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The design of the trimodal powder feedstock and its feasibility for micro powder injection molding (μ-PIM) were investigated. The feedstock was prepared by mixing Fe micropowder (D 50 = 4 μm) and nanopowder agglomerate composed of a bimodal particle distribution (D 50 = 330 nm and D 50 = 30 nm, respectively) with low viscosity wax-based binders. The homogeneity of the feedstock was evaluated by torque rheometer, microstructure observations, binder burnout analysis, and an extrusion test. The trimodal concept in this study effectively improved the powder loading up to 72 vol%, and the feedstock with 70 vol% powder loading exhibited good homogeneity and flowability. By using the feedstock, the microparts were successfully replicated with sufficient shape retention to be potentially useful for a range of μ-PIM applications. [ABSTRACT FROM AUTHOR]

The densification and grain growth behavior of powder injection molded 316L stainless steel micro–nanopowder were investigated in terms of microstructural development. The sintered density of the micro–nanopowder sample increased remarkably in the temperature range of 1000 to 1100 °C due to the sintering effect of nanopowders which increased the number of grain boundaries acting as high material transport path. A near full density of 98% TD was obtained after sintering at 1100 °C for 5 h with the average grain size less than 10 μm, indicating that there was no drastic grain growth. The presence of nanopowders in micro–nanopowder played decisive role in the entire sintering process by enhancing densification but suppressing grain growth. These effects open up the possibility of using micro–nanopowder feedstock to control the sintering behavior of powder injection molding products with full density and fine microstructure. [ABSTRACT FROM AUTHOR]