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for 5 min at 3000 psi at 1150, 1200,
and 1250OC in an argon atmosphere.
Further tests have been run at 1150°C
for 1, 10, and 30 min to determine
the effect of time on the extent of
bonding. Evaluation of these tests
is not complete.
Examination of the first group of
samples revealed little difference in
the degree of bonding at the various
temperatures. As was expected, considerably
more diffusion occurred at
1250'C than at the lower temperatures,
but bonding was only slightly better.
In general, the various couples may
be divided into four groups on the
basis of the extent of bonding: excellent,
interface almost obliterated,
insep ar ab1 e; good, inter face we1 1
de fined, in sep ar ab1 e; fa i r , sep ar a te d
with some di f f i cul ty; poor, only
* superficial bonding. The couples
studied fall into these categories in
the following manner:
Exce 1 Zen t
Nickel to Inconel
Nickel to stainless steel
Stainless steel to stainless steel
Iron to iron
Good
Nickel to iron
Nickel to nickel
Molybdenum to nickel foil to molybdenum
Farr
Molybdenum to nickel
Molybdenum to Inconel
Molybdenum to molybdenum
Poor
Molybdenum to iron
Molybdenum to stainless steel
The self-welding of the molybdenum,
with or without a nickel foil bonding
layer, was poor at 1ZSO'C; so supplementary
runs were made at 1400 and
1500°C, with results as indicated
above.
For molybdenum to nickel and molybdenum
to Inconel, there was a
measurable amount of diffusion but
only fair bonding, possibly because
of the formation of a third phase of
PERIOD ENDING DECEMBER 10, 1952
poor strength at the interface. EX-
tensive diffusion (2 to 3 m i l s )
occurred between molybdenum and iron
and molybdenum and stainless steel,
but there was even less bonding than
was found between molybdenum and
nickel or between molybdenum and
Inconel.
Further work in which electro-
deposited chromium is used as a bonding
layer is being done on the bonding of
molybdenum to the other metals.
Chromium is reported to be completely
miscible with molybdenum and may be
more compatible with the other ma-
terial s.
Several small fuel assemblies have
been prepared by using the electro-
formed nickel screen, filling with
mixtures of UO, and stainless steel
powder, and pressing rubberstatically.
This step is followed by cladding both
sides with iron or nickel sheet and
by hot pressing at 1250°C. The as-
semblies are now being examined for
fuel distribution and bond integrity.
COLUMBIUM RESEARCIl
E. S. Romar H. Inouye
Me tal lurgy Division
Gaseou s Reac t ions. I nve s ti ga ti on
of the reaction of gases with colurnbi-
um was initiated after a literature
survey was made that revealed the
high reactivity oi the metal above
400°C and some preliminary high tem-
perature tests made that gave erratic
results. Minute quantities of dis-
solved gases change the mechanical
properties considerably, and hence
these reactions must be controlled.
The primary interest during this
period was in finding a suitable
atmosphere in which to conduct creep
tests. An argon atmosphere was
selected, initially, and some of the
observations are presented in Table
12.1. Commercial, tank argon was
purified by drying with a tower of
m agne si um perchlorate , fo 1 lowed by
157