Boron-containing high-performance cobalt-based high-temperature alloy and preparation method thereof

Abstract

The invention discloses a boron-containing high-performance cobalt-based high-temperature alloy and a preparation method thereof. The cobalt-based high-temperature alloy is prepared from the following components in percentage by mass: 0.15 to 0.35 percent of C, 24.5 to 25.5 percent of Cr, 9.5 to 10.5 percent of Ni, 7.5 to 8.5 percent of W, 0.2 to 1.2 percent of Si, 0.2 to 1.2 percent of Mn, 0.5 to 1.5 percent of Fe, 0.01 to 0.02 percent of B and the balance of Co and inevitable impurities. According to the method, the alloy components are optimized by introducing boron, the alloy content of the boron is controlled so that the boron can exist in a solid solution state in a grain boundary, the hardness of the cobalt-based high-temperature alloy at the room temperature is improved, the hardness is improved by 6.9% at most, the stability of the structure and performance of the cobalt-based high-temperature alloy in the service process is enhanced, and the application range of the cobalt-based high-temperature alloy is widened. And the preparation method adopts a vacuum non-consumable electric arc furnace to smelt alloy elements to obtain an alloy ingot, the operation is simple, the cost is low, and the economic benefit of the alloy is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of next-generation turbine blade materials for gas turbines, specifically to a boron-containing high-performance cobalt-based superalloy and its preparation method. Background Technology

[0002] Currently, cobalt-based superalloys have extremely important applications in the aerospace field, mainly used to manufacture key components of aero-engines such as turbine blades, combustion chambers, and turbine outer rings. These components need to operate under extreme high temperature, high pressure, and high-speed rotation conditions. The excellent high-temperature performance, oxidation resistance, and corrosion resistance of cobalt-based superalloys ensure that these components can operate stably for a long time under extreme conditions.

[0003] Hardness is one of the important mechanical properties of cobalt-based superalloys. It directly affects the material's wear resistance, machinability, and resistance to deformation. During service, the alloy is subjected to high-speed airflow, high-temperature combustion gases, and particle abrasion. Simultaneously, the alloy is subjected to various stresses during service. Therefore, ensuring that cobalt-based superalloys maintain high hardness during service is an important consideration when designing alloy composition. Summary of the Invention

[0004] The purpose of this invention is to provide a novel high-performance cobalt-based superalloy containing boron and its preparation method, which can improve the hardness of cobalt-based superalloys and enhance their stability under complex service environments such as high temperature and high stress.

[0005] To achieve the above objectives, the present invention employs the following technical solution: a boron-containing high-performance cobalt-based superalloy, wherein the mass percentages of each component of the cobalt-based superalloy are: C: 0.15–0.35%, Cr: 24.5–25.5%, Ni: 9.5–10.5%, W: 7.5–8.5%, Si: 0.2–1.2%, Mn: 0.2–1.2%, Fe: 0.5–1.5%, B: 0.01–0.02%, with the balance being Co and unavoidable impurities.

[0006] Furthermore, the mass percentages of each component in the cobalt-based superalloy are as follows: C: 0.15%, Cr: 24.5%, Ni: 9.5%, W: 7.5%, Si: 0.2%, Mn: 0.2%, Fe: 0.5%, B: 0.01-0.02%, with the balance being Co; and at room temperature, the average Vickers hardness of the cobalt-based superalloy is 306.

[0007] Furthermore, the mass percentages of each component in the cobalt-based superalloy are as follows: C: 0.35%, Cr: 25.5%, Ni: 10.5%, W: 8.5%, Si: 1.2%, Mn: 1.2%, Fe: 1.5%, B: 0.01-0.02%, with the balance being Co. At room temperature, the average Vickers hardness of the cobalt-based superalloy is 300.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned cobalt-based superalloy, the method specifically comprising the following steps: S1) First, each raw material is subjected to ultrasonic treatment and drying treatment, and then each raw material is weighed according to the design ratio for later use; S2) Mix the raw materials processed in S1) and place them in the furnace cavity. First, evacuate the furnace cavity, then fill the furnace cavity with a protective atmosphere, and perform multiple melting processes under a certain current to obtain a high-performance cobalt-based high-temperature alloy containing boron.

[0009] Furthermore, the specific steps of S1 are as follows: S1.1) Remove impurities and oxide scale from the surface of the selected raw material block, place it in anhydrous ethanol for ultrasonic vibration cleaning to remove surface impurities, and then dry it. S1.2) Weigh the raw material blocks after processing S1.1) according to the design ratio calculation. Place the weighed mixed raw materials and oxygen-consuming titanium ingots into the copper crucible of the vacuum non-consumable electric arc furnace. Furthermore, the specific step of S2 is as follows: evacuate to 5 × 10⁻⁶. -3 Below Pa, a protective atmosphere is introduced at a pressure of 0.02 MPa. After the residual oxygen is consumed by titanium ingots, the mixed material is smelted at least 10 times. Each smelting time is 2 to 3 minutes, and the current during smelting is 200A-250A. The mixture needs to be turned over after each smelting.

[0010] Furthermore, the protective atmosphere is high-purity argon.

[0011] One of the aforementioned cobalt-based superalloys is used in the manufacture of key components of aero-engines, such as turbine blades, combustion chambers, and turbine outer rings.

[0012] Boron has advantages in improving the strength of cobalt-based superalloys. By controlling the boron content, it can prevent the formation of bulk borides. Instead, boron replaces some of the carbon in the carbides of cobalt-based superalloys, forming M(C,B) solid solutions and coherent CB structures. This reduces mismatch, resulting in a bulk distribution of carbides with smaller sizes, prolonged pinning action, and improved alloy strength.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present invention optimizes the alloy composition by introducing boron and controls the boron alloy content so that it can exist in a solid solution state at the grain boundaries, thereby improving the hardness of cobalt-based superalloys at room temperature by up to 6.9%, enhancing the stability of its structure and performance during service, and broadening the application range of cobalt-based superalloys.

[0014] The present invention also discloses a method for preparing the above-mentioned high-performance cobalt-based high-temperature alloy containing boron. The alloying elements are melted in a vacuum non-consumable arc furnace to obtain alloy ingots. The method is simple to operate and low in cost, which greatly improves the economic benefits of the alloy. Attached Figure Description

[0015] Figure 1 SEM image of the high-performance cobalt-based superalloy with added boron prepared in Example 1.

[0016] Figure 2 The image shows a SEM image of the cobalt-based superalloy without boron in Comparative Example 1.

[0017] Figure 3 The image shows a comparison of the Vickers hardness of the as-cast cobalt-based superalloys prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0018] The present invention will be further described below with reference to specific embodiments. Unless otherwise specified, the methods described are conventional methods, and the raw materials described are obtainable from publicly available commercial sources.

[0019] In the following embodiments: The purity (mass percentage, wt%) of the elemental substances corresponding to C, Cr, Ni, W, Si, Mn, Fe, Co and B is all greater than 99.9%; Hardness test: HV-50 Vickers hardness tester test parameters, loading force 1kN, loading time 15s, 12 points of hardness value for each test, remove the maximum and minimum values, and take the average of the remaining values.

[0020] Microstructure characterization: The microstructure of the prepared as-cast cobalt-based superalloy was observed using a Supra 55 field emission scanning electron microscope (SEM) manufactured by Zeiss, Germany. Columnar samples with dimensions of Φ8×8mm were cut using wire EDM. The surfaces of the samples were polished smooth using 60#, 400#, 800#, and 2000# sandpaper, respectively. The samples were then mechanically polished with diamond polishing paste on a metallographic polishing machine. Electropolishing was performed using a solution of 20 vol% concentrated sulfuric acid + 80 vol% methanol (volume fraction) at a voltage of 9–10 V for approximately 5 seconds. Electrolytic etching was then performed using an electrolyte solution of 15 g chromium oxide + 150 ml phosphoric acid + 10 ml concentrated sulfuric acid at a voltage of 4.5–5 V for approximately 2 seconds. The samples were then ultrasonically cleaned in anhydrous ethanol. After thorough drying, the samples were observed under an electron microscope.

[0021] Example 1 A method for preparing a novel high-performance cobalt-based superalloy containing boron includes the following steps: Raw material preparation: Calculate and take a fixed amount of raw material blocks containing C, Cr, Ni, W, Si, Mn, Fe, Co, and B. After sanding off impurities and oxide scale from the surface of the raw materials, place all weighed raw materials in anhydrous ethanol for ultrasonic cleaning to further remove surface impurities, followed by drying. Finally, accurately weigh the required mass of raw materials on a balance.

[0022] The mass percentages of the components in the cobalt-based superalloy are as follows: C: 0.15%, Cr: 25.5%, Ni: 10.5%, W: 8.5%, Si: 1.2%, Mn: 1.2%, Fe: 1.5%, and B: 0.02%, with the balance being Co.

[0023] Melting and preparation: The raw materials are placed in a small vacuum non-consumable arc furnace for melting to obtain a new high-performance cobalt-based superalloy containing boron. The current requirement during melting is 200A. Before melting, the vacuum degree of the vacuum non-consumable arc furnace needs to be evacuated to 5×10⁻⁶. - 3 The melting time is below Pa. Each melting session takes 3 minutes, and the current requirement during melting is 200A. The alloy must be flipped after each melting session, and the melting process is repeated 13 times to obtain the alloy ingot.

[0024] Table 1 shows the Vickers hardness test results for Example 1: Metallographic sample preparation and scanning analysis: Metallographic samples from Example 1 were prepared. After mechanical polishing to improve the surface finish, the samples underwent electropolishing and electrolytic etching to meet testing requirements. SEM was used to observe the precipitation at grain boundaries, and SEM-EDS was used to observe the elemental distribution at the grain boundaries.

[0025] Table 2 shows the SEM-EDS results for Example 1: .

[0026] Example 2: A method for preparing a novel high-performance cobalt-based superalloy containing boron includes the following steps: Raw material preparation: Calculate and take a fixed amount of raw material blocks containing C, Cr, Ni, W, Si, Mn, Fe, Co, and B. After sanding off impurities and oxide scale from the surface of the raw materials, place all weighed raw materials in anhydrous ethanol for ultrasonic cleaning to further remove surface impurities, followed by drying. Finally, accurately weigh the required mass of raw materials on a balance.

[0027] The mass percentages of the components in the cobalt-based superalloy are as follows: C: 0.35%, Cr: 24.5%, Ni: 9.5%, W: 7.5%, Si: 0.2%, Mn: 0.2%, Fe: 0.5%, and B: 0.01%, with the balance being Co.

[0028] Melting and preparation: The raw materials are placed in a small vacuum non-consumable arc furnace for melting to obtain a new high-performance cobalt-based superalloy containing boron. The current requirement during melting is 250A. Before melting, the vacuum degree of the vacuum non-consumable arc furnace needs to be evacuated to 5×10⁻⁶. - 3 The melting time is below Pa. Each melting session takes 2 minutes, and the current requirement during melting is 250A. The alloy must be flipped after each melting session. After repeating the melting process 10 times, an ingot of the alloy is obtained. The average Vickers hardness is 300.

[0029] Example 3: A method for preparing a novel high-performance cobalt-based superalloy containing boron includes the following steps: Raw material preparation: Calculate and take quantitative amounts of raw material blocks containing C, Cr, Ni, W, Si, Mn, Fe, Co, and B. After sanding off impurities and oxide scale from the surface of the raw materials, place all weighed raw materials in anhydrous ethanol for ultrasonic cleaning to further remove surface impurities, followed by drying. Finally, accurately weigh the required mass of raw materials on a balance; the mass percentage of each component is the same as in Example 1.

[0030] Melting and preparation: The raw materials are placed in a small vacuum non-consumable arc furnace for melting to obtain a new high-performance cobalt-based superalloy containing boron. The current requirement during melting is 225A. Before melting, the vacuum degree of the vacuum non-consumable arc furnace needs to be evacuated to 5×10⁻⁶. - 3 The melting time is below Pa. Each melting session takes 2.5 minutes, and the current requirement during melting is 225A. The alloy must be flipped after each melting session. After repeating the melting process 12 times, an ingot of the alloy is obtained. The average Vickers hardness is 303.

[0031] Comparative Example 1 A method for preparing a cobalt-based superalloy without added boron includes the following steps: Raw material preparation: Calculate and take a fixed amount of raw material blocks of C, Cr, Ni, W, Si, Mn, Fe, and Co. After sanding off impurities and oxide scale from the surface of the raw materials with sandpaper, place all weighed raw materials in anhydrous ethanol for ultrasonic cleaning to further remove surface impurities, followed by drying. Finally, accurately weigh the required mass of raw materials on a balance.

[0032] Melting and preparation: The raw materials are placed in a small vacuum non-consumable arc furnace for melting to obtain a cobalt-based superalloy. The current required during melting is 200A-250A. Before melting, the vacuum degree of the vacuum non-consumable arc furnace needs to be evacuated to 5×10⁻⁶. -3 The melting time is below Pa. The melting time is 2 to 3 minutes, and the current requirement during melting is 200A-250A. The alloy needs to be flipped after each melting and the melting is repeated at least 10 times to obtain the alloy ingot.

[0033] Table 3 shows the Vickers hardness test results for Comparative Example 1: Metallographic sample preparation and scanning analysis: Metallographic samples of Comparative Example 1 were prepared. After mechanical polishing to improve the surface finish, the samples underwent electropolishing and electrolytic etching to meet testing requirements. SEM was used to observe the precipitation at grain boundaries, and SEM-EDS was used to observe the elemental distribution at the grain boundaries.

[0034] Table 4 shows the SEM-EDS results for Comparative Example 1: Elemental segregation occurs during alloy smelting, and carbides are prone to precipitate at grain boundaries.

[0035] Figure 3 The results show a columnar comparison of the hardness of the cobalt-based superalloys prepared in Example 1 and Comparative Example 1.

[0036] Based on the SEM-EDS and Vickers hardness analyses of Example 1 and Comparative Example 1, boron, when introduced into cobalt-based superalloys, exists in solid solution form at grain boundaries, causing grain boundary strengthening, which leads to increased hardness and enhanced performance of the alloy.

[0037] The foregoing has provided a detailed description of a novel high-performance cobalt-based high-temperature alloy containing boron and its preparation method, as provided in the embodiments of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this application; furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

[0038] Certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that hardware manufacturers may use different names to refer to the same component. This specification and claims do not distinguish components based on differences in name, but rather on differences in function. The terms "comprising" and "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising / including but not limited to". "Approximately" means that within an acceptable margin of error, those skilled in the art can solve the technical problem and substantially achieve the technical effect within a certain margin of error. The following descriptions in the specification are preferred embodiments for carrying out this application; however, these descriptions are for the purpose of illustrating the general principles of this application and are not intended to limit the scope of this application. The scope of protection of this application shall be determined by the appended claims.

[0039] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a product or system comprising a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a product or system. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the product or system that includes said element.

[0040] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0041] The foregoing description illustrates and describes several preferred embodiments of this application. However, as previously stated, it should be understood that this application is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the application concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this application should be within the protection scope of the appended claims.

Claims

1. A high performance cobalt-based superalloy containing boron, characterized in that, The mass percentage of each component of the cobalt-based high-temperature alloy is: C: 0.15-0.35%, Cr: 24.5-25.5%, Ni: 9.5-10.5%, W: 7.5-8.5%, Si: 0.2-1.2%, Mn: 0.2-1.2%, Fe: 0.5-1.5%, B: 0.01-0.02%, and the balance is Co and inevitable impurities.

2. The cobalt-based superalloy of claim 1, wherein, The mass percentage of each component of the cobalt-based high-temperature alloy is: C: 0.15%, Cr: 24.5%, Ni: 9.5%, W: 7.5%, Si: 0.2%, Mn: 0.2%, Fe: 0.5%, B: 0.01-0.02%, and the balance is Co; and the average Vickers hardness of the cobalt-based high-temperature alloy at room temperature is 306.

3. The cobalt-base superalloy of claim 1, wherein, The mass percentage of each component of the cobalt-based high-temperature alloy is: C: 0.35%, Cr: 25.5%, Ni: 10.5%, W: 8.5%, Si: 1.2%, Mn: 1.2%, Fe: 1.5%, B: 0.01-0.02%, and the balance is Co; and the average Vickers hardness of the cobalt-based high-temperature alloy at room temperature is 300.

4. A method of producing a cobalt-based superalloy as claimed in any one of claims 1 to 3, characterised in that, The method specifically comprises the following steps: S1) ultrasonic treatment and drying treatment are first performed on each raw material, and then each raw material is weighed according to the designed ratio for standby; S2) each raw material treated in S1) is mixed and placed in a furnace cavity, vacuum is first drawn on the furnace cavity, then a protective atmosphere is filled into the furnace cavity, and multiple melting is performed under a certain current, so that the high-performance cobalt-based high-temperature alloy containing boron is obtained.

5. The preparation method according to claim 4, characterized in that, The specific steps of S1) are: S1.1) remove the impurities and oxide skin on the surface of the selected raw material block, place it in anhydrous ethanol for ultrasonic oscillation cleaning, so as to remove the impurities on the surface, and perform drying treatment; S1.2) the mass of each raw material is calculated according to the designed ratio, the raw material block treated in S1.1) is weighed, and the weighed mixed raw material and titanium ingot consuming oxygen are placed in the copper crucible of the vacuum non-consumable arc furnace.

6. The preparation method according to claim 4, characterized in that, S2) The specific step is: vacuumizing to 5 × 10 -3 Pa, filling protective atmosphere, pressure is 0.02MPa, using titanium ingot to consume residual oxygen, then melting the mixed material for at least 10 times; each melting time is 2-3 minutes, the current during melting is 200A-250A, and turning over is needed after each melting.

7. The preparation method according to claim 6, characterized in that, The protective atmosphere is high-purity argon.

8. The cobalt-based high-temperature alloy according to any one of claims 1-3 is applied to the manufacture of key components of turbine blades, combustion chambers and turbine outer rings of an aero-engine.

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