Study of rheological and sintering behavior of iron-based feedstock used in low-pressure metal injection molding

Abstract

This research project investigates the possibility of producing low-cost petal injection molding (PIM) parts from irregular iron-based powders produced by Rio Tinto Metal Powders Company. Mainly water-atomized iron powders with different post-processing conditions (milling, sieving, and annealing), chemical compositions, and particle sizes were primarily tested based on the possibility of producing flowable feedstocks. The low-pressure powder injection molding (LPIM) approach was employed to formulate feedstock with maximum workable solid loading. The best powder in terms of flowability (i.e., unannealed -45 µm powder) was selected to study the effect of each binder ingredient on feedstock rheological properties, evaluate powder/binder interaction, achieve the best binder formulation, and identify the highest solid loading (58 vol. %) of this powder. Furthermore, to design the debinding cycle (i.e., wick thermal debinding) and define the presintering temperature (i.e., 600ºC), the same powder with optimal binder formulation (i.e., 1 vol. % stearic acid as a surfactant, 2 vol. % ethylene-vinyl acetate as a thickening agent, 2 vol. % carnauba wax as a shrinking agent, and paraffin wax (balance) as the main carrier) was used to prepare the feedstock for injecting test specimens. Finally, to evaluate the effect of particle size and impurity level on the moldability, debindability, and sinterability of irregular iron powders, three powders, including -45 µm (325 mesh), -25 µm (500 mesh), and -10 µm (1200 mesh), were used. The results revealed that feedstocks prepared from these three powders could achieve suitable flowability. Furthermore, the density values, mechanical properties, and final composition of PIM parts produced from feedstock prepared from -10 µm powder confirm that this powder is a reasonable alternative for commercially available iron powders in PIM.

Date	12 Feb 2023
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Vincent Demers (Supervisor) & Vladimir Brailovski (Co-supervisor)