Effect of Feedstock Properties on Extrusion of High Aspect Ratio Microbi-Lumen Tubes

The micro-extrusion of feedstock is a promising and emerging technology for manufacturing very high length to thickness aspect ratio metallic microcomponents which are not feasible for conventional metal processing methodologies or commonly used feedstock processing technologies. Extrusion of high aspect ratio microcomponents using metallic feedstock confronts the challenges of achieving a continuous extrusion without any breakage, the geometrical accuracy, surface finish and structural properties for the component which are required for the micro-application, during micro-extrusion process. The type of metallic powder, powder size, type of binder, and binder properties are very decisive in making the extrusion process feasible for the micro-application. The influence of feedstock properties on micro-extrusion of high aspect ratio microcomponents are still unknown in case of micro-extrusion of feedstock. In this research work, the effect of type of feedstock on micro-extrusion is studied by extruding microbi-lumen tubes using biocompatible steel feedstocks AISI316 L and 17-4PH at two different aging states (no aging and 1.5 years aging). The geometrical features of the extruded bi-lumen tubes, surface roughness and structural properties are analyzed using three-dimensional (3D) focus variation microscopy, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The analysis showed that feedstock type affects the feasibility of extrusion and geometrical size to a great extent. An average Sa roughness deviation from 1.73 to 4.57 mu m was observed for feedstocks 17-4PH and AISI316 L. The study also confirms that binder properties and aging of the feedstocks also have to be taken into account for maintaining the surface finish and structural properties in case of metallic feedstock extrusion of high aspect ratio bi-lumen tubes.