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<p>Immersion or dipping remains a widely used technique by the investment casting industry for hardening mold shells due to its rapid reaction rate, operational simplicity, and high production efficiency. However, the uncontrollable nature of the reaction across the entire shell surface, combined with variability in the physicochemical properties of the hardening agent over time, poses challenges for process stability, environmental compliance, and sustainability. This study investigates the application of microfluidic spray technology as a method to regulate the hardening of sodium silicate shell molds. Shell specimens were cured by spraying a fine mist of aqueous boric acid solution at various concentrations, enabling controlled dosing based on processing requirements. Mechanical and technological properties were evaluated, and the fracture surfaces and gel film microstructures were characterized using TG/DSC, SEM, FT-IR, and XRD. Compared to the traditional immersion method, the microfluidic approach improved both green and fired strength—reaching 27.52&#xa0;MPa and 10.87&#xa0;MPa, respectively—representing increases of approximately 115% and 35.7%. The mist-cured shells also exhibited lower high-temperature deformation, slightly reduced gas permeability, and enhanced thermal cracking resistance, as indicated by a 50&#xa0;°C increase in the critical cracking temperature. These findings demonstrate that microfluidic technology offers an effective and controllable alternative for hardening sodium silicate shells in investment casting, with potential benefits in both process performance and environmental impact.</p>

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Evolution of Performance and Micro Structure of Sodium Silicate Shells Cured Through Spraying Mist of Boric Acid Aqueous Solution

  • 期刊论文

  • 发表日期：

    2025年11月14日

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  • Pengfei Li,
  • Chang Liu,
  • Zhijun Chen,
  • Dawei Yu,
  • Xiangdong Liu

摘要

Immersion or dipping remains a widely used technique by the investment casting industry for hardening mold shells due to its rapid reaction rate, operational simplicity, and high production efficiency. However, the uncontrollable nature of the reaction across the entire shell surface, combined with variability in the physicochemical properties of the hardening agent over time, poses challenges for process stability, environmental compliance, and sustainability. This study investigates the application of microfluidic spray technology as a method to regulate the hardening of sodium silicate shell molds. Shell specimens were cured by spraying a fine mist of aqueous boric acid solution at various concentrations, enabling controlled dosing based on processing requirements. Mechanical and technological properties were evaluated, and the fracture surfaces and gel film microstructures were characterized using TG/DSC, SEM, FT-IR, and XRD. Compared to the traditional immersion method, the microfluidic approach improved both green and fired strength—reaching 27.52 MPa and 10.87 MPa, respectively—representing increases of approximately 115% and 35.7%. The mist-cured shells also exhibited lower high-temperature deformation, slightly reduced gas permeability, and enhanced thermal cracking resistance, as indicated by a 50 °C increase in the critical cracking temperature. These findings demonstrate that microfluidic technology offers an effective and controllable alternative for hardening sodium silicate shells in investment casting, with potential benefits in both process performance and environmental impact.