Oxidation resistance and mechanical properties of experimental low coefficient of thermal expansion (CTE) Ni-base alloys

Energy generation systems must operate at higher temperatures and pressures in order to achieve increased efficiency. This may require the utilization of high temperature, high strength Ni-base alloys. However, the high thermal expansion coefficients (CTE) of commercially available Ni-base alloys relative to low cost ferritic steels may make it difficult to employ Ni-base alloys in hot sections. Utilizing prior work by Yamamoto et al. [In: Materials for advanced power engineering—2002. Proceedings of the seventh Leige conference; September 30–October 3, 2002. Energy and technology, Volume 21. Forschungszentium Julich Gmbh Inst. Fur Werkstoffe und Verfahren der Energietechnik; 2002] and the Thermo-Calc phase prediction software, a series of Ni-based alloys were developed at the National Energy Technology Laboratory based on the composition range of Ni–(18-25)Mo–(8-15)Cr–1Ti–0.5Mn, with CTEs similar to ferritic steels. The oxidation behavior was measured at 800∘C in moist air. The tensile properties were measured at 25 and 750∘C after aging at 750∘C for upwards of 1000 h. The results were compared to Haynes 230 and Crofer 22 APU.