ORNL-1816 - the Molten Salt Energy Technologies Web Site

AT= 136OOF
OPERATING TIME = 312 hr
MAXIMUM CORROSION
PENETRATION = 0 001 in.
i6O0F
NOTE EQUILIBRIUM LOOP SURFACE TEMPERATURES
ARE GIVEN.
-
0°F
4651
BOILER AND
VAPOR
SEPARATOR
SECTION
30°F
-
1 1 2 3 4 5 1
Fig. 6.12. Sectioned lnconel Loop After Ex-
posure to Boiling or Vaporized Rubidium for
100 hr.
During - the past quarter
this hypothesis has been tested further, and, as in
,.
PERlOD ENDING DECEMBER 70, 1954
The first loops in which the 50% Fe--50% Cr
specimen was tested in liquid lead failed after
46 hr of operation with hot- and cold-leg Vempera-
tures of 805 and 550°C, respectively. The second
loop failed after only 30 hr of o
and cold-leg temperatures of 805 and 5OO0C, re-
spect ivel y. Microscopic examination showed
clearly that a phase transformation took piece in
the test specimens during the operation of the
loops. As shown in Fig, 6.16, a narrow layer of a
second phase formed at the outer surface of the
hot-leg specimens, Hardness measurements yielded
values of 162 and 1140 (DPH hardness scale) for
the new and original phases, respectively. These
values correspond closely to those expected for
ferrite and sigma phases, The possibility that
the new phase was ferritic was supported by the
fact that it was magnetic and by a chemicctl analy-
sis of the plugs formed in the loops. Siince the
plugs were slightly richer in chromium than in
iron, a decrease in the chromium content of the
outer layers of the test specimens was indicated.
The test temperature was close to the sigma-fo-
ferrite transformation point, and therefore even a
slight alteration in the original 50% Fe--50% Cr
composition would produce an alloy in which only
ferrite is stable at the temperature in question.
A second alloy, 50% Mo-50% Fe, was a1 so tested.
This alloy was chosen because an intermetallic
compound predominates at the indicated compo-
sition, Circulation of lead in this loop stopped
after 520 hr with hot- and cold-leg temperatures
of 805 and 5OO0C, respectively. Examination of
this loop has not yet been completed; therefore,
the results obtained will not be discussed other
for loops containing their pure constituents.
'