The combined influence of elevated pre-sintering and subsequent bronze infiltration on the microstructures and mechanical properties of 420 stainless steel additively manufactured via binder jet printing

In the present study, 420 stainless steel parts with different porosities in the range of ∼6 % to ∼ 54 % were fabricated via the binder jet printing technology followed by pre-sintering between 1000 and 1400 °C. Initially, during the pre-sintering at 1150 °C, evidences of neck formation between the 420 stainless steel particles were observed. Later, when pre-sintered at higher temperature between 1300 and 1350 °C, the parts were found with 3D interconnected open-porous channels. Finally, pre-sintering at 1400 °C led to closed/isolated pores within the parts. Subsequent bronze infiltration into the as-built (without pre-sintering) and pre-sintered (<1350 °C) 420 stainless steel parts with open porous channels were carried out successfully and their corresponding microstructures and mechanical properties were presented and discussed. Relatively more uniform bronze infiltration was able to be achieved for the parts pre-sintered between 1300 and 1350 °C due to the presence of 3D interconnected open-porous channels. When compared to the as-built parts, the combination of pre-sintering at 1350 °C and subsequent bronze infiltration led to a significant increase in the tensile properties exhibiting a maximum tensile yield strength and ultimate tensile strength of ∼ 647 and ∼ 1053 MPa, respectively. The fractured surfaces indicated a typical brittle mode of fracture with cleavages on the 420 stainless steel matrix whereas dimples and ridges were observed within the bronze phase.