On the machinability of selective laser melted duplex stainless steels

Duplex stainless steels are well known for their high corrosion resistance, strength, and other useful characteristics, but mainly suffer from a lack of machinability. Selective laser melting, one of the additive manufacturing technologies was recently shown to be suitable for processing duplex stainless steels. However, the point-by-point consolidation of the powders and the complex thermal variations convert the biphasic ferrite plus austenite structures into predominantly ferritic structures. Ferritic stainless steels were traditionally known for better machinability. The research question, if selective laser melting route can be used first to convert duplex powders into ferritic printed forms to improve the machinability is answered here, through experimental investigations machining laser melted and wrought duplex stainless-steel specimens. Comparative assessments of the mechanisms of machining by means of metallographic and micro-hardness evaluations together with preliminary insights into torque and temperature variations proved the hypothesis that selective laser melting is a promising route to alleviate the machinability problems in duplex stainless-steel systems, while also allowing to reap all the benefits of additive manufacturing. This research not only considers a nonstandard material for laser melting but addresses the machinability limitations.