The oxidation of four oxide dispersion strengthened Ni-5Al-xSi-0.2Y2O3 (x = 1, 3, 5, 7 wt.%) alloys in air at 1100 °C

Highlights: • Silicon could promote the selective oxidation of Al. • Silicon exerted third-element effect and improved oxidation resistance significantly. • 5 wt.% Silicon improved spallation resistance of scales significantly. • Single and continuous α-alumina scales were formed on Ni-5Si-5Al-0.2Y₂O₃ alloys. - Abstract: The cyclic oxidation behavior of oxide dispersion strengthened Ni-xSi-5Al-0.2Y₂O₃ (with x = 1, 3, 5, 7 wt.%) superalloys was investigated at 1100 °C for 100 h. The alloys contained 5 wt.% silicon possessed the best oxidation resistance with the formation of continuous external α-alumina scales developed on the surface without any noticeable internal oxides. Therefore, the addition of silicon decreased the oxidation rate significantly and exerted the third-element effect by reducing the critical Al content needed for the transition from its internal to external oxidation. However, the excessive silicon content (7 wt.%) reduced the spallation resistance of oxide scales.