Abstract Powder injection moulding is a low-cost manufacturing process that produces very complex parts to net shapes in a wide variety of materials and unique alloys, including superalloys, stainless steels, and carbides. The feedstocks used in this process must meet various requirements. They have to show good flowability for the injection process, but they also need to have high solids loading to reduce shrinkage during sintering. In the present study, we investigated the rheological behaviours of Inconel feedstock with various average particle sizes in a polydisperse population from 6 to 66 μm and solids loading (ϕ = 50%–72%) at a shear rate of 10–105 s− 1. The binder formulation was a polymer-based aqueous system composed of 55 vol% polyethylene glycol (PEG), 40 vol% polypropylene (PP), and 5 vol% stearic acid (SA). In particular, the effects of particle size, flow activation energy and the mouldability index on the rheology of the feedstock were studied in detail. New rheological models that describe the effects of various parameters such as shear rate, particle size, temperature, and solids loading are introduced, and their predictions are compared with the experimental values. These rheological behaviours were also characterised using our empirical models, which can be directly applied to the process optimisation of powder injection moulding for micro-components. As a result, rheological parameters such as flow behaviour index, maximal solids loading, and flow activation energy were obtained. The particular rheological behaviour of the Inconel feedstock with a highly concentrated solids fraction, which deviates from typical pseudoplastic behaviour, has a relevant correlation with the proposed models. Moreover, the models can be used when similar behaviours are observed in other formulation, powder and binder systems.

中文翻译：

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粒度分布和温度对高浓度Inconel原料合金718流变性能的影响

摘要 粉末注射成型是一种低成本的制造工艺，可将非常复杂的零件生产为采用多种材料和独特合金（包括高温合金、不锈钢和碳化物）的净形状。该过程中使用的原料必须满足各种要求。它们必须在注射过程中表现出良好的流动性，但它们还需要具有高固体含量以减少烧结过程中的收缩。在本研究中，我们研究了具有不同平均粒径的 Inconel 原料在 6 至 66 μm 和固体负载 (φ = 50%–72%) 的多分散体中在 10–105 s− 1 的剪切速率下的流变行为粘合剂配方是一种基于聚合物的水性体系，由 55 vol% 的聚乙二醇 (PEG)、40 vol% 的聚丙烯 (PP) 和 5 vol% 的硬脂酸 (SA) 组成。特别是，详细研究了粒度、流动活化能和可塑性指数对原料流变性的影响。介绍了描述各种参数（如剪切速率、粒度、温度和固体负载）影响的新流变模型，并将它们的预测与实验值进行了比较。这些流变行为也使用我们的经验模型进行了表征，可以直接应用于微部件粉末注射成型的工艺优化。结果，获得了流变参数，例如流动行为指数、最大固体负载和流动活化能。具有高浓度固体部分的 Inconel 原料的特殊流变行为，与典型的假塑性行为不同，与提出的模型有相关性。此外，当在其他配方、粉末和粘合剂系统中观察到类似行为时，可以使用这些模型。