Additive manufacturing of Ti-6Al-4V alloy by metal fused filament fabrication (MF3): producing parts comparable to that of metal injection molding

This paper presents metal-fused filament fabrication (MF3) for manufacturing Ti-6Al-4V parts by 3D printing of green parts followed by debinding and sintering to obtain mechanical properties comparable to metal injection-molded (MIM) specimens. The current work discusses critical material and process aspects of the MF3 process that currently limits it from effective defect-free translation from 3D printed to sintering. We show successfully produced bound filament with 59 vol% of Ti-6Al-4V powder mixed with a polymeric binder system to print parts using MF3. The feedstock and filaments showed uniform powder dispersion and acceptable flowability necessary for consistent extrusion during MF3 printing, leading to defect-free parts. The green part density was 98.5 ± 0.6% relative to the density of the 59 vol% Ti-6Al-4V feedstock that resulted in successful debinding without slumping, no warpage, and layer delamination of the MF3 parts. A two-step debinding combining solvent and thermal extraction of polymer binder followed by sintering in partial vacuum resulted in almost isotropic shrinkage of ~ 14% in all directions. The sintered density of these parts was 94.2 ± 0.1%. The mechanical properties of the present MF3 processed Ti-6Al-4V alloy parts represent UTS of 875 ± 15 MPa and elongation of 17 ± 3%, which being 1.7% higher in UTS and 17.5% higher in elongation when compared to literature data for metal injection-molded parts.