Evolution of properties of parts during MIM and sintering of recycled oxide particles

Abstract

Metal injection moulding (MIM) is an established process for high volume production of complex shaped metallic parts using commercially available feedstocks. The characteristics of parts after moulding, debinding, and sintering cannot be simply predictable from raw materials because the properties get altered with the process parameters and the corresponding levels of porosity during processing steps. In this study, physical properties, microstructure, and mechanical properties of the MIM parts have been characterised to understand the evolution of strength during various steps in MIM processing. Feedstocks with different binder loading show a considerable difference in physical as well as mechanical characteristics. During sintering of parts which have solid loading of grinding sludge, simultaneous in situ reduction and densification takes place, whereas only densification occurs in carbonyl iron parts. It is, therefore, possible to make complex shaped parts of different levels of porosity from downgraded shop floor metallic waste.

Effect of powder particle shape and size distributions on the properties of low-viscosity iron-based feedstocks used in low-pressure powder injection moulding

“…They confirmed that feedstock formulated with only recycled powder manifests low flowability due to high inter-particle friction inherent to the powder shape, while the addition of graphite flakes decreases the viscosity and improves the moldability of such low-cost feedstocks. A few years later, the same research group confirmed that recycled iron oxide powders can potentially be used in the production of low-cost MIM components despite lower achievable solid loadings and sintered densities when compared with virgin powders [28].…”