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National Advisory Committee for Aeronautics, Technical Notes - Influence of Chemical Composition on Rupture Test Propellers at 1500°F of Forged Chromium-Cobalt-Nickel-Iron Base Alloys

The influence of systematic variations of chemical composition on
rupture properties at 15000 F was determined for 62 modifications of a
basic alloy containing 0.15 percent carbon, 1.7 percent manganese,

0.5 percent silicon, 20 percent chromium, 20 percent nickel, 20 percent
cobalt, 3 percent molybdenum, 2 percent tungsten, 1 percent columbium,
0.12 percent nitrogen, and the balance iron. These modifications
included individual variations of each of 10 elements present and
simultaneous variations of molybdenum, tungsten, and columbium. All
specimens were forged to bar stock, solution—treated at 22000 F for

1 hour, and aged at 1’400o F for 2h hours using procedures to minimize
effects of prior history. The rupture strengths for 100 hours and at
least extrapolated values to 1000 hours were obtained. The results of
a similar study at 12000 F were previously reported in NACA Report 1058.

All of the elements can be varied individually between quite wide
limits without significantly changing the rupture properties. This
feature of the results could be partially-responsible for the difficulty
of correlating chemical composition with properties at high temperatures
from data in the literature. There was no evidence to indicate that
composition variation within usual commercial limits contributes materially
to scatter bands in properties.

Carbon could be increased to about 0.h0 percent with little change
in strength although elongation in_the rupture test would be greatly
reduced. Increased silicon would be detrimental to.strength.' The amount
of carbon and manganese must be above minimum values to.avoid low
strength and low elongation, respectively. Alloys with 10 percent of
nickel or cobalt have properties similar to those of the basic alloy.
Reduction of chromium, molybdenum, tungsten, or columbium below the
values in the basic. alloy would be detrimental to strength. Further
increases are of no benefit and in the case of columbium are detrimental.
Alloys containing about 8 percent of molybdenum plus tungsten without
the presence of columbium would be as strong as the basic alloy.