Mixing and characterisation of 316L stainless steel feedstock for micro powder injection molding

In recent years, micro powder injection molding (μPIM) is being explored as an economical fabrication method for microcomponents. μPIM, adapted from powder injection molding (PIM), has the same four main processing steps as PIM: mixing of powder and binder system to form the feedstock, injection molding, debinding and sintering. Unlike PIM, the feedstock for μPIM requires more stringent characteristics. Thus, commercial feedstock may not be suitable especially for microstructures with high aspect ratio. In this paper, the mixing, characterisation and feasibility of an in-house feedstock for the injection molding of microstructures, each of φ100 μm×height 200 μm, is reported. The feedstock comprises 316L stainless steel and a multi-component binder system. The effects of powder loading and extrusion on mixing and feedstock homogeneity were investigated. The rheological and thermal characteristics of the feedstock were determined and used in subsequent processing steps. The results show that the feedstock can be used for the fabrication of the microstructures with good shape retention.