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

The micro extrusion of feedstock is a promising emerging technology for manufacturing very high length to thickness aspect ratio metallic micro components which are not feasible by conventional metal processing methodologies or commonly used feedstock processing technologies. Extrusion of high aspect ratio micro components 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 micro components 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 micro bi-lumen tubes using bio-compactible steel feedstocks AISI316L and 17-4PH with two different ageing. The geometrical features of the extruded bi-lumen tubes, surface roughness and structural properties are analysed using 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 in great extent. An average Sa roughness deviation from 1.73 μm to 4.57 μm was observed for feedstocks 17-4PH and AISI316L. The study also confirms that binder properties and ageing of the feedstocks also have to be taken into account for maintaining the surface finish and structural properties in case of metallic feedstock Keywords: micro extrusion, bi-lumen tube, feedstock extrusion of high aspect ratio bi-lumen tubes.