Atmosphere-controlled heat treatment of low-cost high-strength fused filament fabricated 316 L stainless steel

Fused filament fabrication (FFF) offers a safer, lower-cost route to metal additive manufacturing (AM) than laser powder bed fusion (LPBF), using polymer-bound metal filaments that avoid loose powder. However, the properties of FFF parts depend strongly on post-sintering heat treatment, and the role of the treatment atmosphere has not been systematically studied. This work examines heat treatments at 800, 950, and 1100 °C in air, argon, and vacuum on the mechanical, microstructural, and tribological behaviour of FFF 316 L stainless steel. As-sintered and heat-treated samples were characterised by tensile testing, Vickers microhardness, dry reciprocating wear testing, optical and scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). One-way ANOVA confirmed significant differences (p < 0.001) across atmospheres and temperatures. Air treatment at 1100 °C gave the highest strength and hardness, approaching LPBF values, but reduced ductility linked to surface oxidation. Argon treatment offered the best balance of strength, toughness, and wear resistance while retaining a stable austenitic structure, whereas vacuum treatment preserved composition and phase stability but gave lower hardness. Overall, atmosphere selection critically governs FFF 316 L performance, with argon the most reliable choice, establishing FFF as a viable low-cost alternative to LPBF for functional stainless-steel components.