Studies of rapid microwave sintering of green parts

This paper regards the application of microwave for the sintering of green parts produced by selective laser sintering (SLS). Heating tests were performed on 420L stainless steel cylindrical (20 mm diameter; 20 mm height). The parameters of the electromagnetic field distribution during microwave sintering of the specimens were optimized for the heating treatments. The dates obtained from preliminary tests were used to carry out further heating treatments. This paper shows the possibility of achieving rapid consolidation in single mode and multimode applicators operating at 2.45 GHz, in less than 20 minutes. This phenomenon is confirmed by a micro-scale numerical modelling of the distribution of the electromagnetic field around the metal particles that evidence a favourable necking stage promoted by local electric field concentration among the spherical particles. The consolidated parts, however, depending on the microwave heating conditions, can present sensitisation due to the formation of chromium carbides, favoured by the C abundance provided by the decomposing organic binder.