阅读说明：本技术 一种选区激光熔化制备具有复杂结构的纯钨构件的方法 (Method for preparing pure tungsten component with complex structure by selective laser melting ) 是由 陈超 董静 李丹 苏超 陈慧 周科朝 于 2019-11-22 设计创作，主要内容包括：本发明涉及一种选区激光熔化制备具有复杂结构的纯钨构件的方法,属于金属材料增材制造技术领域。本发明通过在纯钨粉末中添加适量的碳元素,结合适当条件参数的选区激光熔化,得到了致密度高、力学性能优异的产品。本发明经优化后的方案:等离子球化渗碳技术+选区激光熔化技术；其所得产品的性能远远高于其他技术所得产品。(The invention relates to a method for preparing a pure tungsten component with a complex structure by selective laser melting, belonging to the technical field of metal material additive manufacturing. According to the invention, a proper amount of carbon element is added into pure tungsten powder, and selective laser melting with proper condition parameters is combined, so that a product with high density and excellent mechanical properties is obtained. The optimized scheme of the invention is that a plasma spheroidizing carburizing technology and a selective laser melting technology are adopted; the performance of the obtained product is far higher than that of the products obtained by other technologies.)

1. A method for preparing a pure tungsten component with a complex structure by selective laser melting is characterized in that; the method comprises the following steps:

step one

Selecting pure tungsten powder as original powder to prepare W/C composite powder; in the W/C composite powder, the content of C is 0.1-0.5 wt%, preferably 0.25-0.35%;

step two

Constructing a part model to be prepared by using three-dimensional software, and guiding the constructed model into selective laser melting molding equipment;

step three

Placing the prepared composite powder into a powder supply cylinder in selective laser melting equipment, and introducing protective gas into a forming cavity for atmosphere protection;

step four

Setting technological parameters of the selective laser melting processing process, and performing laser sintering on the prepared powder;

step five

And carrying out linear cutting and ultrasonic cleaning on the printed part to obtain the tungsten part.

2. The selective laser melting method for preparing the pure tungsten component with the complex structure according to claim 1, wherein the selective laser melting method comprises the following steps: the particle size range of the pure tungsten powder is 10-35 mu m.

3. The selective laser melting method for preparing the pure tungsten component with the complex structure according to claim 2, wherein the selective laser melting method comprises the following steps: the pure tungsten powder had a D50 of 22.5 μm.

4. The selective laser melting method for preparing the pure tungsten component with the complex structure according to claim 1, wherein the selective laser melting method comprises the following steps: the three-dimensional software includes Magics.

5. The selective laser melting method for preparing the pure tungsten component with the complex structure according to claim 1, wherein the selective laser melting method comprises the following steps: the W/C composite powder was prepared by the following 2 methods:

the method comprises the following steps: ball milling mixed powder

Taking tungsten powder and graphite powder as raw materials, wherein the particle size range of the graphite powder is 1-8 mu m, the D50 is 3 mu m, and the mass percentage of the tungsten powder is as follows: graphite powder 99.7: 0.3, weighing tungsten powder and graphite powder, and putting the tungsten powder and the graphite powder into a ball milling tank containing stainless steel balls, wherein the mass ratio of the ball materials is 2: 1, ball milling is carried out in a ball mill for 12 hours at the rotating speed of 50rpm by taking argon as a protective atmosphere. Sieving the powder subjected to ball milling, and then putting the powder into a vacuum drying oven for drying to obtain W/C composite powder for later use;

the method 2 comprises the following steps: plasma spheroidizing carburizing

Carburizing in a spheroidizing process is adopted for the original pure tungsten powder; the spheroidization of the tungsten powder is carried out in a reaction containing carbon in Ar₂Adding CH₄As carbonizing agent, by Ar₂-CH₄The mixed carrier gas feeds the powder particles into a plasma zone where they are melted to form a liquid, CH₄Cracking at high temperature to generate activated carbon atoms, absorbing the activated carbon atoms by molten liquid particles, solidifying the molten particles into spherical shapes under the action of centrifugal force and surface tension in subsequent cooling, and collecting the spheroidized powder particles by a collection bin below an instrument; and then, sieving the spheroidized powder, and then putting the spheroidized powder into a vacuum drying oven for drying to obtain W/C composite powder for later use.

6. The selective laser melting method for preparing the pure tungsten component with the complex structure according to claim 1, wherein the selective laser melting method comprises the following steps: in the third step, the protective atmosphere is argon atmosphere, and the oxygen content in the forming cavity is less than 0.1 percent when the selective laser melting is carried out.

7. The selective laser melting method for preparing the pure tungsten component with the complex structure according to claim 1, wherein the selective laser melting method comprises the following steps: the substrate heating temperature is set to 100 ℃ to 180 ℃, preferably 175 ℃ to 180 ℃.

8. The selective laser melting method for preparing the pure tungsten component with the complex structure according to claim 1, wherein the selective laser melting method comprises the following steps: when selective laser melting is carried out, the diameter of a laser spot is controlled to be 90-130 mu m, preferably 130 mu m, the laser power is controlled to be 400-475W, the laser scanning speed is 400-600 mm/s, the laser scanning interval is 40-80 mu m, and the powder spreading thickness is 20-40 mu m.

9. The selective laser melting method for preparing a pure tungsten member with a complex structure according to any one of claims 1 to 8, wherein: the density of the obtained member is more than or equal to 98.5 percent, and the compressive strength is more than or equal to 1280 MPa.

10. The selective laser melting method for preparing the pure tungsten component with the complex structure according to claim 9, wherein the selective laser melting method comprises the following steps: the density of the obtained member is 99.2-99.5%, and the compressive strength is 1420-1430 MPa.

Technical Field

The invention relates to a method for preparing a pure tungsten component with a complex structure by selective laser melting, belonging to the technical field of metal material additive manufacturing.

Background

Tungsten (W), which is a refractory metal having the highest melting point (3410 ℃), has unique physicochemical properties such as high density, good thermal conductivity, high recrystallization temperature, low thermal expansion coefficient, high strength at room temperature, and high hardness. It finds wide application in the manufacture of military weapons, medical devices, aerospace and nuclear applications. Particularly, in nuclear fusion devices such as an international thermonuclear experimental reactor and a high-performance rocket nozzle, tungsten is considered as the most promising plasma surface material due to excellent heat resistance and plasma radiation performance. Despite these advantages, tungsten has one major drawback, namely its high ductile-brittle transition temperature (DBBT), typically between 200 and 400 ℃, resulting in low room temperature plasticity. The high melting point and low room temperature ductility of tungsten increase the difficulty of processing and manufacturing, limiting the application of tungsten as a structural material. Therefore, tungsten articles are typically manufactured using Powder Metallurgy (PM), Spark Plasma Sintering (SPS), Chemical Vapor Deposition (CVD), and Hot Isostatic Pressing (HIP).

In recent years, with the continuous development of science and technology, the application field of pure tungsten is continuously expanded, and the requirements on formed parts are higher and higher. In the application of nuclear fusion devices such as armor piercing bullets, automobile turbine engines, rocket nozzles and the like, the required tungsten parts are more complex in shape and usually have complex structures such as inner holes, grooves, multi-section and the like. This requires the development of freedom in designing the tungsten parts into three-dimensional shapes. The traditional forming method has the limitations in manufacturing parts with complex structures, and is long in time consumption and high in cost. Therefore, the additive manufacturing technology which can rapidly and custom prepare the complex parts is widely concerned.

Selective Laser Melting (SLM) is a method in the field of additive manufacturing technology that can selectively melt powder layer by layer using a Laser beam generated by a Laser according to a three-dimensional CAD model to produce single or multiple metal parts with complex geometries without the need for part-specific molds. The SLM technology has the characteristics of short part development period, high machining precision, raw material saving, capability of forming any complex part and the like. Currently, this technique has been used to form a variety of metals such as titanium alloys, stainless steels, aluminum alloys, nickel-base superalloys, and the like. Even refractory metals such as Mo, Ta, W, etc. can be formed by a high energy density laser. However, because tungsten has the characteristics of high melting point, high thermal conductivity, high melt viscosity, affinity to oxygen at high temperature, brittleness at room temperature and the like, holes and cracks appear in the pure tungsten part after laser scanning, the mechanical properties of the tungsten component are seriously influenced, the application of the pure tungsten component is limited, and the problems are great difficulties and challenges faced by selective laser melting of pure tungsten at present.

Disclosure of Invention

Aiming at the defect that the traditional powder metallurgy technology can not prepare a pure tungsten component with a complex structure, the invention aims to provide a method for preparing the complex pure tungsten component by utilizing selective laser melting and greatly improving the mechanical property of the complex tungsten component prepared by selective laser melting. By adding carbon element into pure tungsten powder, on one hand, the carbon element reacts with the tungsten powder and oxygen in protective atmosphere by utilizing the strong reducibility of the carbon element at high temperature, so that the oxygen content is reduced, and the porosity is reduced; on the other hand, the carbon element reacts with tungsten at high temperature to generate tungsten carbide which is used as a strengthening phase to improve the mechanical property of the tungsten part. The mechanical property of the pure tungsten component is improved by reducing the problems of pores and cracks in the selective melting process.

The purpose of the invention can be realized by the following technical scheme:

a method for preparing a pure tungsten component with a complex structure by selective laser melting comprises the following steps:

step one

Selecting pure tungsten powder as original powder to prepare W/C composite powder; in the W/C composite powder, the content of C is 0.1-0.5 wt%, preferably 0.25-0.35%;

step two

Constructing a part model to be prepared by using three-dimensional software, and guiding the constructed model into selective laser melting molding equipment;

step three

And placing the prepared composite powder into a powder supply cylinder in selective laser melting equipment, and introducing protective gas into a forming cavity for atmosphere protection.

Step four

Setting technological parameters of the selective laser melting processing process, and performing laser sintering on the prepared powder;

step five

And carrying out linear cutting and ultrasonic cleaning on the printed part to obtain the tungsten part.

Preferably, the particle size range of the pure tungsten powder is 10-35 μm. More preferably, the pure tungsten powder has a D50 of 22.5 μm.

Preferably, the three-dimensional software comprises Magics.

Preferably, the W/C powder is prepared by the following 2 methods:

the method comprises the following steps: ball milling mixed powder

Taking tungsten powder and graphite powder as raw materials, wherein the particle size range of the graphite powder is 1-8 mu m, the D50 is 3 mu m, and the mass percentage of the tungsten powder is as follows: graphite powder 99.7: 0.3, weighing tungsten powder and graphite powder, and putting the tungsten powder and the graphite powder into a ball milling tank containing stainless steel balls, wherein the mass ratio of the ball materials is 2: 1, ball milling is carried out in a ball mill for 12 hours at the rotating speed of 50rpm by taking argon as a protective atmosphere. And (4) sieving the powder subjected to ball milling, and then putting the powder into a vacuum drying oven for drying to obtain W/C powder for later use.

The method 2 comprises the following steps: plasma spheroidizing carburizing

According to an advantageous embodiment of the invention, for the raw tungsten powder, carburization during spheroidization is used. During the spheroidization process, the agglomerated or irregularly shaped powder particles can be remelted and then formed into spherical droplets by centrifugal force and surface tension and rapidly solidified into powder particles in a solidification bin. The spheroidized powder has a spherical shape, thereby having excellent fluidity. The spheroidization of the tungsten powder is carried out in a reaction containing carbon in Ar₂Adding CH₄As carbonizing agent, by Ar₂-CH₄The mixed carrier gas sends the powder particles into the plasma region, the powder particles are melted into liquid in the high-temperature environment of the plasma region,CH4 is cracked at high temperature to produce activated carbon atoms which are absorbed by the molten liquid particles, which solidify into spherical shapes under the action of centrifugal force and surface tension during subsequent cooling, and the spheroidized powder particles are collected in a collection bin below the instrument. By this process, the particles are uniformly carburized, and the carbon content of the powder is changed by changing Ar₂And CH₄Is adjusted. And then, sieving the spheroidized powder, and then putting the spheroidized powder into a vacuum drying oven for drying to obtain W/C powder for later use.

Preferably, argon is introduced into the forming cavity as protective gas in the processing process, so that the oxygen content in the forming cavity is ensured to be less than 0.1%.

Preferably, the substrate heating temperature is set to 100 to 180 ℃, preferably 175 to 180 ℃.

Preferably, the diameter of a laser spot is set to be 90-130 mu m, preferably 130 mu m, the laser power is set to be 400-475W, the laser scanning speed is 400-600 mm/s, the laser scanning interval is set to be 40-80 mu m, and the powder spreading thickness is set to be 20-40 mu m.

The method for preparing the pure tungsten component with the complex structure by selective laser melting provided by the invention adds a proper amount of carbon element into pure tungsten powder by two methods of ball milling and plasma spheroidizing carburization, and then performs selective laser melting. By the reduction of carbon element and the reaction with oxygen in the powder and in the atmosphere, CO or CO is formed₂And the impurity oxygen is removed, the oxygen content in a formed sample is reduced, the oxygen segregation at the grain boundary is reduced, the grains are refined, the porosity is reduced, and the cracks are reduced. And tungsten and carbon react at high temperature to generate tungsten carbide which is used as a strengthening phase to improve the mechanical property of the tungsten product. The method for preparing the complex pure tungsten component by selective laser melting has simple and reasonable process and high production efficiency, and provides a method for preparing the pure tungsten component with a complex structure and effectively improving the mechanical property of the pure tungsten component.

According to the method for preparing the pure tungsten member with the complex structure through selective laser melting, the density of the obtained member is more than or equal to 98.5%, and the compressive strength of the obtained member is more than or equal to 1280 MPa. After optimization, the density of the obtained member is 99.2-99.5%, and the compressive strength is 1420-.

The specific implementation mode is as follows: