Study on Debinding and Sintering Conditions in Extrusion-Based Additive Manufacturing of 316L and 316L + Cu

Abstract

This study investigates the use of a methylcellulose binder in extrusion additive manufacturing of 316L as an alternative to common wax-based binders. Various quantities of copper (Cu) powder were also added in the paste composition to attempt to reduce the sintering temperature by promoting persistent liquid phase sintering. Debinding experiments were conducted under different temperatures and dwell times using argon (Ar), Ar/5%H2, and Ar/1%O2 atmospheres. Debinding reduced carbon (C) content to 0.032 wt.% by using a two-step debinding process of Ar/5%H2 and Ar/1%O2 thermal treatments. Using this debinding process, sintering was conducted at 1200 °C under Ar/5%H2 atmosphere with the presence of 0, 10, and 20 vol.% Cu in the paste. Microstructure, mechanical, and corrosion properties were studied. Cu additions allowed the improvement of the densification when sintering at 1200 °C was performed. A 20 vol.% Cu addition yielded 88% relative density after sintering for 10 h, while pure 316L powder sintered under the same conditions had 70%. Mechanical properties were inferior to fully dense stainless steel, but it is not clear if this is due to the Cu additions or insufficient densification.