Oxidation mechanism of the Inconel 601 alloy at high temperatures

The Inconel 601 alloy oxidation was performed in air, in the temperature range 1000–1150 °C, during 90 h. Kinetic results show that the parabolic behavior is always followed in this temperature range. The Arrhenius plot of the k p values shows two different activation energies. Between 1000 and 1050 °C the activation energy is E a1  = 160 ± 10 kJ/mol. In the 1050–1150 °C temperature range a higher value is calculated E a2  = 252 ± 20 kJ/mol. The E a2 value and the X‐ray diffraction (XRD) results and scanning electron microscope (SEM) energy dispersive X‐ray spectroscopy (EDS) examinations are in accordance with a scale growth mechanism limited by a growing Cr 2 O 3 scale acting as a diffusion barrier. In the 1000–1050 °C temperature range the activation energy is lower and the structural analyses show that the oxide scale is not only composed of Cr 2 O 3 . Then, the oxide scale is composed of titanium oxides (TiO 2 and Ti 2 Cr 7 O 17 ) and chromia mixed together. A doping effect of the chromia scale by titanium can be envisaged. Our results also show the presence of some Mn 1.5 Cr 1.5 O 4 at the external interface. This external subscale spalls off easily during cooling after the highest temperature oxidation tests. Nevertheless, XRD results and SEM–EDS observations show that the Cr 2 O 3 scale remains very adherent on the substrate and can give a good oxidation protection. This good adherence can be related to the presence of a low amount of aluminum in the Inconel 601 alloy composition.