Oxidation behavior of the Ni-Cr-Al alloy at high temperatures

The effect of temperature on oxidation behavior of the Ni-base superalloy Ni10Cr5Al (wt%) in air was studied using the thermogravimetric analysis method. Microstructure of the sample surface after oxidation was determined by scanning electron microscopy, X-ray diffraction, and energy dispersive spectroscopy. The results indicate that the oxidation kinetics between 700 and 1 100 ℃ obeys parabolic law, and there exist two different parabolic rate constants at different stages during oxidation. The oxide scales mainly consist of NiO, NiAl₂O₄, Al₂O₃ and small amount of Cr₂O₃. Internal oxidation has also been found. The mass gain is much greater and the thickness of the internal oxide is much thicker at elevated temperatures; and accordingly the oxidation mechanism of the Ni-Cr-Al alloy with the Al₂O₃ scale has been analyzed.