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| Study on injection molding process of complex parts for iron-based alloys |
| ZHOU Fen1，LUO Meng2，XIE Min1，BAO Jinxiao1，GAO Jianquan1，SONG Xiwen1 |
| 1.School of Materials and Metallurgy，Inner Mongolia University of Science and Technology，
Baotou 014010，China；2.Suzhou Shareate Tools Co.，Ltd，Suzhou，215121，China） |
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Abstract The iron-based alloy part with complex shapes and thin walls could not be prepared by conventional
methods. In this paper,the iron-based alloy part made of Fe-Ni-Co-Mo-Ti alloy was produced by powder injection
molding. Oxides were used as raw materials, and high-density polyethylene (HDPE), polyethylene-ethylene ethyl
acetate copolymer (EVA), paraffin (PW) and stearic acid (SA) were used as binders to study the optimal binder
composition and optimal solids content for feeding. On this basis, the optimal process of n-heptane degreasing and
the influence of thermal degreasing atmosphere on carbon and oxygen content in products were studied. The composition
of the optimized binder system was determined by testing the relationship between the torque and time of
feedstock, and combining with the quality of the green parts measuring. The optimal solids loading of feedstock
was determined by torque rheometer. The microstructures of the mixed powder, the green part, the solvent-debound
part, and the thermal-debound part were observed using a field emission scanning electron microscope (FESEM)
and scanning electron microscopy (SEM). The mixing torque was recorded using a torque rheometer (ZJL-200) at
115 ℃ and 45 r/min. The contents of carbon and oxygen residues in the sintered samples were measured by a carbon/
sulphur determinator (CS-8810) and an oxygen and nitrogen analyzer (ON-2000), respectively. The influence
of different debinding atmospheres on the carbon and oxygen residues in the sintered samples were also investigated.
The densities of the sintered samples were tested using Archimedes’method. The results show that the
feedstock with the binder composition of 15% HDPE-75% PW-8% EVA-2% SA and with the optimum solid content of 50% has a good fluidity and the green parts have high strength. The optimum condition for the binder
removal of n-heptane is 80 min-40 °C. The thermal debinding atmosphere affects the carbon and oxygen content of
the product. When debinding in hydrogen atmosphere, the residual carbon content is high, the residual oxygen content
is low, and the argon atmosphere is opposite. The product sintered in hydrogen atmosphere has an iron phase
and has a high density. Complex parts of Fe-Ni-Co-Mo-Ti base alloy with complex shapes and thin walls can be
prepared by powder injection molding technology with the binder system of 15% HDPE-75% PW-8% EVA-2% SA
and the optimal solid content consisting of 50%.
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Received: 29 December 2021
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2022, Vol. 32 
