Effects of Al and Y elements on mechanical properties and LEB resistance of FeCrAl(Y) coatings prepared by HiPIMS

Abstract

This study explores the microstructural evolution, mechanical properties, and corrosion resistance of FeCrAl(Y) coatings deposited using high-power impulse magnetron sputtering (HiPIMS), focusing on the effects of Al content and Y addition. The coatings were comprehensively characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) to evaluate their grain structure and elemental distribution. Mechanical performance was assessed through nano-indentation, thermal shock, scratch-adhesion and friction-wear tests, while corrosion and irradiation resistance were investigated by liquid lead‑bismuth eutectic (LBE) exposure and heavy-ion irradiation tests. The results reveal that Y addition plays a crucial role in grain refinement, enhancing irradiation resistance, and promoting the diffusion of alloying elements under LBE exposure, thereby improving the coating's integrity under extreme conditions. Meanwhile, increasing Al content led to a smoother surface morphology (average roughness (R_a) decreasing from 4.5 to 2.6 nm) and higher hardness (rising from 9.1 to 11.2 GPa) due to solid-solution strengthening and grain refinement. However, excessive Al incorporation (>24.4 at.%) introduced brittleness, compromising thermal shock tolerance and wear resistance (decreasing from 6.5 × 10⁻⁶ to 2.5 × 10⁻⁶). A threshold Al content was identified as essential for forming a continuous and protective Al₂O₃ oxide layer, which effectively mitigates LBE infiltration. Coatings with Al content below 6.1 at.% failed to prevent deep LBE penetration, which could result in significant substrate degradation under long-term application. These findings underscore the necessity of optimizing Al content to achieve a balanced trade-off between mechanical properties and corrosion resistance. The study provides valuable insights into the development of FeCrAlY coatings for nuclear applications, particularly in next-generation lead-cooled fast reactor (LFR) cladding materials, where high-temperature stability, irradiation tolerance, and LBE compatibility are critical.