## 2 Process Flow and Performance Indicators of Binder Jetting 3D Printing
### Process Flow and Pre-Printing Parameter Selection for Binder Jetting of Silicon Carbide Components  
The fabrication of SiC ceramic components via binder jetting additive manufacturing involves two critical processing stages: green part formation and densification post-processing. During the green part formation stage, SiC green bodies with predetermined geometries are fabricated in the printing chamber through precise control of the printing parameters. The mechanical strength of the green bodies at this stage primarily originates from temporary bonding networks formed by binder bridging effects, typically exhibiting high internal porosity that results in relatively low flexural strength. This porous structural characteristic renders the green bodies inadequate to meet the mechanical property requirements for structural ceramic applications. Consequently, appropriate densification post-processing is essential to transform the green bodies into final products possessing dense microstructures and satisfactory mechanical performance. Figure 4 demonstrates the step-by-step process for fabricating dense Si-SiC composite components through binder jetting 3D printing combined with liquid silicon infiltration (LSI) and phenolic resin impregnation and pyrolysis (PRIP) post-treatment. Initially, green parts with porous structures are fabricated using binder jetting 3D printing equipment (as shown in Figure 4a). Subsequently, the green parts are placed in a vacuum device for phenolic resin impregnation, allowing the resin to uniformly infiltrate the pores of the SiC green parts, resulting in impregnated parts (as shown in Figure 4b). Furthermore, the impregnated parts undergo curing treatment at 190 \({}^{\circ}\)C (as shown in Figure 4c), during which the phenolic resin undergoes polycondensation to form a three-dimensionally crosslinked stable structure, preventing part collapse during pyrolysis while maintaining the porous structure for subsequent LSI. The cured parts are then subjected to pyrolysis at 1000 \({}^{\circ}\)C in an argon atmosphere (as shown in Figure 4d), where the phenolic resin within the pores of the cured parts thermally decomposes to form a continuous carbon scaffold, serving as a reactive precursor for subsequent LSI. The argon atmosphere effectively prevents carbon loss due to oxidation during pyrolysis and controls the pyrolysis rate. Finally, the carbonized parts undergo LSI at 1500 \({}^{\circ}\)C under vacuum, where the liquid silicon reacts with the carbon precursor in the pores of the carbonized parts to form SiC structures, gradually filling the component's pores (as shown in Figure 4e). After LSI, a small amount of residual silicon remains within the component, forming dense Si-SiC composite parts. The particle size of the SiC powder and the binder system constitute two fundamental factors in the printing process, making their appropriate selection prior to printing critically important. Regarding powder particle size, current BJ 3D printers employed in practical production universally adopt a uniform layer thickness slicing strategy, maintaining consistent thickness across all powder layers. Existing studies have reported on the spreading and flow characteristics of layers with a thickness of three times the particle size [32] and two times the particle size [33], yet there is no consensus on the optimal relationship between layer thickness and particle size. However, it is important to note that the layer thickness should not be less than the maximum particle size of the powder [34] to meet the basic requirements for powder spreading and printing resolution. Moreover, while smaller powder particle sizes theoretically enable finer surface details of printed components through reduced layer thickness settings and corresponding binder jetting volume adjustments, decreasing particle size simultaneously induces powder agglomeration during spreading and other issues. When the powder particle size falls below 5 \(\upmu\)m, spreading defects can significantly compromise printing quality [23].