Does selective shell printing advance binder jetting additive manufacturing?

Study examines binder deposition methods (bulk vs. selective printing) and sintering atmospheres (vacuum vs. H2) on binder jetted 316 L stainless steel components. The density of the H2-sintered specimens was found to be lower (up to 5%) compared to the vacuum-sintered parts with the final density of 99.7%. Grain size analysis indicated smaller grains in the H2-sintered parts (-26 mu m) compared to vacuum-sintered condition (-33 mu m) in the bound area which could be attributed to the presence of residual pores that impeded grain growth. The H2sintered specimens exhibited an elongation of 25% and an ultimate tensile strength (UTS) of 460 MPa, whereas the vacuum-sintered parts displayed an elongation of 70% and a UTS of 550 MPa. Fractography analysis using microscopy and micro-computed tomography revealed ductile fracture in the vacuum-sintered samples, while the H2-sintered parts exhibited a combination of brittle and ductile fracture due to remnant pores in the microstructure.