ORNL-1771 - Oak Ridge National Laboratory

ANP QUARTERLY PROGRESS REPORT
TABLE 6.4. CARFSURIZATION OF INCONEL BY
EXPOSURE TO SODIUM CONTAINING CARBON
ADDITIONS FOR 100 hr AT lMO0F
Carbon content of lnconel specirnen before test, 0.056 wt %
Carbon Added Carbon Content*
to Sodium of Specimen
Before Test
Afrer Test
Specimen
Weight Change**
(% 1
(wt 76) (wt %) . . . . . . . . . . . . . .
1 0.882 1.09
5 1.09 1.34
io 1.24 1.63
*Average of three analyses.
**On all specimens part of weight change was due to
formation of G203 film on surface.
compared with the 0 to 2 mils attack by NaF-ZrF,-
UF, (50-46-4 mole %) in the previous tests.' The
carbon content of the fluoride mixture did not change
significantly in either test.
A comparison of the carburization of nustenitic
stuinless steel by tar-impregnated and fired graphite
and by C-18 graphite (reactor grade) was obtained
through static tests of cylinders of the same size
of each type of graphite in type 304 stainless steel
tubes containing equal quantities of sodium in
vacuum. Tests for 100. and SOO-hr periods at
1500°C were made on each type of graphite. Type
3114 stainless steel was chosen because it carbur-
izes more readily than other austenitic stainless
steels.
The results of the tests are shown in Figs. 6.12
and 6.13. In the 100-hr test, the tar-impregnated
and fired graphite curburized the type 304 stainless
steel to a slightly greater extent than the C-18
graphite did, and in the 500-hr test, it clearly car-
burized the steel to a greater extent. After the
500-hr tests of both types of graphite, steel in ron-
tact with the sodium showed small subsurface
voids; the voids were pronounced in the steel tested
with the tar-impregnated and fired graphite. The
depth of Carburization of the type 304 stainless
steel above the level of the molten sodium covering
the graphite cylinders was 1 mil in all the tests,
except the 500-hr test with u tar-impregnated and
fired graphite cylinder in which there was carbu-
rization of the steel to a depth of 2 mils.
92
Vf '[DENT
Y - 12453 'IAL
Y - I 2416
0 INCH f
Fig. 6.11. Graph-i-tite Crucible Before (u) and
Aftes (6) Exposure to HoF-ErF4-UF, (53.5-40-6.5
mole %) for 108 hr at 150t)OF. At the end of the
test the crucible was inverted so that the fluoride
mixture would flow to the top. The frozen fluoride
mixture can be seen above the shiny inner surface
of the crucible,