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STATIC TESTS OF INCONEL CASTINGS
R. Carlander
In thermal-convection loop tests bf lnconel cast-
ings in the fuel mixture (No. 30) NaF-ZrF,-UF,
(50-46-4 mole %), much heavier attack of the cast
material occurred than is normally observed for
wrought lnconel (see Chap. 3.1, "Dynamic Cor-
rosion Studies"). Metallographic examination of
the as-received material showed the presence of
cracks, stringer porosity, and large grains, with
the grain boundaries perpendicular to the surface.
In order to obtain further information on the effect
of the composition of the cast material on its
corrosion resistance, static tests of three lnconel
castings that differed primarily in silicon content
were performed in the fuel mixture (No. 30) NaF-
ZrF,-UF, (50-46-4 mole %) in wrought lnconel
capsules for 1000 hr ut 15OOOF. Examination of
the tested specimens revealed that the casting
with the highest silicon content (1.93%) was the
least attacked, while the casting with the lowest
silicon content was the most severely attacked.
In all cases, the attack was a combination of
subsurface voids and intergranular penetration.
The depth of subsurface voids on the Inconel
castings was 3 to 4 mils, as compared with 2 to
4 mils on the wrought lnconel capsules. The
intergranular penetration, however, varied from
3 mils on the high-silicon-content casting to 12
mils on the low-silicon-content casting. This
PERIOD ENDING JUNE lo, l9S6
difference is attributed to the porosity and to the
grain boundaries running perpendicular to the
surface of the casting. The results of metal-
lographic examinations of the three cast specimens
are presented in Table 3.2.5, and the wrought
lnconel capsule and cast lnconel specimen No. 321
are shown in Fig. 3.2.14. In every case the
wrought lnconel container was more corrosion
resistant than was the cast lnconel specimen.
INCONEL AND STAINLESS STEEL IN NaK
CONTAINING LITHIUM
R. Carlander
Type 316 stainless steel and lnconel were ex-
posed to NaK containing lithium in static and in
dynamic systems in order to determine the effect
of the lithium on corrosion resistance. In the
static tests the specimens were exposed to NaK
(5644 wt %) with lithium additions of 1, 5, 10,
20, and 30 wt % for 100 hr at 1500OF. No attack
occurred in any of the tests.
For the dynamic tests, 12-in.-long capsules
were filled to 40% of their volume with NaK plus
lithium (5 or 10 wt %) and placed in a tilting-
type furnace (1 cpm) at a hot-zone temperature
of 15OOOF (cold zone, 1100'F) for 100 hr. No
mass transfer occurred in any of these systems.
The lnconel exposed to NaK with 10 wt % lithium
added was attacked to a depth of 1 mil in the hot
tone, while the other capsules were unattacked.
TABLE 3.25. RESULTS OF METALLOGRAPHIC EXAMINATION OF CAST INCONEL SPECIMENS AFTER
EXPOSURE TO STATIC NaF-ZrF4-UF4 (50-46-4 mole %) FOR 1000 hr AT lSOO°F
Cast Inconel Slllcon bepth of Attack (mils)
Specimen Content Wrought lnconel Cast lnconel
Metallographic Notes on Cost
cracks apparent
lnconel Specimen
intergranular penetration to depth
of 8 mils; no cracks apparent
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