Interface-Engineered Aluminide Coatings for Enhanced X-ray Shielding of Ni-Based Superalloys: Effect of Si and Co Additions

Abstract This research represents the first comprehensive study—combining experimental analysis and computational modeling—to demonstrate the protective performance of Si- and Co-enhanced Ni-based aluminide coatings against low-energy X-ray radiation. These coatings were deposited onto INC-738 superalloy substrates using a low-temperature powder pack cementation method. The aluminizing pack consisted of aluminum (Al), alumina (Al₂O₃), and ammonium chloride (NH₄Cl), and the samples were processed at 800 °C for 4 h under open-air conditions. The study systematically investigates how the addition of Si and Co influences the coatings’ growth behavior, microstructural evolution, and hardness. Microstructural analysis was performed using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), while phase composition was analyzed through X-ray diffraction (XRD). The coating layers were mainly composed of Ni 2 Al 3 , with some NiAl 3 and AlCr 2 detected. Radiation-shielding capabilities were assessed through both experimental data and simulation models (Phy-X and XCOM), focusing on key attenuation parameters such as the linear attenuation coefficient (µ), mass attenuation coefficient (µ/ρ), half-value layer (HVL), mean free path (MFP), tenth-value layer (TVL), effective atomic number ( Z eff ), transmission factor (TF), and radiation protection efficiency (RPE). Of the coatings examined—Al, AlSi, and AlSiCo—the AlSiCo sample consistently demonstrated the highest efficiency in reducing low-energy X-ray photon penetration. These findings were further supported by simulation results, which likewise demonstrated strong consistency in terms of neutron removal cross section (∑R), electrical conductivity ( C eff ), and the mass stopping power for alpha and proton particles. A comprehensive assessment of the coatings’ compositional features, microstructural characteristics, and radiation-shielding performance highlights the markedly superior attenuation capability of the AlSiCo-coated sample. Overall, the results position AlSiCo as a highly promising lightweight, high-efficiency radiation-shielding material suitable for advanced nuclear and aerospace applications.