Effect of overheating on creep-rupture properties of S-816 alloy at 1,500 degrees F Page: 2 of 76
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TECH LIBRARY KAFB, NM
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS 0066952
TECHNICAL NOTE 4081
EFFECT OF OVERHEATING ON CREEP-RUPTURE PROPERTIES
OF S-816 AIJLOY AT 1,5000 F
By John P. Rowe and J. W. Freeman
An investigation of overheating S-816 alloy to temperatures of
1,6500, 1,8000, 1,9000, and 2,0000 F during the course of rupture tests
at 1,5000 F was carried out. The overheating was applied periodically
for 2 minutes in most of the tests. The intent was to develop basic
information on the effect of overheats on creep-rupture properties in
order to assist in the evaluation of damage from overheats during gas-
Overheating reduces rupture life both through alteration of the
internal structure of the alloy and, if stress is present during an
overheat, by accelerated creep at the higher temperature. Such reduc-
tion in rupture life increases with the temperature and duration of
overheating. Loss in rupture life by structural alteration was negli-
gible at 1,6500 F, but two overheats to 2,0000 F of 2-minute duration
in the absence of stress reduced life at 1,5000 F by about 70 percent.
Apparently, the total damage, if stress is present during overheats, is
the sum of the structural change effect from temperature plus the per-
centage of the total rupture life at the overheat temperature represented
by the time at the overheat temperature under stress.
While the reduction in rupture time at 1,5000 F due to temperature-
induced structural changes can be large, the corresponding reduction in
stress for rupture in a specific time is considerably smaller on a per-
centage basis. From this viewpoint, major reductions in rupture strength
due to overheating arise only when sufficient stress is present during
an overheat to use up substantial amounts of rupture life by accelerated
creep. This indicates that in the absence of substantial creep during
overheating other sources of damage, such as thermal shock, will usually
be the important causes of damage.
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Rowe, John P. & Freeman, J. W. Effect of overheating on creep-rupture properties of S-816 alloy at 1,500 degrees F, report, December 1957; (https://digital.library.unt.edu/ark:/67531/metadc57081/m1/2/: accessed April 19, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.