Study on Yttrium-Enhanced Anti-Oxidation and Adhesion Properties of Al2O3 Oxide Scale on AFA Alloy Under Low Oxygen Partial Pressure

This work investigated the effect of yttrium addition on the pre-oxidation behavior of Fe–25Ni–20Cr–4Al–1Nb–1Mn–1.5Si-based alloys at 1000 °C in a 4% H2 + 0.2% CH4 + Ar + 0.25% H2O atmosphere. The oxidation resistance and oxide scale adhesion were evaluated through cyclic oxidation tests and micro-scratch measurements. Results show that the Y-free alloy formed a discontinuous oxide layer, whereas all Y-containing alloys formed a continuous and dense Al2O3 scale. Incorporating 0.2 wt.% Y increased the work of adhesion by approximately 7 to 9 times relative to the Y-free sample, indicating a pronounced interfacial strengthening effect. The role of yttrium content and oxygen partial pressure in promoting alumina-scale formation was discussed based on thermodynamic considerations and microstructural evidence.