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<p>This study investigates the hot corrosion behavior of CoCrFeNiSiₓ high-entropy alloys (x = 0.1, 0.3, 0.5) in a molten salt (75 wt% Na<sub>2</sub>SO<sub>4</sub>+25 wt% NaCl) at 900&#xa0;°C. Increasing the Si content refines the microstructure from coarse dendrites to equiaxed and columnar grains. At x = 0.5, a significant amount of face-centered cubic (FCC) structure phase and minor body-centered cubic (BCC) structure phase precipitate, indicating Si promotes element segregation and secondary phase formation. The Si = 0.5 alloy possesses the best resistance, exhibiting the lowest mass gain (21.5&#xa0;mg/cm<sup>2</sup>) and thinnest corrosion layer (~ 100&#xa0;μm) after 100&#xa0;h. Its corrosion rate decelerated significantly in the later stage, suggesting the formation of a protective surface scale. Analysis shows that Si addition substantially alters the intermediate corrosion layer composition. At Si = 0.5, a dense, continuous SiO<sub>2</sub> layer forms, acting as an effective barrier against sulfur and chlorine penetration and suppressing internal sulfidation. The outer layer consists mainly of spinel oxides and sodium-containing compounds (e.g., Na<sub>4</sub>Fe<sub>2</sub>O<sub>5</sub>). Silicon suppresses the formation of detrimental sodium salt oxides, thereby improving the scale’s density and protectiveness. In conclusion, silicon enhances the molten salt corrosion resistance of CoCrFeNiSiₓ HEAs by facilitating the formation of a protective SiO<sub>2</sub> layer, providing valuable support for their potential application in high-temperature corrosive environments.</p> Graphical abstract <p></p>

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The Effect of Non-metallic Si Content on the Corrosion Resistance of CoCrFeNiSiX High-Entropy Alloy in Molten Salt at 900 °C

  • 期刊论文

  • 发表日期：

    2026年3月20日

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  • Lei Wang,
  • Wenyu Tang,
  • Xuancheng He,
  • Qing Dong,
  • Yuhang Guo,
  • Ye Cheng,
  • Weiguo Yang

摘要

This study investigates the hot corrosion behavior of CoCrFeNiSiₓ high-entropy alloys (x = 0.1, 0.3, 0.5) in a molten salt (75 wt% Na2SO4+25 wt% NaCl) at 900 °C. Increasing the Si content refines the microstructure from coarse dendrites to equiaxed and columnar grains. At x = 0.5, a significant amount of face-centered cubic (FCC) structure phase and minor body-centered cubic (BCC) structure phase precipitate, indicating Si promotes element segregation and secondary phase formation. The Si = 0.5 alloy possesses the best resistance, exhibiting the lowest mass gain (21.5 mg/cm2) and thinnest corrosion layer (~ 100 μm) after 100 h. Its corrosion rate decelerated significantly in the later stage, suggesting the formation of a protective surface scale. Analysis shows that Si addition substantially alters the intermediate corrosion layer composition. At Si = 0.5, a dense, continuous SiO2 layer forms, acting as an effective barrier against sulfur and chlorine penetration and suppressing internal sulfidation. The outer layer consists mainly of spinel oxides and sodium-containing compounds (e.g., Na4Fe2O5). Silicon suppresses the formation of detrimental sodium salt oxides, thereby improving the scale’s density and protectiveness. In conclusion, silicon enhances the molten salt corrosion resistance of CoCrFeNiSiₓ HEAs by facilitating the formation of a protective SiO2 layer, providing valuable support for their potential application in high-temperature corrosive environments.

Graphical abstract