ORNL-1771 - Oak Ridge National Laboratory

ANP QUARTERLY PROGRESS REPORT
A plausible explanation has been developed for
the evidence of a maximum in the corrosion of In-
conel by molten fluorides in static tests at 800 to
900°C and for both void formation and chromium
concentration in the melt being less at 1000°C than
at 800°C. Static tests of type 316 stainless steel
in NaZrF, and in NaF-ZrF,-UF, substantiated the
phenomena observed with Inconel.
Additional corrosion experiments with fuel mix-
tures containing simulated fission products have
shown that the experimental procedure being. fol-
lowed is entirely unsatisfactory. A controlled-
velocity corrosion testing apparatus has been con-
structed for the rapid transfer of molten fluoride
niixtures through both heated and cooled test sec-
tions. This apparatus was designed to simulate
conditions in reactor components.
82
STATIC AND SEESAW CORROSION TESTS
E. E. Hoffman
C. R. Brooks
Metallurgy B ivi s ion
W. H. Cook
C. F. Leitten
Brazing Allays in NaF-ZrF,-UF, and in Sodium
Specimens of the three brazing OIIOYS described
in Table 6,1 were tested in NaF-ZrF,-UF, and in
sodium. The specimens were cut from 5-in. T-joints
of Inconel which had been brazed in a dry hydrogen
atmosphere. The purpose of these tests was to
find brazing cslloy with good corrosion resistance
to both NaF-ZrF,-UF, and sodium, since such ci
brazing alloy could be used to back up tube-to-
header welds. In use, the brazing alloy would be
exposed to the fluoride mixture, but resistance to
attack by sodium would also be required if a
fracture occurred in a tube-to-header weld.
TABLE 6.1. RESULTS OF STATIC TESTS OF BWAZRNG ALLOYS IN NaS-ZrF4-UF4
(53.5-40.6.5 mole %) AND IN SODIUM A? 150OoF FOR 100 hr
Brazing Alloy
Composition
Allay A
67 Ni, 13 Ge, 11 Cr, 6 Si, 2 Fe, NaF-ZrF4-UF4
1 Mn on lnconel (brazed at
1 120°C for 10 min)
Alloy 8
65 Ni, 25 Ge, 10 Cr on lncanel
(brazed at 1 14OoC for 10 mi")
Sodium
We ig ht We ig ht
Both Change Change Metallographic Notes
No F- Zr F4-UF4
Sodium
Alloy C
72 Ni, 18 Ge, 7 Cr, 3 p on Na F- ZrF4-UFq
lnconel
Sodium
+0.0003 +0.024
-0.0003 - 0.0 17
-0.0010 -0.077
-0.0013 -0.1 16
-0.0005 -5.041
-0.0008 -0.058
Very little attack; slight surface
roughening to a depth of 0.25
mil
Attack in the form of subsurface
voids to a maximum depth of 3
to 4 mils
No attack; slight uniform solu-
tion would occount for weight
loss
Braze fillet attacked to a maxi-
mum depth of 8 mils
Braze fillet attacked to a depth
of 2 to 3 mils in the form of
subsurface voids
Braze fillet ottocked to a depth
of 3 to 6 mils in the form of
subsurface voids