Experimental study and characterisation of 316L stainless steel parts fabricated with metal fused filament fabrication.

The 3D printing process of Fused Deposition Modelling (FDM) can be used for fabricating metal parts without the need of mold. Metal Material Extrusion uses metal-polymer composite filament in the 3D printer to extrude the green part, then a de-binding process for removing the polymer binder, and eventually, the sintering process under high temperatures for making a metallic part. A comprehensive research is conducted in which sintering parameters including heating rate, dwell time, and sintering atmospheres are varied for metal parts mechanical characteristics including tensile strength, ductility, and density. Moreover, sintering atmospheres including vacuum and argon are taken into consideration in this research study. The metal part is known as silver part which has exhibited a high mechanical strength of 540 MPa, a considerable density of 7.57 g/cm3, and a high hardness of 220 HV under a vacuum sintering atmosphere. Whereas the metal parts produced under argon atmosphere have shown comparatively low mechanical strength 424 MPa, density 7.1 g/cm3 and 177 HV. The results are compared with an industrial benchmark process where catalytic de-binding and sintering are used to achieve 500 MPa tensile strength, density 7.83 g/cm3, and 175 HV. Scanning Electron Microscopy reveals that grains are coarsened in a vacuum, and grains appear peeled off along with small pores in the boundaries. The industrial benchmark part has uniform and finer grains.