ORNL-1816 - the Molten Salt Energy Technologies Web Site

ANP QUARTERLY PROGRESS REPORT
7. METALLURGY AND CERAMICS
W. D. Manly
Metal I urgy
el-molybdenum base alloys are being
studied extensively as possible reactor structural
materials with qualities superior to those of
Inconel. Efforts are under way to evaluate and
improve the existing alloys and to develop better
ones, Radiator test assemblies have been fabri-
cated, and weld stability and mechanical properties
are being studied. Work has continued on the
preparation of duplex tubing, boron carbide shield-
ing, tubular fuel elements, and other special
materials. The results of oxidation resistance
tests of brazing alloys are presented. In addition,
the first production of beryllium oxide ceramics by
casting from a slip which is basic is described.
DEVELOPMENT OF NICKEL-MOLYBDENUM
BASE ALLOYS
The investigations under way for the evaluation
of nickel-molybdenum base alloys as structural
materials for circulating-fuel reactors include
attempts to improve the ductility and the fabrica-
bility of commercially available Hastelloy B through
purification, and efforts to find another suitable
and improved nickel-molybdenum base alloy that
has the strength and corrosion resistance of
Hastelloy B. Fabrication experiments are being
used to determine the effects of various treatments
on the materials developed.
Fabrication Experiments
H. lnouye J. H. Coobs
Meta I I urgy Division
One of the difficulties experienced in the fabri-
cation of Hastelloy B is due to the narrow range
of forgeability of the alloy - between 1950 and
21OOOF. The upper limit of forgeability is due to
impurities which cause gra i n-boundary me1 ti ng .
The low ductility at temperatures between 900 and
180OOF is less understood, but it is believed to be
due to aging and impurity precipitation in grain
boundaries. Therefore efforts are being made
to eliminate trace (tramp) elements by vacuum
elting and the addition of elements to neutralize
One of the most critical components of a circu-
lating-fuel reactor will be the fluoride-to-NaK
J. M. Warde
Division
heat exchanger, for which, because of its com-
plexity and fragility, it will be highly desirable to
have seamless tubing. Commercially available
Hastelloy B tubing, which is now made by welding
strip, is not satisfactory because of cracks in the
weld, checks on the surface, and, in the absence
of severe working of the weld, nonuniform proper-
ties. Therefore several extrusion experiments have
been performed in an effort to produce seamless
tubing.
The initial extrusion experiments were attempts
to produce rod from air melts of Hastelloys B and
C. When extrusion temperatures above 21OO0F
and up to 235OOF were used, the alloys fractured
severely in all instances. For the subsequent
experiments, the extrusion temperature was lowered
to 21OO0F, and a reduction ratio of 6.3:l was
established. The results obtained for the various -
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materials are summarized in the following.
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Vacuum-Melted, As-Cost Hastelloy B. The 6’
ingot that was extruded had been homogeneized
at 21OOOF for 48 hr. The front of the extrusion
fractured severely, but some improvement was
noted in comparison with the air melts previously
extruded.
Air-Melted, As-Cast Hastelloy B PluyO.2% Ti
as Ti-Mn-AI-Ni Master Alloy. The ingot was
homogeneized 48 hr at 2 100°F before extrusion.
The extrusion fractured severely, and no improvement
in comparison with the vacuum melt was
noted.
Air-Melted, Commercial, Wrought Hastelloy B .
The extrusion fractured severely and thus indicated
that the cast structure was not responsible for
the poor hot forgeability of the alloy.
Air-Melted, Commercial, As-Cast Hastelloy C.
The extrusion was made through a cascade die
(cone plus shear) to determine the effect of die
design. Thus far, the alloy has been extruded
through cone dies varying from 45 to 25 deg and
through a shear die. In all extrusions, the rod
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fractured severely. An extrusion was also made 3 ,
by containing the billet in an lnconel can 0.063 - 1
in. thick on the outside diameter and with a %-in.-
thick disk at the nose of the billet. The lnconel
nose separated from the Hastelloy, but the Hastelloy * I
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