Improvement of rheological properties of Inconel 718 MIM feedstock using tailored particle size distributions

Abstract

One of the most important stages in the metal injection moulding (MIM) process is feedstock fabrication, since the rheological properties of the feedstock are of crucial importance in the injection moulding step. In the present work, the possibility of replacing a conventional MIM superalloy feedstock (particle size <20 μm) by a mixture of powders with different particle size ranges, to tailor the flow properties, was investigated. Five Inconel 718 feedstocks were prepared with the same binder (HDPE–paraffin wax–stearic acid) and different mixes of four spherical gas atomised powder fractions (<22; 16–45; 45–63; 65–212 μm). The rheological characteristics and processability of each feedstock were evaluated with a capillary rheometer to determine flow index, yield stress and activation energy.