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

Journal Article · Thu Jul 30 00:00:00 EDT 2015 · Corrosion

DOI:https://doi.org/10.5006/1657· OSTI ID:1273151

Zheng, Guiqiu ^[1]; Kelleher, Brian ^[1]; He, Lingfeng ^[2]; Cao, Guoping ^[1]; Anderson, Mark ^[1]; Allen, Todd ^[2]; Sridharan, Kumar ^[1]

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1. Univ. of Wisconsin, Madison, WI (United States)
2. Idaho National Lab. (INL), Idaho Falls, ID (United States)

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.

• Research Organization: Idaho National Lab. (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC07-05ID14517
• OSTI ID: 1273151
• Journal Information: Corrosion, Vol. 71, Issue 10; ISSN 0010-9312
• Publisher: NACE International
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
hastelloy N
molten salt
FLiBe
corrosion
nuclear reactor