Exploring Micro-focus X-ray computed tomography for metal injection moulded green parts

Abstract

Metal injection moulding (MIM) involves mass production of simple to intricate near-net shape parts at a relatively low cost by blending metal powders of defined characteristics with a polymeric binder system. The blend, popularly known as a feedstock, is injected into a mould cavity of a desired shape to form a green part. Most defects such as cracks, sink marks and voids manifest during the injection stage of the process. Internal cracks and voids are impossible to visualise after injection moulding. Micro-focus X-ray computed tomography (µXCT) is one of the techniques that can be used to evaluate and characterise such defective features. μXCT is a non-destructive method that uses penetrating X-ray radiation to probe objects or samples and create a complete virtual 3D representation of the object to visualise the internal structures and morphologies such as porosity, voids, cracks and inclusions as well as their location and their distribution in 3D. This work is intended to explore the µXCT approach MIM green parts and characterise the internal defects. The samples were scanned at 135 keV and 100 µA for X-ray penetration and contrast while placed onto a rotating sample manipulator which facilitated scanning through 360°. The samples were then reconstructed and further analysed for volume (3D) graphics.