Synergistic effects of Si and Ta on the high-temperature oxidation and corrosion behaviors of NiCrAlY coatings

This study focuses on the degradation mechanisms of a Si and Ta-modified NiCrAlY dual-phase coating under high-temperature oxidation and cyclic corrosion at 750 °C. During isothermal oxidation, the coating exhibits a characteristic two-stage behavior: initial outward growth of mixed oxides (Stage I), followed by oxide stratification and intensified interdiffusion within the coating (Stage II). In contrast, NaCl-induced cyclic corrosion triggers a self-sustaining chlorine cycle, accelerating the depletion of Cr-rich oxides and porous zone formation. Si and Ta alloying directly facilitates α-Al₂O₃ formation at reduced temperatures (750 °C) within shortened durations (8–16 h), significantly enhancing both isothermal oxidation resistance and cyclic corrosion performance. Microstructural analysis reveals corrosion-induced Si and Ta segregation at the coating-substrate interface, forming in situ diffusion barriers. These results demonstrate the distinct synergistic roles of Si and Ta co-modification in high-temperature oxidation and chlorine-induced corrosion, providing guidance for developing durable protective coatings in harsh environments.