Evaluation of Corrosion Behavior of Various Fe- and Ni-Based Alloys in Molten Li₂BeF₄ (FLiBe)

Abstract

Reliable performance of structural alloys is essential for the successful implementation of Generation-IV fluoride salt–cooled high-temperature reactors (FHRs). Most FHR designs are considering molten salt (2LiF-BeF₂), or FLiBe, as a primary coolant or fuel carrier. The main corrosion mechanism for alloys exposed to molten fluoride salts is the selective dealloying of active alloying elements. Alloy composition has a significant effect on their high-temperature mechanical properties, but also affects their corrosion behavior. Although Hastelloy-N and its variants show good corrosion resistance compared to higher Cr-containing Ni- or Fe-based alloys, the mechanical properties of these alloys degrade quickly at temperatures above ~600°C. Twelve Ni-based or Fe-based alloys were selected due to their high temperature stability or their low Cr alloy composition and tested for their corrosion behavior in FLiBe. The results show that the mode and the extent of alloy degradation by selective dissolution mechanism corelates well with the overall alloy composition, and not just the concentration of active elements. It was found that there was good correlation between weight loss of the tested alloys and the ratio of major active elements (Cr, Mn) to that of the more noble alloying elements (Ni, Mo).

Keywords:

• Molten salt
• corrosion
• alloy selection, FLiBe

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Nuclear Energy University Program under award DE-NE0008749. Any opinions, findings, conclusions, or recommendations expressed in this paper are those of the authors and do not necessarily reflect the views of the U.S. Department of Energy (DOE) Office of Nuclear Energy.This paper has been co-authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with DOE. The U.S. government retains and the publisher, by accepting this paper for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this paper, or allow others to do so, for U.S. government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).