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

Abstract

The initial stage of shaping ac omponent 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 ad iameter of 20 mm. Regarding the aforementioned thick specimens, injection at the normal velocity of 15 cm 3 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 1cm 3 s -1 .U nder 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 an ovel 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.A. Safarian, Ç. Karataş: The impact of injection velocity on the defects in thick components fabricated by IMIM Int. J. Mater. Res.( formerly Z. Metallkd.) 106 (2015) 66 49 Fig. 3. Sintered specimens and microscopic views of their surfaces injected at 1cm 3 s -1 (left) resulting in low surface quality, and injected at 15 cm 3 s -1 (right) resulting in high surface quality.

Ti-6Al-4V ALAŞIM TOZUNDAN HAZIRLANAN BESLEME STOKUNUN KALIPLAMA VE SİNTERLEME PARAMETRELERİNİN ARAŞTIRILMASI

“…Enjeksiyon hızı yavaş olduğunda da yüzey düzgün olmazken enjeksiyon hızı hızlı olduğunda ise ürünün özellikle kalın bölgelerinde gözenekler oluşmaktadır [27]. Ayrıca besleme stoklarının yüksek debi ve enjeksiyon basınçlarında kalıplanmaları numunelerde toz ve bağlayıcı ayrışmasının oluşmasına da sebep olmaktadır.…”