Densification and coarsening of laser sintered green parts by microwave technique

Microwave sintering of SLS green parts made of 420 L stainless steel has been performed applying microwaves at the frequency of 2.45 GHz. The use of single mode and multi-mode microwave furnaces allowed to find the most suitable sintering conditions in absence of auxiliary microwave absorbers. In case the electric field intensity reaches a threshold value, able to trigger breakdown phenomena, sintering is rapidly achieved, but at the cost of homogeneity and process controllability. A lower electric field intensity allows, instead, to achieve complete sintering of the green parts in 10 to 20 minutes time, which results considerably shorter than current state of the art conventional sintering of SLS green parts. Comparison between microwave and conventionally sintered parts showed that the final product present a similar microstructure, with the presence of Cr-rich regions whose extension is a function of the microwave processing time.