Grain growth and oxidation resistance of Fe_2.5Ni_2.5CrAl multi-principal elements alloy at high temperature

Grain growth and oxidation resistance are critical factors affecting the high-temperature performance of Fe_2.5Ni_2.5CrAl multi-principal elements alloys (MPEAs), which remains underexplored till now. This work investigated the grain growth and oxidation kinetics in air at 800, 900 and 1000 °C, and the oxide compositions at different exposure temperatures have been examined. The Fe_2.5Ni_2.5CrAl MPEA displayed initial transient oxidation, followed by of parabolic growth of the oxide. The oxidation rate was measured as 0.0017 ± 0.0001 and 0.046 ±0.0001mg²/cm⁴/h at 800 °C and 900 °C, respectively. The oxidation at 1000 °C had three stages, the oxidation rate shows a slight decrease as the oxidation proceeds, and the average value was 0.048 ±0.0001mg²/cm⁴/h. The Fe_2.5Ni_2.5CrAl MPEA exhibits promising oxidation resistance compared with commercial stainless steel and reported alloys. After oxidation at 800 and 900 °C, some oxide particles were found on the surface. Spalling occurred after oxidation at 1000 °C. Analysis of oxidation products showed that a combination of Al₂O₃ and Cr₂O₃ formed on the surface at 800 °C. As the oxidation temperature increased to 900 and 1000 °C, the formation of (Fe, Cr) oxides appeared in the oxide scale and mixed oxidation products of Al₂O₃,Cr₂O₃ and (Fe, Cr) oxides formed on the surface. An outer protective scale, which was composed of Cr₂O₃, acted as a barrier to prevent further oxidation inside the substrate. Thus, Fe_2.5Ni_2.5CrAl MPEAs are suitable for high temperature structural material applications.