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Title: High-temperature corrosion of UNS N10003 in molten Li2BeF4 (FLiBe) salt

Here, corrosion testing of Hastelloy N in molten fluoride salt was performed in purified molten 27LiF-BeF2 (66-34mol%) (FLiBe) salt at 700°C for 1000 hours, in pure nickel and graphite capsules. In the nickel capsule tests, the near-surface region of the alloy exhibited an about 200 nm porous structure, an approximately 3.5 μm chromium depleted region, and MoSi2 precipitates. In tests performed in graphite capsules, the alloy samples gained weight due to the formation of a variety of Cr3C2, Cr7C3, Mo2C and Cr23C6, carbide phases on the surface and in the subsurface regions of the alloy. A Cr depleted region was observed in the near-surface region where Mo thermally diffused toward either surface or grain boundary, which induced approximately 1.4 μm Ni3Fe alloy layer in this region. The carbide containing layer extended to about 7 μm underneath the Ni3Fe layer. The presence of graphite dramatically changes the mechanisms of corrosion attack in Hastelloy N in molten FLiBe salt. Evaluated by in terms of the depth of attack, graphite clearly accelerates corrosion, but the results appear to indicate that the formation of Cr23C6 phase might stabilize the Cr and mitigate its dissolution in molten FLiBe salt.
 [1] ;  [1] ;  [2] ;  [1] ;  [1] ;  [2] ;  [1]
  1. Univ. of Wisconsin, Madison, WI (United States)
  2. Idaho National Lab. (INL), Idaho Falls, ID (United States)
Publication Date:
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Additional Journal Information:
Journal Volume: 71; Journal Issue: 10; Journal ID: ISSN 0010-9312
NACE International
Research Org:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
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Country of Publication:
United States
36 MATERIALS SCIENCE; hastelloy N; molten salt; FLiBe; corrosion; nuclear reactor