Study of the influence of powder and binders characteristics on rheological behavior and moldability properties of low-pressure powder injection molding stainless steel feedstocks

The fabrication of small as well as sophisticated and cost-effective metallic parts which are of proper geometric tolerances and dimensions is a significant goal in the present manufacturing industries. In the manufacturing industry, all these requirements can be encompassed through low-pressure powder injection molding LPIM. In this study, the rheological behavior of feedstocks using water-atomized stainless steel 17-4PH metal powder under LPIM is investigated by variations of solid loading and particle size distribution of 3 μm and 10 μm. Since LPIM’s feedstock is exposed to high stringent characteristics, the study emphasizes on powder and binder system in which stainless steel 17-4PH powder is mixed with composite binder composition, which consists of paraffin wax PW, stearic acid SA, and ethylene vinyl acetate EVA and examined by variation of solid loading concentration. In addition, the rheological properties such as the impact of thermal equilibrium, different solid loading, particle size distribution, shear rate and temperature were performed by using a rotational rheometer MCR 302. Since the geometry of the water atomized stainless steel metal powder is an irregular shape, the rheological properties can significantly influence the surface quality, resolution capabilities, and shape retention. Hence, the LPIM rheological characteristics as a function of water atomized stainless steel powder are evaluated by viscosity, moldability, and feedstock characteristics. Moreover, during the experimental investigation, different tests were repeatedly conducted with the same feedstock after a specific waiting time since results obtained were different for the same method and feedstock composition. The feedstock samples with the stainless steel powder at different solid loading of 48, 60, and 65 vol. % were investigated at shear range from 0.5 to 3500 s-1 with different binders at temperatures of 70, 80, 90, and 100°C. Results were demonstrated by evaluating the effect of shear rate on the feedstock viscosity in the graphical representation and has been seen that the viscosity of the powders decrease as the shear rate is increased in a feedstock containing PW-SA whereas it behaves unexpectedly in a feedstock containing PW-SA-EVA as the viscosity does not change with increasing temperature