Pre-sintered mim brown parts obtained by rapid microwave-assisted binder removal

Microwave assisted thermal debinding of parts obtained by Metal Injection Moulding (MIM) was studied using Design of Experiment techniques to reduce the number of virtual experiments needed to gather information regarding binder removal. The optimization, in terms of speed, heating homogeneity and energy efficiency of the early stages of this process in an existing 2-feeds multimode applicator operating at 2.45 GHz has been reached with numerical simulation used to perform the virtual experiments. The obtained model was used to determine the optimum debinding conditions, which were experimentally tested in a laboratory multimode applicator. Sample characterization, before and after sintering, in terms of strength and final density, with respect to an equivalent industrial production, was used to assess the optimized process. A process time reduction of more than 6 times was achieved. In case of MIM parts made of 430L steel, material not prone to high temperature oxidation, the preferential microwave absorption by the metallic powders resulted also in a pre-sintering treatment which improves the brown parts strength and favors their handling during the subsequent sintering stage.