## 2 Process Flow and Performance Indicators of Binder Jetting 3D Printing
### Key Parameters Affecting Formation Quality
The strength of the final components is predominantly determined by densification processes during post-treatment (e.g., sintering, LSI, etc.) of the green parts, yet the state of the printed powder bed equally exerts a non-negligible influence on the ultimate component quality. A uniform and dense powder bed typically indicates more homogeneous pore distribution and material arrangement within the green parts. Green parts with non-uniform porosity may induce a series of critical issues affecting final component quality during post-densification, such as preferential shrinkage in high-porosity regions generating internal stresses and dimensional deformations during sintering or selective melt infiltration leading to incomplete reactions and consequent fluctuations in Si/SiC content in the final components during LSI. Therefore, precise regulation of the powder bed state constitutes an indispensable aspect for enhancing final component quality. Additionally, the high chemical inertness and thermal stability of SiC materials make the choice of binder crucial. Differences in bonding performance between the binder and SiC powder can affect the density during the sintering process, which in turn influences the strength of the formed components. However, adding the curing agent to the powder bed in advance may cause premature reactions or moisture absorption in the powder, affecting the quality of the powder bed and printing accuracy. Therefore, developing binders that react directly with SiC is key to solving such issues. While macroscopic mechanical properties provide a comprehensive assessment of material strength and offer a general indication of internal defects, they are insufficient to reveal the critical microscopic mechanisms that govern long-term material reliability. Internal defect detection enables the identification of early-stage damage that cannot be captured through macroscopic mechanical testing-damage which, in high-precision applications, may originate from micron-scale flaws and lead to premature component failure--thus significantly reducing safety risks. Internal defects (such as voids, cracks, and regions of incomplete fusion) significantly affect the long-term performance of the material. Internal defects may lead to stress concentration, reducing the material's fatigue life and impact resistance, and even causing brittle fracture or premature failure under dynamic or complex loads. Furthermore, internal defects may further propagate under environmental conditions such as repeated loading, thermal cycling, or corrosion, ultimately leading to premature material failure. Therefore, detection of internal defects is crucial for studying the failure mechanisms of components and predicting their service life, while also providing important feedback for process optimization and formation quality control. When 3D printed objects with poor mechanical properties are applied in practical fields, many potential issues may arise. For example, parts with insufficient strength may easily break or undergo plastic deformation when subjected to external forces, especially in high-load or high-stress environments. This situation may lead to component failure, affecting overall structural stability and safety. Parts with poor hardness are prone to wear during friction or long-term use, especially when used as wear components (such as gears, bearings, etc. ), greatly reducing their durability and service life. Parts with poor impact resistance are prone to brittle fracture under sudden impacts or high loads, creating safety hazards. To avoid potential problems caused by poor mechanical properties, optimizing the printing process to obtain high-quality green bodies is the foundation for enhancing the mechanical strength of printed parts. Additionally, improving quality inspection techniques for green bodies and enhancing the density and strength of materials through post-processing techniques (such as heat treatment, sintering, or adding composite materials) for lower-quality green bodies are important.