Experimental analysis of the evolution of the physical properties of pyramidal-shaped metallic replicas made using the MIM process

Abstract

In the applications of powder injection moulding (PIM), the metallic powders are the most popular material. In our study, three metallic powders with different compositions, particle shapes and particle sizes have been selected as the test materials to produce micro-structured parts using injection moulding process. The combination of three binders (polypropylene, paraffin waxes and stearic acid) with a constant and adapted formulation has been chosen as a binder system. The mixtures obtained by mixing the metallic powders and the binder system with solid loadings ranging from 56 to 64 vol.% have been used as the feedstocks for the next injection moulding. The viscosity of mixture increased with increasing solid loading. These feedstocks were injected using the same injection moulding conditions in the metallic mould structured with pyramidal shape manufactured using electro-erosion machining. The debinding and sintering process have been carried out at different temperatures to eliminate the binders in the injected replica and obtain the final metallic die mould. To analyse the physical properties evolution of the die mould manufactured by PIM and the influence factors (powder nuance, solid loading and sintering conditions), the shrinkage rate, density, roughness of surface, Vickers hardness and mass losses in metallic mould cavities were investigated. The experimental results demonstrate that properly micro-structured parts can be obtained using the process chain of injection, debinding and sintering with metallic powders.