Comparative study of partially water-soluble metal injection moulding feedstock based on inconel 718: The effect of polyethylene glycol molecular weight on rheology and debinding

Abstract

Polyethylene glycol (PEG) is a common component of partially water-soluble binder systems used for metal injection moulding (MIM) feedstocks. After injection moulding, PEG is removed from the components by immersion in water. In this work, the processability of MIM feedstocks based on 59 vol. % of Inconel 718 powder in a binder system containing PEGs with molecular weight (Mw) varying in the range of 1,500 - 20,000, poly (methyl methacrylate) and stearic acid was investigated. The results of the rheological analysis showed that viscosity of feedstocks with low Mw of PEG was more sensitive to temperature at higher shear rates, while at lower shear rates the opposite trend was found. Based on overall flow and debinding behaviour, the feedstock containing PEG with Mw of 8 000 was selected as the most suitable for the processing of Inconel 718 via MIM.