Insights into the oxidation behavior of Ni–25Cr–10Fe–xSi (x = 1, 2, 3, 4 wt%) alloys at 1000°C in ambient air

Abstract

AbstractThe isothermal oxidation behavior of Ni–25Cr–10Fe–xSi (x = 1, 2, 3, 4 wt%) alloys at 1000°C in ambient air was investigated. The thermodynamics and kinetics of the oxidation behavior were analyzed using scanning electron microscopy with energy‐dispersive X‐ray spectroscopy, Raman spectroscopy, and the Thermo‐Calc software with the TTNI8 database. The weight gain per unit area of the four alloys showed a parabolic relationship with the oxidation time. The weight gain of the oxides decreased with the addition of larger amounts of Si from 1 to 3 wt%; however, this trend was lost when excessive addition of Si (4 wt% Si) was added. A sufficient amount of discontinuously distributed SiO2 precipitates resulted in better oxidation resistance and adhesion properties than continuous SiO2 layers. The spallation resistance of the oxide scales is believed to be mainly dependent on the distribution of the SiO2 layer rather than the content of SiO2; 3 wt% is a reasonable reference value for Si addition for improving the oxidation resistance of Ni–25Cr–10Fe alloys.