NiCrBSi-CrB₂ composite powders and coatings, with varying CrB₂ mass fractions, were successfully prepared using spray granulation and high-velocity oxygen-fuel (HVOF) spraying. This study systematically investigated their hot corrosion behavior and underlying mechanisms in KCl-NaCl-Na₂SO₄ molten salt at 600 °C. The results showed that the composite powder consisted of γ-Ni, CrB₂, CrB, CrSi₂, Ni₂B, and Ni₃B phases. The phases within the coatings were similar to those in the powder, with the additional identification of Ni₂Si and Ni₃Si₂ phases in coatings containing 30% and 40% CrB₂. Crucially, the hot corrosion weight gain and kinetic constant of the coatings initially decreased and then increased with increasing CrB₂ content. The coating with 20% CrB₂ demonstrated optimal corrosion resistance, exhibiting the lowest corrosion weight gain (12.42 mg/cm²) and kinetic constant (0.80 mg²/(cm⁴·h)). The superior corrosion resistance is primarily attributed to grain refinement, which increases the short-range diffusion channels centered on grain boundaries and dislocations in the coating. The nano-crystalline and amorphous forms of Cr₂O₃ and SiO₂ oxide scale on the coated surface effectively hinder the rapid diffusion of corrosive media, thereby reducing the corrosion rate.

High-velocity oxygen-fuel spraying; NiCrBSi-CrB2 composite power and coating; High-temperature corrosion; Molten salts