Effect of powder particle size on the rheology of feedstocks for low pressure powder injection moulding

Powder Injection Moulding (PIM) is a widespread technology for the fabrication of metal and ceramic components. Thanks to recent development within the field of Additive Manufacturing (AM), more and more focus is spent on the integration between AM and PIM. The use of AM to produce moulds for the injection moulding sector has pointed out new challenges: among others, the mould deformation during the filling stage. This issue is particularly severe when dealing with the injection of PIM feedstocks. The high viscosity of PIM feedstocks require elevated injection pressures. In this paper, the possibility to tailor the rheological properties of a feedstock by changing the distribution of powder particle size is investigated, taking into consideration the effect of specific surface area and interparticle forces. Finer powders with narrower distribution, higher specific surface area and presence of colloids showed higher viscosity, while coarse powder with broader particle size distribution and mainly non-colloidal particles resulted in lower viscosity.