Research on Tungsten Powder 3D Printing Process Based on Binder Jetting
Release time:
2025-11-13
0 Introduction
Binder jetting additive manufacturing (BJAM) is a powder-based additive manufacturing technology initially proposed by Emanuel Sachs et al. at the Massachusetts Institute of Technology. It employs inkjet printheads to selectively deposit binder for rapid part formation. Binder jetting shares similarities with injection molding: it first forms the target shape using binder and powder, followed by post-processing steps of debinding and sintering to achieve part densification and metallurgical bonding.
Binder jet metal 3D printing is a rapid, low-cost additive manufacturing technique with unique advantages. Compared to traditional casting processes, it easily produces complex geometries without conventional machining constraints, enabling the fabrication of parts with intricate internal structures unattainable through conventional methods. Material selection is diverse, encompassing ceramics, sand, and metals. Compared to other 3D printing technologies, Binder Jetting offers lower costs by utilizing relatively inexpensive raw material powders, thereby reducing material expenses [1-3].
Tungsten-infiltrated copper composites possess a unique combination of properties, making them advantageous in applications requiring high electrical conductivity, high-temperature resistance, high hardness, and wear resistance. Composites manufactured via the tungsten infiltration process meet the demands of high-performance applications, particularly in precision manufacturing, aerospace, and power electronics sectors. Traditional preparation of tungsten-infiltrated copper composite blanks involves powder metallurgy pressing. However, pressed blanks exhibit density inhomogeneity, high porosity, and limited shape diversity, making complex part geometries unfeasible while incurring high mold manufacturing costs. In these aspects, binder jetting printing of tungsten skeletons for producing tungsten-infiltrated copper products offers significant advantages.
Binder jetting 3D printing processes and product requirements typically favor powders with concentrated particle size distribution and high sphericity [2], commonly within the 0–30 μm range. This work primarily investigates the printing process for irregular tungsten powder with a particle size range of 15–60 μm and lower cost. This research aims to facilitate the widespread application of binder jetting 3DP for printing tungsten-copper infiltrated composites and advance the development of binder jetting technology.
1. Experiment
Tungsten powder with a particle size range of 15–65 μm (as shown in Figure 1) was selected. Its particle size distribution (PSD), density, and flowability were characterized. The powder consists of irregularly fractured particles. The PSD results for the particle size distribution are as follows: D10, D50, and D90 were 17 μm, 33 μm, and 63 μm, respectively. The angle of repose was 21°, with a bulk density of 9.2 g/cm³ and a tapped density of 11.9 g/cm³. Forming experiments were conducted on an AJM500 device (Ningxia Shared), using a water-based metallic binder [4-5].
The formed specimens are 100mm × 100mm × 10mm cubes, Φ10mm × 10mm compressive test blocks, and Φ25mm × 30mm cylinders. To determine the process parameters for binder jetting printing of low-cost tungsten powder, experiments were conducted to adjust different printing parameters. Since the speed of the spreading roller and the compaction roller affects the uniformity of powder bed spreading, thereby influencing the appearance quality of the printed green body, the binder saturation parameter affects the appearance quality and green body strength of the specimen. Binder saturation is defined as the ratio of the air gap between powder particles to the binder volume. The selection of binder saturation primarily depends on the wettability between the powder and the binder. Excessively low binder saturation typically results in insufficient bonding between powder particles, leading to green body delamination and reduced strength. This hinders powder removal and green body handling. Conversely, excessively high binder saturation/ concentration can cause excessive wetting between powder layers, causing the binder to adhere to the powder spreading roller and pick up excessive powder. This severely impacts dimensional accuracy. Additionally, excessively high binder saturation can lead to ink bleeding. In this experiment, a binder saturation of 55%–70% was selected for printing. Layer thickness directly impacts green body density. This refers to the thickness of powder deposited per print layer, critically affecting surface quality. Excessively thin layers cause powder pushing during printing, while overly thick layers reduce green body density and compromise strength. For this experiment, layer thicknesses were set at 60, 70, and 80 μm. Powder bed temperature parameters also affect the final green body formation quality. Too low a temperature may cause ink seepage, while too high a temperature may trigger premature binder reaction, leading to sample delamination and potential damage to the printhead. After printing samples with different parameter sets, the build chamber was placed into a curing device at 200°C. Samples were removed after 5 hours of curing and deburred to obtain specimens for each experimental group.
2 Results
2.1 Effect of Leveling Roller and Compaction Roller Speed on Powder Distribution
The leveling roller primarily disperses powder and removes excess material, while the compaction roller consolidates and levels the powder bed. Three parameter sets were tested as shown in Table 1 to determine optimal powder distribution parameters.
As shown in Figure 2, the best powder bed leveling effect was achieved under Scheme 3, where the compaction roller speed was 13 r/s and the leveling roller speed was 6 r/s.
2.2 Effect of Temperature Parameters on Green Body Quality
The primary purpose of setting the powder bed temperature is to evaporate moisture from the binder, increase the viscosity of the binder in the formed sample, prevent further binder penetration causing ink bleeding in the product, and ensure dimensional accuracy of the green body. To this end, four sets of parameters (see Table 2) were set for comparative printing of test specimens to determine the optimal temperature parameters.
As shown in Figure 3, when the temperature was set to 55°C, the pre-powder spreading heating speed was 10 mm/s, and the printing heating speed was 60 mm/s, the product exhibited superior surface quality with no ink bleeding.
2.3 Effect of Binder Saturation on Green Body Quality
Binder saturation, a critical process parameter, determines the feasibility of printing. It significantly influences the dimensional accuracy of the printed part and the strength of the green body. Inappropriate binder saturation may lead to printing defects and failures. Binder saturation affects the penetration of binder within the powder bed. Insufficient saturation prevents proper bonding between powder layers and reduces specimen strength, compromising suitability for post-processing. Conversely, excessive saturation causes excessive binder penetration into non-target areas, resulting in poor dimensional accuracy. Therefore, selecting an appropriate binder saturation level is essential to ensure printed specimens possess adequate strength without compromising other forming qualities [6-8].
As shown in Table 3, the experimental plan was designed with printing parameters set at binder saturations of 55%, 60%, 65%, and 70%, followed by specimen printing.
Table 4 presents compressive strength data for printed specimens at binder saturation levels of 55%, 60%, 65%, and 70%. As shown in Figure 4, increasing binder saturation enhances specimen compressive strength. At 60% saturation, compressive strength reaches approximately 7 MPa, meeting the requirements for powder removal strength.
As shown in Figure 5, at 55% saturation, the edges of the printed green body are indistinct and exhibit low strength; At 65% saturation, the green body exhibited slight ink bleeding on the surface; at 70% saturation, severe ink bleeding occurred. At 60% binder saturation, the printed green body demonstrated good surface quality and strength meeting the powder removal requirement.
The selection of powder bed thickness generally depends on the powder's particle size distribution or average particle diameter. Typically, a bed thickness of 2–3 times the powder volume is chosen, with an average particle diameter exceeding the D90 value to ensure stable powder flow. To ensure a level powder bed surface, experiments were conducted with designed powder layer thicknesses (60, 70, 80 μm) under appropriate powder spreading speed, roller rotation speed, and saturation conditions. These experiments validated the influence of layer thickness on green body dimensional accuracy and relative density.
The effect of powder layer thickness on green compact dimensional accuracy is shown in Table 5. Smaller print layer thicknesses yield higher dimensional accuracy in green compacts, with reduced dimensional deviations in both diameter and height directions.
As shown in Table 6, the relative density of green compacts decreases with increasing print layer thickness. The highest average density of 51.62% was achieved at a print layer thickness of 60 μm. As shown in Figure 6, the printed green compact exhibits powder streaks. This is primarily due to the powder particle size D90 being 63 μm and the layer thickness set to 60 μm. During printing, larger powder particles are extruded as the compaction roller moves, causing powder streaks in the green compact. Therefore, considering the combined effects of layer thickness on green compact dimensions and density, the optimal printing condition is achieved at a layer thickness of 70 μm.
3 Conclusions
Higher compaction roller speeds result in a flatter powder bed. At 13 r/s, the powder bed appears smooth and streak-free. Low binder saturation causes layering, indistinct edges, and reduced strength, while high saturation leads to powder extrusion. Thus, 60% saturation yields the optimal overall quality.
As the powder layer thickness increases, the dimensional error of the green compact gradually increases. With increasing powder layer thickness, the relative density of the green compact decreases. The optimal green compact quality is achieved at a powder layer thickness of 70 μm.
Source: Materials Reports 2024, Vol. 38, No. Z2 www.mater-rep.com, Research on Tungsten Powder 3D Printing Process Based on Binder Jetting, Chen Weidong, Zhang Longjiang, Dong Zhichao, Yang Zhengxue, Li Ting
Stardust Technology's spherical tungsten powder is produced using core radiofrequency plasma spheroidization technology. As a flagship product of this national high-tech enterprise, it boasts a purity ≥99.95% and oxygen content ≤200ppm, combining high cleanliness with exceptional stability. The powder exhibits over 95% sphericity, smooth surfaces free of satellite particles, and minimal hollow particles. Particle size is customizable between 5-150μm, with a bulk density ≥10.0g/cm³ and excellent flow properties. Leveraging tungsten's inherent advantages of high-temperature resistance and radiation shielding, this product is compatible with laser/electron beam additive manufacturing, hot isostatic pressing, and laser cladding processes. It finds extensive application in high-end sectors such as aerospace high-temperature components, defense and military industries, target materials, and medical devices, providing reliable powder material support for advanced manufacturing. For further details, please contact our professional manager Cathie Zheng at +86 13318326187.
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