ORNL-1771 - Oak Ridge National Laboratory

Three brazed lnconel specimens were exposed
for 100 hr at 1500°F in \-in.-OD# 0.035-in.-wall
lnconel container tubes to static NaF-ZrF,-UF,
(53.5-40-6.5 mole %), and three were exposed to
static sodium. The brazed specimens were cleaned
carefully before and after testing so that valid
weight-change data could be obtained. The speci-
mens were nickel plated after exposure to prevent
rounding of the edges during metallographic polish-
ing. Presented in Table 6.1 are the data obtained
by metallographic examination of the specimens.
Alloys A and B showed very good resistance to
attack by the fluoride mixture, as shown in Figs.
6.1 and 6.2. Alloy A is also shown in Figs. 6.3
and 6.4 at low magnification in the as-brazed and
as-tested conditions. Alloy C was attacked slightly
by the fluoride mixture. All the alloys were attacked
slightly by sodium, with alloy A showing the least
attack. The maximum depth of attack of 3 to 4 mils
Ni PLATE
PERIOD ENDING SEPTEMBER 10, 7954
on alloy A is not serious, since sodium would be
in contact with this alloy only in the event of a
tube-to-header weld fracture. It may be concluded
from the results of these iests that further study is
warranted on alloys A and B; both showed good re-
sistance to attack by the fluoride mixture. Special
emphasis will be placed on alloy A, since it
exhibited superior resistance to attack by sodium.
Special Stellite Heats in
bdoF-ZrF,-UF, and in Sodium
Two special heats of Stellite, heats B and C,
were requested from the Union Carbide and Carbon
Metals Research Laboratories for corrosion testing.
The specimens were sand cast and had Rockwell
C hardnesses as follows: heat B, 39 to 42; heat C,
42 to 43. The as-received microstructure consisted
of Cr,C, carbide particles in a cobalt-rich matrix.
The approximate compositions of these heats were
0.001
_I_
X
0
2
0.002
3.003
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