Molten halide salts are being considered as working fluids for nuclear and concentrated solar power applications.  High temperature (>600°C) molten fluoride and chloride salts are known to preferentially attack and deplete chromium in alloys.  This leads to the use of high-nickel lower-chromium alloys in test facilities for advanced molten salt technology.  Alloy 600 (UNS N06600) and C-276 (UNS N10276) are two commercially available nickel alloys that have moderate chromium contents and are qualified to the maximum temperature of 649°C and 677°C, respectively, in ASME BPVC Section VIII and Piping Code B31.3.  Both alloys have good corrosion resistance to acids, are resistant to stress-corrosion cracking, and have long track records of use in the chemical industry.  Comparatively, Alloy C-276 has a similar chromium content but much higher allowed stresses for temperatures greater than 600°C.  Therefore, it has been considered as a structural material for test facilities that require operations at 700°C or greater to develop high-temperature molten salt technology.  To meet the requirements, the current code design values were extended based on some experimental data.  Analysis showed that above current Codified maximum temperature, strength of the alloy is mainly controlled by creep rupture life under the average stress, although the S~c~ creep rate criterion is close to the F~avg~.S~avg~ rupture criterion.  This paper presents the intended test facilities and the design requirements, alloy selection considerations, literature review, data analysis, and proposed allowed stresses extension based on some creep test data for C-276 at temperatures greater than 677°C.\[RKR1\] \[RW2\]   Further research activities are also briefly discussed.


Extension of Alloy C-276 Code Design Values for Advanced Molten Salt Technology Test Facilities

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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