Understanding Binder Influence on Densification in Binder Jet via Hot Isostatic Pressing

Binder Jet Additive Manufacturing has emerged as a versatile and high-throughput technique for producing complex metallic components, yet challenges in achieving full densification and eliminating process-induced defects continue to limit its industrial application. This study investigates how binder chemistry, sintering dynamics, and post-processing treatments collectively influence densification, microstructural evolution, and mechanical performance in binder-jetted AISI M2 high-speed tool steel. Two commercial binder systems AquaFuse and FluidFuse were examined to evaluate their effects on powder–binder interaction, sintering behavior, and microstructural uniformity. Green parts were sintered at 1270–1300°C for 60–120 minutes, followed by distinct cooling routes (furnace, air, and water) and Hot Isostatic Pressing (1150°C, 100 MPa, 3 h). Across all conditions, HIP significantly improved densification, increasing relative density from ~93–95% to over 99%, with compressive strength gains up to ~45%. Microstructural analysis revealed that HIP promoted fragmentation, spheroidization, and redistribution of M₂C, MC, and M₆C carbides, yielding a refined and homogeneous dispersion that enhanced strength and mitigated defects. Among the evaluated binders, FluidFuse demonstrated superior performance, producing finer carbide morphology and more uniform particle packing. The optimized condition FluidFuse binder, 1270°C sintering for 60 min, furnace cooling, followed by HIP achieved ~99.7% density, ~855 HV hardness, and ~4130 MPa compressive strength with 24% strain retention. Binder-dependent trade-offs were also identified: localized micro-porosity in some FluidFuse cases and carbide coarsening at higher sintering temperatures reduced ductility. CALPHAD modeling was employed to predict carbide transformations and define an optimal sintering window. This talk will also discuss the comparative evaluation with Selective Laser Melting and Directed Energy Deposition demonstrated that binder jetting coupled with HIP offers a cost-effective and scalable route to near-fully dense, high-strength tool steels. This work establishes a process-structure-property framework for binder selection and HIP-assisted densification, advancing defect mitigation strategies in next-generation additive manufacturing.