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allow the billet to start through the die more
8
easily, as well as to transfer the chilling action
by the ram to a more easily extruded material.
The miid steel is cropped from the tube blank
after extrusion. Steel washed back on the outside
.
surface of the tube is machined off before the tube
blank is reduced to tubing.
Improved lubrication of the billet was obtained
by coating the container of the press, as well as
the mandrel, with Necrolene grease prior to each
extrusion. Low-melting-point Fiberglas mats are
also placed around the hot billets before they are
introduced into the extrusion press. This Iubrication
practice has resulted in lowering the
c pressure required for extrusion of these materials.
.
i
*
LJ
Consumable-Electrode Experiments
As indicated previously,’ arrangements were
made with Battelle Memorial institute for the prepa-
ration of arc-melted ingots of nickel, Hastelloy B,
Hastelloy W, a 76% Ni-1774 Mo-7% Cr alloy, and
an 83% Ni-17% Mo alloy. The melts were to be
made by the consumable-electrode process to take
advantage of the high arc temperatures for vapor-
izing “tramp” etements in an effort to improve
the strength and fabricability of these alloys.
Electrodes of the first three alloys were to be
supplied in the form of rolled rods. The special
nickel-molybdenum alloys were to be prepared
by vacuum melting, and the electrodes were to be
fabricated by threading together extruded rods of
the material. All the electrodes are now ready
for shipment.
2
*Weight gain of lnconel in 168 hr at lSOO°F = 0.00004 g/crn .
PERlOD ENDING JUNE 10, 1956
OXIDATION OF HASTELLOY B
H. lnouye J. E. Spruiel12
It was reported previously3 that the oxidation
rate of Hastelloy B in air at 1500°F was not
excessive, When the alloy was thermally cycled
from 1500°F to below about 66OoF, however, the
rate was increased by an order of magnitude as
a result of spalling of the protective NiMoO, scale
from the metal surface. This spalling is caused
by a phase transformation in the NiMoO, layer at
about 660°F.
The oxidation of Hastelloy 6 in static air has
now been investigated at 1200, 1400, 1600, afld
1800°F. Data were obtained for mechanically
polished specimens exposed to air at the various
temperatures for periods of 168 hr. The increases
in the specimen weights were determined at
frequent i nterva I s to obtain oxi dot i on-rate curves.
The total weight idcreases of the specimens
during the tests at the various temperatures are
shown in Table 3.3.7. The curves of the weight
gain vs time were parabolic at all test temper-
atures, and thus the oxide scale appears to be
protective.
The oxidation rate of the alloy at 1200°F is
very low, and the superficial scale which forms
does not spall upon cooling. Preliminary x-ray
data show that this scale is principally NiO.
Thus far in these studies‘ of the oxidation
characteristics of nickel-molybdenum alloys, evi-
dence has been found that the formation of NiMoO,
depends upon the molybdenum content. However,
its formation may also be a function of temper-
ature, as indicated in the tests described above.
Rarnorks
Oxide did not spall on cooling
Oxide spalled on cooling
Oxide spalled on cooling
Oxide spalled on cooling
167