Microstructure and properties of KNO₃- based water-soluble salt core strengthened by glass fiber

Abstract

The KNO3-based water-soluble salt core was prepared using 70%KNO3-30%KCl (mole fraction) as a matrix material and glass fiber as a reinforcing material by stirring casting method. The effects of different glass fiber contents on the bending strength, impact toughness, water solubility rate and hygroscopic rate of the water-soluble salt core were compared and analyzed. The scanning electron microscopy and energy spectrometer were used to analyze the microstructure characteristics of the water-soluble salt core strengthened by glass fiber. The results show that with the increase of glass fiber content, the bending strength and impact toughness of the salt core are increased, and the water solubility rate and moisture absorption rate are gradually decreased. When the mass fraction of glass fiber is 30%, the salt core has the largest bending strength of (38.85±0.61) MPa and impact toughness with (2.13±0.1) kJ/m2, and the water solubility rate is still as high as (476.5±12.0) g/(min·m2), and the moisture absorption rate is (0.085±0.007)%. The microanalysis shows that the glass fibers are evenly distributed among the matrix of KNO3-based water-soluble salt core, which significantly refines the KCl primary phase. The average grain size of KCl primary phase is reduced from 57.89 μm to 24.13 μm, which is the main strengthening mechanism of the salt core. The crack will deflect when encountering glass fibers during the crack propagation, and the fiber pull-out is also observed, which is the main toughening mechanism of the salt core.

Keywords

• stirring casting
• water-soluble salt core
• glass fiber
• strengthening and toughening mech-anism