Method for preparing spherical powder of intermetallic compound

Abstract

The invention discloses a method for preparing intermetallic compound spherical powder, which comprises the following steps: (1) powder mixing: mixing multiple metal element powder capable of generating intermetallic compounds according to a required proportion to obtain mixed metal element powder; (2) pressing forming is conducted, specifically, the mixed metal element powder is pressed and formed through cold isostatic pressing, and a pressed blank is obtained; (3) alloying the pressed blank: reacting the pressed blank at a certain temperature to synthesize an intermetallic compound blank; (4) crushing into powder: mechanically crushing the intermetallic compound blank into powder; and (5) plasma spheroidization: performing plasma spheroidization on the crushed powder. According to the method, the metal element powder is creatively used as the raw material, the intermetallic compound is generated and then crushed and spheroidized to form the spherical powder, the process that an intermetallic compound bar needs to be prepared through smelting in a traditional preparation method is omitted, the preparation process is shortened, the production cost is reduced, the production process is simple, and energy consumption is low.

Description

Technical Field

[0001] The invention relates to the field of preparation of spherical metal powders, and more particularly to a method for preparing spherical intermetallic compound powders. Background Art

[0002] Intermetallic compounds have superior properties in high temperature, electromagnetic and superconductivity, but their development and application are limited by their poor room temperature plasticity and processing difficulties. Taking titanium-aluminum-based intermetallic compounds (titanium-aluminum alloys) as an example, they are mainly composed of three phases, namely Ti3Al, TiAl and TiAl3. They have low density, high strength, high melting point and excellent creep resistance, oxidation resistance and high temperature resistance. They can replace high-temperature alloys for aerospace structural parts in the temperature range of 600-900 degrees, and have received extensive attention in the structural materials of the aerospace and automotive industries. Titanium-aluminum alloys are traditionally vacuum melted and then subjected to hot processing such as forging. The grains of vacuum-melted titanium-aluminum-based intermetallic compound ingots are coarse, the composition segregation is serious, and the mechanical properties of the alloy are poor. At the same time, titanium-aluminum-based intermetallic compounds generally have low room temperature plasticity and poor processing performance. Therefore, titanium-aluminum alloy billet forging generally adopts isothermal forging, which has high processing costs, is difficult to deform, and has a very low material utilization rate, which limits its application.

[0003] Additive manufacturing is a new type of processing and preparation technology developed in recent years. It can achieve near-net forming and is a forming method for intermetallic compounds that has attracted much attention in recent years. It can overcome the problem of difficult forming and processing of intermetallic compounds. Currently, the more popular intermetallic compound additive manufacturing generally uses spherical intermetallic compound powder as raw material to synthesize intermetallic compounds through powder metallurgy process. The manufacturing method of spherical powder of intermetallic compounds generally adopts gas atomization method, rotating electrode method, mechanical alloying combined with plasma spheroidization method, etc. Among them, gas atomization and rotating electrode method both need to prepare alloy rods of suitable size first, but the processing and manufacturing cost of alloy rods of intermetallic compounds is high, and mechanical alloying combined with plasma spheroidization method generally uses metal element powder for ball milling, but it is difficult to control the powder particle size and purity during ball milling alloying process, and it is difficult to control oxygen during long-term ball milling process. Too high oxygen content affects the quality of powder.

[0004] Therefore, it is of great significance to develop a low-cost, high-quality preparation method for intermetallic compound spherical powders. Summary of the invention

[0005] The object of the present invention is to solve or at least partially alleviate the above problems by providing a method for preparing spherical powder of intermetallic compounds.

[0006] According to the present invention, there is provided a method for preparing spherical intermetallic compound powder, comprising:

[0007] (1) Powder mixing: mixing a plurality of metal element powders capable of forming an intermetallic compound in a desired proportion to obtain a mixed metal element powder;

[0008] (2) Pressing and forming: Pressing and forming the mixed metal element powder by cold isostatic pressing to obtain a pressed blank;

[0009] (3) Alloying of pressed billets: reacting the pressed billets of mixed metal element powders at a certain temperature to synthesize intermetallic compound billets;

[0010] (4) Crushing into powder: Mechanically crushing the intermetallic compound blank after reaction synthesis into powder;

[0011] (5) Plasma spheroidization: The obtained intermetallic compound powder is spheroidized by plasma to obtain spherical intermetallic compound powder.

[0012] Preferably, the mechanical crushing into powder in step (4) comprises ball milling the intermetallic compound blank into powder or hammering the intermetallic compound blank into powder.

[0013] Preferably, in step (4), after the powder is mechanically crushed, a powder screening step is further included to obtain intermetallic compound powder of appropriate size, and then spherical intermetallic compound powder is obtained by plasma spheroidization.

[0014] Preferably, after step (5), a powder screening step is further included to obtain spherical intermetallic compound powder of appropriate size.

[0015] Preferably, the metal element powder is titanium powder and aluminum powder, or titanium powder, aluminum powder and other metal element powders, and the other metal element powders are selected from one or more of the group consisting of Cr, Nb, Fe, Zr, B, C, W, Mo, Mn, La, Si, Sn, Ni, V, and Ta.

[0016] Preferably, the titanium powder is pure titanium powder or hydrogen-containing titanium powder, and the hydrogen content is 0.1% to 4%.

[0017] Preferably, the weight percentage of the powder is 35 wt.% to 50 wt.%.

[0018] Preferably, in step (3), the reaction synthesis temperature is 700-1000 degrees Celsius.

[0019] Preferably, in step (4), high-purity argon is used as the protective atmosphere.

[0020] Preferably, in the case of obtaining spherical intermetallic compound powder by plasma spheroidization, the gas flow rate is 10 to 100 L / min, the power is 30 to 100 kW, and the powder feeding amount is 5 to 100 g / min.

[0021] The method for preparing spherical powder of intermetallic compound of the present invention creatively utilizes powder of single metal element as raw material, generates intermetallic compound and then crushes it to form spherical powder, thereby reducing the need for smelting to prepare intermetallic compound rods in the traditional method for preparing spherical powder of intermetallic compound, shortening the preparation process, reducing production costs, simplifying the production process and reducing energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0023] Figure 1 is a flow chart showing the principle of the method for preparing spherical powder of intermetallic compound according to the present invention;

[0024] Figure 2 is a flow chart of a method for preparing spherical powder of titanium-aluminum-based intermetallic compound according to a preferred embodiment of the present invention;

[0025] Figure 3 is a morphology diagram of titanium-aluminum-based intermetallic compound spherical powder obtained according to the method for preparing intermetallic compound spherical powder of the present invention;

[0026] Figure 4 yes Figure 3 A partial enlarged view of the morphology shown in . DETAILED DESCRIPTION

[0027] The present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It is also necessary to explain that, for ease of description, only the parts related to the invention are shown in the accompanying drawings.

[0028] In the method of additive manufacturing of intermetallic compounds, in addition to the preparation by powder metallurgy using spherical powder of intermetallic compounds as raw materials as described in the background technology, metal element powders can also be used as raw materials, and powder metallurgy processes are performed after pressing and molding at room temperature to obtain intermetallic compounds. However, the intermetallic compounds obtained by using metal element powders as raw materials usually have a non-dense and non-uniform structure, and the mechanical properties of the intermetallic compounds obtained are poor, which are not suitable for direct application. Usually, multiple subsequent heat treatment processes are required to improve the structure and mechanical properties, or by adding other metal elements to the mixed powder before the powder metallurgy process, and then performing the powder metallurgy process, to improve the structure and mechanical properties.

[0029] The present application has found through many years of experience that although the intermetallic compound structure is not dense and uniform after sintering by pressing and molding at room temperature using metal element powder as raw material, the intermetallic compound has poor plasticity at room temperature, that is, it has brittleness. The present application utilizes the brittleness of the intermetallic compound obtained by a simple powder metallurgy process of metal element powder, which can be easily crushed into powder, and then the powder is spheroidized to obtain spherical powder of the intermetallic compound. Compared with the traditional method for preparing spherical powder of intermetallic compound in the background technology, the preparation process is shortened, the production cost is reduced, the production process is simple, and the energy consumption is low.

[0030] Figure 1 1 is a flow chart showing the principle of the method for preparing spherical powder of intermetallic compound according to the present invention. In the figure, the flow chart is generally indicated by reference numeral 100, and includes steps 101, 102, 103, 104 and 105. Step 101 is a powder mixing step. In step 101, a plurality of metal element powders that can generate intermetallic compounds are mixed in a desired proportion to obtain a mixed metal element powder. Step 102 is a pressing and forming step. In step 102, the mixed metal element powder is pressed and formed by cold isostatic pressing to obtain a pressed blank. The shape of the pressed blank is preferably set to a shape that is easy to be mechanically crushed into powder, such as a thin sheet. Step 103 is a pressed blank alloying step. In step 103, the pressed blank of the mixed metal element powder is reacted at a certain temperature to synthesize an intermetallic compound blank. Step 104 is a crushing and powdering step. In step 104, the intermetallic compound blank after reaction synthesis is mechanically crushed into powder. Step 105 is a plasma spheroidization step. In step 105, the obtained intermetallic compound powder is spheroidized by plasma to obtain intermetallic compound spherical powder.

[0031] Specifically, in step 104, mechanical crushing into powder includes ball milling, hammering or rolling the intermetallic compound blank into powder, and the process can be protected by a protective gas to prevent metal oxidation. In step 105, the carrier gas sends the powder into the high-temperature plasma, and the high-temperature environment of the thermal plasma is used to quickly heat the mechanically crushed intermetallic compound powder. The powder particles quickly absorb heat and reach the melting point, and the surface or the whole melts. Under the action of surface tension, the molten powder particles condense into spherical droplets. Subsequently, these spherical droplets enter the cooling chamber and solidify into spherical powder particles in a quenched environment, thereby achieving a change in the shape and structure of the mechanically crushed intermetallic compound powder particles. In this way, the mechanically crushed intermetallic compound powders with irregular shapes and sizes are converted into spherical particles with strong fluidity and dense packing.

[0032] After the intermetallic compound blank is crushed into powder, the powder can be screened and graded using a multi-stage screen to obtain an intermetallic compound powder of an appropriate size, and then the intermetallic compound spherical powder can be obtained by plasma spheroidization. It is also possible to directly perform plasma spheroidization after the intermetallic compound blank is crushed into powder, and after obtaining the intermetallic compound spherical powder, the intermetallic compound spherical powder can be screened and graded using a multi-stage screen. The following preferably takes the raw materials as titanium element powder and aluminum element powder, and the raw materials as titanium element powder, aluminum element powder and other metal element powder as examples to describe in detail the preparation method of the intermetallic compound spherical powder of the present invention.

[0033] Figure 2 It is a flow chart of a method for preparing a spherical powder of a titanium-aluminum-based intermetallic compound according to a preferred embodiment of the present invention. In the figure, the flow chart is generally indicated by reference numeral 200, and includes steps 201, 202, 203, 204 and 205. Step 201 is a powder mixing step. In step 201, titanium powder and aluminum powder that can generate titanium-aluminum-based intermetallic compounds, or titanium powder, aluminum powder and other metal element powders are mixed in a desired proportion to obtain a mixed metal powder, and other metal element powders are selected to include one or more of the group consisting of Cr, Nb, Fe, Zr, B, C, W, Mo, Mn, La, Si, Sn, Ni, V, and Ta. Step 202 is a pressing step. In step 202, the mixed metal element powder is pressed by cold isostatic pressing to obtain a pressed blank. Step 203 is a pressed blank alloying step. In step 203, the pressed blank of the mixed metal element powder is reacted at a certain temperature to synthesize a titanium-aluminum-based intermetallic compound blank. Step 204 is a crushing step, in which the titanium-aluminum-based intermetallic compound blank after reaction synthesis is mechanically crushed into powder. Step 205 is a plasma spheroidization step, in which the obtained titanium-aluminum intermetallic compound powder is spheroidized by plasma to obtain titanium-aluminum intermetallic compound spherical powder.

[0034] Similarly, in step 204, mechanical crushing into powder includes ball milling, hammering or rolling the intermetallic compound blank into powder, and a protective gas, such as argon, can be introduced into the process for protection to prevent metal oxidation. After the titanium-aluminum-based intermetallic compound blank is crushed into powder, the powder can be screened and graded using a multi-stage screen to obtain titanium-aluminum-based intermetallic compound powder of appropriate size, and then the titanium-aluminum-based intermetallic compound spherical powder is obtained by plasma spheroidization. It is also possible to directly perform plasma spheroidization after the titanium-aluminum-based intermetallic compound blank is crushed into powder, and after obtaining the titanium-aluminum-based intermetallic compound spherical powder, the titanium-aluminum-based intermetallic compound spherical powder is screened and graded using a multi-stage screen.

[0035] The titanium powder in the raw material can be pure titanium powder or hydrogen-containing titanium powder. When hydrogen-containing titanium powder is used as the raw material, the hydrogen content is 0.1-4%. In the preparation of the commonly used titanium-aluminum-based intermetallic compound spherical powder, the weight percentage of the titanium powder in the raw material is preferably 35wt.%-50wt.%.

[0036] In step 203, the pressed billet of the mixed titanium aluminum metal element powder or the pressed billet of titanium aluminum and other metal element powder is reacted at a certain temperature to synthesize the titanium aluminum-based intermetallic compound blank. The temperature is usually selected to be higher than the melting point of aluminum and lower than the melting point of titanium, so that aluminum can participate in the reaction more completely. The upper limit of the temperature is usually set according to the ratio of titanium powder to aluminum powder and the organizational structure of the desired intermetallic compound spherical powder. The preferred reaction synthesis temperature is 700-1000 degrees Celsius.

[0037] The specific embodiments are as follows:

[0038] Example 1

[0039] A method for preparing spherical powder of titanium-aluminum-based intermetallic compound at low cost, the specific preparation steps are as follows:

[0040] 1. Powder mixing: 84wt% titanium powder (D50=15 microns) and 16wt% aluminum powder (-325 mesh) are placed in a three-dimensional mixer and mixed under argon protection to obtain a mixed powder;

[0041] 2. Pressing and forming: The mixed powder is put into a cold isostatic pressing bag with a forming pressure of 180 MPa, and the mixed powder is pressed into a blank;

[0042] 3. Reaction synthesis of intermetallic compounds: The pressed blank is placed in a vacuum furnace, heated to 900 degrees, with a heating rate of 5 degrees Celsius / min, and kept at high temperature for 180 minutes, and titanium-aluminum-based intermetallic compounds are synthesized by high-temperature reaction;

[0043] 4. Crushing into powder: Mechanically crushing the titanium-aluminum-based intermetallic compound synthesized by the reaction into powder, and sieving, and the mesh number of the sieve is selected to be 220 mesh;

[0044] 5. Plasma spheroidization: The screened titanium-aluminum-based intermetallic compound powder with appropriate mesh size is plasma spheroidized. The spheroidization processing parameters are controlled as follows: gas flow rate is 28L / min, power is 50kw, powder feeding amount is 35g / min, and spherical powder of titanium-aluminum-based intermetallic compound is collected.

[0045] Embodiment 2:

[0046] A method for preparing spherical powder of titanium-aluminum-based intermetallic compound at low cost, the specific preparation steps are as follows:

[0047] 1. Powder mixing: Put 64wt% titanium hydride powder (D50=12 microns) and 36wt% aluminum powder (-325 mesh) into a three-dimensional mixer and mix them under argon protection to obtain a mixed powder;

[0048] 2. Pressing and forming: The mixed powder is put into a cold isostatic pressing bag with a forming pressure of 190 MPa, and the mixed powder is pressed into a blank;

[0049] 3. Reaction synthesis of intermetallic compounds: Put the pressed billet into a vacuum furnace, heat it to 850 degrees, with a heating rate of 4 degrees Celsius / min, and keep it at high temperature for 240 minutes to synthesize titanium-aluminum-based intermetallic compounds by high temperature reaction;

[0050] 4. Crushing into powder: crushing the titanium-aluminum-based intermetallic compound synthesized by the reaction into powder by using a ball mill, and sieving, and selecting the sieve mesh number as 200 mesh;

[0051] 5. Plasma spheroidization: The screened titanium-aluminum-based intermetallic compound powder with appropriate mesh size is plasma spheroidized, and the spheroidization processing parameters are controlled as follows: gas flow rate is 25L / min, power is 45kw, powder feeding amount is 30g / min, and spherical powder of titanium-aluminum-based intermetallic compound is collected.

[0052] Embodiment 3:

[0053] A method for preparing spherical powder of titanium-aluminum-based intermetallic compound at low cost, the specific preparation steps are as follows:

[0054] 1. Powder mixing: 44wt% titanium powder (D50=15 microns), 13wt% aluminum powder (-300 mesh), and 43wt% niobium powder (-325 mesh) are placed in a three-dimensional mixer and mixed under argon protection to obtain a mixed powder;

[0055] 2. Pressing and forming: The mixed powder is put into a cold isostatic pressing bag with a forming pressure of 180 MPa, and the mixed powder is pressed into a blank;

[0056] 3. Reaction synthesis of intermetallic compounds: The pressed blank is placed in a vacuum furnace, heated to 900 degrees, with a heating rate of 5 degrees Celsius / min, and kept at high temperature for 180 minutes, and titanium-aluminum-based intermetallic compounds are synthesized by high-temperature reaction;

[0057] 4. Crushing into powder: crushing the titanium-aluminum-based intermetallic compound synthesized by the reaction into powder using a hammer crusher, and sieving, and the mesh number of the sieve is selected to be 220 mesh;

[0058] 5. Plasma spheroidization: The screened titanium-aluminum-based intermetallic compound powder with appropriate mesh size is plasma spheroidized. The spheroidization processing parameters are controlled as follows: gas flow rate is 30L / min, power is 56kw, powder feeding amount is 25g / min, and titanium-aluminum-niobium spherical powder is obtained after collection.

[0059] In the method for preparing spherical intermetallic compound powder according to the present invention, after obtaining intermetallic compound powder of appropriate mesh size after mechanical crushing (not alloyed and spheroidized by ball milling, usually irregular powder), it is not necessary to use plasma spheroidization process as in the above embodiment, and appropriate heat treatment process or other process can also be used for spheroidization. In the case of obtaining spherical intermetallic compound powder by plasma spheroidization, the gas flow rate is preferably 10-100 L / min, the power is preferably 30-100 kw, and the powder feeding amount is preferably 5-100 g / min.

[0060] Theoretically, the method for preparing spherical intermetallic compound powder of the present invention is applicable to any metal element powder that can form an intermetallic compound. Due to limited space, only Example 4 in which iron element powder and aluminum element powder are used as raw materials to prepare spherical iron-aluminum-based intermetallic compound powder is used as an extended example.

[0061] Example 4

[0062] A method for preparing spherical powder of iron-aluminum-based intermetallic compounds at low cost, the specific preparation steps are as follows:

[0063] 1. Powder mixing: 86wt% iron powder (-200 mesh) and 14wt% aluminum powder (-300 mesh) are placed in a three-dimensional mixer and mixed under nitrogen protection to obtain a mixed powder;

[0064] 2. Pressing and forming: The mixed powder is put into a cold isostatic pressing bag with a forming pressure of 170 MPa, and the mixed powder is pressed into a blank;

[0065] 3. Reaction synthesis of intermetallic compounds: put the pressed billet into a vacuum furnace, heat it to 1000 degrees, with a heating rate of 5°C / min, and keep it at high temperature for 240 minutes, and synthesize iron-aluminum-based intermetallic compounds by high temperature reaction;

[0066] 4. Crushing into powder: crushing the iron-aluminum based intermetallic compound synthesized by the reaction into powder using a hammer crusher, and sieving, and selecting the sieve mesh number of 200 mesh;

[0067] 5. Plasma spheroidization: The screened titanium-aluminum-based intermetallic compound powder with appropriate mesh size is plasma spheroidized. The spheroidization processing parameters are controlled as follows: gas flow rate is 35L / min, power is 56kw, powder feeding amount is 35g / min, and spherical powder of iron-aluminum-based intermetallic compound is obtained after collection.

[0068] Figure 3 is a morphology diagram of titanium-aluminum intermetallic compound spherical powder obtained by the method for preparing intermetallic compound spherical powder of the present invention, Figure 4 yes Figure 3 A partial enlargement of the photograph shown in . Figure 3 and Figure 4 It can be seen that the spherical powder of the titanium-aluminum intermetallic compound obtained by the method of the present invention is mostly spherical, has good sphericity, and has planetary powder, so the fluidity of the obtained powder is also good.

[0069] Therefore, the method for preparing spherical powder of intermetallic compound of the present invention creatively utilizes powder of single metal element as raw material, generates intermetallic compound and then crushes it to form spherical powder, thereby reducing the need for smelting to prepare intermetallic compound rods in the traditional method for preparing spherical powder of intermetallic compound, shortening the preparation process, reducing production cost, simplifying the production process and reducing energy consumption, which is of great significance for developing a low-cost, high-quality method for preparing spherical powder of intermetallic compound.

[0070] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in this application (but not limited to) by each other.

Claims

1. A method for preparing spherical intermetallic compound powder, comprising: (1) Powder mixing: mixing a plurality of metal element powders capable of forming an intermetallic compound in a desired proportion to obtain a mixed metal element powder; (2) Pressing and forming: Pressing the mixed metal element powder by cold isostatic pressing to obtain a pressed blank; (3) Alloying of pressed billets: reacting the pressed billets of mixed metal element powders at a certain temperature to synthesize intermetallic compound billets; (4) Crushing into powder: Mechanically crushing the intermetallic compound blank after reaction synthesis into powder; (5) Plasma spheroidization: The obtained intermetallic compound powder is spheroidized by plasma to obtain spherical intermetallic compound powder.

2. The method for preparing spherical intermetallic compound powder according to claim 1, wherein: Step (4) mechanically crushing the intermetallic compound blank into powder includes ball milling, hammering or rolling the intermetallic compound blank into powder.

3. The method for preparing spherical intermetallic compound powder according to claim 2, wherein: In step (4), after the powder is mechanically crushed, a powder screening step is also included to obtain intermetallic compound powder of appropriate size, and then spherical intermetallic compound powder is obtained by plasma spheroidization.

4. The method for preparing spherical intermetallic compound powder according to claim 2, wherein: After step (5), a powder screening step is further included to obtain spherical intermetallic compound powder of appropriate size.

5. The method for preparing spherical intermetallic compound powder according to any one of claims 1 to 4, wherein: The metal element powder is titanium powder and aluminum powder, or titanium powder, aluminum powder and other metal element powders, and the other metal element powders are selected from one or more of the group including Cr, Nb, Fe, Zr, B, C, W, Mo, Mn, La, Si, Sn, Ni, V, and Ta.

6. The method for preparing spherical intermetallic compound powder according to claim 5, wherein: The titanium powder is pure titanium powder or hydrogen-containing titanium powder, and the hydrogen content is 0.1% to 4%.

7. The method for preparing spherical intermetallic compound powder according to claim 5, wherein: The weight percentage of the titanium powder is 35wt.% to 50wt.%.

8. The method for preparing spherical intermetallic compound powder according to claim 5, wherein: In step (3), the reaction synthesis temperature is 700-1000 degrees Celsius.

9. The method for preparing spherical intermetallic compound powder according to claim 5, wherein: In step (4), high-purity argon gas is used as the protective atmosphere.

10. The method for preparing spherical intermetallic compound powder according to claim 5, wherein: In the case of obtaining spherical intermetallic compound powder by plasma spheroidization, the gas flow rate is 10 to 100 L / min, the power is 30 to 100 kW, and the powder feeding amount is 5 to 100 g / min.

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