High-Temperature Corrosion of Chromia-Forming Ni-Based Alloys in CO2 Containing Impurities

Abstract

Future technologies require structural materials resistant to environmental degradation in high temperature CO 2 -rich environments. Herein we exposed several commercially available 263, 282, 617, 625, 740H) to atmospheric pressures gases intended to simulate the compositions expected in future direct-red supercritical CO 2 power cycles. The alloys were exposed to 95% CO 2 + 4% H 2 O + 1% O 2 and the same gas containing 0.1% SO 2 at temperatures of 600, 650, 700, 750, and 800°C for 2500 h. With minor exceptions, chromia scales formed on all alloys at all temperatures in the SO 2 -free gas, yielding parabolic growth rates that followed a clear Arrhenius temperature-dependence. Behavior in the SO 2 -containing gas was more complex. Generally, the alloys performed well at temperatures of 650, 750, and 800°C. While some alloys further performed relatively well across the whole temperature range, several of the alloys experienced chromia failure and higher oxidation rates at temperatures of 600 and 700°C. Deviation from protective behavior was associated with internal sul de formation and, additionally for the case of 600°C, external sulfate formation. The thermodynamic and kinetic factors in uencing the accelerated corrosion in the presence of sulfur are discussed. The results suggest that caution is required when assessing compatibility of Ni-based alloys for CO 2 -based systems when sulfurbased impurities are expected.

Corrosion Behaviour of Ni-based Alloys 230, 617 and 601 in CO2 Gas at 750 and 850 °C

“…8 The corrosion resistance of some Ni-based chromia forming commercial alloys in CO 2 -rich gases was also investigated and found to be varied with the alloys and impurities in the gas. 12,13 This work investigated corrosion behaviour of three high Cr containing (⩾22 wt%) Ni-base alloys (230, 617, 601) in CO 2 gas at 750 and 850 °C for up to 500 h by examining weight gain kinetics, characterizing the reaction products and understanding the corrosion mechanisms. It is expected that these results can provide a better understanding of the effects of alloy compositions and temperatures on CO 2 corrosion, providing a better materials selection to resist CO 2 corrosion at high temperatures.…”