Effects of infiltration conditions on binder jet additively manufactured stainless steel infiltrated with bronze

The effects of infiltration conditions on the microstructure and mechanical properties of binder jet fabricated stainless steel 316 samples infiltrated with bronze (SS316 + bronze) were investigated through ultrasonic testing, optical and scanning electron microscope imaging, and mechanical testing. Infiltration environment, bronze infiltrant amount, and infiltration configuration were varied to determine their impacts on the porosity and mechanical properties of the fabricated samples. (Cr, Mo)₂N precipitates were observed in samples infiltrated in N₂-based environments, resulting in increased hardness and tensile strength compared to samples infiltrated in an Ar-based environment. Ultrasonic testing was performed, showing that the ultrasonic wave's attenuation was positively correlated with porosity and inversely correlated with ultimate tensile strength and elongation, while wave speed was inversely correlated with porosity and positively correlated with ultimate tensile strength and elongation. Samples fractured near regions that ultrasonic attenuation and wave speed showed indications of having higher porosity, demonstrating ultrasonic testing as a promising nondestructive evaluation technique for assessing microstructure and mechanical properties of binder jet metals.