Oxidation characteristics of nickel based superalloys in steam

An improvement in the efficiency of land based gas turbines is sought by replacing air with steam for the internal cooling of hot gas path components. However, the degradation behavior and mechanisms associated with the interaction of superalloys with steam at high temperatures are unknown. This information is very crucial for the reliability as well as for useful life prediction of the gas turbine components. In this work, oxidation in steam has been studied for three nickel based superalloys commonly used in the gas turbines. These are IN 738, Inconel 617, and CMSX-4. The study was carried out at four different test temperatures in the range of 800 °C to 950 °C for times up to 1400 hours. The results indicated significantly different oxidation behavior in steam compared to air for all the alloys tested