Microstructure, Mechanical and Corrosion Properties of 17-4PH Stainless Steels Manufactured via Metal Material Extrusion Additive Manufacturing

Metal Material Extrusion Additive Manufacturing (M-MEAM) is a building process by extruding filaments composed of metal powders and polymer binder layer-by-layer. M-MEAM has been getting spotlighted because of its superior economic feasibility and accessibility than other metal AMs. In this study, 17-4PH steels were manufactured by M-MEAM with post sintering process. Heat treatments (HT) were also applied to MEAM 17-4PH sintered parts and the microstructures, mechanical properties, and corrosion properties were investigated according to HT conditions. Microstructure observation demonstrated that the size and distributions of precipitates, such as nano-size NbC and Cu-rich precipitates, were altered by HT conditions. The HT improved tensile properties (tensile strength: 1.35 GPa, yield strength: 1.11 GPa, elongation: 7.8%) which were comparable to ASTM standard and the corrosion properties were also improved. The fracture and corrosion mechanisms of 17-4PH alloy manufactured by M-MEAM was also discussed in relation with the microstructures.