High-temperature oxidation and spalling behavior of incoloy 825

Incoloy-825-sheet specimens were exposed to four different atmospheres; steam, synthetic air, CO₂, and CO₂ diluted with argon. The duration of exposure was varied from 2 min to 100 hr in the temperature range of 600–1300°C. A comparison of the results in these four atmospheres showed the maximum weight gain in specimens exposed under steam, while the minumum value was obtained in specimens subjected to diluted CO₂. The alloy obeyed similar reaction kinetics while exposed to all the atmospheres under consideration. The overall domination of parabolic rates was observed at 800–1000°C. For still higher temperatures, a transition from the parabolic to the cubic rate law was observed. Thermal cycling did not show any appreciable effects on the reaction kinetics of the alloy when specimens were cycled between test temperatures and 500°C, and finally cooled to ambient temperature.