Effect of binder composition on rheology of iron powder injection moulding feedstocks: Experimental design

A statistical analysis based on the McLean-Anderson design method was conducted to study the influence of each binder component on the flow properties of iron feedstocks for powder injection moulding. The formulations were composed of carbonyl iron powder (FE), polyethylene resin (PE), polyethylene wax (PEW), and stearic acid (SA). The viscosities of 15 different formulations were measured using a capillary viscometer. Fluidity and pseudoplasticity were evaluated and the effect of each component on these properties was analysed. The studied composition ranges of FE, PE, PEW, and SA were 90-92, 3-4·5, 2-4, and 0-1·5 wt-% respectively. It was found that lower iron powder content or higher binder content improved the fluidity of the feedstock. The relative effectiveness of binder ingredients in increasing fluidity is SA > PEW > PE and in enhancing pseudoplasticity PE > PEW > SA. Feedstocks with binder phases containing about 50 wt-%PE have the greatest fluidity with flow index n in the range 0·6-0·8.