|About this Abstract
||MS&T23: Materials Science & Technology
||High Temperature Corrosion and Degradation of Structural Materials
||Effect of Temperature and Impurities on the Oxidation Behavior of Ni-based Alloys in Hot CO2-rich Gases
||Richard P. Oleksak, Joseph H. Tylczak, Lucas Teeter, Casey S. Carney, Ömer N. Doğan
|On-Site Speaker (Planned)
||Richard P. Oleksak
Several Ni-based superalloys were exposed to gas compositions and temperatures intended to simulate the hot portions of direct-fired supercritical CO2 power cycles. The alloys were tested in 95%CO2-4%H2O-1%O2, with and without 0.1% SO2, at a pressure of 1 bar and temperatures ranging from 600-800°C for up to 2500h. In the absence of SO2, the alloys performed well, forming thin chromia scales at all temperatures. Additions of SO2 had little influence at temperatures ≥750°C but significantly increased corrosion for several alloys at 600°C and 700°C. The increased corrosion was associated with sulfate formation at 600°C and internal sulfide formation at 700°C. At higher temperatures (≥750°C), sulfates were unstable and sufficient diffusion in the alloy prevented severe Cr depletion, thereby preventing formation of low-melting temperature nickel sulfide compounds. The results suggest caution is needed when using Ni-based alloys in CO2-rich environments if sulfur impurities are expected.