New insights on the porous network created during solvent debinding of powder injection-molded (PIM) parts, and its influence on the thermal debinding efficiency

Abstract

Mn-Zn ferrite components were successfully produced using Powder Injection Molding (PIM) from a binder system (11.5 wt%) made of paraffin wax (PW), linear low density polyethylene (LLDPE) and stearic acid. Solvent debinding kinetics of the molded parts depended on n-hexane temperature, on immersion duration and on part’s geometry. The volume to surface ratio of the considered parts were comprised between 1.3 and 4.0. The primary binder (PW) removal created a porous network having a narrow average pores distribution centered on a diameter of about 50 nm. We highlighted by using Archimedes’ principle and mercury intrusion porosimetries that the parts achieved a maximal open porosity disregarding their volume to surface ratio, while it was still possible to remove additionnal PW. This maximal porosity (12.6 %) has proved to be the most relevant parameter for the definition of an optimal solvent debinding duration (∼15−20 h at 40 °C). Using this chemical debinding step, it was possible to reduce our thermal debinding duration by 62.5 % (80 h–30 h) while avoiding the occurrence of structural defects as cracking or deformations on the parts. The sintered PIM parts had a density of about 4.84 g/cm3 (94.9 % of relative density) and a magnetic saturation polarization of about 500 mT what is very similar to parts produced using the conventional fabrication techniques. These results should be useful to understand how to improve the production rate of ferrites fabricated by PIM technology.