Characterization of 17-4 PH stainless steel metal injection molding feedstock using mixing torque data

Abstract

Currently, there are many components produced by a metal injection molding process in automotive, consumer goods, medical, and electronics. Metal Injection Molding process (MIM process) consists of four stages, mixing, injection molding, debinding, and sintering. Feedstock plays critical roles in the MIM process since the feedstock's low quality cannot be corrected later. Feedstocks, which are a mixture of powder and binder, are mixed at an elevated temperature. A feedstock should be homogeneous and has a pseudo-plastic behavior. In the MIM process, the shear rate during injection molding is usually 10 to 10 000 s-1. Within the shear rates range, a maximum viscosity for injection molding was 100 Pas at molding temperatures. In this paper, the rheological characteristic of feedstocks was analyzed using the torque rheometer. The objective of this research was to find the value of viscosity and compare to the Material Safety Data Sheet (MSDS) of the commercial feedstock by using torque mixing data. All the three feedstocks had pseudo-plastic behavior and below 100 Pas within shear rates range. Form the validation of injection molding experiment, feedstock B with solid loading 60 %, and binder system consists of 35 % PP, 64% PW, and 1 % SA showed a good flowability and moldability.