The impact of injection velocity on the defects in thick components fabricated by inserted metal injection molding

Abstract

Abstract The initial stage of shaping a component in metal injection molding is the injection process. Any defects occurring in this stage are transferred to the subsequent stages, namely debinding and sintering. To investigate the jetting phenomenon in the current study, 316L stainless steel feedstock was exploited as the material for fabricating thick cylindrical specimens with a diameter of 20 mm. Regarding the aforementioned thick specimens, injection at the normal velocity of 15 cm3 s–1 resulted in critical defects, such as folding, weld lines and porosity. It was found that these defects were eliminated in the specimens injected at velocities as low as 1 cm3 s–1. Under such conditions, however, due to the increase in the injection time, the flow front rapidly solidifies with ensuing dramatic deterioration of component surface quality. Furthermore, the present study proposes a novel method, entitled inserted metal injection molding, with a double aim both for removing the jetting phenomenon and the consequent defects in injected components and for making the injection process possible at normal velocities allowing fabrication of the components with high surface quality.