A kind of penetrant and its preparation process for aluminizing layer of nickel-based superalloy parts

Abstract

The application discloses a kind of penetrant and its preparation nickel-based superalloy piece aluminizing layer process, penetrant includes the raw material of following mass fraction proportioning: aluminum powder 18%~22%, ammonium chloride 0.5%~1.2%, the rest is calcined alumina.The application uses new raw material and proportioning to prepare penetrant, and the aluminum content of penetrant is moderate, can well meet the requirement of infiltration layer;Optimized heating and holding parameters in aluminizing process play a crucial role on the performance of infiltration layer, ensure that the prepared nickel-based superalloy piece aluminizing layer depth, organization can meet the design requirement, especially for the hollow turbine blade aluminizing on aero-engine, its infiltration layer oxidation resistance, high-temperature gas corrosion resistance, neutral salt spray corrosion resistance can meet the requirements of hollow gas turbine blade oxidation resistance, high-temperature gas corrosion resistance of turboshaft, turboprop engine;The prepared penetrant of the application can be reused, and can ensure that the depth of infiltration layer, infiltration layer organization and aluminum content are within the qualified range.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, specifically to a diffusion agent and a process for preparing an aluminized layer on nickel-based high-temperature alloy parts. Background Technology

[0002] Some components on aero engines require an aluminized layer to improve their performance and meet operational requirements. For example, hollow turbine blades require an aluminized layer to enhance their resistance to high-temperature oxidation and combustion gas corrosion. This aluminized layer is typically formed through vapor-phase aluminizing (where the component and the aluminizing agent do not directly contact; the aluminizing agent reacts to create an activating atmosphere, forming the aluminized layer on the component's surface). Currently, the main component of commercially available aluminizing agents, aluminum powder, is imported. Due to various factors, the quality of aluminum powder cannot be consistently maintained, resulting in uncertainties in the composition, proportions, and particle size of each batch of aluminizing agent, leading to significant fluctuations in aluminized quality. Furthermore, there is a risk of inconsistent and unstable aluminum powder supply, all of which severely impact production schedules and ultimately prevent timely delivery of parts.

[0003] Furthermore, the currently prepared carburizing agent can only be used once. If it is reused multiple times, the carburized layer depth will be too shallow, and the aluminum content of the carburized layer will be too low, failing to guarantee the performance of the carburized layer. Therefore, the method of preparing the carburizing agent only once undoubtedly increases the manufacturing costs for enterprises.

[0004] Patent CN112159954A discloses an aluminizing agent and its application. The aluminizing agent mainly comprises the following raw materials in weight percentage: 84.000-86.000% Al2O3 powder, 12.500-13.000% Al-Si alloy powder, 1.500-2.000% Al-Cr alloy powder, and 0.250-0.300% Cr powder. The invention also includes the application of aluminizing agent for preparing an aluminized layer, comprising the following steps: (1) agent preparation: preparing the aluminizing agent according to the weight percentage; (2) cleaning: cleaning and drying the parts to be aluminized; (3) protection of non-aluminized surfaces: applying a protective coating to the surfaces that do not require aluminization; (4) sandblasting: sandblasting the aluminized parts of the parts, and then cleaning the residual sand particles of the parts with a blower; (5) aluminization: heating container II to 780℃±10℃ and keeping it at that temperature for more than 1 hour; loading the parts and the aluminizing agent into container I, and introducing argon gas into container I to replace the air, with an argon gas flow rate of (1-1.5) m3 / h and an argon gas introduction time of ≥1 hour. Then, place container I in container II, change the flow rate of argon gas into container I to (0.4-0.6) m3 / h, and gradually increase the temperature inside container I. When the temperature inside container I rises to above 600℃, start timing and keep warm for 5min to 60min. Then place container I in a normal temperature environment and adjust the flow rate of argon gas to (1 to 1.5) m3 / h. Stop passing argon gas when the temperature of container I cools down to ≤100℃. Take out the parts in container I; (6) Cleaning: Clean the parts; (7) Sandblasting: Sandblast the parts as a whole until the surface is uniformly grayish-white, and then use a blower to clean the residual sand particles on the parts.

[0005] The aforementioned patent uses an appropriate ratio of Al2O3 powder, Al-Si alloy powder, Al-Cr alloy powder and Cr powder to obtain a carburizing agent that can replace the imported aluminum powder used in its preparation, thus achieving the localization of carburizing agent production. However, this type of carburizing agent has a low aluminum content and is suitable for solid carburizing (embedded carburizing method, where the part is embedded in the carburizing agent), but not for vapor phase carburizing. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a diffusion agent that can make the diffusion depth, structure, oxidation resistance, gas corrosion resistance and corrosion resistance of parts meet the technical requirements and can be reused.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] An aluminizing agent for preparing an aluminized layer comprises raw materials in the following mass fractions: 18%–22% aluminum powder, 0.5%–1.2% ammonium chloride, and the remainder being calcined alumina.

[0009] Furthermore, it includes raw materials in the following mass fraction ratios: 20% aluminum powder, 0.6% to 1% ammonium chloride, and the remainder being calcined alumina.

[0010] A process for preparing an aluminized layer on a nickel-based superalloy part using the aluminizing agent described above includes the following steps:

[0011] S1. Pickling: The parts are pickled with 100% hydrochloric acid to remove hydrogen after pickling;

[0012] S2. First sandblasting: After sandblasting the parts, clean the surface of any remaining sand particles;

[0013] S3. Aluminizing: The aluminizing agent is placed in the furnace chamber of the aluminizing furnace, and the parts are suspended in the furnace chamber space by tooling; the furnace chamber is heated to a certain temperature and held for a period of time, then heated to a higher temperature within a specified time, held for a certain time, and then the parts are cooled.

[0014] S4. Cleaning and drying: Clean the parts and then dry them;

[0015] S5. Second sandblasting: Clean up any remaining sand particles after the sandblasting of the parts is completed.

[0016] Furthermore, in step S3, when the penetrant is a reusable penetrant, 0.8-1.2% by weight of aluminum powder and 0.6-1% by weight of ammonium chloride must be added to the penetrant before use.

[0017] Furthermore, step S1 involves pickling at room temperature for 1–5 minutes, and the dehydrogenation operation is carried out at a temperature of 180–200°C for at least 3 hours.

[0018] Furthermore, in step S2, the part is blown with 200-240 mesh corundum sand at a blowing pressure of less than or equal to 0.25 MPa.

[0019] Further, step S3 is as follows: the furnace is heated to 300±10℃ within 0.9 to 1.2 hours, held for 1 to 2 hours, then heated to 980±10℃ within 2.8 to 3.2 hours, and held for 2 to 7 hours. The parts are cooled in the furnace to less than or equal to 100℃ and then air-cooled after being removed from the furnace.

[0020] Furthermore, in step S3, pure nickel wire is used to bind and suspend the parts on the fixture, and the distance between parts and between parts and fixture is greater than or equal to 20mm.

[0021] Furthermore, in step S4, compressed air is used to clean the parts, then the parts are immersed in hot water to wash them, and then soaked in clean water; the parts are kept at 145±5℃ for 1 to 2 hours to complete the drying operation, and then air-cooled.

[0022] Furthermore, in step S5, the part is blown with 200-240 mesh corundum sand at a blowing pressure of less than or equal to 0.15 MPa.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention uses new raw materials and proportions to formulate the carburizing agent, with a moderate aluminum content that can well meet the requirements of the carburizing layer. The optimized heating and holding parameters during the carburizing process play a crucial role in the performance of the carburized layer, ultimately ensuring that the depth and microstructure of the carburized layer of the prepared nickel-based high-temperature alloy parts meet the design requirements. In particular, for the carburizing of hollow turbine blades on aero-engines, the oxidation resistance, high-temperature gas corrosion resistance, and neutral salt spray corrosion resistance of the carburized layer can meet the requirements of oxidation resistance and high-temperature gas corrosion resistance of hollow gas turbine blades of turboshaft and turboprop engines.

[0025] The penetrant formulated by this invention can be reused multiple times, and the recycled penetrant can still ensure that the penetration layer depth, penetration layer structure and aluminum content are within the qualified range, which greatly saves the production cost of enterprises. Attached Figure Description

[0026] Figure 1a The infiltration metallographic structure of the DZ406 hollow turbine blade prepared in Example 2;

[0027] Figure 1b Metallographic structure of the infiltrated layer for DZ406 hollow turbine blades prepared with an infiltrator formulated using imported aluminum powder;

[0028] Figure 2a The infiltration metallographic structure of the K447A hollow turbine blade prepared in Example 2;

[0029] Figure 2b Metallographic structure of the infiltrated layer for K447A hollow turbine blades prepared with an infiltrator formulated using imported aluminum powder;

[0030] Figure 3a , Figure 3b and Figure 3c The metallographic structures of the DZ406 hollow turbine blade infiltration layer after the first, second, and third uses of the infiltration agent are shown respectively.

[0031] Figure 4a , Figure 4b and Figure 4c The metallographic structures of the infiltrated layer on the K447A hollow turbine blades are shown for the first, second, and third uses of the infiltrator. Detailed Implementation

[0032] To clearly illustrate the technical features of this solution, the following detailed description, in conjunction with the accompanying drawings, will explain the technical solution in detail.

[0033] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0034] Furthermore, it should be understood in the description of this application that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application 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 on this application. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0035] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0036] In this application, unless otherwise expressly specified and limited, the "above" or "below" of the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. In the description of this specification, references to terms such as "an embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples.

[0037] Example 1

[0038] A diffusion agent is provided for preparing an aluminizing layer on hollow turbine blades of an aero-engine. The hollow turbine blade is made of a nickel-based high-temperature alloy. The raw materials used in the preparation of the diffusion agent include aluminum powder, ammonium chloride, and alumina, wherein the alumina is selected as calcined alumina (i.e., high-temperature calcined alumina powder). These raw materials are specifically formulated in the following mass fraction ratios:

[0039] Aluminum powder 18%–22%; ammonium chloride 0.5%–1.2%; the remainder is calcined alumina.

[0040] The aluminum powder mentioned above is gas-atomized aluminum powder, with a mesh size of 800, a spherical or near-spherical morphology, and an aluminum content greater than 99.0%.

[0041] After the aluminum powder is prepared according to the above proportions, the mass fraction of aluminum can be measured again, and it should be maintained between 18% and 22%.

[0042] Example 2

[0043] This embodiment uses the carburizing agent from Example 1 to prepare the aluminized layer on nickel-based high-temperature alloy parts. The main process flow is: pickling → sandblasting → aluminizing → cleaning → drying → sandblasting → inspection. The specific steps are as follows:

[0044] S1. Pickling: Pickle the parts with 100% hydrochloric acid at room temperature for 1-5 minutes. After pickling, remove hydrogen. The hydrogen removal operation shall be carried out at a temperature of 180-200℃ for at least 3 hours.

[0045] S2. First sandblasting: Blow 200-240 mesh corundum sand onto the part, with a sandblasting pressure of less than or equal to 0.25 MPa. After sandblasting, use compressed air to clean the surface of any remaining sand particles.

[0046] S3. Aluminizing: Place the aluminizing agent in the furnace chamber of the vapor phase aluminizing furnace, bind the parts with pure nickel wire, and suspend them on a fixture. The distance between parts and between parts and fixture should be greater than or equal to 20 mm. Heat the furnace chamber to 300±10℃ within 0.9 to 1.2 hours, hold for 1 to 2 hours, then heat to 980±10℃ within 2.8 to 3.2 hours, hold for 2 to 7 hours, and then cool the parts in the furnace to less than or equal to 100℃ before air cooling.

[0047] S4. Cleaning and drying: Clean the blade and inner cavity with compressed air. After cleaning, immerse the parts in hot water and scrub them thoroughly with a nylon brush. Then soak them in clean water for at least 30 minutes. After that, dry the parts at 145±5℃ for 1 to 2 hours. After that, air cool the parts.

[0048] S5. Second sandblasting: Use a ventilated sandblasting fixture to blow 200-240 mesh corundum sand onto the part, with a sandblasting pressure of less than or equal to 0.15 MPa; the air pressure of the sandblasting fixture is ≥0.25 MPa. After sandblasting, use compressed air to clean the residual sand particles.

[0049] S6. Inspection: Check the surface of the parts for defects such as cracks, corrosion, scratches, and foreign matter. Check whether the depth, structure, and mechanical properties of the aluminized layer in the blade and inner cavity of the parts meet the relevant technical requirements.

[0050] This embodiment uses hollow turbine blades made of two nickel-based superalloy materials for testing, focusing on the holding time in step S3. The required diffusion depth varies for different nickel-based superalloy materials, thus the selected holding time differs. For example, for DZ406 material, a holding time of 2–4 hours is selected, while for K447A material, a holding time of 4–7 hours is selected. The test results are shown in the table below:

[0051]

[0052] As shown in the table above, the hollow turbine blades prepared using the aforementioned process passed the test for the depth of the infiltration layer. Figure 1a The microstructure of the DZ406 hollow turbine blade in this embodiment is shown. Figure 1b The metallographic structure of the infiltrated layer prepared using an infiltrated agent formulated with imported aluminum powder is shown. Figure 2a The microstructure of the diffusion layer of the K447A hollow turbine blade in this embodiment is shown. Figure 2b The metallographic structure of the infiltrated layer prepared using an infiltrate formulated with imported aluminum powder is shown; Figure 1a , Figure 2a aluminized layer and Figure 1b and Figure 2b Comparing the aluminized layers, these aluminized layers all have a two-layer structure and the aluminized layer structures are quite similar.

[0053] The table below compares the aluminum content of the infiltrated layers prepared using the infiltrator formulated in this embodiment and the infiltrator formulated with imported aluminum powder (hereinafter referred to as the imported infiltrator):

[0054]

[0055] As can be seen from the table above, the aluminum content of each layer of the infiltration layer obtained by using the infiltration agent of this invention is basically the same as that of the infiltration layer obtained by using the imported infiltration agent.

[0056] Therefore, the aluminizing agent of the present invention can rival imported aluminizing agents in terms of various properties such as aluminizing layer depth and oxidation resistance, thus truly realizing the domestic production of this aluminizing agent.

[0057] The aluminizing agent and diffusion layer process of the present invention can also be extended to other turbine components of various engine types such as turboshaft, turbofan and new generation turboprop / turboshaft, and can completely replace imported aluminizing agents, break the dependence on imported aluminizing agents, and significantly reduce the production cost of enterprises.

[0058] Example 3

[0059] This embodiment is based on Example 2, but the penetrant is recycled twice. Before each recycling, 0.8-1.2% by weight of aluminum powder and 0.6-1% by weight of ammonium chloride are added to the penetrant. Because the aluminum content and activator of the penetrant will decrease accordingly when it is reused, appropriate replenishment of the corresponding raw materials during reuse can maintain the activity and performance of the penetrant.

[0060] Figure 3a , Figure 3b and Figure 3c The metallographic structures of the infiltrated layer on the DZ406 hollow turbine blade are shown in the first, second, and third cycles of infiltrated agent utilization. Figure 4a , Figure 4b and Figure 4c The metallographic structures of the aluminized layer on the K447A hollow turbine blade after the first, second, and third use of the aluminizing agent are shown. As can be seen from the figure, the metallographic structure of the aluminized layer obtained in the latter two cycles is not substantially different from that obtained after the first use of the aluminizing agent, and the resulting aluminized layer fully meets the requirements of the relevant technical documents.

[0061] The aluminum content of the carburized layer obtained from the recycled carburizing agent is then tested and compared with the aluminum content of the carburized layer prepared with imported carburizing agent:

[0062] The aluminum content of the diffusion layer in the DZ406 hollow turbine blades is shown in the table below:

[0063]

[0064] The aluminum content of the diffusion layer in the K447A hollow turbine blades is shown in the table below:

[0065]

[0066] As can be seen from the data in the two tables above, the aluminum content of the infiltrated layer obtained after the infiltrated agent of the present invention is comparable to that of the infiltrated layer prepared with imported infiltrated agent.

[0067] Comparative Example 1

[0068] In this embodiment, the penetrant is prepared using the following mass fraction ratio:

[0069]

[0070] The above-mentioned infiltration agent was used to prepare an aluminized layer for DZ406 hollow turbine blades using the process shown in Example 2 above. The final measured depth of the infiltration layer was 30-40 μm, which is too deep and does not meet the required 10-30 μm, thus failing to meet the aluminization technical requirements for the parts.

[0071] Comparative Example 2

[0072] The difference between this comparative example and Example 2 lies in the aluminizing process in step S3: the furnace is heated to 300±10℃ within 0.9–1.2 hours, held for 1–2 hours, and then heated to 980℃ within 2.8–3.2 hours. Afterwards, two groups are tested for holding the temperature for 8 hours and 10 hours respectively. The parts are then cooled in the furnace to less than or equal to 100℃ before being removed and air-cooled. The depth of the aluminized layer is then checked. The following table shows the results of the aluminized layers obtained from the two groups of tests (groups four and five) and multiple tests using the process of Example 2 (groups one to three):

[0073]

[0074] As shown in the table above, different insulation times result in significant differences in the final aluminized layer depth. In this comparative example, the insulation times of both groups of experiments failed to achieve the required aluminized layer depth.

[0075] Obviously, the above embodiments are merely examples to clearly illustrate the technical solutions of the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A process for preparing an aluminized layer on a nickel-based superalloy part, characterized in that, The raw materials include the following mass fractions: 18%–22% aluminum powder, 0.5%–1.2% ammonium chloride, and the remainder being calcined alumina; the aluminum powder is gas-atomized aluminum powder with an aluminum content greater than 99.0%; the process includes the following steps: S1. Pickling: The parts are pickled with 100% hydrochloric acid to remove hydrogen after pickling; S2. First sandblasting: After sandblasting the parts, clean the surface of any remaining sand particles; S3. Aluminizing: The aluminizing agent is placed in the furnace chamber of the aluminizing furnace, and the parts are suspended in the furnace space by tooling; the furnace chamber is heated to a certain temperature and held for a period of time, then heated to a higher temperature within a specified time, held for a certain time, and then the parts are cooled; specifically: the furnace chamber is heated to 300±10℃ in 0.9~1.2h, held for 1~2h, then heated to 980±10℃ in 2.8~3.2h, and held for 2~7h. The parts are cooled with the furnace to less than or equal to 100℃ and then removed from the furnace and air-cooled. S4. Cleaning and drying: Clean the parts and then dry them; S5. Second sandblasting: Clean up residual sand particles after sandblasting of the parts; When the penetrant is a reusable penetrant, 0.8-1.2% aluminum powder and 0.6-1% ammonium chloride by weight should be added to the penetrant before use.

2. The process for preparing an aluminized layer on a nickel-based high-temperature alloy part according to claim 1, characterized in that, Step S1 involves pickling at room temperature for 1–5 minutes, followed by hydrogen removal at 180–200°C for at least 3 hours.

3. The process for preparing an aluminized layer on a nickel-based high-temperature alloy part according to claim 1, characterized in that, In step S2, the part is blown with 200-240 mesh corundum sand at a blowing pressure of less than or equal to 0.25 MPa.

4. The process for preparing an aluminized layer on a nickel-based high-temperature alloy part according to claim 1, characterized in that, In step S3, pure nickel wire is used to bind the parts and suspend them on the fixture. The distance between parts and between parts and the fixture is greater than or equal to 20mm.

5. The process for preparing an aluminized layer on a nickel-based high-temperature alloy part according to claim 1, characterized in that, In step S4, compressed air is used to clean the parts, followed by immersion in hot water for brushing, and then soaking in clean water. The parts are then dried by keeping them at 145±5℃ for 1 to 2 hours and then air-cooled.

6. The process for preparing an aluminized layer on a nickel-based high-temperature alloy part according to claim 1, characterized in that, In step S5, the part is blown with 200-240 mesh corundum sand at a pressure of less than or equal to 0.15 MPa.

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