A binder jet 3D printing forming method of refractory metals

Abstract

The present application relates to the technical field of additive manufacturing of refractory metals, and a binder jetting 3D printing forming method of refractory metals, comprising the following steps: S1, selecting a refractory metal powder as a raw material; S2, performing high-energy ball milling treatment; S3, mixing with a PVA aqueous solution, preparing uniform droplets by using a centrifugal disc atomization method or a spraying method, and drying; S4, performing sieving treatment; S5, performing binder jetting 3D printing; S6, after printing is completed, performing drying and solidification, then cleaning the powder around the parts, and obtaining a printed green body; and S7, sintering the printed green body, and obtaining a sintered body. The present application adopts a fine particle size powder of a refractory metal to perform 3D printing, the raw material is simple and easy to obtain and has low cost, the binder jetting 3D printing process has high efficiency, the product has high size precision, the machining amount is reduced, the powder utilization rate is improved, and the cost is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of additive manufacturing of refractory metals, in particular to a binder jetting 3D printing forming method of refractory metals. BACKGROUND

[0002] At present, for refractory metals tungsten, molybdenum and their alloys, the traditional powder pressing forming process is mainly used for preparation. The products prepared by this process are mainly simple-shaped parts. For parts with complex structure, machining is needed, resulting in low material utilization. At the same time, due to the high hardness and brittleness of tungsten, molybdenum and their alloys, the machining cost is extremely high. In recent years, the additive manufacturing process has developed, which has irreplaceable advantages for preparing three-dimensional complex structure parts and can realize near-net forming. However, since this process has very high requirements for powder flowability, the raw materials are mainly spherical or near-spherical powders prepared by atomization process (water atomization, gas atomization, rotating electrode atomization, etc.). Refractory metals tungsten, molybdenum and their alloys are mainly prepared by reduction method, and the powder particle size is fine (≤15 μm) and the sphericity is poor, mainly being polygonal irregular shape. The spherical tungsten, molybdenum powder and their alloys with high flowability need to be prepared by plasma spheroidization process, which has high cost, thereby limiting the application of refractory metals and their alloys in additive manufacturing process. SUMMARY

[0003] In order to overcome the shortcomings of the prior art, the present application provides a binder jetting 3D printing forming method of refractory metals.

[0004] In order to achieve the above-mentioned purpose, a binder jetting 3D printing forming method of refractory metals is designed, characterized by comprising the following steps,

[0005] S1, selecting refractory metal powder as raw material, the particle size distribution range of refractory metal powder is 0

[0006] S2, high-energy ball milling treatment is carried out on the refractory metal powder, and the bulk density of the powder after ball milling is greater than or equal to 5 g / cm³;

[0007] S3, mixing the powder after ball milling with PVA aqueous solution to prepare a suspension, and using centrifugal disc atomization method or spray method to prepare uniform droplets and dry them to form near-spherical powder with multiple powder aggregates;

[0008] S4, sieving the near-spherical powder to obtain near-spherical powder with particle size less than or equal to 30 μm;

[0009] S5, binder jetting 3D printing is carried out using the sieved near-spherical powder;

[0010] S6. After printing, dry and cure at 120~200℃. After drying and curing, clean the powder around the parts to obtain the printed blank.

[0011] S7. Sinter the printed green blank at 1400~1500℃ in a hydrogen atmosphere for 2~5 hours to obtain the sintered blank.

[0012] The refractory metal powder in step S1 includes tungsten, molybdenum, tungsten nickel iron, tungsten copper, molybdenum copper, and molybdenum lanthanum alloy powder.

[0013] The ball milling process in step S2 is characterized by a powder-to-ball weight ratio of 1:1 to 1.2, a ball milling speed of 30 to 100 r / min, and a ball milling time of 90 minutes or more.

[0014] The mass concentration range of the PVA aqueous solution in step S3 is 0.5-5%, and the volume ratio of metal powder to PVA aqueous solution is 0.5-1:10.

[0015] The thickness of the printed layer in step S5 is 3 to 10 times that of D90.

[0016] Compared with existing technologies, this invention uses fine-particle-size powder of refractory metal for 3D printing. The raw materials are simple, readily available and low in cost. The binder jet 3D printing process is highly efficient, produces products with high dimensional accuracy, reduces machining, improves powder utilization, and significantly reduces costs. Detailed Implementation

[0017] The present invention will be further described below with reference to embodiments.

[0018] S1. Tungsten powder is selected as the raw material. The particle size distribution range of tungsten powder is 0 < D10 ≤ 2.5 μm, D50 ≤ 6 μm, and D90 ≤ 12 μm. Refractory metal tungsten is mainly prepared by reduction method. The powder has a fine particle size. Compared with traditional plasma spheroidized tungsten powder, the price of raw materials is reduced by about 70%, which greatly reduces the product manufacturing cost.

[0019] S2. The refractory metal powder is subjected to high-energy ball milling. The weight ratio of powder to ball is 1:1, the ball milling speed is 60 r / min, and the ball milling time is 90 minutes. The loose density of the powder after ball milling is greater than or equal to 5 g / cm³. Through the ball milling process, the powder is dispersed and the morphology of the reduced tungsten powder is greatly improved, making it nearly spherical and improving its flowability. This makes it suitable for binder jet 3D printing technology, which can produce three-dimensional complex structure parts or thin-walled parts, solving the problem of simple shape of products in traditional powder metallurgy processes.

[0020] S3. The ball-milled powder is mixed with PVA aqueous solution to prepare a suspension. The mass concentration of PVA aqueous solution is 0.5%, and the volume ratio of powder to PVA aqueous solution is 1:10. The suspension is prepared into uniform droplets by centrifugal disc atomization or spraying and dried to form near-spherical powder with multiple powder particles aggregated, which greatly improves the flowability of the powder.

[0021] S4. The near-spherical powder is sieved to obtain near-spherical powder with a particle size of less than or equal to 30μm. The near-spherical powder is a powder agglomeration of multiple powder particles. The particle size of the original powder is not changed. Without changing the original particle size state of the powder, the flowability of the powder is greatly improved. During subsequent sintering, due to the fine powder, the sintering driving force is greater, and it is easier to sinter into a dense state. The required sintering temperature is lower. The sintering temperature is related to the particle size of the original powder, but not to the particle size of the near-spherical powder agglomeration.

[0022] S5. Use sieved near-spherical powder for binder jet 3D printing, with a printing layer thickness of 3 times D90;

[0023] S6. After printing, dry and cure at 120℃. After drying and curing, clean the powder around the parts to obtain the printed blank.

[0024] S7. The printed blank is sintered at 1400℃ in a hydrogen atmosphere for 3 hours to obtain a sintered blank. Tungsten is then prepared using a binder jet 3D printing process, which is 5 to 10 times more efficient than the traditional SLM process. The complexity of the prepared product structure is comparable to that of the SLM process, and the dimensional accuracy can be controlled within ±0.3mm. This process can achieve near-net-shape forming of three-dimensional complex structural parts, reduce machining, improve powder utilization, and significantly reduce costs.

[0025] The refractory metal powders in step S1 include tungsten, molybdenum, tungsten nickel iron, tungsten copper, molybdenum copper, and molybdenum lanthanum alloy powders, which can produce a wider variety of materials compared to the traditional SLM process.

[0026] The ball milling process in step S2 is characterized by a powder-to-ball weight ratio of 1:1 to 1.2, a ball milling speed of 30 to 100 r / min, and a ball milling time of 90 minutes or more.

[0027] The mass concentration range of the PVA aqueous solution in step S3 is 0.5-5%, and the volume ratio of metal powder to PVA aqueous solution is 0.5-1:10.

[0028] The thickness of the printed layer in step S5 is 3 to 10 times that of D90.

[0029] When using this invention, fine-particle-size powder of refractory metal is used for 3D printing. The raw materials are simple, readily available and low in cost. The binder jet 3D printing process is highly efficient, produces products with high dimensional accuracy, reduces machining, improves powder utilization, and significantly reduces costs.

Claims

1. A binder jet 3D printing forming method of refractory metals, characterized in that: The method comprises the following steps: S1, selecting refractory metal powder as raw material, the particle size distribution range of the refractory metal powder is 0 S2, the refractory metal powder is subjected to high-energy ball milling treatment, the weight ratio of powder to ball is 1:1~1.2, the ball milling speed is 30~100r / min, the ball milling time is greater than or equal to 90 minutes, and the bulk density of the powder after ball milling is greater than or equal to 5g / cm³; S3, the powder after ball milling is mixed with PVA aqueous solution to prepare a suspension, the suspension is prepared into uniform droplets by centrifugal disc atomization method or spray method and dried to form near-spherical powder with multiple powder aggregates; S4, the near-spherical powder is subjected to sieving treatment to obtain near-spherical powder with a particle size of less than or equal to 30μm; S5, the near-spherical powder after sieving is used for binder jet 3D printing; S6, after printing, drying and curing are carried out at 120~200℃, the powder around the parts is cleaned to obtain a printed green body; S7, the printed green body is sintered at 1400~1500℃, the sintering atmosphere is hydrogen, and the sintering holding time is 2~5 hours to obtain a sintered body.

2. A binder jet 3D printing forming method of refractory metals according to claim 1, characterized in that: The refractory metal powder in step S1 includes tungsten, molybdenum, tungsten-nickel-iron, tungsten-copper, molybdenum-copper and molybdenum-lanthanum alloy powder.

3. A method of binder jet 3D printing of refractory metals according to claim 1, characterized in that: The mass concentration of the PVA aqueous solution in step S3 is 0.5~5%, and the volume ratio of metal powder to PVA aqueous solution is 0.5~1:

10.

4. A method of binder jet 3D printing of refractory metals according to claim 1, characterized in that: The printing layer thickness in step S5 is 3~10 times D90.