CN-117206541-B - Preparation method of metal tungsten porous structure

Abstract

The invention belongs to the technical field of additive manufacturing, and particularly provides a preparation method of a metal tungsten porous structure. The method takes high-purity micron-sized tungsten powder prepared by a hydrogen reduction method as a raw material, obtains powder with uniform nearly spherical particle size distribution through air flow mill grading treatment, adopts epoxy resin binder to spray and form the powder into green bodies, and adopts a sectional sintering method to sinter after thermal degreasing, so as to obtain the metal tungsten porous structure with uniform and fine pores, wherein the porosity of the metal tungsten porous structure is 10-50%, and the pore diameter is less than 1 mu m. The invention adopts the binder to spray and form the porous structure for preparing tungsten, and has the advantages of low cost, high speed, no need of support, difficult cracking and the like. The invention provides a new idea for preparing the porous tungsten complex part.

Inventors

• LIU JUNMING
• ZHANG LIN
• LI XINGYU
• ZHANG PENG
• NAN YANGRUI
• YANG QILONG
• Huang Xinduo
• ZHAO JINYAN
• ZHAO XIN

Assignees

• 北京科技大学
• 北京恒创增材制造技术研究院有限公司

Dates

Publication Date

20260508

Application Date

20230807

Claims (5)

1. 1. The preparation method of the metal tungsten porous structure is characterized in that micron-sized tungsten powder prepared by a hydrogen reduction method is used as a raw material, nearly spherical powder with uniform particle size distribution is obtained through air flow grinding classification treatment, the nearly spherical powder is prepared into a green body by adopting a binder spray forming technology, and after thermal degreasing, the green body is sintered by adopting a sectional sintering method, so that the metal tungsten porous structure with uniform and fine pores is obtained; the preparation method specifically comprises the following steps: S1) carrying out jet milling treatment on tungsten powder obtained by hydrogen reduction to obtain nearly spherical powder; The Fisher particle size of the micron-sized tungsten powder is 1-10 mu m, and the purity is over 99.9 percent; S2) preparing an epoxy resin binder; The mass fraction of the adhesive in the epoxy resin adhesive is 10-30%, the mass fraction of the curing agent is 4-8%, the mass fraction of the toughening agent is 0.5-3%, and the rest is solvent, wherein the viscosity of the adhesive is 3-15cps; The adhesive is epoxy resin, the curing agent is m-phenylenediamine or imidazole curing agent, the toughening agent is polyamide resin, and the solvent is dimethylformamide or butyl glycidyl ether; S3) adding the nearly spherical powder obtained in the step S1) and the epoxy resin binder obtained in the step S2) into equipment, setting parameters of powder spreading, ink spraying and printing, performing powder spreading and bonding forming, moving a powder bed containing parts to an oven for heating and curing after printing, and cleaning powder around the parts after curing to obtain a green body; The printing parameters are that the powder spreading layer thickness is 0.05-0.2mm, the powder spreading speed is 15-120mm/s, the printing speed is 100-400mm/s, the saturation of the adhesive is 50-80%, the curing temperature is 150-200 ℃, and the heat preservation time is 1-3h; s4) removing the binder by adopting a thermal degreasing mode, and sintering by adopting a sectional sintering method under a protective atmosphere to obtain the metal tungsten porous structure with the porosity of 10-50%, the pore diameter of less than 1 mu m and the pore diameter variance of less than 0.2.
2. 2. The preparation method according to claim 1, wherein the specific steps of S1) are: s1.1), firstly, opening an air flow mill, filling nitrogen with the purity of more than 99.9% as a grinding medium, adjusting the grinding pressure to 0.5-0.7MPa, and adding tungsten powder; S1.2) setting the frequency of a sorting wheel to 150HZ according to the particle size requirement of the powder, dispersing the powder, then sequentially reducing the frequency of the sorting wheel to 100HZ, 70HZ and 20HZ, and processing for 2-4h, wherein the powder with the middle particle size in the processed powder is selected as the powder for printing.
3. 3. The preparation method according to claim 1, wherein the specific steps of S4) are: S4.1) a thermal degreasing process, namely heating from room temperature to 300 ℃ at a heating rate of 1-3 ℃ per minute, preserving heat for 1h, continuously heating to 600-700 ℃, and preserving heat for 1-2h; s4.2) under the protection atmosphere, heating to the temperature of T 1 , performing low-temperature sintering, and preserving heat; S4.3) the sintering temperature is increased to T 2 , and the heat is preserved, so that compact sintering is completed.
4. 4. The method according to claim 3, wherein the temperature rise rate in S4.2) is 1-3 ℃ per minute, the value of T 1 is 600-700 ℃, and the incubation time is 1-2 hours; S4.3) the value of T 2 is 1400-2000 ℃, and the temperature is kept for 1-3h.
5. 5. A method of preparing according to claim 3, wherein the protective atmosphere is hydrogen.

Description

Preparation method of metal tungsten porous structure Technical Field The invention belongs to the technical field of additive manufacturing, and particularly provides a preparation method of a metal tungsten porous structure. Background Tungsten is used as refractory metal with highest melting point, has the characteristics of excellent high-temperature performance, low vapor pressure, corrosion resistance and the like, is widely applied to the fields of national defense and military industry, aerospace, energy industry, electronic information industry and the like, and plays an important role in national economy. The method has important application in the industrial field and the nuclear power field, tungsten shows good application prospect of high-temperature materials in nuclear fusion reactors, for example, a porous cathode with high current density is one of important application of porous tungsten, and the diffusion cathode which is most used at present is prepared by taking porous tungsten as a matrix and dipping aluminate of barium metal on the porous tungsten matrix. The pores in the porous tungsten are used as a storage emission substance, a transmission channel for the emission substance is provided, certain requirements are provided for the size, the shape and the uniform distribution of the pores and the open pore porosity, and the characteristics of the pores have important influences on the storage, the activation and the transmission of the substances of the tungsten matrix, so that the preparation of the high-quality porous tungsten matrix is a key technology for realizing the uniform emission of cathode electrons. For the preparation method of porous tungsten, the powder sintering method is mostly adopted in the prior art, namely, a pore-forming agent is added into tungsten powder, and then the porous structure is obtained by pressing and sintering, but the preparation method is difficult to control the uniformity of pores, and complicated parts can be obtained by machining, and the complicated components of the porous tungsten and the difficulties of the complicated components are prepared by the traditional machining method due to the high hardness and high brittleness of tungsten. The 3D printing is used as an emerging manufacturing technology at present, can directly form complex parts, has obvious advantages in small-batch and customized production, and is mainly used for laser forming, electron beam forming and adhesive injection forming, and the use of the metal 3D printing technology is limited because the tungsten has high melting point and high brittleness, and serious deformation and cracking are easily caused in the melting and solidification process by using laser or electron beam to form tungsten. The binder spray forming is used as an indirect 3D printing technology, green bricks are obtained by laying powder layer by layer and bonding at normal temperature, and then the required products are obtained by degreasing and sintering, so that the prepared samples have uniform structure performance, the problems of anisotropy, cracking and the like are avoided, and the process is particularly suitable for preparing refractory metal porous structures. Disclosure of Invention The invention discloses a preparation method of a metal tungsten porous structure, which solves the technical problems and other technical problems in the prior art. In order to solve the technical problems, the technical scheme is that the preparation method of the metal tungsten porous structure is characterized in that high-purity micron-sized tungsten powder is prepared by a hydrogen reduction method and is used as a raw material, powder with uniform nearly spherical particle size distribution is obtained through air flow grinding classification treatment, the powder is made into green bodies through spray forming of an epoxy resin binder, and the green bodies are sintered through a sectional sintering method after thermal degreasing, so that the metal tungsten porous structure with uniform and fine pores is obtained. Further, the preparation method specifically comprises the following steps: s1) carrying out air flow grinding treatment on tungsten powder obtained by hydrogen reduction, setting the frequency of an air flow mill, filling nitrogen as a grinding medium, and grading under a certain grinding pressure to obtain nearly spherical powder with narrow particle size distribution and good fluidity; s2) respectively weighing the adhesive, the solvent, the curing agent and the toughening agent according to a certain proportion, uniformly mixing, stirring and filtering to obtain the epoxy resin adhesive; s3) setting parameters of powder spreading, ink spraying and printing, performing powder spreading and bonding forming, moving a powder bed containing the parts to an oven for heating and curing after printing is finished, and cleaning powder around the parts after curing is finished to obtain a green bo