Influence of powder type and binder saturation on binder jet 3D–printed and sintered Inconel 625 samples

Binder jet 3D printing combined with post-deposition sintering is a non-beam additive manufacturing (AM) method for the creation of complex 3-dimensional structures. Binder saturation and particle morphology are two important factors affecting the quality of printed parts. Here, we investigated the effects of binder saturation on dimension accuracy, porosity, microstructure, and microhardness of nickel-based alloy 625 samples made of differently atomized powders. Argon gas atomized (GA) and water atomized (WA) nickel-based alloy 625 powders were used to binder jet samples for a detailed comparative study. The optimal binder saturation for WA system is 60 to 70%, whereas for GA system the optimal is about 80%. Generally, GA samples achieved better overall quality than WA samples in terms of packing density, dimensional accuracy, sintered density, and microhardness. This difference is attributed mainly to the particle morphology including sphericity and roundness. The critical threshold for visible binder bleeding phenomenon in WA and GA systems is determined to be 120% and 140% binder saturation, respectively. Mechanisms for binder bleeding phenomenon at different saturation levels for WA and GA systems are discussed in detail. A pore evolution model is proposed to better understand the printing and sintering processes.