A nickel-tantalum master alloy and its preparation method

Abstract

This invention discloses a nickel-tantalum master alloy, comprising, by mass percentage: 40.0%–50.0% nickel, with the balance being tantalum and unavoidable impurities. The nickel-tantalum master alloy is prepared from nickel foil, nickel suboxide, tantalum pentoxide, aluminum powder, and calcium granules. The specific preparation method is as follows: nickel suboxide, tantalum pentoxide, and aluminum powder are mixed uniformly to obtain a mixture; calcium granules are spread evenly at the bottom of a crucible in a vacuum aluminothermic reaction furnace, and a layer of calcium oxide slurry is coated onto the inner wall of the crucible. After drying, the mixture is added to perform a vacuum aluminothermic / calcothermic reduction reaction to obtain a nickel-tantalum alloy liquid. After cooling, a primary nickel-tantalum alloy is obtained; tantalum pentoxide is wrapped in nickel foil to form multiple bales; the primary nickel-tantalum alloy is crushed, and the wrapped bales and crushed primary nickel-tantalum alloy are melted in a vacuum electron beam furnace; the melted alloy liquid is cooled to obtain the nickel-tantalum master alloy. The nickel-tantalum master alloy obtained by this invention has high uniformity and high purity.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials technology and relates to a high-purity nickel-tantalum master alloy and its preparation method. Background Technology

[0002] Nickel-based superalloys possess high-temperature strength and structural stability, and are widely used in the manufacture of hot-end components for aero-jet engines and industrial gas turbines. Nickel-based superalloys are high-temperature alloys with nickel as the base material (generally containing more than 50%), exhibiting high strength and good resistance to oxidation and gas corrosion in the temperature range of 650–1000℃. They are developed based on the Cr20Ni80 alloy. To meet the requirements of high-temperature thermal strength around 1000℃ and resistance to oxidation and corrosion in gaseous media, a large number of strengthening elements, such as W, Mo, Ti, Al, and Ta, are added to ensure their superior high-temperature performance. Among these, Ta can significantly improve the alloy's high-temperature resistance to hot corrosion and structural stability.

[0003] The melting point of metallic nickel is 1453.0℃, and its density is 8.90 g / cm³. 3 Tantalum has a melting point of 2996℃ and a density of 16.68 g / cm³. 3 In the production of high-temperature alloys, if metals are added directly in elemental form, element loss and segregation of refractory elements can easily occur due to differences in melting point and density. However, nickel-tantalum master alloys have a melting point close to that of metallic nickel, thus neutralizing the differences in melting point and density between nickel and tantalum. When high-temperature alloys are smelted using nickel-tantalum master alloys, the element loss rate is low, and the resulting high-temperature alloys have a uniform composition and no segregation.

[0004] However, tantalum is expensive and not suitable for mass production. At the same time, the high melting temperature and complex preparation process lead to high equipment requirements in industrial production, which in turn increases production costs.

[0005] Therefore, how to develop a high-purity nickel-tantalum master alloy to improve the overall performance of nickel-based superalloys is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a nickel-tantalum master alloy and its preparation method, so as to improve the overall performance of nickel-based superalloys.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The primary technical objective of this invention is to provide a high-purity nickel-tantalum master alloy, comprising, by mass percentage: 40.0% to 50.0% nickel, with the balance being tantalum and unavoidable impurities.

[0009] The nickel-tantalum master alloy provided by this invention has a uniform composition and low impurity content, which helps to homogenize and purify the composition of high-temperature alloys during smelting.

[0010] Optionally, the nickel-tantalum master alloy comprises, by weight percentage: 42.0% to 48.0% nickel, with the balance being tantalum and unavoidable impurities.

[0011] Furthermore, by mass percentage, the nickel-tantalum master alloy comprises: 45% nickel, with the balance being tantalum and unavoidable impurities.

[0012] It should be noted that when the nickel content is below 40%, a eutectic structure will be formed, resulting in higher alloy strength and hardness, but making it difficult to process. When the nickel content is above 50%, the tantalum content is low, and the purpose of introducing tantalum cannot be achieved.

[0013] The second technical objective of this invention is to provide a method for preparing a high-purity nickel-tantalum master alloy, specifically including the following steps:

[0014] (1) Mix nickel oxide, tantalum pentoxide and aluminum powder evenly to obtain a mixture;

[0015] (2) Spread calcium particles evenly on the bottom of the crucible of the vacuum aluminothermic reaction furnace, and coat the inner wall of the crucible with a layer of calcium oxide liquid. After drying, add the mixed materials to carry out the vacuum aluminothermic / calcothermic reduction reaction to obtain nickel-tantalum alloy liquid. After cooling, obtain a first-grade nickel-tantalum alloy.

[0016] (3) Wrap tantalum pentoxide in nickel foil to form multiple packages, crush the first-grade nickel-tantalum alloy, and melt the packaged packages and the crushed first-grade nickel-tantalum alloy in a vacuum electron beam furnace.

[0017] (4) After the alloy liquid smelted in step (3) is cooled, the high-purity nickel-tantalum master alloy is obtained.

[0018] Optionally, in step (1), the mass ratio of nickel oxide, tantalum pentoxide, and aluminum powder is (0.968~1.072):(1.618~1.993):(0.528~0.573).

[0019] It should be noted that in this invention, nickel oxide, tantalum pentoxide, and aluminum powder are the raw materials for the aluminothermic reduction reaction. Each raw material is preferably in powder form, which increases the contact area of ​​the aluminothermic reduction reaction and makes the reaction more complete and uniform.

[0020] Furthermore, before mixing, nickel oxide, tantalum pentoxide, and aluminum powder are dried separately at a temperature of 100℃ to 120℃ for 12 to 20 hours.

[0021] It is worth noting that drying can remove the moisture absorbed by the material, ensuring that the material is dry, thereby reducing the release of impurity gases (such as hydrogen, nitrogen, oxygen, etc.) during the smelting process. The temperature is controlled between 100℃ and 120℃, and the time is controlled between 12 and 20 hours to ensure that the material is completely dried. If the temperature is too low or the time is too short, the material will not be completely dried, while if the temperature is too high or the time is too long, resources will be wasted.

[0022] Optionally, the mass ratio between the amount of calcium metal particles added in a flat manner at the bottom and the amount of aluminum powder added in step (1) is (0.996-1.031):(8.977-9.022), and the temperature of the aluminothermic / calcothermic reduction reaction is 3000℃-3200℃, and the time is 30-42s.

[0023] Calothermic reduction generates more heat than aluminothermic reduction, allowing the alloy to remain in a molten state for a longer period. The calcium oxide produced in the reaction also acts as a slag-forming agent, lowering the initial crystallization temperature of the slag and reducing inclusions in the alloy. Spreading calcium particles evenly at the bottom prolongs the time calcium oxide spends floating in the molten alloy, resulting in a long-lasting slag-forming effect.

[0024] Furthermore, the aluminothermic reaction occurs under vacuum conditions inside the vacuum aluminothermic furnace, preventing the metals from undergoing oxidation or nitriding reactions with oxygen and nitrogen in the air.

[0025] Furthermore, coating the inner wall of the crucible with a layer of calcium oxide liquid can prevent the alloy melt from corroding the crucible and introducing impurities.

[0026] Preferably, in step (3), the number of nickel foil-wrapped tantalum pentoxide packages is 7-11, and the weight ratio of nickel foil to tantalum pentoxide in each package is (7.49-7.51):1.

[0027] Furthermore, in step (3), the vacuum degree of the vacuum electron beam furnace melting is ≤2Pa, and the size of the first-grade nickel-tantalum alloy and the packaged material is 5-10cm.

[0028] It should be noted that the added Ta2O5 removes the Al element from the primary alloy produced by the aluminothermic reduction method. It provides heat through a small amount of aluminothermic reduction process, which has a stirring effect, making the alloy more uniform and facilitating the floating of impurities. In addition, the purpose of wrapping Ta2O5 with nickel foil is to ensure that it enters the interior of the alloy liquid before reacting.

[0029] Furthermore, the electron gun inside the vacuum electron beam furnace emits electrons, causing the electron beam to bombard the surface of the vanadium-aluminum alloy. This converts the kinetic energy of the high-speed electrons into heat energy, melting the material. Under high vacuum conditions, impurities with high vapor pressure, such as iron (1538℃), silicon (1410℃), and aluminum (660℃), are removed.

[0030] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a nickel-tantalum master alloy and its preparation method, which have the following beneficial effects:

[0031] 1. This invention uses metallic calcium as a heating agent and produces a slag-forming agent, resulting in an alloy with few inclusions.

[0032] 2. The present invention uses a vacuum electron beam furnace for melting, resulting in alloys with low impurities, especially gaseous impurities.

[0033] 3. This invention introduces nickel foil-wrapped Ta2O5 into the alloy liquid, making the alloy more uniform and reducing the Al content. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] In the following embodiments, unless otherwise specified, the raw materials of the required components are all commercially available products well known to those skilled in the art;

[0036] Example 1

[0037] The preparation method of high-purity nickel-tantalum master alloy specifically includes the following steps:

[0038] (1) First, nickel oxide, tantalum pentoxide, aluminum powder and nickel foil are dried at 100℃ for 20h. Then, 26.12kg of nickel oxide, 53.66kg of tantalum pentoxide and 15.48kg of aluminum powder are weighed and put into a mixer to mix, so as to obtain a nickel-tantalum mixture. The mixing requirements are: all raw materials are fully and evenly mixed to ensure sufficient contact between raw materials.

[0039] (2) Spread 1.72 kg of calcium granules evenly on the bottom of the crucible of the vacuum aluminothermic reaction furnace, and coat the inner wall of the crucible with a layer of calcium oxide liquid. After drying, add the mixed materials to carry out the vacuum aluminothermic / calcothermic reduction reaction. After cooling for 12 hours, a first-grade nickel-tantalum alloy is obtained.

[0040] (3) Weigh 50kg of grade 1 nickel-tantalum alloy, wrap 0.12kg of tantalum pentoxide with 0.9kg of nickel foil to form a material bag, wrap a total of 7 material bags, place the grade 1 nickel-tantalum alloy and material bags evenly, and then melt them into liquid in a vacuum electron beam furnace, wherein the vacuum degree of melting is 2Pa;

[0041] (4) After the reaction, the power is turned off, the vacuum is maintained, and the furnace is cooled for 12 hours to obtain the target nickel-tantalum master alloy.

[0042] Example 2

[0043] The preparation method of high-purity nickel-tantalum master alloy specifically includes the following steps:

[0044] (1) First, nickel oxide, tantalum pentoxide, aluminum powder and nickel foil are dried at 100℃ for 20h. Then, 26.31kg of nickel oxide, 51.65kg of tantalum pentoxide and 15.15kg of aluminum powder are weighed and put into a mixer to mix and obtain a nickel-tantalum mixture. The mixing requirements are: all raw materials are fully mixed and evenly to ensure sufficient contact between raw materials.

[0045] (2) Spread 1.68 kg of calcium granules on the bottom of the crucible of the vacuum aluminothermic reaction furnace, and coat the inner wall of the crucible with a layer of calcium oxide liquid. After drying, add the mixed materials to carry out the vacuum aluminothermic / calcothermic reduction reaction. After cooling for 12 hours, a first-grade nickel-tantalum alloy is obtained.

[0046] (3) Weigh 50 kg of grade 1 nickel-tantalum alloy, wrap 0.12 kg of tantalum pentoxide with 0.9 kg of nickel foil to form a material bag, wrap a total of 8 material bags, place the grade 1 nickel-tantalum alloy and material bags evenly, and then melt them into liquid in a vacuum electron beam furnace, wherein the vacuum degree of melting is 1.8 Pa;

[0047] (4) After the reaction, the power is turned off, the vacuum is maintained, and the furnace is cooled for 12 hours to obtain the target nickel-tantalum master alloy.

[0048] Example 3

[0049] The preparation method of high-purity nickel-tantalum master alloy specifically includes the following steps:

[0050] (1) First, nickel oxide, tantalum pentoxide, aluminum powder and nickel foil are dried at 100℃ for 20h. Then, 27.46kg of nickel oxide, 48.72kg of tantalum pentoxide and 14.86kg of aluminum powder are weighed and put into a mixer to mix and obtain a nickel-tantalum mixture. The mixing requirements are: all raw materials are fully and evenly mixed to ensure sufficient contact between the raw materials.

[0051] (2) Spread 1.65 kg of calcium granules evenly on the bottom of the crucible of the vacuum aluminothermic reaction furnace, and coat the inner wall of the crucible with a layer of calcium oxide liquid. After drying, add the mixed materials to carry out the vacuum aluminothermic / calcothermic reduction reaction. After cooling for 12 hours, a first-grade nickel-tantalum alloy is obtained.

[0052] (3) Weigh 50 kg of grade 1 nickel-tantalum alloy, wrap 0.12 kg of tantalum pentoxide with 0.9 kg of nickel foil to form a material bag, wrap a total of 9 material bags, place the grade 1 nickel-tantalum alloy and material bags evenly, and then melt them into liquid in a vacuum electron beam furnace, wherein the vacuum degree of melting is 1.5 Pa;

[0053] (4) After the reaction, the power is turned off, the vacuum is maintained, and the furnace is cooled for 12 hours to obtain the target nickel-tantalum master alloy.

[0054] Example 4

[0055] The preparation method of high-purity nickel-tantalum master alloy specifically includes the following steps:

[0056] (1) First, nickel oxide, tantalum pentoxide, aluminum powder and nickel foil are dried at 100℃ for 20h. Then, 28.60kg of nickel oxide, 45.79kg of tantalum pentoxide and 14.57kg of aluminum powder are weighed and put into a mixer to mix, so as to obtain a nickel-tantalum mixture. The mixing requirements are: all raw materials are fully and evenly mixed to ensure sufficient contact between raw materials.

[0057] (2) Spread 1.62 kg of calcium granules evenly on the bottom of the crucible of the vacuum aluminothermic reaction furnace, and coat the inner wall of the crucible with a layer of calcium oxide liquid. After drying, add the mixed materials to carry out the vacuum aluminothermic / calcothermic reduction reaction. After cooling for 12 hours, a first-grade nickel-tantalum alloy is obtained.

[0058] (3) Weigh 50 kg of grade 1 nickel-tantalum alloy, wrap 0.12 kg of tantalum pentoxide with 0.9 kg of nickel foil to form a material bag, wrap a total of 10 material bags, place the grade 1 nickel-tantalum alloy and material bags evenly, and then melt them into liquid in a vacuum electron beam furnace, wherein the vacuum degree of melting is 1.5 Pa;

[0059] (4) After the reaction, the power is turned off, the vacuum is maintained, and the furnace is cooled for 12 hours to obtain the target nickel-tantalum master alloy.

[0060] Example 5

[0061] The preparation method of nickel-tantalum master alloy specifically includes the following steps:

[0062] (1) First, nickel oxide, tantalum pentoxide, aluminum powder and nickel foil are dried at 100℃ for 20h. Then, 28.79kg of nickel oxide, 43.77kg of tantalum pentoxide and 14.24kg of aluminum powder are weighed and put into a mixer to mix, so as to obtain a nickel-tantalum mixture. The mixing requirements are: all raw materials are fully and evenly mixed to ensure sufficient contact between raw materials.

[0063] (2) Spread 1.58 kg of calcium granules on the bottom of the crucible of the vacuum aluminothermic reaction furnace, and coat the inner wall of the crucible with a layer of calcium oxide liquid. After drying, add the mixture to carry out the vacuum aluminothermic / calcothermic reduction reaction. After cooling for 12 hours, a first-grade nickel-tantalum alloy is obtained.

[0064] (3) Weigh 50 kg of grade 1 nickel-tantalum alloy, wrap 0.12 kg of tantalum pentoxide with 0.9 kg of nickel foil to form a material bag, wrap a total of 11 material bags, place the grade 1 nickel-tantalum alloy and material bags evenly, and then melt them into liquid in a vacuum electron beam furnace, wherein the vacuum degree of melting is 1.5 Pa;

[0065] (4) After the reaction, the power is turned off, the vacuum is maintained, and the furnace is cooled for 12 hours to obtain the target nickel-tantalum master alloy.

[0066] Performance testing

[0067] Samples were taken from different locations on the nickel-tantalum master alloy ingots (cylinders) prepared in Examples 1 to 5 for chemical composition analysis. Three points were taken from the upper layer of the alloy ingot, numbered 1, 2, and 3 respectively; three points were taken from the middle layer of the alloy ingot, numbered 4, 5, and 6 respectively; and three points were taken from the lower layer of the alloy ingot, numbered 7, 8, and 9 respectively. The results are shown in Tables 1 to 5, and the optimal values ​​are shown in Table 6 (the balance is Ta).

[0068] Table 1. Chemical composition of different positions in the nickel-tantalum master alloy of Example 1.

[0069]

[0070] Table 2 Chemical composition of different positions in the nickel-tantalum master alloy of Example 2

[0071]

[0072] Table 3 Chemical composition of different positions in the nickel-tantalum master alloy of Example 3

[0073]

[0074] Table 4 Chemical composition of different positions in the nickel-tantalum master alloy of Example 4

[0075]

[0076] Table 5 Chemical composition of different positions in the nickel-tantalum master alloy of Example 5

[0077]

[0078]

[0079] Table 6 shows the optimal chemical composition values ​​of the nickel-tantalum master alloys in Examples 1-5.

[0080]

[0081] As shown in Tables 1-6, the nickel-tantalum master alloys prepared in Examples 1-5 of the present invention have uniform and stable composition and low impurity content.

[0082] Comparative Example 1

[0083] A method for preparing a nickel-tantalum master alloy specifically includes the following steps:

[0084] (1) First, nickel oxide, tantalum pentoxide, aluminum powder and nickel foil are dried at 100℃ for 20h. Then, 27.46kg of nickel oxide, 48.72kg of tantalum pentoxide and 14.86kg of aluminum powder are weighed and put into a mixer to mix and obtain a nickel-tantalum mixture. The mixing requirements are: all raw materials are fully and evenly mixed to ensure sufficient contact between the raw materials.

[0085] (2) Spread 1.65 kg of calcium granules evenly on the bottom of the crucible of the vacuum aluminothermic reaction furnace, and coat the inner wall of the crucible with a layer of calcium oxide liquid. After drying, add the mixed materials, wrap 0.12 kg of tantalum pentoxide with 0.9 kg of nickel foil to form a material bag, wrap a total of 9 material bags, place the material bags evenly in various positions of the material, and then carry out the vacuum aluminothermic / calcothermic reduction reaction. After cooling for 12 hours, the target nickel-tantalum alloy is obtained; the test results are shown in Table 7.

[0086] Table 7 shows the chemical composition of the alloy at different locations in Comparative Example 1.

[0087]

[0088] Comparative Example 2

[0089] A method for preparing a nickel-tantalum master alloy specifically includes the following steps:

[0090] (1) First, nickel oxide, tantalum pentoxide, aluminum powder and nickel foil are dried at 100℃ for 20h. Then, 27.46kg of nickel oxide, 48.72kg of tantalum pentoxide and 14.86kg of aluminum powder are weighed and put into a mixer to mix and obtain a nickel-tantalum mixture. The mixing requirements are: all raw materials are fully and evenly mixed to ensure sufficient contact between the raw materials.

[0091] (2) Spread 1.65 kg of calcium granules evenly on the bottom of the crucible of the vacuum aluminothermic reaction furnace, and coat the inner wall of the crucible with a layer of calcium oxide liquid. After drying, add the mixed materials to carry out the vacuum aluminothermic / calcothermic reduction reaction. After cooling for 12 hours, a first-grade nickel-tantalum alloy is obtained.

[0092] (3) Weigh 50 kg of grade 1 nickel-tantalum alloy and melt it into a liquid in a vacuum electron beam furnace, wherein the vacuum degree of the melting is 1.5 Pa;

[0093] (4) After the reaction, the power was turned off, the vacuum was maintained, and the furnace was removed after cooling for 12 hours to obtain the target nickel-tantalum master alloy; the test results are shown in Table 8.

[0094] Table 8 shows the chemical composition of the alloy at different locations in Comparative Example 2.

[0095]

[0096] As can be seen from the data in Tables 7 and 8, the present invention uses a vacuum electron beam furnace for melting, resulting in alloys with low impurities, especially gaseous impurities; and the present invention introduces nickel foil-wrapped Ta2O5 into the alloy liquid, making the alloy more uniform and with a lower Al content.

[0097] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for producing a high-purity nickel tantalum master alloy, characterized by, Specifically, the following steps are included: (1) Mix nickel oxide, tantalum pentoxide and aluminum powder evenly to obtain a mixture; (2) Spread calcium particles evenly on the bottom of the crucible of the vacuum aluminothermic reaction furnace, and coat the inner wall of the crucible with a layer of calcium oxide liquid. After drying, add the mixed materials to carry out the vacuum aluminothermic / calcothermic reduction reaction to obtain nickel-tantalum alloy liquid. After cooling, obtain a first-grade nickel-tantalum alloy. (3) Wrap tantalum pentoxide in nickel foil to form multiple packages, crush the first-grade nickel-tantalum alloy, and melt the packaged packages and the crushed first-grade nickel-tantalum alloy in a vacuum electron beam furnace. (4) After the alloy liquid smelted in step (3) is cooled, the nickel-tantalum master alloy is obtained; The nickel-tantalum master alloy comprises, by mass percentage: 40.0% to 50.0% nickel, with the balance being tantalum and unavoidable impurities.

2. The method for preparing a high-purity nickel-tantalum master alloy according to claim 1, characterized in that, In step (1), the mass ratio of nickel oxide, tantalum pentoxide, and aluminum powder is (0.968~1.072):(1.618~1.993):(0.528~0.573).

3. The method for preparing a high-purity nickel-tantalum master alloy according to claim 1 or 2, characterized in that, The nickel oxide, tantalum pentoxide, aluminum powder, nickel foil, and tantalum pentoxide all need to be dried. The drying temperature is 100℃~120℃ and the time is 12~20h.

4. The method for preparing a high-purity nickel-tantalum master alloy according to claim 1, characterized in that, In step (2), the mass ratio of calcium particles to aluminum powder is (0.996-1.031):(8.977-9.022), and the temperature of the aluminothermic / calcothermic reduction reaction is 3000℃-3200℃, and the time is 30~42s.

5. The method for preparing a high-purity nickel-tantalum master alloy according to claim 1, characterized in that, In step (3), the number of nickel foil-wrapped tantalum pentoxide packages is 7-11, and the weight ratio of nickel foil to tantalum pentoxide in each package is (7.49-7.51):

1.

6. The method for preparing a high-purity nickel-tantalum master alloy according to claim 1 or 5, characterized in that, The vacuum degree of the vacuum electron beam furnace is ≤2Pa, and the size of the first-grade nickel-tantalum alloy and the packaged material is 5-10cm.

7. The method for preparing a high-purity nickel-tantalum master alloy according to claim 1, characterized in that, The nickel-tantalum master alloy comprises, by mass percentage: 42.0% to 48.0% nickel, with the balance being tantalum and unavoidable impurities.

8. The method for preparing a high-purity nickel-tantalum master alloy according to claim 1 or 7, characterized in that, The nickel-tantalum master alloy comprises, by weight percentage: 45% nickel, with the balance being tantalum and unavoidable impurities.

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