Recent Advances in Heat-resistant Structural Material Development with Laves Phases at Oak Ridge National Laboratory

This presentation provides an overview of recent developmental efforts at Oak Ridge National Laboratory (ORNL) on heat-resistant ferrous materials with Laves-phase strengthening for fossil-fired energy conversion systems. Laves phases are attractive as second-phase strengtheners in Fe-base alloys, including ferritic and austenitic stainless steels, since most of the Fe-rich Laves phases (Fe₂M intermetallic compounds, M: Nb, Mo, W, Zr, Ti, etc.) are thermodynamically equilibrated with BCC- or FCC-Fe solid solution. Because of the characteristics, relatively easy control of second-phase dispersion is expected through a traditional “solution-and-annealing” process combined with proper alloying additions. The thermal stability of the Laves phase precipitates at elevated temperature was found to be controlled and improved through combinations of multiple Laves-phase forming elements, which guides the alloy design and provides effective strengthening of high-temperature structural materials for the extended periods of time. Laves-phase precipitation in Fe-base matrix can be expected in relatively large composition/temperature ranges, which also allows designing the alloys with proper surface protections, such as chromia- or alumina-scale formation on the surface. This leads to proposing and designing new high-temperature structural materials to be used in extreme environments such as Advanced USC or supercritical CO₂ cycle applications. The presentation will also introduce various developmental efforts in Fe-base, Cr-base, and Cu-base alloys with Laves-phase strengthening at ORNL in the last decades. Research supported by the U.S. Department of Energy, Office of Fossil Energy, the Crosscutting Research Program.