Abstract
The alloys required for fossil power plants are altered from stainless steel that has been used below 600 °C to Ni-based alloy that can operate over 700 °C for advanced ultra super critical (A-USC) steam turbine. The IN 740 alloy is proposed for improved rupture strength and corrosion resistance at high temperature. However, previous studies with experiments and simulations on stable phases at over 700 °C have indicated the formation of the eta phase with the wasting of the gamma prime phase, which is the most important reinforced phase in precipitation hardened Ni alloys. This results in the formation of precipitation free zones to decrease the strength. LESS 1 alloy designed through some modifications of IN 740 was suggested in this study. LESS 1 showed the phase stability more than IN 740 due to the optimum composition of Cr, Mo, Ti and Al. The experimental results established that a needle-shaped eta phase was formed in the grain boundary and it grew to intra-grain, and a precipitation free zone was also observed in IN 740, but these defects were entirely controlled in LESS 1.
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Youn, J.I., Shin, Y.K., Kang, B.I., Kim, Y.J., Suk, J.I., Ryu, S.H. (2014). Study on Phase Stability of New Ni Based Superalloy Less 1 Designed to Low the ETA and Sigma Phase Fraction at 700 °C. In: Energy Materials 2014. Springer, Cham. https://doi.org/10.1007/978-3-319-48765-6_15
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DOI: https://doi.org/10.1007/978-3-319-48765-6_15
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-48598-0
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