Experimental Validation and CALPHAD Modeling of Al–Si Coatings Under Oxidizing and Corrosive Conditions

ABSTRACT Al–Si coatings were developed on AISI 410 by pack cementation to study high‐temperature oxidation and corrosion response. The coating has bilayer structure of thickness 52.42 µm, consisting an outer Al–Si‐rich zone of 13.12 µm. SEM/EDS and XRD confirmed the presence of Al 3 FeSi with AlNi₂Si, Cr₃Si, and AlFe. Adhesion testing revealed a critical load of 20 N, indicating good coating adherence. Isothermal oxidation at 1100°C for 12–24 h indicates mass gains, reaching 0.23 mg/cm 2 at 20 h, followed by a slight decrease (0.218 mg/cm 2 at 24 h) due to oxide spallation. The degree of spallation increased from 33.1% at 12 h to 43.7% at 16 h, stabilizing near 41%–42% at longer exposures. Oxide scale characterization revealed the presence of Al₂O₃, Al₂SiO₅, Fe₂SiO₄, and Cr₂SiO₄. Surface roughness (Ra) increased from 1.03 µm to a maximum of 4.18 µm at 20 h, confirming oxide scale thickening. Hot corrosion tests in a Na₂SO₄–NaCl (1:1) environment at 1100°C confirmed the lower mass gain of coated sample due to the formation of protective SiO₂ and Al₂SiO₅. Thermodynamic predictions supported the experimental observations, identifying stable silicate and alumina as key protective products.