Preparation method of high-rhenium low-oxygen spherical tungsten-rhenium alloy powder

Abstract

The invention discloses a preparation method of high-rhenium and low-oxygen spherical tungsten-rhenium alloy powder, which comprises the following steps: proportioning tungsten powder and rhenium powder, adding into a ball mill for ball milling and mixing to obtain uniform composite powder slurry; the composite powder slurry is fed into a spray dryer to be subjected to spray granulation to form sphere-like alloy powder; and the spheroidized powder is subjected to plasma spheroidizing treatment to form the spherical tungsten-rhenium alloy powder. According to the preparation method disclosed by the invention, the tungsten-rhenium suspension slurry with uniformly dispersed components is prepared, and then granulation and spheroidization are carried out, so that the uniform state of the suspension is successfully solidified, oxygen can be reduced, impurities can be removed, and the spherical alloy powder with relatively large granularity and unlimited rhenium adding amount is prepared. The technical route flow is short, the process controllability is high, pilot scale production can be achieved, and the prepared tungsten-rhenium alloy spherical powder is high in density, sphericity degree and uniformity and low in oxygen content.

Description

Technical Field

[0001] The invention relates to the technical field of tungsten-rhenium powder preparation, and in particular to a method for preparing a spherical tungsten-rhenium alloy powder with high rhenium and low oxygen. Background Art

[0002] The strategic rare and precious metal rhenium has become the focus of attention in the industry due to its excellent hardness, mechanical strength, wear and corrosion resistance, and chemical stability. Its characteristic of having no ductile-brittle transition temperature enables rhenium doping in tungsten and molybdenum to induce a significant "rhenium effect", thereby greatly improving the plasticity, high-temperature tensile strength, and high-temperature creep resistance of rhenium alloys.

[0003] At present, tungsten-rhenium alloy can be used to prepare key components such as high-temperature thermocouples, aviation electromagnetic electromechanical contacts, nuclear fuel storage and controllers, and diffusion walls of high-temperature heat release elements. However, the above fields have extremely high requirements for the uniformity, rhenium content and oxygen content of rhenium in the tungsten-rhenium alloy structure, which places extremely high requirements on the above indicators and formability of the tungsten-rhenium alloy powder raw materials. Ammonium tungstate and ammonium rhenate ammonium salt compounds are used as precursors, dissolved and mixed, and then calcined and reduced to prepare tungsten-rhenium pre-alloyed powder raw materials with good uniformity. However, the disadvantage is that the tungsten-rhenium alloy powder obtained by this method has a fine particle size, often at the micro-nano level, and has extremely poor fluidity, and the amount of rhenium added is also limited. The traditional high-energy ball milling method can also prepare tungsten-rhenium pre-alloyed powder. Its advantages are that it can be mass-produced, the powder particle size is controllable, and conventional particle size alloy powder can be prepared, and the amount of rhenium added is not limited. However, the disadvantage is that the uniformity of rhenium cannot be guaranteed, and the process requirements for ball milling are extremely strict. Summary of the invention

[0004] The invention discloses a method for preparing a spherical tungsten-rhenium alloy powder with high rhenium and low oxygen, so as to solve any of the above and other potential problems in the prior art.

[0005] In order to solve the above technical problems, the technical solution of the present invention is: a method for preparing a spherical tungsten-rhenium alloy powder with high rhenium and low oxygen, the preparation method specifically comprising the following steps:

[0006] S1) Weighing tungsten powder and rhenium powder according to the designed ratio, adding them into a ball mill and mixing them to obtain a uniform composite powder slurry;

[0007] S2) feeding the composite powder slurry obtained in S1) into a spray dryer for spray granulation into quasi-spherical alloy powder;

[0008] S3) subjecting the quasi-spherical powder obtained in S2) to plasma spheroidization to obtain spherical tungsten-rhenium alloy powder.

[0009] Furthermore, the mass percentages of the tungsten powder and the rhenium powder in S1) are: 50wt%≤W<90wt%, 10<Re≤50wt%.

[0010] Furthermore, the ball milling conditions described in S1) are: rotation speed 150-350 r / min; each ball milling time 25-35 min, downtime 15-20 min; ball milling medium is 10-35% anhydrous ethanol; ball milling time is 2-4 h.

[0011] Furthermore, the materials in the grinding balls have diameters of 8 mm, 5 mm, and 3 mm and are mixed in a mass ratio of 1:2:(1.5-2).

[0012] Furthermore, the spray granulation conditions in S2) are: adding a certain amount of adhesive, the inlet temperature is 170-200°C; the outlet temperature is 50-70°C; and the rotation speed frequency is 70-200Hz.

[0013] Furthermore, the oxygen content of the spray granulation cavity in S2) is ≤2.5%; the oxygen-removing medium is nitrogen with a purity of ≥99.99%.

[0014] Furthermore, the added amount of the adhesive is 1%-5%; the adhesive is polyvinyl alcohol or polyethylene glycol.

[0015] Further, the plasma spheroidization treatment conditions in S3) are: the flow rate of the powder is 10-20g / min; the speed of the powder feeder is 10-15rpm; the plasma power is 30-40Kw; the powder feeding gap is 0.3-0.6mm, and the working atmosphere is a rare gas.

[0016] Furthermore, the particle size of the tungsten powder is less than 10 μm, and the powder purity is ≥99.5%; the particle size of the rhenium powder is ≤10 μm, and the powder purity is ≥99.5%.

[0017] Furthermore, the oxygen content of the spherical tungsten-rhenium alloy powder is not higher than 0.054%; the rhenium content fluctuation of a single particle is less than ±10%, the density is high and there are no hollow balls, and the sphericity is ≥95%.

[0018] The beneficial effects of the present invention are:

[0019] (1) The present invention can prepare spherical tungsten-rhenium alloy powder with high rhenium content and unlimited rhenium addition amount: by designing the amount of binder, tungsten and rhenium can be effectively prepared into a suspension of any proportion. Since rhenium is introduced in the form of a single substance powder, it will not be affected by the low solubility when introduced in the form of ammonium rhenate and the restriction on the addition amount, and the component customization capability is extremely strong.

[0020] (2) The present invention can prepare spherical tungsten-rhenium alloy powder with extremely low oxygen content: by controlling the medium of the ball milling process, the oxygen content of the entire spray drying process, and the introduction of a reducing atmosphere during the plasma spheroidization process, the oxygen content of the powder product is greatly reduced, thereby improving its performance as a raw material for preparing molded parts.

[0021] (3) The spherical tungsten-rhenium alloy powder prepared by the present invention has good rhenium uniformity, high density and sphericity, competitive product quality, and wide application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the morphology of the spray-granulated spherical alloy powder in the preparation method of the present invention.

[0023] Figure 2 Schematic diagram of the physical phase of spherical tungsten-rhenium alloy powder prepared by Example 2 of the preparation method of the present invention.

[0024] Figure 3 Laser particle size distribution diagram of spherical tungsten-rhenium alloy powder prepared by Example 3 of the preparation method of the present invention.

[0025] Figure 4 FESEM morphology of spherical tungsten-rhenium alloy powder with high rhenium content prepared by Example 4 of the preparation method of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with specific embodiments.

[0027] This application creatively prepares a tungsten-rhenium suspension slurry with uniformly dispersed components, and then solidifies the uniform state of the suspension through granulation and spheroidization, and at the same time can reduce oxygen and remove impurities, and prepares spherical alloy powder with relatively large particle size and unlimited rhenium addition. This technical route has a short process, strong process controllability, and can be pilot-produced. The prepared tungsten-rhenium alloy spherical powder has high density, sphericity and uniformity, and low oxygen content.

[0028] The present invention discloses a method for preparing a spherical tungsten-rhenium alloy powder with high rhenium and low oxygen, and the preparation method specifically comprises the following steps:

[0029] S1) After the tungsten powder and the rhenium powder are mixed in a certain proportion, the mixture is added into a ball mill and ball milled to obtain a uniform composite powder slurry;

[0030] S2) the obtained composite powder slurry is sent into a spray dryer for spray granulation into spherical alloy powder;

[0031] S3) The quasi-spherical powder obtained is subjected to plasma spheroidization treatment to form spherical tungsten-rhenium alloy powder.

[0032] The ball milling conditions in S1) are as follows: rotation speed 150-350 r / min; each ball milling time 25-35 min, stop time 15-20 min; grinding balls with diameters of 8 mm, 5 mm, and 3 mm are mixed in a mass ratio of 1:2:(1.5-2); the ball milling medium is 10-35% anhydrous ethanol; and the ball milling time is 2-4 h.

[0033] The spray granulation conditions in S2) are: the tower inlet temperature is 170-200°C; the tower outlet temperature is 50-70°C; and the rotation speed frequency is 70-200 Hz.

[0034] The oxygen content of the spray granulation cavity in S2) is ≤2.5%; the oxygen-removing medium is nitrogen with a purity of ≥99.99%.

[0035] In the spray granulation in S2), a binder (polyvinyl alcohol or polyethylene glycol) needs to be added in an amount of 1%-5%.

[0036] The plasma spheroidization treatment conditions in S3) are: the flow rate of the powder is 10-20g / min; the speed of the powder feeder is 10-15rpm; the plasma power is 30-40Kw; the powder feeding gap is 0.3-0.6mm, and the working atmosphere is a rare gas.

[0037] Embodiment 1:

[0038] A spherical powder, with 89wt% W and 11wt% Re by mass percentage, tungsten powder particle size ≤5μm, powder purity 99.5%, rhenium powder particle size ≤10μm, powder purity 99.5%. The preparation method is as follows: Step 1, first mix tungsten powder and rhenium powder, add them to a ball mill and mix them to obtain a uniform composite powder slurry, the ball milling conditions are: speed 350r / min; each ball milling 25min, stop 20min; grinding ball diameters of 8mm, 5mm, and 3mm are mixed in a mass ratio of 1:2:1.5; the ball milling medium is 35% anhydrous ethanol; the ball milling time is 4h; Step 2, send the above slurry into a spray dryer for spray granulation into a quasi-spherical alloy powder, the spray granulation conditions are:

[0039] The inlet temperature is 190°C; the outlet temperature is 60°C; the frequency of the rotation speed is 150Hz; the oxygen content of the spray granulation cavity is 2.1%; the oxygen-driving medium is nitrogen with a purity of 99.999%; 5% polyvinyl alcohol is added to the spray granulation; step three, the quasi-spherical alloy powder is plasma spheroidized into spherical tungsten-rhenium alloy powder. The plasma spheroidization treatment conditions are: the flow rate of the powder is 20g / min; the speed of the powder feeder is 10rpm; the plasma power is 30Kw; the powder feeding gap is 0.3mm, the working atmosphere is a rare gas, the rhenium content of a single particle fluctuates <±10%, the density is high and there are no hollow balls, and the sphericity is ≥95%.

[0040] Embodiment 2:

[0041] A spherical powder comprises 75wt% of W and 25wt% of Re by mass percentage, the particle size of the tungsten powder is ≤3μm, the powder purity is 99.5%, and the particle size of the rhenium powder is ≤5μm, and the powder purity is 99.9%. The preparation method is as follows: step 1, first mix tungsten powder and rhenium powder, add them into a ball mill and mix them to obtain a uniform composite powder slurry, and the ball milling conditions are: rotation speed 250r / min; each ball milling 30min, stop 20min; the grinding ball diameters are 8mm, 5mm, and 3mm, and they are mixed in a mass ratio of 1:2:2; the ball milling medium is 25% anhydrous ethanol; the ball milling time is 3h; step 2, the above slurry is sent to a spray dryer for spray granulation into a quasi-spherical alloy powder, and the spray granulation conditions are: the tower inlet temperature is 200°C; the tower outlet temperature is 75°C; the rotation speed frequency is 120Hz; the oxygen content of the spray granulation cavity is 1.8%; the oxygen-driving medium is nitrogen with a purity of 99.999%; 4% polyethylene glycol is added during spray granulation; step 3, the above quasi-spherical alloy powder is plasma spheroidized to form a spherical tungsten-rhenium alloy powder. The plasma spheroidization treatment conditions are: the powder flow rate is 18g / min; the powder feeder speed is 15rpm; the plasma power is 37Kw; the powder feeding gap is 0.6mm, the working atmosphere is rare gas, the rhenium content of a single particle fluctuates <±10%, the density is high and there are no hollow balls, and the sphericity is ≥95%.

[0042] Embodiment 3:

[0043] A spherical powder comprises 60wt% of W and 40wt% of Re by mass percentage, the particle size of the tungsten powder is ≤2μm, the powder purity is 99.99%, and the particle size of the rhenium powder is ≤4μm, and the powder purity is 99.99%. The preparation method is as follows: step 1, first mix tungsten powder and rhenium powder, add them into a ball mill and mix them to obtain a uniform composite powder slurry, and the ball milling conditions are: rotation speed 200r / min; each ball milling for 35min, stop for 20min; the grinding ball diameters are 8mm, 5mm, and 3mm, and they are mixed in a mass ratio of 1:2:2; the ball milling medium is 20% anhydrous ethanol; the ball milling time is 4h; step 2, the above slurry is sent to a spray dryer for spray granulation into a quasi-spherical alloy powder, and the spray granulation conditions are: the tower inlet temperature is 180°C; the tower outlet temperature is 55°C; the rotation speed frequency is 90Hz; the oxygen content of the spray granulation cavity is 2.5%; the oxygen-dripping medium is nitrogen with a purity of 99.999%; 4% polyethylene glycol is added during spray granulation; step 3, the above quasi-spherical alloy powder is plasma spheroidized to form a spherical tungsten-rhenium alloy powder. The plasma spheroidization treatment conditions are: the flow rate of the powder is 14g / min; the speed of the powder feeder is 13rpm; the plasma power is 40Kw; the powder feeding gap is 0.5mm, the working atmosphere is rare gas, the rhenium content of a single particle fluctuates <±10%, the density is high and there are no hollow balls, and the sphericity is ≥95%.

[0044] Embodiment 4:

[0045] A spherical powder comprises 51wt% W and 49wt% Re by mass percentage, the particle size of the tungsten powder is ≤2μm, the powder purity is 99.99%, and the particle size of the rhenium powder is ≤5μm, and the powder purity is 99.99%. The preparation method is as follows: step 1, first mix tungsten powder and rhenium powder, add them into a ball mill and mix them to obtain a uniform composite powder slurry, and the ball milling conditions are: rotation speed 350r / min; each ball milling 30min, stop 20min; the grinding ball diameters are 8mm, 5mm, and 3mm, and they are mixed in a mass ratio of 1:2:1.5; the ball milling medium is 20% anhydrous ethanol; the ball milling time is 2h; step 2, the above slurry is sent to a spray dryer for spray granulation into a quasi-spherical alloy powder, and the spray granulation conditions are: the tower inlet temperature is 170°C; the tower outlet temperature is 50°C; the rotation speed frequency is 70Hz; the oxygen content of the spray granulation cavity is 1.7%; the oxygen-dripping medium is nitrogen with a purity of 99.999%; 3% polyethylene glycol is added during spray granulation; step 3, the above quasi-spherical alloy powder is plasma spheroidized to form a spherical tungsten-rhenium alloy powder. The plasma spheroidization treatment conditions are: the powder flow rate is 15g / min; the powder feeder speed is 10rpm; the plasma power is 39Kw; the powder feeding gap is 0.3mm, the working atmosphere is rare gas, the rhenium content of a single particle fluctuates <±10%, the density is high and there are no hollow balls, and the sphericity is ≥95%.

[0046] Test example:

[0047] 1. Phase test: In this experiment, a Philips X-Pert Pro X-ray diffractometer was used to analyze the phase composition of the prepared rhenium powder. The measurement angle range was 10°-90°, and the step length was 0.02 (°) / s; Cu Kα target material.

[0048] 2. Determination of oxygen content of powder: In this test, the oxygen content of the powder was tested using the oxygen, nitrogen and hydrogen analyzer of Gangyan Nano-K, with random sampling and 3 tests.

[0049] 3. Powder particle size determination: This test uses a laser particle size distribution analyzer to test the powder particle size of the powder obtained in the preparation process. The test method is a wet method.

[0050] 4. Powder morphology characterization: In this experiment, the field emission scanning electron microscope of JEOL was used to observe the microscopic morphology of granulated powder and spherical powder of tungsten-rhenium alloy.

[0051] First, from Figure 1It can be seen that the SEM morphology of the powder obtained after step 2 (S2) using the preparation method (Examples 1-4) of the present application shows that the uniformly mixed tungsten-rhenium mixed suspension powder is solidified after spray drying and granulation, retaining the uniformity of the liquid phase, and the ultrafine tungsten powder and rhenium powder of less than 10 μm added in Examples 1-4 can be agglomerated into large particle powders as shown in the figure ( Figure 1 The average particle size of the alloy powder shown is about 50 μm, and the specific size evolves accordingly according to the spray drying process). Therefore, the uniformity and particle size customization of the tungsten-rhenium alloy powder prepared by the present invention are extremely high.

[0052] Table 1 is a statistical table of composition tests of spherical tungsten-rhenium alloy powders prepared in Examples 1-4: from Figure 2 It can be seen that the spherical tungsten-rhenium alloy powder prepared in Example 2 is mainly composed of tungsten, rhenium and tungsten-rhenium alloy, which means that the powder has no obvious impurity phase, and the main phase is tungsten, and tungsten and rhenium have formed a part of alloy phase structures such as WRe and W3Re during the high temperature process of plasma spheroidization. This fully shows that the tungsten-rhenium spherical powder prepared in this application is an alloy powder without impurity phase.

[0055] from Figure 3 It can be found that the laser particle size distribution diagram of rhenium powder is unimodal, and the average particle size (D50) is 57.8μm, which confirms that the particles of the prepared rhenium powder are evenly distributed and of medium size, and are suitable for back-end forming applications such as 3D printing, plasma cladding and hot isostatic pressing.

[0056] from Figure 4 The SEM image of the spherical tungsten-rhenium alloy powder with a weight of 49 wt.% prepared in Example 4 shows that the powder has a very high sphericity (greater than 95%), no satellite balls, and a smooth surface. This indicates that after the granulated powder is spheroidized by plasma, the tungsten-rhenium alloy powder is partially or completely alloyed (a fine grain structure has been formed on the surface of the spheroidized particles).

[0057] The above is a detailed introduction to the preparation method of a high-rhenium, low-oxygen spherical tungsten-rhenium alloy powder provided in the embodiment of the present application. The description of the above embodiment is only used to help understand the method and its core idea of ​​the present application; at the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present application.

[0058] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" and "comprising" are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be determined by the definition of the attached claims.

[0059] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0060] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0061] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims

1. A method for preparing a spherical tungsten-rhenium alloy powder with high rhenium and low oxygen, characterized in that: The preparation method specifically comprises the following steps: S1) Weighing tungsten powder and rhenium powder according to the designed ratio, adding them into a ball mill and mixing them to obtain a uniform composite powder slurry; S2) feeding the composite powder slurry obtained in S1) into a spray dryer for spray granulation into quasi-spherical alloy powder; S3) subjecting the quasi-spherical powder obtained in S2) to plasma spheroidization to obtain spherical tungsten-rhenium alloy powder.

2. The preparation method according to claim 1, characterized in that: The mass percentages of the tungsten powder and the rhenium powder in S1) are: 50wt%≤W<90wt%, 10<Re≤50wt%.

3. The preparation method according to claim 1, characterized in that: The ball milling conditions described in S1) are: rotation speed 150-350 r / min; each ball milling time 25-35 min, stop time 15-20 min; ball milling medium is 10-35% anhydrous ethanol; ball milling time is 2-4 h.

4. The preparation method according to claim 3, characterized in that: The materials in the grinding balls have diameters of 8 mm, 5 mm, and 3 mm and are mixed in a mass ratio of 1:2:(1.5-2).

5. The preparation method according to claim 1, characterized in that: The spray granulation conditions in S2) are: adding a certain amount of adhesive, the inlet temperature is 170-200°C; the outlet temperature is 50-70°C; and the rotation speed frequency is 70-200Hz.

6. The preparation method according to claim 1, characterized in that: The oxygen content of the spray granulation cavity in S2) is ≤2.5%; the oxygen-removing medium is nitrogen with a purity of ≥99.99%.

7. The preparation method according to claim 5, characterized in that: The added amount of the adhesive is 1%-5%; the adhesive is polyvinyl alcohol or polyethylene glycol.

8. The preparation method according to claim 1, characterized in that: The plasma spheroidization treatment conditions in S3) are: the flow rate of the powder is 10-20g / min; the speed of the powder feeder is 10-15rpm; the plasma power is 30-40Kw; the powder feeding gap is 0.3-0.6mm, and the working atmosphere is a rare gas.

9. The preparation method according to claim 1, characterized in that: The particle size of the tungsten powder is less than 10 μm, and the powder purity is ≥ 99.5%; the particle size of the rhenium powder is ≤ 10 μm, and the powder purity is ≥ 99.5%.

10. The preparation method according to claim 1, characterized in that: The oxygen content of the spherical tungsten-rhenium alloy powder is not higher than 0.054%; the rhenium content fluctuation of a single particle is less than ±10%, the density is high and there is no hollow ball, and the sphericity is ≥95%.

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