Microstructure evolution for isothermal sintering of binder jet 3D printed alloy 625 above and below the solidus temperature

Supersolidus liquid phase sintering of water-atomized low-alloy steel in binder jetting additive manufacturing

“…Several emerging studies have demonstrated the potential to further improve the sintered density of BJAM parts (Inconel [ 20 , 21 ], tool steels [ 14 , 15 , 22 ], or shape memory alloy [ 23 ]) via supersolidus liquid phase sintering (SLPS). Densification and distortion during SLPS depend on the resistance obtained by the structure to viscous deformation, which is related to various metallurgical factors such as grain size, neck size, packing density, and liquid volume fraction [ 24 ].…”

Site-specific control of alloy property through binder jet 3D printing

“…On the other hand, BJ3DP consolidates materials via sintering, which is a solid-state process conducted at a much slower heating and cooling rate, thus generating less residual stress and avoiding hot cracking altogether. On top of that, there is no concern for the laser absorption by different powders in BJ3DP [42,43], enabling the process to be widely applicable to most powdered materials, including steel [44][45][46][47][48], titanium alloy [49][50][51], nickel-based superalloy [52][53][54], copper alloy [55,56], refractory alloy [57,58], ceramics [59][60][61], and metal matrix composite [62,63], etc. Additionally, the densification by sintering produces distinctively different microstructural evolution as compared to PBF or DED process, resulting in different mechanical properties.…”

“…Of the many factors that affect sintered density, the peak temperature is the most influential one, as showcased in several works investigating sintering parameters on different alloys [45,53]. However, other factors such as sintering duration, furnace environment, heating rate, alloy composition, green density, powder size and distribution also play a role in determining the sintered quality.…”

“…For example, adopting a broader range of powder size distribution to increase the green density would improve the resulted density after sintering [52]. Depending on the slight change of alloy composition, the peak temperature and duration of sintering may need to be reconsidered to avoid abnormal grain growth at final stage and adjust the amount of other hightemperature phases that may be retained at room temperature [53,75]. Additionally, there are some factors that are inherently stochastic to a certain extent, making the sintering condition difficult to be maintained consistently, such as powder characteristics, furnace environment, and green density after different packing procedures.…”