Using fused filament fabrication to improve the tribocorrosion behaviour of 17-4 PH SS in comparison to other metal forming techniques

Fused filament fabrication (FFF) is one of the additive manufacturing processes which has gained more interest because of its simplicity and low-cost. This technology is similar to the conventional metal injection moulding (MIM) process, consisting of the feedstock preparation of metal powder and polymer binders, followed by layer-by-layer 3D printing (FFF) or injection (MIM) to create green parts and, finally, debinding and sintering. Moreover, both technologies provide near-dense parts. This work presents an in-depth study of the processing method's influence. The porosity, microstructure, hardness, corrosion, and tribocorrosion behaviour are compared for 17-4 PH SS samples processed from powder by additive manufacturing using FFF and MIM, as well as conventional powder metallurgy (PM) samples. MIM samples exhibited the highest macro and microhardness, while corrosion behaviour was similar for both MIM and FFF samples, but superior in comparison to conventional PM samples. However, the FFF-as fabricated samples displayed a significant improvement in tribocorrosion resistance that could be explained by the higher proportion of delta ferrite and retained austenite in their microstructure.