - 3 h, and finally lower the temperature to 500 - 700 °C, keep it for 0.5 - 1 h and then take it out.

4. The aluminizing method according to claim 3, characterized in that: For embedding the nickel-based superalloy with the aluminizing agent, it is embedded in an infiltration tank made of high-purity corundum.

5. The aluminizing method according to any one of claims 1, 2, and 4, characterized in that: For performing the diffusion annealing treatment, the annealing temperature is 800 - 1000 °C, the annealing time is 4 - 8 h, and the cooling method is furnace cooling.

6. The aluminizing method according to claim 5, characterized in that: It also includes pre-treating the nickel-based superalloy before aluminizing. After grinding the nickel-based superalloy, perform polishing treatment, then perform ultrasonic cleaning and drying.

7. The aluminizing method according to claim 6, characterized in that: For the pre-treatment, the nickel-based superalloy is ground successively with 600-mesh and 1000-mesh sandpapers, polished with 0.5 µm diamond for the nickel-based superalloy, ultrasonically cleaned with acetone and alcohol solution respectively, and dried.

8. The aluminizing method according to any one of claims 1, 2, 4, 6, and 7, characterized in that: 200 g of the aluminizing agent is used for each nickel-based superalloy with a size of 10 mm * 10 mm * 2 mm.

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