ORNL-1771 - Oak Ridge National Laboratory

excessive oxidation. A potential source of trouble
exists because of the molybdenum content; molybde-
num oxide has been reported to cause catastrophic
oxidation of surrounding structures, especially the
steels.
The solutions to these problems are being ap-
proached in two major ways. First, attempts are
being made to find suitable melting and heating
treatments of Hastelloy 5 that will reduce the
degree of age hardening so that both the cast and
wrought materials wi I I possess acceptable properties
in the temperature range of interest. Second,
Hastelloy-type alloys are being studied. Both
phases of the investigation will involve attempts to
extrude seamless tubing, since, at present, Hastelloy
B tubing must be made by welding strips. Aging
studies of the following materials are now in ptog-
ress at temperatures between 1200 and 1700°F:
commercial, wrought, Hastelloy 5 plate; vacuum-
melted Hastelloy B, as cast; cast and wrought 20%
M0-80% Ni alloy; wrought 24% Mo-76% Ni alloy,
Some of the properties of the 20% Mo-80% Ni
alloy already obtained indicate that this alloy will
be easier to fabricate than Hastelloy B from an
extrusion standpoint; sound tubing could be made,
whereas none was obtained from Hastelloy B.
The recrystallization temperature of a 6Wo cold-
worked sheet of the 20% Mo-80% Ni alloy was ap-
proximately 1900°F for an annealing time of 30
min. However, this alloy oxidizes in air ai 1500°F
at a faster rate than does Hastelloy 5, although
under a temperature cycle between room temperature
and 1500°F the oxidation rates are similar. The
scale formed spalls near room temperature. A
sheet, 0.065 in. thick, could be heiiarc welded
without producing porosity, but an argon arc pro-
duced porosity. In strength tests at 150O0F, the
20% M0-80% Ni allay had a rupture life of 90 hr at
8000 psi; when tested at SO00 psi for 600 hr, it had
a 3% elongation; during a short-time test the alloy
had a tensile strength of 40,000 psi and an elongation
of 10% in a 2-in. gage length.
Oxidation and oxidation-protection studies are in
progress to find suitable methods of protecting the
nickel-molybdenum-base alloys during tests in ther-
mal-convection loops and creep-testing apparatus.
This work will be the ground work for further studies
of the protection of reactor components. The coat-
ings being studied are those that can be applied by
methods readily available, that is, chromium electro-
plate, chromium plus nickel electroplate, nickel
PERIOD ENDING SEPTEMBER 70, 1954
plus aluminum spray, and aluminum spray. In
constant-temperature tests, a chromium electroplate
was found to be beneficial. In oxidation tests in-
volving cycling between room temperature and
1500"F, these coatings eliminate the spalling
characteristics of Hastelloy B. The chromium elec-
troplate and the chromium plus nickel electroplate
afford the best protection.
Duplex Tubing
Attempts have been made to fabricate duplex
seamless tubing that wi II have good corrosion
resistance on the inner surface and oxidation
resistance on the outer surface. In the first ex-
periments, attempts were made to deep draw duplex
blanks 4 in. in diameter. The blanks were made by
hot pressing and also by hot rolling, The following
materials were combined by hot pressing 0.025-in.-
thick sheets under an argon atmosphere with Al,O,-
coated graphite dies at 1500 psi.
Copper plus type 310 stainless
steel
Inconel plus type 310 stainless
steel
Pressing
Te rnperature
("a
1000
Inconel plus Hastelloy B 1200
Hastelloy B plus type 310 stainless
steel
1200
1200
Copper was also combined with type 310 stainless
steel by hot rolling at 1000°C. Far this, a three-ply
composite with capper in the center and cover plates
of the stainless steel was used. One of the cover
plates was oxidized at 1100°C for 2 hr to prevent
bonding during rolling.
Included in these experiments were some tests
involving the fabrication of composites of molybde-
num and Inconel. The purposes of these tests were
to determine the conditions necessary to obtain a
metallurgical bond by hot rolling, to determine the
extent of directional properties due io the molybde-
num, and to determine whether such a combination
could be deep drawn. The first rolling experiments
were made on an evacuated capsule at 1225OC with
reductions of 10% per pass. The total reduction was
79% in thickness. No bonding was obtained by
using nickel as an intermediate layer between the
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