Rheological and mechanical assessment for formulating hybrid feedstock to be used in MIM & FFF

Abstract

Processes involving additive manufacturing (AM) and Powder Injection Moulding (PIM) in industry show great potential in producing parts with complex shapes, covering both short series of customed components and high production volumes. A deep study into the fundamentals of the material flow behaviour according to both processing methods requirements, not previously described, is carried out and the synergy of PIM and AM based on Fused Filament Fabrication (FFF) is confirmed. The significance of having a robust material, defined as “hybrid feedstock”, carefully designed to enable the FFF and PIM process, including the debinding and sintering stages, is discussed. The mechanical properties of the 17-4 PH filaments, such as shear strength and maximum force, are analysed, and it is concluded that the choice of an appropriate binder system is crucial for achievement optimal performance during the printing process. The rheological properties of the materials (fluidity and shear thinning behaviour) are also examined and the importance of considering printing speed and temperature to control nozzle pressure and ensure successful printing is emphasized. Furthermore, the mechanical properties of the filaments with different metallic powder loadings are discussed, The need to stablish limits for material suitability in terms of shear stress and activation energy is also mentioned. Overall, the scientific discussion addresses various relevant aspects related to the mechanical and rheological properties of the materials used in 3D printing of metals using FFF technology. Conclusions based on experimental results are provided and key parameters to consider for successful printed parts are highlighted.