High strength brown parts produced by fast microwave-assisted debinding

The binder removal from 430L-steel MIM parts was performed in a two-step procedure using chemical and thermal debinding. During the first step, almost 80% of the binder is removed and a porous structure is created, which then favours the subsequent step. The second step was performed in a multi-mode microwave applicator, at 2.45 GHz ISM frequency. Numerical simulation allowed to optimise the microwave applicator loading conditions, in terms of heating homogeneity and efficiency. Experimental validation confirmed that using microwaves it is possible to reduce conventional debinding times by a factor of 3, and that the resulting brown parts possess a 4 times higher compressive strength. This phenomenon can be ascribed to local over-heating of the regions surrounding neighbouring metal particles, triggered by the high frequency electric field. This promotes the formation of necks among the particles, leading to pre-sintering, despite the overall measured samples temperature, which never exceeded 600°C.