Cyclic oxidation behavior of Al-Si coating on new γ′-strengthened cobalt-based superalloy: Experimental study and first-principles calculation

Highlights: • Al-Si coating was prepared on the new γ′-strengthened Co-based superalloy. • Cyclic oxidation resistance of Al coating was effectively improved by Si addition. • Role of Si in the enhanced cyclic oxidation resistance of the coating was revealed. The aluminide coatings with and without Si modification were prepared on the new γ′-strengthened cobalt-based superalloy using a pack cementation method. Cyclic oxidation of the coated Co-based superalloy was study at 1050 °C. The weight changes of Al coating and Al-Si coating were -4.28 mg/cm² after 248 cycles and -3.40 mg/cm² after 346 cycles, respectively. The cyclic oxidation resistance of the Al coating was effectively improved by Si modification. Based on the experimental study and the first-principles calculation, it is suggested that Si addition facilitated the formation of a protective Al₂O₃+SiO₂ film and reduced oxygen diffusion in the coating.