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Slow-strain-rate testing of 2. 25Cr-1Mo in molten-nitrate salt. [450 AND 520/sup 0/C]

Technical Report ·
DOI:https://doi.org/10.2172/6164552· OSTI ID:6164552
The influence of an oxidizing molten-nitrate salt (60% NaNO/sub 3/-40% KNO/sub 3/) on the mechanical properties of 2.25Cr-1Mo has been examined through a series of slow-strain-rate tests at 450/sup 0/C and 525/sup 0/C. By comparing fracture strain, reduction in area, and the ultimate strength of air-exposed specimens to these same parameters for specimens tested in the binary-salt mixture, the susceptibility of the alloy to environmental degradation could be ascertained. Exposure to the nitrate resulted in a loss of ductility as measured by either the engineering fracture strain or reduction in area at both temperatures studied. At these temperatures, the ductility loss was most pronounced at the lowest strain rates (1 x 10/sup -7/ sec/sup -1/). In general, for all strain rates examined, the degree of ductility loss was greater at 525/sup 0/C than at 450/sup 0/C. Metallographic observations revealed that severe surface oxidation occurred as the result of exposure to the molten salt. These surface scales were found to be nonadherent and easily spalled. The rapid formation of these corrosion products and the inability of the material to form a protective barrier against further oxidation is consistent with the ductility loss observed in the salt-exposed specimens. 22 figures.
Research Organization:
Sandia National Labs., Livermore, CA (USA)
DOE Contract Number:
AC04-76DP00789
OSTI ID:
6164552
Report Number(s):
SAND83-8214; ON: DE83011894
Country of Publication:
United States
Language:
English